[{"Question":"I've written a Python package that includes a bsddb database of pre-computed values for one of the more time-consuming computations.  For simplicity, my setup script installs the database file in the same directory as the code which accesses the database (on Unix, something like \/usr\/lib\/python2.5\/site-packages\/mypackage\/).\nHow do I store the final location of the database file so my code can access it?  Right now, I'm using a hack based on the __file__ variable in the module which accesses the database:\n\ndbname = os.path.join(os.path.dirname(__file__), \"database.dat\")\n\nIt works, but it seems... hackish.  Is there a better way to do this?  I'd like to have the setup script just grab the final installation location from the distutils module and stuff it into a \"dbconfig.py\" file that gets installed alongside the code that accesses the database.","AnswerCount":4,"Available Count":2,"Score":1.0,"is_accepted":false,"ViewCount":28993,"Q_Id":39104,"Users Score":19,"Answer":"Use pkgutil.get_data. It\u2019s the cousin of pkg_resources.resource_stream, but in the standard library, and should work with flat filesystem installs as well as zipped packages and other importers.","Q_Score":32,"Tags":"python,distutils","A_Id":9918496,"CreationDate":"2008-09-02T09:40:00.000","Title":"Finding a file in a Python module distribution","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I've written a Python package that includes a bsddb database of pre-computed values for one of the more time-consuming computations.  For simplicity, my setup script installs the database file in the same directory as the code which accesses the database (on Unix, something like \/usr\/lib\/python2.5\/site-packages\/mypackage\/).\nHow do I store the final location of the database file so my code can access it?  Right now, I'm using a hack based on the __file__ variable in the module which accesses the database:\n\ndbname = os.path.join(os.path.dirname(__file__), \"database.dat\")\n\nIt works, but it seems... hackish.  Is there a better way to do this?  I'd like to have the setup script just grab the final installation location from the distutils module and stuff it into a \"dbconfig.py\" file that gets installed alongside the code that accesses the database.","AnswerCount":4,"Available Count":2,"Score":0.1488850336,"is_accepted":false,"ViewCount":28993,"Q_Id":39104,"Users Score":3,"Answer":"That's probably the way to do it, without resorting to something more advanced like using setuptools to install the files where they belong.\nNotice there's a problem with that approach, because on OSes with real a security framework (UNIXes, etc.) the user running your script might not have the rights to access the DB in the system directory where it gets installed.","Q_Score":32,"Tags":"python,distutils","A_Id":39295,"CreationDate":"2008-09-02T09:40:00.000","Title":"Finding a file in a Python module distribution","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"All the docs for SQLAlchemy give INSERT and UPDATE examples using the local table instance (e.g. tablename.update()... )\nDoing this seems difficult with the declarative syntax, I need to reference Base.metadata.tables[\"tablename\"] to get the table reference.\nAm I supposed to do this another way?   Is there a different syntax for INSERT and UPDATE recommended when using the declarative syntax?  Should I just switch to the old way?","AnswerCount":3,"Available Count":2,"Score":0.2605204458,"is_accepted":false,"ViewCount":2919,"Q_Id":75829,"Users Score":4,"Answer":"via the __table__ attribute on your declarative class","Q_Score":8,"Tags":"python,sql,sqlalchemy","A_Id":77962,"CreationDate":"2008-09-16T19:08:00.000","Title":"Best way to access table instances when using SQLAlchemy's declarative syntax","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"All the docs for SQLAlchemy give INSERT and UPDATE examples using the local table instance (e.g. tablename.update()... )\nDoing this seems difficult with the declarative syntax, I need to reference Base.metadata.tables[\"tablename\"] to get the table reference.\nAm I supposed to do this another way?   Is there a different syntax for INSERT and UPDATE recommended when using the declarative syntax?  Should I just switch to the old way?","AnswerCount":3,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":2919,"Q_Id":75829,"Users Score":0,"Answer":"There may be some confusion between table (the object) and tablename (the name of the table, a string). Using the table class attribute works fine for me.","Q_Score":8,"Tags":"python,sql,sqlalchemy","A_Id":315406,"CreationDate":"2008-09-16T19:08:00.000","Title":"Best way to access table instances when using SQLAlchemy's declarative syntax","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm writing a server that I expect to be run by many different people, not all of whom I will have direct contact with. The servers will communicate with each other in a cluster. Part of the server's functionality involves selecting a small subset of rows from a potentially very large table. The exact choice of what rows are selected will need some tuning, and it's important that it's possible for the person running the cluster (eg, myself) to update the selection criteria without getting each and every server administrator to deploy a new version of the server.\nSimply writing the function in Python isn't really an option, since nobody is going to want to install a server that downloads and executes arbitrary Python code at runtime.\nWhat I need are suggestions on the simplest way to implement a Domain Specific Language to achieve this goal. The language needs to be capable of simple expression evaluation, as well as querying table indexes and iterating through the returned rows. Ease of writing and reading the language is secondary to ease of implementing it. I'd also prefer not to have to write an entire query optimiser, so something that explicitly specifies what indexes to query would be ideal.\nThe interface that this will have to compile against will be similar in capabilities to what the App Engine datastore exports: You can query for sequential ranges on any index on the table (eg, less-than, greater-than, range and equality queries), then filter the returned row by any boolean expression. You can also concatenate multiple independent result sets together.\nI realise this question sounds a lot like I'm asking for SQL. However, I don't want to require that the datastore backing this data be a relational database, and I don't want the overhead of trying to reimplement SQL myself. I'm also dealing with only a single table with a known schema. Finally, no joins will be required. Something much simpler would be far preferable.\nEdit: Expanded description to clear up some misconceptions.","AnswerCount":9,"Available Count":6,"Score":0.022218565,"is_accepted":false,"ViewCount":2773,"Q_Id":140026,"Users Score":1,"Answer":"\"implement a Domain Specific Language\"\n\"nobody is going to want to install a server that downloads and executes arbitrary Python code at runtime\"\nI want a DSL but I don't want Python to be that DSL.  Okay.  How will you execute this DSL?  What runtime is acceptable if not Python?\nWhat if I have a C program that happens to embed the Python interpreter?  Is that acceptable?\nAnd -- if Python is not an acceptable runtime -- why does this have a Python tag?","Q_Score":5,"Tags":"python,database,algorithm,dsl","A_Id":141872,"CreationDate":"2008-09-26T14:56:00.000","Title":"Writing a Domain Specific Language for selecting rows from a table","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm writing a server that I expect to be run by many different people, not all of whom I will have direct contact with. The servers will communicate with each other in a cluster. Part of the server's functionality involves selecting a small subset of rows from a potentially very large table. The exact choice of what rows are selected will need some tuning, and it's important that it's possible for the person running the cluster (eg, myself) to update the selection criteria without getting each and every server administrator to deploy a new version of the server.\nSimply writing the function in Python isn't really an option, since nobody is going to want to install a server that downloads and executes arbitrary Python code at runtime.\nWhat I need are suggestions on the simplest way to implement a Domain Specific Language to achieve this goal. The language needs to be capable of simple expression evaluation, as well as querying table indexes and iterating through the returned rows. Ease of writing and reading the language is secondary to ease of implementing it. I'd also prefer not to have to write an entire query optimiser, so something that explicitly specifies what indexes to query would be ideal.\nThe interface that this will have to compile against will be similar in capabilities to what the App Engine datastore exports: You can query for sequential ranges on any index on the table (eg, less-than, greater-than, range and equality queries), then filter the returned row by any boolean expression. You can also concatenate multiple independent result sets together.\nI realise this question sounds a lot like I'm asking for SQL. However, I don't want to require that the datastore backing this data be a relational database, and I don't want the overhead of trying to reimplement SQL myself. I'm also dealing with only a single table with a known schema. Finally, no joins will be required. Something much simpler would be far preferable.\nEdit: Expanded description to clear up some misconceptions.","AnswerCount":9,"Available Count":6,"Score":0.0,"is_accepted":false,"ViewCount":2773,"Q_Id":140026,"Users Score":0,"Answer":"Why not create a language that when it \"compiles\" it generates SQL or whatever query language your datastore requires ?\nYou would be basically creating an abstraction over your persistence layer.","Q_Score":5,"Tags":"python,database,algorithm,dsl","A_Id":140066,"CreationDate":"2008-09-26T14:56:00.000","Title":"Writing a Domain Specific Language for selecting rows from a table","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm writing a server that I expect to be run by many different people, not all of whom I will have direct contact with. The servers will communicate with each other in a cluster. Part of the server's functionality involves selecting a small subset of rows from a potentially very large table. The exact choice of what rows are selected will need some tuning, and it's important that it's possible for the person running the cluster (eg, myself) to update the selection criteria without getting each and every server administrator to deploy a new version of the server.\nSimply writing the function in Python isn't really an option, since nobody is going to want to install a server that downloads and executes arbitrary Python code at runtime.\nWhat I need are suggestions on the simplest way to implement a Domain Specific Language to achieve this goal. The language needs to be capable of simple expression evaluation, as well as querying table indexes and iterating through the returned rows. Ease of writing and reading the language is secondary to ease of implementing it. I'd also prefer not to have to write an entire query optimiser, so something that explicitly specifies what indexes to query would be ideal.\nThe interface that this will have to compile against will be similar in capabilities to what the App Engine datastore exports: You can query for sequential ranges on any index on the table (eg, less-than, greater-than, range and equality queries), then filter the returned row by any boolean expression. You can also concatenate multiple independent result sets together.\nI realise this question sounds a lot like I'm asking for SQL. However, I don't want to require that the datastore backing this data be a relational database, and I don't want the overhead of trying to reimplement SQL myself. I'm also dealing with only a single table with a known schema. Finally, no joins will be required. Something much simpler would be far preferable.\nEdit: Expanded description to clear up some misconceptions.","AnswerCount":9,"Available Count":6,"Score":0.0,"is_accepted":false,"ViewCount":2773,"Q_Id":140026,"Users Score":0,"Answer":"It really sounds like SQL, but perhaps it's worth to try using SQLite if you want to keep it simple?","Q_Score":5,"Tags":"python,database,algorithm,dsl","A_Id":140304,"CreationDate":"2008-09-26T14:56:00.000","Title":"Writing a Domain Specific Language for selecting rows from a table","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm writing a server that I expect to be run by many different people, not all of whom I will have direct contact with. The servers will communicate with each other in a cluster. Part of the server's functionality involves selecting a small subset of rows from a potentially very large table. The exact choice of what rows are selected will need some tuning, and it's important that it's possible for the person running the cluster (eg, myself) to update the selection criteria without getting each and every server administrator to deploy a new version of the server.\nSimply writing the function in Python isn't really an option, since nobody is going to want to install a server that downloads and executes arbitrary Python code at runtime.\nWhat I need are suggestions on the simplest way to implement a Domain Specific Language to achieve this goal. The language needs to be capable of simple expression evaluation, as well as querying table indexes and iterating through the returned rows. Ease of writing and reading the language is secondary to ease of implementing it. I'd also prefer not to have to write an entire query optimiser, so something that explicitly specifies what indexes to query would be ideal.\nThe interface that this will have to compile against will be similar in capabilities to what the App Engine datastore exports: You can query for sequential ranges on any index on the table (eg, less-than, greater-than, range and equality queries), then filter the returned row by any boolean expression. You can also concatenate multiple independent result sets together.\nI realise this question sounds a lot like I'm asking for SQL. However, I don't want to require that the datastore backing this data be a relational database, and I don't want the overhead of trying to reimplement SQL myself. I'm also dealing with only a single table with a known schema. Finally, no joins will be required. Something much simpler would be far preferable.\nEdit: Expanded description to clear up some misconceptions.","AnswerCount":9,"Available Count":6,"Score":0.0,"is_accepted":false,"ViewCount":2773,"Q_Id":140026,"Users Score":0,"Answer":"You mentioned Python. Why not use Python? If someone can \"type in\" an expression in your DSL, they can type in Python.\nYou'll need some rules on structure of the expression, but that's a lot easier than implementing something new.","Q_Score":5,"Tags":"python,database,algorithm,dsl","A_Id":140091,"CreationDate":"2008-09-26T14:56:00.000","Title":"Writing a Domain Specific Language for selecting rows from a table","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm writing a server that I expect to be run by many different people, not all of whom I will have direct contact with. The servers will communicate with each other in a cluster. Part of the server's functionality involves selecting a small subset of rows from a potentially very large table. The exact choice of what rows are selected will need some tuning, and it's important that it's possible for the person running the cluster (eg, myself) to update the selection criteria without getting each and every server administrator to deploy a new version of the server.\nSimply writing the function in Python isn't really an option, since nobody is going to want to install a server that downloads and executes arbitrary Python code at runtime.\nWhat I need are suggestions on the simplest way to implement a Domain Specific Language to achieve this goal. The language needs to be capable of simple expression evaluation, as well as querying table indexes and iterating through the returned rows. Ease of writing and reading the language is secondary to ease of implementing it. I'd also prefer not to have to write an entire query optimiser, so something that explicitly specifies what indexes to query would be ideal.\nThe interface that this will have to compile against will be similar in capabilities to what the App Engine datastore exports: You can query for sequential ranges on any index on the table (eg, less-than, greater-than, range and equality queries), then filter the returned row by any boolean expression. You can also concatenate multiple independent result sets together.\nI realise this question sounds a lot like I'm asking for SQL. However, I don't want to require that the datastore backing this data be a relational database, and I don't want the overhead of trying to reimplement SQL myself. I'm also dealing with only a single table with a known schema. Finally, no joins will be required. Something much simpler would be far preferable.\nEdit: Expanded description to clear up some misconceptions.","AnswerCount":9,"Available Count":6,"Score":0.0,"is_accepted":false,"ViewCount":2773,"Q_Id":140026,"Users Score":0,"Answer":"You said nobody is going to want to install a server that downloads and executes arbitrary code at runtime.  However, that is exactly what your DSL will do (eventually) so there probably isn't that much of a difference.  Unless you're doing something very specific with the data then I don't think a DSL will buy you that much and it will frustrate the users who are already versed in SQL.  Don't underestimate the size of the task you'll be taking on.\nTo answer your question however, you will need to come up with a grammar for your language, something to parse the text and walk the tree, emitting code or calling an API that you've written (which is why my comment that you're still going to have to ship some code).  \nThere are plenty of educational texts on grammars for mathematical expressions you can refer to on the net, that's fairly straight forward.  You may have a parser generator tool like ANTLR or Yacc you can use to help you generate the parser (or use a language like Lisp\/Scheme and marry the two up).  Coming up with a reasonable SQL grammar won't be easy.  But google 'BNF SQL' and see what you come up with.\nBest of luck.","Q_Score":5,"Tags":"python,database,algorithm,dsl","A_Id":140228,"CreationDate":"2008-09-26T14:56:00.000","Title":"Writing a Domain Specific Language for selecting rows from a table","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm writing a server that I expect to be run by many different people, not all of whom I will have direct contact with. The servers will communicate with each other in a cluster. Part of the server's functionality involves selecting a small subset of rows from a potentially very large table. The exact choice of what rows are selected will need some tuning, and it's important that it's possible for the person running the cluster (eg, myself) to update the selection criteria without getting each and every server administrator to deploy a new version of the server.\nSimply writing the function in Python isn't really an option, since nobody is going to want to install a server that downloads and executes arbitrary Python code at runtime.\nWhat I need are suggestions on the simplest way to implement a Domain Specific Language to achieve this goal. The language needs to be capable of simple expression evaluation, as well as querying table indexes and iterating through the returned rows. Ease of writing and reading the language is secondary to ease of implementing it. I'd also prefer not to have to write an entire query optimiser, so something that explicitly specifies what indexes to query would be ideal.\nThe interface that this will have to compile against will be similar in capabilities to what the App Engine datastore exports: You can query for sequential ranges on any index on the table (eg, less-than, greater-than, range and equality queries), then filter the returned row by any boolean expression. You can also concatenate multiple independent result sets together.\nI realise this question sounds a lot like I'm asking for SQL. However, I don't want to require that the datastore backing this data be a relational database, and I don't want the overhead of trying to reimplement SQL myself. I'm also dealing with only a single table with a known schema. Finally, no joins will be required. Something much simpler would be far preferable.\nEdit: Expanded description to clear up some misconceptions.","AnswerCount":9,"Available Count":6,"Score":0.022218565,"is_accepted":false,"ViewCount":2773,"Q_Id":140026,"Users Score":1,"Answer":"I think we're going to need a bit more information here.  Let me know if any of the following is based on incorrect assumptions.\nFirst of all, as you pointed out yourself, there already exists a DSL for selecting rows from arbitrary tables-- it is called \"SQL\".  Since you don't want to reinvent SQL, I'm assuming that you only need to query from a single table with a fixed format.\nIf this is the case, you probably don't need to implement a DSL (although that's certainly one way to go); it may be easier, if you are used to Object Orientation, to create a Filter object.  \nMore specifically, a \"Filter\" collection that would hold one or more SelectionCriterion objects.  You can implement these to inherit from one or more base classes representing types of selections (Range, LessThan, ExactMatch, Like, etc.) Once these base classes are in place, you can create column-specific inherited versions which are appropriate to that column.  Finally, depending on the complexity of the queries you want to support, you'll want to implement some kind of connective glue to handle AND and OR and NOT linkages between the various criteria.\nIf you feel like it, you can create a simple GUI to load up the collection; I'd look at the filtering in Excel as a model, if you don't have anything else in mind.\nFinally, it should be trivial to convert the contents of this Collection to the corresponding SQL, and pass that to the database.\nHowever: if what you are after is simplicity, and your users understand SQL, you could simply ask them to type in the contents of a WHERE clause, and programmatically build up the rest of the query.  From a security perspective, if your code has control over the columns selected and the FROM clause, and your database permissions are set properly, and you do some sanity checking on the string coming in from the users, this would be a relatively safe option.","Q_Score":5,"Tags":"python,database,algorithm,dsl","A_Id":140275,"CreationDate":"2008-09-26T14:56:00.000","Title":"Writing a Domain Specific Language for selecting rows from a table","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I've seen a number of postgresql modules for python like pygresql, pypgsql, psyco. Most of them are Python DB API 2.0 compliant, some are not being actively developed anymore.\nWhich module do you recommend? Why?","AnswerCount":6,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":15582,"Q_Id":144448,"Users Score":0,"Answer":"I uses only psycopg2 and had no problems with that.","Q_Score":28,"Tags":"python,postgresql,module","A_Id":1579851,"CreationDate":"2008-09-27T20:55:00.000","Title":"Python PostgreSQL modules. Which is best?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I've seen a number of postgresql modules for python like pygresql, pypgsql, psyco. Most of them are Python DB API 2.0 compliant, some are not being actively developed anymore.\nWhich module do you recommend? Why?","AnswerCount":6,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":15582,"Q_Id":144448,"Users Score":0,"Answer":"Psycopg1 is known for better performance in heavilyy threaded environments (like web applications) than Psycopg2, although not maintained. Both are well written and rock solid, I'd choose one of these two depending on use case.","Q_Score":28,"Tags":"python,postgresql,module","A_Id":145801,"CreationDate":"2008-09-27T20:55:00.000","Title":"Python PostgreSQL modules. Which is best?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm trying to develop an app using turbogears and sqlalchemy.\nThere is already an existing app using kinterbasdb directly under mod_wsgi on the same server.\nWhen both apps are used, neither seems to recognize that kinterbasdb is already initialized\nIs there something non-obvious I am missing about using sqlalchemy and kinterbasdb in separate apps?  In order to make sure only one instance of kinterbasdb gets initialized and both apps use that instance, does anyone have suggestions?","AnswerCount":1,"Available Count":1,"Score":0.3799489623,"is_accepted":false,"ViewCount":270,"Q_Id":155029,"Users Score":2,"Answer":"I thought I posted my solution already...\nModifying both apps to run under WSGIApplicationGroup ${GLOBAL} in their httpd conf file\nand patching sqlalchemy.databases.firebird.py to check if self.dbapi.initialized is True\nbefore calling self.dbapi.init(... was the only way I could manage to get this scenario up and running.\nThe SQLAlchemy 0.4.7 patch:\n\ndiff -Naur SQLAlchemy-0.4.7\/lib\/sqlalchemy\/databases\/firebird.py SQLAlchemy-0.4.7.new\/lib\/sqlalchemy\/databases\/firebird.py\n--- SQLAlchemy-0.4.7\/lib\/sqlalchemy\/databases\/firebird.py       2008-07-26 12:43:52.000000000 -0400\n+++ SQLAlchemy-0.4.7.new\/lib\/sqlalchemy\/databases\/firebird.py   2008-10-01 10:51:22.000000000 -0400\n@@ -291,7 +291,8 @@\n         global _initialized_kb\n         if not _initialized_kb and self.dbapi is not None:\n             _initialized_kb = True\n-            self.dbapi.init(type_conv=type_conv, concurrency_level=concurrency_level)\n+            if not self.dbapi.initialized:\n+                self.dbapi.init(type_conv=type_conv, concurrency_level=concurrency_level)\n         return ([], opts)\n\n     def create_execution_context(self, *args, **kwargs):","Q_Score":1,"Tags":"python,sqlalchemy,kinterbasdb","A_Id":175634,"CreationDate":"2008-09-30T20:47:00.000","Title":"SQLAlchemy and kinterbasdb in separate apps under mod_wsgi","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":1,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a table that looks something like this:\n\nword        big   expensive   smart   fast\n\ndog         9     -10         -20     4\nprofessor   2     4           40      -7\nferrari     7     50          0       48\nalaska      10    0           1       0\ngnat        -3    0           0       0\n\nThe + and - values are associated with the word, so professor is smart and dog is not smart.  Alaska is big, as a proportion of the total value associated with its entries, and the opposite is true of gnat.\nIs there a good way to get the absolute value of the number farthest from zero, and some token whether absolute value =\/= value?  Relatedly, how might I calculate whether the results for a given value are proportionately large with respect to the other values?  I would write something to format the output to the effect of: \"dog: not smart, probably not expensive; professor smart; ferrari: fast, expensive; alaska: big; gnat: probably small.\" (The formatting is not a question, just an illustration, I am stuck on the underlying queries.)  \nAlso, the rest of the program is python, so if there is any python solution with normal dbapi modules or a more abstract module, any help appreciated.","AnswerCount":5,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":4588,"Q_Id":177284,"Users Score":0,"Answer":"Can you use the built-in database aggregate functions like MAX(column)?","Q_Score":1,"Tags":"python,mysql,sql,oracle,postgresql","A_Id":177302,"CreationDate":"2008-10-07T05:06:00.000","Title":"SQL Absolute value across columns","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Sometimes in our production environment occurs situation when connection between service (which is python program that uses MySQLdb) and mysql server is flacky, some packages are lost, some black magic happens and .execute() of MySQLdb.Cursor object never ends (or take great amount of time to end). \nThis is very bad because it is waste of service worker threads. Sometimes it leads to exhausting of workers pool and service stops responding at all.\nSo the question is: Is there a way to interrupt MySQLdb.Connection.execute operation after given amount of time?","AnswerCount":2,"Available Count":2,"Score":0.1973753202,"is_accepted":false,"ViewCount":2995,"Q_Id":196217,"Users Score":2,"Answer":"if the communication is such a problem, consider writing a 'proxy' that receives your SQL commands over the flaky connection and relays them to the MySQL server on a reliable channel (maybe running on the same box as the MySQL server).  This way you have total control over failure detection and retrying.","Q_Score":2,"Tags":"python,mysql,timeout","A_Id":196308,"CreationDate":"2008-10-12T22:27:00.000","Title":"MySQLdb execute timeout","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Sometimes in our production environment occurs situation when connection between service (which is python program that uses MySQLdb) and mysql server is flacky, some packages are lost, some black magic happens and .execute() of MySQLdb.Cursor object never ends (or take great amount of time to end). \nThis is very bad because it is waste of service worker threads. Sometimes it leads to exhausting of workers pool and service stops responding at all.\nSo the question is: Is there a way to interrupt MySQLdb.Connection.execute operation after given amount of time?","AnswerCount":2,"Available Count":2,"Score":0.0996679946,"is_accepted":false,"ViewCount":2995,"Q_Id":196217,"Users Score":1,"Answer":"You need to analyse exactly what the problem is. MySQL connections should eventually timeout if the server is gone; TCP keepalives are generally enabled. You may be able to tune the OS-level TCP timeouts.\nIf the database is \"flaky\", then you definitely need to investigate how. It seems unlikely that the database really is the problem, more likely that networking in between is.\nIf you are using (some) stateful firewalls of any kind, it's possible that they're losing some of the state, thus causing otherwise good long-lived connections to go dead.\nYou might want to consider changing the idle timeout parameter in MySQL; otherwise, a long-lived, unused connection may go \"stale\", where the server and client both think it's still alive, but some stateful network element in between has \"forgotten\" about the TCP connection. An application trying to use such a \"stale\" connection will have a long wait before receiving an error (but it should eventually).","Q_Score":2,"Tags":"python,mysql,timeout","A_Id":196891,"CreationDate":"2008-10-12T22:27:00.000","Title":"MySQLdb execute timeout","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Any gotchas I should be aware of?  Can I store it in a text field, or do I need to use a blob?\n(I'm not overly familiar with either pickle or sqlite, so I wanted to make sure I'm barking up the right tree with some of my high-level design ideas.)","AnswerCount":14,"Available Count":6,"Score":0.0285636566,"is_accepted":false,"ViewCount":31019,"Q_Id":198692,"Users Score":2,"Answer":"Since Pickle can dump your object graph to a string it should be possible. \nBe aware though that TEXT fields in SQLite uses database encoding so you might need to convert it to a simple string before you un-pickle.","Q_Score":40,"Tags":"python,sqlite,pickle","A_Id":198763,"CreationDate":"2008-10-13T19:11:00.000","Title":"Can I pickle a python dictionary into a sqlite3 text field?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"Any gotchas I should be aware of?  Can I store it in a text field, or do I need to use a blob?\n(I'm not overly familiar with either pickle or sqlite, so I wanted to make sure I'm barking up the right tree with some of my high-level design ideas.)","AnswerCount":14,"Available Count":6,"Score":0.0713073417,"is_accepted":false,"ViewCount":31019,"Q_Id":198692,"Users Score":5,"Answer":"Pickle has both text and binary output formats. If you use the text-based format you can store it in a TEXT field, but it'll have to be a BLOB if you use the (more efficient) binary format.","Q_Score":40,"Tags":"python,sqlite,pickle","A_Id":198767,"CreationDate":"2008-10-13T19:11:00.000","Title":"Can I pickle a python dictionary into a sqlite3 text field?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"Any gotchas I should be aware of?  Can I store it in a text field, or do I need to use a blob?\n(I'm not overly familiar with either pickle or sqlite, so I wanted to make sure I'm barking up the right tree with some of my high-level design ideas.)","AnswerCount":14,"Available Count":6,"Score":0.0285636566,"is_accepted":false,"ViewCount":31019,"Q_Id":198692,"Users Score":2,"Answer":"If a dictionary can be pickled, it can be stored in text\/blob field as well.\nJust be aware of the dictionaries that can't be pickled (aka that contain unpickable objects).","Q_Score":40,"Tags":"python,sqlite,pickle","A_Id":198770,"CreationDate":"2008-10-13T19:11:00.000","Title":"Can I pickle a python dictionary into a sqlite3 text field?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"Any gotchas I should be aware of?  Can I store it in a text field, or do I need to use a blob?\n(I'm not overly familiar with either pickle or sqlite, so I wanted to make sure I'm barking up the right tree with some of my high-level design ideas.)","AnswerCount":14,"Available Count":6,"Score":0.0285636566,"is_accepted":false,"ViewCount":31019,"Q_Id":198692,"Users Score":2,"Answer":"Yes, you can store a pickled object in a TEXT or BLOB field in an SQLite3 database, as others have explained.\nJust be aware that some object cannot be pickled.  The built-in container types can (dict, set, list, tuple, etc.).  But some objects, such as file handles, refer to state that is external to their own data structures, and other extension types have similar problems.\nSince a dictionary can contain arbitrary nested data structures, it might not be pickle-able.","Q_Score":40,"Tags":"python,sqlite,pickle","A_Id":198829,"CreationDate":"2008-10-13T19:11:00.000","Title":"Can I pickle a python dictionary into a sqlite3 text field?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"Any gotchas I should be aware of?  Can I store it in a text field, or do I need to use a blob?\n(I'm not overly familiar with either pickle or sqlite, so I wanted to make sure I'm barking up the right tree with some of my high-level design ideas.)","AnswerCount":14,"Available Count":6,"Score":0.0142847425,"is_accepted":false,"ViewCount":31019,"Q_Id":198692,"Users Score":1,"Answer":"SpoonMeiser is correct, you need to have a strong reason to pickle into a database.  \nIt's not difficult to write Python objects that implement persistence with SQLite.  Then you can use the SQLite CLI to fiddle with the data as well.  Which in my experience is worth the extra bit of work, since many debug and admin functions can be simply performed from the CLI rather than writing specific Python code.\nIn the early stages of a project, I did what you propose and ended up re-writing with a Python class for each business object (note: I didn't say for each table!) This way the body of the application can focus on \"what\" needs to be done rather than \"how\" it is done.","Q_Score":40,"Tags":"python,sqlite,pickle","A_Id":199190,"CreationDate":"2008-10-13T19:11:00.000","Title":"Can I pickle a python dictionary into a sqlite3 text field?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"Any gotchas I should be aware of?  Can I store it in a text field, or do I need to use a blob?\n(I'm not overly familiar with either pickle or sqlite, so I wanted to make sure I'm barking up the right tree with some of my high-level design ideas.)","AnswerCount":14,"Available Count":6,"Score":1.2,"is_accepted":true,"ViewCount":31019,"Q_Id":198692,"Users Score":23,"Answer":"If you want to store a pickled object, you'll need to use a blob, since it is binary data. However, you can, say, base64 encode the pickled object to get a string that can be stored in a text field.\nGenerally, though, doing this sort of thing is indicative of bad design, since you're storing opaque data you lose the ability to use SQL to do any useful manipulation on that data. Although without knowing what you're actually doing, I can't really make a moral call on it.","Q_Score":40,"Tags":"python,sqlite,pickle","A_Id":198748,"CreationDate":"2008-10-13T19:11:00.000","Title":"Can I pickle a python dictionary into a sqlite3 text field?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"For a website like reddit with lots of up\/down votes and lots of comments per topic what should I go with?\nLighttpd\/Php or Lighttpd\/CherryPy\/Genshi\/SQLAlchemy?\nand for database what would scale better \/ be fastest MySQL ( 4.1 or 5 ? ) or PostgreSQL?","AnswerCount":5,"Available Count":4,"Score":0.0798297691,"is_accepted":false,"ViewCount":1670,"Q_Id":204802,"Users Score":2,"Answer":"I would go with nginx + php + xcache + postgresql","Q_Score":7,"Tags":"php,python,lighttpd,cherrypy,high-load","A_Id":244836,"CreationDate":"2008-10-15T13:57:00.000","Title":"What would you recommend for a high traffic ajax intensive website?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"For a website like reddit with lots of up\/down votes and lots of comments per topic what should I go with?\nLighttpd\/Php or Lighttpd\/CherryPy\/Genshi\/SQLAlchemy?\nand for database what would scale better \/ be fastest MySQL ( 4.1 or 5 ? ) or PostgreSQL?","AnswerCount":5,"Available Count":4,"Score":0.0798297691,"is_accepted":false,"ViewCount":1670,"Q_Id":204802,"Users Score":2,"Answer":"Going to need more data.  Jeff had a few articles on the same problems and the answer was to wait till you hit a performance issue.\nto start with - who is hosting and what do they have available ?  what's your in house talent skill sets ?  Are you going to be hiring an outside firm ? what do they recommend ?  brand new project w\/ a team willing to learn a new framework ?\n2nd thing is to do some mockups - how is the interface going to work.  what data does it need to load and persist ? the idea is to keep your traffic between the web and db side down. e.g. no chatty pages with lots of queries. etc.\nOnce you have a better idea of the data requirements and flow - then work on the database design.  there are plenty of rules to follow but one of the better ones is to follow normalization rules (yea i'm a db guy why ?)\nNow you have a couple of pages build - run your tests. are you having a problem ? Yes, now look at what is it. Page serving or db pulls ?  Measure then pick a course of action.","Q_Score":7,"Tags":"php,python,lighttpd,cherrypy,high-load","A_Id":204854,"CreationDate":"2008-10-15T13:57:00.000","Title":"What would you recommend for a high traffic ajax intensive website?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"For a website like reddit with lots of up\/down votes and lots of comments per topic what should I go with?\nLighttpd\/Php or Lighttpd\/CherryPy\/Genshi\/SQLAlchemy?\nand for database what would scale better \/ be fastest MySQL ( 4.1 or 5 ? ) or PostgreSQL?","AnswerCount":5,"Available Count":4,"Score":1.2,"is_accepted":true,"ViewCount":1670,"Q_Id":204802,"Users Score":8,"Answer":"I can't speak to the MySQL\/PostgreSQL question as I have limited experience with Postgres, but my Masters research project was about high-performance websites with CherryPy, and I don't think you'll be disappointed if you use CherryPy for your site.  It can easily scale to thousands of simultaneous users on commodity hardware.\nOf course, the same could be said for PHP, and I don't know of any reasonable benchmarks comparing PHP and CherryPy performance.  But if you were wondering whether CherryPy can handle a high-traffic site with a huge number of requests per second, the answer is definitely yes.","Q_Score":7,"Tags":"php,python,lighttpd,cherrypy,high-load","A_Id":204853,"CreationDate":"2008-10-15T13:57:00.000","Title":"What would you recommend for a high traffic ajax intensive website?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"For a website like reddit with lots of up\/down votes and lots of comments per topic what should I go with?\nLighttpd\/Php or Lighttpd\/CherryPy\/Genshi\/SQLAlchemy?\nand for database what would scale better \/ be fastest MySQL ( 4.1 or 5 ? ) or PostgreSQL?","AnswerCount":5,"Available Count":4,"Score":0.1194272985,"is_accepted":false,"ViewCount":1670,"Q_Id":204802,"Users Score":3,"Answer":"On the DB question, I'd say PostgreSQL scales better and has better data integrity than MySQL. For a small site MySQL might be faster, but from what I've heard it slows significantly as the size of the database grows. (Note: I've never used MySQL for a large database, so you should probably get a second opinion about its scalability.) But PostgreSQL definitely scales well, and would be a good choice for a high traffic site.","Q_Score":7,"Tags":"php,python,lighttpd,cherrypy,high-load","A_Id":205425,"CreationDate":"2008-10-15T13:57:00.000","Title":"What would you recommend for a high traffic ajax intensive website?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have created a Python module that creates and populates several SQLite tables. Now, I want to use it in a program but I don't really know how to call it properly. All the tutorials I've found are essentially \"inline\", i.e. they walk through using SQLite in a linear fashion rather than how to actually use it in production.\nWhat I'm trying to do is have a method check to see if the database is already created. If so, then I can use it. If not, an exception is raised and the program will create the database. (Or use if\/else statements, whichever is better).\nI created a test script to see if my logic is correct but it's not working. When I create the try statement, it just creates a new database rather than checking if one already exists. The next time I run the script, I get an error that the table already exists, even if I tried catching the exception. (I haven't used try\/except before but figured this is a good time to learn).\nAre there any good tutorials for using SQLite operationally or any suggestions on how to code this? I've looked through the pysqlite tutorial and others I found but they don't address this.","AnswerCount":8,"Available Count":5,"Score":0.0,"is_accepted":false,"ViewCount":31269,"Q_Id":211501,"Users Score":0,"Answer":"Yes, I was nuking out the problem. All I needed to do was check for the file and catch the IOError if it didn't exist.\nThanks for all the other answers. They may come in handy in the future.","Q_Score":13,"Tags":"python,exception,sqlite","A_Id":214623,"CreationDate":"2008-10-17T09:02:00.000","Title":"Using SQLite in a Python program","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have created a Python module that creates and populates several SQLite tables. Now, I want to use it in a program but I don't really know how to call it properly. All the tutorials I've found are essentially \"inline\", i.e. they walk through using SQLite in a linear fashion rather than how to actually use it in production.\nWhat I'm trying to do is have a method check to see if the database is already created. If so, then I can use it. If not, an exception is raised and the program will create the database. (Or use if\/else statements, whichever is better).\nI created a test script to see if my logic is correct but it's not working. When I create the try statement, it just creates a new database rather than checking if one already exists. The next time I run the script, I get an error that the table already exists, even if I tried catching the exception. (I haven't used try\/except before but figured this is a good time to learn).\nAre there any good tutorials for using SQLite operationally or any suggestions on how to code this? I've looked through the pysqlite tutorial and others I found but they don't address this.","AnswerCount":8,"Available Count":5,"Score":0.0748596907,"is_accepted":false,"ViewCount":31269,"Q_Id":211501,"Users Score":3,"Answer":"Doing SQL in overall is horrible in any language I've picked up. SQLalchemy has shown to be easiest from them to use because actual query and committing with it is so clean and absent from troubles.\nHere's some basic steps on actually using sqlalchemy in your app, better details can be found from the documentation.\n\nprovide table definitions and create ORM-mappings\nload database\nask it to create tables from the definitions (won't do so if they exist)\ncreate session maker (optional)\ncreate session\n\nAfter creating a session, you can commit and query from the database.","Q_Score":13,"Tags":"python,exception,sqlite","A_Id":211539,"CreationDate":"2008-10-17T09:02:00.000","Title":"Using SQLite in a Python program","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have created a Python module that creates and populates several SQLite tables. Now, I want to use it in a program but I don't really know how to call it properly. All the tutorials I've found are essentially \"inline\", i.e. they walk through using SQLite in a linear fashion rather than how to actually use it in production.\nWhat I'm trying to do is have a method check to see if the database is already created. If so, then I can use it. If not, an exception is raised and the program will create the database. (Or use if\/else statements, whichever is better).\nI created a test script to see if my logic is correct but it's not working. When I create the try statement, it just creates a new database rather than checking if one already exists. The next time I run the script, I get an error that the table already exists, even if I tried catching the exception. (I haven't used try\/except before but figured this is a good time to learn).\nAre there any good tutorials for using SQLite operationally or any suggestions on how to code this? I've looked through the pysqlite tutorial and others I found but they don't address this.","AnswerCount":8,"Available Count":5,"Score":1.0,"is_accepted":false,"ViewCount":31269,"Q_Id":211501,"Users Score":7,"Answer":"SQLite automatically creates the database file the first time you try to use it. The SQL statements for creating tables can use IF NOT EXISTS to make the commands only take effect if the table has not been created This way you don't need to check for the database's existence beforehand: SQLite can take care of that for you.\nThe main thing I would still be worried about is that executing CREATE TABLE IF EXISTS for every web transaction (say) would be inefficient; you can avoid that by having the program keep an (in-memory) variable saying whether it has created the database today, so it runs the CREATE TABLE script once per run. This would still allow for you to delete the database and start over during debugging.","Q_Score":13,"Tags":"python,exception,sqlite","A_Id":211573,"CreationDate":"2008-10-17T09:02:00.000","Title":"Using SQLite in a Python program","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have created a Python module that creates and populates several SQLite tables. Now, I want to use it in a program but I don't really know how to call it properly. All the tutorials I've found are essentially \"inline\", i.e. they walk through using SQLite in a linear fashion rather than how to actually use it in production.\nWhat I'm trying to do is have a method check to see if the database is already created. If so, then I can use it. If not, an exception is raised and the program will create the database. (Or use if\/else statements, whichever is better).\nI created a test script to see if my logic is correct but it's not working. When I create the try statement, it just creates a new database rather than checking if one already exists. The next time I run the script, I get an error that the table already exists, even if I tried catching the exception. (I haven't used try\/except before but figured this is a good time to learn).\nAre there any good tutorials for using SQLite operationally or any suggestions on how to code this? I've looked through the pysqlite tutorial and others I found but they don't address this.","AnswerCount":8,"Available Count":5,"Score":1.0,"is_accepted":false,"ViewCount":31269,"Q_Id":211501,"Users Score":29,"Answer":"Don't make this more complex than it needs to be.  The big, independent databases have complex setup and configuration requirements.  SQLite is just a file you access with SQL, it's much simpler.\nDo the following.\n\nAdd a table to your database for \"Components\" or \"Versions\" or \"Configuration\" or \"Release\" or something administrative like that.  \nCREATE TABLE REVISION(\n    RELEASE_NUMBER CHAR(20)\n);\nIn your application, connect to your database normally.\nExecute a simple query against the revision table.  Here's what can happen.\n\n\nThe query fails to execute: your database doesn't exist, so execute a series of CREATE statements to build it.\nThe query succeeds but returns no rows or the release number is lower than expected: your database exists, but is out of date.  You need to migrate from that release to the current release.  Hopefully, you have a sequence of DROP, CREATE and ALTER statements to do this.\nThe query succeeds, and the release number is the expected value.  Do nothing more, your database is configured correctly.","Q_Score":13,"Tags":"python,exception,sqlite","A_Id":211660,"CreationDate":"2008-10-17T09:02:00.000","Title":"Using SQLite in a Python program","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have created a Python module that creates and populates several SQLite tables. Now, I want to use it in a program but I don't really know how to call it properly. All the tutorials I've found are essentially \"inline\", i.e. they walk through using SQLite in a linear fashion rather than how to actually use it in production.\nWhat I'm trying to do is have a method check to see if the database is already created. If so, then I can use it. If not, an exception is raised and the program will create the database. (Or use if\/else statements, whichever is better).\nI created a test script to see if my logic is correct but it's not working. When I create the try statement, it just creates a new database rather than checking if one already exists. The next time I run the script, I get an error that the table already exists, even if I tried catching the exception. (I haven't used try\/except before but figured this is a good time to learn).\nAre there any good tutorials for using SQLite operationally or any suggestions on how to code this? I've looked through the pysqlite tutorial and others I found but they don't address this.","AnswerCount":8,"Available Count":5,"Score":1.2,"is_accepted":true,"ViewCount":31269,"Q_Id":211501,"Users Score":13,"Answer":"AFAIK an SQLITE database is just a file.\nTo check if the database exists, check for file existence.\nWhen you open a SQLITE database it will automatically create one if the file that backs it up is not in place.\nIf you try and open a file as a sqlite3 database that is NOT a database, you will get this:\n\"sqlite3.DatabaseError: file is encrypted or is not a database\"\nso check to see if the file exists and also make sure to try and catch the exception in case the file is not a sqlite3 database","Q_Score":13,"Tags":"python,exception,sqlite","A_Id":211534,"CreationDate":"2008-10-17T09:02:00.000","Title":"Using SQLite in a Python program","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"From what I understand, the parent attribute of a db.Model (typically defined\/passed in the constructor call) allows you to define hierarchies in your data models. As a result, this increases the size of the entity group. However, it's not very clear to me why we would want to do that. Is this strictly for ACID compliance? I would like to see scenarios where each is best suited or more appropriate.","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1067,"Q_Id":215570,"Users Score":15,"Answer":"There are several differences:\n\nAll entities with the same ancestor are in the same entity group. Transactions can only affect entities inside a single entity group.\nAll writes to a single entity group are serialized, so throughput is limited.\nThe parent entity is set on creation and is fixed. References can be changed at any time.\nWith reference properties, you can only query for direct relationships, but with parent properties you can use the .ancestor() filter to find everything (directly or indirectly) descended from a given ancestor.\nEach entity has only a single parent, but can have multiple reference properties.","Q_Score":10,"Tags":"python,api,google-app-engine","A_Id":216187,"CreationDate":"2008-10-18T21:12:00.000","Title":"What's the difference between a parent and a reference property in Google App Engine?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I need to update data to a mssql 2005 database so I have decided to use adodbapi, which is supposed to come built into the standard installation of python 2.1.1 and greater.\nIt needs pywin32 to work correctly and the open office python 2.3 installation does not have pywin32 built into it. It also seems like this built int python installation does not have adodbapi, as I get an error when I go import adodbapi. \nAny suggestions on how to get both pywin32 and adodbapi installed into this open office 2.4 python installation?\nthanks \n\noh yeah I tried those ways. annoyingly nothing. So i have reverted to jython, that way I can access Open Office for its conversion capabilities along with decent database access.\nThanks for the help.","AnswerCount":3,"Available Count":1,"Score":0.0665680765,"is_accepted":false,"ViewCount":833,"Q_Id":239009,"Users Score":1,"Answer":"maybe the best way to install pywin32 is to place it in \n(openofficedir)\\program\\python-core-2.3.4\\lib\\site-packages\nit is easy  if you have a python 2.3 installation (with pywin installed) under \nC:\\python2.3 \nmove the C:\\python2.3\\Lib\\site-packages\\ to your\n(openofficedir)\\program\\python-core-2.3.4\\lib\\site-packages","Q_Score":0,"Tags":"python,openoffice.org,pywin32,adodbapi","A_Id":239487,"CreationDate":"2008-10-27T03:32:00.000","Title":"getting pywin32 to work inside open office 2.4 built in python 2.3 interpreter","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"With SQLAlchemy, is there a way to know beforehand whether a relation would be lazy-loaded?\nFor example, given a lazy parent->children relation and an instance X of \"parent\", I'd like to know if \"X.children\" is already loaded, without triggering the query.","AnswerCount":3,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":3701,"Q_Id":258775,"Users Score":5,"Answer":"I think you could look at the child's __dict__ attribute dictionary to check if the data is already there or not.","Q_Score":16,"Tags":"python,sqlalchemy","A_Id":261191,"CreationDate":"2008-11-03T14:28:00.000","Title":"How to find out if a lazy relation isn't loaded yet, with SQLAlchemy?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I want to make my Python library working with MySQLdb be able to detect deadlocks and try again.  I believe I've coded a good solution, and now I want to test it.\nAny ideas for the simplest queries I could run using MySQLdb to create a deadlock condition would be?\nsystem info:\n\nMySQL 5.0.19 \nClient 5.1.11 \nWindows XP\nPython 2.4 \/ MySQLdb 1.2.1 p2","AnswerCount":5,"Available Count":1,"Score":0.0399786803,"is_accepted":false,"ViewCount":7080,"Q_Id":269676,"Users Score":1,"Answer":"you can always run LOCK TABLE tablename from another session (mysql CLI for instance). That might do the trick.\nIt will remain locked until you release it or disconnect the session.","Q_Score":10,"Tags":"python,mysql,database,deadlock","A_Id":270449,"CreationDate":"2008-11-06T18:06:00.000","Title":"How can I Cause a Deadlock in MySQL for Testing Purposes","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm starting a web project that likely should be fine with SQLite.  I have SQLObject on top of it, but thinking long term here -- if this project should require a more robust (e.g. able to handle high traffic), I will need to have a transition plan ready.  My questions:\n\nHow easy is it to transition from one DB (SQLite) to another (MySQL or Firebird or PostGre) under SQLObject?  \nDoes SQLObject provide any tools to make such a transition easier?  Is it simply take the objects I've defined and call createTable?  \nWhat about having multiple SQLite databases instead?  E.g. one per visitor group?  Does SQLObject provide a mechanism for handling this scenario and if so, what is the mechanism to use?\n\nThanks,\nSean","AnswerCount":3,"Available Count":1,"Score":0.1325487884,"is_accepted":false,"ViewCount":876,"Q_Id":275572,"Users Score":2,"Answer":"Your success with createTable() will depend on your existing underlying table schema \/ data types.  In other words, how well SQLite maps to the database you choose and how SQLObject decides to use your data types.\nThe safest option may be to create the new database by hand.  Then you'll have to deal with data migration, which may be as easy as instantiating two SQLObject database connections over the same table definitions.\nWhy not just start with the more full-featured database?","Q_Score":1,"Tags":"python,mysql,database,sqlite,sqlobject","A_Id":275676,"CreationDate":"2008-11-09T03:46:00.000","Title":"Database change underneath SQLObject","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am having a postgres production database in production (which contains a lot of Data). now I need to modify the model of the tg-app to add couple of new tables to the database. \nHow do i do this? I am using sqlAlchemy.","AnswerCount":4,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":889,"Q_Id":301566,"Users Score":1,"Answer":"This always works and requires little thinking -- only patience.\n\nMake a backup.\nActually make a backup.  Everyone skips step 1 thinking that they have a backup, but they can never find it or work with it.  Don't trust any backup that you can't recover from.\nCreate a new database schema.\nDefine your new structure from the ground up in the new schema.  Ideally, you'll run a DDL script that builds the new schema.  Don't have a script to build the schema?  Create one and put it under version control.\nWith SA, you can define your tables and it can build your schema for you.  This is ideal, since you have your schema under version control in Python.\nMove data.\na. For tables which did not change structure, move data from old schema to new schema using simple INSERT\/SELECT statements.\nb. For tables which did change structure, develop INSERT\/SELECT scripts to move the data from old to new.  Often, this can be a single SQL statement per new table.  In some cases, it has to be a Python loop with two open connections.\nc. For new tables, load the data.\nStop using the old schema.  Start using the new schema.  Find every program that used the old schema and fix the configuration.  \nDon't have a list of applications?  Make one.  Seriously -- it's important.  \nApplications have hard-coded DB configurations?  Fix that, too, while you're at it.  Either create a common config file, or use some common environment variable or something to (a) assure consistency and (b) centralize the notion of \"production\".\n\nYou can do this kind of procedure any time you do major surgery.  It never touches the old database except to extract the data.","Q_Score":1,"Tags":"python,database,postgresql,data-migration,turbogears","A_Id":301708,"CreationDate":"2008-11-19T11:00:00.000","Title":"How to update turbogears application production database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm using Django and Python 2.6, and I want to grow my application using a MySQL backend.  Problem is that there isn't a win32 package for MySQLdb on Python 2.6.\nNow I'm no hacker, but I thought I might compile it myself using MSVC++9 Express.  But I run into a problem that the compiler quickly can't find config_win.h, which I assume is a header file for MySQL so that the MySQLdb package can know what calls it can make into MySQL.\nAm I right?  And if so, where do I get the header files for MySQL?","AnswerCount":4,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":3446,"Q_Id":316484,"Users Score":2,"Answer":"I think that the header files are shipped with MySQL, just make sure you check the appropriate options when installing (I think that sources and headers are under \"developer components\" in the installation dialog).","Q_Score":9,"Tags":"python,mysql,winapi","A_Id":317716,"CreationDate":"2008-11-25T06:14:00.000","Title":"Problem compiling MySQLdb for Python 2.6 on Win32","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"What is the sqlalchemy equivalent column type for 'money' and 'OID' column types in Postgres?","AnswerCount":3,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":10565,"Q_Id":359409,"Users Score":3,"Answer":"we've never had an \"OID\" type specifically, though we've supported the concept of an implicit \"OID\" column on every table through the 0.4 series, primarily for the benefit of postgres.  However since user-table defined OID columns are deprecated in Postgres, and we in fact never really used the OID feature that was present, we've removed this feature from the library.\nIf a particular type is not supplied in SQLA, as an alternative to specifying a custom type, you can always use the NullType which just means SQLA doesn't know anything in particular about that type.  If psycopg2 sends\/receives a useful Python type for the column already, there's not really any need for a SQLA type object, save for issuing CREATE TABLE statements.","Q_Score":8,"Tags":"python,postgresql,sqlalchemy","A_Id":405923,"CreationDate":"2008-12-11T13:52:00.000","Title":"What is the sqlalchemy equivalent column type for 'money' and 'OID' in Postgres?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"How do I connect to a MySQL database using a python program?","AnswerCount":25,"Available Count":1,"Score":0.0079998293,"is_accepted":false,"ViewCount":1369727,"Q_Id":372885,"Users Score":1,"Answer":"First step to get The Library:\nOpen terminal and execute pip install mysql-python-connector.\nAfter the installation go the second step.\nSecond Step to import the library:\nOpen your python file and write the following code:\nimport mysql.connector\nThird step to connect to the server:\nWrite the following code:\n\nconn = mysql.connector.connect(host=you host name like  localhost or 127.0.0.1,\nusername=your  username like root,\npassword = your  password)\n\nThird step Making the cursor:\nMaking a cursor makes it easy for us to run queries.\nTo make the cursor use the following code:\ncursor = conn.cursor()\nExecuting queries:\nFor executing queries you can do the following:\ncursor.execute(query)\nIf the query changes any thing in the table you need to add the following code after the execution of the query:\nconn.commit()\nGetting values from a query:\nIf you want to get values from a query then you can do the following:\ncursor.excecute('SELECT * FROM table_name') for i in cursor: print(i) #Or for i in cursor.fetchall(): print(i)\nThe fetchall() method returns a list with many tuples that contain the values that you requested ,row after row .\nClosing the connection:\nTo close the connection you should use the following code:\nconn.close()\nHandling exception:\nTo Handel exception you can do it Vai the following method:\ntry: #Logic pass except mysql.connector.errors.Error: #Logic  pass\nTo use a database:\nFor example you are a account creating system where you are storing the data in a database named blabla, you can just add a database parameter to the connect() method ,like\nmysql.connector.connect(database = database name)\ndon't remove other informations like host,username,password.","Q_Score":1242,"Tags":"python,mysql","A_Id":64762149,"CreationDate":"2008-12-16T21:49:00.000","Title":"How do I connect to a MySQL Database in Python?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"So, looking for a mysql-db-lib that is compatible with py3k\/py3.0\/py3000, any ideas? Google turned up nothing.","AnswerCount":9,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":43916,"Q_Id":384471,"Users Score":0,"Answer":"You're probably better off using Python 2.x at the moment. It's going to be a while before all Python packages are ported to 3.x, and I expect writing a library or application with 3.x at the moment would be quite frustrating.","Q_Score":36,"Tags":"python,mysql,python-3.x","A_Id":385225,"CreationDate":"2008-12-21T13:37:00.000","Title":"MySQL-db lib for Python 3.x?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I need to design a program using python that will ask the user for a barcode. Then, using this barcode, it will search a mysql to find its corresponding product. \nI am a bit stuck on how to get started. Does anyone have any tips for me?","AnswerCount":4,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":4847,"Q_Id":387606,"Users Score":0,"Answer":"To start with, treat the barcode input as plain old text.   \nIt has been quite a while since I worked with barcode scanners, but I doubt they have changed that much, the older ones used to just piggyback on the keyboard input, so from a programming perspective, the net result was a stream of characters in the keyboard buffer, either typed or scanned made no difference. \nIf the device you are targeting differs from that, you will need to write something to deal with that before you get to the database query.   \nIf you have one of the devices to play with, plug it in, start notepad, start scanning some barcodes and see what happens.","Q_Score":1,"Tags":"python,sql,user-input","A_Id":387800,"CreationDate":"2008-12-22T22:37:00.000","Title":"Using user input to find information in a Mysql database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I need to design a program using python that will ask the user for a barcode. Then, using this barcode, it will search a mysql to find its corresponding product. \nI am a bit stuck on how to get started. Does anyone have any tips for me?","AnswerCount":4,"Available Count":3,"Score":0.049958375,"is_accepted":false,"ViewCount":4847,"Q_Id":387606,"Users Score":1,"Answer":"A barcode is simply a graphical representation of a series of characters (alphanumeric)\nSo if you have a method for users to enter this code (a barcode scanner), then its just an issue of querying the mysql database for the character string.","Q_Score":1,"Tags":"python,sql,user-input","A_Id":387622,"CreationDate":"2008-12-22T22:37:00.000","Title":"Using user input to find information in a Mysql database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I need to design a program using python that will ask the user for a barcode. Then, using this barcode, it will search a mysql to find its corresponding product. \nI am a bit stuck on how to get started. Does anyone have any tips for me?","AnswerCount":4,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":4847,"Q_Id":387606,"Users Score":0,"Answer":"That is a very ambiguous question. What you want can be done in many ways depending on what you actually want to do.\nHow are your users going to enter the bar code? Are they going to use a bar code scanner? Are they entering the bar code numbers manually? \nIs this going to run on a desktop\/laptop computer or is it going to run on a handheld device? \nIs the bar code scanner storing the bar codes for later retrieval or is it sending them directly to the computer. Will it send them through a USB cable or wireless?","Q_Score":1,"Tags":"python,sql,user-input","A_Id":387694,"CreationDate":"2008-12-22T22:37:00.000","Title":"Using user input to find information in a Mysql database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm writing a script in python which basically queries WMI and updates the information in a mysql database.  One of those \"write something you need\" to learn to program exercises.\nIn case something breaks in the middle of the script, for example, the remote computer turns off, it's separated out into functions.\nQuery Some WMI data\nUpdate that to the database\nQuery Other WMI data\nUpdate that to the database  \nIs it better to open one mysql connection at the beginning and leave it open or close the connection after each update?\nIt seems as though one connection would use less resources. (Although I'm just learning, so this is a complete guess.)  However, opening and closing the connection with each update seems more 'neat'. Functions would be more stand alone, rather than depend on code outside that function.","AnswerCount":4,"Available Count":3,"Score":1.2,"is_accepted":true,"ViewCount":1201,"Q_Id":387619,"Users Score":7,"Answer":"\"However, opening and closing the connection with each update seems more 'neat'. \" \nIt's also a huge amount of overhead -- and there's no actual benefit.\nCreating and disposing of connections is relatively expensive.  More importantly, what's the actual reason?  How does it improve, simplify, clarify?\nGenerally, most applications have one connection that they use from when they start to when they stop.","Q_Score":2,"Tags":"python,mysql","A_Id":387932,"CreationDate":"2008-12-22T22:40:00.000","Title":"Mysql Connection, one or many?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm writing a script in python which basically queries WMI and updates the information in a mysql database.  One of those \"write something you need\" to learn to program exercises.\nIn case something breaks in the middle of the script, for example, the remote computer turns off, it's separated out into functions.\nQuery Some WMI data\nUpdate that to the database\nQuery Other WMI data\nUpdate that to the database  \nIs it better to open one mysql connection at the beginning and leave it open or close the connection after each update?\nIt seems as though one connection would use less resources. (Although I'm just learning, so this is a complete guess.)  However, opening and closing the connection with each update seems more 'neat'. Functions would be more stand alone, rather than depend on code outside that function.","AnswerCount":4,"Available Count":3,"Score":0.0996679946,"is_accepted":false,"ViewCount":1201,"Q_Id":387619,"Users Score":2,"Answer":"I don't think that there is \"better\" solution. Its too early to think about resources. And since wmi is quite slow ( in comparison to sql connection ) the db is not an issue.\nJust make it work. And then make it better.\nThe good thing about working with open connection here, is that the \"natural\" solution is to use objects and not just functions. So it will be a learning experience( In case you are learning python and not mysql).","Q_Score":2,"Tags":"python,mysql","A_Id":387735,"CreationDate":"2008-12-22T22:40:00.000","Title":"Mysql Connection, one or many?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm writing a script in python which basically queries WMI and updates the information in a mysql database.  One of those \"write something you need\" to learn to program exercises.\nIn case something breaks in the middle of the script, for example, the remote computer turns off, it's separated out into functions.\nQuery Some WMI data\nUpdate that to the database\nQuery Other WMI data\nUpdate that to the database  \nIs it better to open one mysql connection at the beginning and leave it open or close the connection after each update?\nIt seems as though one connection would use less resources. (Although I'm just learning, so this is a complete guess.)  However, opening and closing the connection with each update seems more 'neat'. Functions would be more stand alone, rather than depend on code outside that function.","AnswerCount":4,"Available Count":3,"Score":0.049958375,"is_accepted":false,"ViewCount":1201,"Q_Id":387619,"Users Score":1,"Answer":"Useful clues in S.Lott's and Igal Serban's answers. I think you should first find out your actual requirements and code accordingly.\nJust to mention a different strategy; some applications keep a pool of database (or whatever) connections and in case of a transaction just pull one from that pool. It seems rather obvious you just need one connection for this kind of application. But you can still keep a pool of one connection and apply following;\n\nWhenever database transaction is needed the connection is pulled from the pool and returned back at the end.\n(optional) The connection is expired (and of replaced by a new one) after a certain amount of time.\n(optional) The connection is expired after a certain amount of usage.\n(optional) The pool can check (by sending an inexpensive query) if the connection is alive before handing it over the program.\n\nThis is somewhat in between single connection and connection per transaction strategies.","Q_Score":2,"Tags":"python,mysql","A_Id":389364,"CreationDate":"2008-12-22T22:40:00.000","Title":"Mysql Connection, one or many?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am using python to read a currency value from excel. The returned from the range.Value method is a tuple that I don't know how to parse.\nFor example, the cell appears as $548,982, but in python the value is returned as (1, 1194857614).\nHow can I get the numerical amount from excel or how can I convert this tuple value into the numerical value?\nThanks!","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":586,"Q_Id":390263,"Users Score":0,"Answer":"I tried this with Excel 2007 and VBA. It is giving correct value.\n1) Try pasting this value in a new excel workbook\n2) Press Alt + F11. Gets you to VBA Editor.\n3) Press Ctrl + G. Gets you to immediate window.\n4) In the immediate window, type  ?cells(\"a1\").Value \nhere \"a1\" is the cell where you have pasted the value.\nI am doubting that the cell has some value or character due to which it is interpreted this way.\nPost your observations here.","Q_Score":1,"Tags":"python,excel,pywin32","A_Id":390304,"CreationDate":"2008-12-23T22:37:00.000","Title":"Interpreting Excel Currency Values","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am currently analyzing a wikipedia dump file; I am extracting a bunch of data from it using python and persisting it into a PostgreSQL db. I am always trying to make things go faster for this file is huge (18GB). In order to interface with PostgreSQL, I am using psycopg2, but this module seems to mimic many other such DBAPIs.\nAnyway, I have a question concerning cursor.executemany(command, values); it seems to me like executing an executemany once every 1000 values or so is better than calling cursor.execute(command % value) for each of these 5 million values (please confirm or correct me!).\nBut, you see, I am using an executemany to INSERT 1000 rows into a table which has a UNIQUE integrity constraint; this constraint is not verified in python beforehand, for this would either require me to SELECT all the time (this seems counter productive) or require me to get more than 3 GB of RAM. All this to say that I count on Postgres to warn me when my script tried to INSERT an already existing row via catching the psycopg2.DatabaseError. \nWhen my script detects such a non-UNIQUE INSERT, it connection.rollback() (which makes ups to 1000 rows everytime, and kind of makes the executemany worthless) and then INSERTs all values one by one.\nSince psycopg2 is so poorly documented (as are so many great modules...), I cannot find an efficient and effective workaround. I have reduced the number of values INSERTed per executemany from 1000 to 100 in order to reduce the likeliness of a non-UNIQUE INSERT per executemany, but I am pretty certain their is a way to just tell psycopg2 to ignore these execeptions or to tell the cursor to continue the executemany. \nBasically, this seems like the kind of problem which has a solution so easy and popular, that all I can do is ask in order to learn about it.\nThanks again!","AnswerCount":4,"Available Count":2,"Score":-0.049958375,"is_accepted":false,"ViewCount":7742,"Q_Id":396455,"Users Score":-1,"Answer":"using a MERGE statement instead of an INSERT one would solve your problem.","Q_Score":6,"Tags":"python,postgresql,database,psycopg","A_Id":675865,"CreationDate":"2008-12-28T17:51:00.000","Title":"Python-PostgreSQL psycopg2 interface --> executemany","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am currently analyzing a wikipedia dump file; I am extracting a bunch of data from it using python and persisting it into a PostgreSQL db. I am always trying to make things go faster for this file is huge (18GB). In order to interface with PostgreSQL, I am using psycopg2, but this module seems to mimic many other such DBAPIs.\nAnyway, I have a question concerning cursor.executemany(command, values); it seems to me like executing an executemany once every 1000 values or so is better than calling cursor.execute(command % value) for each of these 5 million values (please confirm or correct me!).\nBut, you see, I am using an executemany to INSERT 1000 rows into a table which has a UNIQUE integrity constraint; this constraint is not verified in python beforehand, for this would either require me to SELECT all the time (this seems counter productive) or require me to get more than 3 GB of RAM. All this to say that I count on Postgres to warn me when my script tried to INSERT an already existing row via catching the psycopg2.DatabaseError. \nWhen my script detects such a non-UNIQUE INSERT, it connection.rollback() (which makes ups to 1000 rows everytime, and kind of makes the executemany worthless) and then INSERTs all values one by one.\nSince psycopg2 is so poorly documented (as are so many great modules...), I cannot find an efficient and effective workaround. I have reduced the number of values INSERTed per executemany from 1000 to 100 in order to reduce the likeliness of a non-UNIQUE INSERT per executemany, but I am pretty certain their is a way to just tell psycopg2 to ignore these execeptions or to tell the cursor to continue the executemany. \nBasically, this seems like the kind of problem which has a solution so easy and popular, that all I can do is ask in order to learn about it.\nThanks again!","AnswerCount":4,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":7742,"Q_Id":396455,"Users Score":0,"Answer":"\"When my script detects such a non-UNIQUE INSERT, it connection.rollback() (which makes ups to 1000 rows everytime, and kind of makes the executemany worthless) and then INSERTs all values one by one.\"\nThe question doesn't really make a lot of sense.\nDoes EVERY block of 1,000 rows fail due to non-unique rows? \nDoes 1 block of 1,000 rows fail (out 5,000 such blocks)?  If so, then the execute many helps for 4,999 out of 5,000 and is far from \"worthless\".\nAre you worried about this non-Unique insert?  Or do you have actual statistics on the number of times this happens?\nIf you've switched from 1,000 row blocks to 100 row blocks, you can -- obviously -- determine if there's a performance advantage for 1,000 row blocks, 100 row blocks and 1 row blocks.\nPlease actually run the actual program with actual database and different size blocks and post the numbers.","Q_Score":6,"Tags":"python,postgresql,database,psycopg","A_Id":396824,"CreationDate":"2008-12-28T17:51:00.000","Title":"Python-PostgreSQL psycopg2 interface --> executemany","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm wondering, is it possible to make an sql query that does the same function as \n'select products where barcode in table1 = barcode in table2'. I am writing this function in a python program. Once that function is called will the table be joined permanently or just while that function is running?\nthanks.","AnswerCount":6,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":680,"Q_Id":403527,"Users Score":0,"Answer":"Here is an example of inner joining two tables based on a common field in both tables.\nSELECT table1.Products\nFROM table1 \nINNER JOIN table2 on table1.barcode = table2.barcode\nWHERE table1.Products is not null","Q_Score":0,"Tags":"python,sql","A_Id":403848,"CreationDate":"2008-12-31T17:20:00.000","Title":"Making a SQL Query in two tables","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm wondering, is it possible to make an sql query that does the same function as \n'select products where barcode in table1 = barcode in table2'. I am writing this function in a python program. Once that function is called will the table be joined permanently or just while that function is running?\nthanks.","AnswerCount":6,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":680,"Q_Id":403527,"Users Score":0,"Answer":"Here's a way to talk yourself through table design in these cases, based on Object Role Modeling. (Yes, I realize this is only indirectly related to the question.)\nYou have products and barcodes. Products are uniquely identified by Product Code (e.g. 'A2111'; barcodes are uniquely identified by Value (e.g. 1002155061).\nA Product has a Barcode. Questions: Can a product have no barcode? Can the same product have multiple barcodes? Can multiple products have the same barcode? (If you have any experience with UPC labels, you know the answer to all these is TRUE.)\nSo you can make some assertions:  \nA Product (code) has zero or more Barcode (value).\nA Barcode (value) has one or more Product (code). -- assumption: we barcodes don't have independent existence if they aren't\/haven't been\/won't be related to products).\nWhich leads directly (via your ORM model) to a schema with two tables:  \nProduct\nProductCode(PK)  Description etc\nProductBarcode\nProductCode(FK)   BarcodeValue\n-- with a two-part natural primary key, ProductCode + BarcodeValue  \nand you tie them together as described in the other answers.\nSimilar assertions can be used to determine which fields go into various tables in your design.","Q_Score":0,"Tags":"python,sql","A_Id":403904,"CreationDate":"2008-12-31T17:20:00.000","Title":"Making a SQL Query in two tables","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"What is the difference between these two apis?\nWhich one faster, reliable using Python DB API?\nUpd:\nI see two psql drivers for Django. The first one is psycopg2.\nWhat is the second one? pygresql?","AnswerCount":5,"Available Count":4,"Score":1.2,"is_accepted":true,"ViewCount":15364,"Q_Id":413228,"Users Score":5,"Answer":"For what it's worth, django uses psycopg2.","Q_Score":13,"Tags":"python,postgresql","A_Id":413259,"CreationDate":"2009-01-05T14:21:00.000","Title":"PyGreSQL vs psycopg2","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"What is the difference between these two apis?\nWhich one faster, reliable using Python DB API?\nUpd:\nI see two psql drivers for Django. The first one is psycopg2.\nWhat is the second one? pygresql?","AnswerCount":5,"Available Count":4,"Score":0.0,"is_accepted":false,"ViewCount":15364,"Q_Id":413228,"Users Score":0,"Answer":"psycopg2 is partly written in C so you can expect a performance gain, but on the other hand, a bit harder to install. PyGreSQL is written in Python only, easy to deployed but slower.","Q_Score":13,"Tags":"python,postgresql","A_Id":413508,"CreationDate":"2009-01-05T14:21:00.000","Title":"PyGreSQL vs psycopg2","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"What is the difference between these two apis?\nWhich one faster, reliable using Python DB API?\nUpd:\nI see two psql drivers for Django. The first one is psycopg2.\nWhat is the second one? pygresql?","AnswerCount":5,"Available Count":4,"Score":0.1586485043,"is_accepted":false,"ViewCount":15364,"Q_Id":413228,"Users Score":4,"Answer":"\"PyGreSQL is written in Python only, easy to deployed but slower.\"\nPyGreSQL contains a C-coded module, too. I haven't done speed tests, but they're not likely to be much different, as the real work will happen inside the database server.","Q_Score":13,"Tags":"python,postgresql","A_Id":592846,"CreationDate":"2009-01-05T14:21:00.000","Title":"PyGreSQL vs psycopg2","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"What is the difference between these two apis?\nWhich one faster, reliable using Python DB API?\nUpd:\nI see two psql drivers for Django. The first one is psycopg2.\nWhat is the second one? pygresql?","AnswerCount":5,"Available Count":4,"Score":0.0798297691,"is_accepted":false,"ViewCount":15364,"Q_Id":413228,"Users Score":2,"Answer":"Licensing may be an issue for you. PyGreSQL is MIT license. Psycopg2 is GPL license.\n(as long as you are accessing psycopg2 in normal ways from Python, with no internal API, and no direct C calls, this shouldn't cause you any headaches, and you can release your code under whatever license you like - but I am not a lawyer).","Q_Score":13,"Tags":"python,postgresql","A_Id":413537,"CreationDate":"2009-01-05T14:21:00.000","Title":"PyGreSQL vs psycopg2","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"The beauty of ORM lulled me into a soporific sleep. I've got an existing Django app with a lack of database indexes. Is there a way to automatically generate a list of columns that need indexing?\nI was thinking maybe some middleware that logs which columns are involved in WHERE clauses? but is there anything built into MySQL that might help?","AnswerCount":2,"Available Count":1,"Score":0.3799489623,"is_accepted":false,"ViewCount":620,"Q_Id":438559,"Users Score":4,"Answer":"No.\nAdding indexes willy-nilly to all \"slow\" queries will also slow down inserts, updates and deletes.\nIndexes are a balancing act between fast queries and fast changes.  There is no general or \"right\" answer.  There's certainly nothing that can automate this.\nYou have to measure the improvement across your whole application as you add and change indexes.","Q_Score":5,"Tags":"python,mysql,database,django,django-models","A_Id":438700,"CreationDate":"2009-01-13T10:36:00.000","Title":"Is there a way to automatically generate a list of columns that need indexing?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm looking for some quick thoughts about a business application I am looking to build. I'd like to separate the three layers of presentation, domain logic, and data using PHP, Python, and PostgreSQL, respectively.  I would like to hear, possibly from other folks who have gone down this path before, if there are problems with this approach, if I am targeting the wrong tools, etc.\n\nI'm looking at PHP because it is widely used, fairly mature, and I can find ample people with skills in PHP interface design.\nI'm looking at Python because of the benefits of readable code, because I hear can find more Python programmers that also have subject-matter skills (in this case, finance), and it's an open source language. Plus, it seems easier to code with.\nI'm looking at PostgreSQL for the transaction-level features. MySQL is also an option here, but I don't need to debate this aspect.\n\nThis is not a web application, although I would like to utilize a browser for the user interface. This is more of an Enterprise Application, but for a small business with moderate numbers of users (maybe 5-10) and a modest number of daily transactions. \nWhat is important is that we are able to upgrade the database or domain logic or interface separate from the other layers in the future.\nI'm NOT looking for a buy vs. build debate, as that's a different discussion.\nThanks for any insight","AnswerCount":7,"Available Count":6,"Score":0.0,"is_accepted":false,"ViewCount":2512,"Q_Id":439759,"Users Score":0,"Answer":"Just to throw it out there... there are PHP frameworks utilizing MVC.\nCodeigniter does simple and yet powerful things. You can definitely separate the template layer from the logic layer.","Q_Score":2,"Tags":"php,python,postgresql","A_Id":494119,"CreationDate":"2009-01-13T16:47:00.000","Title":"Is a PHP, Python, PostgreSQL design suitable for a business application?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm looking for some quick thoughts about a business application I am looking to build. I'd like to separate the three layers of presentation, domain logic, and data using PHP, Python, and PostgreSQL, respectively.  I would like to hear, possibly from other folks who have gone down this path before, if there are problems with this approach, if I am targeting the wrong tools, etc.\n\nI'm looking at PHP because it is widely used, fairly mature, and I can find ample people with skills in PHP interface design.\nI'm looking at Python because of the benefits of readable code, because I hear can find more Python programmers that also have subject-matter skills (in this case, finance), and it's an open source language. Plus, it seems easier to code with.\nI'm looking at PostgreSQL for the transaction-level features. MySQL is also an option here, but I don't need to debate this aspect.\n\nThis is not a web application, although I would like to utilize a browser for the user interface. This is more of an Enterprise Application, but for a small business with moderate numbers of users (maybe 5-10) and a modest number of daily transactions. \nWhat is important is that we are able to upgrade the database or domain logic or interface separate from the other layers in the future.\nI'm NOT looking for a buy vs. build debate, as that's a different discussion.\nThanks for any insight","AnswerCount":7,"Available Count":6,"Score":0.0,"is_accepted":false,"ViewCount":2512,"Q_Id":439759,"Users Score":0,"Answer":"I personally agree with the second and the third points in your post. Speaking about PHP, in my opinion you can use Python also for presentation, there are many solutions (Zope, Plone ...) based on Python.","Q_Score":2,"Tags":"php,python,postgresql","A_Id":439793,"CreationDate":"2009-01-13T16:47:00.000","Title":"Is a PHP, Python, PostgreSQL design suitable for a business application?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm looking for some quick thoughts about a business application I am looking to build. I'd like to separate the three layers of presentation, domain logic, and data using PHP, Python, and PostgreSQL, respectively.  I would like to hear, possibly from other folks who have gone down this path before, if there are problems with this approach, if I am targeting the wrong tools, etc.\n\nI'm looking at PHP because it is widely used, fairly mature, and I can find ample people with skills in PHP interface design.\nI'm looking at Python because of the benefits of readable code, because I hear can find more Python programmers that also have subject-matter skills (in this case, finance), and it's an open source language. Plus, it seems easier to code with.\nI'm looking at PostgreSQL for the transaction-level features. MySQL is also an option here, but I don't need to debate this aspect.\n\nThis is not a web application, although I would like to utilize a browser for the user interface. This is more of an Enterprise Application, but for a small business with moderate numbers of users (maybe 5-10) and a modest number of daily transactions. \nWhat is important is that we are able to upgrade the database or domain logic or interface separate from the other layers in the future.\nI'm NOT looking for a buy vs. build debate, as that's a different discussion.\nThanks for any insight","AnswerCount":7,"Available Count":6,"Score":0.0,"is_accepted":false,"ViewCount":2512,"Q_Id":439759,"Users Score":0,"Answer":"Just skip PHP and use Python (with Django, as already noticed while I typed). Django already separates the layers as you mentioned.\nI have never used PgSQL myself, but I think it's mostly a matter of taste whether you prefer it over MySQL. It used to support more enterprise features than MySQL but I'm not sure if that's still true with MySQL 5.0 and 5.1. Transactions are supported in MySQL, anyway (you have to use the InnoDB table engine, however).","Q_Score":2,"Tags":"php,python,postgresql","A_Id":439818,"CreationDate":"2009-01-13T16:47:00.000","Title":"Is a PHP, Python, PostgreSQL design suitable for a business application?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm looking for some quick thoughts about a business application I am looking to build. I'd like to separate the three layers of presentation, domain logic, and data using PHP, Python, and PostgreSQL, respectively.  I would like to hear, possibly from other folks who have gone down this path before, if there are problems with this approach, if I am targeting the wrong tools, etc.\n\nI'm looking at PHP because it is widely used, fairly mature, and I can find ample people with skills in PHP interface design.\nI'm looking at Python because of the benefits of readable code, because I hear can find more Python programmers that also have subject-matter skills (in this case, finance), and it's an open source language. Plus, it seems easier to code with.\nI'm looking at PostgreSQL for the transaction-level features. MySQL is also an option here, but I don't need to debate this aspect.\n\nThis is not a web application, although I would like to utilize a browser for the user interface. This is more of an Enterprise Application, but for a small business with moderate numbers of users (maybe 5-10) and a modest number of daily transactions. \nWhat is important is that we are able to upgrade the database or domain logic or interface separate from the other layers in the future.\nI'm NOT looking for a buy vs. build debate, as that's a different discussion.\nThanks for any insight","AnswerCount":7,"Available Count":6,"Score":0.0285636566,"is_accepted":false,"ViewCount":2512,"Q_Id":439759,"Users Score":1,"Answer":"I can only repeat what other peoples here already said : if you choose Python for the domain layer, you won't gain anything (quite on the contrary) using PHP for the presentation layer. Others already advised Django, and that might be a pretty good choice, but there's no shortage of good Python web frameworks.","Q_Score":2,"Tags":"php,python,postgresql","A_Id":440496,"CreationDate":"2009-01-13T16:47:00.000","Title":"Is a PHP, Python, PostgreSQL design suitable for a business application?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm looking for some quick thoughts about a business application I am looking to build. I'd like to separate the three layers of presentation, domain logic, and data using PHP, Python, and PostgreSQL, respectively.  I would like to hear, possibly from other folks who have gone down this path before, if there are problems with this approach, if I am targeting the wrong tools, etc.\n\nI'm looking at PHP because it is widely used, fairly mature, and I can find ample people with skills in PHP interface design.\nI'm looking at Python because of the benefits of readable code, because I hear can find more Python programmers that also have subject-matter skills (in this case, finance), and it's an open source language. Plus, it seems easier to code with.\nI'm looking at PostgreSQL for the transaction-level features. MySQL is also an option here, but I don't need to debate this aspect.\n\nThis is not a web application, although I would like to utilize a browser for the user interface. This is more of an Enterprise Application, but for a small business with moderate numbers of users (maybe 5-10) and a modest number of daily transactions. \nWhat is important is that we are able to upgrade the database or domain logic or interface separate from the other layers in the future.\nI'm NOT looking for a buy vs. build debate, as that's a different discussion.\nThanks for any insight","AnswerCount":7,"Available Count":6,"Score":0.0285636566,"is_accepted":false,"ViewCount":2512,"Q_Id":439759,"Users Score":1,"Answer":"I'm going to assume that by \"business application\" you mean a web application hosted in an intranet environment as opposed to some sort of SaaS application on the internet.\nWhile you're in the process of architecting your application you need to consider the existing infrastructure and infrastructure support people of your employer\/customer.  Also, if the company is large enough to have things such as \"approved software\/hardware lists,\" you should be aware of those.  Keep in mind that some elements of the list may be downright retarded.  Don't let past mistakes dictate the architecture of your app, but in cases where they are reasonably sensible I would pick my battles and stick with your enterprise standard.  This can be a real pain when you pick a development stack that really works best on Unix\/Linux, and then someone tries to force onto a Windows server admined by someone who's never touched anything but ASP.NET applications.\nUnless there is a particular PHP module that you intend to use that has no Python equivalent, I would drop PHP and use Django.  If there is a compelling reason to use PHP, then I'd drop Python.  I'm having difficulty imagining a scenario where you would want to use both at the same time.\nAs for PG versus MySQL, either works.  Look at what you customer already has deployed, and if they have a bunch of one and little of another, pick that.  If they have existing Oracle infrastructure you should consider using it.  If they are an SQL Server shop...reconsider your stack and remember to pick your battles.","Q_Score":2,"Tags":"php,python,postgresql","A_Id":440118,"CreationDate":"2009-01-13T16:47:00.000","Title":"Is a PHP, Python, PostgreSQL design suitable for a business application?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm looking for some quick thoughts about a business application I am looking to build. I'd like to separate the three layers of presentation, domain logic, and data using PHP, Python, and PostgreSQL, respectively.  I would like to hear, possibly from other folks who have gone down this path before, if there are problems with this approach, if I am targeting the wrong tools, etc.\n\nI'm looking at PHP because it is widely used, fairly mature, and I can find ample people with skills in PHP interface design.\nI'm looking at Python because of the benefits of readable code, because I hear can find more Python programmers that also have subject-matter skills (in this case, finance), and it's an open source language. Plus, it seems easier to code with.\nI'm looking at PostgreSQL for the transaction-level features. MySQL is also an option here, but I don't need to debate this aspect.\n\nThis is not a web application, although I would like to utilize a browser for the user interface. This is more of an Enterprise Application, but for a small business with moderate numbers of users (maybe 5-10) and a modest number of daily transactions. \nWhat is important is that we are able to upgrade the database or domain logic or interface separate from the other layers in the future.\nI'm NOT looking for a buy vs. build debate, as that's a different discussion.\nThanks for any insight","AnswerCount":7,"Available Count":6,"Score":0.0,"is_accepted":false,"ViewCount":2512,"Q_Id":439759,"Users Score":0,"Answer":"Just to address the MySQL vs PgSQL issues - it shouldn't matter. They're both more than capable of the task, and any reasonable framework should isolate you from the differences relatively well. I think it's down to what you use already, what people have most experience in, and if there's a feature in one or the other you think you'd benefit from.\nIf you have no preference, you might want to go with MySQL purely because it's more popular for web work. This translates to more examples, easier to find help, etc. I actually prefer the philosophy of PgSQL, but this isn't a good enough reason to blow against the wind.","Q_Score":2,"Tags":"php,python,postgresql","A_Id":440098,"CreationDate":"2009-01-13T16:47:00.000","Title":"Is a PHP, Python, PostgreSQL design suitable for a business application?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Example Problem:\nEntities:\n\nUser contains name and a list of friends (User references)\nBlog Post contains title, content, date and Writer (User)\n\nRequirement:\nI want a page that displays the title and a link to the blog of the last 10 posts by a user's friend.  I would also like the ability to keep paging back through older entries.\nSQL Solution:\nSo in sql land it would be something like:\n\nselect * from blog_post where user_id in (select friend_id from user_friend where user_id = :userId) order by date\n\nGAE solutions i can think of are:\n\nLoad user, loop through the list of friends and load their latest blog posts.  Finally merge all the blog posts to find the latest 10 blog entries\nIn a blog post have a list of all users that have the writer as a friend.  This would mean a simple read but would result in quota overload when adding a friend who has lots of blog posts.\n\nI don't believe either of these solutions will scale.\nIm sure others have hit this problem but I've searched, watched google io videos, read other's code ...  What am i missing?","AnswerCount":4,"Available Count":2,"Score":1.0,"is_accepted":false,"ViewCount":2112,"Q_Id":445827,"Users Score":13,"Answer":"If you look at how the SQL solution you provided will be executed, it will go basically like this:\n\nFetch a list of friends for the current user\nFor each user in the list, start an index scan over recent posts\nMerge-join all the scans from step 2, stopping when you've retrieved enough entries\n\nYou can carry out exactly the same procedure yourself in App Engine, by using the Query instances as iterators and doing a merge join over them.\nYou're right that this will not scale well to large numbers of friends, but it suffers from exactly the same issues the SQL implementation has, it just doesn't disguise them as well: Fetching the latest 20 (for example) entries costs roughly O(n log n) work, where n is the number of friends.","Q_Score":13,"Tags":"python,google-app-engine,join,google-cloud-datastore","A_Id":446471,"CreationDate":"2009-01-15T06:07:00.000","Title":"GAE - How to live with no joins?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"Example Problem:\nEntities:\n\nUser contains name and a list of friends (User references)\nBlog Post contains title, content, date and Writer (User)\n\nRequirement:\nI want a page that displays the title and a link to the blog of the last 10 posts by a user's friend.  I would also like the ability to keep paging back through older entries.\nSQL Solution:\nSo in sql land it would be something like:\n\nselect * from blog_post where user_id in (select friend_id from user_friend where user_id = :userId) order by date\n\nGAE solutions i can think of are:\n\nLoad user, loop through the list of friends and load their latest blog posts.  Finally merge all the blog posts to find the latest 10 blog entries\nIn a blog post have a list of all users that have the writer as a friend.  This would mean a simple read but would result in quota overload when adding a friend who has lots of blog posts.\n\nI don't believe either of these solutions will scale.\nIm sure others have hit this problem but I've searched, watched google io videos, read other's code ...  What am i missing?","AnswerCount":4,"Available Count":2,"Score":0.049958375,"is_accepted":false,"ViewCount":2112,"Q_Id":445827,"Users Score":1,"Answer":"\"Load user, loop through the list of friends and load their latest blog posts.\"\nThat's all a join is -- nested loops.  Some kinds of joins are loops with lookups.  Most lookups are just loops; some are hashes.\n\"Finally merge all the blog posts to find the latest 10 blog entries\"\nThat's a ORDER BY with a LIMIT.  That's what the database is doing for you.\nI'm not sure what's not scalable about this; it's what a database does anyway.","Q_Score":13,"Tags":"python,google-app-engine,join,google-cloud-datastore","A_Id":446477,"CreationDate":"2009-01-15T06:07:00.000","Title":"GAE - How to live with no joins?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I am using plone.app.blob to store large ZODB objects in a blobstorage directory. This reduces size pressure on Data.fs but I have not been able to find any advice on backing up this data.\nI am already backing up Data.fs by pointing a network backup tool at a directory of repozo backups. Should I simply point that tool at the blobstorage directory to backup my blobs? \nWhat if the database is being repacked or blobs are being added and deleted while the copy is taking place? Are there files in the blobstorage directory that must be copied over in a certain order?","AnswerCount":4,"Available Count":3,"Score":1.0,"is_accepted":false,"ViewCount":2618,"Q_Id":451952,"Users Score":13,"Answer":"It should be safe to do a repozo backup of the Data.fs followed by an rsync of the blobstorage directory, as long as the database doesn't get packed while those two operations are happening.\nThis is because, at least when using blobs with FileStorage, modifications to a blob always results in the creation of a new file named based on the object id and transaction id.  So if new or updated blobs are written after the Data.fs is backed up, it shouldn't be a problem, as the files that are referenced by the Data.fs should still be around.  Deletion of a blob doesn't result in the file being removed until the database is packed, so that should be okay too.\nPerforming a backup in a different order, or with packing during the backup, may result in a backup Data.fs that references blobs that are not included in the backup.","Q_Score":8,"Tags":"python,plone,zope,zodb,blobstorage","A_Id":2664479,"CreationDate":"2009-01-16T20:51:00.000","Title":"What is the correct way to backup ZODB blobs?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am using plone.app.blob to store large ZODB objects in a blobstorage directory. This reduces size pressure on Data.fs but I have not been able to find any advice on backing up this data.\nI am already backing up Data.fs by pointing a network backup tool at a directory of repozo backups. Should I simply point that tool at the blobstorage directory to backup my blobs? \nWhat if the database is being repacked or blobs are being added and deleted while the copy is taking place? Are there files in the blobstorage directory that must be copied over in a certain order?","AnswerCount":4,"Available Count":3,"Score":1.2,"is_accepted":true,"ViewCount":2618,"Q_Id":451952,"Users Score":3,"Answer":"Backing up \"blobstorage\" will do it. No need for a special order or anything else, it's very simple.\nAll operations in Plone are fully transactional, so hitting the backup in the middle of a transaction should work just fine. This is why you can do live backups of the ZODB. Without knowing what file system you're on, I'd guess that it should work as intended.","Q_Score":8,"Tags":"python,plone,zope,zodb,blobstorage","A_Id":453942,"CreationDate":"2009-01-16T20:51:00.000","Title":"What is the correct way to backup ZODB blobs?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am using plone.app.blob to store large ZODB objects in a blobstorage directory. This reduces size pressure on Data.fs but I have not been able to find any advice on backing up this data.\nI am already backing up Data.fs by pointing a network backup tool at a directory of repozo backups. Should I simply point that tool at the blobstorage directory to backup my blobs? \nWhat if the database is being repacked or blobs are being added and deleted while the copy is taking place? Are there files in the blobstorage directory that must be copied over in a certain order?","AnswerCount":4,"Available Count":3,"Score":0.049958375,"is_accepted":false,"ViewCount":2618,"Q_Id":451952,"Users Score":1,"Answer":"Your backup strategy for the FileStorage is fine. However, making a backup of any database that stores data in multiple files never is easy as your copy has to happen with no writes to the various files. For the FileStorage a blind stupid copy is fine as it's just a single file. (Using repozo is even better.)\nIn this case (with BlobStorage combined with FileStorage) I have to point to the regular backup advice:\n\ntake the db offline while making a file-system copy\nuse snapshot tools like LVM to freeze the disk at a given point\ndo a transactional export (not feasable in practice)","Q_Score":8,"Tags":"python,plone,zope,zodb,blobstorage","A_Id":676364,"CreationDate":"2009-01-16T20:51:00.000","Title":"What is the correct way to backup ZODB blobs?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am using Python version 2.5.4 and install MySQL version 5.0 and Django. Django is working fine with Python, but not MySQL. I am using it in Windows Vista.","AnswerCount":32,"Available Count":5,"Score":0.0312398314,"is_accepted":false,"ViewCount":804257,"Q_Id":454854,"Users Score":5,"Answer":"Go to your project directory with cd.\nsource\/bin\/activate (activate your env. if not previously).\nRun the command easy_install MySQL-python","Q_Score":493,"Tags":"python,django,python-2.x","A_Id":28278997,"CreationDate":"2009-01-18T09:13:00.000","Title":"No module named MySQLdb","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am using Python version 2.5.4 and install MySQL version 5.0 and Django. Django is working fine with Python, but not MySQL. I am using it in Windows Vista.","AnswerCount":32,"Available Count":5,"Score":1.0,"is_accepted":false,"ViewCount":804257,"Q_Id":454854,"Users Score":6,"Answer":"I personally recommend using pymysql instead of using the genuine MySQL connector, which provides you with a platform independent interface and could be installed through pip.\nAnd you could edit the SQLAlchemy URL schema like this:\nmysql+pymysql:\/\/username:passwd@host\/database","Q_Score":493,"Tags":"python,django,python-2.x","A_Id":58246337,"CreationDate":"2009-01-18T09:13:00.000","Title":"No module named MySQLdb","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am using Python version 2.5.4 and install MySQL version 5.0 and Django. Django is working fine with Python, but not MySQL. I am using it in Windows Vista.","AnswerCount":32,"Available Count":5,"Score":1.0,"is_accepted":false,"ViewCount":804257,"Q_Id":454854,"Users Score":93,"Answer":"if your python version is 3.5, do a pip install mysqlclient, other things didn't work for me","Q_Score":493,"Tags":"python,django,python-2.x","A_Id":38310817,"CreationDate":"2009-01-18T09:13:00.000","Title":"No module named MySQLdb","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am using Python version 2.5.4 and install MySQL version 5.0 and Django. Django is working fine with Python, but not MySQL. I am using it in Windows Vista.","AnswerCount":32,"Available Count":5,"Score":0.012499349,"is_accepted":false,"ViewCount":804257,"Q_Id":454854,"Users Score":2,"Answer":"None of the above worked for me on an Ubuntu 18.04 fresh install via docker image.\nThe following solved it for me:\napt-get install holland python3-mysqldb","Q_Score":493,"Tags":"python,django,python-2.x","A_Id":58825148,"CreationDate":"2009-01-18T09:13:00.000","Title":"No module named MySQLdb","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am using Python version 2.5.4 and install MySQL version 5.0 and Django. Django is working fine with Python, but not MySQL. I am using it in Windows Vista.","AnswerCount":32,"Available Count":5,"Score":0.0,"is_accepted":false,"ViewCount":804257,"Q_Id":454854,"Users Score":0,"Answer":"For CentOS 8 and Python3\n$ sudo dnf install python3-mysqlclient -y","Q_Score":493,"Tags":"python,django,python-2.x","A_Id":72496371,"CreationDate":"2009-01-18T09:13:00.000","Title":"No module named MySQLdb","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I think I am being a bonehead, maybe not importing the right package, but when I do...\n\nfrom pysqlite2 import dbapi2 as sqlite\nimport types\nimport re\nimport sys\n...\n    def create_asgn(self):\n        stmt = \"CREATE TABLE ? (login CHAR(8) PRIMARY KEY NOT NULL, grade INTEGER NOT NULL)\"\n        stmt2 = \"insert into asgn values ('?', ?)\"\n        self.cursor.execute(stmt, (sys.argv[2],))\n        self.cursor.execute(stmt2, [sys.argv[2], sys.argv[3]])\n...\n I get the error pysqlite2.dbapi2.OperationalError: near \"?\": syntax error \nThis makes very little sense to me, as the docs show that pysqlite is qmark parametrized.  I am new to python and db-api though, help me out!  THANKS","AnswerCount":3,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1629,"Q_Id":474261,"Users Score":7,"Answer":"That's because parameters can only be passed to VALUES. The table name can't be parametrized.\nAlso you have quotes around a parametrized argument on the second query. Remove the quotes, escaping is handled by the underlining library automatically for you.","Q_Score":1,"Tags":"python,sqlite,pysqlite,python-db-api","A_Id":474296,"CreationDate":"2009-01-23T19:55:00.000","Title":"Python pysqlite not accepting my qmark parameterization","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have been working with PostgreSQL, playing around with Wikipedia's millions of hyperlinks and such, for 2 years now. I either do my thing directly by sending SQL commands, or I write a client side script in python to manage a million queries when this cannot be done productively (efficiently and effectively) manually. \nI would run my python script on my 32bit laptop and have it communicate with a $6000 64bit server running PostgreSQL; I would hence have an extra 2.10 Ghz, 3 GB of RAM, psyco and a multithreaded SQL query manager.\nI now realize that it is time for me to level up. I need to learn to server-side script using a procedural language (PL); I really need to reduce network traffic and its inherent serializing overhead. \nNow, I really do not feel like researching all the PLs. Knowing that I already know python, and that I am looking for the means between effort and language efficiency, what PL do you guys fancy I should install, learn and use, and why and how?","AnswerCount":3,"Available Count":2,"Score":0.0665680765,"is_accepted":false,"ViewCount":2801,"Q_Id":475302,"Users Score":1,"Answer":"I was in the exact same situation as you and went with PL\/Python after giving up on PL\/SQL after a while. It was a good decision, looking back. Some things that bit me where unicode issues (client encoding, byte sequence) and specific postgres data types (bytea).","Q_Score":3,"Tags":"python,postgresql","A_Id":476089,"CreationDate":"2009-01-24T01:38:00.000","Title":"PostgreSQL procedural languages: to choose?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have been working with PostgreSQL, playing around with Wikipedia's millions of hyperlinks and such, for 2 years now. I either do my thing directly by sending SQL commands, or I write a client side script in python to manage a million queries when this cannot be done productively (efficiently and effectively) manually. \nI would run my python script on my 32bit laptop and have it communicate with a $6000 64bit server running PostgreSQL; I would hence have an extra 2.10 Ghz, 3 GB of RAM, psyco and a multithreaded SQL query manager.\nI now realize that it is time for me to level up. I need to learn to server-side script using a procedural language (PL); I really need to reduce network traffic and its inherent serializing overhead. \nNow, I really do not feel like researching all the PLs. Knowing that I already know python, and that I am looking for the means between effort and language efficiency, what PL do you guys fancy I should install, learn and use, and why and how?","AnswerCount":3,"Available Count":2,"Score":0.1325487884,"is_accepted":false,"ViewCount":2801,"Q_Id":475302,"Users Score":2,"Answer":"Why can't you run your Python on the database server?  That has the fewest complexities -- you can run the program you already have.","Q_Score":3,"Tags":"python,postgresql","A_Id":475939,"CreationDate":"2009-01-24T01:38:00.000","Title":"PostgreSQL procedural languages: to choose?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Is there a good ORM (object relational manager) solution that can use the same database from C++, C#, Python?\nIt could also be multiple solutions, e.g. one per language, as long as they can can access the same database and use the same schema.\nMulti platform support is also needed.\nClarification:\nThe idea is to have one database and access this from software written in several different programming languages. Ideally this would be provided by one ORM having APIs (or bindings) in all of these languages.\nOne other solution is to have a different ORM in each language, that use compatible schemas. However I believe that schema migration will be very hard in this setting.","AnswerCount":3,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":1697,"Q_Id":482612,"Users Score":0,"Answer":"We have an O\/RM that has C++ and C# (actually COM) bindings (in FOST.3) and we're putting together the Python bindings which are new in version 4 together with Linux and Mac support.","Q_Score":7,"Tags":"c#,c++,python,orm","A_Id":496166,"CreationDate":"2009-01-27T08:10:00.000","Title":"ORM (object relational manager) solution with multiple programming language support","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Is there a good ORM (object relational manager) solution that can use the same database from C++, C#, Python?\nIt could also be multiple solutions, e.g. one per language, as long as they can can access the same database and use the same schema.\nMulti platform support is also needed.\nClarification:\nThe idea is to have one database and access this from software written in several different programming languages. Ideally this would be provided by one ORM having APIs (or bindings) in all of these languages.\nOne other solution is to have a different ORM in each language, that use compatible schemas. However I believe that schema migration will be very hard in this setting.","AnswerCount":3,"Available Count":2,"Score":0.0665680765,"is_accepted":false,"ViewCount":1697,"Q_Id":482612,"Users Score":1,"Answer":"With SQLAlchemy, you can use reflection to get the schema, so it should work with any of the supported engines.\nI've used this to migrate data from an old SQLite to Postgres.","Q_Score":7,"Tags":"c#,c++,python,orm","A_Id":482653,"CreationDate":"2009-01-27T08:10:00.000","Title":"ORM (object relational manager) solution with multiple programming language support","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Here is the situation: I have a parent model say BlogPost. It has many Comments. What I want is the list of BlogPosts ordered by the creation date of its' Comments. I.e. the blog post which has the most newest comment should be on top of the list. Is this possible with SQLAlchemy?","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":595,"Q_Id":492223,"Users Score":1,"Answer":"I had the same question as the parent when using the ORM, and GHZ's link contained the answer on how it's possible. In sqlalchemy, assuming BlogPost.comments is a mapped relation to the Comments table, you can't do:\n\nsession.query(BlogPost).order_by(BlogPost.comments.creationDate.desc())\n\n, but you can do:\n\nsession.query(BlogPost).join(Comments).order_by(Comments.creationDate.desc())","Q_Score":3,"Tags":"python,sqlalchemy","A_Id":1227979,"CreationDate":"2009-01-29T16:01:00.000","Title":"How can I order objects according to some attribute of the child in sqlalchemy?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a small project I am doing in Python using web.py. It's a name generator, using 4 \"parts\" of a name (firstname, middlename, anothername, surname). Each part of the name is a collection of entites in a MySQL databse (name_part (id, part, type_id), and name_part_type (id, description)). Basic stuff, I guess.\nMy generator picks a random entry of each \"type\", and assembles a comical name. Right now, I am using select * from name_part where type_id=[something] order by rand() limit 1 to select a random entry of each type (so I also have 4 queries that run per pageview, I figured this was better than one fat query returning potentially hundreds of rows; if you have a suggestion for how to pull this off in one query w\/o a sproc I'll listen).\nObviously I want to make this more random. Actually, I want to give it better coverage, not necessarily randomness. I want to make sure it's using as many possibilities as possible. That's what I am asking in this question, what sorts of strategies can I use to give coverage over a large random sample? \nMy idea, is to implement a counter column on each name_part, and increment it each time I use it. I would need some logic to then say like: \"get a name_part that is less than the highest \"counter\" for this \"name_part_type\", unless there are none then pick a random one\". I am not very good at SQL, is this kind of logic even possible? The only way I can think to do this would require up to 3 or 4 queries for each part of the name (so up to 12 queries per pageview). \nCan I get some input on my logic here? Am I overthinking it? This actually sounds ideal for a stored procedure... but can you guys at least help me solve how to do it without a sproc? (I don't know if I can even use a sproc with the built-in database stuff of web.py).\nI hope this isn't terribly dumb but thanks ahead of time. \nedit: Aside from my specific problem I am still curious if there are any alternate strategies I can use that may be better.","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":1758,"Q_Id":514617,"Users Score":1,"Answer":"I agree with your intuition that using a stored procedure is the right way to go, but then, I almost always try to implement database stuff in the database.\nIn your proc, I would introduce some kind of logic like say, there's only a 30% chance that returning the result will actually increment the counter. Just to increase the variability.","Q_Score":4,"Tags":"python,mysql,random,web.py","A_Id":514643,"CreationDate":"2009-02-05T04:51:00.000","Title":"Random name generator strategy - help me improve it","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I've got a legacy application which is implemented in a number of Excel workbooks. It's not something that I have the authority to re-implement, however another application that I do maintain does need to be able to call functions in the Excel workbook. \nIt's been given a python interface using the Win32Com library. Other processes can call functions in my python package which in turn invokes the functions I need via Win32Com.\nUnfortunately COM does not allow me to specify a particular COM process, so at the moment no matter how powerful my server I can only control one instance of Excel at a time on the computer. If I were to try to run more than one instance of excel there would be no way of ensuring that the python layer is bound to a specific Excel instance. \nI'd like to be able to run more than 1 of my excel applications on my Windows server concurrently. Is there a way to do this? For example, could I compartmentalize my environment so that I could run as many Excel _ Python combinations as my application will support?","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":4391,"Q_Id":516946,"Users Score":0,"Answer":"If you application uses a single excel file which contains macros which you call, I fear the answer is probably no since aside from COM Excel does not allow the same file to be opened with the same name (even if in different directories).  You may be able to get around this by dynamically copying the file to another name before opening. \nMy python knowledge isn't huge, but in most languages there is a way of specifying when you  create a COM object whether you wish it to be a new object or connect to a preexisting instance by default.  Check the python docs for something along these lines.\nCan you list the kind of specific problems you are having and exactly what you are hoping to do?","Q_Score":6,"Tags":"python,windows,excel,com","A_Id":516983,"CreationDate":"2009-02-05T17:32:00.000","Title":"Control 2 separate Excel instances by COM independently... can it be done?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am getting the error OperationalError: FATAL: sorry, too many clients already when using psycopg2. I am calling the close method on my connection instance after I am done with it. I am not sure what could be causing this, it is my first experience with python and postgresql, but I have a few years experience with php, asp.net, mysql, and sql server.\nEDIT: I am running this locally, if the connections are closing like they should be then I only have 1 connection open at a time. I did have a GUI open to the database but even closed I am getting this error. It is happening very shortly after I run my program. I have a function I call that returns a connection that is opened like:\npsycopg2.connect(connectionString)\nThanks\nFinal Edit:\nIt was my mistake, I was recursively calling the same method on mistake that was opening the same method over and over. It has been a long day..","AnswerCount":3,"Available Count":3,"Score":0.1973753202,"is_accepted":false,"ViewCount":27905,"Q_Id":519296,"Users Score":3,"Answer":"Make sure your db connection command isn't in any kind of loop.  I was getting the same error from my script until I moved my db.database() out of my programs repeating execution loop.","Q_Score":22,"Tags":"python,postgresql,psycopg2","A_Id":15046529,"CreationDate":"2009-02-06T06:15:00.000","Title":"Getting OperationalError: FATAL: sorry, too many clients already using psycopg2","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am getting the error OperationalError: FATAL: sorry, too many clients already when using psycopg2. I am calling the close method on my connection instance after I am done with it. I am not sure what could be causing this, it is my first experience with python and postgresql, but I have a few years experience with php, asp.net, mysql, and sql server.\nEDIT: I am running this locally, if the connections are closing like they should be then I only have 1 connection open at a time. I did have a GUI open to the database but even closed I am getting this error. It is happening very shortly after I run my program. I have a function I call that returns a connection that is opened like:\npsycopg2.connect(connectionString)\nThanks\nFinal Edit:\nIt was my mistake, I was recursively calling the same method on mistake that was opening the same method over and over. It has been a long day..","AnswerCount":3,"Available Count":3,"Score":1.2,"is_accepted":true,"ViewCount":27905,"Q_Id":519296,"Users Score":15,"Answer":"This error means what it says, there are too many clients connected to postgreSQL.\nQuestions you should ask yourself:\n\nAre you the only one connected to this database?\nAre you running a graphical IDE?\nWhat method are you using to connect?\nAre you testing queries at the same time that you running the code?\n\nAny of these things could be the problem. If you are the admin, you can up the number of clients, but if a program is hanging it open, then that won't help for long.\nThere are many reasons why you could be having too many clients running at the same time.","Q_Score":22,"Tags":"python,postgresql,psycopg2","A_Id":519304,"CreationDate":"2009-02-06T06:15:00.000","Title":"Getting OperationalError: FATAL: sorry, too many clients already using psycopg2","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am getting the error OperationalError: FATAL: sorry, too many clients already when using psycopg2. I am calling the close method on my connection instance after I am done with it. I am not sure what could be causing this, it is my first experience with python and postgresql, but I have a few years experience with php, asp.net, mysql, and sql server.\nEDIT: I am running this locally, if the connections are closing like they should be then I only have 1 connection open at a time. I did have a GUI open to the database but even closed I am getting this error. It is happening very shortly after I run my program. I have a function I call that returns a connection that is opened like:\npsycopg2.connect(connectionString)\nThanks\nFinal Edit:\nIt was my mistake, I was recursively calling the same method on mistake that was opening the same method over and over. It has been a long day..","AnswerCount":3,"Available Count":3,"Score":0.0665680765,"is_accepted":false,"ViewCount":27905,"Q_Id":519296,"Users Score":1,"Answer":"It simple means many clients are making transaction to PostgreSQL at same time.\nI was running Postgis container and Django in different docker container. Hence for my case restarting both db and system container solved the problem.","Q_Score":22,"Tags":"python,postgresql,psycopg2","A_Id":64746356,"CreationDate":"2009-02-06T06:15:00.000","Title":"Getting OperationalError: FATAL: sorry, too many clients already using psycopg2","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm working on an application that will gather data through HTTP from several places, cache the data locally and then serve it through HTTP.\nSo I was looking at the following. My application will first create several threads that will gather data at a specified interval and cache that data locally into a SQLite database.   \nThen in the main thread start a CherryPy application that will query that SQLite database and serve the data.\nMy problem is: how do I handle connections to the SQLite database from my threads and from the CherryPy application?\nIf I'd do a connection per thread to the database will I also be able to create\/use an in memory database?","AnswerCount":6,"Available Count":4,"Score":0.0,"is_accepted":false,"ViewCount":13542,"Q_Id":524797,"Users Score":0,"Answer":"Depending on the data rate sqlite could be exactly the correct way to do this. The entire database is locked for each write so you aren't going to scale to 1000s of simultaneous writes per second. But if you only have a few it is the safest way of assuring you don't overwrite each other.","Q_Score":9,"Tags":"python,multithreading,sqlite","A_Id":524955,"CreationDate":"2009-02-07T23:18:00.000","Title":"Python, SQLite and threading","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm working on an application that will gather data through HTTP from several places, cache the data locally and then serve it through HTTP.\nSo I was looking at the following. My application will first create several threads that will gather data at a specified interval and cache that data locally into a SQLite database.   \nThen in the main thread start a CherryPy application that will query that SQLite database and serve the data.\nMy problem is: how do I handle connections to the SQLite database from my threads and from the CherryPy application?\nIf I'd do a connection per thread to the database will I also be able to create\/use an in memory database?","AnswerCount":6,"Available Count":4,"Score":0.0,"is_accepted":false,"ViewCount":13542,"Q_Id":524797,"Users Score":0,"Answer":"Depending on the application the DB could be a real overhead.  If we are talking about volatile data, maybe you could skip the communication via DB completely and share the data between the data gathering process and the data serving process(es) via IPC.  This is not an option if the data has to be persisted, of course.","Q_Score":9,"Tags":"python,multithreading,sqlite","A_Id":524937,"CreationDate":"2009-02-07T23:18:00.000","Title":"Python, SQLite and threading","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm working on an application that will gather data through HTTP from several places, cache the data locally and then serve it through HTTP.\nSo I was looking at the following. My application will first create several threads that will gather data at a specified interval and cache that data locally into a SQLite database.   \nThen in the main thread start a CherryPy application that will query that SQLite database and serve the data.\nMy problem is: how do I handle connections to the SQLite database from my threads and from the CherryPy application?\nIf I'd do a connection per thread to the database will I also be able to create\/use an in memory database?","AnswerCount":6,"Available Count":4,"Score":1.2,"is_accepted":true,"ViewCount":13542,"Q_Id":524797,"Users Score":8,"Answer":"Short answer: Don't use Sqlite3 in a threaded application.\nSqlite3 databases scale well for size, but rather terribly for concurrency. You will be plagued with \"Database is locked\" errors.\nIf you do, you will need a connection per thread, and you have to ensure that these connections clean up after themselves. This is traditionally handled using thread-local sessions, and is performed rather well (for example) using SQLAlchemy's ScopedSession. I would use this if I were you, even if you aren't using the SQLAlchemy ORM features.","Q_Score":9,"Tags":"python,multithreading,sqlite","A_Id":524806,"CreationDate":"2009-02-07T23:18:00.000","Title":"Python, SQLite and threading","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm working on an application that will gather data through HTTP from several places, cache the data locally and then serve it through HTTP.\nSo I was looking at the following. My application will first create several threads that will gather data at a specified interval and cache that data locally into a SQLite database.   \nThen in the main thread start a CherryPy application that will query that SQLite database and serve the data.\nMy problem is: how do I handle connections to the SQLite database from my threads and from the CherryPy application?\nIf I'd do a connection per thread to the database will I also be able to create\/use an in memory database?","AnswerCount":6,"Available Count":4,"Score":0.0333209931,"is_accepted":false,"ViewCount":13542,"Q_Id":524797,"Users Score":1,"Answer":"\"...create several threads that will gather data at a specified interval and cache that data locally into a sqlite database.\nThen in the main thread start a CherryPy app that will query that sqlite db and serve the data.\"\nDon't waste a lot of time on threads.  The things you're describing are simply OS processes.  Just start ordinary processes to do gathering and run Cherry Py.\nYou have no real use for concurrent threads in a single process for this. Gathering data at a specified interval -- when done with simple OS processes -- can be scheduled by the OS very simply.  Cron, for example, does a great job of this.\nA CherryPy App, also, is an OS process, not a single thread of some larger process.\nJust use processes -- threads won't help you.","Q_Score":9,"Tags":"python,multithreading,sqlite","A_Id":524901,"CreationDate":"2009-02-07T23:18:00.000","Title":"Python, SQLite and threading","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I get \"database table is locked\" error in my sqlite3 db. My script is single threaded, no other app is using the program (i did have it open once in \"SQLite Database Browser.exe\"). I copied the file, del the original (success) and renamed the copy so i know no process is locking it yet when i run my script everything in table B cannot be written to and it looks like table A is fine. Whats happening?\n-edit-\nI fixed it but unsure how. I notice the code not doing the correct things (i copied the wrong field) and after fixing it up and cleaning it, it magically started working again.\n-edit2-\nSomeone else posted so i might as well update. I think the problem was i was trying to do a statement with a command\/cursor in use.","AnswerCount":4,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":5791,"Q_Id":531711,"Users Score":0,"Answer":"I've also seen this error when the db file is on an NFS mounted file system.","Q_Score":3,"Tags":"python,sqlite,locking","A_Id":6345495,"CreationDate":"2009-02-10T09:50:00.000","Title":"python, sqlite error? db is locked? but it isnt?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"All I want to do is serialize and unserialize tuples of strings or ints.\nI looked at pickle.dumps() but the byte overhead is significant. Basically it looks like it takes up about 4x as much space as it needs to. Besides, all I need is basic types and have no need to serialize objects.\nmarshal is a little better in terms of space but the result is full of nasty \\x00 bytes. Ideally I would like the result to be human readable.\nI thought of just using repr() and eval(), but is there a simple way I could accomplish this without using eval()?\nThis is getting stored in a db, not a file. Byte overhead matters because it could make the difference between requiring a TEXT column versus a varchar, and generally data compactness affects all areas of db performance.","AnswerCount":7,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":2674,"Q_Id":532934,"Users Score":0,"Answer":"\"the byte overhead is significant\"\nWhy does this matter?  It does the job.  If you're running low on disk space, I'd be glad to sell you a 1Tb for $500.  \nHave you run it?  Is performance a problem?  Can you demonstrate that the performance of serialization is the problem?\n\"I thought of just using repr() and eval(), but is there a simple way I could accomplish this without using eval()?\"\nNothing simpler than repr and eval.\nWhat's wrong with eval?\nIs is the \"someone could insert malicious code into the file where I serialized my lists\" issue?\nWho -- specifically -- is going to find and edit this file to put in malicious code?  Anything you do to secure this (i.e., encryption) removes \"simple\" from it.","Q_Score":7,"Tags":"python,serialization,pickle","A_Id":532989,"CreationDate":"2009-02-10T16:03:00.000","Title":"Lightweight pickle for basic types in python?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I want to fetch data from a mysql database using sqlalchemy and use the data in a different class.. Basically I fetch a row at a time, use the data, fetch another row, use the data and so on.. I am running into some problem doing this.. \nBasically, how do I output data a row at a time from mysql data?.. I have looked into all tutorials but they are not helping much.","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":563,"Q_Id":536051,"Users Score":1,"Answer":"Exactly what problems are you running into?\nYou can simply iterate over the ResultProxy object:\n\nfor row in conn_or_sess_or_engine.execute(selectable_obj_or_SQLstring):\n   do_something_with(row)","Q_Score":0,"Tags":"python,mysql,sqlalchemy","A_Id":536269,"CreationDate":"2009-02-11T09:19:00.000","Title":"Outputting data a row at a time from mysql using sqlalchemy","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have some software that is heavily dependent on MySQL, and is written in python without any class definitions. For performance reasons, and because the database is really just being used to store and retrieve large amounts of data, I'd like to convert this to an object-oriented python script that does not use the database at all.\nSo my plan is to export the database tables to a set of files (not many -- it's a pretty simple database; it's big in that it has a lot of rows, but only a few tables, each of which has just two or three columns).\nThen I plan to read the data in, and have a set of functions which provide access to and operations on the data.\nMy question is this:\nis there a preferred way to convert a set of database tables to classes and objects? For example, if I have a table which contains fruit, where each fruit has an id and a name, would I have a \"CollectionOfFruit\" class which contains a list of \"Fruit\" objects, or would I just have a \"CollectionOfFruit\" class which contains a list of tuples? Or would I just have a list of Fruit objects?\nI don't want to add any extra frameworks, because I want this code to be easy to transfer to different machines. So I'm really just looking for general advice on how to represent data that might more naturally be stored in database tables, in objects in Python.\nAlternatively, is there a good book I should read that would point me in the right direction on this?","AnswerCount":8,"Available Count":5,"Score":0.024994793,"is_accepted":false,"ViewCount":330,"Q_Id":557199,"Users Score":1,"Answer":"Here are a couple points for you to consider.  If your data is large reading it all into memory may be wasteful.  If you need random access and not just sequential access to your data then you'll either have to scan the at most the entire file each time or read that table into an indexed memory structure like a dictionary.  A list will still require some kind of scan (straight iteration or binary search if sorted).  With that said, if you don't require some of the features of a DB then don't use one but if you just think MySQL is too heavy then +1 on the Sqlite suggestion from earlier.  It gives you most of the features you'd want while using a database without the concurrency overhead.","Q_Score":0,"Tags":"python,object","A_Id":558822,"CreationDate":"2009-02-17T14:56:00.000","Title":"Converting a database-driven (non-OO) python script into a non-database driven, OO-script","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have some software that is heavily dependent on MySQL, and is written in python without any class definitions. For performance reasons, and because the database is really just being used to store and retrieve large amounts of data, I'd like to convert this to an object-oriented python script that does not use the database at all.\nSo my plan is to export the database tables to a set of files (not many -- it's a pretty simple database; it's big in that it has a lot of rows, but only a few tables, each of which has just two or three columns).\nThen I plan to read the data in, and have a set of functions which provide access to and operations on the data.\nMy question is this:\nis there a preferred way to convert a set of database tables to classes and objects? For example, if I have a table which contains fruit, where each fruit has an id and a name, would I have a \"CollectionOfFruit\" class which contains a list of \"Fruit\" objects, or would I just have a \"CollectionOfFruit\" class which contains a list of tuples? Or would I just have a list of Fruit objects?\nI don't want to add any extra frameworks, because I want this code to be easy to transfer to different machines. So I'm really just looking for general advice on how to represent data that might more naturally be stored in database tables, in objects in Python.\nAlternatively, is there a good book I should read that would point me in the right direction on this?","AnswerCount":8,"Available Count":5,"Score":1.2,"is_accepted":true,"ViewCount":330,"Q_Id":557199,"Users Score":5,"Answer":"If the data is a natural fit for database tables (\"rectangular data\"), why not convert it to sqlite?  It's portable -- just one file to move the db around, and sqlite is available anywhere you have python (2.5 and above anyway).","Q_Score":0,"Tags":"python,object","A_Id":557473,"CreationDate":"2009-02-17T14:56:00.000","Title":"Converting a database-driven (non-OO) python script into a non-database driven, OO-script","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have some software that is heavily dependent on MySQL, and is written in python without any class definitions. For performance reasons, and because the database is really just being used to store and retrieve large amounts of data, I'd like to convert this to an object-oriented python script that does not use the database at all.\nSo my plan is to export the database tables to a set of files (not many -- it's a pretty simple database; it's big in that it has a lot of rows, but only a few tables, each of which has just two or three columns).\nThen I plan to read the data in, and have a set of functions which provide access to and operations on the data.\nMy question is this:\nis there a preferred way to convert a set of database tables to classes and objects? For example, if I have a table which contains fruit, where each fruit has an id and a name, would I have a \"CollectionOfFruit\" class which contains a list of \"Fruit\" objects, or would I just have a \"CollectionOfFruit\" class which contains a list of tuples? Or would I just have a list of Fruit objects?\nI don't want to add any extra frameworks, because I want this code to be easy to transfer to different machines. So I'm really just looking for general advice on how to represent data that might more naturally be stored in database tables, in objects in Python.\nAlternatively, is there a good book I should read that would point me in the right direction on this?","AnswerCount":8,"Available Count":5,"Score":0.024994793,"is_accepted":false,"ViewCount":330,"Q_Id":557199,"Users Score":1,"Answer":"you could have a fruit class with id and name instance variables. and a function to read\/write the information from a file, and maybe a class variable to keep track of the number of fruits (objects) created","Q_Score":0,"Tags":"python,object","A_Id":557279,"CreationDate":"2009-02-17T14:56:00.000","Title":"Converting a database-driven (non-OO) python script into a non-database driven, OO-script","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have some software that is heavily dependent on MySQL, and is written in python without any class definitions. For performance reasons, and because the database is really just being used to store and retrieve large amounts of data, I'd like to convert this to an object-oriented python script that does not use the database at all.\nSo my plan is to export the database tables to a set of files (not many -- it's a pretty simple database; it's big in that it has a lot of rows, but only a few tables, each of which has just two or three columns).\nThen I plan to read the data in, and have a set of functions which provide access to and operations on the data.\nMy question is this:\nis there a preferred way to convert a set of database tables to classes and objects? For example, if I have a table which contains fruit, where each fruit has an id and a name, would I have a \"CollectionOfFruit\" class which contains a list of \"Fruit\" objects, or would I just have a \"CollectionOfFruit\" class which contains a list of tuples? Or would I just have a list of Fruit objects?\nI don't want to add any extra frameworks, because I want this code to be easy to transfer to different machines. So I'm really just looking for general advice on how to represent data that might more naturally be stored in database tables, in objects in Python.\nAlternatively, is there a good book I should read that would point me in the right direction on this?","AnswerCount":8,"Available Count":5,"Score":0.024994793,"is_accepted":false,"ViewCount":330,"Q_Id":557199,"Users Score":1,"Answer":"There's no \"one size fits all\" answer for this -- it'll depend a lot on the data and how it's used in the application. If the data and usage are simple enough you might want to store your fruit in a dict with id as key and the rest of the data as tuples. Or not. It totally depends. If there's a guiding principle out there then it's to extract the underlying requirements of the app and then write code against those requirements.","Q_Score":0,"Tags":"python,object","A_Id":557241,"CreationDate":"2009-02-17T14:56:00.000","Title":"Converting a database-driven (non-OO) python script into a non-database driven, OO-script","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have some software that is heavily dependent on MySQL, and is written in python without any class definitions. For performance reasons, and because the database is really just being used to store and retrieve large amounts of data, I'd like to convert this to an object-oriented python script that does not use the database at all.\nSo my plan is to export the database tables to a set of files (not many -- it's a pretty simple database; it's big in that it has a lot of rows, but only a few tables, each of which has just two or three columns).\nThen I plan to read the data in, and have a set of functions which provide access to and operations on the data.\nMy question is this:\nis there a preferred way to convert a set of database tables to classes and objects? For example, if I have a table which contains fruit, where each fruit has an id and a name, would I have a \"CollectionOfFruit\" class which contains a list of \"Fruit\" objects, or would I just have a \"CollectionOfFruit\" class which contains a list of tuples? Or would I just have a list of Fruit objects?\nI don't want to add any extra frameworks, because I want this code to be easy to transfer to different machines. So I'm really just looking for general advice on how to represent data that might more naturally be stored in database tables, in objects in Python.\nAlternatively, is there a good book I should read that would point me in the right direction on this?","AnswerCount":8,"Available Count":5,"Score":0.049958375,"is_accepted":false,"ViewCount":330,"Q_Id":557199,"Users Score":2,"Answer":"Generally you want your Objects to absolutely match your \"real world entities\".\nSince you're starting from a database, it's not always the case that the database has any real-world fidelity, either.  Some database designs are simply awful.\nIf your database has reasonable models for Fruit, that's where you start.  Get that right first.\nA \"collection\" may -- or may not -- be an artificial construct that's part of the solution algorithm, not really a proper part of the problem.  Usually collections are part of the problem, and you should design those classes, also.\nOther times, however, the collection is an artifact of having used a database, and a simple Python list is all you need.\nStill other times, the collection is actually a proper mapping from some unique key value to an entity, in which case, it's a Python dictionary.\nAnd sometimes, the collection is a proper mapping from some non-unique key value to some collection of entities, in which case it's a Python collections.defaultdict(list).\nStart with the fundamental, real-world-like entities.  Those get class definitions.\nCollections may use built-in Python collections or may require their own classes.","Q_Score":0,"Tags":"python,object","A_Id":557291,"CreationDate":"2009-02-17T14:56:00.000","Title":"Converting a database-driven (non-OO) python script into a non-database driven, OO-script","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I want to experiment\/play around with non-relational databases, it'd be best if the solution was:\n\nportable, meaning it doesn't require an installation. ideally just copy-pasting the directory to someplace would make it work. I don't mind if it requires editing some configuration files or running a configuration tool for first time usage.\naccessible from python\nworks on both windows and linux\n\nWhat can you recommend for me?\nEssentially, I would like to be able to install this system on a shared linux server where I have little user privileges.","AnswerCount":9,"Available Count":1,"Score":0.0886555158,"is_accepted":false,"ViewCount":3510,"Q_Id":575172,"Users Score":4,"Answer":"If you're used to thinking a relational database has to be huge and heavy like PostgreSQL or MySQL, then you'll be pleasantly surprised by SQLite.\nIt is relational, very small, uses a single file, has Python bindings, requires no extra priviledges, and works on Linux, Windows, and many other platforms.","Q_Score":2,"Tags":"python,non-relational-database,portable-database","A_Id":575197,"CreationDate":"2009-02-22T16:31:00.000","Title":"portable non-relational database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I don't expect to need much more than basic CRUD type functionality. I know that SQLAlchemy is more flexible, but the syntax etc of sqlobject just seem to be a bit easier to get up and going with.","AnswerCount":3,"Available Count":1,"Score":1.0,"is_accepted":false,"ViewCount":3351,"Q_Id":592332,"Users Score":9,"Answer":"I think SQLObject is more pythonic\/simpler, so if it works for you, then stick with it.\nSQLAlchemy takes a little more to learn, but can do more advanced things if you need that.","Q_Score":14,"Tags":"python,orm,sqlalchemy,sqlobject","A_Id":592348,"CreationDate":"2009-02-26T20:37:00.000","Title":"Any reasons not to use SQLObject over SQLAlchemy?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am working on ajax-game. The abstract: 2+ gamers(browsers) change a variable which is saved to DB through json. All gamers are synchronized by javascript-timer+json - periodically reading that variable from DB. \nIn general, all changes are stored in DB as history, but I want the recent change duplicated in memory. \nSo the problem is: i want one variable to be stored in memory instead of DB.","AnswerCount":4,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":127,"Q_Id":602030,"Users Score":0,"Answer":"You'd either have to use a cache, or fetch the most recent change on each request (since you can't persist objects between requests in-memory).\nFrom what you describe, it sounds as if it's being hit fairly frequently, so the cache is probably the way to go.","Q_Score":0,"Tags":"python,django","A_Id":603637,"CreationDate":"2009-03-02T11:46:00.000","Title":"Store last created model's row in memory","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am writing a Python (2.5) GUI Application that does the following:\n\nImports from Access to an Sqlite database \nSaves ui form settings to an Sqlite database\n\nCurrently I am using pywin32 to read Access, and pysqlite2\/dbapi2 to read\/write Sqlite.\nHowever, certain Qt objects don't automatically cast to Python or Sqlite equivalents when updating the Sqlite database. For example, a QDate, QDateTime, QString and others raise an error. Currently I am maintaining conversion functions.\nI investigated using QSql, which appears to overcome the casting problem. In addition, it is able to connect to both Access and Sqlite. These two benefits would appear to allow me to refactor my code to use less modules and not maintain my own conversion functions.\nWhat I am looking for is a list of important side-effects, performance gains\/losses, functionality gains\/losses that any of the SO community has experienced as a result from the switch to QSql.\nOne functionality loss I have experienced thus far is the inability to use Access functions using the QODBC driver (e.g., 'SELECT LCASE(fieldname) from tablename' fails, as does 'SELECT FORMAT(fieldname, \"General Number\") from tablename')","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":241,"Q_Id":608098,"Users Score":0,"Answer":"When dealing with databases and PyQt UIs, I'll use something similar to model-view-controller model to help organize and simplify the code.  \nView module\n\nuses\/holds any QObjects that are necessary\nfor the UI \ncontain simple    functions\/methods\nfor updating your    QTGui Object, as\nwell as extracting    input from GUI\nobjects\n\nController module\n\nwill perform all DB interactions\nthe more complex code lives here\n\nBy using a MVC, you will not need to rely on the QT Library as much, and you will run into less problems linking QT with Python.\nSo I guess my suggestion is to continue using pysqlite (since that's what you are used to), but refactor your design a little so the only thing dealing with the QT libraries is the UI.  From the description of your GUI, it should be fairly straightforward.","Q_Score":1,"Tags":"python,qt,sqlite,pyqt4,pywin32","A_Id":608262,"CreationDate":"2009-03-03T20:45:00.000","Title":"What will I lose or gain from switching database APIs? (from pywin32 and pysqlite to QSql)","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Using pysqlite how can a user-defined-type be used as a value in a comparison, e. g: \u201c... WHERE columnName > userType\u201d?\nFor example, I've defined a bool type with the requisite registration, converter, etc. Pysqlite\/Sqlite responds as expected for INSERT and SELECT operations (bool 'True' stored as an integer 1 and returned as True).\nBut it fails when the bool is used in either \u201cSELECT * from tasks WHERE display = True\u201d or \u201c... WHERE display = 'True.' \u201c In the first case Sqlite reports an error that there is not a column named True. And in the second case no records are returned. The select works if a 1 is used in place of True. I seem to have the same problem when using pysqlite's own date and timestamp adaptors.\nI can work around this behavior for this and other user-types but that's not as fun. I'd like to know if using a user-defined type in a query is or is not possible so that I don't keep banging my head on this particular wall.\nThank you.","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":671,"Q_Id":609516,"Users Score":0,"Answer":"You probably have to cast it to the correct type.  Try \"SELECT * FROM tasks WHERE (display = CAST ('True' AS bool))\".","Q_Score":1,"Tags":"python,sqlite,pysqlite","A_Id":610761,"CreationDate":"2009-03-04T07:08:00.000","Title":"pysqlite user types in select statement","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I often need to execute custom sql queries in django, and manually converting query results into objects every time is kinda painful. I wonder how fellow Slackers deal with this. Maybe someone had written some kind of a library to help dealing with custom SQL in Django?","AnswerCount":3,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":3263,"Q_Id":619384,"Users Score":3,"Answer":"Since the issue is \"manually converting query results into objects,\" the simplest solution is often to see if your custom SQL can fit into an ORM .extra() call rather than being a pure-SQL query.  Often it can, and then you let the ORM do all the work of building up objects as usual.","Q_Score":2,"Tags":"python,django,orm","A_Id":620117,"CreationDate":"2009-03-06T16:11:00.000","Title":"Tools to ease executing raw SQL with Django ORM","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"When I have created a table with an auto-incrementing primary key, is there a way to obtain what the primary key would be (that is, do something like reserve the primary key) without actually committing?\nI would like to place two operations inside a transaction however one of the operations will depend on what primary key was assigned in the previous operation.","AnswerCount":2,"Available Count":1,"Score":-0.2913126125,"is_accepted":false,"ViewCount":19996,"Q_Id":620610,"Users Score":-3,"Answer":"You can use multiple transactions and manage it within scope.","Q_Score":53,"Tags":"python,sql,sqlalchemy","A_Id":620784,"CreationDate":"2009-03-06T22:07:00.000","Title":"SQLAlchemy Obtain Primary Key With Autoincrement Before Commit","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Our Python CMS stores some date values in a generic \"attribute\" table's varchar column.  Some of these dates are later moved into a table with an actual date column.  If the CMS user entered an invalid date, it doesn't get caught until the migration, when the query fails with an \"Invalid string date\" error.\nHow can I use Python to make sure that all dates put into our CMS are valid Oracle string date representations?","AnswerCount":3,"Available Count":2,"Score":0.0665680765,"is_accepted":false,"ViewCount":902,"Q_Id":639949,"Users Score":1,"Answer":"The format of a date string that Oracle recognizes as a date is a configurable property of the database and as such it's considered bad form to rely on implicit conversions of strings to dates.\nTypically Oracle dates format to 'DD-MON-YYYY' but you can't always rely on it being set that way.\nPersonally I would have the CMS write to this \"attribute\" table in a standard format like 'YYYY-MM-DD', and then whichever job moves that to a DATE column can explicitly cast the value with to_date( value, 'YYYY-MM-DD' ) and you won't have any problems.","Q_Score":1,"Tags":"python,oracle,validation","A_Id":640115,"CreationDate":"2009-03-12T18:41:00.000","Title":"Validating Oracle dates in Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Our Python CMS stores some date values in a generic \"attribute\" table's varchar column.  Some of these dates are later moved into a table with an actual date column.  If the CMS user entered an invalid date, it doesn't get caught until the migration, when the query fails with an \"Invalid string date\" error.\nHow can I use Python to make sure that all dates put into our CMS are valid Oracle string date representations?","AnswerCount":3,"Available Count":2,"Score":-0.0665680765,"is_accepted":false,"ViewCount":902,"Q_Id":639949,"Users Score":-1,"Answer":"Validate as early as possible. Why don't you store dates as dates in your Python CMS? \nIt is difficult to know what date a string like '03-04-2008' is. Is it 3 april 2008 or 4 march 2008? An American will say 4 march 2008 but a Dutch person will say 3 april 2008.","Q_Score":1,"Tags":"python,oracle,validation","A_Id":640153,"CreationDate":"2009-03-12T18:41:00.000","Title":"Validating Oracle dates in Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am finding it difficult to use MySQL with Python in my windows system.\nI am currently using Python 2.6. I have tried to compile MySQL-python-1.2.3b1 (which is supposed to work for Python 2.6 ?) source code using the provided setup scripts. The setup script runs and it doesn't report any error but it doesn't generate _mysql module. \nI have also tried setting up MySQL for Python 2.5 with out success. The problem with using 2.5 is that Python 2.5 is compiled with visual studio 2003 (I installed it using the provided binaries). I have visual studio 2005 on my windows system. Hence setuptools fails to generate _mysql module.\nAny help ?","AnswerCount":16,"Available Count":1,"Score":0.012499349,"is_accepted":false,"ViewCount":110355,"Q_Id":645943,"Users Score":1,"Answer":"Because I am running python in a (pylons\/pyramid) virtualenv, I could not run the binary installers (helpfully) linked to previously. \nI had problems following the steps with Willie's answer, but I determined that the problem is (probably) that I am running windows 7 x64 install, which puts the registry key for mysql in a slightly different location, specifically in my case (note: I am running version 5.5) in: \"HKEY_LOCAL_MACHINE\\SOFTWARE\\Wow6432Node\\MySQL AB\\MySQL Server 5.5\".\nHOWEVER, \"HKEY_LOCAL_MACHINE\\\" cannot be included in the path or it will fail.\nAlso, I had to do a restart between steps 3 and 4.\nAfter working through all of this, IMO it would have been smarter to run the entire python dev environment from cygwin.","Q_Score":102,"Tags":"python,mysql,windows","A_Id":5294670,"CreationDate":"2009-03-14T13:53:00.000","Title":"Integrating MySQL with Python in Windows","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"OMG!\nWhat an apparent problem... my django based scripts have locked my sqlite db...\nDoes anyone know how to fix?","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":4579,"Q_Id":652750,"Users Score":6,"Answer":"Your database is locked because you have a transaction running somewhere.  \nStop all your Django apps.  If necessary, reboot.\nIt's also remotely possible that you crashed a SQLite client in the middle of a transaction and the file lock was left in place.","Q_Score":1,"Tags":"python,django","A_Id":652758,"CreationDate":"2009-03-17T01:33:00.000","Title":"How to unlock an sqlite3 db?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I've added new models and pushed to our staging server, run syncdb to create their tables, and it locks up. It gets as far as 'Create table photos_photousertag' and postgres output shows the notice for creation of 'photos_photousertag_id_seq', but otherwise i get nothing on either said. I can't ctrl+c the syncdb process and I have no indication of what route to take from here. Has anyone else ran into this?","AnswerCount":3,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":985,"Q_Id":674030,"Users Score":0,"Answer":"Strange here too, but simply restarting the PostgreSQL service (or server) solved it. I'd tried manually pasting the table creation code in psql too, but that wasn't solving it either (well, no way it could if it was a lock thing) - so I just used the restart:\n\nsystemctl restart postgresql.service \n\nthat's on my Suse box.\nAm not sure whether reloading the service\/server might lift existing table locks too?","Q_Score":3,"Tags":"python,django,django-syncdb","A_Id":21254637,"CreationDate":"2009-03-23T16:16:00.000","Title":"Django syncdb locking up on table creation","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I've added new models and pushed to our staging server, run syncdb to create their tables, and it locks up. It gets as far as 'Create table photos_photousertag' and postgres output shows the notice for creation of 'photos_photousertag_id_seq', but otherwise i get nothing on either said. I can't ctrl+c the syncdb process and I have no indication of what route to take from here. Has anyone else ran into this?","AnswerCount":3,"Available Count":3,"Score":0.0665680765,"is_accepted":false,"ViewCount":985,"Q_Id":674030,"Users Score":1,"Answer":"I just experienced this as well, and it turned out to just be a plain old lock on that particular table, unrelated to Django. Once that cleared the sync went through just fine.\nTry querying the table that the sync is getting stuck on and make sure that's working correctly first.","Q_Score":3,"Tags":"python,django,django-syncdb","A_Id":10438955,"CreationDate":"2009-03-23T16:16:00.000","Title":"Django syncdb locking up on table creation","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I've added new models and pushed to our staging server, run syncdb to create their tables, and it locks up. It gets as far as 'Create table photos_photousertag' and postgres output shows the notice for creation of 'photos_photousertag_id_seq', but otherwise i get nothing on either said. I can't ctrl+c the syncdb process and I have no indication of what route to take from here. Has anyone else ran into this?","AnswerCount":3,"Available Count":3,"Score":0.0665680765,"is_accepted":false,"ViewCount":985,"Q_Id":674030,"Users Score":1,"Answer":"We use postgres, and while we've not run into this particular issue, there are some steps you may find helpful in debugging:\na. What version of postgres and psycopg2 are you using? For that matter, what version of django?\nb. Try running the syncdb command with the \"--verbosity=2\" option to show all output.\nc. Find the SQL that django is generating by running the \"manage.py sql \" command. Run the CREATE TABLE statements for your new models in the postgres shell and see what develops.\nd. Turn the error logging, statement logging, and server status logging on postgres way up to see if you can catch any particular messages.\nIn the past, we've usually found that either option b or option c points out the problem.","Q_Score":3,"Tags":"python,django,django-syncdb","A_Id":674105,"CreationDate":"2009-03-23T16:16:00.000","Title":"Django syncdb locking up on table creation","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Let's say I have two or more processes dealing with an SQLite database - a \"player\" process and many \"editor\" processes. \nThe \"player\" process reads the database and updates a view - in my case it would be a waveform being mixed to the soundcard depending on events stored in the database.\nAn \"editor\" process is any editor for that database: it changes the database constantly.\nNow I want the player to reflect the editing changes quickly.\nI know that SQLite supplies hooks to trace database changes within the same process, but there seems to be little info on how to do this with multiple processes.\nI could poll the database constantly, compare records and trigger events, but that seems to be quite inefficient, especially when the database grows to a large size.\nI am thinking about using a log table and triggers, but I wonder if there is a simpler method.","AnswerCount":8,"Available Count":5,"Score":0.049958375,"is_accepted":false,"ViewCount":15631,"Q_Id":677028,"Users Score":2,"Answer":"Just open a socket between the two processes and have the editor tell all the players about the update.","Q_Score":15,"Tags":"python,sqlite,notifications","A_Id":677042,"CreationDate":"2009-03-24T11:34:00.000","Title":"How do I notify a process of an SQLite database change done in a different process?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Let's say I have two or more processes dealing with an SQLite database - a \"player\" process and many \"editor\" processes. \nThe \"player\" process reads the database and updates a view - in my case it would be a waveform being mixed to the soundcard depending on events stored in the database.\nAn \"editor\" process is any editor for that database: it changes the database constantly.\nNow I want the player to reflect the editing changes quickly.\nI know that SQLite supplies hooks to trace database changes within the same process, but there seems to be little info on how to do this with multiple processes.\nI could poll the database constantly, compare records and trigger events, but that seems to be quite inefficient, especially when the database grows to a large size.\nI am thinking about using a log table and triggers, but I wonder if there is a simpler method.","AnswerCount":8,"Available Count":5,"Score":0.049958375,"is_accepted":false,"ViewCount":15631,"Q_Id":677028,"Users Score":2,"Answer":"I think in that case, I would make a process to manage the database read\/writes.\nEach editor that want to make some modifications to the database makes a call to this proccess, be it through IPC or network, or whatever method.\nThis process can then notify the player of a change in the database. The player, when he wants to retrieve some data should make a request of the data it wants to the process managing the database. (Or the db process tells it what it needs, when it notifies of a change, so no request from the player needed)\nDoing this will have the advantage of having only one process accessing the SQLite DB, so no locking or concurrency issues on the database.","Q_Score":15,"Tags":"python,sqlite,notifications","A_Id":677215,"CreationDate":"2009-03-24T11:34:00.000","Title":"How do I notify a process of an SQLite database change done in a different process?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Let's say I have two or more processes dealing with an SQLite database - a \"player\" process and many \"editor\" processes. \nThe \"player\" process reads the database and updates a view - in my case it would be a waveform being mixed to the soundcard depending on events stored in the database.\nAn \"editor\" process is any editor for that database: it changes the database constantly.\nNow I want the player to reflect the editing changes quickly.\nI know that SQLite supplies hooks to trace database changes within the same process, but there seems to be little info on how to do this with multiple processes.\nI could poll the database constantly, compare records and trigger events, but that seems to be quite inefficient, especially when the database grows to a large size.\nI am thinking about using a log table and triggers, but I wonder if there is a simpler method.","AnswerCount":8,"Available Count":5,"Score":0.049958375,"is_accepted":false,"ViewCount":15631,"Q_Id":677028,"Users Score":2,"Answer":"If it's on the same machine, the simplest way would be to have named pipe, \"player\" with blocking read() and \"editors\" putting a token in pipe whenever they modify DB.","Q_Score":15,"Tags":"python,sqlite,notifications","A_Id":677087,"CreationDate":"2009-03-24T11:34:00.000","Title":"How do I notify a process of an SQLite database change done in a different process?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Let's say I have two or more processes dealing with an SQLite database - a \"player\" process and many \"editor\" processes. \nThe \"player\" process reads the database and updates a view - in my case it would be a waveform being mixed to the soundcard depending on events stored in the database.\nAn \"editor\" process is any editor for that database: it changes the database constantly.\nNow I want the player to reflect the editing changes quickly.\nI know that SQLite supplies hooks to trace database changes within the same process, but there seems to be little info on how to do this with multiple processes.\nI could poll the database constantly, compare records and trigger events, but that seems to be quite inefficient, especially when the database grows to a large size.\nI am thinking about using a log table and triggers, but I wonder if there is a simpler method.","AnswerCount":8,"Available Count":5,"Score":1.2,"is_accepted":true,"ViewCount":15631,"Q_Id":677028,"Users Score":4,"Answer":"A relational database is not your best first choice for this.\nWhy?\nYou want all of your editors to pass changes to your player.  \nYour player is -- effectively -- a server for all those editors.  Your player needs multiple open connections.  It must listen to all those connections for changes.  It must display those changes.\nIf the changes are really large, you can move to a hybrid solution where the editors persist the changes and notify the player.  \nEither way, the editors must notify they player that they have a change.  It's much, much simpler than the player trying to discover changes in a database.\n\nA better design is a server which accepts messages from the editors, persists them, and notifies the player.  This server is neither editor nor player, but merely a broker that assures that all the messages are handled.  It accepts connections from editors and players.  It manages the database.\nThere are two implementations.  Server IS the player.  Server is separate from the player.  The design of server doesn't change -- only the protocol.  When server is the player, then server calls the player objects directly.  When server is separate from the player, then the server writes to the player's socket.\nWhen the player is part of the server, player objects are invoked directly when a message is received from an editor.  When the player is separate, a small reader collects the messages from a socket and calls the player objects.\nThe player connects to the server and then waits for a stream of information.  This can either be input from the editors or references to data that the server persisted in the database.\nIf your message traffic is small enough so that network latency is not a problem, editor sends all the data to the server\/player.  If message traffic is too large, then the editor  writes to a database and sends a message with just a database FK to the server\/player.  \n\nPlease clarify \"If the editor crashes while notifying, the player is permanently messed up\" in your question.\nThis sounds like a poor design for the player service.  It can't be \"permanently messed up\" unless it's not getting state from the various editors.  If it's getting state from the editors (but attempting to mirror that state, for example) then you should consider a design where the player simply gets state from the editor and cannot get \"permanently messed up\".","Q_Score":15,"Tags":"python,sqlite,notifications","A_Id":677085,"CreationDate":"2009-03-24T11:34:00.000","Title":"How do I notify a process of an SQLite database change done in a different process?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Let's say I have two or more processes dealing with an SQLite database - a \"player\" process and many \"editor\" processes. \nThe \"player\" process reads the database and updates a view - in my case it would be a waveform being mixed to the soundcard depending on events stored in the database.\nAn \"editor\" process is any editor for that database: it changes the database constantly.\nNow I want the player to reflect the editing changes quickly.\nI know that SQLite supplies hooks to trace database changes within the same process, but there seems to be little info on how to do this with multiple processes.\nI could poll the database constantly, compare records and trigger events, but that seems to be quite inefficient, especially when the database grows to a large size.\nI am thinking about using a log table and triggers, but I wonder if there is a simpler method.","AnswerCount":8,"Available Count":5,"Score":0.024994793,"is_accepted":false,"ViewCount":15631,"Q_Id":677028,"Users Score":1,"Answer":"How many editor processes (why processes?), and how often do you expect updates? This doesn't sound like a good design, especially not considering sqlite really isn't too happy about multiple concurrent accesses to the database.\nIf multiple processes makes sense and you want persistence, it would probably be smarter to have the editors notify your player via sockets, pipes, shared memory or the like and then have the player (aka server process) do the persisting.","Q_Score":15,"Tags":"python,sqlite,notifications","A_Id":677169,"CreationDate":"2009-03-24T11:34:00.000","Title":"How do I notify a process of an SQLite database change done in a different process?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"does anybody know what is the equivalent to SQL \"INSERT OR REPLACE\" clause in SQLAlchemy and its SQL expression language?\nMany thanks -- honzas","AnswerCount":4,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":20634,"Q_Id":708762,"Users Score":5,"Answer":"I don't think (correct me if I'm wrong) INSERT OR REPLACE is in any of the SQL standards; it's an SQLite-specific thing.  There is MERGE, but that isn't supported by all dialects either.  So it's not available in SQLAlchemy's general dialect.\nThe cleanest solution is to use Session, as suggested by M. Utku.  You could also use SAVEPOINTs to save, try: an insert, except IntegrityError: then rollback and do an update instead.  A third solution is to write your INSERT with an OUTER JOIN and a WHERE clause that filters on the rows with nulls.","Q_Score":13,"Tags":"python,sqlalchemy","A_Id":709452,"CreationDate":"2009-04-02T08:05:00.000","Title":"SQLAlchemy - INSERT OR REPLACE equivalent","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Yes, this is as stupid a situation as it sounds like.  Due to some extremely annoying hosting restrictions and unresponsive tech support, I have to use a CSV file as a database.  \nWhile I can use MySQL with PHP, I can't use it with the Python backend of my program because of install issues with the host.  I can't use SQLite with PHP because of more install issues, but can use it as it's a Python builtin.\nAnyways, now, the question: is it possible to update values SQL-style in a CSV database? Or should I keep on calling the help desk?","AnswerCount":12,"Available Count":9,"Score":0.0,"is_accepted":false,"ViewCount":2433,"Q_Id":712510,"Users Score":0,"Answer":"Disagreeing with the noble colleagues, I often use DBD::CSV from Perl.  There are good reasons to do it.  Foremost is data update made simple using a spreadsheet. As a bonus,  since I am using SQL queries, the application can be easily upgraded to a real  database engine. Bear in mind these were extremely small database in a single user application.  \nSo rephrasing the question: Is there a python module equivalent to Perl's DBD:CSV","Q_Score":4,"Tags":"python,csv","A_Id":1396578,"CreationDate":"2009-04-03T04:02:00.000","Title":"Using CSV as a mutable database?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Yes, this is as stupid a situation as it sounds like.  Due to some extremely annoying hosting restrictions and unresponsive tech support, I have to use a CSV file as a database.  \nWhile I can use MySQL with PHP, I can't use it with the Python backend of my program because of install issues with the host.  I can't use SQLite with PHP because of more install issues, but can use it as it's a Python builtin.\nAnyways, now, the question: is it possible to update values SQL-style in a CSV database? Or should I keep on calling the help desk?","AnswerCount":12,"Available Count":9,"Score":0.0,"is_accepted":false,"ViewCount":2433,"Q_Id":712510,"Users Score":0,"Answer":"What about postgresql? I've found that quite nice to work with, and python supports it well.\nBut I really would look for another provider unless it's really not an option.","Q_Score":4,"Tags":"python,csv","A_Id":713531,"CreationDate":"2009-04-03T04:02:00.000","Title":"Using CSV as a mutable database?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Yes, this is as stupid a situation as it sounds like.  Due to some extremely annoying hosting restrictions and unresponsive tech support, I have to use a CSV file as a database.  \nWhile I can use MySQL with PHP, I can't use it with the Python backend of my program because of install issues with the host.  I can't use SQLite with PHP because of more install issues, but can use it as it's a Python builtin.\nAnyways, now, the question: is it possible to update values SQL-style in a CSV database? Or should I keep on calling the help desk?","AnswerCount":12,"Available Count":9,"Score":0.0166651236,"is_accepted":false,"ViewCount":2433,"Q_Id":712510,"Users Score":1,"Answer":"\"Anyways, now, the question: is it possible to update values SQL-style in a CSV database?\"\nTechnically, it's possible.  However, it can be hard.\nIf both PHP and Python are writing the file, you'll need to use OS-level locking to assure that they don't overwrite each other.  Each part of your system will have to lock the file, rewrite it from scratch with all the updates, and unlock the file.\nThis means that PHP and Python must load the entire file into memory before rewriting it.\nThere are a couple of ways to handle the OS locking.\n\nUse the same file and actually use some OS lock module.  Both processes have the file open at all times.\nWrite to a temp file and do a rename.  This means each program must open and read the file for each transaction.  Very safe and reliable.  A little slow.\n\nOr.\nYou can rearchitect it so that only Python writes the file.  The front-end reads the file when it changes, and drops off little transaction files to create a work queue for Python.  In this case, you don't have multiple writers -- you have one reader and one writer -- and life is much, much simpler.","Q_Score":4,"Tags":"python,csv","A_Id":713396,"CreationDate":"2009-04-03T04:02:00.000","Title":"Using CSV as a mutable database?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Yes, this is as stupid a situation as it sounds like.  Due to some extremely annoying hosting restrictions and unresponsive tech support, I have to use a CSV file as a database.  \nWhile I can use MySQL with PHP, I can't use it with the Python backend of my program because of install issues with the host.  I can't use SQLite with PHP because of more install issues, but can use it as it's a Python builtin.\nAnyways, now, the question: is it possible to update values SQL-style in a CSV database? Or should I keep on calling the help desk?","AnswerCount":12,"Available Count":9,"Score":0.0,"is_accepted":false,"ViewCount":2433,"Q_Id":712510,"Users Score":0,"Answer":"I agree.  Tell them that 5 random strangers agree that you being forced into a corner to use CSV is absurd and unacceptable.","Q_Score":4,"Tags":"python,csv","A_Id":712567,"CreationDate":"2009-04-03T04:02:00.000","Title":"Using CSV as a mutable database?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Yes, this is as stupid a situation as it sounds like.  Due to some extremely annoying hosting restrictions and unresponsive tech support, I have to use a CSV file as a database.  \nWhile I can use MySQL with PHP, I can't use it with the Python backend of my program because of install issues with the host.  I can't use SQLite with PHP because of more install issues, but can use it as it's a Python builtin.\nAnyways, now, the question: is it possible to update values SQL-style in a CSV database? Or should I keep on calling the help desk?","AnswerCount":12,"Available Count":9,"Score":0.0166651236,"is_accepted":false,"ViewCount":2433,"Q_Id":712510,"Users Score":1,"Answer":"You can probably used sqlite3 for more real database.  It's hard to imagine hosting that won't allow you to install it as a python module.\nDon't even think of using CSV, your data will be corrupted and lost faster than you say \"s#&t\"","Q_Score":4,"Tags":"python,csv","A_Id":712568,"CreationDate":"2009-04-03T04:02:00.000","Title":"Using CSV as a mutable database?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Yes, this is as stupid a situation as it sounds like.  Due to some extremely annoying hosting restrictions and unresponsive tech support, I have to use a CSV file as a database.  \nWhile I can use MySQL with PHP, I can't use it with the Python backend of my program because of install issues with the host.  I can't use SQLite with PHP because of more install issues, but can use it as it's a Python builtin.\nAnyways, now, the question: is it possible to update values SQL-style in a CSV database? Or should I keep on calling the help desk?","AnswerCount":12,"Available Count":9,"Score":0.0166651236,"is_accepted":false,"ViewCount":2433,"Q_Id":712510,"Users Score":1,"Answer":"I couldn't imagine this ever being a good idea.  The current mess I've inherited writes vital billing information to CSV and updates it after projects are complete.  It runs horribly and thousands of dollars are missed a month.  For the current restrictions that you have, I'd consider finding better hosting.","Q_Score":4,"Tags":"python,csv","A_Id":712522,"CreationDate":"2009-04-03T04:02:00.000","Title":"Using CSV as a mutable database?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Yes, this is as stupid a situation as it sounds like.  Due to some extremely annoying hosting restrictions and unresponsive tech support, I have to use a CSV file as a database.  \nWhile I can use MySQL with PHP, I can't use it with the Python backend of my program because of install issues with the host.  I can't use SQLite with PHP because of more install issues, but can use it as it's a Python builtin.\nAnyways, now, the question: is it possible to update values SQL-style in a CSV database? Or should I keep on calling the help desk?","AnswerCount":12,"Available Count":9,"Score":0.0166651236,"is_accepted":false,"ViewCount":2433,"Q_Id":712510,"Users Score":1,"Answer":"Keep calling on the help desk.\nWhile you can use a CSV as a database, it's generally a bad idea. You would have to implement you own locking, searching, updating, and be very careful with how you write it out to make sure that it isn't erased in case of a power outage or other abnormal shutdown. There will be no transactions, no query language unless you write your own, etc.","Q_Score":4,"Tags":"python,csv","A_Id":712515,"CreationDate":"2009-04-03T04:02:00.000","Title":"Using CSV as a mutable database?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Yes, this is as stupid a situation as it sounds like.  Due to some extremely annoying hosting restrictions and unresponsive tech support, I have to use a CSV file as a database.  \nWhile I can use MySQL with PHP, I can't use it with the Python backend of my program because of install issues with the host.  I can't use SQLite with PHP because of more install issues, but can use it as it's a Python builtin.\nAnyways, now, the question: is it possible to update values SQL-style in a CSV database? Or should I keep on calling the help desk?","AnswerCount":12,"Available Count":9,"Score":0.0,"is_accepted":false,"ViewCount":2433,"Q_Id":712510,"Users Score":0,"Answer":"I'd keep calling help desk. You don't want to use CSV for data if it's relational at all.  It's going to be nightmare.","Q_Score":4,"Tags":"python,csv","A_Id":712512,"CreationDate":"2009-04-03T04:02:00.000","Title":"Using CSV as a mutable database?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Yes, this is as stupid a situation as it sounds like.  Due to some extremely annoying hosting restrictions and unresponsive tech support, I have to use a CSV file as a database.  \nWhile I can use MySQL with PHP, I can't use it with the Python backend of my program because of install issues with the host.  I can't use SQLite with PHP because of more install issues, but can use it as it's a Python builtin.\nAnyways, now, the question: is it possible to update values SQL-style in a CSV database? Or should I keep on calling the help desk?","AnswerCount":12,"Available Count":9,"Score":0.0,"is_accepted":false,"ViewCount":2433,"Q_Id":712510,"Users Score":0,"Answer":"If I understand you correctly: you need to access the same database from both python and php, and you're screwed because you can only use mysql from php, and only sqlite from python?\nCould you further explain this? Maybe you could use xml-rpc or plain http requests with xml\/json\/... to get the php program to communicate with the python program (or the other way around?), so that only one of them directly accesses the db.\nIf this is not the case, I'm not really sure what the problem.","Q_Score":4,"Tags":"python,csv","A_Id":712974,"CreationDate":"2009-04-03T04:02:00.000","Title":"Using CSV as a mutable database?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am trying to do the schedule for the upcoming season for my simulation baseball team.  I have an existing Postgresql database that contains the old schedule.\nThere are 648 rows in the database: 27 weeks of series for 24 teams.  The problem is that the schedule has gotten predictable and allows teams to know in advance about weak parts of their schedule.  What I want to do is take the existing schedule and randomize it.  That way teams are still playing each other the proper number of times but not in the same order as before.\nThere is one rule that has been tripping me up:  each team can only play one home and one road series PER week.  I had been fooling around with SELECT statements based on ORDER BY RANDOM() but I haven't figured out how to make sure a team only has one home and one road series per week.\nNow, I could do this in PHP (which is the language I am most comfortable with) but I am trying to make the shift to Python so I'm not sure how to get this done in Python.  I know that Python doesn't seem to handle two dimensional arrays very well.\nAny help would be greatly appreciated.","AnswerCount":3,"Available Count":2,"Score":0.1325487884,"is_accepted":false,"ViewCount":2359,"Q_Id":719886,"Users Score":2,"Answer":"Have you considered keeping your same \"schedule\", and just shuffling the teams?  Generating a schedule where everyone plays each other the proper number of times is possible, but if you already have such a schedule then it's much easier to just shuffle the teams.\nYou could keep your current table, but replace each team in it with an id (0-23, or A-X, or whatever), then randomly generate into another table where you assign each team to each id (0 = TeamJoe, 1 = TeamBob, etc).  Then when it's time to shuffle again next year, just regenerate that mapping table.\nNot sure if this answers the question the way you want, but is probably what I would go with (and is actually how I do it on my fantasy football website).","Q_Score":0,"Tags":"python,postgresql","A_Id":719913,"CreationDate":"2009-04-05T23:34:00.000","Title":"Help Me Figure Out A Random Scheduling Algorithm using Python and PostgreSQL","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am trying to do the schedule for the upcoming season for my simulation baseball team.  I have an existing Postgresql database that contains the old schedule.\nThere are 648 rows in the database: 27 weeks of series for 24 teams.  The problem is that the schedule has gotten predictable and allows teams to know in advance about weak parts of their schedule.  What I want to do is take the existing schedule and randomize it.  That way teams are still playing each other the proper number of times but not in the same order as before.\nThere is one rule that has been tripping me up:  each team can only play one home and one road series PER week.  I had been fooling around with SELECT statements based on ORDER BY RANDOM() but I haven't figured out how to make sure a team only has one home and one road series per week.\nNow, I could do this in PHP (which is the language I am most comfortable with) but I am trying to make the shift to Python so I'm not sure how to get this done in Python.  I know that Python doesn't seem to handle two dimensional arrays very well.\nAny help would be greatly appreciated.","AnswerCount":3,"Available Count":2,"Score":0.0665680765,"is_accepted":false,"ViewCount":2359,"Q_Id":719886,"Users Score":1,"Answer":"I'm not sure I fully understand the problem, but here is how I would do it:\n1. create a complete list of matches that need to happen\n2. iterate over the weeks, selecting which match needs to happen in this week.\nYou can use Python lists to represent the matches that still need to happen, and, for each week, the matches that are happening in this week.\nIn step 2, selecting a match to happen would work this way:\na. use random.choice to select a random match to happen.\nb. determine which team has a home round for this match, using random.choice([1,2]) (if it could have been a home round for either team)\nc. temporarily remove all matches that get blocked by this selection. a match is blocked if one of its teams has already two matches in the week, or if both teams already have a home match in this week, or if both teams already have a road match in this week.\nd. when there are no available matches anymore for a week, proceed to the next week, readding all the matches that got blocked for the previous week.","Q_Score":0,"Tags":"python,postgresql","A_Id":719909,"CreationDate":"2009-04-05T23:34:00.000","Title":"Help Me Figure Out A Random Scheduling Algorithm using Python and PostgreSQL","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm working with a 20 gig XML file that I would like to import into a SQL database (preferably MySQL, since that is what I am familiar with). This seems like it would be a common task, but after Googling around a bit I haven't been able to figure out how to do it. What is the best way to do this? \nI know this ability is built into MySQL 6.0, but that is not an option right now because it is an alpha development release.\nAlso, if I have to do any scripting I would prefer to use Python because that's what I am most familiar with. \nThanks.","AnswerCount":5,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":12197,"Q_Id":723757,"Users Score":0,"Answer":"It may be a common task, but maybe 20GB isn't as common with MySQL as it is with SQL Server.\nI've done this using SQL Server Integration Services and a bit of custom code. Whether you need either of those depends on what you need to do with 20GB of XML in a database. Is it going to be a single column of a single row of a table? One row per child element?\nSQL Server has an XML datatype if you simply want to store the XML as XML. This type allows you to do queries using XQuery, allows you to create XML indexes over the XML, and allows the XML column to be \"strongly-typed\" by referring it to a set of XML schemas, which you store in the database.","Q_Score":5,"Tags":"python,sql,xml","A_Id":723931,"CreationDate":"2009-04-07T00:39:00.000","Title":"Import XML into SQL database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I've written a web-app in python using SQLite and it runs fine on my server at home (with apache and python 2.5.2). I'm now trying to upload it to my web host and there servers use python 2.2.3 without SQLite.\nAnyone know of a way to use SQLite in python 2.2.3 e.g. a module that I can upload and import? I've tried butchering the module from newer versions of python, but they don't seem to be compatible.\nThanks,\nMike","AnswerCount":4,"Available Count":2,"Score":0.0996679946,"is_accepted":false,"ViewCount":1012,"Q_Id":737511,"Users Score":2,"Answer":"There is no out-of-the-box solution; you either have to backport the SQLlite module from Python 2.5 to Python 2.2 or ask your web hoster to upgrade to the latest Python version. \nPython 2.2 is really ancient! At least for security reasons, they should upgrade (no more security fixes for 2.2 since May 30, 2003!).\nNote that you can install several versions of Python in parallel. Just make sure you use \"\/usr\/bin\/python25\" instead of \"\/usr\/bin\/python\" in your scripts. To make sure all the old stuff is still working, after installing Python 2.5, you just have to fix the two symbolic links \"\/usr\/bin\/python\" and \"\/usr\/lib\/python\" which should now point to 2.5. Bend them back to 2.2 and you're good.","Q_Score":1,"Tags":"python,sql,linux,sqlite,hosting","A_Id":737617,"CreationDate":"2009-04-10T12:40:00.000","Title":"SQLite in Python 2.2.3","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I've written a web-app in python using SQLite and it runs fine on my server at home (with apache and python 2.5.2). I'm now trying to upload it to my web host and there servers use python 2.2.3 without SQLite.\nAnyone know of a way to use SQLite in python 2.2.3 e.g. a module that I can upload and import? I've tried butchering the module from newer versions of python, but they don't seem to be compatible.\nThanks,\nMike","AnswerCount":4,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":1012,"Q_Id":737511,"Users Score":0,"Answer":"In case anyone comes across this question, the reason why neither pysqlite nor APSW are available for Python 2.2 is because Python 2.3 added the simplified GIL API.  Prior to Python 2.3 it required a lot of code to keep track of the GIL.  (The GIL is the lock used by Python to ensure correct behaviour while multi-threading.)\nDoing a backport to 2.2 would require ripping out all the threading code.  Trying to make it also be thread safe under 2.2 would be a nightmare.  There was a reason they introduced the simplified GIL API!\nI am still astonished at just how popular older Python versions are.  APSW for Python 2.3 is still regularly downloaded.","Q_Score":1,"Tags":"python,sql,linux,sqlite,hosting","A_Id":4066757,"CreationDate":"2009-04-10T12:40:00.000","Title":"SQLite in Python 2.2.3","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm trying to use SQLAlchemy to implement a basic users-groups model where users can have multiple groups and groups can have multiple users.\nWhen a group becomes empty, I want the group to be deleted, (along with other things associated with the group.  Fortunately, SQLAlchemy's cascade works fine with these more simple situations).\nThe problem is that cascade='all, delete-orphan' doesn't do exactly what I want; instead of deleting the group when the group becomes empty, it deletes the group when any member leaves the group.\nAdding triggers to the database works fine for deleting a group when it becomes empty, except that triggers seem to bypass SQLAlchemy's cascade processing so things associated with the group don't get deleted.\nWhat is the best way to delete a group when all of its members leave and have this deletion cascade to related entities.\nI understand that I could do this manually by finding every place in my code where a user can leave a group and then doing the same thing as the trigger however, I'm afraid that I would miss places in the code (and I'm lazy).","AnswerCount":4,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":3255,"Q_Id":740630,"Users Score":0,"Answer":"Could you post a sample of your table and mapper set up? It might be easier to spot what is going on.\nWithout seeing the code it is hard to tell, but perhaps there is something wrong with the direction of the relationship?","Q_Score":9,"Tags":"python,sqlalchemy","A_Id":776246,"CreationDate":"2009-04-11T19:07:00.000","Title":"SQLAlchemy many-to-many orphan deletion","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm trying to use SQLAlchemy to implement a basic users-groups model where users can have multiple groups and groups can have multiple users.\nWhen a group becomes empty, I want the group to be deleted, (along with other things associated with the group.  Fortunately, SQLAlchemy's cascade works fine with these more simple situations).\nThe problem is that cascade='all, delete-orphan' doesn't do exactly what I want; instead of deleting the group when the group becomes empty, it deletes the group when any member leaves the group.\nAdding triggers to the database works fine for deleting a group when it becomes empty, except that triggers seem to bypass SQLAlchemy's cascade processing so things associated with the group don't get deleted.\nWhat is the best way to delete a group when all of its members leave and have this deletion cascade to related entities.\nI understand that I could do this manually by finding every place in my code where a user can leave a group and then doing the same thing as the trigger however, I'm afraid that I would miss places in the code (and I'm lazy).","AnswerCount":4,"Available Count":3,"Score":1.2,"is_accepted":true,"ViewCount":3255,"Q_Id":740630,"Users Score":3,"Answer":"The way I've generally handled this is to have a function on your user or group called leave_group.  When you want a user to leave a group, you call that function, and you can add any side effects you want into there.  In the long term, this makes it easier to add more and more side effects.  (For example when you want to check that someone is allowed to leave a group).","Q_Score":9,"Tags":"python,sqlalchemy","A_Id":763256,"CreationDate":"2009-04-11T19:07:00.000","Title":"SQLAlchemy many-to-many orphan deletion","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm trying to use SQLAlchemy to implement a basic users-groups model where users can have multiple groups and groups can have multiple users.\nWhen a group becomes empty, I want the group to be deleted, (along with other things associated with the group.  Fortunately, SQLAlchemy's cascade works fine with these more simple situations).\nThe problem is that cascade='all, delete-orphan' doesn't do exactly what I want; instead of deleting the group when the group becomes empty, it deletes the group when any member leaves the group.\nAdding triggers to the database works fine for deleting a group when it becomes empty, except that triggers seem to bypass SQLAlchemy's cascade processing so things associated with the group don't get deleted.\nWhat is the best way to delete a group when all of its members leave and have this deletion cascade to related entities.\nI understand that I could do this manually by finding every place in my code where a user can leave a group and then doing the same thing as the trigger however, I'm afraid that I would miss places in the code (and I'm lazy).","AnswerCount":4,"Available Count":3,"Score":0.1488850336,"is_accepted":false,"ViewCount":3255,"Q_Id":740630,"Users Score":3,"Answer":"I think you want cascade='save, update, merge, expunge, refresh, delete-orphan'.  This will prevent the \"delete\" cascade (which you get from \"all\") but maintain the \"delete-orphan\", which is what you're looking for, I think (delete when there are no more parents).","Q_Score":9,"Tags":"python,sqlalchemy","A_Id":770287,"CreationDate":"2009-04-11T19:07:00.000","Title":"SQLAlchemy many-to-many orphan deletion","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Trying to understand S3...How do you limit access to a file you upload to S3?  For example, from a web application, each user has files they can upload, but how do you limit access so only that user has access to that file?  It seems like the query string authentication requires an expiration date and that won't work for me, is there another way to do this?","AnswerCount":4,"Available Count":3,"Score":0.049958375,"is_accepted":false,"ViewCount":4305,"Q_Id":765964,"Users Score":1,"Answer":"You will have to build the whole access logic to S3 in your applications","Q_Score":10,"Tags":"python,django,amazon-web-services,amazon-s3","A_Id":766030,"CreationDate":"2009-04-19T19:51:00.000","Title":"Amazon S3 permissions","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":1,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Trying to understand S3...How do you limit access to a file you upload to S3?  For example, from a web application, each user has files they can upload, but how do you limit access so only that user has access to that file?  It seems like the query string authentication requires an expiration date and that won't work for me, is there another way to do this?","AnswerCount":4,"Available Count":3,"Score":1.0,"is_accepted":false,"ViewCount":4305,"Q_Id":765964,"Users Score":8,"Answer":"Have the user hit your server\nHave the server set up a query-string authentication with a short expiration (minutes, hours?)\nHave your server redirect to #2","Q_Score":10,"Tags":"python,django,amazon-web-services,amazon-s3","A_Id":768090,"CreationDate":"2009-04-19T19:51:00.000","Title":"Amazon S3 permissions","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":1,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Trying to understand S3...How do you limit access to a file you upload to S3?  For example, from a web application, each user has files they can upload, but how do you limit access so only that user has access to that file?  It seems like the query string authentication requires an expiration date and that won't work for me, is there another way to do this?","AnswerCount":4,"Available Count":3,"Score":1.0,"is_accepted":false,"ViewCount":4305,"Q_Id":765964,"Users Score":14,"Answer":"There are various ways to control access to the S3 objects:\n\nUse the query string auth - but as you noted this does require an expiration date.  You could make it far in the future, which has been good enough for most things I have done.\nUse the S3 ACLS - but this requires the user to have an AWS account and authenticate with AWS to access the S3 object.  This is probably not what you are looking for.\nYou proxy the access to the S3 object through your application, which implements your access control logic.  This will bring all the bandwidth through your box.\nYou can set up an EC2 instance with your proxy logic - this keeps the bandwidth closer to S3 and can reduce latency in certain situations.  The difference between this and #3 could be minimal, but depends your particular situation.","Q_Score":10,"Tags":"python,django,amazon-web-services,amazon-s3","A_Id":768050,"CreationDate":"2009-04-19T19:51:00.000","Title":"Amazon S3 permissions","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":1,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Given a time (eg. currently 4:24pm on Tuesday), I'd like to be able to select all businesses that are currently open out of a set of businesses. \n\nI have the open and close times for every business for every day of the week\nLet's assume a business can open\/close only on 00, 15, 30, 45 minute marks of each hour\nI'm assuming the same schedule each week.\nI am most interested in being able to quickly look up a set of businesses that is open at a certain time, not the space requirements of the data.\nMind you, some my open at 11pm one day and close 1am the next day. \nHolidays don't matter - I will handle these separately\n\nWhat's the most efficient way to store these open\/close times such that with a single time\/day-of-week tuple I can speedily figure out which businesses are open?\nI am using Python, SOLR and mysql. I'd like to be able to do the querying in SOLR. But frankly, I'm open to any suggestions and alternatives.","AnswerCount":7,"Available Count":5,"Score":0.1137907297,"is_accepted":false,"ViewCount":1489,"Q_Id":775161,"Users Score":4,"Answer":"You say you're using SOLR, don't care about storage, and want the lookups to be fast.  Then instead of storing open\/close tuples, index an entry for every open block of time at the level of granularity you need (15 mins).  For the encoding itself, you could use just cumulative hours:minutes.\nFor example, a store open from 4-5 pm on Monday, would have indexed values added for [40:00, 40:15, 40:30, 40:45].  A query at 4:24 pm on Monday would be normalized to 40:15, and therefore match that store document.\nThis may seem inefficient at first glance, but it's a relatively small constant penalty for indexing speed and space.  And makes the searches as fast as possible.","Q_Score":6,"Tags":"python,mysql,performance,solr","A_Id":775354,"CreationDate":"2009-04-21T23:48:00.000","Title":"Efficiently determining if a business is open or not based on store hours","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Given a time (eg. currently 4:24pm on Tuesday), I'd like to be able to select all businesses that are currently open out of a set of businesses. \n\nI have the open and close times for every business for every day of the week\nLet's assume a business can open\/close only on 00, 15, 30, 45 minute marks of each hour\nI'm assuming the same schedule each week.\nI am most interested in being able to quickly look up a set of businesses that is open at a certain time, not the space requirements of the data.\nMind you, some my open at 11pm one day and close 1am the next day. \nHolidays don't matter - I will handle these separately\n\nWhat's the most efficient way to store these open\/close times such that with a single time\/day-of-week tuple I can speedily figure out which businesses are open?\nI am using Python, SOLR and mysql. I'd like to be able to do the querying in SOLR. But frankly, I'm open to any suggestions and alternatives.","AnswerCount":7,"Available Count":5,"Score":1.2,"is_accepted":true,"ViewCount":1489,"Q_Id":775161,"Users Score":8,"Answer":"If you are willing to just look at single week at a time, you can canonicalize all opening\/closing times to be set numbers of minutes since the start of the week, say Sunday 0 hrs. For each store, you create a number of tuples of the form [startTime, endTime, storeId]. (For hours that spanned Sunday midnight, you'd have to create two tuples, one going to the end of the week, one starting at the beginning of the week). This set of tuples would be indexed (say, with a tree you would pre-process) on both startTime and endTime. The tuples shouldn't be that large: there are only ~10k minutes in a week, which can fit in 2 bytes. This structure would be graceful inside a MySQL table with appropriate indexes, and would be very resilient to constant insertions & deletions of records as information changed. Your query would simply be \"select storeId where startTime <= time and endtime >= time\", where time was the canonicalized minutes since midnight on sunday.\nIf information doesn't change very often, and you want to have lookups be very fast, you could solve every possible query up front and cache the results. For instance, there are only 672 quarter-hour periods in a week. With a list of businesses, each of which had a list of opening & closing times like Brandon Rhodes's solution, you could simply, iterate through every 15-minute period in a week, figure out who's open, then store the answer in a lookup table or in-memory list.","Q_Score":6,"Tags":"python,mysql,performance,solr","A_Id":775247,"CreationDate":"2009-04-21T23:48:00.000","Title":"Efficiently determining if a business is open or not based on store hours","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Given a time (eg. currently 4:24pm on Tuesday), I'd like to be able to select all businesses that are currently open out of a set of businesses. \n\nI have the open and close times for every business for every day of the week\nLet's assume a business can open\/close only on 00, 15, 30, 45 minute marks of each hour\nI'm assuming the same schedule each week.\nI am most interested in being able to quickly look up a set of businesses that is open at a certain time, not the space requirements of the data.\nMind you, some my open at 11pm one day and close 1am the next day. \nHolidays don't matter - I will handle these separately\n\nWhat's the most efficient way to store these open\/close times such that with a single time\/day-of-week tuple I can speedily figure out which businesses are open?\nI am using Python, SOLR and mysql. I'd like to be able to do the querying in SOLR. But frankly, I'm open to any suggestions and alternatives.","AnswerCount":7,"Available Count":5,"Score":0.0855049882,"is_accepted":false,"ViewCount":1489,"Q_Id":775161,"Users Score":3,"Answer":"Sorry I don't have an easy answer, but I can tell you that as the manager of a development team at a company in the late 90's we were tasked with solving this very problem and it was HARD.\nIt's not the weekly hours that's tough, that can be done with a relatively small bitmask (168 bits = 1 per hour of the week), the trick is the businesses which are closed every alternating Tuesday.\nStarting with a bitmask then moving on to an exceptions field is the best solution I've ever seen.","Q_Score":6,"Tags":"python,mysql,performance,solr","A_Id":775175,"CreationDate":"2009-04-21T23:48:00.000","Title":"Efficiently determining if a business is open or not based on store hours","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Given a time (eg. currently 4:24pm on Tuesday), I'd like to be able to select all businesses that are currently open out of a set of businesses. \n\nI have the open and close times for every business for every day of the week\nLet's assume a business can open\/close only on 00, 15, 30, 45 minute marks of each hour\nI'm assuming the same schedule each week.\nI am most interested in being able to quickly look up a set of businesses that is open at a certain time, not the space requirements of the data.\nMind you, some my open at 11pm one day and close 1am the next day. \nHolidays don't matter - I will handle these separately\n\nWhat's the most efficient way to store these open\/close times such that with a single time\/day-of-week tuple I can speedily figure out which businesses are open?\nI am using Python, SOLR and mysql. I'd like to be able to do the querying in SOLR. But frankly, I'm open to any suggestions and alternatives.","AnswerCount":7,"Available Count":5,"Score":0.0,"is_accepted":false,"ViewCount":1489,"Q_Id":775161,"Users Score":0,"Answer":"Have you looked at how many unique open\/close time combinations there are?  If there are not that many, make a reference table of the unique combinations and store the index of the appropriate entry against each business. Then you only have to search the reference table and then find the business with those indices.","Q_Score":6,"Tags":"python,mysql,performance,solr","A_Id":775459,"CreationDate":"2009-04-21T23:48:00.000","Title":"Efficiently determining if a business is open or not based on store hours","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Given a time (eg. currently 4:24pm on Tuesday), I'd like to be able to select all businesses that are currently open out of a set of businesses. \n\nI have the open and close times for every business for every day of the week\nLet's assume a business can open\/close only on 00, 15, 30, 45 minute marks of each hour\nI'm assuming the same schedule each week.\nI am most interested in being able to quickly look up a set of businesses that is open at a certain time, not the space requirements of the data.\nMind you, some my open at 11pm one day and close 1am the next day. \nHolidays don't matter - I will handle these separately\n\nWhat's the most efficient way to store these open\/close times such that with a single time\/day-of-week tuple I can speedily figure out which businesses are open?\nI am using Python, SOLR and mysql. I'd like to be able to do the querying in SOLR. But frankly, I'm open to any suggestions and alternatives.","AnswerCount":7,"Available Count":5,"Score":0.0285636566,"is_accepted":false,"ViewCount":1489,"Q_Id":775161,"Users Score":1,"Answer":"In your Solr index, instead of indexing each business as one document with hours, index every \"retail session\" for every business during the course of a week.  \nFor example if Joe's coffee is open Mon-Sat 6am-9pm and closed on Sunday, you would index six distinct documents, each with two indexed fields, \"open\" and \"close\".  If your units are 15 minute intervals, then the values can range from 0 to 7*24*4.  Assuming you have a unique ID for each business, store this in each document so you can map the sessions to businesses.\nThen you can simply do a range search in Solr:\nopen:[* TO N] AND close:[N+1 TO *]\nwhere N is computed to the Nth 15 minute interval that the current time falls into.  For examples if it's 10:10AM on Wednesday, your query would be:\nopen:[* TO 112] AND close:[113 TO *]\naka \"find a session that starts at or before 10:00am Wed and ends at or after 10:15am Wed\"\nIf you want to include other criteria in your search, such as location or products, you will need to index this with each session document as well.  This is a bit redundant, but if your index is not huge, it shouldn't be a problem.","Q_Score":6,"Tags":"python,mysql,performance,solr","A_Id":777443,"CreationDate":"2009-04-21T23:48:00.000","Title":"Efficiently determining if a business is open or not based on store hours","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a legacy database with an integer set as a primary key. It was initially managed manually, but since we are wanting to move to django, the admin tool seemed to be the right place to start. I created the model and am trying to set the primary key to be an autofield. It doesn't seem to be remembering the old id in updates, and it doesn't create new id's on insert. What am I doing wrong?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":454,"Q_Id":777778,"Users Score":2,"Answer":"The DB is responsible for managing the value of the ID. If you want to use AutoField, you have to change the column in the DB to use that. Django is not responsible for managing the generated ID","Q_Score":1,"Tags":"python,django,oracle,autofield","A_Id":778346,"CreationDate":"2009-04-22T15:18:00.000","Title":"How do I set up a model to use an AutoField with a legacy database in Python?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Python communicating with EXCEL... i need to find a way so that I can find\/search a row for given column datas. Now, i m scanning entire rows one by one... It would be useful, If there is some functions like FIND\/SEARCH\/REPLACE .... I dont see these features in pyExcelerator or xlrd modules.. I dont want to use win32com modules! it makes my tool windows based!\nFIND\/SEARCH Excel rows through Python.... Any idea, anybody?","AnswerCount":4,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":7840,"Q_Id":778093,"Users Score":0,"Answer":"With pyExcelerator you can do a simple optimization by finding the maximum row and column indices first (and storing them), so that you iterate over (row, i) for i in range(maxcol+1) instead of iterating over all the dictionary keys.  That may be the best you get, unless you want to go through and build up a dictionary mapping value to set of keys.\nIncidentally, if you're using pyExcelerator to write spreadsheets, be aware that it has some bugs.  I've encountered one involving writing integers between 230 and 232 (or thereabouts).  The original author is apparently hard to contact these days, so xlwt is a fork that fixes the (known) bugs.  For writing spreadsheets, it's a drop-in replacement for pyExcelerator; you could do import xlwt as pyExcelerator and change nothing else.  It doesn't read spreadsheets, though.","Q_Score":2,"Tags":"python,excel,search,pyexcelerator,xlrd","A_Id":779599,"CreationDate":"2009-04-22T16:23:00.000","Title":"pyExcelerator or xlrd - How to FIND\/SEARCH a row for the given few column data?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Python communicating with EXCEL... i need to find a way so that I can find\/search a row for given column datas. Now, i m scanning entire rows one by one... It would be useful, If there is some functions like FIND\/SEARCH\/REPLACE .... I dont see these features in pyExcelerator or xlrd modules.. I dont want to use win32com modules! it makes my tool windows based!\nFIND\/SEARCH Excel rows through Python.... Any idea, anybody?","AnswerCount":4,"Available Count":3,"Score":0.0996679946,"is_accepted":false,"ViewCount":7840,"Q_Id":778093,"Users Score":2,"Answer":"You can't. Those tools don't offer search capabilities. You must iterate over the data in a loop and search yourself. Sorry.","Q_Score":2,"Tags":"python,excel,search,pyexcelerator,xlrd","A_Id":779030,"CreationDate":"2009-04-22T16:23:00.000","Title":"pyExcelerator or xlrd - How to FIND\/SEARCH a row for the given few column data?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Python communicating with EXCEL... i need to find a way so that I can find\/search a row for given column datas. Now, i m scanning entire rows one by one... It would be useful, If there is some functions like FIND\/SEARCH\/REPLACE .... I dont see these features in pyExcelerator or xlrd modules.. I dont want to use win32com modules! it makes my tool windows based!\nFIND\/SEARCH Excel rows through Python.... Any idea, anybody?","AnswerCount":4,"Available Count":3,"Score":0.0996679946,"is_accepted":false,"ViewCount":7840,"Q_Id":778093,"Users Score":2,"Answer":"\"Now, i m scanning entire rows one by one\"\nWhat's wrong with that?  \"search\" -- in a spreadsheet context -- is really complicated.  Search values?  Search formulas?  Search down rows then across columns?  Search specific columns only?  Search specific rows only?\nA spreadsheet isn't simple text -- simple text processing design patterns don't apply.\nSpreadsheet search is hard and you're doing it correctly.  There's nothing better because it's hard.","Q_Score":2,"Tags":"python,excel,search,pyexcelerator,xlrd","A_Id":778282,"CreationDate":"2009-04-22T16:23:00.000","Title":"pyExcelerator or xlrd - How to FIND\/SEARCH a row for the given few column data?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Currently I have tables like: Pages, Groups, GroupPage, Users, UserGroup. With pickled sets I can implement the same thing with only 3 tables: Pages, Groups, Users.\nset seems a natural choice for implementing ACL, as group and permission related operations can be expressed very naturally with sets. If I store the allow\/deny lists as pickled sets, it can eliminate few intermediate tables for many-to-many relationship and allow permission editing without many database operations.\nIf human readability is important, I can always use json instead of cPickle for serialization and use set when manipulating the permission list in Python. It is highly unlikely that permissions will ever be edited directly using SQL. So is it a good design idea?\nWe're using SQLAlchemy as ORM, so it's likely to be implemented with PickleType column. I'm not planning to store the whole pickled \"resource\" recordset, only the set object made out of \"resource\" primary key values.","AnswerCount":4,"Available Count":2,"Score":0.0996679946,"is_accepted":false,"ViewCount":2877,"Q_Id":790613,"Users Score":2,"Answer":"Me, I'd stick with keeping persistent info in the relational DB in a form that's independent from a specific programming language used to access it -- much as I love Python (and that's a lot), some day I may want to access that info from some other language, and if I went for Python-specific formats... boy would I ever regret it...","Q_Score":1,"Tags":"python,set,acl,pickle","A_Id":791425,"CreationDate":"2009-04-26T10:37:00.000","Title":"Using Python set type to implement ACL","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Currently I have tables like: Pages, Groups, GroupPage, Users, UserGroup. With pickled sets I can implement the same thing with only 3 tables: Pages, Groups, Users.\nset seems a natural choice for implementing ACL, as group and permission related operations can be expressed very naturally with sets. If I store the allow\/deny lists as pickled sets, it can eliminate few intermediate tables for many-to-many relationship and allow permission editing without many database operations.\nIf human readability is important, I can always use json instead of cPickle for serialization and use set when manipulating the permission list in Python. It is highly unlikely that permissions will ever be edited directly using SQL. So is it a good design idea?\nWe're using SQLAlchemy as ORM, so it's likely to be implemented with PickleType column. I'm not planning to store the whole pickled \"resource\" recordset, only the set object made out of \"resource\" primary key values.","AnswerCount":4,"Available Count":2,"Score":0.0996679946,"is_accepted":false,"ViewCount":2877,"Q_Id":790613,"Users Score":2,"Answer":"You need to consider what it is that a DBMS provides you with, and which of those features you'll need to reimplement.\nThe issue of concurrency is a big one. There are a few race conditions to be considered (such as multiple writes taking place in different threads and processes and overwriting the new data), performance issues (write policy? What if your process crashes and you lose your data?), memory issues (how big are your permission sets? Will it all fit in RAM?).\nIf you have enough memory and you don't have to worry about concurrency, then your solution might be a good one. Otherwise I'd stick with a databases -- it takes care of those problems for you, and lots of work has gone into them to make sure that they always take your data from one consistent state to another.","Q_Score":1,"Tags":"python,set,acl,pickle","A_Id":790662,"CreationDate":"2009-04-26T10:37:00.000","Title":"Using Python set type to implement ACL","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have downloaded & installed the latest Python InformixDB package, but when I try to import it from the shell, I am getting the following error in the form of a Windows dialog box!\n\"A procedure entry point sqli_describe_input_stmt could not be located in the dynamic link isqlit09a.dll\"\nAny ideas what's happening?\nPlatform: Windows Vista (Biz Edition), Python 2.5.","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":435,"Q_Id":801515,"Users Score":0,"Answer":"Does other way to connect to database work?\nCan you use (configure in control panel) ODBC? If ODBC works then you can use Python win32 extensions (ActiveState distribution comes with it) and there is ODBC support. You can also use Jython which can work with ODBC via JDBC-ODBC bridge or with Informix JDBC driver.","Q_Score":1,"Tags":"python,informix","A_Id":823474,"CreationDate":"2009-04-29T09:01:00.000","Title":"Why Python informixdb package is throwing an error!","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have downloaded & installed the latest Python InformixDB package, but when I try to import it from the shell, I am getting the following error in the form of a Windows dialog box!\n\"A procedure entry point sqli_describe_input_stmt could not be located in the dynamic link isqlit09a.dll\"\nAny ideas what's happening?\nPlatform: Windows Vista (Biz Edition), Python 2.5.","AnswerCount":2,"Available Count":2,"Score":0.0996679946,"is_accepted":false,"ViewCount":435,"Q_Id":801515,"Users Score":1,"Answer":"Which version of IBM Informix Connect (I-Connect) or IBM Informix ClientSDK (CSDK) are you using?  The 'describe input' function is a more recent addition, but it is likely that you have it.\nHave you been able to connect to any Informix DBMS from the command shell?  If not, then the suspicion must be that you don't have the correct environment.  You would probably need to specify $INFORMIXDIR (or %INFORMIXDIR% - I'm going to omit '$' and '%' sigils from here on); you would need to set INFORMIXSERVER to connect successfully; you would need to have the correct directory (probably INFORMIXDIR\/bin on Windows; on Unix, it would be INFORMIXDIR\/lib and INFORMIXDIR\/lib\/esql or INFORMIXDIR\/lib\/odbc) on your PATH.","Q_Score":1,"Tags":"python,informix","A_Id":803958,"CreationDate":"2009-04-29T09:01:00.000","Title":"Why Python informixdb package is throwing an error!","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm developing software using the Google App Engine. \nI have some considerations about the optimal design regarding the following issue: I need to create and save snapshots of some entities at regular intervals.\nIn the conventional relational db world, I would create db jobs which would insert new summary records.\nFor example, a job would insert a record for every active user that would contain his current score to the \"userrank\" table, say, every hour.\nI'd like to know what's the best method to achieve this in Google App Engine. I know that there is the Cron service, but does it allow us to execute jobs which will insert\/update thousands of records?","AnswerCount":3,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":1473,"Q_Id":814896,"Users Score":3,"Answer":"I think you'll find that snapshotting every user's state every hour isn't something that will scale well no matter what your framework. A more ordinary environment will disguise this by letting you have longer running tasks, but you'll still reach the point where it's not practical to take a snapshot of every user's data, every hour.\nMy suggestion would be this: Add a 'last snapshot' field, and subclass the put() function of your model (assuming you're using Python; the same is possible in Java, but I don't know the syntax), such that whenever you update a record, it checks if it's been more than an hour since the last snapshot, and if so, creates and writes a snapshot record.\nIn order to prevent concurrent updates creating two identical snapshots, you'll want to give the snapshots a key name derived from the time at which the snapshot was taken. That way, if two concurrent updates try to write a snapshot, one will harmlessly overwrite the other.\nTo get the snapshot for a given hour, simply query for the oldest snapshot newer than the requested period. As an added bonus, since inactive records aren't snapshotted, you're saving a lot of space, too.","Q_Score":1,"Tags":"python,database,google-app-engine,cron","A_Id":815113,"CreationDate":"2009-05-02T13:54:00.000","Title":"Google App Engine - design considerations about cron tasks","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"So, I've been tossing this idea around in my head for a while now.  At its core, it's mostly a project for me to learn programming.  The idea is that, I have a large set of data, my music collection.  There are quite a few datasets that my music has.  Format, artist, title, album, genre, length, year of release, filename, directory, just to name a few.  Ideally, I'd like to create a database that has all of this data stored in it, and in the future, create a web interface on top of it that I can manage my music collection with.  So, my questions are as follows:\n\nDoes this sound like a good project to begin building databases from scratch with?\nWhat language would you recommend I start with?  I know tidbits of PHP, but I would imagine it would be awful to index data in a filesystem with.  Python was the other language I was thinking of, considering it's the language most people consider as a beginner language.\nIf you were going to implement this kind of system (the web interface) in your home (if you had PCs connected to a couple of stereos in your home and this was the software connected), what kind of features would you want to see?\n\nMy idea for building up the indexing script would be as follows:\n\nGet it to populate the database with only the filenames\nFrom the extension of the filename, determine format\nGet file size\nUsing the filenames in the database as a reference, pull ID3 or other applicable metadata (artist, track name, album, etc)\nCheck if all files still exist on disk, and if not, flag the file as unavailable\n\nAnother script would go in later and check if the files are back, if they are not, the will remove the row from the database.","AnswerCount":4,"Available Count":1,"Score":0.049958375,"is_accepted":false,"ViewCount":2085,"Q_Id":818752,"Users Score":1,"Answer":"Working on something you care about is the best way to learn programming, so I think this is a great idea.\nI also recommend Python as a place to start. Have fun!","Q_Score":2,"Tags":"php,python,mysql","A_Id":818763,"CreationDate":"2009-05-04T04:10:00.000","Title":"Web-Based Music Library (programming concept)","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"in my google app application, whenever a user purchases a number of contracts, these events are executed (simplified for clarity):\n\nuser.cash is decreased\nuser.contracts is increased by the number\ncontracts.current_price is updated.\nmarket.no_of_transactions is increased by 1.\n\nin a rdms, these would be placed within the same transaction. I conceive that google datastore does not allow entities of more than one model to be in the same transaction.\nwhat is the correct approach to this issue? how can I ensure that if a write fails, all preceding writes are rolled back? \nedit: I have obviously missed entity groups. Now I'd appreciate some further information regarding how they are used. Another point to clarify is google says \"Only use entity groups when they are needed for transactions. For other relationships between entities, use ReferenceProperty properties and Key values, which can be used in queries\". does it mean I have to define both a reference property (since I need queriying them) and a parent-child relationship (for transactions)? \nedit 2: and finally, how do I define two parents for an entity if the entity is being created to establish an n-to-n relationship between 2 parents?","AnswerCount":3,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":384,"Q_Id":836992,"Users Score":0,"Answer":"After a through research, I have found that a distributed transaction layer that provides a solution to the single entity group restriction has been developed in userland with the help of some google people. But so far, it is not released and is only available in java.","Q_Score":3,"Tags":"python,google-app-engine,transactions,google-cloud-datastore","A_Id":838960,"CreationDate":"2009-05-07T20:55:00.000","Title":"datastore transaction restrictions","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"Has anybody got recent experience with deploying a Django application with an SQL Server database back end? Our workplace is heavily invested in SQL Server and will not support Django if there isn't a sufficiently developed back end for it.\nI'm aware of mssql.django-pyodbc and django-mssql as unofficially supported back ends. Both projects seem to have only one person contributing which is a bit of a worry though the contributions seem to be somewhat regular.\nAre there any other back ends for SQL Server that are well supported? Are the two I mentioned here 'good enough' for production? What are your experiences?","AnswerCount":7,"Available Count":2,"Score":0.1137907297,"is_accepted":false,"ViewCount":48333,"Q_Id":842831,"Users Score":4,"Answer":"We are using django-mssql in production at our company. We too had an existing system using mssql. For me personally it was the best design decision I have ever made because my productivity increased dramatically now that I can use django .  \nI submitted a patch but when I started using django-mssql and did a week or two of testing.Since then (October 2008) we run our system on django and it runs solid. I also tried pyodbc but I did not like to much. \nWe are running a repair system where all transactions run through this system 40 heavy users. If you have more questions let me know.","Q_Score":52,"Tags":"python,sql-server,django,pyodbc","A_Id":843500,"CreationDate":"2009-05-09T06:45:00.000","Title":"Using Sql Server with Django in production","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Has anybody got recent experience with deploying a Django application with an SQL Server database back end? Our workplace is heavily invested in SQL Server and will not support Django if there isn't a sufficiently developed back end for it.\nI'm aware of mssql.django-pyodbc and django-mssql as unofficially supported back ends. Both projects seem to have only one person contributing which is a bit of a worry though the contributions seem to be somewhat regular.\nAre there any other back ends for SQL Server that are well supported? Are the two I mentioned here 'good enough' for production? What are your experiences?","AnswerCount":7,"Available Count":2,"Score":0.0285636566,"is_accepted":false,"ViewCount":48333,"Q_Id":842831,"Users Score":1,"Answer":"Haven't used it in production yet, but my initial experiences with django-mssql have been pretty solid. All you need are the Python Win32 extensions and to get the sqlserver_ado module onto your Python path. From there, you just use sql_server.pyodbc as your DATABASE_ENGINE. So far I haven't noticed anything missing, but I haven't fully banged on it yet either.","Q_Score":52,"Tags":"python,sql-server,django,pyodbc","A_Id":843476,"CreationDate":"2009-05-09T06:45:00.000","Title":"Using Sql Server with Django in production","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I need to launch a server side process off a mysql row insert. I'd appreciate some feedback\/suggestions.  So far I can think of three options:\n1st (least attractive):  My preliminary understanding is that I can write a kind of \"custom trigger\" in C that could fire off a row insert. In addition to having to renew my C skills this would requite a (custom?) recompile of MySQl ... yuck!\n2nd (slightly more attractive):  I could schedule a cron task server side of a program that I write that would query the table for new rows periodically.  This has the benefit of being DB and language independent.  The problem with this is that I suffer the delay of the cron's schedule.\n3rd (the option I'm leading with):  I could write a multi threaded program that would query the table for changes on a single thread, spawning new threads to process the newly inserted rows as needed. This has all the benefits of option 2 with less delay.\nI'll also mention that I'm leaning towards python for this task, as easy access to the system (linux) commands, as well as some in house perl scripts, is going to be very very useful.\nI'd appreciate any feedback\/suggestion\nThanks in advance.","AnswerCount":2,"Available Count":2,"Score":0.3799489623,"is_accepted":false,"ViewCount":227,"Q_Id":856173,"Users Score":4,"Answer":"Write an insert trigger which duplicates inserted rows to a secondary table. Periodically poll the secondary table for rows with an external application\/cronjob; if any rows are in the table, delete them and do your processing (or set a 'processing started' flag and only delete from the secondary table upon successful processing).\nThis will work very nicely for low to medium insert volumes. If you have a ton of data coming at your table, some kind of custom trigger in C is probably your only choice.","Q_Score":3,"Tags":"python,mysql,linux,perl","A_Id":856208,"CreationDate":"2009-05-13T05:15:00.000","Title":"launch a process off a mysql row insert","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I need to launch a server side process off a mysql row insert. I'd appreciate some feedback\/suggestions.  So far I can think of three options:\n1st (least attractive):  My preliminary understanding is that I can write a kind of \"custom trigger\" in C that could fire off a row insert. In addition to having to renew my C skills this would requite a (custom?) recompile of MySQl ... yuck!\n2nd (slightly more attractive):  I could schedule a cron task server side of a program that I write that would query the table for new rows periodically.  This has the benefit of being DB and language independent.  The problem with this is that I suffer the delay of the cron's schedule.\n3rd (the option I'm leading with):  I could write a multi threaded program that would query the table for changes on a single thread, spawning new threads to process the newly inserted rows as needed. This has all the benefits of option 2 with less delay.\nI'll also mention that I'm leaning towards python for this task, as easy access to the system (linux) commands, as well as some in house perl scripts, is going to be very very useful.\nI'd appreciate any feedback\/suggestion\nThanks in advance.","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":227,"Q_Id":856173,"Users Score":0,"Answer":"I had this issue about 2 years ago in .NET and I went with the 3rd approach.  However, looking back at it, I'm wondering if looking into Triggers with PhpMyAdmin & MySQL isn't the approach to look into.","Q_Score":3,"Tags":"python,mysql,linux,perl","A_Id":856210,"CreationDate":"2009-05-13T05:15:00.000","Title":"launch a process off a mysql row insert","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am writing a code in python in which I established a connection with database. I have queries in a loop. While queries being executed in the loop , If i unplug the network cable it should stop with an exception. But this not happens, When i again plug yhe network cabe after 2 minutes it starts again from where it ended. I am using linux and psycopg2. It is not showing exception","AnswerCount":3,"Available Count":2,"Score":0.0665680765,"is_accepted":false,"ViewCount":442,"Q_Id":867175,"Users Score":1,"Answer":"If you want to implement timeouts that work no matter how the client library is connecting to the server, it's best to attempt the DB operations in a separate thread, or, better, a separate process, which a \"monitor\" thread\/process can kill if needed; see the multiprocessing module in Python 2.6 standard library (there's a backported version for 2.5 if you need that). A process is better because when it's killed the operating system will take care of deallocating and cleaning up resources, while killing a thread is always a pretty unsafe and messy business.","Q_Score":0,"Tags":"python,tcp,database-connection","A_Id":867433,"CreationDate":"2009-05-15T06:03:00.000","Title":"db connection in python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am writing a code in python in which I established a connection with database. I have queries in a loop. While queries being executed in the loop , If i unplug the network cable it should stop with an exception. But this not happens, When i again plug yhe network cabe after 2 minutes it starts again from where it ended. I am using linux and psycopg2. It is not showing exception","AnswerCount":3,"Available Count":2,"Score":0.1325487884,"is_accepted":false,"ViewCount":442,"Q_Id":867175,"Users Score":2,"Answer":"Your database connection will almost certainly be based on a TCP socket. TCP sockets will hang around for a long time retrying before failing and (in python) raising an exception. Not to mention and retries\/automatic reconnection attempts in the database layer.","Q_Score":0,"Tags":"python,tcp,database-connection","A_Id":867202,"CreationDate":"2009-05-15T06:03:00.000","Title":"db connection in python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am in the design phase of a file upload service that allows users to upload very large zip files to our server as well as updates our database with the data.  Since the files are large (About 300mb) we want to allow the user to limit the amount of bandwidth they want to use for uploading.  They should also be able to pause and resume the transfer, and it should recover from a system reboot.  The user also needs to be authenticated in our MSSQL database to ensure that they have permission to upload the file and make changes to our database.  \nMy question is, what is the best technology to do this? We would like to minimize the amount of development required, but the only thing that I can think of now that would allow us to do this would be to create a client and server app from scratch in something like python, java or c#.  Is there an existing technology available that will allow us to do this?","AnswerCount":6,"Available Count":3,"Score":0.1325487884,"is_accepted":false,"ViewCount":3014,"Q_Id":878143,"Users Score":4,"Answer":"What's wrong with FTP? The protocol supports reusability and there are lots and lots of clients.","Q_Score":6,"Tags":"c#,java,python","A_Id":878154,"CreationDate":"2009-05-18T14:56:00.000","Title":"Resumable File Upload","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am in the design phase of a file upload service that allows users to upload very large zip files to our server as well as updates our database with the data.  Since the files are large (About 300mb) we want to allow the user to limit the amount of bandwidth they want to use for uploading.  They should also be able to pause and resume the transfer, and it should recover from a system reboot.  The user also needs to be authenticated in our MSSQL database to ensure that they have permission to upload the file and make changes to our database.  \nMy question is, what is the best technology to do this? We would like to minimize the amount of development required, but the only thing that I can think of now that would allow us to do this would be to create a client and server app from scratch in something like python, java or c#.  Is there an existing technology available that will allow us to do this?","AnswerCount":6,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":3014,"Q_Id":878143,"Users Score":0,"Answer":"On client side, flash; On server side, whatever (it wouldn't make any difference).\nNo existing technologies (except for using FTP or something).","Q_Score":6,"Tags":"c#,java,python","A_Id":878160,"CreationDate":"2009-05-18T14:56:00.000","Title":"Resumable File Upload","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am in the design phase of a file upload service that allows users to upload very large zip files to our server as well as updates our database with the data.  Since the files are large (About 300mb) we want to allow the user to limit the amount of bandwidth they want to use for uploading.  They should also be able to pause and resume the transfer, and it should recover from a system reboot.  The user also needs to be authenticated in our MSSQL database to ensure that they have permission to upload the file and make changes to our database.  \nMy question is, what is the best technology to do this? We would like to minimize the amount of development required, but the only thing that I can think of now that would allow us to do this would be to create a client and server app from scratch in something like python, java or c#.  Is there an existing technology available that will allow us to do this?","AnswerCount":6,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":3014,"Q_Id":878143,"Users Score":0,"Answer":"I'm surprised no one has mentioned torrent files. They can also be packaged into a script that then triggers something to execute.","Q_Score":6,"Tags":"c#,java,python","A_Id":30990243,"CreationDate":"2009-05-18T14:56:00.000","Title":"Resumable File Upload","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm currently working with a web application written in Python (and using SQLAlchemy). In order to handle authentication, the app first checks for a user ID in the session, and providing it exists, pulls that whole user record out of the database and stores it for the rest of that request. Another query is also run to check the permissions of the user it has stored.\nI'm fairly new to the web application development world, but from my understanding, hitting the database for something like this on every request isn't efficient. Or is this considered a normal thing to do?\nThe only thing I've thought of so far is pulling up this data once, and storing what's relevant (most of the data isn't even required on every request). However, this brings up the problem of what's supposed to happen if this user record happens to be removed in the interim. Any ideas on how best to manage this?","AnswerCount":4,"Available Count":4,"Score":0.1488850336,"is_accepted":false,"ViewCount":967,"Q_Id":881517,"Users Score":3,"Answer":"For a user login and basic permission tokens in a simple web application I will definitely store that in a cookie-based session.   It's true that a few SELECTs per request is not a big deal at all, but then again if you can get some\/all of your web requests to execute from cached data with no DB hits at all, that just adds that much more scalability to an app which is planning on receiving a lot of load.  \nThe issue of the user token being changed on the database is handled in two ways.  One is, ignore it - for a lot of use cases its not that big a deal for the user to log out and log back in again to get at new permissions that have been granted elsewhere (witness unix as an example).  The other is that all mutations of the user row are filtered through a method that also resets the state within the cookie-based session, but this is only effective if the user him\/herself is the one initiating the changes through the browser interface.\nIf OTOH neither of the above use cases apply to you, then you probably need to stick with a little bit of database access built into every request.","Q_Score":0,"Tags":"python,sqlalchemy","A_Id":890202,"CreationDate":"2009-05-19T08:11:00.000","Title":"SQLAlchemy - Database hits on every request?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm currently working with a web application written in Python (and using SQLAlchemy). In order to handle authentication, the app first checks for a user ID in the session, and providing it exists, pulls that whole user record out of the database and stores it for the rest of that request. Another query is also run to check the permissions of the user it has stored.\nI'm fairly new to the web application development world, but from my understanding, hitting the database for something like this on every request isn't efficient. Or is this considered a normal thing to do?\nThe only thing I've thought of so far is pulling up this data once, and storing what's relevant (most of the data isn't even required on every request). However, this brings up the problem of what's supposed to happen if this user record happens to be removed in the interim. Any ideas on how best to manage this?","AnswerCount":4,"Available Count":4,"Score":0.049958375,"is_accepted":false,"ViewCount":967,"Q_Id":881517,"Users Score":1,"Answer":"It's a Database, so often it's fairly common to \"hit\" the Database to pull the required data. You can reduce single queries if you build up Joins or Stored Procedures.","Q_Score":0,"Tags":"python,sqlalchemy","A_Id":881535,"CreationDate":"2009-05-19T08:11:00.000","Title":"SQLAlchemy - Database hits on every request?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm currently working with a web application written in Python (and using SQLAlchemy). In order to handle authentication, the app first checks for a user ID in the session, and providing it exists, pulls that whole user record out of the database and stores it for the rest of that request. Another query is also run to check the permissions of the user it has stored.\nI'm fairly new to the web application development world, but from my understanding, hitting the database for something like this on every request isn't efficient. Or is this considered a normal thing to do?\nThe only thing I've thought of so far is pulling up this data once, and storing what's relevant (most of the data isn't even required on every request). However, this brings up the problem of what's supposed to happen if this user record happens to be removed in the interim. Any ideas on how best to manage this?","AnswerCount":4,"Available Count":4,"Score":0.1488850336,"is_accepted":false,"ViewCount":967,"Q_Id":881517,"Users Score":3,"Answer":"\"hitting the database for something like this on every request isn't efficient.\"\nFalse.  And, you've assumed that there's no caching, which is also false.\nMost ORM layers are perfectly capable of caching rows, saving some DB queries.\nMost RDBMS's have extensive caching, resulting in remarkably fast responses to common queries.\nAll ORM layers will use consistent SQL, further aiding the database in optimizing the repetitive operations.  (Specifically, the SQL statement is cached, saving parsing and planning time.)\n\" Or is this considered a normal thing to do?\"\nTrue.\nUntil you can prove that your queries are the slowest part of your application, don't worry.  Build something that actually works.  Then optimize the part that you can prove is the bottleneck.","Q_Score":0,"Tags":"python,sqlalchemy","A_Id":882021,"CreationDate":"2009-05-19T08:11:00.000","Title":"SQLAlchemy - Database hits on every request?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm currently working with a web application written in Python (and using SQLAlchemy). In order to handle authentication, the app first checks for a user ID in the session, and providing it exists, pulls that whole user record out of the database and stores it for the rest of that request. Another query is also run to check the permissions of the user it has stored.\nI'm fairly new to the web application development world, but from my understanding, hitting the database for something like this on every request isn't efficient. Or is this considered a normal thing to do?\nThe only thing I've thought of so far is pulling up this data once, and storing what's relevant (most of the data isn't even required on every request). However, this brings up the problem of what's supposed to happen if this user record happens to be removed in the interim. Any ideas on how best to manage this?","AnswerCount":4,"Available Count":4,"Score":0.0996679946,"is_accepted":false,"ViewCount":967,"Q_Id":881517,"Users Score":2,"Answer":"You are basically talking about caching data as a performance optimization. As always, premature optimization is a bad idea. It's hard to know where the bottlenecks are beforehand, even more so if the application domain is new to you. Optimization adds complexity and if you optimize the wrong things, you not only have wasted the effort, but have made the necessary optimizations harder.\nRequesting user data usually is usually a pretty trivial query. You can build yourself a simple benchmark to see what kind of overhead it will introduce. If it isn't a significant percentage of your time-budget, just leave it be.\nIf you still want to cache the data on the application server then you have to come up with a cache invalidation scheme.\nPossible schemes are to check for changes from the database. If you don't have a lot of data to cache, this really isn't significantly more efficient than just reloading it.\nAnother option is to just time out cached data. This is a good option if instant visibility  of changes isn't important.\nAnother option is to actively invalidate caches on changes. This depends on whether you only modify the database through your application and if you have a single application server or a clustered solution.","Q_Score":0,"Tags":"python,sqlalchemy","A_Id":882171,"CreationDate":"2009-05-19T08:11:00.000","Title":"SQLAlchemy - Database hits on every request?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"MySQL has a RENAME TABLE statemnt that will allow you to change the name of a table.  \nThe manual mentions \n\nThe rename operation is done atomically, which means that no other session can \n  access any of the tables while the rename is running\n\nThe manual does not (to my knowedge) state how this renaming is accomplished.  Is an entire copy of the table created, given a new name, and then the old table deleted?  Or does MySQL do some magic behind the scenes to quickly rename the table?\nIn other words, does the size of the table have an effect on how long the RENAME table statement will take to run.  Are there other things that might cause the renaming of a block to significantly block?","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":2472,"Q_Id":885771,"Users Score":5,"Answer":"I believe MySQL only needs to alter metadata and references to the table's old name in stored procedures -- the number of records in the table should be irrelevant.","Q_Score":3,"Tags":"php,python,mysql,ruby,migration","A_Id":885783,"CreationDate":"2009-05-20T01:22:00.000","Title":"How does MySQL's RENAME TABLE statment work\/perform?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"At start you have a string 'DDMMYYYY HHMMSS' and I want at the end to insert the string in a date field  in sqlite3 database. The program is made in python. How can I do that ?","AnswerCount":3,"Available Count":1,"Score":0.0665680765,"is_accepted":false,"ViewCount":359,"Q_Id":889974,"Users Score":1,"Answer":"Even though the \".schema\" indicates that the field is a date or timestamp field... the field is actually a string.  You can format the string anyway you want. If memory serves... their is no validation at all.","Q_Score":0,"Tags":"python,sqlite,date","A_Id":890025,"CreationDate":"2009-05-20T20:08:00.000","Title":"Is it possible to format a date with sqlite3?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I posted this in the mailing list, but the reply I got wasn't too clear, so maybe I'll have better luck here.\nI currently have a grid with data in it.\nI would like to know if there is a way to give each generated row an\nID, or at least, associate each row with an object.\nIt may make it more clear if I clarify what i'm doing. It is described\nbelow.\nI pull data from an SQL table and display them in the grid.\nI am allowing for the user to add\/delete rows and edit cells.\nSay the user is viewing a grid that has 3 rows(which is, in turn, a\nmysql table with 3 rows).\nIf he is on the last row and presses the down arrow key, a new row is\ncreated and he can enter data into it and it will be inserted in the\ndatabase when he presses enter.\nHowever, I need a way to find out which rows will use \"insert\" query\nand which will use \"update\" query.\nSo ideally, when the user creates a new row by pressing the down\narrow, I would give that row an ID and store it in a list(or, if rows\nalready have IDs, just store it in a list) and when the user finishes\nentering data in the cells and presses enter, I would check if that\nrow's ID is in the in the list. If it is, i would insert all of that\nrow's cells values into the table, if not, i would update mysql with\nthe values.\nHope I made this clear.","AnswerCount":2,"Available Count":1,"Score":0.2913126125,"is_accepted":false,"ViewCount":1026,"Q_Id":901704,"Users Score":3,"Answer":"What I did when I encountered such a case was to create a column for IDs and set its width to 0.","Q_Score":2,"Tags":"python,wxpython,wxwidgets","A_Id":901806,"CreationDate":"2009-05-23T15:13:00.000","Title":"Give Wxwidget Grid rows an ID","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":1,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"In diagnosing SQL query problems, it would sometimes be useful to be able to see the query string after parameters are interpolated into it, using MySQLdb's safe interpolation.\nIs there a way to get that information from either a MySQL exception object or from the connection object itself?","AnswerCount":2,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":817,"Q_Id":904042,"Users Score":2,"Answer":"Use mysql's own ability to log the queries and watch for them.","Q_Score":2,"Tags":"python,mysql","A_Id":904077,"CreationDate":"2009-05-24T15:56:00.000","Title":"python-mysql : How to get interpolated query string?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"We have lots of data and some charts repesenting one logical item. Charts and data is stored in various files. As a result, most users can easily access and re-use the information in their applications.\nHowever, this not exactly a good way of storing data. Amongst other reasons, charts belong to some data, the charts and data have some meta-information that is not reflected in the file system, there are a lot of files, etc.\nIdeally, we want\n\none big \"file\" that can store all\ninformation (text, data and charts)\nthe \"file\" is human readable,\nportable and accessible by\nnon-technical users\nallows typical office applications\nlike MS Word or MS Excel to extract\ntext, data and charts easily.\nlight-weight, easy solution. Quick\nand dirty is sufficient. Not many\nusers.\n\nI am happy to use some scripting language like Python to generate the \"file\", third-party tools (ideally free as in beer), and everything that you find on a typical Windows-centric office computer.\nSome ideas that we currently ponder:\n\nusing VB or pywin32 to script MS Word or Excel \ncreating html and publish it on a RESTful web server\n\nCould you expand on the ideas above? Do you have any other ideas? What should we consider?","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":325,"Q_Id":915726,"Users Score":2,"Answer":"I can only agree with Reef on the general concepts he presented:\n\nYou will almost certainly prefer the data in a database than in a single large file\nYou should not worry that the data is not directly manipulated by users because as Reef mentioned, it can only go wrong. And you would be suprised at how ugly it can get\n\nConcerning the usage of MS Office integration tools I disagree with Reef. You can quite easily create an ActiveX Server (in Python if you like) that is accessible from the MS Office suite. As long as you have a solid infrastructure that allows some sort of file share, you could use that shared area to keep your code. I guess the mess Reef was talking about mostly is about keeping users' versions of your extract\/import code in sync. If you do not use some sort of shared repository (a simple shared folder) or if your infrastructure fails you often so that the shared folder becomes unavailable you will be in great pain. Note what is also somewhat painful if you do not have the appropriate tools but deal with many users: The ActiveX Server is best registered on each machine.\nSo.. I just said MS Office integration is very doable. But whether it is the best thing to do is a different matter. I strongly believe you will serve your users better if you build a web-site that handles their data for them. This sort of tool however almost certainly becomes an \"ongoing project\". Often, even as an \"ongoing project\", the time saved by your users could still make it worth it. But sometimes, strategically, you want to give your users a poorer experience to control project costs. In that case the ActiveX Server I mentioned could be what you want.","Q_Score":2,"Tags":"python,web-services,scripting,reporting,ms-office","A_Id":921061,"CreationDate":"2009-05-27T13:34:00.000","Title":"Reporting charts and data for MS-Office users","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"We have lots of data and some charts repesenting one logical item. Charts and data is stored in various files. As a result, most users can easily access and re-use the information in their applications.\nHowever, this not exactly a good way of storing data. Amongst other reasons, charts belong to some data, the charts and data have some meta-information that is not reflected in the file system, there are a lot of files, etc.\nIdeally, we want\n\none big \"file\" that can store all\ninformation (text, data and charts)\nthe \"file\" is human readable,\nportable and accessible by\nnon-technical users\nallows typical office applications\nlike MS Word or MS Excel to extract\ntext, data and charts easily.\nlight-weight, easy solution. Quick\nand dirty is sufficient. Not many\nusers.\n\nI am happy to use some scripting language like Python to generate the \"file\", third-party tools (ideally free as in beer), and everything that you find on a typical Windows-centric office computer.\nSome ideas that we currently ponder:\n\nusing VB or pywin32 to script MS Word or Excel \ncreating html and publish it on a RESTful web server\n\nCould you expand on the ideas above? Do you have any other ideas? What should we consider?","AnswerCount":2,"Available Count":2,"Score":0.0996679946,"is_accepted":false,"ViewCount":325,"Q_Id":915726,"Users Score":1,"Answer":"Instead of using one big file, You should use a database. Yes, You can store various types of files like gifs in the database if You like to.\nThe file would not be human readable or accessible by non-technical users, but this is good.\nThe database would have a website that Your non-technical users would use to insert, update and get data from. They would be able to display it on the page or export it to csv (or even xls - it's not that hard, I've seen some csv->xls converters). You could look into some open standard document formats, I think it should be quite easy to output data with in it. Do not try to output in \"doc\" format (but You could try \"docx\"). You should be able to easily teach the users how to export their data to a CSV and upload it to the site, or they could use the web interface to insert the data if they like to.\nIf You will allow Your users to mess with the raw data, they will break it (i have tried that, You have no idea how those guys could do that). The only way to prevent it is to make a web form that only allows them to perform certain actions that You exactly know how that they should suppose to perform.\nThe database + web page solution is the good one. Using VB or pywin32 to script MSOffice will get You in so much trouble I cannot even imagine.\nYou could use gnuplot or some other graphics library to draw (pretty straightforward to implement, it does all the hard work for You).\nI am afraid that the \"quick\" and dirty solution is tempting, but I only can say one thing: it will not be quick. In a few weeks You will find that hacking around with MSOffice scripting is messy, buggy and unreliable and the non-technical guys will hate it and say that in other companies they used to have a simple web panel that did that. Then You will find that You will not be able to ask about the scripting because everyone uses the web interfaces nowadays, as they are quite easy to implement and maintain.\nThis is not a small project, it's a medium sized one, You need to remember this while writing it. It will take some time to do it and test it and You will have to add new features as the non-technical guys will start using it. I knew some passionate php teenagers who would be able to write this panel in a week, but as I understand You have some better resources so I hope You will come with a really reliable, modular, extensible solution with good usability and happy users.\nGood luck!","Q_Score":2,"Tags":"python,web-services,scripting,reporting,ms-office","A_Id":920669,"CreationDate":"2009-05-27T13:34:00.000","Title":"Reporting charts and data for MS-Office users","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"A table has been ETLed to another table. My task is to verify the data between two tables programmatically. \nOne of the difficulties I m facing rite now is:\nhow to use the expression that I can get from, let s say, derived column task and verify with the source and destination.\nor in other words, how can I use the expression to work in the code. \nAny ideas....highly appreciated\nSagar","AnswerCount":1,"Available Count":1,"Score":0.3799489623,"is_accepted":false,"ViewCount":1102,"Q_Id":921268,"Users Score":2,"Answer":"Set up a column which holds a CHECKSUM() of each row.  Do a left outer join between the two tables .  If you have any nulls for the right side, you have problems.","Q_Score":0,"Tags":".net,ssis,ironpython","A_Id":1233648,"CreationDate":"2009-05-28T14:55:00.000","Title":"How to compare data of two tables transformed in SSIS package","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am having a script which makes a db connection and pereform some select operation.accroding to the fetch data i am calling different functions which also perform db operations.How can i pass db connection to the functions which are being called as i donot want to make new connection","AnswerCount":1,"Available Count":1,"Score":0.3799489623,"is_accepted":false,"ViewCount":515,"Q_Id":934221,"Users Score":2,"Answer":"Why to pass connection itself? Maybe build a class that handles all the DB-operation and just pass this class' instance around, calling it's methods to perform selects, inserts and all that DB-specific code?","Q_Score":0,"Tags":"python","A_Id":934709,"CreationDate":"2009-06-01T10:08:00.000","Title":"python db connection","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"It seems cx_Oracle doesn't.\nAny other suggestion for handling xml with Oracle and Python is appreciated.\nThanks.","AnswerCount":3,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1256,"Q_Id":936381,"Users Score":1,"Answer":"I managed to do this with cx_Oracle.\nI used the sys.xmltype.createxml() function in the statement that inserts the rows in a table with XMLTYPE fields; then I used prepare() and setinputsizes() to specify that the bind variables I used for XMLTYPE fields were of cx_Oracle.CLOB type.","Q_Score":5,"Tags":"python,xml,oracle,xmltype","A_Id":946854,"CreationDate":"2009-06-01T19:36:00.000","Title":"Is there an Oracle wrapper for Python that supports xmltype columns?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm trying to find a way to cause SQLAlchemy to generate a query of the following form:\n\nselect * from t where (a,b) in ((a1,b1),(a2,b2));\n\nIs this possible?\nIf not, any suggestions on a way to emulate it?","AnswerCount":4,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":6490,"Q_Id":948212,"Users Score":3,"Answer":"Well, thanks to Hao Lian above, I came up with a functional if painful solution.\nAssume that we have a declarative-style mapped class, Clazz, and a list of tuples of compound primary key values, values\n(Edited to use a better (IMO) sql generation style):\n\nfrom sqlalchemy.sql.expression import text,bindparam\n...\n    def __gParams(self, f, vs, ts, bs):\n        for j,v in enumerate(vs):\n            key = f % (j+97)\n            bs.append(bindparam(key, value=v, type_=ts[j]))\n            yield ':%s' % key\n\n    def __gRows(self, ts, values, bs):\n        for i,vs in enumerate(values):\n            f = '%%c%d' % i\n            yield '(%s)' % ', '.join(self.__gParams(f, vs, ts, bs))\n\n    def __gKeys(self, k, ts):\n        for c in k:  \n            ts.append(c.type)\n            yield str(c)\n\n    def __makeSql(self,Clazz, values):\n        t = []\n        b = []\n        return text(\n                '(%s) in (%s)' % (\n                    ', '.join(self.__gKeys(Clazz.__table__.primary_key,t)),\n                    ', '.join(self.__gRows(t,values,b))),\n                bindparams=b)\n\nThis solution works for compound or simple primary keys.  It's probably marginally slower than the col.in_(keys) for simple primary keys though.\nI'm still interested in suggestions of better ways to do this, but this way is working for now and performs noticeably better than the or_(and_(conditions)) way, or the for key in keys: do_stuff(q.get(key)) way.","Q_Score":10,"Tags":"python,sql,sqlalchemy","A_Id":951640,"CreationDate":"2009-06-04T01:40:00.000","Title":"Sqlalchemy complex in_ clause with tuple in list of tuples","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a webapp (call it myapp.com) that allows users to upload files.  The webapp will be deployed on Amazon EC2 instance.  I would like to serve these files back out to the webapp consumers via an s3 bucket based domain (i.e. uploads.myapp.com).  \nWhen the user uploads the files, I can easily drop them in into a folder called \"site_uploads\" on the local ec2 instance.  However, since my ec2 instance has finite storage, with a lot of uploads, the ec2 file system will fill up quickly.  \nIt would be great if the ec2 instance could mount and s3 bucket as the \"site_upload\" directory.  So that uploads to the EC2 \"site_upload\" directory automatically end up on uploads.myapp.com (and my webapp can use template tags to make sure the links for this uploaded content is based on that s3 backed domain).  This also gives me scalable file serving, as request for files hits s3 and not my ec2 instance.  Also, it makes it easy for my webapp to perform scaling\/resizing of the images that appear locally in \"site_upload\" but are actually on s3.\nI'm looking at s3fs, but judging from the comments, it doesn't look like a fully baked solution.  I'm looking for a non-commercial solution.\nFYI, The webapp is written in django, not that that changes the particulars too much.","AnswerCount":5,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":8589,"Q_Id":956904,"Users Score":0,"Answer":"I'd suggest using a separately-mounted EBS volume. I tried doing the same thing for some movie files. Access to S3 was slow, and S3 has some limitations like not being able to rename files, no real directory structure, etc.\nYou can set up EBS volumes in a RAID5 configuration and add space as you need it.","Q_Score":4,"Tags":"python,django,amazon-s3,amazon-ec2","A_Id":6308720,"CreationDate":"2009-06-05T16:39:00.000","Title":"mounting an s3 bucket in ec2 and using transparently as a mnt point","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I'm looking for resources to help migrate my design skills from traditional RDBMS data store over to AppEngine DataStore (ie: 'Soft Schema' style). I've seen several presentations and all touch on the the overarching themes and some specific techniques. \nI'm wondering if there's a place we could pool knowledge from experience (\"from the trenches\") on real-world approaches to rethinking how data is structured, especially porting existing applications. We're heavily Hibernate based and have probably travelled a bit down the wrong path with our data model already, generating some gnarly queries which our DB is struggling with.\nPlease respond if:\n\nYou have ported a non-trivial application over to AppEngine\nYou've created a common type of application from scratch in AppEngine\nYou've done neither 1 or 2, but are considering it and want to share your own findings so far.","AnswerCount":4,"Available Count":2,"Score":0.049958375,"is_accepted":false,"ViewCount":1022,"Q_Id":976639,"Users Score":1,"Answer":"The non relational database design essentially involves denormalization wherever possible.\nExample: Since the BigTable doesnt provide enough aggregation features, the sum(cash) option that would be in the RDBMS world is not available. Instead it would have to be stored on the model and the model save method must be overridden to compute the denormalized field sum.\nEssential basic design that comes to mind is that each template has its own model where all the required fields to be populated are present denormalized in the corresponding model; and you have an entire signals-update-bots complexity going on in the models.","Q_Score":6,"Tags":"java,python,google-app-engine,data-modeling","A_Id":979391,"CreationDate":"2009-06-10T16:13:00.000","Title":"Thinking in AppEngine","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I'm looking for resources to help migrate my design skills from traditional RDBMS data store over to AppEngine DataStore (ie: 'Soft Schema' style). I've seen several presentations and all touch on the the overarching themes and some specific techniques. \nI'm wondering if there's a place we could pool knowledge from experience (\"from the trenches\") on real-world approaches to rethinking how data is structured, especially porting existing applications. We're heavily Hibernate based and have probably travelled a bit down the wrong path with our data model already, generating some gnarly queries which our DB is struggling with.\nPlease respond if:\n\nYou have ported a non-trivial application over to AppEngine\nYou've created a common type of application from scratch in AppEngine\nYou've done neither 1 or 2, but are considering it and want to share your own findings so far.","AnswerCount":4,"Available Count":2,"Score":0.049958375,"is_accepted":false,"ViewCount":1022,"Q_Id":976639,"Users Score":1,"Answer":"The timeouts are tight and performance was ok but not great, so I found myself using extra space to save time; for example I had a many-to-many relationship between trading cards and players, so I duplicated the information of who owns what: Card objects have a list of Players and Player objects have a list of Cards.\nNormally storing all your information twice would have been silly (and prone to get out of sync) but it worked really well.\nIn Python they recently released a remote API so you can get an interactive shell to the datastore so you can play with your datastore without any timeouts or limits (for example, you can delete large swaths of data, or refactor your models); this is fantastically useful since otherwise as Julien mentioned it was very difficult to do any bulk operations.","Q_Score":6,"Tags":"java,python,google-app-engine,data-modeling","A_Id":978757,"CreationDate":"2009-06-10T16:13:00.000","Title":"Thinking in AppEngine","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I have a sqlite3 db which i insert\/select from in python. The app works great but i want to tweak it so no one can read from the DB without a password. How can i do this in python? note i have no idea where to start.","AnswerCount":5,"Available Count":1,"Score":0.1194272985,"is_accepted":false,"ViewCount":29194,"Q_Id":986403,"Users Score":3,"Answer":"SQLite databases are pretty human-readable, and there isn't any built-in encryption.\nAre you concerned about someone accessing and reading the database files directly, or accessing them through your program?  \nI'm assuming the former, because the latter isn't really database related--it's your application's security you're asking about. \nA few options come to mind:\n\nProtect the db with filesystem permissions rather than encryption.  You haven't mentioned what your environment is, so I can't say if this is workable for you or not, but it's probably the simplest and most reliable way, as you can't attempt to decrypt what you can't read.\nEncrypt in Python before writing, and decrypt in Python after reading.  Fairly simple, but you lose most of the power of SQL's set-based matching operations.\nSwitch to another database; user authentication and permissions are standard features of most multi-user databases.  When you find yourself up against the limitations of a tool, it may be easier to look around at other tools rather than hacking new features into the current tool.","Q_Score":10,"Tags":"python,sqlite,encryption","A_Id":987942,"CreationDate":"2009-06-12T12:35:00.000","Title":"Encrypted file or db in python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"A hashtable in memcached will be discarded either when it's Expired or when there's not enough memory and it's choosen to die based on the Least Recently Used algorithm.\nCan we put a Priority to hint or influence the LRU algorithm? I want to use memcached to store Web Sessions so i can use the cheap round-robin. \nI need to give Sessions Top Priority and nothing can kill them (not even if it's the Least Recently Used) except their own Max_Expiry.","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":799,"Q_Id":1000540,"Users Score":1,"Answer":"Not that I know of.\nmemcached is designed to be very fast and very straightforward, no fancy weights and priorities keep it simple.\nYou should not rely on memcache for persistent session storage. You should keep your sessions in the DB, but you can cache them in memcache. This way you can enjoy both worlds.","Q_Score":0,"Tags":"python,database,session,caching,memcached","A_Id":1130289,"CreationDate":"2009-06-16T09:56:00.000","Title":"Is there an option to configure a priority in memcached? (Similiar to Expiry)","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I need your advices to choose a Python Web Framework for developing a large project:\nDatabase (Postgresql)will have at least 500 tables, most of them with a composite primary\nkey, lots of constraints, indexes & queries. About 1,500 views for starting. The project belongs to the financial area. Alwasy new requirements are coming.\nWill a ORM be helpful?","AnswerCount":7,"Available Count":4,"Score":0.0285636566,"is_accepted":false,"ViewCount":2101,"Q_Id":1003131,"Users Score":1,"Answer":"I would absolutely recommend Repoze.bfg with SQLAlchemy for what you describe. I've done projects now in Django, TurboGears 1, TurboGears 2, Pylons, and dabbled in pure Zope3. BFG is far and away the framework most designed to accomodate a project growing in ways you don't anticipate at the beginning, but is far more lightweight and pared down than Grok or Zope 3. Also, the docs are the best technical docs of all of them, not the easiest, but the ones that answer the hard questions you're going to encounter the best. I'm currently doing a similar thing where we are overhauling a bunch of legacy databases into a new web deliverable app and we're using BFG, some Pylons, Zope 3 adapters, Genshi for templating, SQLAlchemy, and Dojo for the front end. We couldn't be happier with BFG, and it's working out great. BFGs classes as views that are actually zope multi-adapters is absolutely perfect for being able to override only very specific bits for certain domain resources. And the complete lack of magic globals anywhere makes testing and packaging the easiest we've had with any framework.\nymmv!","Q_Score":4,"Tags":"python,frameworks,web-frameworks","A_Id":2246687,"CreationDate":"2009-06-16T18:21:00.000","Title":"python web framework large project","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I need your advices to choose a Python Web Framework for developing a large project:\nDatabase (Postgresql)will have at least 500 tables, most of them with a composite primary\nkey, lots of constraints, indexes & queries. About 1,500 views for starting. The project belongs to the financial area. Alwasy new requirements are coming.\nWill a ORM be helpful?","AnswerCount":7,"Available Count":4,"Score":0.057080742,"is_accepted":false,"ViewCount":2101,"Q_Id":1003131,"Users Score":2,"Answer":"Depending on what you want to do, you actually have a few possible frameworks :\n[Django] Big, strong (to the limit of what a python framework can be), and the older in the race. Used by a few 'big' sites around the world ([Django sites]). Still is a bit of an overkill for almost everything and with a deprecated coding approach.\n[Turbogears] is a recent framework based on Pylons. Don't know much about it, but got many good feedbacks from friends who tried it.\n[Pylons] ( which Turbogears2 is based on ). Often saw at the \"PHP of Python\" , it allow very quick developements from scratch. Even if it can seem inappropriate for big projects, it's often the faster and easier way to go.\nThe last option is [Zope] ( with or without Plone ), but Plone is way to slow, and Zope learning curve is way too long ( not even speaking in replacing the ZODB with an SQL connector ) so if you don't know the framework yet, just forget about it.\nAnd yes, An ORM seem mandatory for a project of this size. For Django, you'll have to handle migration to their database models (don't know how hard it is to plug SQLAlchemy in Django). For turbogears and Pylons, the most suitable solution is [SQLAlchemy], which is actually the most complete ( and rising ) ORM for python. For zope ... well, nevermind\nLast but not least, I'm not sure you're starting on a good basis for your project. 500 tables on any python framework would scare me to death. A boring but rigid language such as java (hibernate+spring+tapestry or so) seem really more appropriate.","Q_Score":4,"Tags":"python,frameworks,web-frameworks","A_Id":1003329,"CreationDate":"2009-06-16T18:21:00.000","Title":"python web framework large project","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I need your advices to choose a Python Web Framework for developing a large project:\nDatabase (Postgresql)will have at least 500 tables, most of them with a composite primary\nkey, lots of constraints, indexes & queries. About 1,500 views for starting. The project belongs to the financial area. Alwasy new requirements are coming.\nWill a ORM be helpful?","AnswerCount":7,"Available Count":4,"Score":1.0,"is_accepted":false,"ViewCount":2101,"Q_Id":1003131,"Users Score":8,"Answer":"Yes.  An ORM is essential for mapping SQL stuff to objects.  \nYou have three choices.\n\nUse someone else's ORM\nRoll your own.\nTry to execute low-level SQL queries and pick out the fields they want from the result set.  This is -- actually -- a kind of ORM with the mappings scattered throughout the applications.  It may be fast to execute and appear easy to develop, but it is a maintenance nightmare.\n\nIf you're designing the tables first, any ORM will be painful.  For example, \"composite primary key\" is generally a bad idea, and with an ORM it's almost always a bad idea.  You'll need to have a surrogate primary key.  Then you can have all the composite keys with indexes you want.  They just won't be \"primary\".\nIf you design the objects first, then work out tables that will implement the objects, the ORM will be pleasant, simple and will run quickly, also.","Q_Score":4,"Tags":"python,frameworks,web-frameworks","A_Id":1003173,"CreationDate":"2009-06-16T18:21:00.000","Title":"python web framework large project","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I need your advices to choose a Python Web Framework for developing a large project:\nDatabase (Postgresql)will have at least 500 tables, most of them with a composite primary\nkey, lots of constraints, indexes & queries. About 1,500 views for starting. The project belongs to the financial area. Alwasy new requirements are coming.\nWill a ORM be helpful?","AnswerCount":7,"Available Count":4,"Score":1.0,"is_accepted":false,"ViewCount":2101,"Q_Id":1003131,"Users Score":12,"Answer":"Django has been used by many large organizations (Washington Post, etc.) and can connect with Postgresql easily enough.  I use it fairly often and have had no trouble.","Q_Score":4,"Tags":"python,frameworks,web-frameworks","A_Id":1003161,"CreationDate":"2009-06-16T18:21:00.000","Title":"python web framework large project","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"How can I configure Django with SQLAlchemy?","AnswerCount":5,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":30261,"Q_Id":1011476,"Users Score":0,"Answer":"There are many benefits of using SQLAlchemy instead of Django ORM, but consider developing a built-in-Django choice of SQLAlchemy\n(to have something called a production ready)\nBy the way, Django ORM is going better - in Django 1.11 they added UNION support (a SQL basic operator), so maybe some day there will be no need to change ORM.","Q_Score":29,"Tags":"python,django,sqlalchemy,configure","A_Id":45878579,"CreationDate":"2009-06-18T08:31:00.000","Title":"Configuring Django to use SQLAlchemy","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"This is mainly just a \"check my understanding\" type of question.  Here's my understanding of CLOBs and BLOBs as they work in Oracle:\n\nCLOBs are for text like XML, JSON, etc.  You should not assume what encoding the database will store it as (at least in an application) as it will be converted to whatever encoding the database was configured to use.\nBLOBs are for binary data.  You can be reasonably assured that they will be stored how you send them and that you will get them back with exactly the same data as they were sent as.\n\nSo in other words, say I have some binary data (in this case a pickled python object).  I need to be assured that when I send it, it will be stored exactly how I sent it and that when I get it back it will be exactly the same.  A BLOB is what I want, correct?\nIs it really feasible to use a CLOB for this?  Or will character encoding cause enough problems that it's not worth it?","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":43567,"Q_Id":1018073,"Users Score":56,"Answer":"CLOB is encoding and collation sensitive, BLOB is not.\nWhen you write into a CLOB using, say, CL8WIN1251, you write a 0xC0 (which is Cyrillic letter \u0410).\nWhen you read data back using AL16UTF16, you get back 0x0410, which is a UTF16 represenation of this letter.\nIf you were reading from a BLOB, you would get same 0xC0 back.","Q_Score":39,"Tags":"python,oracle","A_Id":1018096,"CreationDate":"2009-06-19T13:51:00.000","Title":"Help me understand the difference between CLOBs and BLOBs in Oracle","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"This is mainly just a \"check my understanding\" type of question.  Here's my understanding of CLOBs and BLOBs as they work in Oracle:\n\nCLOBs are for text like XML, JSON, etc.  You should not assume what encoding the database will store it as (at least in an application) as it will be converted to whatever encoding the database was configured to use.\nBLOBs are for binary data.  You can be reasonably assured that they will be stored how you send them and that you will get them back with exactly the same data as they were sent as.\n\nSo in other words, say I have some binary data (in this case a pickled python object).  I need to be assured that when I send it, it will be stored exactly how I sent it and that when I get it back it will be exactly the same.  A BLOB is what I want, correct?\nIs it really feasible to use a CLOB for this?  Or will character encoding cause enough problems that it's not worth it?","AnswerCount":2,"Available Count":2,"Score":1.0,"is_accepted":false,"ViewCount":43567,"Q_Id":1018073,"Users Score":10,"Answer":"Your understanding is correct. Since you mention Python, think of the Python 3 distinction between strings and bytes: CLOBs and BLOBs are quite analogous, with the extra issue that the encoding of CLOBs is not under your app's control.","Q_Score":39,"Tags":"python,oracle","A_Id":1018102,"CreationDate":"2009-06-19T13:51:00.000","Title":"Help me understand the difference between CLOBs and BLOBs in Oracle","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have been building business database applications such as finance, inventory and other business requirement applications. I am planning to shift to Python. What would be the tools to start with best. I would need to do master, transaction forms, processing (back end), reports and that sort of thing. The database would be postgress or mysql. As I am new to Python I understand that I need besides Python the ORM and also a framework. My application is not a web site related but it could also be need to be done over the web if needed. \nHow to choose the initial setup of tool combinations?","AnswerCount":6,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":9831,"Q_Id":1020775,"Users Score":0,"Answer":"just FYI, for PyQT, the book   has a chapter 15 with Databases, It looks good. and the book has something with data and view etc. I have read it and I think it's well worth your time:)","Q_Score":9,"Tags":"python,frame","A_Id":1021195,"CreationDate":"2009-06-20T02:22:00.000","Title":"Python database application framework and tools","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"which versions of sqlite may best suite for python 2.6.2?","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":444,"Q_Id":1025493,"Users Score":0,"Answer":"I'm using 3.4.0 out of inertia (it's what came with the Python 2.* versions I'm using) but there's no real reason (save powerful inertia;-) to avoid upgrading to 3.4.2, which fixes a couple of bugs that could lead to DB corruption and introduces no incompatibilities that I know of. (If you stick with 3.4.0 I'm told the key thing is to avoid VACUUM as it might mangle your data).\nPython 3.1 comes with SQLite 3.6.11 (which is supposed to work with Python 2.* just as well) and I might one day update to that (or probably to the latest, currently 3.6.15, to pick up a slew of minor bug fixes and enhancements) just to make sure I'm using identical releases on either Python 2 or Python 3 -- I've never observed a compatibility problem, but I doubt there has been thorough testing to support reading and writing the same DB from 3.4.0 and 3.6.11 (or any two releases so far apart from each other!-).","Q_Score":2,"Tags":"python,sqlite,python-2.6","A_Id":1028006,"CreationDate":"2009-06-22T04:49:00.000","Title":"sqlite version for python26","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm using the above mentioned Python lib to connect to a MySQL server. So far I've worked locally and all worked fine, until i realized I'll have to use my program in a network where all access goes through a proxy.\nDoes anyone now how I can set the connections managed by that lib to use a proxy?\nAlternatively: do you know of another Python lib for MySQL that can handle this?\nI also have no idea if the if the proxy server will allow access to the standard MySQL port or how I can trick it to allow it. Help on this is also welcomed.","AnswerCount":3,"Available Count":1,"Score":0.0665680765,"is_accepted":false,"ViewCount":2939,"Q_Id":1027751,"Users Score":1,"Answer":"there are a lot of different possibilities here. the only way you're going to get a definitive answer is to talk to the person that runs the proxy.\nif this is a web app and the web server and the database serve are both on the other side of a proxy, then you won't need to connect to the mysql server at all since the web app will do it for you.","Q_Score":2,"Tags":"python,mysql,proxy","A_Id":1027817,"CreationDate":"2009-06-22T15:11:00.000","Title":"MySQLdb through proxy","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am newbie in Google App Engine. While I was going through the tutorial, I found several things that we do in php-mysql is not available in GAE. For example in dataStore auto increment feature is not available. Also I am confused about session management in GAE. Over all I am confused and can not visualize the whole thing.\nPlease advise me a simple user management system with user registration, user login, user logout, session (create,manage,destroy) with data Store. Also please advise me where I can get simple but effective examples.\nThanks in advance.","AnswerCount":3,"Available Count":1,"Score":0.0665680765,"is_accepted":false,"ViewCount":7295,"Q_Id":1030293,"Users Score":1,"Answer":"You don't write user management and registration and all that, because you use Google's own authentication services. This is all included in the App Engine documentation.","Q_Score":17,"Tags":"php,python,google-app-engine","A_Id":1030362,"CreationDate":"2009-06-23T01:58:00.000","Title":"Simple User management example for Google App Engine?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I'm making a Django web-app which allows a user to build up a set of changes over a series of GETs\/POSTs before committing them to the database (or reverting) with a final POST. I have to keep the updates isolated from any concurrent database users until they are confirmed (this is a configuration front-end), ruling out committing after each POST.\nMy preferred solution is to use a per-session transaction. This keeps all the problems of remembering what's changed (and how it affects subsequent queries), together with implementing commit\/rollback, in the database where it belongs. Deadlock and long-held locks are not an issue, as due to external constraints there can only be one user configuring the system at any one time, and they are well-behaved.\nHowever, I cannot find documentation on setting up Django's ORM to use this sort of transaction model. I have thrown together a minimal monkey-patch (ew!) to solve the problem, but dislike such a fragile solution. Has anyone else done this before? Have I missed some documentation somewhere?\n(My version of Django is 1.0.2 Final, and I am using an Oracle database.)","AnswerCount":3,"Available Count":1,"Score":0.1325487884,"is_accepted":false,"ViewCount":2065,"Q_Id":1033934,"Users Score":2,"Answer":"I came up with something similar to the Memento pattern, but different enough that I think it bears posting.  When a user starts an editing session, I duplicate the target object to a temporary object in the database.  All subsequent editing operations affect the duplicate.  Instead of saving the object state in a memento at each change, I store operation objects.  When I apply an operation to an object, it returns the inverse operation, which I store.  \nSaving operations is much cheaper for me than mementos, since the operations can be described with a few small data items, while the object being edited is much bigger.  Also I apply the operations as I go and save the undos, so that the temporary in the db always corresponds to the version in the user's browser.  I never have to replay a collection of changes; the temporary is always only one operation away from the next version.\nTo implement \"undo,\" I pop the last undo object off the stack (as it were--by retrieving the latest operation for the temporary object from the db) apply it to the temporary and return the transformed temporary.  I could also push the resultant operation onto a redo stack if I cared to implement redo.\nTo implement \"save changes,\" i.e. commit, I de-activate and time-stamp the original object and activate the temporary in it's place.\nTo implement \"cancel,\" i.e. rollback,  I do nothing!  I could delete the temporary, of course, because there's no way for the user to retrieve it once the editing session is over, but I like to keep the canceled edit sessions so I can run stats on them before clearing them out with a cron job.","Q_Score":8,"Tags":"python,django,transactions","A_Id":1121915,"CreationDate":"2009-06-23T17:16:00.000","Title":"Per-session transactions in Django","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a system sitting on a \"Master Server\", that is periodically transferring quite a few chunks of information from a MySQL DB to another server in the web.\nBoth servers have a MySQL Server and an Apache running. I would like an easy-to-use solution for this.\nCurrently I'm looking into:\n\nXMLRPC\nRestFul Services\na simple POST to a processing script\nsocket transfers\n\nThe app on my master is a TurboGears app, so I would prefer \"pythonic\" aka  less ugly solutions. Copying a dumped table to another server via FTP \/ SCP or something like that might be quick, but in my eyes it is also very (quick and) dirty, and I'd love to have a nicer solution.\nCan anyone describe shortly how you would do this the \"best-practise\" way?\nThis doesn't necessarily have to involve Databases. Dumping the table on Server1 and transferring the raw data in a structured way so server2 can process it without parsing too much is just as good. One requirement though: As soon as the data arrives on server2, I want it to be processed, so there has to be a notification of some sort when the transfer is done. Of course I could just write my whole own server sitting on a socket on the second machine and accepting the file with own code and processing it and so forth, but this is just a very very small piece of a very big system, so I dont want to spend half a day implementing this.\nThanks,\nTom","AnswerCount":5,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":810,"Q_Id":1043528,"Users Score":2,"Answer":"Server 1: Convert rows to JSON, call the RESTful api of second with JSON data\nServer 2: listens on a URI e.g. POST \/data , get json data convert back to dictionary or ORM objects, insert into db\nsqlalchemy\/sqlobject and simplejson is what you need.","Q_Score":2,"Tags":"python,web-services,database-design","A_Id":1043653,"CreationDate":"2009-06-25T11:59:00.000","Title":"Best Practise for transferring a MySQL table to another server?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a system sitting on a \"Master Server\", that is periodically transferring quite a few chunks of information from a MySQL DB to another server in the web.\nBoth servers have a MySQL Server and an Apache running. I would like an easy-to-use solution for this.\nCurrently I'm looking into:\n\nXMLRPC\nRestFul Services\na simple POST to a processing script\nsocket transfers\n\nThe app on my master is a TurboGears app, so I would prefer \"pythonic\" aka  less ugly solutions. Copying a dumped table to another server via FTP \/ SCP or something like that might be quick, but in my eyes it is also very (quick and) dirty, and I'd love to have a nicer solution.\nCan anyone describe shortly how you would do this the \"best-practise\" way?\nThis doesn't necessarily have to involve Databases. Dumping the table on Server1 and transferring the raw data in a structured way so server2 can process it without parsing too much is just as good. One requirement though: As soon as the data arrives on server2, I want it to be processed, so there has to be a notification of some sort when the transfer is done. Of course I could just write my whole own server sitting on a socket on the second machine and accepting the file with own code and processing it and so forth, but this is just a very very small piece of a very big system, so I dont want to spend half a day implementing this.\nThanks,\nTom","AnswerCount":5,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":810,"Q_Id":1043528,"Users Score":0,"Answer":"Assuming your situation allows this security-wise, you forgot one transport mechanism: simply opening a mysql connection from one server to another.\nMe, I would start by thinking about one script that ran regularly on the write server and opens a read only db connection to the read server (A bit of added security) and a full connection to it's own data base server. \nHow you then proceed depends on the data (is it just inserts to deal with? do you have to mirror deletes? how many inserts vs updates? etc) but basically you could write a script that pulled data from the read server and processed it immediately into the write server.\nAlso, would mysql server replication work or would it be to over-blown as a solution?","Q_Score":2,"Tags":"python,web-services,database-design","A_Id":1043595,"CreationDate":"2009-06-25T11:59:00.000","Title":"Best Practise for transferring a MySQL table to another server?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I want to access a postgreSQL database that's running on a remote machine, from Python in OS\/X. Do I have to install postgres on the mac as well? Or will psycopg2 work on its own. \nAny hints for a good installation guide for psycopg2 for os\/x?","AnswerCount":3,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":4829,"Q_Id":1052957,"Users Score":3,"Answer":"macports tells me that the psycopg2 package has a dependency on the postgres client and libraries (but not the db server). If you successfully installed psycopg, then you should be good to go.\nIf you haven't installed yet, consider using macports or fink to deal with dependency resolution for you. In most cases, this will make things easier (occasionally build problems erupt).","Q_Score":2,"Tags":"python,macos,postgresql","A_Id":1052990,"CreationDate":"2009-06-27T14:52:00.000","Title":"psycopg2 on OSX: do I have to install PostgreSQL too?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":0},{"Question":"I have a username which I must change in numerous (up to ~25) tables.  (Yeah, I know.)  An atomic transaction seems to be the way to go for this sort of thing.  However, I do not know how to do this with pyodbc.  I've seen various tutorials on atomic transactions before, but have never used them.\nThe setup: Windows platform, Python 2.6, pyodbc, Microsoft SQL 2005.  I've used pyodbc for single SQL statements, but no compound statements or transactions.\nBest practices for SQL seem to suggest that creating a stored procedure is excellent for this.  My fears about doing a stored procedure are as follows, in order of increasing importance:\n    1) I have never written a stored procedure.\n    2) I heard that pyodbc does not return results from stored procedures as of yet.\n    3) This is most definitely Not My Database.  It's vendor-supplied, vendor-updated, and so forth.\nSo, what's the best way to go about this?","AnswerCount":2,"Available Count":1,"Score":-1.0,"is_accepted":false,"ViewCount":27883,"Q_Id":1063770,"Users Score":-10,"Answer":"I don't think pyodbc has any specific support for transactions. You need to send the SQL command to start\/commit\/rollback transactions.","Q_Score":15,"Tags":"python,transactions,pyodbc","A_Id":1063879,"CreationDate":"2009-06-30T13:45:00.000","Title":"In Python, Using pyodbc, How Do You Perform Transactions?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am not very familiar with databases, and so I do not know how to partition a table using SQLAlchemy.\nYour help would be greatly appreciated.","AnswerCount":3,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":7505,"Q_Id":1085304,"Users Score":3,"Answer":"Automatic partitioning is a very database engine specific concept and SQLAlchemy doesn't provide any generic tools to manage partitioning. Mostly because it wouldn't provide anything really useful while being another API to learn. If you want to do database level partitioning then do the CREATE TABLE statements using custom Oracle DDL statements (see Oracle documentation how to create partitioned tables and migrate data to them). You can use a partitioned table in SQLAlchemy just like you would use a normal table, you just need the table declaration so that SQLAlchemy knows what to query. You can reflect the definition from the database, or just duplicate the table declaration in SQLAlchemy code.\nVery large datasets are usually time-based, with older data becoming read-only or read-mostly and queries usually only look at data from a time interval. If that describes your data, you should probably partition your data using the date field.\nThere's also application level partitioning, or sharding, where you use your application to split data across different database instances. This isn't all that popular in the Oracle world due to the exorbitant pricing models. If you do want to use sharding, then look at SQLAlchemy documentation and examples for that, for how SQLAlchemy can support you in that, but be aware that application level sharding will affect how you need to build your application code.","Q_Score":2,"Tags":"python,sqlalchemy","A_Id":1087081,"CreationDate":"2009-07-06T03:33:00.000","Title":"how to make table partitions?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I want to write some unittests for an application that uses MySQL. However, I do not want to connect to a real mysql database, but rather to a temporary one that doesn't require any SQL server at all.\nAny library (I could not find anything on google)? Any design pattern? Note that DIP doesn't work since I will still have to test the injected class.","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":3416,"Q_Id":1088077,"Users Score":12,"Answer":"There isn't a good way to do that.  You want to run your queries against a real MySQL server, otherwise you don't know if they will work or not.\nHowever, that doesn't mean you have to run them against a production server. We have scripts that create a Unit Test database, and then tear it down once the unit tests have run.  That way we don't have to maintain a static test database, but we still get to test against the real server.","Q_Score":8,"Tags":"python,mysql,unit-testing","A_Id":1088090,"CreationDate":"2009-07-06T17:00:00.000","Title":"testing python applications that use mysql","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have id values for products that I need store. Right now they are all integers, but I'm not sure if the data provider in the future will introduce letters or symbols into that mix, so I'm debating whether to store it now as integer or string.\nAre there performance or other disadvantages to saving the values as strings?","AnswerCount":10,"Available Count":8,"Score":0.0199973338,"is_accepted":false,"ViewCount":10684,"Q_Id":1090022,"Users Score":1,"Answer":"You won't be able to do comparisons correctly. \"... where x > 500\" is not same as \".. where x > '500'\" because \"500\" > \"100000\"\nPerformance wise string it would be a hit especially if you use indexes as integer indexes are much faster than string indexes.\n\nOn the other hand it really depends upon your situation. If you intend to store something like phone numbers or student enrollment numbers, then it makes perfect sense to use strings.","Q_Score":22,"Tags":"python,mysql,database,database-design","A_Id":1090708,"CreationDate":"2009-07-07T01:58:00.000","Title":"Drawbacks of storing an integer as a string in a database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have id values for products that I need store. Right now they are all integers, but I'm not sure if the data provider in the future will introduce letters or symbols into that mix, so I'm debating whether to store it now as integer or string.\nAre there performance or other disadvantages to saving the values as strings?","AnswerCount":10,"Available Count":8,"Score":0.0,"is_accepted":false,"ViewCount":10684,"Q_Id":1090022,"Users Score":0,"Answer":"Better use independent ID and add string ID if necessary: if there's a business indicator you need to include, why make it system ID?\nMain drawbacks:\n\nInteger operations and indexing always show better performance on large scales of data (more than 1k rows in a table, not to speak of connected tables)\nYou'll have to make additional checks to restrict numeric-only values in a column: these can be regex whether on client or database side. Anyway, you'll have to guarantee somehow that there's actually integer.\nAnd you will create additional context layer for developers to know, and anyway someone will always mess this up :)","Q_Score":22,"Tags":"python,mysql,database,database-design","A_Id":1090924,"CreationDate":"2009-07-07T01:58:00.000","Title":"Drawbacks of storing an integer as a string in a database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have id values for products that I need store. Right now they are all integers, but I'm not sure if the data provider in the future will introduce letters or symbols into that mix, so I'm debating whether to store it now as integer or string.\nAre there performance or other disadvantages to saving the values as strings?","AnswerCount":10,"Available Count":8,"Score":0.0599281035,"is_accepted":false,"ViewCount":10684,"Q_Id":1090022,"Users Score":3,"Answer":"I've just spent the last year dealing with a database that has almost all IDs as strings, some with digits only, and others mixed. These are the problems:\n\nGrossly restricted ID space. A 4 char (digit-only) ID has capacity for 10,000 unique values. A 4 byte numeric has capacity for over 4 billion.\nUnpredictable ID space coverage. Once IDs start including non-digits it becomes hard to predict where you can create new IDs without collisions.\nConversion and display problems in certain circumstances, when scripting or on export for instance. If the ID gets interpreted as a number and there is a leading zero, the ID gets altered.\nSorting problems. You can't rely on the natural order being helpful.\n\nOf course, if you run out of IDs, or don't know how to create new IDs, your app is dead. I suggest that if you can't control the format of your incoming IDs then you need to create your own (numeric) IDs and relate the user provided ID to that. You can then ensure that your own ID is reliable and unique (and numeric) but provide a user-viewable ID that can have whatever format your users want, and doesn't even have to be unique across the whole app. This is more work, but if you'd been through what I have you'd know which way to go.\nAnil G","Q_Score":22,"Tags":"python,mysql,database,database-design","A_Id":1090390,"CreationDate":"2009-07-07T01:58:00.000","Title":"Drawbacks of storing an integer as a string in a database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have id values for products that I need store. Right now they are all integers, but I'm not sure if the data provider in the future will introduce letters or symbols into that mix, so I'm debating whether to store it now as integer or string.\nAre there performance or other disadvantages to saving the values as strings?","AnswerCount":10,"Available Count":8,"Score":1.2,"is_accepted":true,"ViewCount":10684,"Q_Id":1090022,"Users Score":37,"Answer":"Unless you really need the features of an integer (that is, the ability to do arithmetic), then it is probably better for you to store the product IDs as strings. You will never need to do anything like add two product IDs together, or compute the average of a group of product IDs, so there is no need for an actual numeric type.\nIt is unlikely that storing product IDs as strings will cause a measurable difference in performance. While there will be a slight increase in storage size, the size of a product ID string is likely to be much smaller than the data in the rest of your database row anyway.\nStoring product IDs as strings today will save you much pain in the future if the data provider decides to start using alphabetic or symbol characters. There is no real downside.","Q_Score":22,"Tags":"python,mysql,database,database-design","A_Id":1090065,"CreationDate":"2009-07-07T01:58:00.000","Title":"Drawbacks of storing an integer as a string in a database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have id values for products that I need store. Right now they are all integers, but I'm not sure if the data provider in the future will introduce letters or symbols into that mix, so I'm debating whether to store it now as integer or string.\nAre there performance or other disadvantages to saving the values as strings?","AnswerCount":10,"Available Count":8,"Score":0.0599281035,"is_accepted":false,"ViewCount":10684,"Q_Id":1090022,"Users Score":3,"Answer":"It really depends on what kind of id you are talking about. If it's a code like a phone number it would actually be better to use a varchar for the id and then have your own id to be a serial for the db and use for primary key. In a case where the integer have no numerical value, varchars are generally prefered.","Q_Score":22,"Tags":"python,mysql,database,database-design","A_Id":1090057,"CreationDate":"2009-07-07T01:58:00.000","Title":"Drawbacks of storing an integer as a string in a database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have id values for products that I need store. Right now they are all integers, but I'm not sure if the data provider in the future will introduce letters or symbols into that mix, so I'm debating whether to store it now as integer or string.\nAre there performance or other disadvantages to saving the values as strings?","AnswerCount":10,"Available Count":8,"Score":0.0,"is_accepted":false,"ViewCount":10684,"Q_Id":1090022,"Users Score":0,"Answer":"Integers are more efficient from a storage and performance perspective.  However, if there is a remote chance that alpha characters may be introduced, then you should use a string.  In my opinion, the efficiency and performance benefits are likely to be negligible, whereas the time it takes to modify your code may not be.","Q_Score":22,"Tags":"python,mysql,database,database-design","A_Id":1090035,"CreationDate":"2009-07-07T01:58:00.000","Title":"Drawbacks of storing an integer as a string in a database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have id values for products that I need store. Right now they are all integers, but I'm not sure if the data provider in the future will introduce letters or symbols into that mix, so I'm debating whether to store it now as integer or string.\nAre there performance or other disadvantages to saving the values as strings?","AnswerCount":10,"Available Count":8,"Score":0.0199973338,"is_accepted":false,"ViewCount":10684,"Q_Id":1090022,"Users Score":1,"Answer":"The space an integer would take up would me much less than a string.  For example 2^32-1 = 4,294,967,295.  This would take 10 bytes to store, where as the integer would take 4 bytes to store.  For a single entry this is not very much space, but when you start in the millions...  As many other posts suggest there are several other issues to consider, but this is one drawback of the string representation.","Q_Score":22,"Tags":"python,mysql,database,database-design","A_Id":1090132,"CreationDate":"2009-07-07T01:58:00.000","Title":"Drawbacks of storing an integer as a string in a database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have id values for products that I need store. Right now they are all integers, but I'm not sure if the data provider in the future will introduce letters or symbols into that mix, so I'm debating whether to store it now as integer or string.\nAre there performance or other disadvantages to saving the values as strings?","AnswerCount":10,"Available Count":8,"Score":1.0,"is_accepted":false,"ViewCount":10684,"Q_Id":1090022,"Users Score":18,"Answer":"Do NOT consider performance.  Consider meaning.\nID \"numbers\" are not numeric except that they are written with an alphabet of all digits.\nIf I have part number 12 and part number 14, what is the difference between the two?  Is part  number 2 or -2 meaningful?  No.\nPart numbers (and anything that doesn't have units of measure) are not \"numeric\".  They're just strings of digits.\nZip codes in the US, for example.  Phone numbers.  Social security numbers.  These are not numbers.  In my town the difference between zip code 12345 and 12309 isn't the distance from my house to downtown. \nDo not conflate numbers -- with units -- where sums and differences mean something with strings of digits without sums or differences.\nPart ID numbers are -- properly -- strings.  Not integers.  They'll never be integers because they don't have sums, differences or averages.","Q_Score":22,"Tags":"python,mysql,database,database-design","A_Id":1090100,"CreationDate":"2009-07-07T01:58:00.000","Title":"Drawbacks of storing an integer as a string in a database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am doing an application which will use multiple sqlite3 databases, prepopuldated with data from an external application. Each database will have the exact same tables, but with different data.\nI want to be able to switch between these databases according to user input. What is the most elegant way to do that in TurboGears 2?","AnswerCount":3,"Available Count":2,"Score":0.0665680765,"is_accepted":false,"ViewCount":163,"Q_Id":1093589,"Users Score":1,"Answer":"I am using two databases for a read-only application. The second database is a cache in case the primary database is down. I use two objects to hold the connection, metadata and compatible Table instances. The top of the view function assigns db = primary or db = secondary and the rest is just queries against db.tableA.join(db.tableB). I am not using the ORM.\nThe schemata are not strictly identical. The primary database needs a schema. prefix (Table(...schema='schema')) and the cache database does not. To get around this, I create my table objects in a function that takes the schema name as an argument. By calling the function once for each database, I wind up with compatible prefixed and non-prefixed Table objects.\nAt least in Pylons, the SQLAlchemy meta.Session is a ScopedSession. The application's BaseController in appname\/lib\/base.py calls Session.remove() after each request. It's probably better to have a single Session that talks to both databases, but if you don't you may need to modify your BaseController to call .remove() on each Session.","Q_Score":1,"Tags":"python,sqlite,turbogears,turbogears2","A_Id":1422838,"CreationDate":"2009-07-07T17:14:00.000","Title":"Switching databases in TG2 during runtime","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am doing an application which will use multiple sqlite3 databases, prepopuldated with data from an external application. Each database will have the exact same tables, but with different data.\nI want to be able to switch between these databases according to user input. What is the most elegant way to do that in TurboGears 2?","AnswerCount":3,"Available Count":2,"Score":0.0665680765,"is_accepted":false,"ViewCount":163,"Q_Id":1093589,"Users Score":1,"Answer":"If ALL databases have the same schema then you should be able to create several Sessions using the same model to the different DBs.","Q_Score":1,"Tags":"python,sqlite,turbogears,turbogears2","A_Id":1387164,"CreationDate":"2009-07-07T17:14:00.000","Title":"Switching databases in TG2 during runtime","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"My specific situation\nProperty management web site where users can upload photos and lease documents.  For every apartment unit, there might be 4 photos, so there won't be an overwhelming number of photo in the system.  \nFor photos, there will be thumbnails of each.\nMy question\nMy #1 priority is performance.  For the end user, I want to load pages and show the image as fast as possible.  \nShould I store the images inside the database, or file system, or doesn't matter?  Do I need to be caching anything?\nThanks in advance!","AnswerCount":6,"Available Count":4,"Score":0.0333209931,"is_accepted":false,"ViewCount":7730,"Q_Id":1105429,"Users Score":1,"Answer":"a DB might be faster than a filesystem on some operations, but loading a well-identified chunk of data 100s of KB is not one of them.\nalso, a good frontend webserver (like nginx) is way faster than any webapp layer you'd have to write to read the blob from the DB.  in some tests nginx is roughly on par with memcached for raw data serving of medium-sized files (like big HTMLs or medium-sized images).\ngo FS.  no contest.","Q_Score":11,"Tags":"python,postgresql,storage,photos,photo-management","A_Id":1105534,"CreationDate":"2009-07-09T17:39:00.000","Title":"storing uploaded photos and documents - filesystem vs database blob","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"My specific situation\nProperty management web site where users can upload photos and lease documents.  For every apartment unit, there might be 4 photos, so there won't be an overwhelming number of photo in the system.  \nFor photos, there will be thumbnails of each.\nMy question\nMy #1 priority is performance.  For the end user, I want to load pages and show the image as fast as possible.  \nShould I store the images inside the database, or file system, or doesn't matter?  Do I need to be caching anything?\nThanks in advance!","AnswerCount":6,"Available Count":4,"Score":1.0,"is_accepted":false,"ViewCount":7730,"Q_Id":1105429,"Users Score":9,"Answer":"File system. No contest.\nThe data has to go through a lot more layers when you store it in the db.\nEdit on caching:\nIf you want to cache the file while the user uploads it to ensure the operation finishes as soon as possible, dumping it straight to disk (i.e. file system) is about as quick as it gets. As long as the files aren't too big and you don't have too many concurrent users, you can 'cache' the file in memory, return to the user, then save to disk. To be honest, I wouldn't bother.\nIf you are making the files available on the web after they have been uploaded and want to cache to improve the performance, file system is still the best option. You'll get caching for free (may have to adjust a setting or two) from your web server. You wont get this if the files are in the database.\nAfter all that it sounds like you should never store files in the database. Not the case, you just need a good reason to do so.","Q_Score":11,"Tags":"python,postgresql,storage,photos,photo-management","A_Id":1105444,"CreationDate":"2009-07-09T17:39:00.000","Title":"storing uploaded photos and documents - filesystem vs database blob","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"My specific situation\nProperty management web site where users can upload photos and lease documents.  For every apartment unit, there might be 4 photos, so there won't be an overwhelming number of photo in the system.  \nFor photos, there will be thumbnails of each.\nMy question\nMy #1 priority is performance.  For the end user, I want to load pages and show the image as fast as possible.  \nShould I store the images inside the database, or file system, or doesn't matter?  Do I need to be caching anything?\nThanks in advance!","AnswerCount":6,"Available Count":4,"Score":0.0996679946,"is_accepted":false,"ViewCount":7730,"Q_Id":1105429,"Users Score":3,"Answer":"Definitely store your images on the filesystem.  One concern that folks don't consider enough when considering these types of things is bloat; cramming images as binary blobs into your database is a really quick way to bloat your DB way up.  With a large database comes higher hardware requirements, more difficult replication and backup requirements, etc.  Sticking your images on a filesystem means you can back them up \/ replicate them with many existing tools easily and simply.  Storage space is far easier to increase on filesystem than in database, as well.","Q_Score":11,"Tags":"python,postgresql,storage,photos,photo-management","A_Id":1105479,"CreationDate":"2009-07-09T17:39:00.000","Title":"storing uploaded photos and documents - filesystem vs database blob","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"My specific situation\nProperty management web site where users can upload photos and lease documents.  For every apartment unit, there might be 4 photos, so there won't be an overwhelming number of photo in the system.  \nFor photos, there will be thumbnails of each.\nMy question\nMy #1 priority is performance.  For the end user, I want to load pages and show the image as fast as possible.  \nShould I store the images inside the database, or file system, or doesn't matter?  Do I need to be caching anything?\nThanks in advance!","AnswerCount":6,"Available Count":4,"Score":1.0,"is_accepted":false,"ViewCount":7730,"Q_Id":1105429,"Users Score":10,"Answer":"While there are exceptions to everything, the general case is that storing images in the file system is your best bet. You can easily provide caching services to the images, you don't need to worry about additional code to handle image processing, and you can easily do maintenance on the images if needed through standard image editing methods.\nIt sounds like your business model fits nicely into this scenario.","Q_Score":11,"Tags":"python,postgresql,storage,photos,photo-management","A_Id":1105453,"CreationDate":"2009-07-09T17:39:00.000","Title":"storing uploaded photos and documents - filesystem vs database blob","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"We've got a healthy debate going on in the office this week. We're creating a Db to store proxy information, for the most part we have the schema worked out except for how we should store IPs. One camp wants to use 4 smallints, one for each octet and the other wants to use a 1 big int,INET_ATON.\nThese tables are going to be huge so performance is key. I am in middle here as I normally use MS SQL and 4 small ints in my world. I don't have enough experience with this type of volume storing IPs. \nWe'll be using perl and python scripts to access the database to further normalize the data into several other tables for top talkers, interesting traffic etc.\nI am sure there are some here in the community that have done something simular to what we are doing and I am interested in hearing about their experiences and which route is best, 1 big int, or 4 small ints for IP addresses.\nEDIT - One of our concerns is space, this database is going to be huge like in 500,000,000 records a day. So we are trying to weigh the space issue along with the performance issue.\nEDIT 2 Some of the conversation has turned over to the volume of data we are going to store...that's not my question. The question is which is the preferable way to store an IP address and why. Like I've said in my comments, we work for a large fortune 50 company. Our log files contain usage data from our users. This data in turn will be used within a security context to drive some metrics and to drive several security tools.","AnswerCount":7,"Available Count":3,"Score":0.057080742,"is_accepted":false,"ViewCount":14213,"Q_Id":1108918,"Users Score":2,"Answer":"for both ipv4 and ipv6 compatibility, use VARBINARY(16) , ipv4's will always be BINARY(4) and ipv6 will always be BINARY(16), so VARBINARY(16) seems like the most efficient way to support both. and to convert them from the normal readable format to binary, use INET6_ATON('127.0.0.1'), and to reverse that, use INET6_NTOA(binary)","Q_Score":25,"Tags":"python,mysql,perl,ip-address","A_Id":59109834,"CreationDate":"2009-07-10T10:58:00.000","Title":"How to store an IP in mySQL","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"We've got a healthy debate going on in the office this week. We're creating a Db to store proxy information, for the most part we have the schema worked out except for how we should store IPs. One camp wants to use 4 smallints, one for each octet and the other wants to use a 1 big int,INET_ATON.\nThese tables are going to be huge so performance is key. I am in middle here as I normally use MS SQL and 4 small ints in my world. I don't have enough experience with this type of volume storing IPs. \nWe'll be using perl and python scripts to access the database to further normalize the data into several other tables for top talkers, interesting traffic etc.\nI am sure there are some here in the community that have done something simular to what we are doing and I am interested in hearing about their experiences and which route is best, 1 big int, or 4 small ints for IP addresses.\nEDIT - One of our concerns is space, this database is going to be huge like in 500,000,000 records a day. So we are trying to weigh the space issue along with the performance issue.\nEDIT 2 Some of the conversation has turned over to the volume of data we are going to store...that's not my question. The question is which is the preferable way to store an IP address and why. Like I've said in my comments, we work for a large fortune 50 company. Our log files contain usage data from our users. This data in turn will be used within a security context to drive some metrics and to drive several security tools.","AnswerCount":7,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":14213,"Q_Id":1108918,"Users Score":0,"Answer":"Old thread, but for the benefit of readers, consider using ip2long. It translates ip into an integer. \nBasically, you will be converting with ip2long when storing into DB then converting back with long2ip when retrieving from DB. The field type in DB will INT, so you will save space and gain better performance compared to storing ip as a string.","Q_Score":25,"Tags":"python,mysql,perl,ip-address","A_Id":56818264,"CreationDate":"2009-07-10T10:58:00.000","Title":"How to store an IP in mySQL","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"We've got a healthy debate going on in the office this week. We're creating a Db to store proxy information, for the most part we have the schema worked out except for how we should store IPs. One camp wants to use 4 smallints, one for each octet and the other wants to use a 1 big int,INET_ATON.\nThese tables are going to be huge so performance is key. I am in middle here as I normally use MS SQL and 4 small ints in my world. I don't have enough experience with this type of volume storing IPs. \nWe'll be using perl and python scripts to access the database to further normalize the data into several other tables for top talkers, interesting traffic etc.\nI am sure there are some here in the community that have done something simular to what we are doing and I am interested in hearing about their experiences and which route is best, 1 big int, or 4 small ints for IP addresses.\nEDIT - One of our concerns is space, this database is going to be huge like in 500,000,000 records a day. So we are trying to weigh the space issue along with the performance issue.\nEDIT 2 Some of the conversation has turned over to the volume of data we are going to store...that's not my question. The question is which is the preferable way to store an IP address and why. Like I've said in my comments, we work for a large fortune 50 company. Our log files contain usage data from our users. This data in turn will be used within a security context to drive some metrics and to drive several security tools.","AnswerCount":7,"Available Count":3,"Score":0.0855049882,"is_accepted":false,"ViewCount":14213,"Q_Id":1108918,"Users Score":3,"Answer":"Having seperate fields doesn't sound particularly sensible to me - much like splitting a zipcode into sections or a phone number.\nMight be useful if you wanted specific info on the sections, but I see no real reason to not use a 32 bit int.","Q_Score":25,"Tags":"python,mysql,perl,ip-address","A_Id":1109278,"CreationDate":"2009-07-10T10:58:00.000","Title":"How to store an IP in mySQL","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"HI \uff0c I made a ICAPServer (similar with httpserver) for which the performance is very important.\nThe DB module is sqlalchemy.\nI then made a test about the performance of sqlalchemy, as a result, i found that it takes about 30ms for sqlalchemy to write <50kb data to DB (Oracle), i don`t know if the result is normal, or i did something wrong?\nBUT, no matter right or wrong, it seems the bottle-neck comes from the DB part.\nHOW can i improve the performance of sqlalchemy? OR it is up to DBA to improve Oracle?\nBTW, ICAPServer and Oracle are on the same pc , and i used the essential way of sqlalchemy..","AnswerCount":3,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":4462,"Q_Id":1110805,"Users Score":1,"Answer":"I had some issues with sqlalchemy's performance as well - I think you should first figure out in which ways you are using it ... they recommend that for big data sets is better to use the sql expression language. Either ways try and optimize the sqlalchemy code and have the Oracle database optimized as well, so you can better figure out what's wrong.\nAlso, do some tests on the database.","Q_Score":1,"Tags":"python,sqlalchemy","A_Id":1110990,"CreationDate":"2009-07-10T17:16:00.000","Title":"python sqlalchemy performance?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"HI \uff0c I made a ICAPServer (similar with httpserver) for which the performance is very important.\nThe DB module is sqlalchemy.\nI then made a test about the performance of sqlalchemy, as a result, i found that it takes about 30ms for sqlalchemy to write <50kb data to DB (Oracle), i don`t know if the result is normal, or i did something wrong?\nBUT, no matter right or wrong, it seems the bottle-neck comes from the DB part.\nHOW can i improve the performance of sqlalchemy? OR it is up to DBA to improve Oracle?\nBTW, ICAPServer and Oracle are on the same pc , and i used the essential way of sqlalchemy..","AnswerCount":3,"Available Count":2,"Score":0.0665680765,"is_accepted":false,"ViewCount":4462,"Q_Id":1110805,"Users Score":1,"Answer":"You can only push SQLAlchemy so far as a programmer. I would agree with you that the rest of the performance is up to your DBA, including creating proper indexes on tables, etc.","Q_Score":1,"Tags":"python,sqlalchemy","A_Id":1110888,"CreationDate":"2009-07-10T17:16:00.000","Title":"python sqlalchemy performance?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I would like to insert a calculation in Excel using Python.\nGenerally it can be done by inserting a formula string into the relevant cell.\nHowever, if i need to calculate a formula multiple times for the whole column\nthe formula must be updated for each individual cell. For example, if i need to \ncalculate the sum of two cells, then for cell C(k) the computation would be A(k)+B(k).\nIn excel it is possible to calculate C1=A1+B1 and then automatically expand the \ncalculation by dragging the mouse from C1 downwards.\nMy question is: Is it possible to the same thing with Python, i.e. to define a formula in only one cell and then to use Excel capabilities to extend the calculation for the whole column\/row?\nThank you in advance,\nSasha","AnswerCount":6,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":12592,"Q_Id":1116725,"Users Score":0,"Answer":"If you are using COM bindings, then you can simply record a macro in Excel, then translate it into Python code.\nIf you are using xlwt, you have to resort to normal loops in python..","Q_Score":1,"Tags":"python,excel,formula","A_Id":1116782,"CreationDate":"2009-07-12T19:36:00.000","Title":"Calculating formulae in Excel with Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"HI\uff0ci got a multi-threading program which all threads will operate on oracle\nDB. So, can sqlalchemy support parallel operation on oracle?\ntks!","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":2195,"Q_Id":1117538,"Users Score":1,"Answer":"As long as each concurrent thread has it's own session you should be fine. Trying to use one shared session is where you'll get into trouble.","Q_Score":0,"Tags":"python,sqlalchemy","A_Id":1117592,"CreationDate":"2009-07-13T02:44:00.000","Title":"python sqlalchemy parallel operation","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Just starting to get to grips with python and MySQLdb and was wondering\n\nWhere is the best play to put a try\/catch block for the connection to MySQL. At the MySQLdb.connect point? Also should there be one when ever i query?\nWhat exceptions should i be catching on any of these blocks?\n\nthanks for any help\nCheers\nMark","AnswerCount":2,"Available Count":2,"Score":0.0996679946,"is_accepted":false,"ViewCount":5063,"Q_Id":1117828,"Users Score":1,"Answer":"I think that the connections and the query can raised errors so you should have try\/excepy for both of them.","Q_Score":9,"Tags":"python,mysql,exception","A_Id":1117841,"CreationDate":"2009-07-13T05:31:00.000","Title":"Python MySQLdb exceptions","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Just starting to get to grips with python and MySQLdb and was wondering\n\nWhere is the best play to put a try\/catch block for the connection to MySQL. At the MySQLdb.connect point? Also should there be one when ever i query?\nWhat exceptions should i be catching on any of these blocks?\n\nthanks for any help\nCheers\nMark","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":5063,"Q_Id":1117828,"Users Score":16,"Answer":"Catch the MySQLdb.Error, while connecting and while executing query","Q_Score":9,"Tags":"python,mysql,exception","A_Id":1118129,"CreationDate":"2009-07-13T05:31:00.000","Title":"Python MySQLdb exceptions","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm developing a web application and considering Django, Google App Engine, and several other options. I wondered what kind of \"penalty\" I will incur if I develop a complete Django application assuming it runs on a dedicated server, and then later want to migrate it to Google App Engine.\nI have a basic understanding of Google's data store, so please assume I will choose a column based database for my \"stand-alone\" Django application rather than a relational database, so that the schema could remain mostly the same and will not be a major factor.\nAlso, please assume my application does not maintain a huge amount of data, so that migration of tens of gigabytes is not required. I'm mainly interested in the effects on the code and software architecture.\nThanks","AnswerCount":4,"Available Count":2,"Score":0.049958375,"is_accepted":false,"ViewCount":1845,"Q_Id":1118761,"Users Score":1,"Answer":"There are a few things that you can't do on the App Engine that you can do on your own server like uploading of files. On the App Engine you kinda have to upload it and store the datastore which can cause a few problems.\nOther than that it should be fine from the Presentation part. There are a number of other little things that are better on your own dedicated server but I think eventually a lot of those things will be in the App Engine","Q_Score":9,"Tags":"python,django,google-app-engine","A_Id":1118790,"CreationDate":"2009-07-13T10:40:00.000","Title":"Migrating Django Application to Google App Engine?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I'm developing a web application and considering Django, Google App Engine, and several other options. I wondered what kind of \"penalty\" I will incur if I develop a complete Django application assuming it runs on a dedicated server, and then later want to migrate it to Google App Engine.\nI have a basic understanding of Google's data store, so please assume I will choose a column based database for my \"stand-alone\" Django application rather than a relational database, so that the schema could remain mostly the same and will not be a major factor.\nAlso, please assume my application does not maintain a huge amount of data, so that migration of tens of gigabytes is not required. I'm mainly interested in the effects on the code and software architecture.\nThanks","AnswerCount":4,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":1845,"Q_Id":1118761,"Users Score":8,"Answer":"Most (all?) of Django is available in GAE, so your main task is to avoid basing your designs around a reliance on anything from Django or the Python standard libraries which is not available on GAE.\nYou've identified the glaring difference, which is the database, so I'll assume you're on top of that. Another difference is the tie-in to Google Accounts and hence that if you want, you can do a fair amount of access control through the app.yaml file rather than in code. You don't have to use any of that, though, so if you don't envisage switching to Google Accounts when you switch to GAE, no problem.\nI think the differences in the standard libraries can mostly be deduced from the fact that GAE has no I\/O and no C-accelerated libraries unless explicitly stated, and my experience so far is that things I've expected to be there, have been there. I don't know Django and haven't used it on GAE (apart from templates), so I can't comment on that.\nPersonally I probably wouldn't target LAMP (where P = Django) with the intention of migrating to GAE later. I'd develop for both together, and try to ensure if possible that the differences are kept to the very top (configuration) and the very bottom (data model). The GAE version doesn't necessarily have to be perfect, as long as you know how to make it perfect should you need it.\nIt's not guaranteed that this is faster than writing and then porting, but my guess is it normally will be. The easiest way to spot any differences is to run the code, rather than relying on not missing anything in the GAE docs, so you'll likely save some mistakes that need to be unpicked. The Python SDK is a fairly good approximation to the real App Engine, so all or most of your tests can be run locally most of the time.\nOf course if you eventually decide not to port then you've done unnecessary work, so you have to think about the probability of that happening, and whether you'd consider the GAE development to be a waste of your time if it's not needed.","Q_Score":9,"Tags":"python,django,google-app-engine","A_Id":1119377,"CreationDate":"2009-07-13T10:40:00.000","Title":"Migrating Django Application to Google App Engine?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I am using Python 2.6.1, MySQL4.0 in Windows platform and I have successfully installed MySQLdb.\nDo we need to set any path for my python code and MySQLdb to successful run my application? Without any setting paths (in my code I am importing MySQLdb) I am getting No module named MySQLdb error is coming and I am not able to move further.","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":770,"Q_Id":1136676,"Users Score":0,"Answer":"How did you install MySQLdb? This sounds like your MySQLdb module is not within your PYTHONPATH which indicates some inconsistancy between how you installed Python itself and how you installed MySQLdb.\nOr did you perhaps install a MySQLdb binary that was not targeted for your version of Python? Modules are normally put into version-dependant folders.","Q_Score":1,"Tags":"python,mysql","A_Id":1136692,"CreationDate":"2009-07-16T10:20:00.000","Title":"is it required to give path after installation MySQL db for Python 2.6","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Has anyone used SQLAlchemy in addition to Django's ORM?\nI'd like to use Django's ORM for object manipulation and SQLalchemy for complex queries (like those that require left outer joins). \nIs it possible?\nNote: I'm aware about django-sqlalchemy but the project doesn't seem to be production ready.","AnswerCount":5,"Available Count":3,"Score":0.1586485043,"is_accepted":false,"ViewCount":12511,"Q_Id":1154331,"Users Score":4,"Answer":"Jacob Kaplan-Moss admitted to typing \"import sqlalchemy\" from time to time.  I may write a queryset adapter for sqlalchemy results in the not too distant future.","Q_Score":23,"Tags":"python,database,django,sqlalchemy","A_Id":1308718,"CreationDate":"2009-07-20T15:44:00.000","Title":"SQLAlchemy and django, is it production ready?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Has anyone used SQLAlchemy in addition to Django's ORM?\nI'd like to use Django's ORM for object manipulation and SQLalchemy for complex queries (like those that require left outer joins). \nIs it possible?\nNote: I'm aware about django-sqlalchemy but the project doesn't seem to be production ready.","AnswerCount":5,"Available Count":3,"Score":1.2,"is_accepted":true,"ViewCount":12511,"Q_Id":1154331,"Users Score":19,"Answer":"What I would do,\n\nDefine the schema in Django orm, let it write the db via syncdb. You get the admin interface.\nIn view1 you need a complex join\n\n\n\n    def view1(request):\n       import sqlalchemy\n       data = sqlalchemy.complex_join_magic(...)\n       ...\n       payload = {'data': data, ...}\n       return render_to_response('template', payload, ...)","Q_Score":23,"Tags":"python,database,django,sqlalchemy","A_Id":1155407,"CreationDate":"2009-07-20T15:44:00.000","Title":"SQLAlchemy and django, is it production ready?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Has anyone used SQLAlchemy in addition to Django's ORM?\nI'd like to use Django's ORM for object manipulation and SQLalchemy for complex queries (like those that require left outer joins). \nIs it possible?\nNote: I'm aware about django-sqlalchemy but the project doesn't seem to be production ready.","AnswerCount":5,"Available Count":3,"Score":1.0,"is_accepted":false,"ViewCount":12511,"Q_Id":1154331,"Users Score":7,"Answer":"I've done it before and it's fine.  Use the SQLAlchemy feature where it can read in the schema so you don't need to declare your fields twice.\nYou can grab the connection settings from the settings, the only problem is stuff like the different flavours of postgres driver (e.g. with psyco and without).\nIt's worth it as the SQLAlchemy stuff is just so much nicer for stuff like joins.","Q_Score":23,"Tags":"python,database,django,sqlalchemy","A_Id":3555602,"CreationDate":"2009-07-20T15:44:00.000","Title":"SQLAlchemy and django, is it production ready?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm modeling a database relationship in django, and I'd like to have other opinions. The relationship is kind of a two-to-many relationship. For example, a patient can have two physicians: an attending and a primary. A physician obviously has many patients.\nThe application does need to know which one is which; further, there are cases where an attending physician of one patient can be the primary of another. Lastly, both attending and primary are often the same. \nAt first, I was thinking two foreign keys from the patient table into the physician table. However, I think django disallows this. Additionally, on second thought, this is really a many(two)-to-many relationship.\nTherefore, how can I model this relationship with django while maintaining the physician type as it pertains to a patient? Perhaps I will need to store the physician type on the many-to-many association table?\nThanks,\nPete","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":358,"Q_Id":1162877,"Users Score":0,"Answer":"I agree with your conclusion. I would store the physician type in the many-to-many linking table.","Q_Score":2,"Tags":"python,database,django,database-design","A_Id":1162884,"CreationDate":"2009-07-22T03:05:00.000","Title":"How would you model this database relationship?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have to get the data from a User site. If I would work on their site, I would VPN and then remote into their server using username and password.\nI thought getting data into my local machine than getting into their server where my work is not secured.\nSo, I thought of using Ironpython to get data from the remote server. \nSo, I still VPN'd to their domain, but when I was using the ADO.net connection string to connect to their database, it does not work.\nconnection string:\nData Source=xx.xx.xx.xx;Initial Catalog=;User ID=;Password=;\nand the error says:\nlogin failed for \nWell, one thing to notice is: when  i remote into their server, I provide username and password once. Then when i log on to SQL Server, I dont have to provide username and password. It s windows authenticated. So, in the above connection string, I used the same username and password that I use while remoting in. I hope this gives an idea to ya'll what i might be missing. \nHelp appreciated!!!","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":1035,"Q_Id":1169668,"Users Score":0,"Answer":"Data Source=xx.xx.xx.xx;Initial Catalog=;Integrated Security=\"SSPI\"\nHow are you connecting to SQL.  Do you use sql server authentication or windows authentication?  Once you know that, then if you use a DNS name or IP that will go to the server correctly, you have the instance name correct AND you have permissions on the account to access the server you can connect.\nHeres a quick test.  From the system you are using to connect to your SQL Server with, can you open the SQL Server management studio and connect to the remote database.  If you can, tell me what settings you needed to do that, and I'll give you a connection string that will work.","Q_Score":0,"Tags":".net,ado.net,ironpython,connection-string","A_Id":1169704,"CreationDate":"2009-07-23T04:52:00.000","Title":"need help on ADO.net connection string","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have to get the data from a User site. If I would work on their site, I would VPN and then remote into their server using username and password.\nI thought getting data into my local machine than getting into their server where my work is not secured.\nSo, I thought of using Ironpython to get data from the remote server. \nSo, I still VPN'd to their domain, but when I was using the ADO.net connection string to connect to their database, it does not work.\nconnection string:\nData Source=xx.xx.xx.xx;Initial Catalog=;User ID=;Password=;\nand the error says:\nlogin failed for \nWell, one thing to notice is: when  i remote into their server, I provide username and password once. Then when i log on to SQL Server, I dont have to provide username and password. It s windows authenticated. So, in the above connection string, I used the same username and password that I use while remoting in. I hope this gives an idea to ya'll what i might be missing. \nHelp appreciated!!!","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":1035,"Q_Id":1169668,"Users Score":0,"Answer":"Is that user granted login abilities in SQL?\nIf using SQL 2005, you go to Security->Logins\nDouble click the user, and click Status.\n------Edit ----\nCreate a file on your desktop called TEST.UDL.  Double click it.\nsetup your connection until it works.\nView the UDL in notepad,  there's your connection string.  Though I think you take out the first part which includes provider info.","Q_Score":0,"Tags":".net,ado.net,ironpython,connection-string","A_Id":1169755,"CreationDate":"2009-07-23T04:52:00.000","Title":"need help on ADO.net connection string","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm trying to make a web app that will manage my Mercurial repositories for me.\nI want it so that when I tell it to load repository X:\n\nConnect to a MySQL server and make sure X exists.\nCheck if the user is allowed to access the repository.\nIf above is true, get the location of X from a mysql server.\nRun a hgweb cgi script (python) containing the path of the repository.\n\nHere is the problem, I want to: take the hgweb script, modify it, and run it.\nBut I do not want to: take the hgweb script, modify it, write it to a file and redirect there.\nI am using Apache to run the httpd process.","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":940,"Q_Id":1185867,"Users Score":0,"Answer":"As far as you question, no, you're not likely to get php to execute a modified script without writing it somewhere, whether that's a file on the disk, a virtual file mapped to ram, or something similar.\nIt sounds like you might be trying to pound a railroad spike with a twig. If you're to the point where you're filtering access based on user permissions stored in MySQL, have you looked at existing HG solutions to make sure there isn't something more applicable than hgweb? It's really built for doing exactly one thing well, and this is a fair bit beyond it's normal realm.\nI might suggest looking into apache's native authentication as a more convenient method for controlling access to repositories, then just serve the repo without modifying the script.","Q_Score":0,"Tags":"php,python,mercurial,cgi","A_Id":1185909,"CreationDate":"2009-07-26T23:24:00.000","Title":"How can I execute CGI files from PHP?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm considering the idea of creating a persistent storage like a dbms engine, what would be the benefits to create a custom binary format over directly cPickling the object and\/or using the shelve module?","AnswerCount":7,"Available Count":4,"Score":0.0285636566,"is_accepted":false,"ViewCount":1116,"Q_Id":1188585,"Users Score":1,"Answer":"The potential advantages of a custom format over a pickle are:\n\nyou can selectively get individual objects, rather than having to incarnate the full set of objects\nyou can query subsets of objects by properties, and only load those objects that match your criteria\n\nWhether these advantages materialize depends on how you design the storage, of course.","Q_Score":5,"Tags":"python,database,data-structures,persistence","A_Id":1188711,"CreationDate":"2009-07-27T14:45:00.000","Title":"What are the benefits of not using cPickle to create a persistent storage for data?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm considering the idea of creating a persistent storage like a dbms engine, what would be the benefits to create a custom binary format over directly cPickling the object and\/or using the shelve module?","AnswerCount":7,"Available Count":4,"Score":1.2,"is_accepted":true,"ViewCount":1116,"Q_Id":1188585,"Users Score":10,"Answer":"Pickling is a two-face coin.\nOn one side, you have a way to store your object in a very easy way. Just four lines of code and you pickle. You have the object exactly as it is.\nOn the other side, it can become a compatibility nightmare. You cannot unpickle objects if they are not defined in your code, exactly as they were defined when pickled. This strongly limits your ability to refactor the code, or rearrange stuff in your modules.\nAlso, not everything can be pickled, and if you are not strict on what gets pickled and the client of your code has full freedom of including any object, sooner or later it will pass something unpicklable to your system, and the system will go boom.\nBe very careful about its use. there's no better definition of quick and dirty.","Q_Score":5,"Tags":"python,database,data-structures,persistence","A_Id":1188704,"CreationDate":"2009-07-27T14:45:00.000","Title":"What are the benefits of not using cPickle to create a persistent storage for data?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm considering the idea of creating a persistent storage like a dbms engine, what would be the benefits to create a custom binary format over directly cPickling the object and\/or using the shelve module?","AnswerCount":7,"Available Count":4,"Score":0.057080742,"is_accepted":false,"ViewCount":1116,"Q_Id":1188585,"Users Score":2,"Answer":"Note that not all objects may be directly pickled - only basic types, or objects that have defined the pickle protocol.\nUsing your own binary format would allow you to potentially store any kind of object.\nJust for note, Zope Object DB (ZODB) is following that very same approach, storing objects with the Pickle format. You may be interested in getting their implementations.","Q_Score":5,"Tags":"python,database,data-structures,persistence","A_Id":1188679,"CreationDate":"2009-07-27T14:45:00.000","Title":"What are the benefits of not using cPickle to create a persistent storage for data?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm considering the idea of creating a persistent storage like a dbms engine, what would be the benefits to create a custom binary format over directly cPickling the object and\/or using the shelve module?","AnswerCount":7,"Available Count":4,"Score":0.0,"is_accepted":false,"ViewCount":1116,"Q_Id":1188585,"Users Score":0,"Answer":"Will you ever need to process data from untrusted sources?  If so, you should know that the pickle format is actually a virtual machine that is capable of executing arbitrary code on behalf of the process doing the unpickling.","Q_Score":5,"Tags":"python,database,data-structures,persistence","A_Id":1189928,"CreationDate":"2009-07-27T14:45:00.000","Title":"What are the benefits of not using cPickle to create a persistent storage for data?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm developing an app that handle sets of financial series data (input as csv or open document), one set could be say 10's x 1000's up to double precision numbers (Simplifying, but thats what matters).\nI plan to do operations on that data (eg. sum, difference, averages etc.) as well including generation of say another column based on computations on the input. This will be between columns (row level operations) on one set and also between columns on many (potentially all) sets at the row level also. I plan to write it in Python and it will eventually need a intranet facing interface to display the results\/graphs etc. for now, csv output based on some input parameters will suffice.\nWhat is the best way to store the data and manipulate? So far I see my choices as being either (1) to write csv files to disk and trawl through them to do the math or (2) I could put them into a database and rely on the database to handle the math. My main concern is speed\/performance as the number of datasets grows as there will be inter-dataset row level math that needs to be done.\n-Has anyone had experience going down either path and what are the pitfalls\/gotchas that I should be aware of?\n-What are the reasons why one should be chosen over another? \n-Are there any potential speed\/performance pitfalls\/boosts that I need to be aware of before I start that could influence the design?\n-Is there any project or framework out there to help with this type of task? \n-Edit-\nMore info:\nThe rows will all read all in order, BUT I may need to do some resampling\/interpolation to match the differing input lengths as well as differing timestamps for each row. Since each dataset will always have a differing length that is not fixed, I'll have some scratch table\/memory somewhere to hold the interpolated\/resampled versions. I'm not sure if it makes more sense to try to store this (and try to upsample\/interploate to a common higher length) or just regenerate it each time its needed.","AnswerCount":4,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":581,"Q_Id":1241758,"Users Score":0,"Answer":"Are you likely to need all rows in order or will you want only specific known rows?\nIf you need to read all the data there isn't much advantage to having it in a database.\nedit: If the code fits in memory then a simple CSV is fine. Plain text data formats are always easier to deal with than opaque ones if you can use them.","Q_Score":0,"Tags":"python,database,database-design,file-io","A_Id":1241784,"CreationDate":"2009-08-06T21:58:00.000","Title":"Store data series in file or database if I want to do row level math operations?","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm developing an app that handle sets of financial series data (input as csv or open document), one set could be say 10's x 1000's up to double precision numbers (Simplifying, but thats what matters).\nI plan to do operations on that data (eg. sum, difference, averages etc.) as well including generation of say another column based on computations on the input. This will be between columns (row level operations) on one set and also between columns on many (potentially all) sets at the row level also. I plan to write it in Python and it will eventually need a intranet facing interface to display the results\/graphs etc. for now, csv output based on some input parameters will suffice.\nWhat is the best way to store the data and manipulate? So far I see my choices as being either (1) to write csv files to disk and trawl through them to do the math or (2) I could put them into a database and rely on the database to handle the math. My main concern is speed\/performance as the number of datasets grows as there will be inter-dataset row level math that needs to be done.\n-Has anyone had experience going down either path and what are the pitfalls\/gotchas that I should be aware of?\n-What are the reasons why one should be chosen over another? \n-Are there any potential speed\/performance pitfalls\/boosts that I need to be aware of before I start that could influence the design?\n-Is there any project or framework out there to help with this type of task? \n-Edit-\nMore info:\nThe rows will all read all in order, BUT I may need to do some resampling\/interpolation to match the differing input lengths as well as differing timestamps for each row. Since each dataset will always have a differing length that is not fixed, I'll have some scratch table\/memory somewhere to hold the interpolated\/resampled versions. I'm not sure if it makes more sense to try to store this (and try to upsample\/interploate to a common higher length) or just regenerate it each time its needed.","AnswerCount":4,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":581,"Q_Id":1241758,"Users Score":0,"Answer":"What matters most if all data will fit simultaneously into memory. From the size that you give, it seems that this is easily the case (a few megabytes at worst).\nIf so, I would discourage using a relational database, and do all operations directly in Python. Depending on what other processing you need, I would probably rather use binary pickles, than CSV.","Q_Score":0,"Tags":"python,database,database-design,file-io","A_Id":1241787,"CreationDate":"2009-08-06T21:58:00.000","Title":"Store data series in file or database if I want to do row level math operations?","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm developing an app that handle sets of financial series data (input as csv or open document), one set could be say 10's x 1000's up to double precision numbers (Simplifying, but thats what matters).\nI plan to do operations on that data (eg. sum, difference, averages etc.) as well including generation of say another column based on computations on the input. This will be between columns (row level operations) on one set and also between columns on many (potentially all) sets at the row level also. I plan to write it in Python and it will eventually need a intranet facing interface to display the results\/graphs etc. for now, csv output based on some input parameters will suffice.\nWhat is the best way to store the data and manipulate? So far I see my choices as being either (1) to write csv files to disk and trawl through them to do the math or (2) I could put them into a database and rely on the database to handle the math. My main concern is speed\/performance as the number of datasets grows as there will be inter-dataset row level math that needs to be done.\n-Has anyone had experience going down either path and what are the pitfalls\/gotchas that I should be aware of?\n-What are the reasons why one should be chosen over another? \n-Are there any potential speed\/performance pitfalls\/boosts that I need to be aware of before I start that could influence the design?\n-Is there any project or framework out there to help with this type of task? \n-Edit-\nMore info:\nThe rows will all read all in order, BUT I may need to do some resampling\/interpolation to match the differing input lengths as well as differing timestamps for each row. Since each dataset will always have a differing length that is not fixed, I'll have some scratch table\/memory somewhere to hold the interpolated\/resampled versions. I'm not sure if it makes more sense to try to store this (and try to upsample\/interploate to a common higher length) or just regenerate it each time its needed.","AnswerCount":4,"Available Count":3,"Score":1.2,"is_accepted":true,"ViewCount":581,"Q_Id":1241758,"Users Score":2,"Answer":"\"I plan to do operations on that data (eg. sum, difference, averages etc.) as well including generation of say another column based on computations on the input.\"\nThis is the standard use case for a data warehouse star-schema design.  Buy Kimball's The Data Warehouse Toolkit.  Read (and understand) the star schema before doing anything else.\n\"What is the best way to store the data and manipulate?\"  \nA Star Schema.\nYou can implement this as flat files (CSV is fine) or RDBMS.  If you use flat files, you write simple loops to do the math.  If you use an RDBMS you write simple SQL and simple loops.  \n\"My main concern is speed\/performance as the number of datasets grows\" \nNothing is as fast as a flat file.  Period.  RDBMS is slower.  \nThe RDBMS value proposition stems from SQL being a relatively simple way to specify SELECT SUM(), COUNT() FROM fact JOIN dimension WHERE filter GROUP BY dimension attribute.  Python isn't as terse as SQL, but it's just as fast and just as flexible.  Python competes against SQL.\n\"pitfalls\/gotchas that I should be aware of?\"\nDB design.  If you don't get the star schema and how to separate facts from dimensions, all approaches are doomed.  Once you separate facts from dimensions, all approaches are approximately equal.\n\"What are the reasons why one should be chosen over another?\"\nRDBMS slow and flexible.  Flat files fast and (sometimes) less flexible.  Python levels the playing field.\n\"Are there any potential speed\/performance pitfalls\/boosts that I need to be aware of before I start that could influence the design?\"\nStar Schema:  central fact table surrounded by dimension tables.  Nothing beats it.\n\"Is there any project or framework out there to help with this type of task?\"\nNot really.","Q_Score":0,"Tags":"python,database,database-design,file-io","A_Id":1245169,"CreationDate":"2009-08-06T21:58:00.000","Title":"Store data series in file or database if I want to do row level math operations?","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm looking for the simplest way of using python and SQLAlchemy to produce some XML for a jQuery based HTTP client. Right now I'm using mod_python's CGI handler but I'm unhappy with the fact that I can't persist stuff like the SQLAlchemy session.\nThe mod_python publisher handler that is apparently capable of persisting stuff does not allow requests with XML content type (as used by jQuery's ajax stuff) so I can't use it.\nWhat other options are there?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1222,"Q_Id":1272325,"Users Score":2,"Answer":"You could always write your own handler, which is the way mod_python is normally intended to be used. You would have to set some HTTP headers (and you could have a look at the publisher handler's source code for inspiration on that), but otherwise I don't think it's much more complicated than what you've been trying to do.\nThough as long as you're at it, I would suggest trying mod_wsgi instead of mod_python, which is probably eventually going to supersede mod_python. WSGI is a Python standard for writing web applications.","Q_Score":2,"Tags":"python,cgi,mod-python","A_Id":1272579,"CreationDate":"2009-08-13T14:29:00.000","Title":"Alternatives to mod_python's CGI handler","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"What I really like about Entity framework is its drag and drop way of making up the whole model layer of your application. You select the tables, it joins them and you're done. If you update the database scheda, right click -> update and you're done again.\nThis seems to me miles ahead the competiting ORMs, like the mess of XML (n)Hibernate requires or the hard-to-update Django Models.\nWithout concentrating on the fact that maybe sometimes more control over the mapping process may be good, are there similar one-click (or one-command) solutions for other (mainly open source like python or php) programming languages or frameworks?\nThanks","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":433,"Q_Id":1283646,"Users Score":0,"Answer":"I have heard iBattis is good.  A few companies fall back to iBattis when their programmer teams are not capable of understanding Hibernate (time issue).\nPersonally, I still like Linq2Sql.  Yes, the first time someone needs to delete and redrag over a table seems like too much work, but it really is not.  And the time that it doesn't update your class code when you save is really a pain, but you simply control-a your tables and drag them over again.  Total remakes are very quick and painless.  The classes it creates are extremely simple.  You can even create multiple table entities if you like with SPs for CRUD.\nLinking SPs to CRUD is similar to EF: You simply setup your SP with the same parameters as your table, then drag it over your table, and poof, it matches the data types.\nA lot of people go out of their way to take IQueryable away from the repository, but you can limit what you link in linq2Sql, so IQueryable is not too bad.\nCome to think of it, I wonder if there is a way to restrict the relations (and foreign keys).","Q_Score":2,"Tags":"php,python,entity-framework,open-source","A_Id":1325558,"CreationDate":"2009-08-16T07:03:00.000","Title":"Entity Framwework-like ORM NOT for .NET","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I installed stackless pyton 2.6.2 after reading several sites that said its fully compatible with vanilla python. After installing i found that my django applications do not work any more.\nI did reinstall django (1.1) again and now im kind of lost. The error that i get is 500:\nInternal Server Error\nThe server encountered an internal error or misconfiguration and was unable to complete your request.\nPlease contact the server administrator, webmaster@localhost and inform them of the time the error occurred, and anything you might have done that may have caused the error.\nMore information about this error may be available in the server error log.\nApache\/2.2.11 (Ubuntu) DAV\/2 PHP\/5.2.6-3ubuntu4.1 with Suhosin-Patch mod_python\/3.3.1 Python\/2.6.2 mod_ruby\/1.2.6 Ruby\/1.8.7(2008-08-11) mod_ssl\/2.2.11 OpenSSL\/0.9.8g Server at 127.0.0.1 Port 80\nWhat else, could or should i do?\nEdit: From 1st comment i understand that the problem is not in django but mod_python & apache? so i edited my question title.\nEdit2: I think something is wrong with some paths setup. I tried going from mod_python to mod_wsgi, managed to finally set it up correctly only to get next error:\n[Sun Aug 16 12:38:22 2009] [error] [client 127.0.0.1]     raise ImproperlyConfigured(\"Error loading MySQLdb module: %s\" % e)\n[Sun Aug 16 12:38:22 2009] [error] [client 127.0.0.1] ImproperlyConfigured: Error loading MySQLdb module: No module named MySQLdb\nAlan","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":672,"Q_Id":1283856,"Users Score":2,"Answer":"When you install a new version of Python (whether stackless or not) you also need to reinstall all of the third party modules you need -- either from sources, which you say you don't want to do, or from packages built for the new version of Python you've just installed. \nSo, check the repository from which you installed Python 2.6.2 with aptitude: does it also have versions for that specific Python of mod_python, mysqldb, django, and any other third party stuff you may need?  There really is no \"silver bullet\" for package management and I know of no \"sumo distribution\" of Python bundling all the packages you could ever possibly need (if there were, it would have to be many 10s of GB;-).","Q_Score":0,"Tags":"python,mod-wsgi,mod-python,stackless,python-stackless","A_Id":1284586,"CreationDate":"2009-08-16T09:14:00.000","Title":"Stackless python stopped mod_python\/apache from working","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I want to write a python script that populates a database with some information.  One of the columns in my table is a BLOB that I would like to save a file to for each entry.\nHow can I read the file (binary) and insert it into the DB using python?  Likewise, how can I retrieve it and write that file back to some arbitrary location on the hard drive?","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":25537,"Q_Id":1294385,"Users Score":0,"Answer":"You can insert and read BLOBs from a DB like every other column type. From the database API's view there is nothing special about BLOBs.","Q_Score":15,"Tags":"python,mysql,file-io,blob","A_Id":1294488,"CreationDate":"2009-08-18T14:50:00.000","Title":"How to insert \/ retrieve a file stored as a BLOB in a MySQL db using python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am working on integrating with several music players. At the moment my favorite is exaile.\nIn the new version they are migrating the database format from SQLite3 to an internal Pickle format. I wanted to know if there is a way to access pickle format files without having to reverse engineer the format by hand.\nI know there is the cPickle python module, but I am unaware if it is callable directly from C.","AnswerCount":3,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":27544,"Q_Id":1296162,"Users Score":3,"Answer":"You can embed a Python interpreter in a C program, but I think that the easiest solution is to write a Python script that converts \"pickles\" in another format, e.g. an SQLite database.","Q_Score":23,"Tags":"python,c","A_Id":1296188,"CreationDate":"2009-08-18T20:02:00.000","Title":"How can I read a python pickle database\/file from C?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm running Django through mod_wsgi and Apache (2.2.8) on Ubuntu 8.04.\nI've been running Django on this setup for about 6 months without any problems.  Yesterday, I moved my database (postgres 8.3) to its own server, and my Django site started refusing to load (the browser spinner would just keep spinning).\nIt works for about 10 mintues, then just stops.  Apache is still able to serve static files.  Just nothing through Django.\nI've checked the apache error logs, and I don't see any entries that could be related.  I'm not sure if this is a WSGI, Django, Apache, or Postgres issue?\nAny ideas?\nThanks for your help!","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":435,"Q_Id":1300213,"Users Score":0,"Answer":"Found it! I'm using eventlet in some other code and I imported one of my modules into a django model. So eventlet was taking over and putting everything to \"sleep\".","Q_Score":1,"Tags":"python,django,postgresql,apache2,mod-wsgi","A_Id":2368542,"CreationDate":"2009-08-19T14:09:00.000","Title":"Apache\/Django freezing after a few requests","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have been working on a website using mod_python, python, and SQL Alchemy when I ran into a strange problem: When I query the database for all of the records, it returns the correct result set; however, when I refresh the page, it returns me a result set with that same result set appended to it. I get more result sets \"stacked\" on top of eachother as I refresh the page more.\nFor example:\nFirst page load: 10 results\nSecond page load: 20 results (two of each)\nThird page load: 30 results (three of each)\netc...\nIs this some underlying problem with mod_python? I don't recall running into this when using mod_wsgi.","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":192,"Q_Id":1301000,"Users Score":0,"Answer":"Not that I've ever heard of, but it's impossible to tell without some code to look at.\nMaybe you initialised your result set list as a global, or shared member, and then appended results to it when the application was called without resetting it to empty? A classic way of re-using lists accidentally is to put one in a default argument value to a function.    \n(The same could happen in mod_wsgi of course.)","Q_Score":0,"Tags":"python,sqlalchemy,mod-python","A_Id":1301029,"CreationDate":"2009-08-19T16:08:00.000","Title":"mod_python problem?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I've got Django set up to run some recurring tasks in their own threads, and I noticed that they were always leaving behind unfinished database connection processes (pgsql \"Idle In Transaction\").\nI looked through the Postgres logs and found that the transactions weren't being completed (no ROLLBACK). I tried using the various transaction decorators on my functions, no luck.\nI switched to manual transaction management and did the rollback manually, that worked, but still left the processes as \"Idle\".\nSo then I called connection.close(), and all is well.\nBut I'm left wondering, why doesn't Django's typical transaction and connection management work for these threaded tasks that are being spawned from the main Django thread?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":10095,"Q_Id":1303654,"Users Score":111,"Answer":"After weeks of testing and reading the Django source code, I've found the answer to my own question:\nTransactions\nDjango's default autocommit behavior still holds true for my threaded function. However, it states in the Django docs:\n\nAs soon as you perform an action that needs to write to the database, Django produces the INSERT\/UPDATE\/DELETE statements and then does the COMMIT. There\u2019s no implicit ROLLBACK.\n\nThat last sentence is very literal. It DOES NOT issue a ROLLBACK command unless something in Django has set the dirty flag. Since my function was only doing SELECT statements it never set the dirty flag and didn't trigger a COMMIT.\nThis goes against the fact that PostgreSQL thinks the transaction requires a ROLLBACK because Django issued a SET command for the timezone. In reviewing the logs, I threw myself off because I kept seeing these ROLLBACK statements and assumed Django's transaction management was the source. Turns out it's not, and that's OK.\nConnections\nThe connection management is where things do get tricky. It turns out Django uses signals.request_finished.connect(close_connection) to close the database connection it normally uses. Since nothing normally happens in Django that doesn't involve a request, you take this behavior for granted.\nIn my case, though, there was no request because the job was scheduled. No request means no signal. No signal means the database connection was never closed.\nGoing back to transactions, it turns out that simply issuing a call to connection.close() in the absence of any changes to the transaction management issues the ROLLBACK statement in the PostgreSQL log that I'd been looking for.\nSolution\nThe solution is to allow the normal Django transaction management to proceed as normal and to simply close the connection one of three ways:\n\nWrite a decorator that closes the connection and wrap the necessary functions in it.\nHook into the existing request signals to have Django close the connection.\nClose the connection manually at the end of the function.\n\nAny of those three will (and do) work.\nThis has driven me crazy for weeks. I hope this helps someone else in the future!","Q_Score":59,"Tags":"python,database,django,multithreading,transactions","A_Id":1346401,"CreationDate":"2009-08-20T02:26:00.000","Title":"Threaded Django task doesn't automatically handle transactions or db connections?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"When using Python and doing a Select statement to MYSQL to select 09 from a column the zero gets dropped and only the 9 gets printed.\nIs there any way to pull all of the number i.e. including the leading zero?","AnswerCount":5,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1789,"Q_Id":1308038,"Users Score":4,"Answer":"There's almost certainly something in either your query, your table definition, or an ORM you're using that thinks the column is numeric and is converting the results to integers.  You'll have to define the column as a string (everywhere!) if you want to preserve leading zeroes.\nEdit: ZEROFILL on the server isn't going to cut it.  Python treats integer columns as Python integers, and those don't have leading zeroes, period.  You'll either have to change the column type to VARCHAR, use something like \"%02d\" % val in Python, or put a CAST(my_column AS VARCHAR) in the query.","Q_Score":1,"Tags":"python,mysql","A_Id":1308060,"CreationDate":"2009-08-20T18:36:00.000","Title":"Python - MYSQL - Select leading zeros","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'd like to use the Python version of App Engine but rather than write my code specifically for the Google Data Store, I'd like to create my models with a generic Python ORM that could be attached to Big Table, or, if I prefer, a regular database at some later time. Is there any Python ORM such as SQLAlchemy that would allow this?","AnswerCount":2,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":5333,"Q_Id":1308376,"Users Score":2,"Answer":"Nowadays they do since Google has launched Cloud SQL","Q_Score":11,"Tags":"python,google-app-engine,sqlalchemy,orm","A_Id":11325656,"CreationDate":"2009-08-20T19:39:00.000","Title":"Do any Python ORMs (SQLAlchemy?) work with Google App Engine?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I need to insert a python tuple (of floats) into a MySQL database. In principle I could pickle it and insert it as a string, but that would grant me the chance only to retrieve it through python. Alternative is to serialize the tuple to XML and store the XML string.\nWhat solutions do you think would be also possible, with an eye toward storing other stuff (e.g. a list, or an object). Recovering it from other languages is a plus.","AnswerCount":3,"Available Count":2,"Score":0.1973753202,"is_accepted":false,"ViewCount":2884,"Q_Id":1313000,"Users Score":3,"Answer":"Make another table and do one-to-many.  Don't try to cram a programming language feature into a database as-is if you can avoid it.\nIf you absolutely need to be able to store an object down the line, your options are a bit more limited.  YAML is probably the best balance of human-readable and program-readable, and it has some syntax for specifying classes you might be able to use.","Q_Score":0,"Tags":"python,mysql","A_Id":1313013,"CreationDate":"2009-08-21T16:39:00.000","Title":"Inserting python tuple in a MySQL database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I need to insert a python tuple (of floats) into a MySQL database. In principle I could pickle it and insert it as a string, but that would grant me the chance only to retrieve it through python. Alternative is to serialize the tuple to XML and store the XML string.\nWhat solutions do you think would be also possible, with an eye toward storing other stuff (e.g. a list, or an object). Recovering it from other languages is a plus.","AnswerCount":3,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":2884,"Q_Id":1313000,"Users Score":2,"Answer":"I'd look at serializing it to JSON, using the simplejson package, or the built-in json package in python 2.6.\nIt's simple to use in python, importable by practically every other language, and you don't have to make all of the \"what tag should I use? what attributes should this have?\" decisions that you might in XML.","Q_Score":0,"Tags":"python,mysql","A_Id":1313016,"CreationDate":"2009-08-21T16:39:00.000","Title":"Inserting python tuple in a MySQL database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"To deploy a site with Python\/Django\/MySQL I had to do these on the server (RedHat Linux):\n\nInstall MySQLPython\nInstall ModPython\nInstall Django (using python setup.py install)\nAdd some directives on httpd.conf file (or use .htaccess)\n\nBut, when I deployed another site with PHP (using CodeIgniter) I had to do nothing. I faced some problems while deploying a Django project on a shared server. Now, my questions are:\n\nCan the deployment process of Django project be made easier?\nAm I doing too much?\nCan some of the steps be omitted?\nWhat is the best way to deploy django site on a shared server?","AnswerCount":7,"Available Count":1,"Score":0.0285636566,"is_accepted":false,"ViewCount":1978,"Q_Id":1313989,"Users Score":1,"Answer":"You didn't have to do anything when deploying a PHP site because your hosting provider had already installed it. Web hosts which support Django typically install and configure it for you.","Q_Score":3,"Tags":"python,django","A_Id":1314005,"CreationDate":"2009-08-21T20:11:00.000","Title":"How can Django projects be deployed with minimal installation work?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Rather than use an ORM, I am considering the following approach in Python and MySQL with no ORM (SQLObject\/SQLAlchemy). I would like to get some feedback on whether this seems likely to have any negative long-term consequences since in the short-term view it seems fine from what I can tell.\nRather than translate a row from the database into an object:\n\neach table is represented by a class\na row is retrieved as a dict\nan object representing a cursor provides access to a table like so:\ncursor.mytable.get_by_ids(low, high)\nremoving means setting the time_of_removal to the current time\n\nSo essentially this does away with the need for an ORM since each table has a class to represent it and within that class, a separate dict represents each row.\nType mapping is trivial because each dict (row) being a first class object in python\/blub allows you to know the class of the object and, besides, the low-level database library in Python handles the conversion of types at the field level into their appropriate application-level types.\nIf you see any potential problems with going down this road, please let me know. Thanks.","AnswerCount":3,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":569,"Q_Id":1319585,"Users Score":8,"Answer":"That doesn't do away with the need for an ORM.  That is an ORM.  In which case, why reinvent the wheel?\nIs there a compelling reason you're trying to avoid using an established ORM?","Q_Score":3,"Tags":"python,sqlalchemy,sqlobject","A_Id":1319598,"CreationDate":"2009-08-23T21:15:00.000","Title":"Is this a good approach to avoid using SQLAlchemy\/SQLObject?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Rather than use an ORM, I am considering the following approach in Python and MySQL with no ORM (SQLObject\/SQLAlchemy). I would like to get some feedback on whether this seems likely to have any negative long-term consequences since in the short-term view it seems fine from what I can tell.\nRather than translate a row from the database into an object:\n\neach table is represented by a class\na row is retrieved as a dict\nan object representing a cursor provides access to a table like so:\ncursor.mytable.get_by_ids(low, high)\nremoving means setting the time_of_removal to the current time\n\nSo essentially this does away with the need for an ORM since each table has a class to represent it and within that class, a separate dict represents each row.\nType mapping is trivial because each dict (row) being a first class object in python\/blub allows you to know the class of the object and, besides, the low-level database library in Python handles the conversion of types at the field level into their appropriate application-level types.\nIf you see any potential problems with going down this road, please let me know. Thanks.","AnswerCount":3,"Available Count":2,"Score":0.1325487884,"is_accepted":false,"ViewCount":569,"Q_Id":1319585,"Users Score":2,"Answer":"You will still be using SQLAlchemy. ResultProxy is actually a dictionary once you go for .fetchmany() or similar.\nUse SQLAlchemy as a tool that makes managing connections easier, as well as executing statements. Documentation is pretty much separated in sections, so you will be reading just the part that you need.","Q_Score":3,"Tags":"python,sqlalchemy,sqlobject","A_Id":1319662,"CreationDate":"2009-08-23T21:15:00.000","Title":"Is this a good approach to avoid using SQLAlchemy\/SQLObject?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am writing a python script that will be doing some processing on text files.  As part of that process, i need to import each line of the tab-separated file into a local MS SQL Server (2008) table.  I am using pyodbc and I know how to do this.  However, I have a question about the best way to execute it.\nI will be looping through the file, creating a cursor.execute(myInsertSQL) for each line of the file.  Does anyone see any problems waiting to commit the statements until all records have been looped (i.e. doing the commit() after the loop and not inside the loop after each individual execute)?  The reason I ask is that some files will have upwards of 5000 lines.  I didn't know if trying to \"save them up\" and committing all 5000 at once would cause problems.\nI am fairly new to python, so I don't know all of these issues yet.  \nThanks.","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":3467,"Q_Id":1325481,"Users Score":0,"Answer":"If I understand what you are doing, Python is not going to be a problem.  Executing a statement inside a transaction does not create cumulative state in Python.  It will do so only at the database server itself.\nWhen you commit you will need to make sure the commit occurred, since having a large batch commit may conflict with intervening changes in the database.  If the commit fails, you will have to re-run the batch again.\nThat's the only problem that I am aware of with large batches and Python\/ODBC (and it's not even really a Python problem, since you would have that problem regardless.)\nNow, if you were creating all the SQL in memory, and then looping through the memory-representation, that might make more sense.  Still, 5000 lines of text on a modern machine is really not that big of a deal.  If you start needing to process two orders of magnitude more, you might need to rethink your process.","Q_Score":1,"Tags":"python,database,odbc,commit,bulkinsert","A_Id":1325524,"CreationDate":"2009-08-25T00:30:00.000","Title":"Importing a text file into SQL Server in Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am interested in monitoring some objects. I expect to get about 10000 data points every 15 minutes. (Maybe not at first, but this is the 'general ballpark'). I would also like to be able to get daily, weekly, monthly and yearly statistics. It is not critical to keep the data in the highest resolution (15 minutes) for more than two months.\nI am considering various ways to store this data, and have been looking at a classic relational database, or at a schemaless database (such as SimpleDB). \nMy question is, what is the best way to go along doing this? I would very much prefer an open-source (and free) solution to a proprietary costly one. \nSmall note: I am writing this application in Python.","AnswerCount":5,"Available Count":1,"Score":0.0399786803,"is_accepted":false,"ViewCount":13739,"Q_Id":1334813,"Users Score":1,"Answer":"plain text files? It's not clear what your 10k data points per 15 minutes translates to in terms of bytes, but in any way text files are easier to store\/archive\/transfer\/manipulate and you can inspect the directly, just by looking at. fairly easy to work with Python, too.","Q_Score":17,"Tags":"python,database,statistics,time-series,schemaless","A_Id":1335132,"CreationDate":"2009-08-26T13:47:00.000","Title":"What is the best open source solution for storing time series data?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm using Django 1.1 with Mysql 5.* and MyISAM tables.\nSome of my queries can take a TON of time for outliers in my data set. These lock the tables and shut the site down. Other times it seems some users cancel the request before it is done and some queries will be stuck in the \"Preparing\" phase locking all other queries out.\nI'm going to try to track down all the corner cases, but its nice to have a safety net so the site doesn't come down.\nHow do I avoid this? Can I set maximum query times?","AnswerCount":6,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":4741,"Q_Id":1353206,"Users Score":0,"Answer":"You shouldn't write queries like that, at least not to run against your live database.  Mysql has a \"slow queries\" pararameter which you can use to identify the queries that are killing you.   Most of the time, these slow queries are either buggy or can be speeded up by defining a new index or two.","Q_Score":7,"Tags":"python,mysql,django,timeout","A_Id":1500947,"CreationDate":"2009-08-30T06:10:00.000","Title":"Django: How can you stop long queries from killing your database?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm using Django 1.1 with Mysql 5.* and MyISAM tables.\nSome of my queries can take a TON of time for outliers in my data set. These lock the tables and shut the site down. Other times it seems some users cancel the request before it is done and some queries will be stuck in the \"Preparing\" phase locking all other queries out.\nI'm going to try to track down all the corner cases, but its nice to have a safety net so the site doesn't come down.\nHow do I avoid this? Can I set maximum query times?","AnswerCount":6,"Available Count":3,"Score":1.2,"is_accepted":true,"ViewCount":4741,"Q_Id":1353206,"Users Score":1,"Answer":"Unfortunately MySQL doesn't allow you an easy way to avoid this.  A common method is basically to write a script that checks all running processes every X seconds (based on what you think is \"long\") and kill ones it sees are running too long.  You can at least get some basic diagnostics, however, by setting log_slow_queries in MySQL which will write all queries that take longer than 10 seconds into a log.  If that's too long for what you regard as \"slow\" for your purposes, you can set long_query_time to a value other than 10 to change the threshold.","Q_Score":7,"Tags":"python,mysql,django,timeout","A_Id":1353862,"CreationDate":"2009-08-30T06:10:00.000","Title":"Django: How can you stop long queries from killing your database?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm using Django 1.1 with Mysql 5.* and MyISAM tables.\nSome of my queries can take a TON of time for outliers in my data set. These lock the tables and shut the site down. Other times it seems some users cancel the request before it is done and some queries will be stuck in the \"Preparing\" phase locking all other queries out.\nI'm going to try to track down all the corner cases, but its nice to have a safety net so the site doesn't come down.\nHow do I avoid this? Can I set maximum query times?","AnswerCount":6,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":4741,"Q_Id":1353206,"Users Score":0,"Answer":"Do you know what the queries are? Maybe you could optimise the SQL or put some indexes on your tables?","Q_Score":7,"Tags":"python,mysql,django,timeout","A_Id":1353366,"CreationDate":"2009-08-30T06:10:00.000","Title":"Django: How can you stop long queries from killing your database?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a problem reading a txt file to insert in the mysql db table, te sniped of this code:\nfile contains the in first line: \"aclaraci\u00f3n\"\n\narchivo = open('file.txt',\"r\") \n  for line in archivo.readlines():\n  ....body = body + line\n  model = MyModel(body=body)\n  model.save()\n\ni get a DjangoUnicodeDecodeError:\n'utf8' codec can't decode bytes in position 8: invalid data. You passed in 'aclaraci\\xf3n' (type 'str')\nUnicode error hint\nThe string that could not be encoded\/decoded was: araci\ufffdn.\nI tried to body.decode('utf-8'), body.decode('latin-1'), body.decode('iso-8859-1') without solution.\nCan you help me please? Any hint is apreciated :)","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":3312,"Q_Id":1355285,"Users Score":5,"Answer":"Judging from the \\xf3 code for '\u00f3', it does look like the data is encoded in ISO-8859-1 (or some close relative).  So body.decode('iso-8859-1') should be a valid Unicode string (you don't specify what \"without solution\" means -- what error message do you get, and where?); if what you need is a utf-8 encoded bytestring instead, body.decode('iso-8859-1').encode('utf-8') should give you one!","Q_Score":1,"Tags":"python,django,utf-8,character-encoding","A_Id":1355303,"CreationDate":"2009-08-31T00:11:00.000","Title":"Latin letters with acute : DjangoUnicodeDecodeError","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm building a fairly large enterprise application made in python that on its first version will require network connection.\nI've been thinking in keeping some user settings stored on the database, instead of a file in the users home folder.\nSome of the advantages I've thought of are:\n\nthe user can change computers keeping all its settings\nsettings can be backed up along with the rest of the systems data (not a big concern)\n\nWhat would be some of the caveats of this approach?","AnswerCount":4,"Available Count":4,"Score":0.2449186624,"is_accepted":false,"ViewCount":650,"Q_Id":1365164,"Users Score":5,"Answer":"One caveat might depend on where the user is using the application from. For example, if they use two computers with different screen resolutions, and 'selected zoom\/text size' is one of the things you associate with the user, it might not always be suitable. It depends what kind of settings you intend to allow the user to customize. My workplace still has some users trapped on tiny LCD screens with a max res of 800x600, and we have to account for those when developing.","Q_Score":2,"Tags":"python,database,settings","A_Id":1365175,"CreationDate":"2009-09-01T23:32:00.000","Title":"Is storing user configuration settings on database OK?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm building a fairly large enterprise application made in python that on its first version will require network connection.\nI've been thinking in keeping some user settings stored on the database, instead of a file in the users home folder.\nSome of the advantages I've thought of are:\n\nthe user can change computers keeping all its settings\nsettings can be backed up along with the rest of the systems data (not a big concern)\n\nWhat would be some of the caveats of this approach?","AnswerCount":4,"Available Count":4,"Score":0.1488850336,"is_accepted":false,"ViewCount":650,"Q_Id":1365164,"Users Score":3,"Answer":"Do you need the database to run any part of the application? If that's the case there are no reasons not to store the config inside the DB. You already mentioned the benefits and there are no downsides.","Q_Score":2,"Tags":"python,database,settings","A_Id":1365176,"CreationDate":"2009-09-01T23:32:00.000","Title":"Is storing user configuration settings on database OK?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm building a fairly large enterprise application made in python that on its first version will require network connection.\nI've been thinking in keeping some user settings stored on the database, instead of a file in the users home folder.\nSome of the advantages I've thought of are:\n\nthe user can change computers keeping all its settings\nsettings can be backed up along with the rest of the systems data (not a big concern)\n\nWhat would be some of the caveats of this approach?","AnswerCount":4,"Available Count":4,"Score":0.1488850336,"is_accepted":false,"ViewCount":650,"Q_Id":1365164,"Users Score":3,"Answer":"It's perfectly reasonable to keep user settings in the database, as long as the settings pertain to the application independent of user location. One possible advantage of a file in the user's home folder is that users can send settings to one another. You may of course regard this as an advantage or a disadvantage :-)","Q_Score":2,"Tags":"python,database,settings","A_Id":1365183,"CreationDate":"2009-09-01T23:32:00.000","Title":"Is storing user configuration settings on database OK?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm building a fairly large enterprise application made in python that on its first version will require network connection.\nI've been thinking in keeping some user settings stored on the database, instead of a file in the users home folder.\nSome of the advantages I've thought of are:\n\nthe user can change computers keeping all its settings\nsettings can be backed up along with the rest of the systems data (not a big concern)\n\nWhat would be some of the caveats of this approach?","AnswerCount":4,"Available Count":4,"Score":1.2,"is_accepted":true,"ViewCount":650,"Q_Id":1365164,"Users Score":8,"Answer":"This is pretty standard. Go for it.\nThe caveat is that when you take the database down for maintenance, no one can use the app because their profile is inaccessible. You can either solve that by making a 100%-on db solution, or, more easily, through some form of caching of profiles locally (an \"offline\" mode of operations). That would allow your app to function whether the user or the db are off the network.","Q_Score":2,"Tags":"python,database,settings","A_Id":1365178,"CreationDate":"2009-09-01T23:32:00.000","Title":"Is storing user configuration settings on database OK?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am learning Python and creating a database connection.\nWhile trying to add to the DB, I am thinking of creating tuples out of information and then add them to the DB. \nWhat I am Doing:\nI am taking information from the user and store it in variables. \nCan I add these variables into a tuple?  Can you please help me with the syntax?\nAlso if there is an efficient way of doing this, please share...\nEDIT\nLet me edit this question a bit...I only need the tuple to enter info into the DB.  Once the information is added to the DB, should I delete the tuple?  I mean I don't need the tuple anymore.","AnswerCount":8,"Available Count":1,"Score":1.0,"is_accepted":false,"ViewCount":728594,"Q_Id":1380860,"Users Score":9,"Answer":"\" once the info is added to the DB, should I delete the tuple? i mean i dont need the tuple anymore.\"\nNo.\nGenerally, there's no reason to delete anything.  There are some special cases for deleting, but they're very, very rare.\nSimply define a narrow scope (i.e., a function definition or a method function in a class) and the objects will be garbage collected at the end of the scope.\nDon't worry about deleting anything.\n[Note.  I worked with a guy who -- in addition to trying to delete objects -- was always writing \"reset\" methods to clear them out.  Like he was going to save them and reuse them.  Also a silly conceit.  Just ignore the objects you're no longer using.  If you define your functions in small-enough blocks of code, you have nothing more to think about.]","Q_Score":353,"Tags":"python,tuples","A_Id":1381304,"CreationDate":"2009-09-04T18:36:00.000","Title":"Add Variables to Tuple","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"SQLite docs specifies that the preferred format for storing datetime values in the DB is to use Julian Day (using built-in functions).\nHowever, all frameworks I saw in python (pysqlite, SQLAlchemy) store the datetime.datetime values as ISO formatted strings. Why are they doing so?\nI'm usually trying to adapt the frameworks to storing datetime as julianday, and it's quite painful. I started to doubt that is worth the efforts.\nPlease share your experience in this field with me. Does sticking with julianday make sense?","AnswerCount":4,"Available Count":2,"Score":1.0,"is_accepted":false,"ViewCount":1707,"Q_Id":1386093,"Users Score":6,"Answer":"Julian Day is handy for all sorts of date calculations, but it can's store the time part decently (with precise hours, minutes, and seconds). In the past I've used both Julian Day fields (for dates), and seconds-from-the-Epoch (for datetime instances), but only when I had specific needs for computation (of dates and respectively of times). The simplicity of ISO formatted dates and datetimes, I think, should make them the preferred choice, say about 97% of the time.","Q_Score":8,"Tags":"python,datetime,sqlite,sqlalchemy,pysqlite","A_Id":1386154,"CreationDate":"2009-09-06T16:43:00.000","Title":"Shall I bother with storing DateTime data as julianday in SQLite?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"SQLite docs specifies that the preferred format for storing datetime values in the DB is to use Julian Day (using built-in functions).\nHowever, all frameworks I saw in python (pysqlite, SQLAlchemy) store the datetime.datetime values as ISO formatted strings. Why are they doing so?\nI'm usually trying to adapt the frameworks to storing datetime as julianday, and it's quite painful. I started to doubt that is worth the efforts.\nPlease share your experience in this field with me. Does sticking with julianday make sense?","AnswerCount":4,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":1707,"Q_Id":1386093,"Users Score":0,"Answer":"Because 2010-06-22 00:45:56 is far easier for a human to read than 2455369.5318981484.  Text dates are great for doing ad-hoc queries in SQLiteSpy or SQLite Manager.\nThe main drawback, of course, is that text dates require 19 bytes instead of 8.","Q_Score":8,"Tags":"python,datetime,sqlite,sqlalchemy,pysqlite","A_Id":3089486,"CreationDate":"2009-09-06T16:43:00.000","Title":"Shall I bother with storing DateTime data as julianday in SQLite?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have an object that is basically a Python implementation of an Oracle sequence.  For a variety of reasons, we have to get the nextval of an Oracle sequence, count up manually when determining primary keys, then update the sequence once the records have been inserted.\nSo here's the steps my object does:\n\nConstruct an object, with a key_generator attribute initially set to None.\nGet the first value from the database, passing it to an itertools.count.\nReturn keys from that generator using a property next_key.\n\nI'm a little bit unsure about where to do step 2.  I can think of three possibilities:\n\nSkip step 1 and do step 2 in the constructor.  I find this evil because I tend to dislike doing this kind of initialization in a constructor.\nMake next_key get the starting key from the database the first time it is called.  I find this evil because properties are typically assumed to be trivial.\nMake next_key into a get_next_key method.  I dislike this because properties just seem more natural here.\n\nWhich is the lesser of 3 evils?  I'm leaning towards #2, because only the first call to this property will result in a database query.","AnswerCount":3,"Available Count":2,"Score":0.1325487884,"is_accepted":false,"ViewCount":190,"Q_Id":1386210,"Users Score":2,"Answer":"I agree that attribute access and everything that looks like it (i.e. properties in the Python context) should be fairly trivial. If a property is going to perform a potentially costly operation, use a method to make this explicit. I recommend a name like \"fetch_XYZ\" or \"retrieve_XYZ\", since \"get_XYZ\" is used in some languages (e.g. Java) as a convention for simple attribute access, is quite generic, and does not sound \"costly\" either.\nA good guideline is: If your property could throw an exception that is not due to a programming error, it should be a method. For example, throwing a (hypothetical) DatabaseConnectionError from a property is bad, while throwing an ObjectStateError would be okay.\nAlso, when I understood you correctly, you want to return the next key, whenever the next_key property is accessed. I recommend strongly against having side-effects (apart from caching, cheap lazy initialization, etc.) in your properties. Properties (and attributes for that matter) should be idempotent.","Q_Score":2,"Tags":"python,properties,initialization","A_Id":1386258,"CreationDate":"2009-09-06T17:35:00.000","Title":"Should properties do nontrivial initialization?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have an object that is basically a Python implementation of an Oracle sequence.  For a variety of reasons, we have to get the nextval of an Oracle sequence, count up manually when determining primary keys, then update the sequence once the records have been inserted.\nSo here's the steps my object does:\n\nConstruct an object, with a key_generator attribute initially set to None.\nGet the first value from the database, passing it to an itertools.count.\nReturn keys from that generator using a property next_key.\n\nI'm a little bit unsure about where to do step 2.  I can think of three possibilities:\n\nSkip step 1 and do step 2 in the constructor.  I find this evil because I tend to dislike doing this kind of initialization in a constructor.\nMake next_key get the starting key from the database the first time it is called.  I find this evil because properties are typically assumed to be trivial.\nMake next_key into a get_next_key method.  I dislike this because properties just seem more natural here.\n\nWhich is the lesser of 3 evils?  I'm leaning towards #2, because only the first call to this property will result in a database query.","AnswerCount":3,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":190,"Q_Id":1386210,"Users Score":0,"Answer":"I've decided that the key smell in the solution I'm proposing is that the property I was creating contained the word \"next\" in it.  Thus, instead of making a next_key property, I've decided to turn my DatabaseIntrospector class into a KeyCounter class and implemented the iterator protocol (ie making a plain old next method that returns the next key).","Q_Score":2,"Tags":"python,properties,initialization","A_Id":1389673,"CreationDate":"2009-09-06T17:35:00.000","Title":"Should properties do nontrivial initialization?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"What is the best way to use an embedded database, say sqlite in Python:\n\nShould be small footprint. I'm only needing few thousands records per table. And just a handful of tables per database.\nIf it's one provided by Python default installation, then great.  Must be open-source, available on Windows and Linus.  \nBetter if SQL is not written directly, but no ORM is fully needed.  Something that will shield me from the actual database, but not that huge of a library.  Something similar to ADO will be great.\nMostly will be used through code, but if there is a GUI front end, then that is great\nNeed just a few pages to get started with.  I don't want to go through pages reading what a table is and how a Select statement works.  I know all of that.\nSupport for Python 3 is preferred, but 2.x is okay too.\n\nThe usage is not a web app.  It's a small database to hold at most 5 tables.  The data in each table is just a few string columns.  Think something just larger than a pickled dictionary\nUpdate: Many thanks for the great suggestions.\nThe use-case I'm talking about is fairly simple.  One you'd probably do in a day or two.\nIt's a 100ish line Python script that gathers data about a relatively large number of files (say 10k), and creates metadata files about them, and then one large metadata file about the whole files tree.  I just need to avoid re-processing the files already processed, and create the metadata for the updated files, and update the main metadata file.  In a way, cache the processed data, and only update it on file updates.\nIf the cache is corrupt \/ unavailable, then simply process the whole tree.  It might take 20 minutes, but that's okay.\nNote that all processing is done in-memory.\nI would like to avoid any external dependencies, so that the script can easily be put on any system with just a Python installation on it.  Being Windows, it is sometimes hard to get all the components installed.\nSo, In my opinion, even a database might be an overkill.  \nYou probably wouldn't fire up an Office Word\/Writer to write a small post it type note, similarly I am reluctant on using something like Django for this use-case.\nWhere to start?","AnswerCount":9,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":5927,"Q_Id":1407248,"Users Score":0,"Answer":"Django is perfect for this but the poster is not clear if he needs to actually make a compiled EXE or a web app. Django is only for web apps.\nI'm not sure where you really get \"heavy\" from. Django is grossly smaller in terms of lines of code than any other major web app framework.","Q_Score":7,"Tags":"python,database,sqlite,ado","A_Id":1407345,"CreationDate":"2009-09-10T19:31:00.000","Title":"python database \/ sql programming - where to start","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have started learning Python by writing a small application using Python 3.1 and py-PostgreSQL. Now I want to turn it into a web application.\nBut it seems that most frameworks such as web-py, Django, zope are still based on Python 2.x. Unfortunately, py-PostgreSQL is incompatible with Python 2.x.\nDo I have to rewrite all my classes and replace py-PostgreSQL with something supported by web-py etc., or is there a framework compatible with Python 3.1?\nOr maybe py-PostgreSQL is compatible with 2.x but I did not figure it out?","AnswerCount":4,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1695,"Q_Id":1423000,"Users Score":0,"Answer":"Even though it's not officially released yet, I am currently 'playing around' with CherryPy 3.2.0rc1 with Python 3.1.1 and have had no problems yet.  Haven't used it with py-postgresql, but I don't see why it shouldn't work.\nHope this helps,\nAlan","Q_Score":1,"Tags":"python,web-applications,python-3.x,wsgi","A_Id":1934744,"CreationDate":"2009-09-14T17:56:00.000","Title":"web framework compatible with python 3.1 and py-postgresql","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am just starting out with the MySQLdb module for python, and upon running some SELECT and UPDATE queries, the following gets output:\n\nException\n  _mysql_exceptions.OperationalError: (2013, 'Lost connection to MySQL\n  server during query') in bound method Cursor.del of\n  MySQLdb.cursors.Cursor object at 0x8c0188c ignored\n\nThe exception is apparently getting caught (and \"ignored\") by MySQLdb itself, so I guess this is not a major issue. Also, the SELECTs generate results and the table gets modified by UPDATE.\nBut, since I am just getting my feet wet with this, I want to ask: does this message suggest I am doing something wrong? Or have you seen these warnings before in harmless situations?\nThanks for any insight,\nlara","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":2148,"Q_Id":1439616,"Users Score":0,"Answer":"Ha! Just realized I was trying to use the cursor after having closed the connection! In any case, it was nice writing! : )\nl","Q_Score":0,"Tags":"python,mysql","A_Id":1439734,"CreationDate":"2009-09-17T15:33:00.000","Title":"have you seen? _mysql_exceptions.OperationalError \"Lost connection to MySQL server during query\" being ignored","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have configured pgpool-II for postgres connection pooling and I want to disable psycopg2 connection pooling. How do I do this?\nThanks!","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1426,"Q_Id":1440245,"Users Score":6,"Answer":"psycopg2 doesn't pool connections unless you explicitely use the psycopg.pool module.","Q_Score":0,"Tags":"python,psycopg2","A_Id":1492172,"CreationDate":"2009-09-17T17:34:00.000","Title":"How do I disable psycopg2 connection pooling?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am trying to install pysqlite and have troubles with that. I found out that the most probable reason of that is missing sqlite headers and I have to install them.\nHowever, I have no ideas what these headers are (where I can find them, what they are doing and how to install them).\nCan anybody, pleas, help me with that?","AnswerCount":3,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":17278,"Q_Id":1462565,"Users Score":0,"Answer":"pysqlite needs to compiled\/build before you can use it.  This requires C language header files (*.H) which come with the source code of sqllite itself.\ni.e. sqllite and pysqlite are two different things.  Did you install sqlite prior to trying and build pysqllte ?  (or maybe you did, but did you do so just with the binaries;  you need the source package (or at least its headers) for pysqlite purposes.","Q_Score":12,"Tags":"python,header,pysqlite","A_Id":1462623,"CreationDate":"2009-09-22T20:57:00.000","Title":"What are sqlite development headers and how to install them?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am trying to install pysqlite and have troubles with that. I found out that the most probable reason of that is missing sqlite headers and I have to install them.\nHowever, I have no ideas what these headers are (where I can find them, what they are doing and how to install them).\nCan anybody, pleas, help me with that?","AnswerCount":3,"Available Count":2,"Score":1.0,"is_accepted":false,"ViewCount":17278,"Q_Id":1462565,"Users Score":7,"Answer":"For me this worked (Redhat\/CentOS):\n$ sudo yum install sqlite-devel","Q_Score":12,"Tags":"python,header,pysqlite","A_Id":5671345,"CreationDate":"2009-09-22T20:57:00.000","Title":"What are sqlite development headers and how to install them?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am trying to get started on working with Python on Django I am by profession a PHP developer and have been told to set up django and python on my current apache and mysql setup however I am having trouble getting the Mysqldb module for python to work, I must of followed about 6 different set of instructions, I am running snow leopard and have mysql installed natively it is not part of MAMP or similar. Please can some tell me where I need to start and what steps I need to follew I would be most grateful.\nThanks","AnswerCount":8,"Available Count":1,"Score":1.0,"is_accepted":false,"ViewCount":7786,"Q_Id":1465846,"Users Score":7,"Answer":"On MAC OS X 10.6, Install the package as usual. The dynamic import error occurs because of wrong DYLD path. Export the path and open up a python terminal.\n$ sudo python setup.py clean\n$ sudo python setup.py build\n$ sudo python setup.py install\n$ export DYLD_LIBRARY_PATH=\/usr\/local\/mysql\/lib:$DYLD_LIBRARY_PATH\n$python\n\n\nimport MySQLdb\n\n\nNow import MySQLdb should work fine.\nYou may also want to manually remove the build folder, before build and install. The clean command does not do a proper task of cleaning up the build files.","Q_Score":7,"Tags":"python,mysql,django,osx-snow-leopard","A_Id":6537345,"CreationDate":"2009-09-23T13:01:00.000","Title":"Install mysqldb on snow leopard","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Can Python be used to query a SAP database?","AnswerCount":7,"Available Count":2,"Score":0.1137907297,"is_accepted":false,"ViewCount":48208,"Q_Id":1466917,"Users Score":4,"Answer":"Sap is NOT a database server.\nBut with the Python SAP RFC module you can query most table quite easily. It is using some sap unsupported function ( that all the world is using). And this function has some limitation on field size and datatypes.","Q_Score":36,"Tags":"python,abap,sap-basis,pyrfc","A_Id":1467921,"CreationDate":"2009-09-23T15:55:00.000","Title":"Query SAP database from Python?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Can Python be used to query a SAP database?","AnswerCount":7,"Available Count":2,"Score":0.0285636566,"is_accepted":false,"ViewCount":48208,"Q_Id":1466917,"Users Score":1,"Answer":"Python is one of the most used object-oriented programming languages which is very easy to code and understand.\nIn order to use Python with SAP, we need to install Python SAP RFC module which is known as PyRFC. One of its available methods is RFC_READ_TABLE which can be called to read data from a table in SAP database.\nAlso, the PyRFC package provides various bindings which can be utilized to make calls either way. We can use to make calls either from ABAP modules to Python modules or the other way round. One can define equivalent SAP data types which are used in data exchange.\nAlso, we can create Web Service in Python which can be used for inter-communication. SAP NetWeaver is fully compatible with web services either state full or stateless.","Q_Score":36,"Tags":"python,abap,sap-basis,pyrfc","A_Id":59210473,"CreationDate":"2009-09-23T15:55:00.000","Title":"Query SAP database from Python?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Is there a python equivalent of phpMyAdmin?\nHere's why I'm looking for a python version of phpmyadmin: While I agree that phpmyadmin really rocks, I don't want to run php on my server. I'd like to move from apache2-prefork to apache2-mpm-worker. Worker blows the doors off of prefork for performance, but php5 doesn't work with worker. (Technically it does, but it's far more complicated.) The extra memory and performance penalty for having php on this server is large to me.","AnswerCount":4,"Available Count":1,"Score":1.0,"is_accepted":false,"ViewCount":23600,"Q_Id":1480453,"Users Score":12,"Answer":"You can use phpMyAdmin for python project, because phpMyAdmin is meant for MySQL databases. If you are using MySQL, then regardless of whether you are using PHP or python, you can use phpMyAdmin.","Q_Score":33,"Tags":"python,phpmyadmin","A_Id":1480549,"CreationDate":"2009-09-26T04:51:00.000","Title":"phpMyAdmin equivalent in python?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm using SQLAlchemy and I can create tables that I have defined in \/model\/__init__.py but I have defined my classes, tables and their mappings in other files found in the \/model directory. \nFor example I have a profile class and a profile table which are defined and mapped in \/model\/profile.py\nTo create the tables I run: \npaster setup-app development.ini\nBut my problem is that the tables that I have defined in \/model\/__init__.py are created properly but the table definitions found in \/model\/profile.py are not created. How can I execute the table definitions found in the \/model\/profile.py so that all my tables can be created?\nThanks for the help!","AnswerCount":3,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":1155,"Q_Id":1482627,"Users Score":0,"Answer":"Just import your other table's modules in your init.py, and use metadata object from models.meta in other files. Pylons default setup_app function creates all tables found in metadata object from model.meta after importing it.","Q_Score":3,"Tags":"python,sqlalchemy,pylons","A_Id":1483061,"CreationDate":"2009-09-27T02:19:00.000","Title":"Creating tables with pylons and SQLAlchemy","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm using SQLAlchemy and I can create tables that I have defined in \/model\/__init__.py but I have defined my classes, tables and their mappings in other files found in the \/model directory. \nFor example I have a profile class and a profile table which are defined and mapped in \/model\/profile.py\nTo create the tables I run: \npaster setup-app development.ini\nBut my problem is that the tables that I have defined in \/model\/__init__.py are created properly but the table definitions found in \/model\/profile.py are not created. How can I execute the table definitions found in the \/model\/profile.py so that all my tables can be created?\nThanks for the help!","AnswerCount":3,"Available Count":3,"Score":0.3215127375,"is_accepted":false,"ViewCount":1155,"Q_Id":1482627,"Users Score":5,"Answer":"I ran into the same problem with my first real Pylons project.  The solution that worked for me was this:\n\nDefine tables and classes in your profile.py file\nIn your __init__.py add from profile import * after your def init_model\nI then added all of my mapper definitions afterwards.  Keeping them all in the init file solved some problems I was having relating between tables defined in different files.\n\nAlso, I've since created projects using the declarative method and didn't need to define the mapping in the init file.","Q_Score":3,"Tags":"python,sqlalchemy,pylons","A_Id":1528312,"CreationDate":"2009-09-27T02:19:00.000","Title":"Creating tables with pylons and SQLAlchemy","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm using SQLAlchemy and I can create tables that I have defined in \/model\/__init__.py but I have defined my classes, tables and their mappings in other files found in the \/model directory. \nFor example I have a profile class and a profile table which are defined and mapped in \/model\/profile.py\nTo create the tables I run: \npaster setup-app development.ini\nBut my problem is that the tables that I have defined in \/model\/__init__.py are created properly but the table definitions found in \/model\/profile.py are not created. How can I execute the table definitions found in the \/model\/profile.py so that all my tables can be created?\nThanks for the help!","AnswerCount":3,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":1155,"Q_Id":1482627,"Users Score":0,"Answer":"If you are using declarative style, be sure to use Base.meta for tables generation.","Q_Score":3,"Tags":"python,sqlalchemy,pylons","A_Id":1485719,"CreationDate":"2009-09-27T02:19:00.000","Title":"Creating tables with pylons and SQLAlchemy","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I been working on finding out how to install MySQLdb module for Python on Mac. And all pathes finally come cross to have MySQL installed since there is a mysql_config needed for the module. But I don't understand why it has to be needed? \nMySQLdb suppose to be a client module for the client who wants to connect to the server. But now I have to first install a server on the client in order to connect to another server?","AnswerCount":5,"Available Count":3,"Score":0.0399786803,"is_accepted":false,"ViewCount":432,"Q_Id":1483024,"Users Score":1,"Answer":"What it needs is the client library and headers that come with the server, since it just a Python wrapper (which sits in _mysql.c; and DB-API interface to that wrapper in MySQLdb package) over original C MySQL API.","Q_Score":1,"Tags":"python,mysql","A_Id":1483154,"CreationDate":"2009-09-27T07:31:00.000","Title":"Why MySQLdb for Mac has to have MySQL installed to install?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I been working on finding out how to install MySQLdb module for Python on Mac. And all pathes finally come cross to have MySQL installed since there is a mysql_config needed for the module. But I don't understand why it has to be needed? \nMySQLdb suppose to be a client module for the client who wants to connect to the server. But now I have to first install a server on the client in order to connect to another server?","AnswerCount":5,"Available Count":3,"Score":0.0399786803,"is_accepted":false,"ViewCount":432,"Q_Id":1483024,"Users Score":1,"Answer":"I'm not sure about the specifics of MySQLdb, but most likely it needs header information to compile\/install.  It uses the location of mysql_config to know where the appropriate headers would be.  The MySQL Gem for Ruby on Rails requires the same thing, even though it simply connects to the MySQL server.","Q_Score":1,"Tags":"python,mysql","A_Id":1483030,"CreationDate":"2009-09-27T07:31:00.000","Title":"Why MySQLdb for Mac has to have MySQL installed to install?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I been working on finding out how to install MySQLdb module for Python on Mac. And all pathes finally come cross to have MySQL installed since there is a mysql_config needed for the module. But I don't understand why it has to be needed? \nMySQLdb suppose to be a client module for the client who wants to connect to the server. But now I have to first install a server on the client in order to connect to another server?","AnswerCount":5,"Available Count":3,"Score":0.0399786803,"is_accepted":false,"ViewCount":432,"Q_Id":1483024,"Users Score":1,"Answer":"Just to clarify what the other answerers have said: you don't need to install a MySQL server, but you do need to install the MySQL client libraries. However, for whatever reasons, MySQL don't make a separate download available for just the client libraries, as they do for Linux.","Q_Score":1,"Tags":"python,mysql","A_Id":1483305,"CreationDate":"2009-09-27T07:31:00.000","Title":"Why MySQLdb for Mac has to have MySQL installed to install?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I just upgraded the default Python 2.5 on Leopard to 2.6 via the installer on www.python.org. Upon doing so, the MySQLdb I had installed was no longer found. So I tried reinstalling it via port install py-mysql, and it succeeded, but MySQLdb was still not importable. So then I tried to python install python26 with python_select python26 and it succeeded, but it doesn't appear that it is getting precedence over the python.org install:\n$ which python\n\/Library\/Frameworks\/Python.framework\/Versions\/2.6\/bin\/python\nWhen I would expect it to be something like \/opt\/local\/bin\/python\nMy path environment is: \/Library\/Frameworks\/Python.framework\/Versions\/2.6\/bin:\/usr\/local\/mysql\/bin\/:\/opt\/local\/bin:\/opt\/local\/sbin:\/usr\/bin:\/bin:\/usr\/sbin:\/sbin:\/usr\/local\/bin:\/usr\/X11\/bin:\/usr\/local\/mysql\/bin:\/Users\/bsr\/bin\nAnyway, when I try port install py-mysql but how does it know where to install the Python MySQL library?","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":1051,"Q_Id":1499572,"Users Score":1,"Answer":"You also need python_select (or is it select_python?) to change the default python used.","Q_Score":0,"Tags":"python,mysql,macos","A_Id":2302542,"CreationDate":"2009-09-30T17:32:00.000","Title":"With multiple Python installs, how does MacPorts know which one to install MySQLdb for?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":0},{"Question":"A quick SQLAlchemy question...  \nI have a class \"Document\" with attributes \"Number\" and \"Date\". I need to ensure that there's no duplicated number for the same year, is\nthere a way to have a UniqueConstraint on \"Number + year(Date)\"? Should I use a unique Index  instead? How would I declare the functional part?\n(SQLAlchemy 0.5.5, PostgreSQL 8.3.4)\nThanks in advance!","AnswerCount":2,"Available Count":1,"Score":-0.0996679946,"is_accepted":false,"ViewCount":890,"Q_Id":1510018,"Users Score":-1,"Answer":"I'm pretty sure that unique constraints can only be applied on columns that already have data in them, and not on runtime-calculated expressions. Hence, you would need to create an extra column which contains the year part of your date, over which you could create a unique constraint together with number. To best use this approach, maybe you should store your date split up in three separate columns containing the day, month and year part. This could be done using default constraints in the table definition.","Q_Score":3,"Tags":"python,sqlalchemy,constraints","A_Id":1510137,"CreationDate":"2009-10-02T14:52:00.000","Title":"Compound UniqueConstraint with a function","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"One of the feature I like in RoR is the db management, it can hide all the sql statement, also, it is very easy to change different db in RoR, is there any similar framework in Python 3000?","AnswerCount":5,"Available Count":3,"Score":0.0399786803,"is_accepted":false,"ViewCount":614,"Q_Id":1510084,"Users Score":1,"Answer":"Python 3 isn't ready for web applications right now. The WSGI 1.0 specification isn't suitable for Py3k and the related standard libraries are 2to3 hacks that don't work consistently faced with bytes vs. unicode. It's a real mess.\nWEB-SIG are bashing out proposals for a WSGI revision; hopefully it can move forward soon, because although Python 3 isn't mainstream yet it's certainly heading that way, and the brokenness of webdev is rather embarrassing.","Q_Score":1,"Tags":"python,ruby-on-rails,frameworks,python-3.x","A_Id":1510491,"CreationDate":"2009-10-02T15:01:00.000","Title":"Is there any framework like RoR on Python 3000?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"One of the feature I like in RoR is the db management, it can hide all the sql statement, also, it is very easy to change different db in RoR, is there any similar framework in Python 3000?","AnswerCount":5,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":614,"Q_Id":1510084,"Users Score":0,"Answer":"Python 3 is not ready for practical use, because there is not yet enough libraries that have been updated to support Python 3. So the answer is: No.\nBut there are LOADS of them on Python 2. Tens, at least.\nDjango, Turbogears, BFG and of course the old man of the game: Zope. To tell which is best for you, you need to expand your requirements a lot.","Q_Score":1,"Tags":"python,ruby-on-rails,frameworks,python-3.x","A_Id":1510218,"CreationDate":"2009-10-02T15:01:00.000","Title":"Is there any framework like RoR on Python 3000?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"One of the feature I like in RoR is the db management, it can hide all the sql statement, also, it is very easy to change different db in RoR, is there any similar framework in Python 3000?","AnswerCount":5,"Available Count":3,"Score":0.0798297691,"is_accepted":false,"ViewCount":614,"Q_Id":1510084,"Users Score":2,"Answer":"I believe CherryPy is on the verge of being released for Python 3.X.","Q_Score":1,"Tags":"python,ruby-on-rails,frameworks,python-3.x","A_Id":1512245,"CreationDate":"2009-10-02T15:01:00.000","Title":"Is there any framework like RoR on Python 3000?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I want 3 columns to have 9 different values, like a list in Python.\nIs it possible? If not in SQLite, then on another database engine?","AnswerCount":3,"Available Count":1,"Score":1.0,"is_accepted":false,"ViewCount":25012,"Q_Id":1517771,"Users Score":12,"Answer":"Generally, you do this by stringifying the list (with repr()), and then saving the string.  On reading the string from the database, use eval() to re-create the list.  Be careful, though that you are certain no user-generated data can get into the column, or the eval() is a security risk.","Q_Score":12,"Tags":"python,sqlite","A_Id":1517795,"CreationDate":"2009-10-05T00:26:00.000","Title":"Is it possible to save a list of values into a SQLite column?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Hi I want some help in building a Phone book application on python and put it on google app engine. I am running a huge db of 2 million user lists and their contacts in phonebook. I want to upload all that data from my servers directly onto the google servers and then use a UI to retrieve the phone book contacts of each user based on his name.\nI am using MS SQL sever 2005 as my DB.\nPlease help in putting together this application.\nYour inputs are much appreciated.","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":420,"Q_Id":1518725,"Users Score":0,"Answer":"I think you're going to need to be more specific as to what problem you're having. As far as bulk loading goes, there's lots of bulkloader documentation around; or are you asking about model design? If so, we need to know more about how you plan to search for users. Do you need partial string matches? Sorting? Fuzzy matching?","Q_Score":0,"Tags":"python,google-app-engine,bulk-load","A_Id":1519020,"CreationDate":"2009-10-05T07:50:00.000","Title":"Need help in designing a phone book application on python running on google app engine","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I've been looking really hard at all of the way**(s)** one can develop web applications using Python.  For reference, we are using RHEL 64bit, apache, mod_wsgi.\nHistory:\n\nPHP + MySQL years ago\nPHP + Python 2.x + MySQL recently and current\nPython + PostgreSQL working on it\n\nWe use a great library for communicating between PHP and Python (interface in PHP, backend in Python)...  However, with a larger upcoming project starting, using 100% python may be very advantagous.\nWe typically prefer not to have a monolithic framework dictating how things are done.  A collection of useful helpers and utilities are much preferred (be it PHP or Python).\nQuestion 1:\nIn reading a number of answers from experienced Python users, I've seen Werkzeug recommended a number of times.   I would love it if several people with direct experience using Werkzeug to develop professional web applications could comment (in as much detail as their fingers feel like) why they use it, why they like it, and anything to watch out for.\nQuestion 2:\nIs there a version of Werkzeug that supports Python 3.1.1.  I've succefully installed mod_wsgi on Apache 2.2 with Python 3.1.1.\nIf there is not a version, what would it take to upgrade it to work on Python 3.1?\nNote: I've run 2to3 on the Werkzeug source code, and it does python-compile without \nEdit:\nThe project that we are starting is not slated to be finished until nearly a year from now.  At which point, I'm guessing Python 3.X will be a lot more mainstream.  Furthermore, considering that we are running the App (not distributing it), can anyone comment on the viability of bashing through some of the Python 3 issues now, so that when a year from now arrives, we are more-or-less already there?\nThoughts appreciated!","AnswerCount":3,"Available Count":3,"Score":0.0665680765,"is_accepted":false,"ViewCount":2259,"Q_Id":1523706,"Users Score":1,"Answer":"I can only answer question one:\nI started using it for some small webstuff but now moved on to rework larger apps with it. Why Werkzeug? The modular concept is really helpful. You can hook in modules as you like, make stuff easily context aware and you get good request file handling for free which is able to cope with 300mb+ files by not storing it in memory.\nDisadvantages... Well sometimes modularity needs some upfront thought (django f.ex. gives you everything all at once, stripping stuff out is hard to do there though) but for me it works fine.","Q_Score":2,"Tags":"python,python-3.x,werkzeug","A_Id":1622505,"CreationDate":"2009-10-06T05:13:00.000","Title":"Werkzeug in General, and in Python 3.1","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I've been looking really hard at all of the way**(s)** one can develop web applications using Python.  For reference, we are using RHEL 64bit, apache, mod_wsgi.\nHistory:\n\nPHP + MySQL years ago\nPHP + Python 2.x + MySQL recently and current\nPython + PostgreSQL working on it\n\nWe use a great library for communicating between PHP and Python (interface in PHP, backend in Python)...  However, with a larger upcoming project starting, using 100% python may be very advantagous.\nWe typically prefer not to have a monolithic framework dictating how things are done.  A collection of useful helpers and utilities are much preferred (be it PHP or Python).\nQuestion 1:\nIn reading a number of answers from experienced Python users, I've seen Werkzeug recommended a number of times.   I would love it if several people with direct experience using Werkzeug to develop professional web applications could comment (in as much detail as their fingers feel like) why they use it, why they like it, and anything to watch out for.\nQuestion 2:\nIs there a version of Werkzeug that supports Python 3.1.1.  I've succefully installed mod_wsgi on Apache 2.2 with Python 3.1.1.\nIf there is not a version, what would it take to upgrade it to work on Python 3.1?\nNote: I've run 2to3 on the Werkzeug source code, and it does python-compile without \nEdit:\nThe project that we are starting is not slated to be finished until nearly a year from now.  At which point, I'm guessing Python 3.X will be a lot more mainstream.  Furthermore, considering that we are running the App (not distributing it), can anyone comment on the viability of bashing through some of the Python 3 issues now, so that when a year from now arrives, we are more-or-less already there?\nThoughts appreciated!","AnswerCount":3,"Available Count":3,"Score":0.0665680765,"is_accepted":false,"ViewCount":2259,"Q_Id":1523706,"Users Score":1,"Answer":"I haven't used Werkzeug, so I can only answer question 2:\nNo, Werkzeug does not work on Python 3. In fact, very little works on Python 3 as of today. Porting is not difficult, but you can't port until all your third-party libraries have been ported, so progress is slow.\nOne big stopper has been setuptools, which is a very popular package to use. Setuptools is unmaintained, but there is a maintained fork called Distribute. Distribute was released with Python 3 support just a week or two ago. I hope package support for Python 3 will pick up now. But it will still be a long time, at least months probably a year or so, before any major project like Werkzeug will be ported to Python 3.","Q_Score":2,"Tags":"python,python-3.x,werkzeug","A_Id":1523934,"CreationDate":"2009-10-06T05:13:00.000","Title":"Werkzeug in General, and in Python 3.1","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I've been looking really hard at all of the way**(s)** one can develop web applications using Python.  For reference, we are using RHEL 64bit, apache, mod_wsgi.\nHistory:\n\nPHP + MySQL years ago\nPHP + Python 2.x + MySQL recently and current\nPython + PostgreSQL working on it\n\nWe use a great library for communicating between PHP and Python (interface in PHP, backend in Python)...  However, with a larger upcoming project starting, using 100% python may be very advantagous.\nWe typically prefer not to have a monolithic framework dictating how things are done.  A collection of useful helpers and utilities are much preferred (be it PHP or Python).\nQuestion 1:\nIn reading a number of answers from experienced Python users, I've seen Werkzeug recommended a number of times.   I would love it if several people with direct experience using Werkzeug to develop professional web applications could comment (in as much detail as their fingers feel like) why they use it, why they like it, and anything to watch out for.\nQuestion 2:\nIs there a version of Werkzeug that supports Python 3.1.1.  I've succefully installed mod_wsgi on Apache 2.2 with Python 3.1.1.\nIf there is not a version, what would it take to upgrade it to work on Python 3.1?\nNote: I've run 2to3 on the Werkzeug source code, and it does python-compile without \nEdit:\nThe project that we are starting is not slated to be finished until nearly a year from now.  At which point, I'm guessing Python 3.X will be a lot more mainstream.  Furthermore, considering that we are running the App (not distributing it), can anyone comment on the viability of bashing through some of the Python 3 issues now, so that when a year from now arrives, we are more-or-less already there?\nThoughts appreciated!","AnswerCount":3,"Available Count":3,"Score":0.1973753202,"is_accepted":false,"ViewCount":2259,"Q_Id":1523706,"Users Score":3,"Answer":"mod_wsgi for Python 3.x is also not ready. There is no satisfactory definition of WSGI for Python 3.x yet; the WEB-SIG are still bashing out the issues. mod_wsgi targets a guess at what might be in it, but there are very likely to be changes to both the spec and to standard libraries. Any web application you write today in Python 3.1 is likely to break in the future.\nIt's a bit of a shambles. Today, for webapps you can only realistically use Python 2.x.","Q_Score":2,"Tags":"python,python-3.x,werkzeug","A_Id":1525943,"CreationDate":"2009-10-06T05:13:00.000","Title":"Werkzeug in General, and in Python 3.1","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I have a web service with Django Framework.\nMy friend's project is a WIN32 program and also a MS-sql server.\nThe Win32 program currently has a login system that talks to a MS-sql for authentication.\nHowever, we would like to INTEGRATE this login system as one.\nPlease answer the 2 things:\n\nI want scrap the MS-SQL to use only the Django authentication system on the linux server. Can the WIN32 client talk to Django using a Django API (login)?\nIf not, what is the best way of combining the authentication?","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":203,"Q_Id":1529128,"Users Score":0,"Answer":"If the only thing the WIN32 app uses the MS-SQL Server for is Authentication\/Authorization then you could write a new Authentication\/Authorization provider that uses a set of Web Services (that you would have to create) that expose the Django provider.","Q_Score":1,"Tags":"python,windows,django,authentication,frameworks","A_Id":1529146,"CreationDate":"2009-10-07T01:59:00.000","Title":"Can a WIN32 program authenticate into Django authentication system, using MYSQL?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a web service with Django Framework.\nMy friend's project is a WIN32 program and also a MS-sql server.\nThe Win32 program currently has a login system that talks to a MS-sql for authentication.\nHowever, we would like to INTEGRATE this login system as one.\nPlease answer the 2 things:\n\nI want scrap the MS-SQL to use only the Django authentication system on the linux server. Can the WIN32 client talk to Django using a Django API (login)?\nIf not, what is the best way of combining the authentication?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":103,"Q_Id":1533259,"Users Score":1,"Answer":"The Win32 client can act like a web client to pass the user's credentials to the server.  You will want to store the session cookie you get once you are authenticated and use that cookie in all following requests","Q_Score":0,"Tags":"python,mysql,windows,django","A_Id":1581622,"CreationDate":"2009-10-07T02:00:00.000","Title":"Can a WIN32 program authenticate into Django authentication system, using MYSQL?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm coding a small piece of server software for the personal use of several users. Not hundreds, not thousands, but perhaps 3-10 at a time.\nSince it's a threaded server, SQLite doesn't work. It complains about threads like this:\n\nProgrammingError: SQLite objects created in a thread can only be used in that same thread.The object was created in thread id 140735085562848 and this is thread id 4301299712\n\nBesides, they say SQLite isn't great for concurrency anyhow.\nNow since I started working with Python 3 (and would rather continue using it) I can't seem to get the MySQL module to work properly and others seem equally frustrated.\nIn that case, is there any other DB option for Python 3 that I could consider?","AnswerCount":6,"Available Count":3,"Score":0.0333209931,"is_accepted":false,"ViewCount":3552,"Q_Id":1547365,"Users Score":1,"Answer":"pymongo works with Python 3 now.","Q_Score":3,"Tags":"python,database,python-3.x","A_Id":10863434,"CreationDate":"2009-10-10T08:09:00.000","Title":"A database for python 3?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm coding a small piece of server software for the personal use of several users. Not hundreds, not thousands, but perhaps 3-10 at a time.\nSince it's a threaded server, SQLite doesn't work. It complains about threads like this:\n\nProgrammingError: SQLite objects created in a thread can only be used in that same thread.The object was created in thread id 140735085562848 and this is thread id 4301299712\n\nBesides, they say SQLite isn't great for concurrency anyhow.\nNow since I started working with Python 3 (and would rather continue using it) I can't seem to get the MySQL module to work properly and others seem equally frustrated.\nIn that case, is there any other DB option for Python 3 that I could consider?","AnswerCount":6,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":3552,"Q_Id":1547365,"Users Score":0,"Answer":"You could create a new sqlite object in each thread, each using the same database file. For such a small number of users you might not come across the problems with concurrency, unless they are all writing to it very heavily.","Q_Score":3,"Tags":"python,database,python-3.x","A_Id":1547384,"CreationDate":"2009-10-10T08:09:00.000","Title":"A database for python 3?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm coding a small piece of server software for the personal use of several users. Not hundreds, not thousands, but perhaps 3-10 at a time.\nSince it's a threaded server, SQLite doesn't work. It complains about threads like this:\n\nProgrammingError: SQLite objects created in a thread can only be used in that same thread.The object was created in thread id 140735085562848 and this is thread id 4301299712\n\nBesides, they say SQLite isn't great for concurrency anyhow.\nNow since I started working with Python 3 (and would rather continue using it) I can't seem to get the MySQL module to work properly and others seem equally frustrated.\nIn that case, is there any other DB option for Python 3 that I could consider?","AnswerCount":6,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":3552,"Q_Id":1547365,"Users Score":0,"Answer":"Surely a pragmatic option is to just use one SQLite connection per thread.","Q_Score":3,"Tags":"python,database,python-3.x","A_Id":1550870,"CreationDate":"2009-10-10T08:09:00.000","Title":"A database for python 3?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am doing some pylons work in a virtual python enviorment, I want to use MySQL with SQLalchemy but I can't install the MySQLdb module on my virtual enviorment, I can't use easyinstall because I am using a version that was compiled for python 2.6 in a .exe format,  I tried running the install from inside the virtual enviorment but that did not work, any sugestions?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":442,"Q_Id":1557972,"Users Score":0,"Answer":"Ok Got it all figured out, After I installed the module on my normal python 2.6 install I went into my Python26 folder and low and behold I happened to find a file called MySQL-python-wininst which happened to be a list of all of the installed module files. Basicly it was two folders called MySQLdb and another called MySQL_python-1.2.2-py2.6.egg-info as well as three other files: _mysql.pyd, _mysql_exceptions.py, _mysql_exceptions.pyc. So I went into the folder where they were located (Python26\/Lib\/site-packages) and copied them to virtualenv's site-packages folder (env\/Lib\/site-packages) and the module was fully functional!\nNote: All paths are the defaults","Q_Score":0,"Tags":"python,mysql,pylons,module,virtualenv","A_Id":1563869,"CreationDate":"2009-10-13T02:43:00.000","Title":"Install custom modules in a python virtual enviroment","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I've produced a few Django sites but up until now I have been mapping individual views and URLs in urls.py.\nNow I've tried to create a small custom CMS but I'm having trouble with the URLs. I have a database table (SQLite3) which contains code for the pages like a column for header, one for right menu, one for content.... so on, so on. I also have a column for the URL. How do I get Django to call the information in the database table from the URL stored in the column rather than having to code a view and the URL for every page (which obviously defeats the purpose of a CMS)?\nIf someone can just point me at the right part of the docs or a site which explains this it would help a lot.\nThanks all.","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":3215,"Q_Id":1563088,"Users Score":1,"Answer":"Your question is a little bit twisted, but I think what you're asking for is something similar to how django.contrib.flatpages handles this. Basically it uses middleware to catch the 404 error and then looks to see if any of the flatpages have a URL field that matches.\nWe did this on one site where all of the URLs were made \"search engine friendly\". We overrode the save() method, munged the title into this_is_the_title.html (or whatever) and then stored that in a separate table that had a URL => object class\/id mapping.ng (this means it is listed before flatpages in the middleware list).","Q_Score":1,"Tags":"python,database,django,url,content-management-system","A_Id":1563359,"CreationDate":"2009-10-13T21:43:00.000","Title":"URLs stored in database for Django site","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I need to generate a list of insert statements (for postgresql) from html files, is there a library available for python to help me properly escape and quote the names\/values? in PHP i use PDO to do the escaping and quoting, is there any equivalent library for python?\nEdit: I need to generate a file with sql statements for execution later","AnswerCount":5,"Available Count":3,"Score":0.0399786803,"is_accepted":false,"ViewCount":50856,"Q_Id":1563967,"Users Score":1,"Answer":"Quoting parameters manually in general is a bad idea. What if there is a mistake in escaping rules? What if escape doesn't match used version of DB? What if you just forget to escape some parameter or erroneously assumed it can't contain data requiring escaping? That all may cause SQL injection vulnerability. Also, DB can have some restrictions on SQL statement length while you need to pass large data chunk for LOB column. That's why Python DB API and most databases (Python DB API module will transparently escape parameters, if database doesn't support this, as early MySQLdb did) allow passing parameters separated from statement:\n\n.execute(operation[,parameters])","Q_Score":17,"Tags":"python,sql,postgresql,psycopg2","A_Id":1564226,"CreationDate":"2009-10-14T02:31:00.000","Title":"Generate SQL statements with python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I need to generate a list of insert statements (for postgresql) from html files, is there a library available for python to help me properly escape and quote the names\/values? in PHP i use PDO to do the escaping and quoting, is there any equivalent library for python?\nEdit: I need to generate a file with sql statements for execution later","AnswerCount":5,"Available Count":3,"Score":0.0798297691,"is_accepted":false,"ViewCount":50856,"Q_Id":1563967,"Users Score":2,"Answer":"For robustness, I recommend using prepared statements to send user-entered values, no matter what language you use. :-)","Q_Score":17,"Tags":"python,sql,postgresql,psycopg2","A_Id":1563981,"CreationDate":"2009-10-14T02:31:00.000","Title":"Generate SQL statements with python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I need to generate a list of insert statements (for postgresql) from html files, is there a library available for python to help me properly escape and quote the names\/values? in PHP i use PDO to do the escaping and quoting, is there any equivalent library for python?\nEdit: I need to generate a file with sql statements for execution later","AnswerCount":5,"Available Count":3,"Score":1.0,"is_accepted":false,"ViewCount":50856,"Q_Id":1563967,"Users Score":13,"Answer":"SQLAlchemy provides a robust expression language for generating SQL from Python.\nLike every other well-designed abstraction layer, however, the queries it generates insert data through bind variables rather than through attempting to mix the query language and the data being inserted into a single string. This approach avoids massive security vulnerabilities and is otherwise The Right Thing.","Q_Score":17,"Tags":"python,sql,postgresql,psycopg2","A_Id":1564224,"CreationDate":"2009-10-14T02:31:00.000","Title":"Generate SQL statements with python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"When using the sqlite3 module in python, all elements of cursor.description except the column names are set to None, so this tuple cannot be used to find the column types for a query result (unlike other DB-API compliant modules). Is the only way to get the types of the columns to use pragma table_info(table_name).fetchall() to get a description of the table, store it in memory, and then match the column names from cursor.description to that overall table description?","AnswerCount":2,"Available Count":1,"Score":0.4621171573,"is_accepted":false,"ViewCount":3955,"Q_Id":1583350,"Users Score":5,"Answer":"No, it's not the only way. Alternatively, you can also fetch one row, iterate over it, and inspect the individual column Python objects and types. Unless the value is None (in which case the SQL field is NULL), this should give you a fairly precise indication what the database column type was.\nsqlite3 only uses sqlite3_column_decltype and sqlite3_column_type in one place, each, and neither are accessible to the Python application - so their is no \"direct\" way that you may have been looking for.","Q_Score":5,"Tags":"python,sqlite,python-db-api","A_Id":1583379,"CreationDate":"2009-10-17T22:11:00.000","Title":"sqlite3 and cursor.description","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I start feeling old fashioned when I see all these SQL generating database abstraction layers and all those ORMs out there, although I am far from being old. I understand the need for them, but their use spreads to places they normally don't belong to.\nI firmly believe that using database abstraction layers for SQL generation is not the right way of writing database applications that should run on multiple database engines, especially when you throw in really expensive databases like Oracle. And this is more or less global, it doesn't apply to only a few languages.\nJust a simple example, using query pagination and insertion: when using Oracle one could use the FIRST_ROWS and APPEND hints(where appropriate). Going to advanced examples I could mention putting in the database lots of Stored Procedures\/Packages where it makes sense. And those are different for every RDBMS.\nBy using only a limited set of features, commonly available to many RDBMS one doesn't exploit the possibilities that those expensive and advanced database engines have to offers.\nSo getting back to the heart of the question: how do you develop PHP, Python, Ruby etc. applications that should run on multiple database engines?\nI am especially interested hearing how you separate\/use the queries that are especially written for running on a single RDBMS. Say you've got a statement that should run on 3 RDBMS: Oracle, DB2 and Sql Server and for each of these you write a separate SQL statement in order to make use of all features this RDBMS has to offer. How do you do it?\nLetting this aside, what is you opinion walking this path? Is it worth it in your experience? Why? Why not?","AnswerCount":4,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":369,"Q_Id":1586008,"Users Score":0,"Answer":"It would be great if code written for one platform would work on every other without any modification whatsoever, but this is usually not the case and probably never will be. What the current frameworks do is about all anyone can.","Q_Score":2,"Tags":"php,python,ruby-on-rails,database","A_Id":1586035,"CreationDate":"2009-10-18T20:56:00.000","Title":"PHP, Python, Ruby application with multiple RDBMS","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I start feeling old fashioned when I see all these SQL generating database abstraction layers and all those ORMs out there, although I am far from being old. I understand the need for them, but their use spreads to places they normally don't belong to.\nI firmly believe that using database abstraction layers for SQL generation is not the right way of writing database applications that should run on multiple database engines, especially when you throw in really expensive databases like Oracle. And this is more or less global, it doesn't apply to only a few languages.\nJust a simple example, using query pagination and insertion: when using Oracle one could use the FIRST_ROWS and APPEND hints(where appropriate). Going to advanced examples I could mention putting in the database lots of Stored Procedures\/Packages where it makes sense. And those are different for every RDBMS.\nBy using only a limited set of features, commonly available to many RDBMS one doesn't exploit the possibilities that those expensive and advanced database engines have to offers.\nSo getting back to the heart of the question: how do you develop PHP, Python, Ruby etc. applications that should run on multiple database engines?\nI am especially interested hearing how you separate\/use the queries that are especially written for running on a single RDBMS. Say you've got a statement that should run on 3 RDBMS: Oracle, DB2 and Sql Server and for each of these you write a separate SQL statement in order to make use of all features this RDBMS has to offer. How do you do it?\nLetting this aside, what is you opinion walking this path? Is it worth it in your experience? Why? Why not?","AnswerCount":4,"Available Count":3,"Score":0.0996679946,"is_accepted":false,"ViewCount":369,"Q_Id":1586008,"Users Score":2,"Answer":"If you want to leverage the bells and whistles of various RDBMSes, you can certainly do it.  Just apply standard OO Principles.  Figure out what kind of API your persistence layer will need to provide.  \nYou'll end up writing a set of isomorphic persistence adapter classes.  From the perspective of your model code (which will be calling adapter methods to load and store data), these classes are identical.  Writing good test coverage should be easy, and good tests will make life a lot easier.  Deciding how much abstraction is provided by the persistence adapters is the trickiest part, and is largely application-specific.\nAs for whether this is worth the trouble: it depends.  It's a good exercise if you've never done it before.  It may be premature if you don't actually know for sure what your target databases are.  \nA good strategy might be to implement two persistence adapters to start.  Let's say you expect the most common back end will be MySQL.  Implement one adapter tuned for MySQL.  Implement a second that uses your database abstraction library of choice, and uses only standard and widely available SQL features.  Now you've got support for a ton of back ends (everything supported by your abstraction library of choice), plus tuned support for mySQL.  If you decide you then want to provide an optimized adapter from Oracle, you can implement it at your leisure, and you'll know that your application can support swappable database back-ends.","Q_Score":2,"Tags":"php,python,ruby-on-rails,database","A_Id":1586105,"CreationDate":"2009-10-18T20:56:00.000","Title":"PHP, Python, Ruby application with multiple RDBMS","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I start feeling old fashioned when I see all these SQL generating database abstraction layers and all those ORMs out there, although I am far from being old. I understand the need for them, but their use spreads to places they normally don't belong to.\nI firmly believe that using database abstraction layers for SQL generation is not the right way of writing database applications that should run on multiple database engines, especially when you throw in really expensive databases like Oracle. And this is more or less global, it doesn't apply to only a few languages.\nJust a simple example, using query pagination and insertion: when using Oracle one could use the FIRST_ROWS and APPEND hints(where appropriate). Going to advanced examples I could mention putting in the database lots of Stored Procedures\/Packages where it makes sense. And those are different for every RDBMS.\nBy using only a limited set of features, commonly available to many RDBMS one doesn't exploit the possibilities that those expensive and advanced database engines have to offers.\nSo getting back to the heart of the question: how do you develop PHP, Python, Ruby etc. applications that should run on multiple database engines?\nI am especially interested hearing how you separate\/use the queries that are especially written for running on a single RDBMS. Say you've got a statement that should run on 3 RDBMS: Oracle, DB2 and Sql Server and for each of these you write a separate SQL statement in order to make use of all features this RDBMS has to offer. How do you do it?\nLetting this aside, what is you opinion walking this path? Is it worth it in your experience? Why? Why not?","AnswerCount":4,"Available Count":3,"Score":1.2,"is_accepted":true,"ViewCount":369,"Q_Id":1586008,"Users Score":2,"Answer":"You cannot eat a cake and have it, choose on of the following options.\n\nUse your database abstraction layer whenever you can and in the rare cases when you have a need for a hand-made query (eg. performance reasons) stick to the lowest common denominator and don't use stored procedures or any proprietary extensions that you database has to offer. In this case deploying the application on a different RDBMS should be trivial.\nUse the full power of your expensive RDBMS, but take into account that your application won't be easily portable. When the need arises you will have to spend considerable effort on porting and maintenance. Of course a decent layered design encapsulating all the differences in a single module or class will help in this endeavor.\n\nIn other words you should consider how probable is it that your application will be deployed to multiple RDBMSes and make an informed choice.","Q_Score":2,"Tags":"php,python,ruby-on-rails,database","A_Id":1587887,"CreationDate":"2009-10-18T20:56:00.000","Title":"PHP, Python, Ruby application with multiple RDBMS","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm looking at using CouchDB for one project and the GAE app engine datastore in the other.  For relational stuff I tend to use postgres, although I much prefer an ORM.  \nAnyway, what use cases suit non relational datastores best?","AnswerCount":3,"Available Count":2,"Score":0.1325487884,"is_accepted":false,"ViewCount":587,"Q_Id":1588708,"Users Score":2,"Answer":"Consider the situation where you have many entity types but few instances of each entity. In this case you will have many tables each with a few records so a relational approach is not suitable.","Q_Score":3,"Tags":"python,google-app-engine,couchdb","A_Id":1588748,"CreationDate":"2009-10-19T13:36:00.000","Title":"What are the use cases for non relational datastores?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I'm looking at using CouchDB for one project and the GAE app engine datastore in the other.  For relational stuff I tend to use postgres, although I much prefer an ORM.  \nAnyway, what use cases suit non relational datastores best?","AnswerCount":3,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":587,"Q_Id":1588708,"Users Score":0,"Answer":"In some cases that are simply nice. ZODB is a Python-only object database, that is so well-integrated with Python that you can simply forget that it's there. You don't have to bother about it, most of the time.","Q_Score":3,"Tags":"python,google-app-engine,couchdb","A_Id":1589186,"CreationDate":"2009-10-19T13:36:00.000","Title":"What are the use cases for non relational datastores?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I have a python program that does something like this:\n\nRead a row from a csv file.\nDo some transformations on it.\nBreak it up into the actual rows as they would be written to the database.\nWrite those rows to individual csv files.\nGo back to step 1 unless the file has been totally read.\nRun SQL*Loader and load those files into the database.\n\nStep 6 isn't really taking much time at all.  It seems to be step 4 that's taking up most of the time.  For the most part, I'd like to optimize this for handling a set of records in the low millions running on a quad-core server with a RAID setup of some kind.\nThere are a few ideas that I have to solve this:\n\nRead the entire file from step one (or at least read it in very large chunks) and write the file to disk as a whole or in very large chunks.  The idea being that the hard disk would spend less time going back and forth between files.  Would this do anything that buffering wouldn't?\nParallelize steps 1, 2&3, and 4 into separate processes.  This would make steps 1, 2, and 3 not have to wait on 4 to complete.\nBreak the load file up into separate chunks and process them in parallel.  The rows don't need to be handled in any sequential order.  This would likely need to be combined with step 2 somehow.\n\nOf course, the correct answer to this question is \"do what you find to be the fastest by testing.\"  However, I'm mainly trying to get an idea of where I should spend my time first.  Does anyone with more experience in these matters have any advice?","AnswerCount":7,"Available Count":5,"Score":0.0855049882,"is_accepted":false,"ViewCount":2504,"Q_Id":1594604,"Users Score":3,"Answer":"If you are I\/O bound, the best way I have found to optimize is to read or write the entire file into\/out of memory at once, then operate out of RAM from there on.\nWith extensive testing I found that my runtime eded up bound not by the amount of data I read from\/wrote to disk, but by the number of I\/O operations I used to do it. That is what you need to optimize.\nI don't know Python, but if there is a way to tell it to write the whole file out of RAM in one go, rather than issuing a separate I\/O for each byte, that's what you need to do.\nOf course the drawback to this is that files can be considerably larger than available RAM. There are lots of ways to deal with that, but that is another question for another time.","Q_Score":3,"Tags":"python,performance,optimization,file-io","A_Id":1594704,"CreationDate":"2009-10-20T13:27:00.000","Title":"How should I optimize this filesystem I\/O bound program?","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a python program that does something like this:\n\nRead a row from a csv file.\nDo some transformations on it.\nBreak it up into the actual rows as they would be written to the database.\nWrite those rows to individual csv files.\nGo back to step 1 unless the file has been totally read.\nRun SQL*Loader and load those files into the database.\n\nStep 6 isn't really taking much time at all.  It seems to be step 4 that's taking up most of the time.  For the most part, I'd like to optimize this for handling a set of records in the low millions running on a quad-core server with a RAID setup of some kind.\nThere are a few ideas that I have to solve this:\n\nRead the entire file from step one (or at least read it in very large chunks) and write the file to disk as a whole or in very large chunks.  The idea being that the hard disk would spend less time going back and forth between files.  Would this do anything that buffering wouldn't?\nParallelize steps 1, 2&3, and 4 into separate processes.  This would make steps 1, 2, and 3 not have to wait on 4 to complete.\nBreak the load file up into separate chunks and process them in parallel.  The rows don't need to be handled in any sequential order.  This would likely need to be combined with step 2 somehow.\n\nOf course, the correct answer to this question is \"do what you find to be the fastest by testing.\"  However, I'm mainly trying to get an idea of where I should spend my time first.  Does anyone with more experience in these matters have any advice?","AnswerCount":7,"Available Count":5,"Score":0.0285636566,"is_accepted":false,"ViewCount":2504,"Q_Id":1594604,"Users Score":1,"Answer":"Use buffered writes for step 4.\nWrite a simple function that simply appends the output onto a string, checks the string length, and only writes when you have enough which should be some multiple of 4k bytes. I would say start with 32k buffers and time it.\nYou would have one buffer per file, so that most \"writes\" won't actually hit the disk.","Q_Score":3,"Tags":"python,performance,optimization,file-io","A_Id":1595358,"CreationDate":"2009-10-20T13:27:00.000","Title":"How should I optimize this filesystem I\/O bound program?","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a python program that does something like this:\n\nRead a row from a csv file.\nDo some transformations on it.\nBreak it up into the actual rows as they would be written to the database.\nWrite those rows to individual csv files.\nGo back to step 1 unless the file has been totally read.\nRun SQL*Loader and load those files into the database.\n\nStep 6 isn't really taking much time at all.  It seems to be step 4 that's taking up most of the time.  For the most part, I'd like to optimize this for handling a set of records in the low millions running on a quad-core server with a RAID setup of some kind.\nThere are a few ideas that I have to solve this:\n\nRead the entire file from step one (or at least read it in very large chunks) and write the file to disk as a whole or in very large chunks.  The idea being that the hard disk would spend less time going back and forth between files.  Would this do anything that buffering wouldn't?\nParallelize steps 1, 2&3, and 4 into separate processes.  This would make steps 1, 2, and 3 not have to wait on 4 to complete.\nBreak the load file up into separate chunks and process them in parallel.  The rows don't need to be handled in any sequential order.  This would likely need to be combined with step 2 somehow.\n\nOf course, the correct answer to this question is \"do what you find to be the fastest by testing.\"  However, I'm mainly trying to get an idea of where I should spend my time first.  Does anyone with more experience in these matters have any advice?","AnswerCount":7,"Available Count":5,"Score":1.2,"is_accepted":true,"ViewCount":2504,"Q_Id":1594604,"Users Score":3,"Answer":"Python already does IO buffering and the OS should handle both prefetching the input file and delaying writes until it needs the RAM for something else or just gets uneasy about having dirty data in RAM for too long.  Unless you force the OS to write them immediately, like closing the file after each write or opening the file in O_SYNC mode.\nIf the OS isn't doing the right thing, you can try raising the buffer size (third parameter to open()). For some guidance on appropriate values given a 100MB\/s 10ms latency IO system a 1MB IO size will result in approximately 50% latency overhead, while a 10MB IO size will result in 9% overhead. If its still IO bound, you probably just need more bandwidth. Use your OS specific tools to check what kind of bandwidth you are getting to\/from the disks.\nAlso useful is to check if step 4 is taking a lot of time executing or waiting on IO. If it's executing you'll need to spend more time checking which part is the culprit and optimize that, or split out the work to different processes.","Q_Score":3,"Tags":"python,performance,optimization,file-io","A_Id":1595626,"CreationDate":"2009-10-20T13:27:00.000","Title":"How should I optimize this filesystem I\/O bound program?","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a python program that does something like this:\n\nRead a row from a csv file.\nDo some transformations on it.\nBreak it up into the actual rows as they would be written to the database.\nWrite those rows to individual csv files.\nGo back to step 1 unless the file has been totally read.\nRun SQL*Loader and load those files into the database.\n\nStep 6 isn't really taking much time at all.  It seems to be step 4 that's taking up most of the time.  For the most part, I'd like to optimize this for handling a set of records in the low millions running on a quad-core server with a RAID setup of some kind.\nThere are a few ideas that I have to solve this:\n\nRead the entire file from step one (or at least read it in very large chunks) and write the file to disk as a whole or in very large chunks.  The idea being that the hard disk would spend less time going back and forth between files.  Would this do anything that buffering wouldn't?\nParallelize steps 1, 2&3, and 4 into separate processes.  This would make steps 1, 2, and 3 not have to wait on 4 to complete.\nBreak the load file up into separate chunks and process them in parallel.  The rows don't need to be handled in any sequential order.  This would likely need to be combined with step 2 somehow.\n\nOf course, the correct answer to this question is \"do what you find to be the fastest by testing.\"  However, I'm mainly trying to get an idea of where I should spend my time first.  Does anyone with more experience in these matters have any advice?","AnswerCount":7,"Available Count":5,"Score":0.057080742,"is_accepted":false,"ViewCount":2504,"Q_Id":1594604,"Users Score":2,"Answer":"Can you use a ramdisk for step 4? Low millions sounds doable if the rows are less than a couple of kB or so.","Q_Score":3,"Tags":"python,performance,optimization,file-io","A_Id":1597062,"CreationDate":"2009-10-20T13:27:00.000","Title":"How should I optimize this filesystem I\/O bound program?","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a python program that does something like this:\n\nRead a row from a csv file.\nDo some transformations on it.\nBreak it up into the actual rows as they would be written to the database.\nWrite those rows to individual csv files.\nGo back to step 1 unless the file has been totally read.\nRun SQL*Loader and load those files into the database.\n\nStep 6 isn't really taking much time at all.  It seems to be step 4 that's taking up most of the time.  For the most part, I'd like to optimize this for handling a set of records in the low millions running on a quad-core server with a RAID setup of some kind.\nThere are a few ideas that I have to solve this:\n\nRead the entire file from step one (or at least read it in very large chunks) and write the file to disk as a whole or in very large chunks.  The idea being that the hard disk would spend less time going back and forth between files.  Would this do anything that buffering wouldn't?\nParallelize steps 1, 2&3, and 4 into separate processes.  This would make steps 1, 2, and 3 not have to wait on 4 to complete.\nBreak the load file up into separate chunks and process them in parallel.  The rows don't need to be handled in any sequential order.  This would likely need to be combined with step 2 somehow.\n\nOf course, the correct answer to this question is \"do what you find to be the fastest by testing.\"  However, I'm mainly trying to get an idea of where I should spend my time first.  Does anyone with more experience in these matters have any advice?","AnswerCount":7,"Available Count":5,"Score":0.0285636566,"is_accepted":false,"ViewCount":2504,"Q_Id":1594604,"Users Score":1,"Answer":"Isn't it possible to collect a few thousand rows in ram, then go directly to the database server and execute them? \nThis would remove the save to and load from the disk that step 4 entails.\nIf the database server is transactional, this is also a safe way to do it - just have the database begin before your first row and commit after the last.","Q_Score":3,"Tags":"python,performance,optimization,file-io","A_Id":1597281,"CreationDate":"2009-10-20T13:27:00.000","Title":"How should I optimize this filesystem I\/O bound program?","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Two libraries for Mysql.\nI've always used _mysql because it's simpler. \nCan anyone tell me the difference, and why I should use which one in certain occasions?","AnswerCount":3,"Available Count":1,"Score":0.3215127375,"is_accepted":false,"ViewCount":4941,"Q_Id":1620575,"Users Score":5,"Answer":"_mysql is the one-to-one mapping of the rough mysql API. On top of it, the DB-API is built, handling things using cursors and so on. \nIf you are used to the low-level mysql API provided by libmysqlclient, then the _mysql module is what you need, but as another answer says, there's no real need to go so low-level. You can work with the DB-API and behave just fine, with the added benefit that the DB-API is backend-independent.","Q_Score":11,"Tags":"python,mysql","A_Id":1620642,"CreationDate":"2009-10-25T10:37:00.000","Title":"Python: advantages and disvantages of _mysql vs MySQLdb?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"On my website I store user pictures in a simple manner such as:\n\"image\/user_1.jpg\".\nI don't want visitors to be able to view images on my server just by trying user_ids. (Ex: www.mydomain.com\/images\/user_2.jpg, www.mydomain.com\/images\/user_3.jpg, so on...)\nSo far I have three solutions in mind:\n\nI tried using .htaccess to password protect the \"images\" folder. That helped me up to some point but some of the images started popping up a username and password request on my htmls (while amazingly some images did not) so this seems to be an unpredictable method.\nI can start converting my user_id's to an md5 hash with some salt. The images would be named as: \/image\/user_e4d909c290d0fb1ca068ffaddf22cbd0.jpg. I don't like this solution. It makes the file system way complicated.\nor I can user PHP's readfile() function or maybe something similar in Perl or Python. For instance I could pass a password using an md5 string to validate visitors as loggedin users with access to that image.\n\nI'm leaning towards option 3 but with a Perl or Python angle (assuming they would be faster than PHP). However I would like to see other ideas on the matter. Maybe there is a simple .htaccess trick to this? \nBasically all I want to make sure is that no one can view images from my website unless the images are directly called from within htmls hosted on my site.\nThanks a lot,\nHaluk","AnswerCount":5,"Available Count":2,"Score":1.0,"is_accepted":false,"ViewCount":4621,"Q_Id":1623311,"Users Score":6,"Answer":"Any method you choose to determine the source of a request is only as reliable as the HTTP_REFERER information that is sent by the user's browser, which is not very. Requiring authentication is the only good way to protect content.","Q_Score":2,"Tags":"php,python,linux,perl","A_Id":1623338,"CreationDate":"2009-10-26T06:06:00.000","Title":"Restrict access to images on my website except through my own htmls","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"On my website I store user pictures in a simple manner such as:\n\"image\/user_1.jpg\".\nI don't want visitors to be able to view images on my server just by trying user_ids. (Ex: www.mydomain.com\/images\/user_2.jpg, www.mydomain.com\/images\/user_3.jpg, so on...)\nSo far I have three solutions in mind:\n\nI tried using .htaccess to password protect the \"images\" folder. That helped me up to some point but some of the images started popping up a username and password request on my htmls (while amazingly some images did not) so this seems to be an unpredictable method.\nI can start converting my user_id's to an md5 hash with some salt. The images would be named as: \/image\/user_e4d909c290d0fb1ca068ffaddf22cbd0.jpg. I don't like this solution. It makes the file system way complicated.\nor I can user PHP's readfile() function or maybe something similar in Perl or Python. For instance I could pass a password using an md5 string to validate visitors as loggedin users with access to that image.\n\nI'm leaning towards option 3 but with a Perl or Python angle (assuming they would be faster than PHP). However I would like to see other ideas on the matter. Maybe there is a simple .htaccess trick to this? \nBasically all I want to make sure is that no one can view images from my website unless the images are directly called from within htmls hosted on my site.\nThanks a lot,\nHaluk","AnswerCount":5,"Available Count":2,"Score":0.0798297691,"is_accepted":false,"ViewCount":4621,"Q_Id":1623311,"Users Score":2,"Answer":"You are right considering option #3. Use service script that would validate user and readfile() an image. Be sure to set correct Content-Type HTTP header via header() function prior to serving an image. For better isolation images should be put above web root directory, or protected by well written .htaccess rules - there is definitely a way of protecting files and\/or directories this way.","Q_Score":2,"Tags":"php,python,linux,perl","A_Id":1623325,"CreationDate":"2009-10-26T06:06:00.000","Title":"Restrict access to images on my website except through my own htmls","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Is there an easy way to reset a django database (i.e. drop all data\/tables, create new tables and create indexes) without loading fixture data afterwords? What I want to have is just an empty database because all data is loaded from another source (a kind of a post-processed backup).\nI know that this could  be achieved by piping the output of the manage sql... commands to manage dbshell, but this relies on manage dbshelland is kind of hacky...\nAre there any other ways to do this?\nEdit:\nmanage reset will do it, but is there a command like reset that doesn't need the application names as parameters?","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1667,"Q_Id":1645310,"Users Score":2,"Answer":"As far as I know, the fixtures (in initial_data file) are automatically loaded after manage.py syndcb and not after reset. So, if you do a manage.py reset yourapp it should not load the fixtures. Hmm?","Q_Score":1,"Tags":"python,database,django,fixtures","A_Id":1645519,"CreationDate":"2009-10-29T17:26:00.000","Title":"Django db reset without loading fixtures","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a database which I regularly need to import large amounts of data into via some python scripts. Compacted, the data for a single months imports takes about 280mb, but during the import file size swells to over a gb.\nGiven the 2gb size limit on mdb files, this is a bit of a concern. Apart from breaking the inserts into chunks and compacting inbetween each, are there any techniques for avoiding the increase in file size?\nNote that no temporary tables are being created\/deleted during the process: just inserts into existing tables.\nAnd to forstall the inevitable comments: yes, I am required to store this data in Access 2003. No, I can't upgrade to Access 2007.\nIf it could help, I could preprocess in sqlite.\nEdit:\nJust to add some further information (some already listed in my comments):\n\nThe data is being generated in Python on a table by table basis, and then all of the records for that table batch inserted via odbc\nAll processing is happening in Python: all the mdb file is doing is storing the data\nAll of the fields being inserted are valid fields (none are being excluded due to unique key violations, etc.)\n\nGiven the above, I'll be looking into how to disable row level locking via odbc and considering presorting the data and\/or removing then reinstating indexes. Thanks for the suggestions.\nAny further suggestions still welcome.","AnswerCount":6,"Available Count":4,"Score":0.0333209931,"is_accepted":false,"ViewCount":3989,"Q_Id":1650856,"Users Score":1,"Answer":"Is your script executing a single INSERT statement per row of data? If so, pre-processing the data into a text file of many rows that could then be inserted with a single INSERT statement might improve the efficiency and cut down on the accumulating temporary crud that's causing it to bloat. \nYou might also make sure the INSERT is being executed without transactions. Whether or not that happens implicitly depends on the Jet version and the data interface library you're using to accomplish the task. By explicitly making sure it's off, you could improve the situation.\nAnother possibility is to drop the indexes before the insert, compact, run the insert, compact, re-instate the indexes, and run a final compact.","Q_Score":1,"Tags":"python,ms-access","A_Id":1652783,"CreationDate":"2009-10-30T16:21:00.000","Title":"MS-Access Database getting very large during inserts","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a database which I regularly need to import large amounts of data into via some python scripts. Compacted, the data for a single months imports takes about 280mb, but during the import file size swells to over a gb.\nGiven the 2gb size limit on mdb files, this is a bit of a concern. Apart from breaking the inserts into chunks and compacting inbetween each, are there any techniques for avoiding the increase in file size?\nNote that no temporary tables are being created\/deleted during the process: just inserts into existing tables.\nAnd to forstall the inevitable comments: yes, I am required to store this data in Access 2003. No, I can't upgrade to Access 2007.\nIf it could help, I could preprocess in sqlite.\nEdit:\nJust to add some further information (some already listed in my comments):\n\nThe data is being generated in Python on a table by table basis, and then all of the records for that table batch inserted via odbc\nAll processing is happening in Python: all the mdb file is doing is storing the data\nAll of the fields being inserted are valid fields (none are being excluded due to unique key violations, etc.)\n\nGiven the above, I'll be looking into how to disable row level locking via odbc and considering presorting the data and\/or removing then reinstating indexes. Thanks for the suggestions.\nAny further suggestions still welcome.","AnswerCount":6,"Available Count":4,"Score":-0.0333209931,"is_accepted":false,"ViewCount":3989,"Q_Id":1650856,"Users Score":-1,"Answer":"File --> Options --> Current Database -> Check below options\n* Use the Cache format that is compatible with Microsoft Access 2010 and later\n   * Clear Cache on Close\nThen, you file will be saved by compacting to the original size.","Q_Score":1,"Tags":"python,ms-access","A_Id":31059064,"CreationDate":"2009-10-30T16:21:00.000","Title":"MS-Access Database getting very large during inserts","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a database which I regularly need to import large amounts of data into via some python scripts. Compacted, the data for a single months imports takes about 280mb, but during the import file size swells to over a gb.\nGiven the 2gb size limit on mdb files, this is a bit of a concern. Apart from breaking the inserts into chunks and compacting inbetween each, are there any techniques for avoiding the increase in file size?\nNote that no temporary tables are being created\/deleted during the process: just inserts into existing tables.\nAnd to forstall the inevitable comments: yes, I am required to store this data in Access 2003. No, I can't upgrade to Access 2007.\nIf it could help, I could preprocess in sqlite.\nEdit:\nJust to add some further information (some already listed in my comments):\n\nThe data is being generated in Python on a table by table basis, and then all of the records for that table batch inserted via odbc\nAll processing is happening in Python: all the mdb file is doing is storing the data\nAll of the fields being inserted are valid fields (none are being excluded due to unique key violations, etc.)\n\nGiven the above, I'll be looking into how to disable row level locking via odbc and considering presorting the data and\/or removing then reinstating indexes. Thanks for the suggestions.\nAny further suggestions still welcome.","AnswerCount":6,"Available Count":4,"Score":0.0996679946,"is_accepted":false,"ViewCount":3989,"Q_Id":1650856,"Users Score":3,"Answer":"A common trick, if feasible with regard to the schema and semantics of the application, is to have several MDB files with Linked tables.\nAlso, the way the insertions take place matters with regards to the way the file size balloons...  For example: batched, vs. one\/few records at a time, sorted (relative to particular index(es)), number of indexes  (as you mentioned readily dropping some during the insert phase)...\nTentatively a pre-processing approach with say storing of new rows to a separate linked table, heap fashion (no indexes), then sorting\/indexing this data is a minimal fashion, and \"bulk loading\" it to its real destination.  Similar pre-processing in SQLite (has hinted in question) would serve the serve purpose. Keeping it \"ALL MDB\" is maybe easier (fewer languages\/processes to learn, fewer inter-op issues [hopefuly ;-)]...)\nEDIT: on why inserting records in a sorted\/bulk fashion may slow down the MDB file's growth (question from Tony Toews)\nOne of the reasons for MDB files' propensity to grow more quickly than the rate at which text\/data added to them (and their counterpart ability to be easily compacted back down) is that as information is added, some of the nodes that constitute the indexes have to be re-arranged (for overflowing \/ rebalancing etc.). Such management of the nodes seems to be implemented in a fashion which favors speed over disk space and harmony, and this approach typically serves simple applications \/ small data rather well. I do not know the specific logic in use for such management but I suspect that in several cases, node operations cause a particular node (or much of it) to be copied anew, and the old location simply being marked as free\/unused but not deleted\/compacted\/reused.  I do have \"clinical\" (if only a bit outdated) evidence that by performing inserts in bulk we essentially limit the number of opportunities for such duplication to occur and hence we slow the growth.\nEDIT again: After reading and discussing things from Tony Toews and Albert Kallal it appears that a possibly more significant source of bloat, in particular in Jet Engine 4.0, is the way locking is implemented. It is therefore important to set the database in single user mode to avoid this.  (Read Tony's and Albert's response for more details.","Q_Score":1,"Tags":"python,ms-access","A_Id":1650897,"CreationDate":"2009-10-30T16:21:00.000","Title":"MS-Access Database getting very large during inserts","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a database which I regularly need to import large amounts of data into via some python scripts. Compacted, the data for a single months imports takes about 280mb, but during the import file size swells to over a gb.\nGiven the 2gb size limit on mdb files, this is a bit of a concern. Apart from breaking the inserts into chunks and compacting inbetween each, are there any techniques for avoiding the increase in file size?\nNote that no temporary tables are being created\/deleted during the process: just inserts into existing tables.\nAnd to forstall the inevitable comments: yes, I am required to store this data in Access 2003. No, I can't upgrade to Access 2007.\nIf it could help, I could preprocess in sqlite.\nEdit:\nJust to add some further information (some already listed in my comments):\n\nThe data is being generated in Python on a table by table basis, and then all of the records for that table batch inserted via odbc\nAll processing is happening in Python: all the mdb file is doing is storing the data\nAll of the fields being inserted are valid fields (none are being excluded due to unique key violations, etc.)\n\nGiven the above, I'll be looking into how to disable row level locking via odbc and considering presorting the data and\/or removing then reinstating indexes. Thanks for the suggestions.\nAny further suggestions still welcome.","AnswerCount":6,"Available Count":4,"Score":0.0996679946,"is_accepted":false,"ViewCount":3989,"Q_Id":1650856,"Users Score":3,"Answer":"One thing to watch out for is  records which are present in the append queries but aren't inserted into the data due to duplicate key values, null required fields, etc.  Access will allocate the space taken by the records which aren't inserted.\nAbout the only significant thing I'm aware of is to ensure you have exclusive access to the database file.  Which might be impossible if doing this during the day.   I noticed a change in behavior from Jet 3.51 (used in Access 97) to Jet 4.0 (used in Access 2000) when the Access MDBs started getting a lot larger when doing record appends.  I think that if the MDB is being used by multiple folks then records are inserted once per 4k page rather than as many as can be stuffed into a page.  Likely because this made index insert\/update operations faster. \nNow compacting does indeed put as many records in the same 4k page as possible but that isn't of help to you.","Q_Score":1,"Tags":"python,ms-access","A_Id":1651412,"CreationDate":"2009-10-30T16:21:00.000","Title":"MS-Access Database getting very large during inserts","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am after a Python module for Google App Engine that abstracts away limitations of the GQL.\nSpecifically I want to store big files (> 1MB) and retrieve all records for a model (> 1000). I have my own code that handles this at present but would prefer to build on existing work, if available.\nThanks","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":78,"Q_Id":1658829,"Users Score":1,"Answer":"I'm not aware of any libraries that do that. You may want to reconsider what you're doing, at least in terms of retrieving more than 1000 results - those operations are not available because they're expensive, and needing to evade them is usually (though not always) a sign that you need to rearchitect your app to do less work at read time.","Q_Score":0,"Tags":"python,google-app-engine,gql","A_Id":1660404,"CreationDate":"2009-11-01T23:54:00.000","Title":"module to abstract limitations of GQL","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":0},{"Question":"So I've been building django applications for a while now, and drinking the cool-aid and all: only using the ORM and never writing custom SQL.\nThe main page of the site (the primary interface where users will spend 80% - 90% of their time) was getting slow once you have a large amount of user specific content (ie photos, friends, other data, etc)\nSo I popped in the sql logger (was pre-installed with pinax, I just enabled it in the settings) and imagine my surprise when it reported over 500 database queries!! With hand coded sql I hardly ever ran more than 50 on the most complex pages.\nIn hindsight it's not all together surprising, but it seems that this can't be good.\n...even if only a dozen or so of the queries take 1ms+\nSo I'm wondering, how much overhead is there on a round trip to mysql? django and mysql are running on the same server so there shouldn't be any networking related overhead.","AnswerCount":4,"Available Count":4,"Score":0.049958375,"is_accepted":false,"ViewCount":1620,"Q_Id":1689031,"Users Score":1,"Answer":"There is always overhead in database calls, in your case the overhead is not that bad because the application and database are on the same machine so there is no network latency but there is still a significant cost.\nWhen you make a request to the database it has to prepare to service that request by doing a number of things including: \n\nAllocating resources (memory buffers, temp tables etc) to the database server connection\/thread that will handle the request, \nDe-serializing the sql and parameters (this is necessary even on one machine as this is an inter-process request unless you are using an embeded database)\nChecking whether the query exists in the query cache if not optimise it and put it in the cache.\n\n\nNote also that if your queries are not parametrised (that is the values are not separated from the SQL) this may result in cache misses for statements that should be the same meaning that each request results in the query being analysed and optimized each time.\n\nProcess the query.\nPrepare and return the results to the client.\n\nThis is just an overview of the kinds of things the most database management systems do to process an SQL request. You incur this overhead 500 times even if the the query itself runs relatively quickly. Bottom line database interactions even to local database are not as cheap as you might expect.","Q_Score":3,"Tags":"python,mysql,django,overhead","A_Id":1689143,"CreationDate":"2009-11-06T17:18:00.000","Title":"Overhead of a Round-trip to MySql?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"So I've been building django applications for a while now, and drinking the cool-aid and all: only using the ORM and never writing custom SQL.\nThe main page of the site (the primary interface where users will spend 80% - 90% of their time) was getting slow once you have a large amount of user specific content (ie photos, friends, other data, etc)\nSo I popped in the sql logger (was pre-installed with pinax, I just enabled it in the settings) and imagine my surprise when it reported over 500 database queries!! With hand coded sql I hardly ever ran more than 50 on the most complex pages.\nIn hindsight it's not all together surprising, but it seems that this can't be good.\n...even if only a dozen or so of the queries take 1ms+\nSo I'm wondering, how much overhead is there on a round trip to mysql? django and mysql are running on the same server so there shouldn't be any networking related overhead.","AnswerCount":4,"Available Count":4,"Score":0.1488850336,"is_accepted":false,"ViewCount":1620,"Q_Id":1689031,"Users Score":3,"Answer":"The overhead of each queries is only part of the picture. The actual round trip time between your Django and Mysql servers is probably very small since most of your queries are coming back in less than a one millisecond.  The bigger problem is that the number of queries issued to your database can quickly overwhelm it. 500 queries for a page is way to much, even 50 seems like a lot to me.  If ten users view complicated pages you're now up to 5000 queries.\nThe round trip time to the database server is more of a factor when the caller is accessing the database from a Wide Area Network, where roundtrips can easily be between 20ms and 100ms.\nI would definitely look into using some kind of caching.","Q_Score":3,"Tags":"python,mysql,django,overhead","A_Id":1689146,"CreationDate":"2009-11-06T17:18:00.000","Title":"Overhead of a Round-trip to MySql?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"So I've been building django applications for a while now, and drinking the cool-aid and all: only using the ORM and never writing custom SQL.\nThe main page of the site (the primary interface where users will spend 80% - 90% of their time) was getting slow once you have a large amount of user specific content (ie photos, friends, other data, etc)\nSo I popped in the sql logger (was pre-installed with pinax, I just enabled it in the settings) and imagine my surprise when it reported over 500 database queries!! With hand coded sql I hardly ever ran more than 50 on the most complex pages.\nIn hindsight it's not all together surprising, but it seems that this can't be good.\n...even if only a dozen or so of the queries take 1ms+\nSo I'm wondering, how much overhead is there on a round trip to mysql? django and mysql are running on the same server so there shouldn't be any networking related overhead.","AnswerCount":4,"Available Count":4,"Score":0.1973753202,"is_accepted":false,"ViewCount":1620,"Q_Id":1689031,"Users Score":4,"Answer":"Just because you are using an ORM doesn't mean that you shouldn't do performance tuning. \nI had - like you - a home page of one of my applications that had low performance. I saw that I was doing hundreds of queries to display that page. I went looking at my code and realized that with some careful use of select_related() my queries would bring more of the data I needed - I went from hundreds of queries to tens.\nYou can also run a SQL profiler and see if there aren't indices that would help your most common queries - you know, standard database stuff.\nCaching is also your friend, I would think. If a lot of a page is not changing, do you need to query the database every single time?\nIf all else fails, remember: the ORM is great, and yes - you should try to use it because it is the Django philosophy; but you are not married to it.\nIf you really have a usecase where studying and tuning the ORM navigation didn't help, if you are sure that you could do it much better with a standard query: use raw sql for that case.","Q_Score":3,"Tags":"python,mysql,django,overhead","A_Id":1689452,"CreationDate":"2009-11-06T17:18:00.000","Title":"Overhead of a Round-trip to MySql?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"So I've been building django applications for a while now, and drinking the cool-aid and all: only using the ORM and never writing custom SQL.\nThe main page of the site (the primary interface where users will spend 80% - 90% of their time) was getting slow once you have a large amount of user specific content (ie photos, friends, other data, etc)\nSo I popped in the sql logger (was pre-installed with pinax, I just enabled it in the settings) and imagine my surprise when it reported over 500 database queries!! With hand coded sql I hardly ever ran more than 50 on the most complex pages.\nIn hindsight it's not all together surprising, but it seems that this can't be good.\n...even if only a dozen or so of the queries take 1ms+\nSo I'm wondering, how much overhead is there on a round trip to mysql? django and mysql are running on the same server so there shouldn't be any networking related overhead.","AnswerCount":4,"Available Count":4,"Score":1.2,"is_accepted":true,"ViewCount":1620,"Q_Id":1689031,"Users Score":2,"Answer":"There are some ways to reduce the query volume.\n\nUse .filter() and .all() to get a bunch of things; pick and choose in the view function (or template via {%if%}).  Python can process a batch of rows faster than MySQL.  \n\"But I could send too much to the template\".   True, but you'll execute fewer SQL requests.  Measure to see which is better.\nThis is what you used to do when you wrote SQL.  It's not wrong -- it doesn't break the ORM -- but it optimizes the underlying DB work and puts the processing into the view function and the template.\nAvoid query navigation in the template.  When you do {{foo.bar.baz.quux}}, SQL is used to get the bar associated with foo, then the baz associated with the bar, then the quux associated with baz.  You may be able to reduce this query business with some careful .filter() and Python processing to assemble a useful tuple in the view function.\nAgain, this was something you used to do when you hand-crafted SQL.  In this case, you gather larger batches of ORM-managed objects in the view function and do your filtering in Python instead of via a lot of individual ORM requests. \nThis doesn't break the ORM.  It changes the usage profile from lots of little queries to a few bigger queries.","Q_Score":3,"Tags":"python,mysql,django,overhead","A_Id":1689330,"CreationDate":"2009-11-06T17:18:00.000","Title":"Overhead of a Round-trip to MySql?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm developing an application that will store a sizeable number of records. These records will be something like (URL, date, title, source, {optional data...})\nAs this is a client-side app, I don't want to use a database server, I just want the info stored into files.\nI want the files to be readable from various languages (at least python and C++), so something language specific like python's pickle is out of the game.\nI am seeing two possibilities: sqlite and BerkeleyDB. As my use case is clearly not relational, I am tempted to go with BerkeleyDB, however I don't really know how I should use it to store my records, as it only stores key\/value pairs.\nIs my reasoning correct? If so, how should I use BDB to store my records? Can you link me to relevant info? Or am I missing a better solution?","AnswerCount":6,"Available Count":3,"Score":0.0665680765,"is_accepted":false,"ViewCount":666,"Q_Id":1697153,"Users Score":2,"Answer":"BerkeleyDB is good, also look at the *DBM incarnations (e.g. GDBM).  The big question though is:  for what do you need to search?  Do you need to search by that URL, by a range of URLs or the dates you list?  \nIt is also quite possible to keep groups of records as simple files in the local filesystem, grouped by dates or search terms, &c.\nAnswering the \"search\" question is the biggest start.\nAs for the key\/value thingy, what you need to ensure is that the KEY itself is well defined as for your lookups.  If for example you need to lookup by dates sometimes and others by title, you will need to maintain a \"record\" row, and then possibly 2 or more \"index\" rows making reference to the original record.  You can model nearly anything in a key\/value store.","Q_Score":5,"Tags":"c++,python,database,persistence","A_Id":1697185,"CreationDate":"2009-11-08T17:01:00.000","Title":"Which database should I use to store records, and how should I use it?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm developing an application that will store a sizeable number of records. These records will be something like (URL, date, title, source, {optional data...})\nAs this is a client-side app, I don't want to use a database server, I just want the info stored into files.\nI want the files to be readable from various languages (at least python and C++), so something language specific like python's pickle is out of the game.\nI am seeing two possibilities: sqlite and BerkeleyDB. As my use case is clearly not relational, I am tempted to go with BerkeleyDB, however I don't really know how I should use it to store my records, as it only stores key\/value pairs.\nIs my reasoning correct? If so, how should I use BDB to store my records? Can you link me to relevant info? Or am I missing a better solution?","AnswerCount":6,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":666,"Q_Id":1697153,"Users Score":0,"Answer":"Ok, so you say just storing the data..? You really only need a DB for retrieval, lookup, summarising, etc. So, for storing, just use simple text files and append lines. Compress the data if you need to, use delims between fields - just about any language will be able to read such files. If you do want to retrieve, then focus on your retrieval needs, by date, by key, which keys, etc. If you want simple client side, then you need simple client db. SQLite is far easier than BDB, but look at things like Sybase Advantage (very fast and free for local clients but not open-source) or VistaDB or firebird... but all will require local config\/setup\/maintenance. If you go local XML for a 'sizable' number of records will give you some unnecessarily bloated file-sizes..!","Q_Score":5,"Tags":"c++,python,database,persistence","A_Id":1698109,"CreationDate":"2009-11-08T17:01:00.000","Title":"Which database should I use to store records, and how should I use it?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm developing an application that will store a sizeable number of records. These records will be something like (URL, date, title, source, {optional data...})\nAs this is a client-side app, I don't want to use a database server, I just want the info stored into files.\nI want the files to be readable from various languages (at least python and C++), so something language specific like python's pickle is out of the game.\nI am seeing two possibilities: sqlite and BerkeleyDB. As my use case is clearly not relational, I am tempted to go with BerkeleyDB, however I don't really know how I should use it to store my records, as it only stores key\/value pairs.\nIs my reasoning correct? If so, how should I use BDB to store my records? Can you link me to relevant info? Or am I missing a better solution?","AnswerCount":6,"Available Count":3,"Score":0.0665680765,"is_accepted":false,"ViewCount":666,"Q_Id":1697153,"Users Score":2,"Answer":"Personally I would use sqlite anyway.  It has always just worked for me (and for others I work with).  When your app grows and you suddenly do want to do something a little more sophisticated, you won't have to rewrite.\nOn the other hand, I've seen various comments on the Python dev list about Berkely DB that suggest it's less than wonderful; you only get dict-style access (what if you want to select certain date ranges or titles instead of URLs); and it's not even in Python 3's standard set of libraries.","Q_Score":5,"Tags":"c++,python,database,persistence","A_Id":1697239,"CreationDate":"2009-11-08T17:01:00.000","Title":"Which database should I use to store records, and how should I use it?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Are there database testing tools for python (like sqlunit)? I want to test the DAL that is built using sqlalchemy","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":601,"Q_Id":1719279,"Users Score":4,"Answer":"Follow the design pattern that Django uses.\n\nCreate a disposable copy of the database.  Use SQLite3 in-memory, for example.\nCreate the database using the SQLAlchemy table and index definitions.  This should be a fairly trivial exercise.\nLoad the test data fixture into the database.  \nRun your unit test case in a database with a known, defined state.\nDispose of the database.\n\nIf you use SQLite3 in-memory, this procedure can be reasonably fast.","Q_Score":4,"Tags":"python,database,testing,sqlalchemy","A_Id":1719347,"CreationDate":"2009-11-12T01:27:00.000","Title":"Are there database testing tools for python (like sqlunit)?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"But, they were unable to be found!?\nHow do I install both of them?","AnswerCount":3,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":730,"Q_Id":1720867,"Users Score":2,"Answer":"Have you installed python-mysqldb? If not install it using apt-get install python-mysqldb. And how are you importing mysql.Is it import MySQLdb? Python is case sensitive.","Q_Score":1,"Tags":"python,linux,unix,installation","A_Id":1720904,"CreationDate":"2009-11-12T09:01:00.000","Title":"I just installed a Ubuntu Hardy server. In Python, I tried to import _mysql and MySQLdb","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm writing an application in Python with Postgresql 8.3 which runs on several machines on a local network.\nAll machines\n1) fetch huge amount of data from the database server ( lets say database gets 100 different queries from a machine with in 2 seconds time) and there are about 10 or 11 machines doing that.\n2) After processing data machines have to update certain tables (about 3 or 4 update\/insert queries per machine per 1.5 seconds).\nWhat I have noticed is that database goes down some times by giving server aborted process abnormally or freezes the server machine (requiring a hard reset). \nBy the way all machines maintain a constant connection to the database at all times i.e. once a connection is made using Psycopg2 (in Python) it remains active until processing finishes (which could last hours).\nWhat's the best \/ optimal way for handling large number of connections in the application, should they be destroyed after each query ?\nSecondly should I increase max_connections ?\nWould greatly appreciate any advice on this matter.","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":1607,"Q_Id":1728350,"Users Score":1,"Answer":"This sounds a bit like your DB server might have some problems, especially if your database server literally crashes. I'd start by trying to figure out from logs what is the root cause of the problems. It could be something like running out of memory, but it could also happen because of faulty hardware.\nIf you're opening all the connections at start and keep them open, max_connections isn't the culprit. The way you're handling the DB connections should be just fine and your server shouldn't do that no matter how it's configured.","Q_Score":2,"Tags":"python,linux,performance,postgresql,out-of-memory","A_Id":1729623,"CreationDate":"2009-11-13T10:18:00.000","Title":"Optimal \/ best pratice to maintain continuos connection between Python and Postgresql using Psycopg2","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"i recently switched to mac. first and foremost i installed xampp.\nthen for django-python-mysql connectivity, i \"somehow\" ended up installing a seperate MySQL.\nnow the seperate mysql installation is active all the time and the Xampp one doesnt switch on unless i kill the other one.\nwhat i wanted to know is it possible to make xampp work with the seperate mysql installation? because that way i wouldnt have to tinker around with the mysqlDB adapter for python?\nany help would be appreciated.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":150,"Q_Id":1734918,"Users Score":1,"Answer":"You could change the listening port of one of the installations and they shouldn't conflict anymore with each other.\nUpdate: You need to find the mysql configuration file my.cnf of the server which should get a new port (the one from xampp should be somewhere in the xampp folder). Find the line port=3306 in the [mysqld] section. You could change it to something like 3307.\nYou will also need to specify the new port when connecting to the server from your applications.","Q_Score":0,"Tags":"python,mysql,django,macos,xampp","A_Id":1734939,"CreationDate":"2009-11-14T17:22:00.000","Title":"2 mysql instances in MAC","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"How do I load data from an Excel sheet into my Django application? I'm using database PosgreSQL as the database.\nI want to do this programmatically. A client wants to load two different lists onto the website weekly and they don't want to do it in the admin section, they just want the lists loaded from an Excel sheet. Please help because I'm kind of new here.","AnswerCount":9,"Available Count":1,"Score":-0.022218565,"is_accepted":false,"ViewCount":7027,"Q_Id":1747501,"Users Score":-1,"Answer":"Just started using XLRD and it looks very easy and simple to use.\nBeware that it does not support Excel 2007 yet, so keep in mind to save your excel at 2003 format.","Q_Score":3,"Tags":"python,django,excel,postgresql","A_Id":11293612,"CreationDate":"2009-11-17T09:07:00.000","Title":"Getting data from an Excel sheet","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Greetings, everybody.\nI'm trying to import the following libraries in python: cx_Oracle and kinterbasdb.\nBut, when I try, I get a very similar message error.\n*for cx_Oracle:\nTraceback (most recent call last):\n  File \"\", line 1, in \nImportError: DLL load failed: N\u00e3o foi poss\u00edvel encontrar o procedimento especificado.\n(translation: It was not possible to find the specified procedure)\n*for kinterbasdb:\nTraceback (most recent call last):\n  File \"C:\\\", line 1, in \n  File \"c:\\Python26\\Lib\\site-packages\\kinterbasdb__init__.py\", line 119, in \n    import _kinterbasdb as _k\nImportError: DLL load failed: N\u00e3o foi poss\u00edvel encontrar o m\u00f3dulo especificado.\n(translation: It was not possible to find the specified procedure)\nI'm using python 2.6.4 in windows XP. cx_Oracle's version is 5.0.2. kinterbasdb's version is 3.3.0.\nEdit: I've solved it for cx_Oracle, it was a wrong version problem. But I believe I'm using the correct version, and I downloaded it from the Firebird site ( kinterbasdb-3.3.0.win32-setup-py2.6.exe ). Still need assistance with this, please.\nCan anyone lend me a hand here?\nMany Thanks\nDante","AnswerCount":1,"Available Count":1,"Score":-0.1973753202,"is_accepted":false,"ViewCount":767,"Q_Id":1799475,"Users Score":-1,"Answer":"oracle is a complete pain.  i don't know the details for windows, but for unix you need ORACLE_HOME and LD_LIBRARY_PATH to both be defined before cx_oracle will work.  in windows this would be your environment variables, i guess.  so check those.\nalso, check that they are defined in the environment in which the program runs (again, i don't know windows specific details, but in unix it's possible for everything to work when you run it from your account by hand, but still not work when run as a batch job because the environment is different).","Q_Score":2,"Tags":"python,cx-oracle,kinterbasdb","A_Id":1803407,"CreationDate":"2009-11-25T19:43:00.000","Title":"importing cx_Oracle and kinterbasdb returns error","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":1,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm creating a financial app and it seems my floats in sqlite are floating around.  Sometimes a 4.0 will be a 4.000009, and a 6.0 will be a 6.00006, things like that.  How can I make these more exact and not affect my financial calculations?\nValues are coming from Python if that matters. Not sure which area the messed up numbers are coming from.","AnswerCount":6,"Available Count":1,"Score":0.0333209931,"is_accepted":false,"ViewCount":3672,"Q_Id":1801307,"Users Score":1,"Answer":"Most people would probably use Decimal for this, however if this doesn't map onto a database type you may take a performance hit.\nIf performance is important you might want to consider using Integers to represent an appropriate currency unit - often cents or tenths of cents is ok.\nThere should be business rules about how amounts are to be rounded in various situations and you should have tests covering each scenario.","Q_Score":4,"Tags":"python,sqlite,floating-point","A_Id":1801521,"CreationDate":"2009-11-26T02:55:00.000","Title":"How to deal with rounding errors of floating types for financial calculations in Python SQLite?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have downloaded mysqlDb, and while installing it I am getting errors like:\n\nC:\\Documents and Settings\\naresh\\Desktop\\MySQL-python-1.2.3c1>setup.py build\nTraceback (most recent call last):\nFile \"C:\\Documents and Settings\\naresh\\Desktop\\MySQL-python-1.2.3c1 \n\\setup.py\",line15,      in  \nmetadata, options = get_config()\nFile \"C:\\Documents and Settings\\naresh\\Desktop\\MySQL-python-1.2.3c1\n\\setup_windows.py\",    line 7, in get_config\nserverKey = _winreg.OpenKey(_winreg.HKEY_LOCAL_MACHINE, options['registry_key'])\nWindowsError: [Error 2] The system cannot find the file specified\n\nWhat can I do to address this?","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":6706,"Q_Id":1803233,"Users Score":0,"Answer":"You need to fire up regedit and make \nHKEY_LOCAL_MACHINE\\SOFTWARE\\Wow6432Node\\Python\\PythonCore\\2.7\\InstallPath\nand HKEY_LOCAL_MACHINE\\SOFTWARE\\Wow6432Node\\Python\\PythonCore\\2.7\\InstallPath\\InstallGroup\nto look like HKEY_LOCAL_MACHINE\\SOFTWARE\\Python\\PythonCore\\2.7\\InstallPath\\InstallGroup.","Q_Score":7,"Tags":"python,mysql","A_Id":6616901,"CreationDate":"2009-11-26T11:46:00.000","Title":"How to install mysql connector","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"We have an existing  C# project based on NHibernate and WPF. I am asked to convert it to Linux and to consider other implementation like Python. But for some reason, they like NHibernate a lot and want to keep it.\nDo you know if it's possible to keep the NHibernate stuff and make it work with Python ? I am under the impression that NHibernate is glue code between C# and the DB, so can not be exported to other languages.\nAlternative question: can somebody recommend a good python compatible replacement of NHibernate ? The backend DB is Oracle something.","AnswerCount":4,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":1382,"Q_Id":1809201,"Users Score":0,"Answer":"Check out Django. They have a nice ORM and I believe it has tools to attempt a reverse-engineer from the DB schema.","Q_Score":0,"Tags":"python,nhibernate,orm","A_Id":1809219,"CreationDate":"2009-11-27T14:50:00.000","Title":"NHibernate and python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"We have an existing  C# project based on NHibernate and WPF. I am asked to convert it to Linux and to consider other implementation like Python. But for some reason, they like NHibernate a lot and want to keep it.\nDo you know if it's possible to keep the NHibernate stuff and make it work with Python ? I am under the impression that NHibernate is glue code between C# and the DB, so can not be exported to other languages.\nAlternative question: can somebody recommend a good python compatible replacement of NHibernate ? The backend DB is Oracle something.","AnswerCount":4,"Available Count":3,"Score":0.0996679946,"is_accepted":false,"ViewCount":1382,"Q_Id":1809201,"Users Score":2,"Answer":"What about running your project under Mono on Linux? Mono seems to support NHibernate, which means you may be able to get away with out rewriting large chunks of your application.\nAlso, if you really wanted to get Python in on the action, you could use IronPython along with Mono.","Q_Score":0,"Tags":"python,nhibernate,orm","A_Id":1809238,"CreationDate":"2009-11-27T14:50:00.000","Title":"NHibernate and python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"We have an existing  C# project based on NHibernate and WPF. I am asked to convert it to Linux and to consider other implementation like Python. But for some reason, they like NHibernate a lot and want to keep it.\nDo you know if it's possible to keep the NHibernate stuff and make it work with Python ? I am under the impression that NHibernate is glue code between C# and the DB, so can not be exported to other languages.\nAlternative question: can somebody recommend a good python compatible replacement of NHibernate ? The backend DB is Oracle something.","AnswerCount":4,"Available Count":3,"Score":0.2449186624,"is_accepted":false,"ViewCount":1382,"Q_Id":1809201,"Users Score":5,"Answer":"NHibernate is not specific to C#, but it is specific to .NET.\nIronPython is a .NET language from which you could use NHibernate.\n.NET and NHibernate can run on Linux through Mono.  I'm not sure how good Mono's support is for WPF.\nI'm not sure if IronPython runs on Linux, but that would seem to be the closest thing to what you are looking for.\nThere is a Java version of NHibernate (said tongue in cheek) called Hibernate and there are integration points between Java and Python where Linux is very much supported.\nI know the Python community has its own ORMs, but as far as I'm aware, those options are not as mature and feature rich as Hibernate\/NHibernate.\nI would imagine that almost all of the options available to you would support Oracle.","Q_Score":0,"Tags":"python,nhibernate,orm","A_Id":1809266,"CreationDate":"2009-11-27T14:50:00.000","Title":"NHibernate and python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I recently created a script that parses several web proxy logs into a tidy sqlite3 db file that is working great for me... with one snag.  the file size.  I have been pressed to use this format (a sqlite3 db) and python handles it natively like a champ, so my question is this...  what is the best form of string compression that I can use for db entries when file size is the sole concern.  zlib? base-n? Klingon?\nAny advice would help me loads, again just string compression for characters that are compliant for URLs.","AnswerCount":3,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":2957,"Q_Id":1829256,"Users Score":0,"Answer":"what sort of parsing do you do before you put it in the database?  I get the impression that it is fairly simple with a single table holding each entry - if not then my apologies. \nCompression is all about removing duplication, and in a log file most of the duplication is between entries rather than within each entry so compressing each entry individually is not going to be a huge win.\nThis is off the top of my head so feel free to shoot it down in flames, but I would consider breaking the table into a set of smaller tables holding the individual parts of the entry.  A log entry would then mostly consist of a timestamp (as DATE type rather than a string) plus a set of indexes into other tables (e.g. requesting IP, request type, requested URL, browser type etc.)\nThis would have a trade-off of course, since it would make the database a lot more complex to maintain, but on the other hand it would enable meaningful queries such as \"show me all the unique IPs that requested page X in the last week\".","Q_Score":0,"Tags":"python,sqlite,compression","A_Id":1829601,"CreationDate":"2009-12-01T22:02:00.000","Title":"Python 3: Best string compression method to minimize the size of a sqlite3 db","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I recently created a script that parses several web proxy logs into a tidy sqlite3 db file that is working great for me... with one snag.  the file size.  I have been pressed to use this format (a sqlite3 db) and python handles it natively like a champ, so my question is this...  what is the best form of string compression that I can use for db entries when file size is the sole concern.  zlib? base-n? Klingon?\nAny advice would help me loads, again just string compression for characters that are compliant for URLs.","AnswerCount":3,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":2957,"Q_Id":1829256,"Users Score":0,"Answer":"Instead of inserting compression\/decompression code into your program, you could store the table itself on a compressed drive.","Q_Score":0,"Tags":"python,sqlite,compression","A_Id":1832688,"CreationDate":"2009-12-01T22:02:00.000","Title":"Python 3: Best string compression method to minimize the size of a sqlite3 db","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm using the sqlite3 module in Python 2.6.4 to store a datetime in a SQLite database. Inserting it is very easy, because sqlite automatically converts the date to a string. The problem is, when reading it it comes back as a string, but I need to reconstruct the original datetime object. How do I do this?","AnswerCount":3,"Available Count":1,"Score":0.0665680765,"is_accepted":false,"ViewCount":58748,"Q_Id":1829872,"Users Score":1,"Answer":"Note: In Python3, I had to change the SQL to something like:\nSELECT jobid, startedTime as \"st [timestamp]\" FROM job\n(I had to explicitly name the column.)","Q_Score":84,"Tags":"python,datetime,sqlite","A_Id":48429766,"CreationDate":"2009-12-02T00:15:00.000","Title":"How to read datetime back from sqlite as a datetime instead of string in Python?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I want to use Python-MySQLDB library on Mac so I have compiled the source code to get the _mysql.so under Mac10.5 with my Intel iMac (i386)\nThis _mysql.co works in 2 of my iMacs and another Macbook. But that's it, it doesn't work in any other Macs.\nDoes this mean some machine specific info got compiled into the file?","AnswerCount":2,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":106,"Q_Id":1831979,"Users Score":2,"Answer":"If you've only built one architecture (i386 \/ PPC) then it won't work on Macs with the opposite architecture. Are the machines that don't work PPC machines, by any chance?\nSometimes build configurations are set up to build only the current architecture by default - I haven't build Python-MySQLDB so I'm not sure if this is the case here, but it's worth checking.\nYou can find out which architectures have been built with the 'file' command in Terminal.\n(Incidentally do you mean \".so\"? I'm not familiar with \".co\" files.)","Q_Score":0,"Tags":"python,compilation,mysql","A_Id":1832065,"CreationDate":"2009-12-02T10:21:00.000","Title":"Why _mysql.co that compiled on one Mac doesn't work on another?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Does there exist, or is there an intention to create, a universal database frontend for Python like Perl's DBI? I am aware of Python's DB-API, but all the separate packages are leaving me somewhat aggravated.","AnswerCount":2,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":1158,"Q_Id":1836061,"Users Score":2,"Answer":"Well...DBAPI is that frontend:\n\nThis API has been defined to encourage similarity between the\n  Python modules that are used to access databases.  By doing this,\n  we hope to achieve a consistency leading to more easily understood\n  modules, code that is generally more portable across databases,\n  and a broader reach of database connectivity from Python.\n\nIt has always worked great for me atleast, care to elaborate the problems you are facing?","Q_Score":1,"Tags":"python,database","A_Id":1836125,"CreationDate":"2009-12-02T21:49:00.000","Title":"Python universal database interface?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have an Excel spreadsheet with calculations I would like to use in a Django web application. I do not need to present the spreadsheet as it appears in Excel. I only want to use the formulae embedded in it. What is the best way to do this?","AnswerCount":4,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1592,"Q_Id":1883098,"Users Score":0,"Answer":"You need to use Excel to calculate the results? I mean, maybe you could run the Excel sheet from OpenOffice and use a pyUNO macro, which is somehow \"native\" python. \nA different approach will be to create a macro to generate some more friendly code to python, if you want Excel to perform the calculation is easy you end up with a very slow process.","Q_Score":2,"Tags":"python,django,excel","A_Id":1937261,"CreationDate":"2009-12-10T18:39:00.000","Title":"Importing Excel sheets, including formulae, into Django","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"PHP provides mysql_connect() and mysql_pconnect() which allow creating both temporary and persistent database connections.\nIs there a similar functionality in Python? The environment on which this will be used is lighttpd server with FastCGI.\nThank you!","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":3649,"Q_Id":1895089,"Users Score":0,"Answer":"Note: Persistent connections can have a very negative effect on your system performance. If you have a large number of web server processes all holding persistent connections to your DB server you may exhaust the DB server's limit on connections. This is one of those areas where you need to test it under heavy simulated loads to make sure you won't hit the wall at 100MPH.","Q_Score":2,"Tags":"python,mysql,web-services","A_Id":1895731,"CreationDate":"2009-12-12T23:49:00.000","Title":"Persistent MySQL connections in Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am using MySQLdb module of python on FC11 machine. Here, i have an issue. I have the following implementation for one of our requirement:\n\nconnect to mysqldb and get DB handle,open a cursor, execute a delete statement,commit and then close the cursor.\nAgain using the DB handle above, iam performing a \"select\" statement one some different table using the cursor way as described above.\n\nI was able to delete few records using Step1, but step2 select is not working. It simply gives no records for step2 though there are some records available under DB.\nBut, when i comment step1 and execute step2, i could see that step2 works fine. Why this is so?\nThough there are records, why the above sequence is failing to do so?\nAny ideas would be appreciated.\nThanks!","AnswerCount":3,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":626,"Q_Id":1922623,"Users Score":0,"Answer":"With no code, I can only make a guess:  try not closing the cursor until you are done with that connection.  I think that calling cursor() again after calling cursor.close() will just give you a reference to the same cursor, which can no longer be used for queries.\nI am not 100% sure if that is the intended behavior, but I haven't seen any MySQLDB examples of cursors being opened and closed within the same connection.","Q_Score":0,"Tags":"python,mysql","A_Id":1922710,"CreationDate":"2009-12-17T15:42:00.000","Title":"MYSQLDB python module","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am using MySQLdb module of python on FC11 machine. Here, i have an issue. I have the following implementation for one of our requirement:\n\nconnect to mysqldb and get DB handle,open a cursor, execute a delete statement,commit and then close the cursor.\nAgain using the DB handle above, iam performing a \"select\" statement one some different table using the cursor way as described above.\n\nI was able to delete few records using Step1, but step2 select is not working. It simply gives no records for step2 though there are some records available under DB.\nBut, when i comment step1 and execute step2, i could see that step2 works fine. Why this is so?\nThough there are records, why the above sequence is failing to do so?\nAny ideas would be appreciated.\nThanks!","AnswerCount":3,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":626,"Q_Id":1922623,"Users Score":0,"Answer":"It sounds as though the first cursor is being returned back to the second step.","Q_Score":0,"Tags":"python,mysql","A_Id":1924766,"CreationDate":"2009-12-17T15:42:00.000","Title":"MYSQLDB python module","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have both, django and mysql set to work with UTF-8.\nMy base.html set utf-8 in head.\nrow on my db :\n\n\n+----+--------+------------------------------------------------------------------+-----------------------------+-----------------------------+---------------------+\n| id | psn_id | name                                                             | publisher                   | developer                   | release_date        |\n+----+--------+------------------------------------------------------------------+-----------------------------+-----------------------------+---------------------+\n|  1 | 10945- | \u307e\u3044\u306b\u3061\u3044\u3063\u3057\u3087 | Sony Computer Entertainment | Sony Computer Entertainment | 2006-11-11 00:00:00 |\n+----+--------+------------------------------------------------------------------+-----------------------------+-----------------------------+---------------------+\n\n\nthe source code generated looks like :\n\n&#12414;&#12356;&#12395;&#12385;&#12356;&#12387;&#12375;&#12423;\n\nand this is wat is displayed :\/\nwhy they are not showing the chars the way in this database?","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":312,"Q_Id":1928087,"Users Score":0,"Answer":"As Dominic has said, the generated HTML source code is correct (these are your Japanese characters translated into HTML entities), but we're not sure, if you see the same code rendered in the page (in this case, you have probably set content-type to \"text\/plain\" instead of \"text\/html\" - do you use render_to_response() or HttpResponse() in the corresponding view.py method?), or your Japanese is rendered correctly but you just don't like the entities in the source code.\nSince we don't know your Django settings and how do you render and return the page, it's difficult to provide you the solution.","Q_Score":0,"Tags":"python,django,unicode","A_Id":1931067,"CreationDate":"2009-12-18T13:04:00.000","Title":"django + mysql + UTF-8 - Chars are not displayed","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'd like to get busy with a winter programming project and am contemplating writing an online word game (with a server load of up to, say, 500 users simultaneously). I would prefer it to be platform independent. I intend to use Python, which I have some experience with. For user data storage, after previous experience with MySQL, a flat database design would be preferable but not essential. Okay, now the questions:\nIs it worth starting with Python 3, or is it still too poorly supported with ports of modules from previous versions?\nAre there any great advantages in using Python 3 for my particular project? Would I be better off looking at using other languages instead, such as Erlang?\nIs there any great advantage in using a relational database within a game server?\nAre there any open source game servers' source code out there that are worthy of study before starting?","AnswerCount":5,"Available Count":2,"Score":0.0798297691,"is_accepted":false,"ViewCount":1430,"Q_Id":1937286,"Users Score":2,"Answer":"Is it worth starting with Python 3, or is it still too poorly supported with ports of modules from previous versions?\n\ndepends on which modules do you want to use. twisted is a \"swiss knife\" for the network programming and could be a choice for your project but unfortunately it does not support python3 yet.\n\nAre there any great advantages in using Python 3 for my particular project? Would I be better off looking at using other languages instead, such as Erlang?\n\nonly you can answer your question because only you know your knowledge. Using python3 instead of python2 you get all the advantages of new features the python3 brings with him and the disadvantage that non all libraries support python3 at the moment.\nnote that python2.6 should implements most (if not all) of the features of python3 while it should be compatible with python2.5 but i did not investigated a lot in this way.\nboth python and erlang are candidates for your needs, use what you know best and what you like most.\n\nIs there any great advantage in using a relational database within a game server?\n\nyou get all the advantages and disadvantage of having a ACID storage system.","Q_Score":2,"Tags":"python","A_Id":1937342,"CreationDate":"2009-12-20T22:18:00.000","Title":"Word game server in Python, design pros and cons?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'd like to get busy with a winter programming project and am contemplating writing an online word game (with a server load of up to, say, 500 users simultaneously). I would prefer it to be platform independent. I intend to use Python, which I have some experience with. For user data storage, after previous experience with MySQL, a flat database design would be preferable but not essential. Okay, now the questions:\nIs it worth starting with Python 3, or is it still too poorly supported with ports of modules from previous versions?\nAre there any great advantages in using Python 3 for my particular project? Would I be better off looking at using other languages instead, such as Erlang?\nIs there any great advantage in using a relational database within a game server?\nAre there any open source game servers' source code out there that are worthy of study before starting?","AnswerCount":5,"Available Count":2,"Score":0.0399786803,"is_accepted":false,"ViewCount":1430,"Q_Id":1937286,"Users Score":1,"Answer":"Related to your database choice, I'd seriously look at using Postgres instead of MySQL.  In my experiance with the two Postgres has shown to be faster on most write operations while MySQL is slightly faster on the reads.  \nHowever, MySQL also has many issues some of which are:\n\nLive backups are difficult at best, and impossible at worse, mostly you have to take the db offline or let it lock during the backups.\nIn the event of having to kill the server forcefully, either by kill -9, or due to power outage, postgres generally has better resilience to table corruption. \nFull support for ACID compliance, and other relational db features that support for, again imho and experiance, are weak or lacking in MySQL.\n\nYou can use a library such as SQLAlchemy to abstract away the db access though.  This would let you test against both to see which you prefer dealing with.\nAs far as the language choice.  \nIf you go with Python:\n\nMore librarys support Python 2.x rather than Python 3.x at this time, so I'd likely stick to 2.x.  \nBeware multi-threading gotchas with Python's GIL.  Utilizing Twisted can get around this. \n\nIf you go with Erlang:\n\nErlang's syntax and idioms can be very foreign to someone who's never used it.\nIf well written it not only scales, it SCALES.  \nErlang has it's own highly concurrent web server named Yaws.\nErlang also has it's own highly scalable DBMS named Mnesia (Note it's not relational).\n\nSo I guess your choices could be really boiled down to how much you're willing to learn to do this project.","Q_Score":2,"Tags":"python","A_Id":1937370,"CreationDate":"2009-12-20T22:18:00.000","Title":"Word game server in Python, design pros and cons?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I worked on a PHP project earlier where prepared statements made the SELECT queries 20% faster.\nI'm wondering if it works on Python? I can't seem to find anything that specifically says it does or does NOT.","AnswerCount":7,"Available Count":1,"Score":0.1418931938,"is_accepted":false,"ViewCount":52874,"Q_Id":1947750,"Users Score":5,"Answer":"Using the SQL Interface as suggested by Amit can work if you're only concerned about performance.  However, you then lose the protection against SQL injection that a native Python support for prepared statements could bring.  Python 3 has modules that provide prepared statement support for PostgreSQL.  For MySQL, \"oursql\" seems to provide true prepared statement support (not faked as in the other modules).","Q_Score":51,"Tags":"python,mysql,prepared-statement","A_Id":2539467,"CreationDate":"2009-12-22T17:06:00.000","Title":"Does Python support MySQL prepared statements?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am using Python 2.6 + xlwt module to generate excel files.\nIs it possible to include an autofilter in the first row with xlwt or pyExcelerator or anything else besides COM? \nThanks","AnswerCount":3,"Available Count":1,"Score":0.1325487884,"is_accepted":false,"ViewCount":6820,"Q_Id":1948224,"Users Score":2,"Answer":"I have the same issue, running a linux server.\ni'm going to check creating an ODS or XLSX file with auto-filter by other means, and then convert them with a libreoffice command line to \"xls\".","Q_Score":6,"Tags":"python,excel,xlwt,pyexcelerator","A_Id":20838509,"CreationDate":"2009-12-22T18:21:00.000","Title":"How to create an excel file with an autofilter in the first row with xlwt?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I need a documentation system for a PHP project and I wanted it to be able to integrate external documentation (use cases, project scope etc.) with the documentation generated from code comments. It seems that phpDocumentor has exactly the right feature set, but external documentation must be written in DocBook which is too complex for our team.\nIf it were in python, sphinx would be just about perfect for this job (ReST is definitely simpler than docbook). Is there any way I can integrate external ReST documentation with the docs extracted from phpdoc? Should I just separate the external documentation (eg. use ReST for external and phpdoc for internal)? Or do you have a better suggestion for managing the external documentation?","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":853,"Q_Id":1957787,"Users Score":2,"Answer":"You can convert ReST to DocBook using pandoc.","Q_Score":0,"Tags":"php,phpdoc,docbook,restructuredtext,python-sphinx","A_Id":2035342,"CreationDate":"2009-12-24T10:37:00.000","Title":"External documentation for PHP, no DocBook","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"If I want to be able to test my application against a empty MySQL database each time my application's testsuite is run, how can I start up a server as a non-root user which refers to a empty (not saved anywhere, or in saved to \/tmp) MySQL database?\nMy application is in Python, and I'm using unittest on Ubuntu 9.10.","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":287,"Q_Id":1960155,"Users Score":0,"Answer":"You can try the Blackhole and Memory table types in MySQL.","Q_Score":2,"Tags":"python,mysql,unit-testing,ubuntu","A_Id":1960164,"CreationDate":"2009-12-25T00:25:00.000","Title":"Start a \"throwaway\" MySQL session for testing code?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"If I want to be able to test my application against a empty MySQL database each time my application's testsuite is run, how can I start up a server as a non-root user which refers to a empty (not saved anywhere, or in saved to \/tmp) MySQL database?\nMy application is in Python, and I'm using unittest on Ubuntu 9.10.","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":287,"Q_Id":1960155,"Users Score":1,"Answer":"--datadir for just the data or --basedir","Q_Score":2,"Tags":"python,mysql,unit-testing,ubuntu","A_Id":1960160,"CreationDate":"2009-12-25T00:25:00.000","Title":"Start a \"throwaway\" MySQL session for testing code?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm looking a way to automate schema migration for such databases like MongoDB or CouchDB.\nPreferably, this instument should be written in python, but any other language is ok.","AnswerCount":4,"Available Count":4,"Score":1.2,"is_accepted":true,"ViewCount":5990,"Q_Id":1961013,"Users Score":19,"Answer":"Since a nosql database can contain huge amounts of data you can not migrate it in the regular rdbms sence. Actually you can't do it for rdbms as well as soon as your data passes some size threshold. It is impractical to bring your site down for a day to add a field to an existing table, and so with rdbms you end up doing ugly patches like adding new tables just for the field and doing joins to get to the data.\nIn nosql world you can do several things.\n\nAs others suggested you can write your code so that it will handle different 'versions' of the possible schema. this is usually simpler then it looks. Many kinds of schema changes are trivial to code around. for example if you want to add a new field to the schema, you just add it to all new records and it will be empty on the all old records (you will not get \"field doesn't exist\" errors or anything ;). if you need a 'default' value for the field in the old records it is too trivially done in code.\nAnother option and actually the only sane option going forward with non-trivial schema changes like field renames and structural changes is to store schema_version in EACH record, and to have code to migrate data from any version to the next on READ. i.e. if your current schema version is 10 and you read a record from the database with the version of 7, then your db layer should call migrate_8, migrate_9, and migrate_10. This way the data that is accessed will be gradually migrated to the new version. and if it is not accessed, then who cares which version is it;)","Q_Score":27,"Tags":"python,mongodb,couchdb,database,nosql","A_Id":3007620,"CreationDate":"2009-12-25T11:23:00.000","Title":"Are there any tools for schema migration for NoSQL databases?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm looking a way to automate schema migration for such databases like MongoDB or CouchDB.\nPreferably, this instument should be written in python, but any other language is ok.","AnswerCount":4,"Available Count":4,"Score":0.0996679946,"is_accepted":false,"ViewCount":5990,"Q_Id":1961013,"Users Score":2,"Answer":"One of the supposed benefits of these databases is that they are schemaless, and therefore don't need schema migration tools.  Instead, you write your data handling code to deal with the variety of data stored in the db.","Q_Score":27,"Tags":"python,mongodb,couchdb,database,nosql","A_Id":1961090,"CreationDate":"2009-12-25T11:23:00.000","Title":"Are there any tools for schema migration for NoSQL databases?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm looking a way to automate schema migration for such databases like MongoDB or CouchDB.\nPreferably, this instument should be written in python, but any other language is ok.","AnswerCount":4,"Available Count":4,"Score":0.0996679946,"is_accepted":false,"ViewCount":5990,"Q_Id":1961013,"Users Score":2,"Answer":"If your data are sufficiently big, you will probably find that you cannot EVER migrate the data, or that it is not beneficial to do so. This means that when you do a schema change, the code needs to continue to be backwards compatible with the old formats forever.\nOf course if your data \"age\" and eventually expire anyway, this can do schema migration for you - simply change the format for newly added data, then wait for all data in the old format to expire - you can then retire the backward-compatibility code.","Q_Score":27,"Tags":"python,mongodb,couchdb,database,nosql","A_Id":1966375,"CreationDate":"2009-12-25T11:23:00.000","Title":"Are there any tools for schema migration for NoSQL databases?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm looking a way to automate schema migration for such databases like MongoDB or CouchDB.\nPreferably, this instument should be written in python, but any other language is ok.","AnswerCount":4,"Available Count":4,"Score":0.049958375,"is_accepted":false,"ViewCount":5990,"Q_Id":1961013,"Users Score":1,"Answer":"When a project has a need for a schema migration in regards to a NoSQL database makes me think that you are still thinking in a Relational database manner, but using a NoSQL database.\nIf anybody is going to start working with NoSQL databases, you need to realize that most of the 'rules' for a RDBMS (i.e. MySQL) need to go out the window too.  Things like strict schemas, normalization, using many relationships between objects.  NoSQL exists to solve problems that don't need all the extra 'features' provided by a RDBMS.\nI would urge you to write your code in a manner that doesn't expect or need a hard schema for your NoSQL database - you should support an old schema and convert a document record on the fly when you access if if you really want more schema fields on that record.\nPlease keep in mind that NoSQL storage works best when you think and design differently compared to when using a RDBMS","Q_Score":27,"Tags":"python,mongodb,couchdb,database,nosql","A_Id":3007685,"CreationDate":"2009-12-25T11:23:00.000","Title":"Are there any tools for schema migration for NoSQL databases?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Python --> SQLite --> ASP.NET C#\nI am looking for an in memory database application that does not have to write the data it receives to disc. Basically, I'll be having a Python server which receives gaming UDP data and translates the data and stores it in the memory database engine.\nI want to stay away from writing to disc as it takes too long. The data is not important, if something goes wrong, it simply flushes and fills up with the next wave of data sent by players.\nNext, another ASP.NET server must be able to connect to this in memory database via TCP\/IP at regular intervals, say once every second, or 10 seconds. It has to pull this data, and this will in turn update on a website that displays \"live\" game data.\nI'm looking at SQlite, and wondering, is this the right tool for the job, anyone have any suggestions?\nThanks!!!","AnswerCount":5,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":309,"Q_Id":1962130,"Users Score":1,"Answer":"This sounds like a premature optimization (apologizes if you've already done the profiling).  What I would suggest is go ahead and write the system in the simplest, cleanest way, but put a bit of abstraction around the database bits so they can easily by swapped out.  Then profile it and find your bottleneck.\nIf it turns out it is the database, optimize the database in the usual way (indexes, query optimizations, etc...).  If its still too slow, most databases support an in-memory table format.  Or you can mount a RAM disk and mount individual tables or the whole database on it.","Q_Score":0,"Tags":"asp.net,python,sqlite,networking,udp","A_Id":1977499,"CreationDate":"2009-12-25T22:47:00.000","Title":"In memory database with socket capability","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Python --> SQLite --> ASP.NET C#\nI am looking for an in memory database application that does not have to write the data it receives to disc. Basically, I'll be having a Python server which receives gaming UDP data and translates the data and stores it in the memory database engine.\nI want to stay away from writing to disc as it takes too long. The data is not important, if something goes wrong, it simply flushes and fills up with the next wave of data sent by players.\nNext, another ASP.NET server must be able to connect to this in memory database via TCP\/IP at regular intervals, say once every second, or 10 seconds. It has to pull this data, and this will in turn update on a website that displays \"live\" game data.\nI'm looking at SQlite, and wondering, is this the right tool for the job, anyone have any suggestions?\nThanks!!!","AnswerCount":5,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":309,"Q_Id":1962130,"Users Score":0,"Answer":"The application of SQlite depends on your data complexity. \nIf you need to perform complex queries on relational data, then it might be a viable option. If your data is flat (i.e. not relational) and processed as a whole, then some python-internal data structures might be applicable.","Q_Score":0,"Tags":"asp.net,python,sqlite,networking,udp","A_Id":1962162,"CreationDate":"2009-12-25T22:47:00.000","Title":"In memory database with socket capability","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm trying to install the module mySQLdb on a windows vista 64 (amd) machine.\nI've installed python on a different folder other than suggested by Python installer.\nWhen I try to install the .exe mySQLdb installer, it can't find python 2.5 and it halts the installation.\nIs there anyway to supply the installer with the correct python location (even thou the registry and path are right)?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":431,"Q_Id":1980454,"Users Score":0,"Answer":"did you use an egg?\nif so, python might not be able to find it.\nimport os,sys\nos.environ['PYTHON_EGG_CACHE'] = 'C:\/temp'\nsys.path.append('C:\/path\/to\/MySQLdb.egg')","Q_Score":0,"Tags":"python,windows-installer,mysql","A_Id":2179175,"CreationDate":"2009-12-30T14:24:00.000","Title":"Problem installing MySQLdb on windows - Can't find python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":1,"Web Development":0},{"Question":"I'm using cherrypy's standalone server (cherrypy.quickstart()) and sqlite3 for a database.\nI was wondering how one would do ajax\/jquery asynchronous calls to the database while using cherrypy?","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":3741,"Q_Id":2015065,"Users Score":2,"Answer":"The same way you would do them using any other webserver - by getting your javascript to call a URL which is handled by the server-side application.","Q_Score":1,"Tags":"jquery,python,ajax,asynchronous,cherrypy","A_Id":2015344,"CreationDate":"2010-01-06T17:57:00.000","Title":"How does one do async ajax calls using cherrypy?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm making a trivia webapp that will feature both standalone questions, and 5+ question quizzes.  I'm looking for suggestions for designing this model.\nShould a quiz and its questions be stored in separate tables\/objects, with a key to tie them together, or am I better off creating the quiz as a standalone entity, with lists stored for each of a question's characteristics?  Or perhaps someone has another idea...\nThank you in advance.  It would probably help to say that I am using Google App Engine, which typically frowns upon relational db models, but I'm willing to go my own route if it makes sense.","AnswerCount":5,"Available Count":2,"Score":0.0399786803,"is_accepted":false,"ViewCount":642,"Q_Id":2017930,"Users Score":1,"Answer":"My first cut (I assumed the questions were multiple choice):\n\nI'd have a table of Questions, with ID_Question as the PK, the question text, and a category (if you want).\nI'd have a table of Answers, with ID_Answer as the PK, QuestionID as a FK back to the Questions table, the answer text, and a flag as to whether it's the correct answer or not.\nI'd have a table of Quizzes, with ID_Quiz as the PK, and a description of the quiz, and a category (if you want).\nI'd have a table of QuizQuestions, with ID_QuizQuestion as the PK, QuizID as a FK back to the Quizzes table, and QuestionID as a FK back to the Questions table.\n\nThis model lets you:\n\nUse questions standalone or in quizzes\nLets you have as many or few questions in a quiz as you want\nLets you have as many of few choices for questions as you want (or even multiple correct answers)\nUse questions in several different quizzes","Q_Score":1,"Tags":"python,database-design,google-app-engine,schema","A_Id":2017958,"CreationDate":"2010-01-07T02:56:00.000","Title":"Database Design Inquiry","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm making a trivia webapp that will feature both standalone questions, and 5+ question quizzes.  I'm looking for suggestions for designing this model.\nShould a quiz and its questions be stored in separate tables\/objects, with a key to tie them together, or am I better off creating the quiz as a standalone entity, with lists stored for each of a question's characteristics?  Or perhaps someone has another idea...\nThank you in advance.  It would probably help to say that I am using Google App Engine, which typically frowns upon relational db models, but I'm willing to go my own route if it makes sense.","AnswerCount":5,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":642,"Q_Id":2017930,"Users Score":0,"Answer":"Have a table of questions, a table of quizzes and a mapping table between them. That will give you the most flexibility. This is simple enough that you wouldn't even necessarily need a whole relational database management system. I think people tend to forget that relations are pretty simple mathematical\/logical concepts. An RDBMS just handles a lot of the messy book keeping for you.","Q_Score":1,"Tags":"python,database-design,google-app-engine,schema","A_Id":2017943,"CreationDate":"2010-01-07T02:56:00.000","Title":"Database Design Inquiry","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Two questions:\n\ni want to generate a View in my PostGIS-DB. How do i add this View to my geometry_columns Table?\nWhat i have to do, to use a View with SQLAlchemy? Is there a difference between a Table and View to SQLAlchemy or could i use the same way to use a View as i do to use a Table?\n\nsorry for my poor english.\nIf there a questions about my question, please feel free to ask so i can try to explain it in another way maybe :)\nNico","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1758,"Q_Id":2026475,"Users Score":4,"Answer":"Table objects in SQLAlchemy have two roles. They can be used to issue DDL commands to create the table in the database. But their main purpose is to describe the columns and types of tabular data that can be selected from and inserted to.\nIf you only want to select, then a view looks to SQLAlchemy exactly like a regular table. It's enough to describe the view as a Table with the columns that interest you (you don't even need to describe all of the columns). If you want to use the ORM you'll need to declare for SQLAlchemy that some combination of the columns can be used as the primary key (anything that's unique will do). Declaring some columns as foreign keys will also make it easier to set up any relations. If you don't issue create for that Table object, then it is just metadata for SQLAlchemy to know how to query the database.\nIf you also want to insert to the view, then you'll need to create PostgreSQL rules or triggers on the view that redirect the writes to the correct location. I'm not aware of a good usage recipe to redirect writes on the Python side.","Q_Score":2,"Tags":"python,postgresql,sqlalchemy,postgis","A_Id":2027143,"CreationDate":"2010-01-08T09:05:00.000","Title":"Work with Postgres\/PostGIS View in SQLAlchemy","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"hmm, is there any reason why sa tries to add Nones to for varchar columns that have defaults set in in database schema ?, it doesnt do that for floats or ints (im using reflection).\nso when i try to add new row :\nlike\nu = User()\nu.foo = 'a'\nu.bar = 'b'\nsa issues a query that has a lot more cols with None values assigned to those, and db obviously bards and doesnt perform default substitution.","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":900,"Q_Id":2036996,"Users Score":0,"Answer":"I've found its a bug in sa, this happens only for string fields, they dont get server_default property for some unknow reason, filed a ticket for this already","Q_Score":0,"Tags":"python,sqlalchemy","A_Id":2037291,"CreationDate":"2010-01-10T12:28:00.000","Title":"Problem with sqlalchemy, reflected table and defaults for string fields","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"i have been in the RDBMS world for many years now but wish to explore the whole nosql movement.  so here's my first question:\nis it bad practice to have the possibility of duplicate keys?  for example, an address book keyed off of last name (most probably search item?) could have multiple entities.  is it bad practice to use the last name then?  is the key supposed to be the most \"searchable\" definition of the entity?  are there any resources for \"best practices\" in this whole new world (for me)?\ni'm intrigued by tokyo cabinet (and specifically the tc interface) but don't know how to iterate through different entities that have the same key (e.g. see above).  i can only get the first entity.  anyway, thanks in advance for the help","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":597,"Q_Id":2068473,"Users Score":1,"Answer":"This depend on no-sql implementation. Cassandra, for example, allows range queries, so you could model data to do queries on last name, or with full name (starting with last name, then first name).\nBeyond this, many simpler key-value stores would indeed require you to store a list structure (or such) for multi-valued entries. Whether this is feasible or not depends on expected number of \"duplicates\" -- with last name, number could be rather high I presume, so it does not sound like an ideal model for many cases.","Q_Score":1,"Tags":"python,tokyo-cabinet","A_Id":2384015,"CreationDate":"2010-01-15T00:04:00.000","Title":"key\/value (general) and tokyo cabinet (python tc-specific) question","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a script with a main for loop that repeats about 15k times. In this loop it queries a local MySQL database and does a SVN update on a local repository. I placed the SVN repository in a RAMdisk as before most of the time seemed to be spent reading\/writing to disk.\nNow I have a script that runs at basically the same speed but CPU utilization for that script never goes over 10%.\nProcessExplorer shows that mysqld is also not taking almost any CPU time or reading\/writing a lot to disk.\nWhat steps would you take to figure out where the bottleneck is?","AnswerCount":3,"Available Count":3,"Score":0.0665680765,"is_accepted":false,"ViewCount":917,"Q_Id":2076582,"Users Score":1,"Answer":"It is \"well known\", so to speak, that svn update waits up to a whole second after it has finished running, so that file modification timestamps get \"in the past\" (since many filesystems don't have a timestamp granularity finer than one second). You can find more information about it by Googling for \"svn sleep_for_timestamps\".\nI don't have any obvious solution to suggest. If this is really performance critical you could either: 1) not update as often as you are doing 2) try to use a lower-level Subversion API (good luck).","Q_Score":2,"Tags":"python,mysql,performance,svn","A_Id":2077129,"CreationDate":"2010-01-16T07:40:00.000","Title":"Finding the performance bottleneck in a Python and MySQL script","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a script with a main for loop that repeats about 15k times. In this loop it queries a local MySQL database and does a SVN update on a local repository. I placed the SVN repository in a RAMdisk as before most of the time seemed to be spent reading\/writing to disk.\nNow I have a script that runs at basically the same speed but CPU utilization for that script never goes over 10%.\nProcessExplorer shows that mysqld is also not taking almost any CPU time or reading\/writing a lot to disk.\nWhat steps would you take to figure out where the bottleneck is?","AnswerCount":3,"Available Count":3,"Score":1.2,"is_accepted":true,"ViewCount":917,"Q_Id":2076582,"Users Score":4,"Answer":"Doing SQL queries in a for loop 15k times is a bottleneck in every language.. \nIs there any reason you query every time again ? If you do a single query before the for loop and then loop over the resultset and the SVN part, you will see a dramatic increase in speed.\nBut I doubt that you will get a higher CPU usage. The reason is that you are not doing calculations, but mostly IO. \nBtw, you can't measure that in mysqld cpu usage, as it's in the actual code not complexity of the queries, but their count and the latency of the server engine to answer. So you will see only very short, not expensive queries, that do sum up in time, though.","Q_Score":2,"Tags":"python,mysql,performance,svn","A_Id":2076639,"CreationDate":"2010-01-16T07:40:00.000","Title":"Finding the performance bottleneck in a Python and MySQL script","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a script with a main for loop that repeats about 15k times. In this loop it queries a local MySQL database and does a SVN update on a local repository. I placed the SVN repository in a RAMdisk as before most of the time seemed to be spent reading\/writing to disk.\nNow I have a script that runs at basically the same speed but CPU utilization for that script never goes over 10%.\nProcessExplorer shows that mysqld is also not taking almost any CPU time or reading\/writing a lot to disk.\nWhat steps would you take to figure out where the bottleneck is?","AnswerCount":3,"Available Count":3,"Score":0.0665680765,"is_accepted":false,"ViewCount":917,"Q_Id":2076582,"Users Score":1,"Answer":"Profile your Python code. That will show you how long each function\/method call takes. If that's the method call querying the MySQL database, you'll have a clue where to look. But it also may be something else. In any case, profiling is the usual approach to solve such problems.","Q_Score":2,"Tags":"python,mysql,performance,svn","A_Id":2076590,"CreationDate":"2010-01-16T07:40:00.000","Title":"Finding the performance bottleneck in a Python and MySQL script","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I recently joined a new company and the development team was in the progress of a project to rebuild the database categories structure as follows:\nif we have category and subcategory for items, like food category and italian food category in food category.\nThey were building a table for each category, instead of having one table and a link to the category id.\nNow we have a table called food\nand another table called food_italian\nand both tables contain the same fields.\nI have asked around and it seems that some DBA prefers this design. I would like to know why? and how this design can improve the performance?","AnswerCount":2,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":155,"Q_Id":2077522,"Users Score":2,"Answer":"First, the most obvious answer is that you should ask them, not us, since I can tell you this, that design seems bogus deluxe.\nThe only reason I can come up with is that you have inexperienced DBA's that does not know how to performance-tune a database, and seems to think that a table with less rows will always vastly outperform a table with more rows.\nWith good indices, that need not be the case.","Q_Score":2,"Tags":"python,mysql,database,django,performance","A_Id":2077536,"CreationDate":"2010-01-16T13:58:00.000","Title":"DB a table for the category and another table for the subcategory with similar fields, why?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a question related to some guidances to solve a problem. I have with me an xml file, I have to populate it into a database system (whatever, it might be sqlite, mysql) using scripting language: Python.\nDoes anyone have any idea on how to proceed?\n\nWhich technologies I need to read further?\nWhich environments I have to install?\nAny tutorials on the same topic?\n\nI already tried to parse xml using both by tree-based and sax method in other language, but to start with Python, I don't know where to start. I already know how to design the database I need. \nAnother question, is Python alone possible of executing database ddl queries?","AnswerCount":4,"Available Count":1,"Score":0.049958375,"is_accepted":false,"ViewCount":15042,"Q_Id":2085430,"Users Score":1,"Answer":"If you are accustomed to DOM (tree) access to xml from other language, you may find useful these standard library modules (and their respective docs):\n\nxml.dom \nxml.dom.minidom\n\nTo save tha data to DB, you can use standard module sqlite3 or look for binding to mysql. Or you may wish to use something more abstract, like SQLAlchemy or Django's ORM.","Q_Score":7,"Tags":"python,xml,database,sqlite,parsing","A_Id":2085657,"CreationDate":"2010-01-18T10:55:00.000","Title":"populating data from xml file to a sqlite database using python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a written a Python module which due to its specifics needs to have a MySQL database connection. Right now, details of this connection (host, database, username and password to connect with) are stored in \/etc\/mymodule.conf in plaintext, which is obviously not a good idea.\nSupposedly, the \/etc\/mymodule.conf file is edited by the root user after the module is installed, since the module and its database may be used by all users of a Unix system.\nHow should I securely store the password instead?","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1241,"Q_Id":2087920,"Users Score":4,"Answer":"Your constraints set a very difficult problem: every user on the system must be able to access that password (since that's the only way for users to access that database)... yet they must not (except when running that script, and presumably only when running it without e.g. a python -i session that would let them set a breakpoint just before the connect call and look all through memory, so definitely able to look at the password).\nYou could write a daemon process that runs as root (so can read mymodule.conf, which you'd make readable only by root) and accepts requests, somehow validates that the request comes from a \"good\" process (one that's running the exact module in question and not interactive), and only then supplies the password.  That's fragile, mostly because of the need to determine whether a process may or may not have a breakpoint set at the crucial point of execution.\nAlternatively, you could further raise the technological stakes by having the daemon return, not the password, but rather the open socket ready to be wrapped in a DB-API compliant wrapper; some Unix systems allow open file descriptors to be sent between unrelated processes (a prereq for this approach) -- and of course you'd have to substantially rework the MySQL-based DB API to allow opening a connection around an already-open socket rather than a freshly made one.  Note that a validated requesting process that happens to be interactive would still be able to get the connection object, once built, and send totally arbitrary requests -- they wouldn't be able to see the password, technically, but that's not much consolation.  So it's unlikely that the large effort required here is warranted.\nSo the next possible architecture is to mediate all db interaction via the validating daemon: a process would \"log into\" the daemon, get validated, and, if all's OK, gain a proxy connection to (e.g.) an XMLRPC server exposing the DB connection and functionality (the daemon would probably fork each such proxy process, right after reading the password from the root-only-readable file, and drop privileges immediately, just on general security ground).\nThe plus wrt the previous alternative, in addition to probably easier implementation, is that the proxy would also get a look at every SQL request that's about to be sent to the MySQL db, and be able to validate and censor those requests as well (presumably on a default-deny basis, again for general security principles), thus seriously limiting the amount of damage a \"rogue\" client process (running interactively with a debugger) can do... one hopes;-).\nYes, no easy solutions here -- but then, the problem your constraints pose is so far from easy that it borders on a self-contradictory impossibility;-).  BTW, the problem's not particularly Python-related, it's essentially about choosing a secure architecture that comes close to \"squaring the circle\"-hard contradictory constraints on access permissions!-)","Q_Score":0,"Tags":"python,security","A_Id":2088188,"CreationDate":"2010-01-18T17:30:00.000","Title":"Storing system-wide DB connection password for a Python module","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I want to add a field to an existing mapped class, how would I update the sql table automatically. Does sqlalchemy provide a method to update the database with a new column, if a field is added to the class.","AnswerCount":6,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":11257,"Q_Id":2103274,"Users Score":0,"Answer":"You can install 'DB Browser (SQLite)' and open your current database file and simple add\/edit table in your database and save it, and run your app\n(add script in your model after save above process)","Q_Score":15,"Tags":"python,sqlalchemy","A_Id":65265231,"CreationDate":"2010-01-20T17:01:00.000","Title":"SqlAlchemy add new Field to class and create corresponding column in table","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Background\nI have many (thousands!) of data files with a standard field based format (think tab-delimited, same fields in every line, in every file).  I'm debating various ways of making this data available \/ searchable.  (Some options include RDBMS, NoSQL stuff, using the grep\/awk and friends, etc.).  \nProposal\nIn particular, one idea that appeals to me is \"indexing\" the files in some way. Since these files are read-only (and static), I was imagining some persistent files containing binary trees (one for each indexed field, just like in other data stores).  I'm open to ideas about how to this, or to hearing that this is simply insane.  Mostly, my favorite search engine hasn't yielded me any pre-rolled solutions for this.  \nI realize this is a little ill-formed, and solutions are welcome.\nAdditional Details\n\nfiles long, not wide\n\n\nmillions of lines per hour, spread over 100 files per hour\ntab seperated, not many columns (~10) \nfields are short (say < 50 chars per field)\n\nqueries are on fields, combinations of fields, and can be historical\n\nDrawbacks to various solutions:\n(All of these are based on my observations and tests, but I'm open to correction)\nBDB\n\nhas problems with scaling to large file sizes (in my experience, once they're 2GB or so, performance can be terrible)\nsingle writer (if it's possible to get around this, I want to see code!)\nhard to do multiple indexing, that is, indexing on different fields at once (sure you can do this by copying the data over and over). \nsince it only stores strings, there is a serialize \/ deserialize step\n\nRDBMSes\nWins:\n\nflat table model is excellent for querying, indexing\n\nLosses:\n\nIn my experience, the problem comes with indexing.  From what I've seen (and please correct me if I am wrong), the issue with rdbmses I know (sqlite, postgres) supporting either batch load (then indexing is slow at the end), or row by row loading (which is low).  Maybe I need more performance tuning.","AnswerCount":5,"Available Count":3,"Score":0.0399786803,"is_accepted":false,"ViewCount":2801,"Q_Id":2110843,"Users Score":1,"Answer":"If the data is already organized in fields, it doesn't sound like a text searching\/indexing problem. It sounds like tabular data that would be well-served by a database.\nScript the file data into a database, index as you see fit, and query the data in any complex way the database supports.\nThat is unless you're looking for a cool learning project. Then, by all means, come up with an interesting file indexing scheme.","Q_Score":4,"Tags":"python,algorithm,indexing,binary-tree","A_Id":2111067,"CreationDate":"2010-01-21T16:22:00.000","Title":"File indexing (using Binary trees?) in Python","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Background\nI have many (thousands!) of data files with a standard field based format (think tab-delimited, same fields in every line, in every file).  I'm debating various ways of making this data available \/ searchable.  (Some options include RDBMS, NoSQL stuff, using the grep\/awk and friends, etc.).  \nProposal\nIn particular, one idea that appeals to me is \"indexing\" the files in some way. Since these files are read-only (and static), I was imagining some persistent files containing binary trees (one for each indexed field, just like in other data stores).  I'm open to ideas about how to this, or to hearing that this is simply insane.  Mostly, my favorite search engine hasn't yielded me any pre-rolled solutions for this.  \nI realize this is a little ill-formed, and solutions are welcome.\nAdditional Details\n\nfiles long, not wide\n\n\nmillions of lines per hour, spread over 100 files per hour\ntab seperated, not many columns (~10) \nfields are short (say < 50 chars per field)\n\nqueries are on fields, combinations of fields, and can be historical\n\nDrawbacks to various solutions:\n(All of these are based on my observations and tests, but I'm open to correction)\nBDB\n\nhas problems with scaling to large file sizes (in my experience, once they're 2GB or so, performance can be terrible)\nsingle writer (if it's possible to get around this, I want to see code!)\nhard to do multiple indexing, that is, indexing on different fields at once (sure you can do this by copying the data over and over). \nsince it only stores strings, there is a serialize \/ deserialize step\n\nRDBMSes\nWins:\n\nflat table model is excellent for querying, indexing\n\nLosses:\n\nIn my experience, the problem comes with indexing.  From what I've seen (and please correct me if I am wrong), the issue with rdbmses I know (sqlite, postgres) supporting either batch load (then indexing is slow at the end), or row by row loading (which is low).  Maybe I need more performance tuning.","AnswerCount":5,"Available Count":3,"Score":0.0399786803,"is_accepted":false,"ViewCount":2801,"Q_Id":2110843,"Users Score":1,"Answer":"The physical storage access time will tend to dominate anything you do.  When you profile, you'll find that the read() is where you spend most of your time.\nTo reduce the time spent waiting for I\/O, your best bet is compression.\nCreate a huge ZIP archive of all of your files.  One open, fewer reads.  You'll spend more CPU time.  I\/O time, however, will dominate your processing, so reduce I\/O time by zipping everything.","Q_Score":4,"Tags":"python,algorithm,indexing,binary-tree","A_Id":2110912,"CreationDate":"2010-01-21T16:22:00.000","Title":"File indexing (using Binary trees?) in Python","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Background\nI have many (thousands!) of data files with a standard field based format (think tab-delimited, same fields in every line, in every file).  I'm debating various ways of making this data available \/ searchable.  (Some options include RDBMS, NoSQL stuff, using the grep\/awk and friends, etc.).  \nProposal\nIn particular, one idea that appeals to me is \"indexing\" the files in some way. Since these files are read-only (and static), I was imagining some persistent files containing binary trees (one for each indexed field, just like in other data stores).  I'm open to ideas about how to this, or to hearing that this is simply insane.  Mostly, my favorite search engine hasn't yielded me any pre-rolled solutions for this.  \nI realize this is a little ill-formed, and solutions are welcome.\nAdditional Details\n\nfiles long, not wide\n\n\nmillions of lines per hour, spread over 100 files per hour\ntab seperated, not many columns (~10) \nfields are short (say < 50 chars per field)\n\nqueries are on fields, combinations of fields, and can be historical\n\nDrawbacks to various solutions:\n(All of these are based on my observations and tests, but I'm open to correction)\nBDB\n\nhas problems with scaling to large file sizes (in my experience, once they're 2GB or so, performance can be terrible)\nsingle writer (if it's possible to get around this, I want to see code!)\nhard to do multiple indexing, that is, indexing on different fields at once (sure you can do this by copying the data over and over). \nsince it only stores strings, there is a serialize \/ deserialize step\n\nRDBMSes\nWins:\n\nflat table model is excellent for querying, indexing\n\nLosses:\n\nIn my experience, the problem comes with indexing.  From what I've seen (and please correct me if I am wrong), the issue with rdbmses I know (sqlite, postgres) supporting either batch load (then indexing is slow at the end), or row by row loading (which is low).  Maybe I need more performance tuning.","AnswerCount":5,"Available Count":3,"Score":0.0399786803,"is_accepted":false,"ViewCount":2801,"Q_Id":2110843,"Users Score":1,"Answer":"sqlite3 is fast, small, part of python (so nothing to install) and provides indexing of columns. It writes to files, so you wouldn't need to install a database system.","Q_Score":4,"Tags":"python,algorithm,indexing,binary-tree","A_Id":12805622,"CreationDate":"2010-01-21T16:22:00.000","Title":"File indexing (using Binary trees?) in Python","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Table structure - Data present for 5 min. slots -\ndata_point  |   point_date\n12          |   00:00\n14          |   00:05\n23           |   00:10\n10          |   00:15\n43           |   00:25\n10          |   00:40  \nWhen I run the query for say 30 mins. and if data is present I'll get 6 rows (one row for each 5 min. stamp). Simple Query -\nselect data_point\nfrom some_table\nwhere point_date >= start_date\nAND point_date < end_date\norder by point_date\nNow when I don't have an entry for a particular time slot (e.g. time slot 00:20 is missing), I want the \"data_point\" to be returned as 0\nThe REPLACE, IF, IFNULL, ISNULL don't work when there no rows returned.\nI thought Union with a default value would work, but it failed too or maybe I didn't use it correctly.\nIs there a way to get this done via sql only ?\nNote :  Python 2.6 & mysql version 5.1","AnswerCount":3,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":1466,"Q_Id":2119153,"Users Score":0,"Answer":"You cannot query data you do not have.\nYou (as a thinking person) can claim that the 00:20 data is missing; but there's no easy way to define \"missing\" in some more formal SQL sense.\nThe best you can do is create a table with all of the expected times.\nThen you can do an outer join between expected times (including a 0 for 00:20) and actual times (missing the 00:20 sample) and you'll get kind of result you're expecting.","Q_Score":1,"Tags":"python,mysql,null","A_Id":2119402,"CreationDate":"2010-01-22T17:28:00.000","Title":"python : mysql : Return 0 when no rows found","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Table structure - Data present for 5 min. slots -\ndata_point  |   point_date\n12          |   00:00\n14          |   00:05\n23           |   00:10\n10          |   00:15\n43           |   00:25\n10          |   00:40  \nWhen I run the query for say 30 mins. and if data is present I'll get 6 rows (one row for each 5 min. stamp). Simple Query -\nselect data_point\nfrom some_table\nwhere point_date >= start_date\nAND point_date < end_date\norder by point_date\nNow when I don't have an entry for a particular time slot (e.g. time slot 00:20 is missing), I want the \"data_point\" to be returned as 0\nThe REPLACE, IF, IFNULL, ISNULL don't work when there no rows returned.\nI thought Union with a default value would work, but it failed too or maybe I didn't use it correctly.\nIs there a way to get this done via sql only ?\nNote :  Python 2.6 & mysql version 5.1","AnswerCount":3,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":1466,"Q_Id":2119153,"Users Score":0,"Answer":"I see no easy way to create non-existing records out of thin air, but you could create yourself a point_dates table containing all the timestamps you're interested in, and left join it on your data:\nselect pd.slot, IFNULL(data_point, 0)\nfrom point_dates pd\nleft join some_table st on st.point_date=pd.slot\nwhere point_date >= start_date\nAND point_date < end_date\norder by point_date","Q_Score":1,"Tags":"python,mysql,null","A_Id":2119384,"CreationDate":"2010-01-22T17:28:00.000","Title":"python : mysql : Return 0 when no rows found","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I've prototyped an iPhone app that uses (internally) SQLite as its data base.  The intent was to ultimately have it communicate with a server via PHP, which would use MySQL as the back-end database.  \nI just discovered Google App Engine, however, but know very little about it.  I think it'd be nice to use the Python interface to write to the data store - but I know very little about GQL's capability.  I've basically written all the working database code using MySQL, testing internally on the iPhone with SQLite.  Will GQL offer the same functionality that SQL can?  I read on the site that it doesn't support join queries.  Also is it truly relational?  \nBasically I guess my question is can an app that typically uses SQL backend work just as well with Google's App Engine, with GQL?\nI hope that's clear... any guidance is great.","AnswerCount":4,"Available Count":3,"Score":1.2,"is_accepted":true,"ViewCount":1021,"Q_Id":2124688,"Users Score":2,"Answer":"True, Google App Engine is a very cool product, but the datastore is a different beast than a regular mySQL database.  That's not to say that what you need can't be done with the GAE datastore; however it may take some reworking on your end. \nThe most prominent different that you notice right off the start is that GAE uses an object-relational mapping for its data storage scheme.  Essentially object graphs are persisted in the database, maintaining there attributes and relationships to other objects.  In many cases ORM (object relational mappings) map fairly well on top of a relational database (this is how Hibernate works).  The mapping is not perfect though and you will find that you need to make alterations to persist your data.  Also, GAE has some unique contraints that complicate things a bit.  One contraint that bothers me a lot is not being able to query for attribute paths: e.g. \"select ... where dog.owner.name = 'bob' \".  It is these rules that force you to read and understand how GAE data store works before you jump in. \nI think GAE could work well in your situation.  It just may take some time to understand ORM persistence in general, and GAE datastore in specifics.","Q_Score":2,"Tags":"iphone,python,google-app-engine,gql","A_Id":2124718,"CreationDate":"2010-01-23T20:55:00.000","Title":"iPhone app with Google App Engine","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I've prototyped an iPhone app that uses (internally) SQLite as its data base.  The intent was to ultimately have it communicate with a server via PHP, which would use MySQL as the back-end database.  \nI just discovered Google App Engine, however, but know very little about it.  I think it'd be nice to use the Python interface to write to the data store - but I know very little about GQL's capability.  I've basically written all the working database code using MySQL, testing internally on the iPhone with SQLite.  Will GQL offer the same functionality that SQL can?  I read on the site that it doesn't support join queries.  Also is it truly relational?  \nBasically I guess my question is can an app that typically uses SQL backend work just as well with Google's App Engine, with GQL?\nI hope that's clear... any guidance is great.","AnswerCount":4,"Available Count":3,"Score":0.049958375,"is_accepted":false,"ViewCount":1021,"Q_Id":2124688,"Users Score":1,"Answer":"That's a pretty generic question :)\nShort answer: yes.  It's going to involve some rethinking of your data model, but yes, changes are you can support it with the GAE Datastore API.\nWhen you create your Python models (think of these as tables), you can certainly define references to other models (so now we have a foreign key).  When you select this model, you'll get back the referencing models (pretty much like a join).\nIt'll most likely work, but it's not a drop in replacement for a mySQL server.","Q_Score":2,"Tags":"iphone,python,google-app-engine,gql","A_Id":2124705,"CreationDate":"2010-01-23T20:55:00.000","Title":"iPhone app with Google App Engine","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I've prototyped an iPhone app that uses (internally) SQLite as its data base.  The intent was to ultimately have it communicate with a server via PHP, which would use MySQL as the back-end database.  \nI just discovered Google App Engine, however, but know very little about it.  I think it'd be nice to use the Python interface to write to the data store - but I know very little about GQL's capability.  I've basically written all the working database code using MySQL, testing internally on the iPhone with SQLite.  Will GQL offer the same functionality that SQL can?  I read on the site that it doesn't support join queries.  Also is it truly relational?  \nBasically I guess my question is can an app that typically uses SQL backend work just as well with Google's App Engine, with GQL?\nI hope that's clear... any guidance is great.","AnswerCount":4,"Available Count":3,"Score":0.0996679946,"is_accepted":false,"ViewCount":1021,"Q_Id":2124688,"Users Score":2,"Answer":"GQL offers almost no functionality at all; it's only used for SELECT queries, and it only exists to make writing SELECT queries easier for SQL programmers.  Behind the scenes, it converts your queries to db.Query objects.\nThe App Engine datastore isn't a relational database at all.  You can do some stuff that looks relational, but my advice for anyone coming from an SQL background is to avoid GQL at all costs to avoid the trap of thinking the datastore is anything at all like an RDBMS, and to forget everything you know about database design.  Specifically, if you're normalizing anything, you'll soon wish you hadn't.","Q_Score":2,"Tags":"iphone,python,google-app-engine,gql","A_Id":2125297,"CreationDate":"2010-01-23T20:55:00.000","Title":"iPhone app with Google App Engine","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"Currently an application of mine is using SQLAlchemy, but I have been considering the possibility of using Django model API. \nDjango 1.1.1 is about 3.6 megabytes in size, whereas SQLAlchemy is about 400 kilobytes (as reported by PyPM - which is essentially the size of the files installed by python setup.py install).\nI would like to use the Django models (so as to not have other developers learn yet-another-ORM), but do not want to include 3.6 megabytes of stuff most of which are not needed. (FYI - the application, final executable that is, actually bundles the install_requires from setup.py)","AnswerCount":2,"Available Count":2,"Score":0.0996679946,"is_accepted":false,"ViewCount":191,"Q_Id":2126433,"Users Score":1,"Answer":"The Django ORM is usable on its own - you can use \"settings.configure()\" to set up the database settings. That said, you'll have to do the stripping down and repackaging yourself, and you'll have to experiment with how much you can actually strip away. I'm sure you can ditch contrib\/, forms\/, template\/, and probably several other unrelated pieces. The ORM definitely relies on conf\/, and quite likely on core\/ and util\/ as well. A few quick greps through db\/* should make it clear what's imported.","Q_Score":0,"Tags":"python,django,deployment,size,sqlalchemy","A_Id":2127512,"CreationDate":"2010-01-24T08:27:00.000","Title":"Using Django's Model API without having to *include* the full Django stack","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Currently an application of mine is using SQLAlchemy, but I have been considering the possibility of using Django model API. \nDjango 1.1.1 is about 3.6 megabytes in size, whereas SQLAlchemy is about 400 kilobytes (as reported by PyPM - which is essentially the size of the files installed by python setup.py install).\nI would like to use the Django models (so as to not have other developers learn yet-another-ORM), but do not want to include 3.6 megabytes of stuff most of which are not needed. (FYI - the application, final executable that is, actually bundles the install_requires from setup.py)","AnswerCount":2,"Available Count":2,"Score":0.0996679946,"is_accepted":false,"ViewCount":191,"Q_Id":2126433,"Users Score":1,"Answer":"You may be able to get a good idea of what is safe to strip out by checking which files don't have their access time updated when you run your application.","Q_Score":0,"Tags":"python,django,deployment,size,sqlalchemy","A_Id":2130014,"CreationDate":"2010-01-24T08:27:00.000","Title":"Using Django's Model API without having to *include* the full Django stack","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Could anyone explain the difference between filter and filter_by functions in SQLAlchemy?\nWhich one should I be using?","AnswerCount":5,"Available Count":4,"Score":1.0,"is_accepted":false,"ViewCount":221892,"Q_Id":2128505,"Users Score":133,"Answer":"We actually had these merged together originally, i.e. there was a \"filter\"-like method that accepted *args and **kwargs, where you could pass a SQL expression or keyword arguments (or both).  I actually find that a lot more convenient, but people were always confused by it, since they're usually still getting over the difference between column == expression and keyword = expression.  So we split them up.","Q_Score":380,"Tags":"python,sqlalchemy","A_Id":2157930,"CreationDate":"2010-01-24T19:49:00.000","Title":"Difference between filter and filter_by in SQLAlchemy","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Could anyone explain the difference between filter and filter_by functions in SQLAlchemy?\nWhich one should I be using?","AnswerCount":5,"Available Count":4,"Score":1.0,"is_accepted":false,"ViewCount":221892,"Q_Id":2128505,"Users Score":40,"Answer":"filter_by uses keyword arguments, whereas filter allows pythonic filtering arguments like filter(User.name==\"john\")","Q_Score":380,"Tags":"python,sqlalchemy","A_Id":2128567,"CreationDate":"2010-01-24T19:49:00.000","Title":"Difference between filter and filter_by in SQLAlchemy","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Could anyone explain the difference between filter and filter_by functions in SQLAlchemy?\nWhich one should I be using?","AnswerCount":5,"Available Count":4,"Score":1.2,"is_accepted":true,"ViewCount":221892,"Q_Id":2128505,"Users Score":494,"Answer":"filter_by is used for simple queries on the column names using regular kwargs, like\ndb.users.filter_by(name='Joe')\nThe same can be accomplished with filter, not using kwargs, but instead using the '==' equality operator, which has been overloaded on the db.users.name object:\ndb.users.filter(db.users.name=='Joe')\nYou can also write more powerful queries using filter, such as expressions like:\ndb.users.filter(or_(db.users.name=='Ryan', db.users.country=='England'))","Q_Score":380,"Tags":"python,sqlalchemy","A_Id":2128558,"CreationDate":"2010-01-24T19:49:00.000","Title":"Difference between filter and filter_by in SQLAlchemy","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Could anyone explain the difference between filter and filter_by functions in SQLAlchemy?\nWhich one should I be using?","AnswerCount":5,"Available Count":4,"Score":0.1586485043,"is_accepted":false,"ViewCount":221892,"Q_Id":2128505,"Users Score":4,"Answer":"Apart from all the technical information posted before, there is a significant difference between filter() and filter_by() in its usability.\nThe second one, filter_by(), may be used only for filtering by something specifically stated - a string or some number value. So it's usable only for category filtering, not for expression filtering.\nOn the other hand filter() allows using comparison expressions (==, <, >, etc.) so it's helpful e.g. when 'less\/more than' filtering is needed. But can be used like filter_by() as well (when == used).\nJust to remember both functions have different syntax for argument typing.","Q_Score":380,"Tags":"python,sqlalchemy","A_Id":68331326,"CreationDate":"2010-01-24T19:49:00.000","Title":"Difference between filter and filter_by in SQLAlchemy","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"we are still pretty new to Postgres and came from Microsoft Sql Server.\nWe are wanting to write some stored procedures now. Well, after struggling to get something more complicated than a hello world to work in pl\/pgsql, we decided it's better if we are going to learn a new language we might as well learn Python because we got the same query working in it in about 15 minutes(note, none of us actually know python). \nSo I have some questions about it in comparison to pl\/psql. \n\nIs pl\/Pythonu slower than pl\/pgsql? \nIs there any kind of \"good\" reference for how to write good stored procedures using it? Five short pages in the Postgres documentation doesn't really tell us enough.\nWhat about query preparation? Should it always be used? \nIf we use the SD and GD arrays for a lot of query plans, will it ever get too full or have a negative impact on the server? Will it automatically delete old values if it gets too full?\nIs there any hope of it becoming a trusted language? \n\nAlso, our stored procedure usage is extremely light. Right now we only have 4, but we are still trying to convert little bits of code over from Sql Server specific syntax(such as variables, which can't be used in Postgres outside of stored procedures)","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":5869,"Q_Id":2141589,"Users Score":9,"Answer":"Depends on what operations you're doing.\nWell, combine that with a general Python documentation, and that's about what you have.\nNo. Again, depends on what you're doing. If you're only going to run a query once, no point in preparing it separately.\nIf you are using persistent connections, it might. But they get cleared out whenever a connection is closed.\nNot likely. Sandboxing is broken in Python and AFAIK nobody is really interested in fixing it. I heard someone say that python-on-parrot may be the most viable way, once we have pl\/parrot (which we don't yet).\n\nBottom line though - if your stored procedures are going to do database work, use pl\/pgsql. Only use pl\/python if you are going to do non-database stuff, such as talking to external libraries.","Q_Score":11,"Tags":"python,postgresql,stored-procedures,plpgsql","A_Id":2142128,"CreationDate":"2010-01-26T18:19:00.000","Title":"Stored Procedures in Python for PostgreSQL","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a queryset with a few million records. I need to update a Boolean Value, fundamentally toggle it, so that in the database table the values are reset. What's the fastest way to do that?\nI tried traversing the queryset and updating and saving each record, that obviously takes ages? We need to do this very fast, any suggestions?","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1711,"Q_Id":2141769,"Users Score":0,"Answer":"Actually, that didn't work out for me.\nThe following did:\nEntry.objects.all().update(value=(F('value')==False))","Q_Score":7,"Tags":"python,database,django,django-queryset","A_Id":4230081,"CreationDate":"2010-01-26T18:50:00.000","Title":"Fastest Way to Update a bunch of records in queryset in Django","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Why is _mysql in the MySQLdb module a C file? When the module tries to import it, I get an import error. What should I do?","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1242,"Q_Id":2169449,"Users Score":0,"Answer":"It's the adaptor that sits between the Python MySQLdb module and the C libmysqlclient library. One of the most common reasons for it not loading is that the appropriate libmysqlclient library is not in place.","Q_Score":1,"Tags":"python,mysql,c","A_Id":2169464,"CreationDate":"2010-01-30T21:12:00.000","Title":"Importing _mysql in MySQLdb","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am attempting to execute the following query via the mysqldb module in python:\nfor i in self.p.parameter_type:\n    cursor.execute(\"\"\"UPDATE parameters SET %s = %s WHERE parameter_set_name = %s\"\"\" % (i,\n               float(getattr(self.p, i)), self.list_box_parameter.GetStringSelection()))\nI keep getting the error: \"Unknown column 'M1' in 'where clause'\". I want to update columns i with the value getattr(self.p, i), but only in rows that have the column parameter_set_name equal to self.list_box_parameter.GetStringSelection(). The error suggests that my query is looking for columns by the name 'M1' in the WHERE clause. Why is the above query incorrect and how can I correct it?","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":375,"Q_Id":2171072,"Users Score":0,"Answer":"It looks like query is formed with wrong syntax.\nCould you display string parameter of cursor.execute?","Q_Score":0,"Tags":"python,mysql","A_Id":2171104,"CreationDate":"2010-01-31T08:45:00.000","Title":"Trouble with MySQL UPDATE syntax with the module mysqldb in Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm trying to implement the proper architecture for multiple databases under Python + Pylons.  I can't put everything in the config files since one of the database connections requires the connection info from a previous database connection (sharding).  \nWhat's the best way to implement such an infrastructure?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":988,"Q_Id":2205047,"Users Score":1,"Answer":"Pylons's template configures the database in config\/environment.py, probably with the engine_from_config method. It finds all the config settings with a particular prefix and passes them as keyword arguments to create_engine.\nYou can just replace that with a few calls to sqlalchemy.create_engine() with the per-engine url, and common username, and password from your config file.","Q_Score":2,"Tags":"python,pylons","A_Id":2224250,"CreationDate":"2010-02-05T04:29:00.000","Title":"Multiple database connections with Python + Pylons + SQLAlchemy","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"TypeError: unsupported operand type(s) for \/: 'tuple' and 'tuple'\nI'm getting above error , while I fetched a record  using query \"select max(rowid) from table\"\nand assigned it to variable and while performing \/ operation is throws above message.\nHow to resolve this.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1106,"Q_Id":2220099,"Users Score":4,"Answer":"Sql query select max(rowid) would return Tuple data like records=(1000,)\nYou may need to do like numerator \/ records[0]","Q_Score":1,"Tags":"python,tuples","A_Id":2220107,"CreationDate":"2010-02-08T07:18:00.000","Title":"python tuple division","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"Suppose that I have a table Articles, which has fields article_id, content and it contains one article with id 1.\nI also have a table Categories, which has fields category_id (primary key), category_name, and it contains one category with id 10.\nNow suppose that I have a table ArticleProperties, that adds properties to Articles. This table has fields article_id, property_name, property_value.\nSuppose that I want to create a mapping from Categories to Articles via ArticleProperties table.\nI do this by inserting the following values in the ArticleProperties table: (article_id=1, property_name=\"category\", property_value=10).\nIs there any way in SQLAlchemy to express that rows in table ArticleProperties with property_name \"category\" are actually FOREIGN KEYS of table Articles to table Categories?\nThis is a complicated problem and I haven't found an answer myself.\nAny help appreciated!\nThanks, Boda Cydo.","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":928,"Q_Id":2234030,"Users Score":1,"Answer":"Assuming I understand you question correctly, then No, you can't model that relationship as you have suggested.  (It would help if you described your desired result, rather than your perceived solution)\nWhat I think you may want is a many-to-many mapping table called ArticleCategories, consisting of 2 int columns, ArticleID and CategoryID (with respective FKs)","Q_Score":0,"Tags":"python,sqlalchemy","A_Id":2248806,"CreationDate":"2010-02-10T02:30:00.000","Title":"SQLAlchemy ForeignKey relation via an intermediate table","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"My Django app, deployed in mod_wsgi under Apache using Django's standard WSGIHandler, authenticates users via form login on the Django side. So to Apache, the user is anonymous. This makes the Apache access log less useful.\nIs there a way to pass the username back through the WSGI wrapper to Apache after handling the request, so that it appears in the Apache access log?\n(Versions: Django 1.1.1, mod_wsgi 2.5, Apache 2.2.9)","AnswerCount":5,"Available Count":2,"Score":0.0399786803,"is_accepted":false,"ViewCount":2209,"Q_Id":2244244,"Users Score":1,"Answer":"This probably isn't what you're expecting, but you could use the username in your URL scheme. That way the user will be in the path section of your apache logs.\nYou'd need to modify your authentication so that auth-required responses are obvious in the apache logs, otherwise when viewing the logs you may attribute unauthenticated requests to authenticated users. E.g. return a temporary redirect to the login page if the request isn't authenticated.","Q_Score":9,"Tags":"python,django,apache,authentication,mod-wsgi","A_Id":2244295,"CreationDate":"2010-02-11T12:03:00.000","Title":"WSGI\/Django: pass username back to Apache for access log","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"My Django app, deployed in mod_wsgi under Apache using Django's standard WSGIHandler, authenticates users via form login on the Django side. So to Apache, the user is anonymous. This makes the Apache access log less useful.\nIs there a way to pass the username back through the WSGI wrapper to Apache after handling the request, so that it appears in the Apache access log?\n(Versions: Django 1.1.1, mod_wsgi 2.5, Apache 2.2.9)","AnswerCount":5,"Available Count":2,"Score":0.0399786803,"is_accepted":false,"ViewCount":2209,"Q_Id":2244244,"Users Score":1,"Answer":"Correct me if I'm wrong, but what's stopping you from creating some custom middleware that sets a cookie equal to the display name of the current user logged in. This middleware will run on every view, so even though technically the user could spoof his username to display whatever he wants it to display, it'll just be reset anyway and it's not like its a security risk because the username itself is just for log purposes, not at all related to the actual user logged in. This seems like a simple enough solution, and then Apache log can access cookies so that gives you easiest access. I know some people wouldn't like the idea of a given user spoofing his own username, but i think this is the most trivial solution that gets the job done. Especially, in my case, when it's an iPhone app and the user doesn't have any direct access to a javascript console or the cookies itself.","Q_Score":9,"Tags":"python,django,apache,authentication,mod-wsgi","A_Id":10406967,"CreationDate":"2010-02-11T12:03:00.000","Title":"WSGI\/Django: pass username back to Apache for access log","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am using PostgreSQL 8.4. I really like the new unnest() and array_agg() features; it is about time they realize the dynamic processing potential of their Arrays!\nAnyway, I am working on web server back ends that uses long Arrays a lot. Their will be two successive processes which will each occur on a different physical machine. Each such process is a light python application which ''manage'' SQL queries to the database on each of their machines as well as requests from the front ends. \nThe first process will generate an Array which will be buffered into an SQL Table. Each such generated Array is accessible via a Primary Key. When its done the first python app sends the key to the second python app. Then the second python app, which is running on a different machine, uses it to go get the referenced Array found in the first machine. It then sends it to it's own db for generating a final result.\nThe reason why I send a key is because I am hopping that this will make the two processes go faster. But really what I would like is for a way to have the second database send a query to the first database in the hope of minimizing serialization delay and such.\nAny help\/advice would be appreciated.\nThanks","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":785,"Q_Id":2263132,"Users Score":0,"Answer":"I am thinking either listen\/notify or something with a cache such as memcache. You would send the key to memcache and have the second python app retrieve it from there. You could even do it with listen\/notify... e.g; send the key and notify your second app that the key is in memcache waiting to be retrieved.","Q_Score":3,"Tags":"python,arrays,postgresql,database-connection","A_Id":2277362,"CreationDate":"2010-02-14T22:40:00.000","Title":"Inter-database communications in PostgreSQL","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am developing some Python modules that use a mysql database to insert some data and produce various types of report. I'm doing test driven development and so far I run:\n\nsome CREATE \/ UPDATE \/ DELETE tests against a temporary database that is thrown away at the end of each test case, and \nsome report generation tests doing exclusively read only operations, mainly SELECT, against a copy of the production database, written on the (valid, in this case) assumption that some things in my database aren't going to change.\n\nSome of the SELECT operations are running slow, so that my tests are taking more than 30 seconds, which spoils the flow of test driven development. I can see two choices:\n\nonly put a small fraction of my data into the copy of the production database that I use for testing the report generation so that the tests go fast enough for test driven development (less than about 3 seconds suits me best), or I can regard the tests as failures. I'd then need to do separate performance testing.\nfill the production database copy with as much data as the main test database, and add timing code that fails a test if it is taking too long.\n\nI'm not sure which approach to take. Any advice?","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":107,"Q_Id":2273414,"Users Score":1,"Answer":"I'd do both. Run against the small set first to make sure all the code works, then run against the large dataset for things which need to be tested for time, this would be selects, searches and reports especially. If you are doing inserts or deletes or updates on multiple row sets, I'd test those as well against the large set. It is unlikely that simple single row action queries will take too long, but if they involve a lot alot of joins, I'd test them as well. If the queries won't run on prod within the timeout limits, that's a fail and far, far better to know as soon as possible so you can fix before you bring prod to it's knees.","Q_Score":1,"Tags":"python,sql,mysql,tdd,automated-tests","A_Id":2273471,"CreationDate":"2010-02-16T14:06:00.000","Title":"Should pre-commit tests use a big data set and fail if queries take too long, or use a small test database?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am developing some Python modules that use a mysql database to insert some data and produce various types of report. I'm doing test driven development and so far I run:\n\nsome CREATE \/ UPDATE \/ DELETE tests against a temporary database that is thrown away at the end of each test case, and \nsome report generation tests doing exclusively read only operations, mainly SELECT, against a copy of the production database, written on the (valid, in this case) assumption that some things in my database aren't going to change.\n\nSome of the SELECT operations are running slow, so that my tests are taking more than 30 seconds, which spoils the flow of test driven development. I can see two choices:\n\nonly put a small fraction of my data into the copy of the production database that I use for testing the report generation so that the tests go fast enough for test driven development (less than about 3 seconds suits me best), or I can regard the tests as failures. I'd then need to do separate performance testing.\nfill the production database copy with as much data as the main test database, and add timing code that fails a test if it is taking too long.\n\nI'm not sure which approach to take. Any advice?","AnswerCount":2,"Available Count":2,"Score":0.0996679946,"is_accepted":false,"ViewCount":107,"Q_Id":2273414,"Users Score":1,"Answer":"The problem with testing against real data is that it contains lots of duplicate values, and not enough edge cases.   It is also difficult to know what the expected values ought to be (especially if your live database is very big).  Oh, and depending on what the live application does, it can be illegal to use the data for the purposes of testing or development. \nGenerally the best thing is to write the test data to go with the tests.  This is labourious and boring, which is why so many TDD practitioners abhor databases.  But if you have a live data set (which you can use for testing) then take a very cut-down sub-set of data for your tests.  If you can write valid assertions against a dataset of thirty records, running your tests against a data set of thirty thousand is just a waste of time.\nBut definitely, once you have got the queries returning the correct results put the queries through some performance tests.","Q_Score":1,"Tags":"python,sql,mysql,tdd,automated-tests","A_Id":2273476,"CreationDate":"2010-02-16T14:06:00.000","Title":"Should pre-commit tests use a big data set and fail if queries take too long, or use a small test database?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm going to write my first non-Access project, and I need advice on choosing the platform. I will be installing it on multiple friends' and family's computers, so (since I'm sure many, many platforms would suffice just fine for my app), my highest priority has two parts: 1) ease of install for the non-technical user and, 2) minimizing compatibility problems.  I want to be able to fix bugs and make changes and roll them out without having to troubleshoot OS and program conflicts on their computers (or at least keeping those things to the absolute minimum-this is why these concerns are my highest priority in choosing a platform.)\nI have narrowed it down to Python or Java.  I like Java's use of the JVM, which seems like would serve to protect against incompatibilities on individual computers nicely.  And I've heard a lot of good things about Python, but I don't know how much more prone to incompatibilities it is vs Java.   In case it is important, I know the app will definitely use some flavor of a free server-enabled SQL db (server-enabled because I want to be able to run the app from multiple computers), but I don't know which to use yet.  I thought I could decide that next.\nMy experience level: I've taken a C++ (console app only) class and done some VBA in Access, but mostly I'm going to have to jump in and learn as I go.  So of course I don't know much about all of this.  I'm not in the computer field, this is just a hobby.\nSo, which would be better for this app, Java or Python?  \n(In case it comes up, I don't want to make it browser-based at all.  I've dealt with individual computers' browser settings breaking programs, and that goes against part 2 of my top priority - maximum compatibility.)\nThank you.\nUpdate: It will need a gui, and I'd like to be able to do a little bit of customization on it (or use a non-standard, or maybe a non-built-in one) to make it pop a little.\nUpdate 2: Truthfully, I really am only concerned with Windows computers.  I am considering Java only for its reliability as a platform.","AnswerCount":5,"Available Count":2,"Score":0.0399786803,"is_accepted":false,"ViewCount":594,"Q_Id":2282360,"Users Score":1,"Answer":"The largest issue I can think of is the need to install an interpreter.\nWith Java, a lot of people will already have that interpreter installed, although you won't necessarily know which version.  It may be wise to include the installer for Java with the program.\nWith Python, you're going to have to install the interpreter on each computer, too.\nOne commenter mentioned .NET.  .NET 2.0 has a fairly high likelyhood of being installed than either Java or Python on Windows machines.  The catch is that you can't (easily) install it on OSX or Linux.","Q_Score":0,"Tags":"java,python","A_Id":2282470,"CreationDate":"2010-02-17T16:20:00.000","Title":"Help for novice choosing between Java and Python for app with sql db","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm going to write my first non-Access project, and I need advice on choosing the platform. I will be installing it on multiple friends' and family's computers, so (since I'm sure many, many platforms would suffice just fine for my app), my highest priority has two parts: 1) ease of install for the non-technical user and, 2) minimizing compatibility problems.  I want to be able to fix bugs and make changes and roll them out without having to troubleshoot OS and program conflicts on their computers (or at least keeping those things to the absolute minimum-this is why these concerns are my highest priority in choosing a platform.)\nI have narrowed it down to Python or Java.  I like Java's use of the JVM, which seems like would serve to protect against incompatibilities on individual computers nicely.  And I've heard a lot of good things about Python, but I don't know how much more prone to incompatibilities it is vs Java.   In case it is important, I know the app will definitely use some flavor of a free server-enabled SQL db (server-enabled because I want to be able to run the app from multiple computers), but I don't know which to use yet.  I thought I could decide that next.\nMy experience level: I've taken a C++ (console app only) class and done some VBA in Access, but mostly I'm going to have to jump in and learn as I go.  So of course I don't know much about all of this.  I'm not in the computer field, this is just a hobby.\nSo, which would be better for this app, Java or Python?  \n(In case it comes up, I don't want to make it browser-based at all.  I've dealt with individual computers' browser settings breaking programs, and that goes against part 2 of my top priority - maximum compatibility.)\nThank you.\nUpdate: It will need a gui, and I'd like to be able to do a little bit of customization on it (or use a non-standard, or maybe a non-built-in one) to make it pop a little.\nUpdate 2: Truthfully, I really am only concerned with Windows computers.  I am considering Java only for its reliability as a platform.","AnswerCount":5,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":594,"Q_Id":2282360,"Users Score":1,"Answer":"If you're going to install only (or mostly) on Windows, I'd go with .Net. \nIf you have experience with C++, then C# would be natural to you, but if you're comfortable with VBA, you can try VB.NET, but if you prefer Python, then there is IronPython or can give a try to IronRuby, but the best of all is you can mix them all as they apply to different parts of your project.\nIn the database area you'll have excellent integration with SQL Server Express, and in the GUI area, Swing can't beat the ease of use of WinForms nor the sophistication of WPF\/Silverlight.\nAs an added bonus, you can have your application automatically updated with ClickOnce.","Q_Score":0,"Tags":"java,python","A_Id":2283347,"CreationDate":"2010-02-17T16:20:00.000","Title":"Help for novice choosing between Java and Python for app with sql db","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"How do I completely reset my Django (1.2 alpha) DB (dropping all tables, rather than just clearing them)?\nmanage.py flush does too little (won't work if there are schema changes) and manage.py reset requires me to specify all apps (and appears to take a format that is different from just \" \".join(INSTALLED_APPS)). I can obviously achieve this in a DB specific way, but I figured there must be a sane, DB backend agnostic way to do this.\n[Edit: I'm looking for something that I can call from a script, e.g. a Makefile and that continues to work if I change the backend DB or add to settings.INSTALLED_APPS]","AnswerCount":7,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":24412,"Q_Id":2289187,"Users Score":0,"Answer":"Hm, maybe you lie to manage.py, pretending to make fixtures, but only to look for apps:\n\napps=$(python manage.py makefixture 2>&1 | egrep -v '(^Error|^django)'|awk -F . '{print $2}'|uniq); for i in $apps; do python manage.py sqlreset $i; done| grep DROP\n\nThat prints out a list of DROP TABLE statements for all apps tables of your project, excluding django tables itself. If you want to include them, remove the |^django pattern vom egrep.\nBut how to feed the correct database backend? sed\/awk-ing through settings.conf? Or better by utilizing a little settings.conf-reading python script itself.","Q_Score":20,"Tags":"python,django","A_Id":2289931,"CreationDate":"2010-02-18T14:16:00.000","Title":"Complete django DB reset","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"How do I completely reset my Django (1.2 alpha) DB (dropping all tables, rather than just clearing them)?\nmanage.py flush does too little (won't work if there are schema changes) and manage.py reset requires me to specify all apps (and appears to take a format that is different from just \" \".join(INSTALLED_APPS)). I can obviously achieve this in a DB specific way, but I figured there must be a sane, DB backend agnostic way to do this.\n[Edit: I'm looking for something that I can call from a script, e.g. a Makefile and that continues to work if I change the backend DB or add to settings.INSTALLED_APPS]","AnswerCount":7,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":24412,"Q_Id":2289187,"Users Score":0,"Answer":"Just assign a new database and drop this db from the db console. Seems to me to be the simplest.","Q_Score":20,"Tags":"python,django","A_Id":2289445,"CreationDate":"2010-02-18T14:16:00.000","Title":"Complete django DB reset","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"How do I completely reset my Django (1.2 alpha) DB (dropping all tables, rather than just clearing them)?\nmanage.py flush does too little (won't work if there are schema changes) and manage.py reset requires me to specify all apps (and appears to take a format that is different from just \" \".join(INSTALLED_APPS)). I can obviously achieve this in a DB specific way, but I figured there must be a sane, DB backend agnostic way to do this.\n[Edit: I'm looking for something that I can call from a script, e.g. a Makefile and that continues to work if I change the backend DB or add to settings.INSTALLED_APPS]","AnswerCount":7,"Available Count":3,"Score":-0.057080742,"is_accepted":false,"ViewCount":24412,"Q_Id":2289187,"Users Score":-2,"Answer":"take a look at reset command in django's code, and write your own which drops\/creates DB first.","Q_Score":20,"Tags":"python,django","A_Id":2289727,"CreationDate":"2010-02-18T14:16:00.000","Title":"Complete django DB reset","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"i'm using Python with MySQL and Django.  I keep seeing this error and I can't figure out where the exception is being thrown:\n\nException _mysql_exceptions.ProgrammingError: (2014, \"Commands out of sync; you can't run this command now\") in <bound method Cursor.__del__ of <MySQLdb.cursors.Cursor object at 0x20108150>> ignored\n\nI have many \"try\" and \"exception\" blocks in my code--if the exception occurred within one of those, then I would see my own debugging messages.  The above Exception is obviously being caught somewhere since my program does not abort when the Exception is thrown.\nI'm very puzzled, can someone help me out?","AnswerCount":5,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":6125,"Q_Id":2291714,"Users Score":0,"Answer":"The exceptions in object destructors (__del__) are ignored, which this message indicates. If you execute some MySQL command without fetching results from the cursor (e.g. 'create procedure' or 'insert') then the exception is unnoticed until the cursor is destroyed.\nIf you want to raise and catch an exception, call explicitly cursor.close() somewhere before going out of the scope.","Q_Score":8,"Tags":"python,mysql,django,exception","A_Id":55394190,"CreationDate":"2010-02-18T19:50:00.000","Title":"Who is throwing (and catching) this MySQL Exception?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"i'm using Python with MySQL and Django.  I keep seeing this error and I can't figure out where the exception is being thrown:\n\nException _mysql_exceptions.ProgrammingError: (2014, \"Commands out of sync; you can't run this command now\") in <bound method Cursor.__del__ of <MySQLdb.cursors.Cursor object at 0x20108150>> ignored\n\nI have many \"try\" and \"exception\" blocks in my code--if the exception occurred within one of those, then I would see my own debugging messages.  The above Exception is obviously being caught somewhere since my program does not abort when the Exception is thrown.\nI'm very puzzled, can someone help me out?","AnswerCount":5,"Available Count":3,"Score":0.0798297691,"is_accepted":false,"ViewCount":6125,"Q_Id":2291714,"Users Score":2,"Answer":"After printing out a bunch of stuff and debugging, I figured out the problem I think.  One of the libraries that I used didn't close the connection or the cursor.  But this problem only shows up if I iterate through a large amount of data.  The problem is also very intermittent and I still don't know who's throwing the \"command out of sync\" exception.  But now that we closed both the connection and cursor, I don't see the errors anymore.","Q_Score":8,"Tags":"python,mysql,django,exception","A_Id":2300154,"CreationDate":"2010-02-18T19:50:00.000","Title":"Who is throwing (and catching) this MySQL Exception?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"i'm using Python with MySQL and Django.  I keep seeing this error and I can't figure out where the exception is being thrown:\n\nException _mysql_exceptions.ProgrammingError: (2014, \"Commands out of sync; you can't run this command now\") in <bound method Cursor.__del__ of <MySQLdb.cursors.Cursor object at 0x20108150>> ignored\n\nI have many \"try\" and \"exception\" blocks in my code--if the exception occurred within one of those, then I would see my own debugging messages.  The above Exception is obviously being caught somewhere since my program does not abort when the Exception is thrown.\nI'm very puzzled, can someone help me out?","AnswerCount":5,"Available Count":3,"Score":0.0798297691,"is_accepted":false,"ViewCount":6125,"Q_Id":2291714,"Users Score":2,"Answer":"I believe this error can occur if you are using the same connection\/cursor from multiple threads. \nHowever, I dont think the creators of Django has made such a mistake, but if you are doing something by yourself it can easily happen.","Q_Score":8,"Tags":"python,mysql,django,exception","A_Id":2292145,"CreationDate":"2010-02-18T19:50:00.000","Title":"Who is throwing (and catching) this MySQL Exception?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm planning on building a Django log-viewing app with powerful filters. I'd like to enable the user to finely filter the results with some custom (possibly DB-specific) SELECT queries.\nHowever, I dislike giving the user write access to the database. Is there a way to make sure a query doesn't change anything in the database? Like a 'dry run' flag? Or is there a way to filter SELECT queries so that they can't be harmful in any way?\nI thought about running the queries as a separate MySQL user but I'd rather avoid the hassle. I also thought about using Google App Engine's GQL 'language', but if there is a cleaner solution, I'd certainly like to hear it :)\nThanks.","AnswerCount":2,"Available Count":2,"Score":0.0996679946,"is_accepted":false,"ViewCount":543,"Q_Id":2305353,"Users Score":1,"Answer":"Create and use non-modifiable views.","Q_Score":2,"Tags":"python,sql,django,security,sql-injection","A_Id":2305359,"CreationDate":"2010-02-21T08:48:00.000","Title":"How can I limit an SQL query to be nondestructive?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm planning on building a Django log-viewing app with powerful filters. I'd like to enable the user to finely filter the results with some custom (possibly DB-specific) SELECT queries.\nHowever, I dislike giving the user write access to the database. Is there a way to make sure a query doesn't change anything in the database? Like a 'dry run' flag? Or is there a way to filter SELECT queries so that they can't be harmful in any way?\nI thought about running the queries as a separate MySQL user but I'd rather avoid the hassle. I also thought about using Google App Engine's GQL 'language', but if there is a cleaner solution, I'd certainly like to hear it :)\nThanks.","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":543,"Q_Id":2305353,"Users Score":14,"Answer":"Connect with a user that has only been granted SELECT permissions. Situations like this is why permissions exist in the first place.","Q_Score":2,"Tags":"python,sql,django,security,sql-injection","A_Id":2305379,"CreationDate":"2010-02-21T08:48:00.000","Title":"How can I limit an SQL query to be nondestructive?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Quick question: is it a good idea to use sqlite while developing a Django project, and use MySQL on the production server?","AnswerCount":6,"Available Count":4,"Score":1.2,"is_accepted":true,"ViewCount":4303,"Q_Id":2306048,"Users Score":24,"Answer":"I'd highly recommend using the same database backend in production as in development, and all stages in between. Django will abstract the database stuff, but having different environments will leave you open to horrible internationalisation, configuration issues, and nasty tiny inconsistencies that won't even show up until you push it live.\nPersonally, I'd stick to mysql, but I never got on with postgres :)","Q_Score":20,"Tags":"python,mysql,django,sqlite,dev-to-production","A_Id":2306070,"CreationDate":"2010-02-21T13:45:00.000","Title":"Django: sqlite for dev, mysql for prod?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Quick question: is it a good idea to use sqlite while developing a Django project, and use MySQL on the production server?","AnswerCount":6,"Available Count":4,"Score":1.0,"is_accepted":false,"ViewCount":4303,"Q_Id":2306048,"Users Score":7,"Answer":"Use the same database in all environments.\nAs much as the ORM tries to abstract the differences between databases, there will always be certain features that behave differently based on the database.  Database portability is a complete myth.\nPlus, it seems pretty insane to test and develop against code paths that you will never use in production, doesn't it?","Q_Score":20,"Tags":"python,mysql,django,sqlite,dev-to-production","A_Id":9401789,"CreationDate":"2010-02-21T13:45:00.000","Title":"Django: sqlite for dev, mysql for prod?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Quick question: is it a good idea to use sqlite while developing a Django project, and use MySQL on the production server?","AnswerCount":6,"Available Count":4,"Score":0.0996679946,"is_accepted":false,"ViewCount":4303,"Q_Id":2306048,"Users Score":3,"Answer":"In short, no; unless you want to unnecessarily double development time.","Q_Score":20,"Tags":"python,mysql,django,sqlite,dev-to-production","A_Id":2306069,"CreationDate":"2010-02-21T13:45:00.000","Title":"Django: sqlite for dev, mysql for prod?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Quick question: is it a good idea to use sqlite while developing a Django project, and use MySQL on the production server?","AnswerCount":6,"Available Count":4,"Score":0.0996679946,"is_accepted":false,"ViewCount":4303,"Q_Id":2306048,"Users Score":3,"Answer":"Just made this major mistake starting off with sqlite and when i try to deploy on production server with mysql, things didn't work as smooth as i expected. I tried dumpdata\/loaddata with various switches but somehow keep getting errors thrown one after another. Do yourself a big favor and use the same db for both production and development.","Q_Score":20,"Tags":"python,mysql,django,sqlite,dev-to-production","A_Id":12684980,"CreationDate":"2010-02-21T13:45:00.000","Title":"Django: sqlite for dev, mysql for prod?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Is there another way to connect to a MySQL database with what came included in the version of  Python (2.5.1) that is bundled with Mac OS 10.5.x? I unfortunately cannot add the the MySQLdb module to the client machines I am working with...I need to work with the stock version of Python that shipped with Leopard.","AnswerCount":4,"Available Count":1,"Score":0.049958375,"is_accepted":false,"ViewCount":3698,"Q_Id":2313307,"Users Score":1,"Answer":"If the problem is the inability, as so many people have mentioned, that the msqldb module is a problem a simpler way is\n1. install the mysql db\n2. install the pyodbc module\n3. Load and configure the odbc mysql driver\n4. perform sql manipulations with pyodbc, which is very mature and full functional.\nhope this helps","Q_Score":3,"Tags":"python,mysql,macos","A_Id":9170459,"CreationDate":"2010-02-22T18:54:00.000","Title":"Python: Access a MySQL db without MySQLdb module","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"What is the best way to access sql server from python is it DB-API ?\nAlso could someone provide a such code using the DB-API how to connect to sql server from python and excute query ?","AnswerCount":4,"Available Count":1,"Score":0.049958375,"is_accepted":false,"ViewCount":28195,"Q_Id":2314178,"Users Score":1,"Answer":"ODBC + freetds + a python wrapper library for ODBC.","Q_Score":26,"Tags":"python,sql,sql-server","A_Id":2314282,"CreationDate":"2010-02-22T21:04:00.000","Title":"Python & sql server","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm seeking a way to let the python logger module to log to database and falls back to file system when the db is down.\nSo basically 2 things: How to let the logger log to database and how to make it fall to file logging when the db is down.","AnswerCount":5,"Available Count":1,"Score":0.0798297691,"is_accepted":false,"ViewCount":48780,"Q_Id":2314307,"Users Score":2,"Answer":"Old question, but dropping this for others. If you want to use python logging, you can add two handlers. One for writing to file, a rotating file handler. This is robust, and can be done regardless if the dB is up or not. \nThe other one can write to another service\/module, like a pymongo integration. \nLook up logging.config on how to setup your handlers from code or json.","Q_Score":48,"Tags":"python,database,logging","A_Id":46617613,"CreationDate":"2010-02-22T21:22:00.000","Title":"python logging to database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am developing a Python web app using sqlalchemy to communicate with mysql database. So far I have mostly been using sqlalchemy's ORM layer to speak with the database. The greatest benefit to me of ORM has been the speed of development, not having to write all these sql queries and then map them to models.\nRecently, however, I've been required to change my design to communicate with the database through stored procedures. Does any one know if there is any way to use sqlalchemy ORM layer to work with my models through the stored procedures? Is there another Python library which would allow me to do this?\nThe way I see it I should be able to write my own select, insert, update and delete statements, attach them to the model and let the library do the rest. I've gone through sqlalchemy's documentation multiple times but can't seem to find a way to do this.\nAny help with this would be great!","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1754,"Q_Id":2330278,"Users Score":3,"Answer":"SQLAlchemy doesn't have any good way to convert inserts, updates and deletes to stored procedure calls. It probably wouldn't be that hard to add the capability to have instead_{update,insert,delete} extensions on mappers, but no one has bothered yet. I consider the requirement to have simple DML statements go through stored procedures rather silly. It really doesn't offer anything that you couldn't do with triggers.\nIf you can't avoid the silliness, there are some ways that you can use SQLAlchemy to go along with it. You'll lose some of the ORM functionality though. You can build ORM objects from stored procedure results using query(Obj).from_statement(text(\"...\")), just have the column labels in the statement match the column names that you told SQLAlchemy to map.\nOne option to cope with DML statements is to turn autoflush off and instead of flushing go through the sessions .new, .dirty and .deleted attributes to see what has changed, issue corresponding statements as stored procedure calls and expunge the objects before committing. \nOr you can just forgo SQLAlchemy state tracking and issue the stored procedure calls directly.","Q_Score":4,"Tags":"python,mysql,database,stored-procedures,sqlalchemy","A_Id":2338360,"CreationDate":"2010-02-24T22:51:00.000","Title":"Keeping ORM with stored procedures","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Here is the scenario.  In your function you're executing statements using a cursor, but one of them fails and an exception is thrown.  Your program exits out of the function before closing the cursor it was working with.  Will the cursor float around taking up space?  Do I have to close the cursor?\nAdditionally, the Python documentation has an example of cursor use and says: \"We can also close the cursor if we are done with it.\"  The keyword being \"can,\" not \"must.\"  What do they mean precisely by this?","AnswerCount":8,"Available Count":3,"Score":1.0,"is_accepted":false,"ViewCount":27863,"Q_Id":2330344,"Users Score":13,"Answer":"You're not obliged to call close() on the cursor; it can be garbage collected like any other object.\nBut even if waiting for garbage collection sounds OK, I think it would be good style still to ensure that a resource such as a database cursor gets closed whether or not there is an exception.","Q_Score":48,"Tags":"python,sqlite","A_Id":2330380,"CreationDate":"2010-02-24T23:02:00.000","Title":"In Python with sqlite is it necessary to close a cursor?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Here is the scenario.  In your function you're executing statements using a cursor, but one of them fails and an exception is thrown.  Your program exits out of the function before closing the cursor it was working with.  Will the cursor float around taking up space?  Do I have to close the cursor?\nAdditionally, the Python documentation has an example of cursor use and says: \"We can also close the cursor if we are done with it.\"  The keyword being \"can,\" not \"must.\"  What do they mean precisely by this?","AnswerCount":8,"Available Count":3,"Score":1.0,"is_accepted":false,"ViewCount":27863,"Q_Id":2330344,"Users Score":7,"Answer":"I haven't seen any effect for the sqlite3.Cursor.close() operation yet. \nAfter closing, you can still call fetch(all|one|many) which will return the remaining results from the previous execute statement. Even running Cursor.execute() still works ...","Q_Score":48,"Tags":"python,sqlite","A_Id":2416354,"CreationDate":"2010-02-24T23:02:00.000","Title":"In Python with sqlite is it necessary to close a cursor?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Here is the scenario.  In your function you're executing statements using a cursor, but one of them fails and an exception is thrown.  Your program exits out of the function before closing the cursor it was working with.  Will the cursor float around taking up space?  Do I have to close the cursor?\nAdditionally, the Python documentation has an example of cursor use and says: \"We can also close the cursor if we are done with it.\"  The keyword being \"can,\" not \"must.\"  What do they mean precisely by this?","AnswerCount":8,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":27863,"Q_Id":2330344,"Users Score":0,"Answer":"Yes, we should close our cursor. I once encountered an error when I used my cursor to configure my connection object: 'PRAGMA synchronous=off' and 'PRAGMA journal_mode=off' for faster insertion. Once I closed the cursor, the error went away. I forgot what type of error I encountered.","Q_Score":48,"Tags":"python,sqlite","A_Id":71683829,"CreationDate":"2010-02-24T23:02:00.000","Title":"In Python with sqlite is it necessary to close a cursor?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm writing a python script to select, insert, update, and delete data in SimpleDB.\nI've been using the simpledb module written by sixapart so far, and it's working pretty well.\nI've found one potential bug\/feature that is problematic for me when running select queries with \"limit\", and I'm thinking of trying it with the boto module to see if it works better.\nHas anyone used these two modules? Care to offer an opinion on which is better?\nThanks!","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":833,"Q_Id":2336822,"Users Score":3,"Answer":"I've found boto to be effective and straight forward and I've never had any trouble with queries with limits. Although I've never used the sixapart module.","Q_Score":4,"Tags":"python,amazon-simpledb","A_Id":2336902,"CreationDate":"2010-02-25T19:10:00.000","Title":"What's the best module to access SimpleDB in python?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"SQLAlchemy seems really heavyweight if all I use is MySQL.\nWhy are convincing reasons for\/against the use of SQLAlchemy in an application that only uses MySQL.","AnswerCount":3,"Available Count":3,"Score":0.2605204458,"is_accepted":false,"ViewCount":275,"Q_Id":2358822,"Users Score":4,"Answer":"I don't think performance should be much of a factor in your choice. The layer that an ORM adds will be insignificant compared to the speed of the database. Databases always end up being a bottleneck.\nUsing an ORM may allow you to develop faster with less bugs. You can still access the DB directly if you have a query that doesn't work well with the ORM layer.","Q_Score":3,"Tags":"python,mysql,sqlalchemy,pylons","A_Id":2359697,"CreationDate":"2010-03-01T20:24:00.000","Title":"If I'm only planning to use MySQL, and if speed is a priority, is there any convincing reason to use SQLAlchemy?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"SQLAlchemy seems really heavyweight if all I use is MySQL.\nWhy are convincing reasons for\/against the use of SQLAlchemy in an application that only uses MySQL.","AnswerCount":3,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":275,"Q_Id":2358822,"Users Score":0,"Answer":"sqlalchemy provides more than just an orm, you can select\/insert\/update\/delete from table objects, join them etc.... the benefit of using those things over building strings with sql in them is guarding against sql injection attacks for one. You also get some decent connection management that you don't have to write yourself. \nThe orm part may not be appropriate for your application, but rolling your own sql handling and connection handling would be really really stupid in my opinion.","Q_Score":3,"Tags":"python,mysql,sqlalchemy,pylons","A_Id":2359777,"CreationDate":"2010-03-01T20:24:00.000","Title":"If I'm only planning to use MySQL, and if speed is a priority, is there any convincing reason to use SQLAlchemy?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"SQLAlchemy seems really heavyweight if all I use is MySQL.\nWhy are convincing reasons for\/against the use of SQLAlchemy in an application that only uses MySQL.","AnswerCount":3,"Available Count":3,"Score":1.2,"is_accepted":true,"ViewCount":275,"Q_Id":2358822,"Users Score":7,"Answer":"ORM means that your OO application actually makes sense when interpreted as the interaction of objects.\nNo ORM means that you must wallow in the impedance mismatch between SQL and Objects.  Working without an ORM means lots of redundant code to map between SQL query result sets, individual SQL statements and objects.  \nSQLAchemy partitions your application cleanly into objects that interact and a persistence mechanism that (today) happens to be a relational database.  \nWith SQLAlchemy you stand a fighting chance of separating the core model and processing from the odd limitations and quirks of a SQL RDBMS.","Q_Score":3,"Tags":"python,mysql,sqlalchemy,pylons","A_Id":2358852,"CreationDate":"2010-03-01T20:24:00.000","Title":"If I'm only planning to use MySQL, and if speed is a priority, is there any convincing reason to use SQLAlchemy?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I\u2019m trying to bulk insert data to SQL server express database. When doing bcp from Windows XP command prompt, I get the following error:\nC:\\temp>bcp  in  -T -f  -S \n\nStarting copy...\nSQLState = S1000, NativeError = 0\nError = [Microsoft][SQL Native Client]Unexpected EOF encountered in BCP data-file\n\n0 rows copied.\nNetwork packet size (bytes): 4096\nClock Time (ms.) Total     : 4391\nSo, there is a problem with EOF. How to append a correct EOF character to this file using Perl or Python?","AnswerCount":3,"Available Count":2,"Score":0.0665680765,"is_accepted":false,"ViewCount":3283,"Q_Id":2371645,"Users Score":1,"Answer":"This is not a problem with missing EOF, but with EOF that is there and is not expected by bcp.\nI am not a bcp tool expert, but it looks like there is some problem with format of your data files.","Q_Score":0,"Tags":"python,sql-server,perl,bcp","A_Id":2371680,"CreationDate":"2010-03-03T13:35:00.000","Title":"How to append EOF to file using Perl or Python?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":0},{"Question":"I\u2019m trying to bulk insert data to SQL server express database. When doing bcp from Windows XP command prompt, I get the following error:\nC:\\temp>bcp  in  -T -f  -S \n\nStarting copy...\nSQLState = S1000, NativeError = 0\nError = [Microsoft][SQL Native Client]Unexpected EOF encountered in BCP data-file\n\n0 rows copied.\nNetwork packet size (bytes): 4096\nClock Time (ms.) Total     : 4391\nSo, there is a problem with EOF. How to append a correct EOF character to this file using Perl or Python?","AnswerCount":3,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":3283,"Q_Id":2371645,"Users Score":3,"Answer":"EOF is End Of File. What probably occurred is that the file is not complete; the software expects data, but there is none to be had anymore.\nThese kinds of things happen when:\n\nthe export is interrupted (quit dump software while dumping)\nwhile copying the dumpfile aborting the copy\ndisk full during dump\n\nthese kinds of things. \nBy the way, though EOF is usually just an end of file, there does exist an EOF character. This is used because terminal (command line) input doesn't really end like a file does, but it sometimes is necessary to pass an EOF to such a utility. I don't think it's used in real files, at least not to indicate an end of file. The file system knows perfectly well when the file has ended, it doesn't need an indicator to find that out.\nEDIT shamelessly copied from a comment provided by  John Machin\nIt can happen (uninentionally) in real files. All it needs is (1) a data-entry user to type Ctrl-Z by mistake, see nothing on the screen, type the intended Shift-Z, and keep going and (2) validation software (written by e.g. the company president's nephew) which happily accepts Ctrl-anykey in text fields and your database has a little bomb in it, just waiting for someone to produce a query to a flat file.","Q_Score":0,"Tags":"python,sql-server,perl,bcp","A_Id":2371725,"CreationDate":"2010-03-03T13:35:00.000","Title":"How to append EOF to file using Perl or Python?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":0},{"Question":"I have a big DBF file (~700MB). I'd like to select only a few lines from it using a python script. I've seen that dbfpy is a nice module that allows to open this type of database, but for now I haven't found any querying capability. Iterating through all the elements from python is simply too slow.\nCan I do what I want from python in a reasonable time?","AnswerCount":3,"Available Count":1,"Score":0.1325487884,"is_accepted":false,"ViewCount":5441,"Q_Id":2373086,"Users Score":2,"Answer":"Chances are, your performance is more I\/O bound than CPU bound. As such, the best way to speed it up is to optimize your search. You probably want to build some kind of index keyed by whatever your search predicate is.","Q_Score":9,"Tags":"python,performance,python-3.x,dbf,xbase","A_Id":2375874,"CreationDate":"2010-03-03T16:38:00.000","Title":"Python: Fast querying in a big dbf (xbase) file","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am able to get the feed from the spreadsheet and worksheet ID. I want to capture the data from each cell. \ni.e, I am able to get the feed from the worksheet. Now I need to get data(string type?) from each of the cells to make a comparison and for input. \nHow exactly can I do that?","AnswerCount":5,"Available Count":1,"Score":0.0399786803,"is_accepted":false,"ViewCount":14275,"Q_Id":2377301,"Users Score":1,"Answer":"gspread is probably the fastest way to begin this process, however there are some speed limitations on updating data using gspread from your localhost. If you're moving large sets of data with gspread - for instance moving 20 columns of data over a column, you may want to automate the process using a CRON job.","Q_Score":6,"Tags":"python,google-sheets,gspread","A_Id":22048019,"CreationDate":"2010-03-04T06:32:00.000","Title":"How to write a python script to manipulate google spreadsheet data","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"1.I have a list of data and a sqlite DB filled with past data along with some stats on each data. I have to do the following operations with them.\n\nCheck if each item in the list is present in DB. if no then collect some stats on the new item and add them to DB.\nCheck if each item in DB is in the list. if no delete it from DB.\n\nI cannot just create a new DB, coz I have other processing to do on the new items and the missing items.\nIn short, i have to update the DB with the new data in list. What is best way to do it? \n2.I had to use sqlite with python threads. So I put a lock for every DB read and write operation. Now it has slowed down the DB access. What is the overhead for thread lock operation? And Is there any other way to use the DB with multiple threads?\nCan someone help me on this?I am using python3.1.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":227,"Q_Id":2378364,"Users Score":0,"Answer":"It does not need to check anything, just use INSERT OR IGNORE in first case (just make sure you have corresponding unique fields so INSERT would not create duplicates) and DELETE FROM tbl WHERE data NOT IN ('first item', 'second item', 'third item') in second case.\nAs it is stated in the official SQLite FAQ, \"Threads are evil. Avoid them.\" As far as I remember there were always problems with threads+sqlite. It's not that sqlite is not working with threads at all, just don't rely much on this feature. You can also make single thread working with database and pass all queries to it first, but effectiveness of such approach is heavily dependent on style of database usage in your program.","Q_Score":0,"Tags":"python,sqlite,multithreading","A_Id":2378530,"CreationDate":"2010-03-04T10:14:00.000","Title":"Need help on python sqlite?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"Writing an app in Python, and been playing with various ORM setups and straight SQL. All of which are ugly as sin.\nI have been looking at ZODB as an object store, and it looks a promising alternative... would you recommend it? What are your experiences, problems, and criticism, particularly regarding developer's perspectives, scalability, integrity, long-term maintenance and alternatives? Anyone start a project with it and ditch it? Why?\nWhilst the ideas behind ZODB, Pypersyst and others are interesting, there seems to be a lack of enthusiasm around for them :(","AnswerCount":5,"Available Count":3,"Score":1.0,"is_accepted":false,"ViewCount":10874,"Q_Id":2388870,"Users Score":15,"Answer":"Compared to \"any key-value store\", the key features for ZODB would be automatic integration of attribute changes with real ACID transactions, and clean, \"arbitrary\" references to other persistent objects.\nThe ZODB is bigger than just the FileStorage used by default in Zope:\n\nThe RelStorage backend lets you put your data in an RDBMS which can be backed up, replicated, etc. using standard tools.\nZEO allows easy scaling of appservers and off-line jobs.\nThe two-phase commit support allows coordinating transactions among multiple databases, including RDBMSes (assuming that they provide a TPC-aware layer).\nEasy hierarchy based on object attributes or containment:  you don't need to write recursive self-joins to emulate it.\nFilesystem-based BLOB support makes serving large files trivial to implement.\n\nOverall, I'm very happy using ZODB for nearly any problem where the shape of the data is not obviously \"square\".","Q_Score":43,"Tags":"python,zodb","A_Id":2390062,"CreationDate":"2010-03-05T18:01:00.000","Title":"ZODB In Real Life","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Writing an app in Python, and been playing with various ORM setups and straight SQL. All of which are ugly as sin.\nI have been looking at ZODB as an object store, and it looks a promising alternative... would you recommend it? What are your experiences, problems, and criticism, particularly regarding developer's perspectives, scalability, integrity, long-term maintenance and alternatives? Anyone start a project with it and ditch it? Why?\nWhilst the ideas behind ZODB, Pypersyst and others are interesting, there seems to be a lack of enthusiasm around for them :(","AnswerCount":5,"Available Count":3,"Score":0.1973753202,"is_accepted":false,"ViewCount":10874,"Q_Id":2388870,"Users Score":5,"Answer":"I would recommend it.\nI really don't have any criticisms. If it's an object store your looking for, this is the one to use. I've stored 2.5 million objects in it before and didn't feel a pinch.","Q_Score":43,"Tags":"python,zodb","A_Id":2391063,"CreationDate":"2010-03-05T18:01:00.000","Title":"ZODB In Real Life","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Writing an app in Python, and been playing with various ORM setups and straight SQL. All of which are ugly as sin.\nI have been looking at ZODB as an object store, and it looks a promising alternative... would you recommend it? What are your experiences, problems, and criticism, particularly regarding developer's perspectives, scalability, integrity, long-term maintenance and alternatives? Anyone start a project with it and ditch it? Why?\nWhilst the ideas behind ZODB, Pypersyst and others are interesting, there seems to be a lack of enthusiasm around for them :(","AnswerCount":5,"Available Count":3,"Score":0.0798297691,"is_accepted":false,"ViewCount":10874,"Q_Id":2388870,"Users Score":2,"Answer":"ZODB has been used for plenty of large databases\nMost ZODB usage is\/was probably Zope users who migrated away if they migrate away from Zope\nPerformance is not so good as relatonal database+ORM especially if you have lots of writes.\nLong term maintenance is not so bad, you want to pack the database from time to time, but that can be done live.\nYou have to use ZEO if you are going to use more than one process with your ZODB which is quite a lot slower than using ZODB directly\nI have no idea how ZODB performs on flash disks.","Q_Score":43,"Tags":"python,zodb","A_Id":2389155,"CreationDate":"2010-03-05T18:01:00.000","Title":"ZODB In Real Life","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I process a lot of text\/data that I exchange between Python, R, and sometimes Matlab.\nMy go-to is the flat text file, but also use SQLite occasionally to store the data and access from each program (not Matlab yet though). I don't use GROUPBY, AVG, etc. in SQL as much as I do these operations in R, so I don't necessarily require the database operations.\nFor such applications that requires exchanging data among programs to make use of available libraries in each language, is there a good rule of thumb on which data exchange format\/method to use (even XML or NetCDF or HDF5)?\nI know between Python -> R there is rpy or rpy2 but I was wondering about this question in a more general sense - I use many computers which all don't have rpy2 and also use a few other pieces of scientific analysis software that require access to the data at various times (the stages of processing and analysis are also separated).","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":3563,"Q_Id":2392017,"Users Score":15,"Answer":"If all the languages support SQLite - use it. The power of SQL might not be useful to you right now, but it probably will be at some point, and it saves you having to rewrite things later when you decide you want to be able to query your data in more complicated ways.\nSQLite will also probably be substantially faster if you only want to access certain bits of data in your datastore - since doing that with a flat-text file is challenging without reading the whole file in (though it's not impossible).","Q_Score":8,"Tags":"python,sql,database,r,file-format","A_Id":2392026,"CreationDate":"2010-03-06T09:30:00.000","Title":"SQLite or flat text file?","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"They will also search part of their name. Not only words with spaces.\nIf they type \"Matt\", I expect to retrieve \"Matthew\" too.","AnswerCount":4,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":291,"Q_Id":2394870,"Users Score":0,"Answer":"If you are trying to search for the names through any development Language, you can use the Regular expression package in Java.\nSome thing like java.util.regex.*;","Q_Score":3,"Tags":"python,mysql,database,search,indexing","A_Id":2395473,"CreationDate":"2010-03-07T01:54:00.000","Title":"Suppose I have 400 rows of people's names in a database. What's the best way to do a search for their names?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Say I have a simple table that contains username, firstname, lastname.\nHow do I express this in berkeley Db?\nI'm currently using bsddb as the interface.\nCheers.","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1199,"Q_Id":2399643,"Users Score":4,"Answer":"You have to pick one \"column\" as the key (must be unique; I imagine that would be \"username\" in your case) -- the only way searches will ever possibly happen.  The other columns can be made to be the single string value of that key by any way you like, from pickling to simple joining with a character that's guaranteed to never occur in any of the columns, such as `\\0' for many kind of \"readable text strings\".\nIf you need to be able to search by different keys you'll need other, supplementary and separate bsddb databases set up as \"indices\" into your main table -- it's lots of work, and there's lots of literature on the subject.  (Alternatively, you move to a higher-abstraction technology, such as sqlite, which handles the indexing neatly on your behalf;-).","Q_Score":1,"Tags":"python,berkeley-db,bsddb,okvs","A_Id":2399691,"CreationDate":"2010-03-08T06:25:00.000","Title":"Expressing multiple columns in berkeley db in python?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Suppose I have 500 rows of data, each with a paragraph of text (like this paragraph). That's it.I want to do a search that matches part of words. (%LIKE%, not FULL_TEXT)\nWhat would be faster?\n\nSELECT * FROM ...WHERE LIKE \"%query%\"; This would put load on the database server.\nSelect all. Then, go through each one and do .find >= 0 This would put load on the web server.\n\nThis is a website, and people will be searching frequently.","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":105,"Q_Id":2401508,"Users Score":1,"Answer":"This is very hard for us to determine without knowing:\n\nthe amount of text to search\nthe load and configuration on the database server\nthe load and configuration on on the webserver\netc etc ...\n\nWith that said i would conceptually definitely go for the first scenario. It should be lightening-fast when searching only 500 rows.","Q_Score":0,"Tags":"python,mysql,database,regex,search","A_Id":2401635,"CreationDate":"2010-03-08T13:18:00.000","Title":"What would be the most efficient way to do this search (mysql or text)?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have an idea for a product that I want to be web-based. But because I live in a part of the world where the internet is not always available, there needs to be a client desktop component that is available for when the internet is down. Also, I have been a SQL programmer, a desktop application programmer using dBase, VB and Pascal, and I have created simple websites using HTML and website creation tools, such as Frontpage. \nSo from my research, I think I have the following options; PHP, Ruby on Rails, Python or .NET for the programming side. MySQL for the DB. And Apache, or possibly IIS, for the webserver. \nI will probably start with a local ISP provider for the cloud servce. But then maybe move to something more \"robust\" and universal in the future, ie. Amazon, or Azure, or something along that line. \nMy question then is this. What would you recommend for something like this? I'm sure that I have not listed all of the possibilities, but the ones I have researched and thought of.\nThanks everyone,\nCraig","AnswerCount":3,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":174,"Q_Id":2428077,"Users Score":0,"Answer":"If you wan't to run a version of the server on desktops, your best options would be Python, Rails, or Java servlets, all of which can be easily packaged into small self contained servers with no dependencies.\nMy recommendation for the desktop would be HTML 5 local storage.  The standard hasn't been finalized, but there is experimental support in Google Chrome.  If you can force your users to use a specific browser version, you should be OK, until it is finalized.\nI would recommend looking at Django and Rails before any other framework.  They have different design philosophies, so one of them might be better suited for your application.  Another framework to consider is Grails, which is essentially a clone of Rails in the groovy language.","Q_Score":1,"Tags":"php,python,ruby-on-rails,programming-languages,saas","A_Id":2430572,"CreationDate":"2010-03-11T19:38:00.000","Title":"Old desktop programmer wants to create S+S project","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have an idea for a product that I want to be web-based. But because I live in a part of the world where the internet is not always available, there needs to be a client desktop component that is available for when the internet is down. Also, I have been a SQL programmer, a desktop application programmer using dBase, VB and Pascal, and I have created simple websites using HTML and website creation tools, such as Frontpage. \nSo from my research, I think I have the following options; PHP, Ruby on Rails, Python or .NET for the programming side. MySQL for the DB. And Apache, or possibly IIS, for the webserver. \nI will probably start with a local ISP provider for the cloud servce. But then maybe move to something more \"robust\" and universal in the future, ie. Amazon, or Azure, or something along that line. \nMy question then is this. What would you recommend for something like this? I'm sure that I have not listed all of the possibilities, but the ones I have researched and thought of.\nThanks everyone,\nCraig","AnswerCount":3,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":174,"Q_Id":2428077,"Users Score":0,"Answer":"The languages you list are all serverside components. The big question is whether you can sensibly build a thick client - effectively you could develop a multi-tier application where the webserver sits on the client and uses a webservice as a datafeed if\/when its available but the solution is not very portable.\nYou could build a purely ajax driven website in javascript then deploy it to the client as signed javascripts on  the local filesystem (they need to be signed to get around the restriction that javscripts can only connect back to the server where they served from normally).\nAnother approach would be to use Google Gears - but that would be a single browser solution.\nC.","Q_Score":1,"Tags":"php,python,ruby-on-rails,programming-languages,saas","A_Id":2429484,"CreationDate":"2010-03-11T19:38:00.000","Title":"Old desktop programmer wants to create S+S project","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have an idea for a product that I want to be web-based. But because I live in a part of the world where the internet is not always available, there needs to be a client desktop component that is available for when the internet is down. Also, I have been a SQL programmer, a desktop application programmer using dBase, VB and Pascal, and I have created simple websites using HTML and website creation tools, such as Frontpage. \nSo from my research, I think I have the following options; PHP, Ruby on Rails, Python or .NET for the programming side. MySQL for the DB. And Apache, or possibly IIS, for the webserver. \nI will probably start with a local ISP provider for the cloud servce. But then maybe move to something more \"robust\" and universal in the future, ie. Amazon, or Azure, or something along that line. \nMy question then is this. What would you recommend for something like this? I'm sure that I have not listed all of the possibilities, but the ones I have researched and thought of.\nThanks everyone,\nCraig","AnswerCount":3,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":174,"Q_Id":2428077,"Users Score":0,"Answer":"If you want a 'desktop component' that is available for you to do development on whenever your internet is out, you could really choose any of those technologies. You can always have a local server (like apache) running on your machine, as well as a local sql database, though if your database contains a large amount of data you may need to scale it down.\nRuby on Rails may be the easiest for you to get started with, though, since it comes packaged with WEBrick (a ruby library that provides HTTP services), and SQLite, a lightweight SQL database management system.  Ruby on Rails is configured by default to use these.","Q_Score":1,"Tags":"php,python,ruby-on-rails,programming-languages,saas","A_Id":2428452,"CreationDate":"2010-03-11T19:38:00.000","Title":"Old desktop programmer wants to create S+S project","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Let's say I have an user registration form.  In this form, I have the option for the user to upload a photo. I have an User table and Photo table.  My User table has a \"PathToPhoto\" column.  My question is how do I fill in the \"PathToPhoto\" column if the photo is uploaded and inserted into Photo table before the user is created?  Another way to phrase my question is how to get the newly uploaded photo to be associated to the user that may or may not be created next. \nI'm using python and postgresql.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":397,"Q_Id":2435281,"Users Score":0,"Answer":"To make sure we're on the same page, is the following correct?\n\nYou're inserting the photo information into the Photo table immediately after the user uploads the photo but before he\/she submits the form;\nWhen the user submits the form, you're inserting a row into the User table;\nOne of the items in that row is information about the previously created photo entry.\n\nIf so, you should be able to store the \"path to photo\" information in a Python variable until the user submits the form, and then use the value from that variable in your User-table insert.","Q_Score":0,"Tags":"python,database,postgresql","A_Id":2435639,"CreationDate":"2010-03-12T19:32:00.000","Title":"Database: storing data from user registration form","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am planning to make some big project (1 000 000 users, approximately 500 request pre second - in hot time).\nFor performance I'm going to use no relational dbms (each request could cost lot of instructions in relational dbms like mysql) - so i can't use DAL.\nMy question is:\n\nhow web2py is working with a big traffic, is it work concurrently? I'm consider to use web2py or Gork - Zope,\nHow is working zodb(Z Object Database) with a lot of data? Is there some comparison with object-relational postgresql?\n\nCould you advice me please.","AnswerCount":3,"Available Count":2,"Score":0.0665680765,"is_accepted":false,"ViewCount":1388,"Q_Id":2459549,"Users Score":1,"Answer":"Zope and the ZODB have been used with big applications, but I'd still consider linking Zope with MySQL or something like that for serious large-scale applications.  Even though Zope has had a lot of development cycles, it is usually used with another database engine for good reason.  As far as I know, the argument applies doubly for web2py.","Q_Score":3,"Tags":"python,zope,web2py,zodb,grok","A_Id":9985357,"CreationDate":"2010-03-17T02:26:00.000","Title":"web2py or grok (zope) on a big portal,","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am planning to make some big project (1 000 000 users, approximately 500 request pre second - in hot time).\nFor performance I'm going to use no relational dbms (each request could cost lot of instructions in relational dbms like mysql) - so i can't use DAL.\nMy question is:\n\nhow web2py is working with a big traffic, is it work concurrently? I'm consider to use web2py or Gork - Zope,\nHow is working zodb(Z Object Database) with a lot of data? Is there some comparison with object-relational postgresql?\n\nCould you advice me please.","AnswerCount":3,"Available Count":2,"Score":1.0,"is_accepted":false,"ViewCount":1388,"Q_Id":2459549,"Users Score":7,"Answer":"First, don't assume that a data abstraction layer will have unacceptable performance, until you actually see it in practice.  It is pretty easy to switch to RAW sql if and when you run into a problem.\nSecond, most users who worry about there server technology handling a million users never finish their applications.  Pick whatever technology you think will enable you to build the best application in the shortest time.  Any technology can be scaled, at the very least, through clustering.","Q_Score":3,"Tags":"python,zope,web2py,zodb,grok","A_Id":2459620,"CreationDate":"2010-03-17T02:26:00.000","Title":"web2py or grok (zope) on a big portal,","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am using Python MySQLDB, and I want to insert this into DATETIME field in Mysql .  How do I do that with cursor.execute?","AnswerCount":3,"Available Count":1,"Score":0.0665680765,"is_accepted":false,"ViewCount":9981,"Q_Id":2460491,"Users Score":1,"Answer":"Solved.\nI just did this:\ndatetime.datetime.now() ...insert that into the column.","Q_Score":5,"Tags":"python,mysql,database,datetime,date","A_Id":2460546,"CreationDate":"2010-03-17T07:28:00.000","Title":"In Python, if I have a unix timestamp, how do I insert that into a MySQL datetime field?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I want to store the images related to a each person's profile in the DB and retrieve them\nwhen requested and save it as .jpg file - and display it to the users.\nHow could I render the image data stored in the DB as an image and store it locally??","AnswerCount":3,"Available Count":1,"Score":0.0665680765,"is_accepted":false,"ViewCount":19327,"Q_Id":2477045,"Users Score":1,"Answer":"Why don't you simply store the images on the file system, and only store their references on the database. That's a lot more elegant, and won't consume loads of your database.\nAlso, you won't have to use any kind of binary functions to read them from the DB, saving memory and loading time.\nIs there a very specific reason why you wanna store it on the DB?\nCheers","Q_Score":3,"Tags":"python,image-manipulation","A_Id":2477074,"CreationDate":"2010-03-19T12:08:00.000","Title":"Storing and Retrieving Images from Database using Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"A legacy web application written using PHP and utilizing MySql database needs to be rewritten completely. However, the existing database structure must not be changed at all.\nI'm looking for suggestions on which framework would be most suitable for this task? Language candidates are Python, PHP, Ruby and Java.\nAccording to many sources it might be challenging to utilize rails effectively with existing database. Also I have not found a way to automatically generate models out of the database.\nWith Django it's very easy to generate models automatically. However I'd appreciate first hand experience on its suitability to work with legacy DBs. The database in question contains all kinds of primary keys, including lots of composite keys.\nAlso I appreciate suggestions of other frameworks worth considering.","AnswerCount":8,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":1525,"Q_Id":2507463,"Users Score":0,"Answer":"There are no clear cut winners when picking a web framework. Each platform you mentioned has its benefits and drawbacks (cost of hardware, professional support, community support, etc.). Depending on your time table, project requirements, and available hardware resources you are probably going to need some different answers.Personally, I would start your investigation with a platform where you and your team are most experienced. \nLike many of the other posters I can only speak to what I'm actively using now, and in my case it is Java. If Java seems to match your projects requirements, you probably want to go with one of the newer frameworks with an active community. Currently Spring Web MVC, Struts2, and Stripes seem to be fairly popular. These frameworks are mostly, if not totally, independent of the persistence layer, but all integrate well with technologies like hibernate and jpa; although you have to do most, if not all, of the wiring yourself. \nIf you want to take the Java road there are also pre-built application stacks that take care of most of wiring issues for you. For an example you might want to look at Matt Raible's AppFuse. He has built an extensible starter application with many permutations of popular java technologies.\nIf you are interested in the JVM as a platform, you may also want to look at complete stack solutions like Grails, or tools that help you build your stack quickly like Spring Roo. \nAlmost all of the full stack solutions I've seen allow for integration with a legacy database schema. As long as your database is well designed, you should be able to map your tables. The mention of composite keys kind of scares me, but depending on your persistence technology this may or may not be an issue. Hibernate in Java\/.NET supports mapping to composite keys, as does GORM in grails (built on hibernate). In almost all cases these mappings are discouraged, but people who build persistence frameworks know you can't always scorch earth and completely recreate your model.","Q_Score":1,"Tags":"java,php,python,ruby","A_Id":2512975,"CreationDate":"2010-03-24T12:11:00.000","Title":"Web framework for an application utilizing existing database?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"A legacy web application written using PHP and utilizing MySql database needs to be rewritten completely. However, the existing database structure must not be changed at all.\nI'm looking for suggestions on which framework would be most suitable for this task? Language candidates are Python, PHP, Ruby and Java.\nAccording to many sources it might be challenging to utilize rails effectively with existing database. Also I have not found a way to automatically generate models out of the database.\nWith Django it's very easy to generate models automatically. However I'd appreciate first hand experience on its suitability to work with legacy DBs. The database in question contains all kinds of primary keys, including lots of composite keys.\nAlso I appreciate suggestions of other frameworks worth considering.","AnswerCount":8,"Available Count":2,"Score":0.049958375,"is_accepted":false,"ViewCount":1525,"Q_Id":2507463,"Users Score":2,"Answer":"I have very good experience with Django. Every time I needed it was up to the task for interfacing with existing database. \nAutogenerated models are the start, as MySQL is not the strictest with its schema. Not that it will not work only that usually some of the db restrictions are held in app itself.","Q_Score":1,"Tags":"java,php,python,ruby","A_Id":2507492,"CreationDate":"2010-03-24T12:11:00.000","Title":"Web framework for an application utilizing existing database?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am in need of a lightweight way to store dictionaries of data into a database. What I need is something that: \n\nCreates a database table from a simple type description (int, float, datetime etc)\nTakes a dictionary object and inserts it into the database (including handling datetime objects!)\nIf possible: Can handle basic references, so the dictionary can reference other tables\n\nI would prefer something that doesn't do a lot of magic. I just need an easy way to setup and get data into an SQL database. \nWhat would you suggest? There seems to be a lot of ORM software around, but I find it hard to evaluate them.","AnswerCount":4,"Available Count":1,"Score":0.1488850336,"is_accepted":false,"ViewCount":1069,"Q_Id":2539147,"Users Score":3,"Answer":"SQLAlchemy offers an ORM much like django, but does not require that you work within a web framework.","Q_Score":1,"Tags":"python,sql,orm","A_Id":2539235,"CreationDate":"2010-03-29T15:30:00.000","Title":"Lightweight Object->Database in Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"Recently i have developed a billing application for my company with Python\/Django. For few months everything was fine but now i am observing that the performance is dropping because of more and more users using that applications. Now the problem is that the application is now very critical for the finance team. Now the finance team are after my life for sorting out the performance issue. I have no other option but to find a way to increase the performance of the billing application. \nSo do you guys know any performance optimization techniques in python that will really help me   with the scalability issue\nGuys we are using mysql database and its hosted on apache web server on Linux box. Secondly what i have noticed more is the over all application is slow and not the database transactional part. For example once the application is loaded then it works fine but if they navigate to other link on that application then it takes a whole lot of time.\nAnd yes we are using HTML, CSS and Javascript","AnswerCount":9,"Available Count":3,"Score":1.0,"is_accepted":false,"ViewCount":1942,"Q_Id":2545820,"Users Score":6,"Answer":"ok, not entirely to the point, but before you go and start fixing it, make sure everyone understands the situation. it seems to me that they're putting some pressure on you to fix the \"problem\".\nwell first of all, when you wrote the application, have they specified the performance requirements? did they tell you that they need operation X to take less than Y secs to complete? Did they specify how many concurrent users must be supported without penalty to the performance? If not, then tell them to back off and that it is iteration (phase, stage, whatever) one of the deployment, and the main goal was the functionality and testing. phase two is performance improvements. let them (with your help obviously) come up with some non functional requirements for the performance of your system.\nby doing all this, a) you'll remove the pressure applied by the finance team (and i know they can be a real pain in the bum) b) both you and your clients will have a clear idea of what you mean by \"performance\" c) you'll have a base that you can measure your progress and most importantly d) you'll have some agreed time to implement\/fix the performance issues.\nPS. that aside, look at the indexing... :)","Q_Score":11,"Tags":"python","A_Id":2545940,"CreationDate":"2010-03-30T14:07:00.000","Title":"Optimization Techniques in Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Recently i have developed a billing application for my company with Python\/Django. For few months everything was fine but now i am observing that the performance is dropping because of more and more users using that applications. Now the problem is that the application is now very critical for the finance team. Now the finance team are after my life for sorting out the performance issue. I have no other option but to find a way to increase the performance of the billing application. \nSo do you guys know any performance optimization techniques in python that will really help me   with the scalability issue\nGuys we are using mysql database and its hosted on apache web server on Linux box. Secondly what i have noticed more is the over all application is slow and not the database transactional part. For example once the application is loaded then it works fine but if they navigate to other link on that application then it takes a whole lot of time.\nAnd yes we are using HTML, CSS and Javascript","AnswerCount":9,"Available Count":3,"Score":1.2,"is_accepted":true,"ViewCount":1942,"Q_Id":2545820,"Users Score":4,"Answer":"A surprising feature of Python is that the pythonic code is quite efficient... So a few general hints:\n\nUse built-ins and standard functions whenever possible, they're already quite well optimized.\nTry to use lazy generators instead one-off temporary lists.\nUse numpy for vector arithmetic.\nUse psyco if running on x86 32bit.\nWrite performance critical loops in a lower level language (C, Pyrex, Cython, etc.).\nWhen calling the same method of a collection of objects, get a reference to the class function and use it, it will save lookups in the objects dictionaries (this one is a micro-optimization, not sure it's worth)\n\nAnd of course, if scalability is what matters:\n\nUse O(n) (or better) algorithms! Otherwise your system cannot be linearly scalable.\nWrite multiprocessor aware code. At some point you'll need to throw more computing power at it, and your software must be ready to use it!","Q_Score":11,"Tags":"python","A_Id":2546955,"CreationDate":"2010-03-30T14:07:00.000","Title":"Optimization Techniques in Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Recently i have developed a billing application for my company with Python\/Django. For few months everything was fine but now i am observing that the performance is dropping because of more and more users using that applications. Now the problem is that the application is now very critical for the finance team. Now the finance team are after my life for sorting out the performance issue. I have no other option but to find a way to increase the performance of the billing application. \nSo do you guys know any performance optimization techniques in python that will really help me   with the scalability issue\nGuys we are using mysql database and its hosted on apache web server on Linux box. Secondly what i have noticed more is the over all application is slow and not the database transactional part. For example once the application is loaded then it works fine but if they navigate to other link on that application then it takes a whole lot of time.\nAnd yes we are using HTML, CSS and Javascript","AnswerCount":9,"Available Count":3,"Score":0.0444152037,"is_accepted":false,"ViewCount":1942,"Q_Id":2545820,"Users Score":2,"Answer":"before you can \"fix\" something you need to know what is \"broken\". In software development that means profiling, profiling, profiling. Did I mention profiling. Without profiling you don't know where CPU cycles and wall clock time is going. Like others have said to get any more useful information you need to post the details of your entire stack. Python version, what you are using to store the data in (mysql, postgres, flat files, etc), what web server interface cgi, fcgi, wsgi, passenger, etc. how you are generating the HTML, CSS and assuming Javascript. Then you can get more specific answers to those tiers.","Q_Score":11,"Tags":"python","A_Id":2546996,"CreationDate":"2010-03-30T14:07:00.000","Title":"Optimization Techniques in Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Why do people use SQLAlchemy instead of MySQLdb? What advantages does it offer?","AnswerCount":3,"Available Count":3,"Score":1.0,"is_accepted":false,"ViewCount":19410,"Q_Id":2550292,"Users Score":6,"Answer":"In addition to what Alex said...\n\n\"Not wanting to learn SQL\" is probably a bad thing. However, if you want to get more non-technical people involved as part of the development process, ORMs do a pretty good job at it because it does push this level of complexity down a level. One of the elements that has made Django successful is its ability to let \"newspaper journalists\" maintain a website, rather than software engineers.\n\nOne of the limitations of ORMs is that they are not as scalable as using raw SQL. At a previous job, we wanted to get rid of a lot of manual SQL generation and switched to an ORM for ease-of-use (SQLAlchemy, Elixir, etc.), but months later, I ended up having to write raw SQL again to get around the inefficient or high latency queries that were generated by the ORM system.","Q_Score":24,"Tags":"python,sql,mysql,sqlalchemy","A_Id":2550578,"CreationDate":"2010-03-31T03:19:00.000","Title":"Purpose of SQLAlchemy over MySQLdb","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Why do people use SQLAlchemy instead of MySQLdb? What advantages does it offer?","AnswerCount":3,"Available Count":3,"Score":1.2,"is_accepted":true,"ViewCount":19410,"Q_Id":2550292,"Users Score":32,"Answer":"You don't use SQLAlchemy instead of MySQLdb\u2014you use SQLAlchemy to access something like MySQLdb, oursql (another MySQL driver that I hear is nicer and has better performance), the sqlite3 module, psycopg2, or whatever other database driver you are using. \nAn ORM (like SQLAlchemy) helps abstract away the details of the database you are using. This allows you to keep from the miry details of the database system you're using, avoiding the possibility of errors some times (and introducing the possibility of others), and making porting trivial (at least in theory).","Q_Score":24,"Tags":"python,sql,mysql,sqlalchemy","A_Id":2550364,"CreationDate":"2010-03-31T03:19:00.000","Title":"Purpose of SQLAlchemy over MySQLdb","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Why do people use SQLAlchemy instead of MySQLdb? What advantages does it offer?","AnswerCount":3,"Available Count":3,"Score":1.0,"is_accepted":false,"ViewCount":19410,"Q_Id":2550292,"Users Score":12,"Answer":"Easier portability among different DB engines (say that tomorrow you decide you want to move to sqlite, or PostgreSQL, or...), and higher level of abstraction (and thus potentially higher productivity).\nThose are some of the good reasons.  There are also some bad reasons for using an ORM, such as not wanting to learn SQL, but I suspect SQLAlchemy in particular is not really favored by people for such bad reasons for wanting an ORM rather than bare SQL;-).","Q_Score":24,"Tags":"python,sql,mysql,sqlalchemy","A_Id":2550304,"CreationDate":"2010-03-31T03:19:00.000","Title":"Purpose of SQLAlchemy over MySQLdb","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm going to write the web portal using Cassandra databases.\nCan you advise me which python interface to use? thrift, lazygal or pycassa?\nAre there any benefits to use more complicated thrift then cleaner pycassa?\nWhat about performace - is the same (all of them are just the layer)?\nThanks for any advice.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1065,"Q_Id":2561804,"Users Score":4,"Answer":"Use pycassa if you don't know what to use.\nUse lazyboy if you want it to maintain indexes for you.  It's significantly more complex.","Q_Score":5,"Tags":"python,database,cassandra,thrift","A_Id":2567396,"CreationDate":"2010-04-01T16:05:00.000","Title":"Cassandra database, which python interface?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I currently have a SQL database of passwords stored in MD5. The server needs to generate a unique key, then sends to the client. In the client, it will use the key as a salt then hash together with the password and send back to the server.\nThe only problem is that the the SQL DB has the passwords in MD5 already. Therefore for this to work, I would have to MD5 the password client side, then MD5 it again with the salt. Am I doing this wrong, because it doesn't seem like a proper solution. Any information is appreciated.","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":260,"Q_Id":2564312,"Users Score":1,"Answer":"You should use SSL to encrypt the connection, then send the password over plain text from the client. The server will then md5 and compare with the md5 hash in the database to see if they are the same. If so auth = success.\nMD5'ing the password on the client buys you nothing because a hacker with the md5 password can get in just as easy as if it was in plain text.","Q_Score":2,"Tags":"python,sql,database,authorization,md5","A_Id":2564367,"CreationDate":"2010-04-01T23:42:00.000","Title":"Server authorization with MD5 and SQL","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Is there an easy way (without downloading any plugins) to connect to a MySQL database in Python?\nAlso, what would be the difference from calling a PHP script to retrieve the data from the database and hand it over to Python and importing one of these third-parties plugins that requires some additional software in the server.\nEDIT: the server has PHP and Python installed by default.","AnswerCount":3,"Available Count":2,"Score":-0.0665680765,"is_accepted":false,"ViewCount":332,"Q_Id":2569427,"Users Score":-1,"Answer":"No, there is no way that I've ever heard of or can think of to connect to a MySQL database with vanilla python.  Just install the MySqldb python package-\nYou can typically do:\n\nsudo easy_install MySqldb","Q_Score":0,"Tags":"php,python,mysql","A_Id":2569567,"CreationDate":"2010-04-02T22:00:00.000","Title":"Python and MySQL","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Is there an easy way (without downloading any plugins) to connect to a MySQL database in Python?\nAlso, what would be the difference from calling a PHP script to retrieve the data from the database and hand it over to Python and importing one of these third-parties plugins that requires some additional software in the server.\nEDIT: the server has PHP and Python installed by default.","AnswerCount":3,"Available Count":2,"Score":-0.0665680765,"is_accepted":false,"ViewCount":332,"Q_Id":2569427,"Users Score":-1,"Answer":"If you don't want to download the python libraries to connect to MySQL, the effective answer is no, not trivially.","Q_Score":0,"Tags":"php,python,mysql","A_Id":2569448,"CreationDate":"2010-04-02T22:00:00.000","Title":"Python and MySQL","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am an occasional Python programer who only have worked so far with MYSQL or SQLITE databases. I am the computer person for everything in a small company and I have been started a new project where I think it is about time to try new databases. \nSales department makes a CSV dump every week and I need to make a small scripting application that allow people form other departments mixing the information, mostly linking the records. I have all this solved, my problem is the speed, I am using just plain text files for all this and unsurprisingly it is very slow.\nI thought about using mysql, but then I need installing mysql in every desktop, sqlite is easier, but it is very slow. I do not need a full relational database, just some way of play with big amounts of data in a decent time.\nUpdate: I think I was not being very detailed about my database usage thus explaining my problem badly. I am working reading all the data ~900 Megas or more from a csv into a Python dictionary then working with it. My problem is storing and mostly reading the data quickly.\nMany thanks!","AnswerCount":9,"Available Count":7,"Score":0.022218565,"is_accepted":false,"ViewCount":11416,"Q_Id":2577967,"Users Score":1,"Answer":"It has been a couple of months since I posted this question and I wanted to let you all know how I solved this problem. I am using Berkeley DB with the module bsddb instead loading all the data in a Python dictionary. I am not fully happy, but my users are.\nMy next step is trying to get a shared server with redis, but unless users starts complaining about speed, I doubt I will get it.\nMany thanks everybody who helped here, and I hope this question and answers are useful to somebody else.","Q_Score":15,"Tags":"python,database,nosql,data-mining","A_Id":2981162,"CreationDate":"2010-04-05T10:59:00.000","Title":"Best DataMining Database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am an occasional Python programer who only have worked so far with MYSQL or SQLITE databases. I am the computer person for everything in a small company and I have been started a new project where I think it is about time to try new databases. \nSales department makes a CSV dump every week and I need to make a small scripting application that allow people form other departments mixing the information, mostly linking the records. I have all this solved, my problem is the speed, I am using just plain text files for all this and unsurprisingly it is very slow.\nI thought about using mysql, but then I need installing mysql in every desktop, sqlite is easier, but it is very slow. I do not need a full relational database, just some way of play with big amounts of data in a decent time.\nUpdate: I think I was not being very detailed about my database usage thus explaining my problem badly. I am working reading all the data ~900 Megas or more from a csv into a Python dictionary then working with it. My problem is storing and mostly reading the data quickly.\nMany thanks!","AnswerCount":9,"Available Count":7,"Score":0.0,"is_accepted":false,"ViewCount":11416,"Q_Id":2577967,"Users Score":0,"Answer":"Take a look at mongodb.","Q_Score":15,"Tags":"python,database,nosql,data-mining","A_Id":2581460,"CreationDate":"2010-04-05T10:59:00.000","Title":"Best DataMining Database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am an occasional Python programer who only have worked so far with MYSQL or SQLITE databases. I am the computer person for everything in a small company and I have been started a new project where I think it is about time to try new databases. \nSales department makes a CSV dump every week and I need to make a small scripting application that allow people form other departments mixing the information, mostly linking the records. I have all this solved, my problem is the speed, I am using just plain text files for all this and unsurprisingly it is very slow.\nI thought about using mysql, but then I need installing mysql in every desktop, sqlite is easier, but it is very slow. I do not need a full relational database, just some way of play with big amounts of data in a decent time.\nUpdate: I think I was not being very detailed about my database usage thus explaining my problem badly. I am working reading all the data ~900 Megas or more from a csv into a Python dictionary then working with it. My problem is storing and mostly reading the data quickly.\nMany thanks!","AnswerCount":9,"Available Count":7,"Score":1.0,"is_accepted":false,"ViewCount":11416,"Q_Id":2577967,"Users Score":12,"Answer":"You probably do need a full relational DBMS, if not right now, very soon.  If you start now while your problems and data are simple and straightforward then when they become complex and difficult you will have plenty of experience with at least one DBMS to help you.  You probably don't need MySQL on all desktops, you might install it on a server for example and feed data out over your network, but you perhaps need to provide more information about your requirements, toolset and equipment to get better suggestions.\nAnd, while the other DBMSes have their strengths and weaknesses too, there's nothing wrong with MySQL for large and complex databases.  I don't know enough about SQLite to comment knowledgeably about it.\nEDIT: @Eric from your comments to my answer and the other answers I form even more strongly the view that it is time you moved to a database.  I'm not surprised that trying to do database operations on a 900MB Python dictionary is slow.  I think you have to first convince yourself, then your management, that you have reached the limits of what your current toolset can cope with, and that future developments are threatened unless you rethink matters.\nIf your network really can't support a server-based database than (a) you really need to make your network robust, reliable and performant enough for such a purpose, but (b) if that is not an option, or not an early option, you should be thinking along the lines of a central database server passing out digests\/extracts\/reports to other users, rather than simultaneous, full RDBMS working in a client-server configuration.\nThe problems you are currently experiencing are problems of not having the right tools for the job.  They are only going to get worse.  I wish I could suggest a magic way in which this is not the case, but I can't and I don't think anyone else will.","Q_Score":15,"Tags":"python,database,nosql,data-mining","A_Id":2577979,"CreationDate":"2010-04-05T10:59:00.000","Title":"Best DataMining Database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am an occasional Python programer who only have worked so far with MYSQL or SQLITE databases. I am the computer person for everything in a small company and I have been started a new project where I think it is about time to try new databases. \nSales department makes a CSV dump every week and I need to make a small scripting application that allow people form other departments mixing the information, mostly linking the records. I have all this solved, my problem is the speed, I am using just plain text files for all this and unsurprisingly it is very slow.\nI thought about using mysql, but then I need installing mysql in every desktop, sqlite is easier, but it is very slow. I do not need a full relational database, just some way of play with big amounts of data in a decent time.\nUpdate: I think I was not being very detailed about my database usage thus explaining my problem badly. I am working reading all the data ~900 Megas or more from a csv into a Python dictionary then working with it. My problem is storing and mostly reading the data quickly.\nMany thanks!","AnswerCount":9,"Available Count":7,"Score":0.022218565,"is_accepted":false,"ViewCount":11416,"Q_Id":2577967,"Users Score":1,"Answer":"It sounds like each department has their own feudal database, and this implies a lot of unnecessary redundancy and inefficiency.\nInstead of transferring hundreds of megabytes to everyone across your network, why not keep your data in MySQL and have the departments upload their data to the database, where it can be normalized and accessible by everyone?\nAs your organization grows, having completely different departmental databases that are unaware of each other, and contain potentially redundant or conflicting data, is going to become very painful.","Q_Score":15,"Tags":"python,database,nosql,data-mining","A_Id":2578659,"CreationDate":"2010-04-05T10:59:00.000","Title":"Best DataMining Database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am an occasional Python programer who only have worked so far with MYSQL or SQLITE databases. I am the computer person for everything in a small company and I have been started a new project where I think it is about time to try new databases. \nSales department makes a CSV dump every week and I need to make a small scripting application that allow people form other departments mixing the information, mostly linking the records. I have all this solved, my problem is the speed, I am using just plain text files for all this and unsurprisingly it is very slow.\nI thought about using mysql, but then I need installing mysql in every desktop, sqlite is easier, but it is very slow. I do not need a full relational database, just some way of play with big amounts of data in a decent time.\nUpdate: I think I was not being very detailed about my database usage thus explaining my problem badly. I am working reading all the data ~900 Megas or more from a csv into a Python dictionary then working with it. My problem is storing and mostly reading the data quickly.\nMany thanks!","AnswerCount":9,"Available Count":7,"Score":0.0,"is_accepted":false,"ViewCount":11416,"Q_Id":2577967,"Users Score":0,"Answer":"If you have that problem with a CSV file, maybe you can just pickle the dictionary and generate a pickle \"binary\" file with pickle.HIGHEST_PROTOCOL option. It can be faster to read and you get a smaller file. You can load the CSV file once and then generate the pickled file, allowing faster load in next accesses.\nAnyway, with 900 Mb of information, you're going to deal with some time loading it in memory. Another approach is not loading it on one step on memory, but load only the information when needed, maybe making different files by date, or any other category (company, type, etc..)","Q_Score":15,"Tags":"python,database,nosql,data-mining","A_Id":2578310,"CreationDate":"2010-04-05T10:59:00.000","Title":"Best DataMining Database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am an occasional Python programer who only have worked so far with MYSQL or SQLITE databases. I am the computer person for everything in a small company and I have been started a new project where I think it is about time to try new databases. \nSales department makes a CSV dump every week and I need to make a small scripting application that allow people form other departments mixing the information, mostly linking the records. I have all this solved, my problem is the speed, I am using just plain text files for all this and unsurprisingly it is very slow.\nI thought about using mysql, but then I need installing mysql in every desktop, sqlite is easier, but it is very slow. I do not need a full relational database, just some way of play with big amounts of data in a decent time.\nUpdate: I think I was not being very detailed about my database usage thus explaining my problem badly. I am working reading all the data ~900 Megas or more from a csv into a Python dictionary then working with it. My problem is storing and mostly reading the data quickly.\nMany thanks!","AnswerCount":9,"Available Count":7,"Score":0.022218565,"is_accepted":false,"ViewCount":11416,"Q_Id":2577967,"Users Score":1,"Answer":"Have you done any bench marking to confirm that it is the text files that are slowing you down? If you haven't, there's a good chance that tweaking some other part of the code will speed things up so that it's fast enough.","Q_Score":15,"Tags":"python,database,nosql,data-mining","A_Id":2578080,"CreationDate":"2010-04-05T10:59:00.000","Title":"Best DataMining Database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am an occasional Python programer who only have worked so far with MYSQL or SQLITE databases. I am the computer person for everything in a small company and I have been started a new project where I think it is about time to try new databases. \nSales department makes a CSV dump every week and I need to make a small scripting application that allow people form other departments mixing the information, mostly linking the records. I have all this solved, my problem is the speed, I am using just plain text files for all this and unsurprisingly it is very slow.\nI thought about using mysql, but then I need installing mysql in every desktop, sqlite is easier, but it is very slow. I do not need a full relational database, just some way of play with big amounts of data in a decent time.\nUpdate: I think I was not being very detailed about my database usage thus explaining my problem badly. I am working reading all the data ~900 Megas or more from a csv into a Python dictionary then working with it. My problem is storing and mostly reading the data quickly.\nMany thanks!","AnswerCount":9,"Available Count":7,"Score":0.022218565,"is_accepted":false,"ViewCount":11416,"Q_Id":2577967,"Users Score":1,"Answer":"Does the machine this process runs on have sufficient memory and bandwidth to handle this efficiently?  Putting MySQL on a slow machine and recoding the tool to use MySQL rather than text files could potentially be far more costly than simply adding memory or upgrading the machine.","Q_Score":15,"Tags":"python,database,nosql,data-mining","A_Id":2578751,"CreationDate":"2010-04-05T10:59:00.000","Title":"Best DataMining Database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm writing a database of all DVDs I have at home.\nOne of the fields, actors, I would like it to be a set of values from an other table, which is storing actors. So for every film I want to store a list of actors, all of which selected from a list of actors, taken from a different table.\nIs it possible? How do I do this? It would be a set of foreign keys basically.\nI'm using a MySQL database for a Django application (python), so any hint in SQL or Python would be much appreciated.\nI hope the question is clear,\nmany thanks.","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":85,"Q_Id":2579866,"Users Score":1,"Answer":"The answer is clear too. You will need not a field, but another films_actors table. This table would act as your field, but much more reliable. This is called many-to-many relation.","Q_Score":3,"Tags":"python,sql,mysql,django-models","A_Id":2579922,"CreationDate":"2010-04-05T17:31:00.000","Title":"Using set with values from a table","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a set of .csv files that I want to process. It would be far easier to process it with SQL queries. I wonder if there is some way to load a .csv file and use SQL language to look into it with a scripting language like python or ruby. Loading it with something similar to ActiveRecord would be awesome. \nThe problem is that I don't want to have to run a database somewhere prior to running my script. I souldn't have additionnal installations needed outside of the scripting language and some modules.\nMy question is which language and what modules should I use for this task. I looked around and can't find anything that suits my need. Is it even possible?","AnswerCount":7,"Available Count":1,"Score":0.0855049882,"is_accepted":false,"ViewCount":12118,"Q_Id":2580497,"Users Score":3,"Answer":"CSV files are not databases--they have no indices--and any SQL simulation you imposed upon them would amount to little more than searching through the entire thing over and over again.","Q_Score":26,"Tags":"python,sql,database,sqlite,sqlalchemy","A_Id":2580542,"CreationDate":"2010-04-05T19:10:00.000","Title":"Database on the fly with scripting languages","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I built an inventory database where ISBN numbers are the primary keys for the items. This worked great for a while as the items were books. Now I want to add non-books. some of the non-books have EANs or ISSNs, some do not.\nIt's in PostgreSQL with django apps for the frontend and JSON api, plus a few supporting python command-line tools for management. the items in question are mostly books and artist prints, some of which are self-published.\nWhat is nice about using ISBNs as primary keys is that in on top of relational integrity, you get lots of handy utilities for validating ISBNs, automatically looking up missing or additional information on the book items, etcetera, many of which I've taken advantage. some such tools are off-the-shelf (PyISBN, PyAWS etc) and some are hand-rolled -- I tried to keep all of these parts nice and decoupled, but you know how things can get.\nI couldn't find anything online about 'private ISBNs' or 'self-assigned ISBNs' but that's the sort of thing I was interested in doing. I doubt that's what I'll settle on, since there is already an apparent run on ISBN numbers.\nshould I retool everything for EAN numbers, or migrate off ISBNs as primary keys in general? if anyone has any experience with working with these systems, I'd love to hear about it, your advice is most welcome.","AnswerCount":4,"Available Count":2,"Score":0.1488850336,"is_accepted":false,"ViewCount":1516,"Q_Id":2610000,"Users Score":3,"Answer":"I don't know postgres but normally ISBM would be a unique index key but not the primary. It's better to have an integer as primary\/foreign key. That way you only need to add a new field EAN\/ISSN as nullable.","Q_Score":2,"Tags":"python,django,postgresql,isbn","A_Id":2610094,"CreationDate":"2010-04-09T18:45:00.000","Title":"ISBNs are used as primary key, now I want to add non-book things to the DB - should I migrate to EAN?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I built an inventory database where ISBN numbers are the primary keys for the items. This worked great for a while as the items were books. Now I want to add non-books. some of the non-books have EANs or ISSNs, some do not.\nIt's in PostgreSQL with django apps for the frontend and JSON api, plus a few supporting python command-line tools for management. the items in question are mostly books and artist prints, some of which are self-published.\nWhat is nice about using ISBNs as primary keys is that in on top of relational integrity, you get lots of handy utilities for validating ISBNs, automatically looking up missing or additional information on the book items, etcetera, many of which I've taken advantage. some such tools are off-the-shelf (PyISBN, PyAWS etc) and some are hand-rolled -- I tried to keep all of these parts nice and decoupled, but you know how things can get.\nI couldn't find anything online about 'private ISBNs' or 'self-assigned ISBNs' but that's the sort of thing I was interested in doing. I doubt that's what I'll settle on, since there is already an apparent run on ISBN numbers.\nshould I retool everything for EAN numbers, or migrate off ISBNs as primary keys in general? if anyone has any experience with working with these systems, I'd love to hear about it, your advice is most welcome.","AnswerCount":4,"Available Count":2,"Score":0.049958375,"is_accepted":false,"ViewCount":1516,"Q_Id":2610000,"Users Score":1,"Answer":"A simple solution (although arguably whether good) would be to use (isbn,title) or (isbn,author) which should pretty much guarantee uniqueness. Ideology is great but practicality also serves a purpose.","Q_Score":2,"Tags":"python,django,postgresql,isbn","A_Id":2614029,"CreationDate":"2010-04-09T18:45:00.000","Title":"ISBNs are used as primary key, now I want to add non-book things to the DB - should I migrate to EAN?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Does anyone know if Python's shelve module uses memory-mapped IO?\nMaybe that question is a bit misleading.  I realize that shelve uses an underlying dbm-style module to do its dirty work.   What are the chances that the underlying module uses mmap?\nI'm prototyping a datastore, and while I realize premature optimization is generally frowned upon, this could really help me understand the trade-offs involved in my design.","AnswerCount":2,"Available Count":2,"Score":0.2913126125,"is_accepted":false,"ViewCount":902,"Q_Id":2618921,"Users Score":3,"Answer":"I'm not sure what you're trying to learn by asking this question, since you already seem to know the answer: it depends on the actual dbm store being used. Some of them will use mmap -- I expect everything but dumbdbm to use mmap -- but so what? The overhead in shelve is almost certainly not in the mmap-versus-fileIO choice, but in the pickling operation. You can't mmap the dbm file sensibly yourself in either case, as the dbm module may have its own fancy locking (and it may not be a single file anyway, like when it uses bsddb.)\nIf you're just looking for inspiration for your own datastore, well, don't look at shelve, since all it does is pickle-and-pass-along to another datastore.","Q_Score":2,"Tags":"python,mmap,shelve,dbm","A_Id":2618963,"CreationDate":"2010-04-11T22:18:00.000","Title":"Does Python's shelve module use memory-mapped IO?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Does anyone know if Python's shelve module uses memory-mapped IO?\nMaybe that question is a bit misleading.  I realize that shelve uses an underlying dbm-style module to do its dirty work.   What are the chances that the underlying module uses mmap?\nI'm prototyping a datastore, and while I realize premature optimization is generally frowned upon, this could really help me understand the trade-offs involved in my design.","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":902,"Q_Id":2618921,"Users Score":4,"Answer":"Existing dbm implementations in the Python standard library all use \"normal\" I\/O, not memory mapping.  You'll need to code your own dbmish implementation with memory mapping, and integrate it with shelve (directly, or, more productively, through anydbm).","Q_Score":2,"Tags":"python,mmap,shelve,dbm","A_Id":2618981,"CreationDate":"2010-04-11T22:18:00.000","Title":"Does Python's shelve module use memory-mapped IO?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm from Brazil and study at FATEC (college located in Brazil).\nI'm trying to learn about AppEngine.\nNow, I'm trying to load a large database from MySQL to AppEngine to perform some queries, but I don't know how i can do it. I did some testing with CSV files,but is there any way to perform the direct import from MySQL?\nThis database is from Pentaho BI Server (www.pentaho.com).\nThank you for your attention.\nRegards,\nDaniel Naito","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1278,"Q_Id":2650499,"Users Score":0,"Answer":"If you're using Pentaho BI Server as your data source, why don't you consider using Pentaho Data Integration (ETL tool) to move the data over? At the very least PDI automate any movement of data between your data source and any AppEngine bulk loader tool (it can easily trigger any app with a shell step).","Q_Score":0,"Tags":"python,mysql,google-app-engine,bulk-load","A_Id":2662880,"CreationDate":"2010-04-16T03:57:00.000","Title":"MySQL to AppEngine","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"There is a m2m relation in my models,  User and Role.   \nI want to merge a role, but i DO NOT want this merge has any effect on user and role relation-ship.  Unfortunately, for some complicate reason, role.users if not empty.  \nI tried to set role.users = None, but SA complains None is not a list.\nAt this moment, I use sqlalchemy.orm.attributes.del_attribute, but I don't know if it's provided for this purpose.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":396,"Q_Id":2665253,"Users Score":0,"Answer":"You'd better fix your code to avoid setting role.users for the item you are going to merge. But there is another way - setting cascade='none' for this relation. Then you lose an ability to save relationship from Role side, you'll have to save User with roles attribute set.","Q_Score":0,"Tags":"python,sqlalchemy","A_Id":2667004,"CreationDate":"2010-04-19T05:01:00.000","Title":"In SqlAlchemy, how to ignore m2m relationship attributes when merge?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am looking for a way to connect to a MS Analysis Services OLAP cube, run MDX queries, and pull the results into Python. In other words, exactly what Excel does. Is there a solution in Python that would let me do that?\nSomeone with a similar question going pointed to Django's ORM. As much as I like the framework, this is not what I am looking for. I am also not looking for a way to pull rows and aggregate them -- that's what Analysis Services is for in the first place.\nIdeas? Thanks.","AnswerCount":3,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":14434,"Q_Id":2670887,"Users Score":4,"Answer":"I am completely ignorant about Python, but if it can call DLLs then it ought to be able to use Microsoft's ADOMD object. This is the best option I can think of.\nYou could look at Office Web Components (OWC) as that has a OLAP control than can be embedded on a web page. I think you can pass MDX to it, but perhaps you want Python to see the results too, which I don't think it allows.\nOtherwise perhaps you can build your own 'proxy' in another language. This program\/webpage could accept MDX in, and return you XML showing the results. Python could then consume this XML.","Q_Score":7,"Tags":"python,database,olap","A_Id":2743692,"CreationDate":"2010-04-19T21:05:00.000","Title":"MS Analysis Services OLAP API for Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am using python in Linux to automate an excel. I have finished writing data into excel by using pyexcelerator package. \nNow comes the real challenge. I have to add another tab to the existing sheet and that tab should contain the macro run in the first tab. All these things should be automated. I Googled a lot and found win32come to do a job in macro, but that was only for windows.\nAnyone have any idea of how to do this, or can you guide me with few suggestions.","AnswerCount":3,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":1093,"Q_Id":2697701,"Users Score":0,"Answer":"Excel Macros are per sheets, so, I am afraid, you need to copy the macros explicitly if you created new sheet, instead of copying existing sheet to new one.","Q_Score":1,"Tags":"python,linux,excel,automation","A_Id":2697769,"CreationDate":"2010-04-23T10:08:00.000","Title":"Automating Excel macro using python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am using python in Linux to automate an excel. I have finished writing data into excel by using pyexcelerator package. \nNow comes the real challenge. I have to add another tab to the existing sheet and that tab should contain the macro run in the first tab. All these things should be automated. I Googled a lot and found win32come to do a job in macro, but that was only for windows.\nAnyone have any idea of how to do this, or can you guide me with few suggestions.","AnswerCount":3,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":1093,"Q_Id":2697701,"Users Score":0,"Answer":"Maybe manipulating your .xls with Openoffice and pyUno is a better way. Way more powerful.","Q_Score":1,"Tags":"python,linux,excel,automation","A_Id":3596123,"CreationDate":"2010-04-23T10:08:00.000","Title":"Automating Excel macro using python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Last night I upgraded my machine to Ubuntu 10.04 from 9.10.\nIt seems to have cluttered my python module. Whenever I run python manage.py I get this error:\n\nImportError: No module named postgresql_psycopg2.base\n\nCan any one throw any light on this?","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1092,"Q_Id":2711737,"Users Score":1,"Answer":"Couple of things.  I ran into the same kind of error - but for a different thing (ie. \"ImportError: No module named django\") when I reinstalled some software. Essentially, it messed up my Python paths.\nSo, you're issue is very reminiscent of the one I had. The issue for me ended up being that the installed I used altered my .profile file (.bash_profile on some systems) in my home directory that messed up the Path environment variable to point to the incorrect Python binaries.  This includes, of course, pointing to the wrong site-packages (where many Python extensions are installed). \nTo verify this, I used two Linux shell commands that saved the day for me where:\n\"which python\" and \"whereis python\" \nThe first tells you which version of Python you are running, and the second tells you where it is located.  This is important since you can have multiple versions of Python installed on your machine.\nHopefully, this is will help you troubleshoot your issue. You may also want to try \"$echo Path\" (at the command line \/ terminal) to see where the paths to resolve commands.\nYou can fix your issue either by:\n1- fixing your Path variable, and exporting Path, in .profile (or .bash_profile)\n2- creating a sym link to the appropriate Python binary \nGood luck :)\n~Aki","Q_Score":2,"Tags":"python,django,postgresql,psycopg2","A_Id":4505549,"CreationDate":"2010-04-26T07:33:00.000","Title":"Some problem with postgres_psycopg2","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I want to use sqlite memory database for all my testing and Postgresql for my development\/production server.\nBut the SQL syntax is not same in both dbs. for ex: SQLite has autoincrement, and Postgresql has serial \nIs it easy to port the SQL script from sqlite to postgresql... what are your solutions?\nIf you want me to use standard SQL, how should I go about generating primary key in both the databases?","AnswerCount":3,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":2892,"Q_Id":2716847,"Users Score":12,"Answer":"Don't do it. Don't test in one environment and release and develop in another.  Your asking for buggy software using this process.","Q_Score":5,"Tags":"python,sqlite,postgresql,sqlalchemy","A_Id":2721100,"CreationDate":"2010-04-26T20:59:00.000","Title":"SQLAlchemy - SQLite for testing and Postgresql for development - How to port?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I want to use sqlite memory database for all my testing and Postgresql for my development\/production server.\nBut the SQL syntax is not same in both dbs. for ex: SQLite has autoincrement, and Postgresql has serial \nIs it easy to port the SQL script from sqlite to postgresql... what are your solutions?\nIf you want me to use standard SQL, how should I go about generating primary key in both the databases?","AnswerCount":3,"Available Count":2,"Score":1.0,"is_accepted":false,"ViewCount":2892,"Q_Id":2716847,"Users Score":19,"Answer":"My suggestion would be: don't.   The capabilities of Postgresql are far beyond what SQLite can provide, particularly in the areas of date\/numeric support, functions and stored procedures, ALTER support, constraints, sequences, other types like UUID, etc., and even using various SQLAlchemy tricks to try to smooth that over will only get you a slight bit further.  In particular date and interval arithmetic are totally different beasts on the two platforms, and SQLite has no support for precision decimals (non floating-point) the way PG does.   PG is very easy to install on every major OS and life is just easier if you go that route.","Q_Score":5,"Tags":"python,sqlite,postgresql,sqlalchemy","A_Id":2717071,"CreationDate":"2010-04-26T20:59:00.000","Title":"SQLAlchemy - SQLite for testing and Postgresql for development - How to port?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have searched high and low for an answer to why query results returned in this format and how to convert to a list.\ndata = cursor.fetchall()\nWhen I print data, it results in:\n(('car',), ('boat',), ('plane',), ('truck',))\nI want to have the results in a list as [\"car\", \"boat\", \"plane\", \"truck\"]","AnswerCount":3,"Available Count":1,"Score":0.0665680765,"is_accepted":false,"ViewCount":1007,"Q_Id":2723432,"Users Score":1,"Answer":"The result for fetchall() returns an array of rows, where each row is an array with one value per column.\nEven if you are selecting only one column, you will still get an array of arrays, but only one value for each row.","Q_Score":3,"Tags":"python,mysql,list,recordset","A_Id":2723548,"CreationDate":"2010-04-27T17:21:00.000","Title":"Why is recordset result being returned in this way for Python database query?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a django project that uses a sqlite database that can be written to by an external tool. The text is supposed to be UTF-8, but in some cases there will be errors in the encoding. The text is from an external source, so I cannot control the encoding. Yes, I know that I could write a \"wrapping layer\" between the external source and the database, but I prefer not having to do this, especially since the database already contains a lot of \"bad\" data.\nThe solution in sqlite is to change the text_factory to something like:\n\nlambda x: unicode(x, \"utf-8\", \"ignore\")\n\nHowever, I don't know how to tell the Django model driver this.\nThe exception I get is:\n\n'Could not decode to UTF-8 column 'Text' with text'\nin\n\/var\/lib\/python-support\/python2.5\/django\/db\/backends\/sqlite3\/base.py in execute\n\nSomehow I need to tell the sqlite driver not to try to decode the text as UTF-8 (at least not using the standard algorithm, but it needs to use my fail-safe variant).","AnswerCount":6,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":4701,"Q_Id":2744632,"Users Score":0,"Answer":"Incompatible Django version. Check Django version for solving this error first. I was running on Django==3.0.8 and it was producing an error. Than I ran virtualenv where I have Django==3.1.2 and the error was removed.","Q_Score":6,"Tags":"python,django,sqlite,pysqlite","A_Id":64263492,"CreationDate":"2010-04-30T13:00:00.000","Title":"Change text_factory in Django\/sqlite","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm curious about how others have approached the problem of maintaining and synchronizing database changes across many (10+) developers without a DBA? What I mean, basically, is that if someone wants to make a change to the database, what are some strategies to doing that? (i.e. I've created a 'Car' model and now I want to apply the appropriate DDL to the database, etc..)\nWe're primarily a Python shop and our ORM is SQLAlchemy. Previously, we had written our models in such a way to create the models using our ORM, but we recently ditched this because:\n\nWe couldn't track changes using the ORM\nThe state of the ORM wasn't in sync with the database (e.g. lots of differences primarily related to indexes and unique constraints)\nThere was no way to audit database changes unless the developer documented the database change via email to the team.\n\nOur solution to this problem was to basically have a \"gatekeeper\" individual who checks every change into the database and applies all accepted database changes to an accepted_db_changes.sql file, whereby the developers who need to make any database changes put their requests into a proposed_db_changes.sql file. We check this file in, and, when it's updated, we all apply the change to our personal database on our development machine. We don't create indexes or constraints on the models, they are applied explicitly on the database.\nI would like to know what are some strategies to maintain database schemas and if ours seems reasonable.\nThanks!","AnswerCount":4,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":930,"Q_Id":2748946,"Users Score":2,"Answer":"The solution is rather administrative then technical :)\nThe general rule is easy, there should only be tree-like dependencies in the project:\n- There should always be a single master source of schema, stored together with the project source code in the version control\n- Everything affected by the change in the master source should be automatically re-generated every time the master source is updated, no manual intervention allowed never, if automatic generation does not work -- fix either master source or generator, don't manually update the source code\n- All re-generations should be performed by the same person who updated the master source and all changes including the master source change should be considered a single transaction (single source control commit, single build\/deployment for every affected environment including DBs update)\nBeing enforced, this gives 100% reliable result.\nThere are essentially 3 possible choices of the master source\n1) DB metadata, sources are generated after DB update by some tool connecting to the live DB\n2) Source code, some tool is generating SQL scheme from the sources, annotated in a special way and then SQL is run on the DB\n3) DDL, both SQL schema and source code are generated by some tool\n4) some other description is used (say a text file read by a special Perl script generating both SQL schema and the source code)\n1,2,3 are equally good, providing that the tool you need exists and is not over expensive\n4 is a universal approach, but it should be applied from the very beginning of the project and has an overhead of couple thousands lines of code in a strange language to maintain","Q_Score":9,"Tags":"python,database,postgresql,sqlalchemy,database-schema","A_Id":2768187,"CreationDate":"2010-05-01T04:57:00.000","Title":"What are some strategies for maintaining a common database schema with a team of developers and no DBA?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm writing an Fast-CGI application that makes use of sqlAlchemy & MySQL for persistent data storage.  I have no problem connecting to the DB and setting up ORM (so that tables get mapped to classes); I can even add data to tables (in memory).  \nBut, as soon as I query the DB (and push any changes from memory to storage) I get a 500 Internal Server Error and my error.log records malformed header from script. Bad header=FROM tags : index.py, when tags is the table name.\nAny idea what could be causing this?\nAlso, I don't think it matters, but its a Linux development server talking to an off-site (across the country) MySQL server.","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":921,"Q_Id":2751957,"Users Score":2,"Answer":"Looks like SQLalchemy is pushing or echoing the query to your output (where fast-cgi) is instead looking for headers, then body.  Maybe setting sqlalchemy.echo to False can help.","Q_Score":0,"Tags":"python,mysql,apache,sqlalchemy,fastcgi","A_Id":2751989,"CreationDate":"2010-05-01T23:44:00.000","Title":"Python fCGI + sqlAlchemy = malformed header from script. Bad header=FROM tags : index.py","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"How would one go about authenticating against a single db using Python and openfire?  Is there a simple module that will do this?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":94,"Q_Id":2752047,"Users Score":0,"Answer":"Openfire uses a SQL database. So talking to the database from python is probably the easiest way.\nYou could also try to connect\/authenticate via XMPP - there's probably an xmpp library for python somewhere.","Q_Score":0,"Tags":"python,database,openfire","A_Id":2766455,"CreationDate":"2010-05-02T00:35:00.000","Title":"I need to authenticate against one db with python and openfire. How do I do this?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am trying to access a MySQL database with python through Pydev Eclipse. I have installed the necessary files to access MysQL from python and I can access the database only when I write code in Python IDLE environment and run it from command prompt. However I am not able to run my applications from Pydev. \nwhen I use this \"import MysqlDB\"  i get an error, but in IDLE no errors and my code runs very smoothly.\nDoes anyone know were the problem is?\nThanks","AnswerCount":3,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":6768,"Q_Id":2775095,"Users Score":0,"Answer":"If the connector works in the IDLE but not in PyDev. Open Eclipse preferences, open PyDev directory and go to interpreter screen. Remove the interpreter and add it again from the location on your computer (Usually C drive). Close and reload Eclipse and now it should work.","Q_Score":2,"Tags":"python,mysql,eclipse,pydev,mysql-python","A_Id":23798598,"CreationDate":"2010-05-05T16:36:00.000","Title":"Using MySQL in Pydev Eclipse","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":0},{"Question":"I am trying to access a MySQL database with python through Pydev Eclipse. I have installed the necessary files to access MysQL from python and I can access the database only when I write code in Python IDLE environment and run it from command prompt. However I am not able to run my applications from Pydev. \nwhen I use this \"import MysqlDB\"  i get an error, but in IDLE no errors and my code runs very smoothly.\nDoes anyone know were the problem is?\nThanks","AnswerCount":3,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":6768,"Q_Id":2775095,"Users Score":0,"Answer":"Posting Answer in case URL changed in future\nFrom Eclipse, choose Window \/ Preferences \/ PyDev \/ Interpreters \/ Python Interpreter, click on Manage with pip and enter the command:\ninstall mysql-connector-python","Q_Score":2,"Tags":"python,mysql,eclipse,pydev,mysql-python","A_Id":70125088,"CreationDate":"2010-05-05T16:36:00.000","Title":"Using MySQL in Pydev Eclipse","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":0},{"Question":"If so, how can I do this?","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":848,"Q_Id":2810235,"Users Score":1,"Answer":"when you create a prepared statement, the \"template\" SQL code is sent to the DBMS already, which compiles it into an expression tree. When you pass the values, the corresponding library (python sqlite3 module in your case) doesn't merge the values into the statement. The DBMS does.\nIf you still want to produce a normal SQL string, you can use string replace functions to replace the placeholders by the values (after escaping them).\nWhat do you need this for?","Q_Score":0,"Tags":"python,sqlite,pysqlite","A_Id":2810300,"CreationDate":"2010-05-11T11:28:00.000","Title":"Can I get the raw SQL generated by a prepared statement in Python\u2019s sqlite3 module?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"If so, how can I do this?","AnswerCount":2,"Available Count":2,"Score":0.1973753202,"is_accepted":false,"ViewCount":848,"Q_Id":2810235,"Users Score":2,"Answer":"When executing a prepared statement, no new SQL is generated.\nThe idea of prepared statements is that the SQL query and its data are transmitted separately (that's why you don't have to escape any arguments) - the query is most likely only stored in an optimized form after preparing it.","Q_Score":0,"Tags":"python,sqlite,pysqlite","A_Id":2810250,"CreationDate":"2010-05-11T11:28:00.000","Title":"Can I get the raw SQL generated by a prepared statement in Python\u2019s sqlite3 module?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a large sql dump file ... with multiple CREATE TABLE and INSERT INTO statements.  Is there any way to load these all into a SQLAlchemy sqlite database at once.  I plan to use the introspected ORM from sqlsoup after I've created the tables.  However, when I use the engine.execute() method it complains: sqlite3.Warning: You can only execute one statement at a time.\nIs there a way to work around this issue.  Perhaps splitting the file with a regexp or some kind of parser, but I don't know enough SQL to get all of the cases for the regexp.\nAny help would be greatly appreciated.\nWill\nEDIT:\nSince this seems important ... The dump file was created with a MySQL database and so it has quite a few commands\/syntax that sqlite3 does not understand correctly.","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":3406,"Q_Id":2824244,"Users Score":2,"Answer":"\"or some kind of parser\"\nI've found MySQL to be a great parser for MySQL dump files :)\nYou said it yourself: \"so it has quite a few commands\/syntax that sqlite3 does not understand correctly.\" Clearly then, SQLite is not the tool for this task.\nAs for your particular error: without context (i.e. a traceback) there's nothing I can say about it. Martelli or Skeet could probably reach across time and space and read your interpreter's mind, but me, not so much.","Q_Score":5,"Tags":"python,sql,sqlalchemy","A_Id":2828580,"CreationDate":"2010-05-13T03:23:00.000","Title":"How can I load a sql \"dump\" file into sql alchemy","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a large sql dump file ... with multiple CREATE TABLE and INSERT INTO statements.  Is there any way to load these all into a SQLAlchemy sqlite database at once.  I plan to use the introspected ORM from sqlsoup after I've created the tables.  However, when I use the engine.execute() method it complains: sqlite3.Warning: You can only execute one statement at a time.\nIs there a way to work around this issue.  Perhaps splitting the file with a regexp or some kind of parser, but I don't know enough SQL to get all of the cases for the regexp.\nAny help would be greatly appreciated.\nWill\nEDIT:\nSince this seems important ... The dump file was created with a MySQL database and so it has quite a few commands\/syntax that sqlite3 does not understand correctly.","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":3406,"Q_Id":2824244,"Users Score":0,"Answer":"The SQL recognized by MySQL and the SQL in SQLite are quite different.  I suggest dumping the data of each table individually, then loading the data into equivalent tables in SQLite.\nCreate the tables in SQLite manually, using a subset of the \"CREATE TABLE\" commands given in your raw-dump file.","Q_Score":5,"Tags":"python,sql,sqlalchemy","A_Id":2828621,"CreationDate":"2010-05-13T03:23:00.000","Title":"How can I load a sql \"dump\" file into sql alchemy","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I want to delete all records in a mysql db except the record id's I have in a list.  The length of that list can vary and could easily contain 2000+ id's, ...\nCurrently I convert my list to a string so it fits in something like this:\ncursor.execute(\"\"\"delete from table where id not in (%s)\"\"\",(list))\nWhich doesn't feel right and I have no idea how long list is allowed to be, ....\nWhat's the most efficient way of doing this from python?\nAltering the structure of table with an extra field to mark\/unmark records for deletion would be great but not an option.\nHaving a dedicated table storing the id's would indeed be helpful then this can just be done through a sql query... but I would really like to avoid these options if possible.\nThanks,","AnswerCount":4,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":3327,"Q_Id":2826387,"Users Score":0,"Answer":"I'd add a \"todelete tinyint(1) not null default 1\" column to the table, update it to 0 for those id's which have to be kept, then delete from table where todelete;. It's faster than not in.\nOr, create a table with the same structure as yours, insert the kept rows there and rename tables. Then, drop the old one.","Q_Score":3,"Tags":"python,mysql","A_Id":2827845,"CreationDate":"2010-05-13T11:37:00.000","Title":"delete all records except the id I have in a python list","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Currently, i am querying with this code: meta.Session.query(Label).order_by(Label.name).all()\nand it returns me objects sorted by Label.name in this manner ['1','7','1a','5c'].  Is there a way i can have the objects returned in the order with their Label.name sorted like this ['1','1a','5c','7']\nThanks!","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":1746,"Q_Id":2863748,"Users Score":1,"Answer":"Sorting is done by the database. If you database doesn't support natural sorting your are out of luck and have to sort your rows manually after retrieving them via sqlalchemy.","Q_Score":1,"Tags":"python,sqlalchemy","A_Id":2863830,"CreationDate":"2010-05-19T07:59:00.000","Title":"sqlalchemy natural sorting","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a relatively extensive sqlite database that I'd like to import into my Google App Engine python app.\nI've created my models using the appengine API which are close, but not quite identical to the existing schema. I've written an import script to load the data from sqlite and create\/save new appengine objects, but the appengine environment blocks me from accessing the sqlite library.  This script is only to be run on my local app engine instance, and from there I hope to push the data to google.\nAm I approaching this problem the wrong way, or is there a way to import the sqlite library while running in the local instance's environment?","AnswerCount":4,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":2231,"Q_Id":2870379,"Users Score":0,"Answer":"I have not had any trouble importing pysqlite2, reading data, then transforming it and writing it to AppEngine using the remote_api.  \nWhat error are you seeing?","Q_Score":5,"Tags":"python,google-app-engine,sqlite","A_Id":2873946,"CreationDate":"2010-05-20T00:47:00.000","Title":"Importing Sqlite data into Google App Engine","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I am working on a personal project where I need to manipulate values in a database-like format.\nUp until now I have been using dictionaries, tuples, and lists to store and consult those values.\nI am thinking about starting to use SQL to manipulate those values, but I don't know if it's worth the effort, because I don't know anything about SQL, and I don't want to use something that won't bring me any benefits (if I can do it in a simpler way, I don't want to complicate things)\nIf I am only storing and consulting values, what would be the benefit of using SQL? \nPS: the numbers of rows goes between 3 and 100 and the number of columns is around 10 (some may have 5 some may have 10 etc.)","AnswerCount":3,"Available Count":3,"Score":0.1325487884,"is_accepted":false,"ViewCount":291,"Q_Id":2870815,"Users Score":2,"Answer":"No, I think you just stick to dictionaries or tuples if you only have rows around 100","Q_Score":1,"Tags":"python,sql,database","A_Id":2870821,"CreationDate":"2010-05-20T03:24:00.000","Title":"Python and database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am working on a personal project where I need to manipulate values in a database-like format.\nUp until now I have been using dictionaries, tuples, and lists to store and consult those values.\nI am thinking about starting to use SQL to manipulate those values, but I don't know if it's worth the effort, because I don't know anything about SQL, and I don't want to use something that won't bring me any benefits (if I can do it in a simpler way, I don't want to complicate things)\nIf I am only storing and consulting values, what would be the benefit of using SQL? \nPS: the numbers of rows goes between 3 and 100 and the number of columns is around 10 (some may have 5 some may have 10 etc.)","AnswerCount":3,"Available Count":3,"Score":1.2,"is_accepted":true,"ViewCount":291,"Q_Id":2870815,"Users Score":7,"Answer":"SQL is nice and practical for many kinds of problems, is not that hard to learn at a simple \"surface\" level, and can be very handy to use in Python with its embedded sqlite.  But if you don't know SQL, have no intrinsic motivation to learn it right now, and are already doing all you need to do to\/with your data without problems, then the immediate return on the investment of learning SQL (relatively small as that investment may be) seem like it would be pretty meager indeed for you.","Q_Score":1,"Tags":"python,sql,database","A_Id":2870832,"CreationDate":"2010-05-20T03:24:00.000","Title":"Python and database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am working on a personal project where I need to manipulate values in a database-like format.\nUp until now I have been using dictionaries, tuples, and lists to store and consult those values.\nI am thinking about starting to use SQL to manipulate those values, but I don't know if it's worth the effort, because I don't know anything about SQL, and I don't want to use something that won't bring me any benefits (if I can do it in a simpler way, I don't want to complicate things)\nIf I am only storing and consulting values, what would be the benefit of using SQL? \nPS: the numbers of rows goes between 3 and 100 and the number of columns is around 10 (some may have 5 some may have 10 etc.)","AnswerCount":3,"Available Count":3,"Score":0.1325487884,"is_accepted":false,"ViewCount":291,"Q_Id":2870815,"Users Score":2,"Answer":"SQL is useful in many applications. But it is an overkill in this case. You can easily store your data in CSV, pickle or JSON format. Get this job done in 5 minutes and then learn SQL when you have time.","Q_Score":1,"Tags":"python,sql,database","A_Id":2871090,"CreationDate":"2010-05-20T03:24:00.000","Title":"Python and database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am trying to install postgrepsql to cygwin on a windows 7 machine and want it to work with django. \nAfter built and installed postgrepsql in cygwin, I built and installed psycopg2 in cygwin as well and got no error, but when use it in python with cygwin, I got the \"no such process\" error:\n\n\n\nimport psycopg2\n      Traceback (most recent call last):\n      File \"\", line 1, in \n      File \"\/usr\/lib\/python2.5\/site-packages\/psycopg2\/init.py\", line 60, in \n      from _psycopg import BINARY, NUMBER, STRING, DATETIME, ROWID\n      ImportError: No such process\n\n\n\nany clues?\nThanks!\nJerry","AnswerCount":4,"Available Count":2,"Score":0.049958375,"is_accepted":false,"ViewCount":1204,"Q_Id":2879246,"Users Score":1,"Answer":"In my case, I had to reinstall libpq5.","Q_Score":0,"Tags":"python,django,postgresql,psycopg2","A_Id":14780956,"CreationDate":"2010-05-21T02:34:00.000","Title":"psycopg2 on cygwin: no such process","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am trying to install postgrepsql to cygwin on a windows 7 machine and want it to work with django. \nAfter built and installed postgrepsql in cygwin, I built and installed psycopg2 in cygwin as well and got no error, but when use it in python with cygwin, I got the \"no such process\" error:\n\n\n\nimport psycopg2\n      Traceback (most recent call last):\n      File \"\", line 1, in \n      File \"\/usr\/lib\/python2.5\/site-packages\/psycopg2\/init.py\", line 60, in \n      from _psycopg import BINARY, NUMBER, STRING, DATETIME, ROWID\n      ImportError: No such process\n\n\n\nany clues?\nThanks!\nJerry","AnswerCount":4,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":1204,"Q_Id":2879246,"Users Score":0,"Answer":"Why? There is native psycopg2 for Win.","Q_Score":0,"Tags":"python,django,postgresql,psycopg2","A_Id":2885759,"CreationDate":"2010-05-21T02:34:00.000","Title":"psycopg2 on cygwin: no such process","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"After running a bunch of simulations I'm going to be outputting the results into a table created using SQLAlchemy. I plan to use this data to generate statistics - mean and variance being key. These, in turn, will be used to generate some graphs - histograms\/line graphs, pie-charts and box-and-whisker plots specifically.\nI'm aware of the Python graphing libraries like matplotlib. The thing is, I'm not sure how to have this integrate with the information contained within the database tables. \nAny suggestions on how to make these two play with each other?\nThe main problem is that I'm not sure how to supply the information as \"data sets\" to the graphing library.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1415,"Q_Id":2890564,"Users Score":1,"Answer":"It looks like matplotlib takes simple python data types -- lists of numbers, etc, so you'll be need to write custom code to massage what you pull out of mysql\/sqlalchemy for input into the graphing functions...","Q_Score":1,"Tags":"python,matplotlib,sqlalchemy","A_Id":2891001,"CreationDate":"2010-05-23T03:10:00.000","Title":"How to generate graphs and statistics from SQLAlchemy tables?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"If you wanted to manipulate the data in a table in a postgresql database using some python (maybe running a little analysis on the result set using scipy) and then wanted to export that data back into another table in the same database, how would you go about the implementation?\nIs the only\/best way to do this to simply run the query, have python store it in an array, manipulate the array in python and then run another sql statement to output to the database?\nI'm really just asking, is there a more efficient way to deal with the data?\nThanks,\nIan","AnswerCount":7,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1582,"Q_Id":2905097,"Users Score":0,"Answer":"I agree with the SQL Alchemy suggestions or using Django's ORM.  Your needs seem to simple for PL\/Python to be used.","Q_Score":4,"Tags":"python,postgresql","A_Id":2906866,"CreationDate":"2010-05-25T13:35:00.000","Title":"Python and Postgresql","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am in the planning stages of rewriting an Access db I wrote several years ago in a full fledged program.  I have very slight experience coding, but not enough to call myself a programmer by far.  I'll definitely be learning as I go, so I'd like to keep everything as simple as possible.  I've decided on Python and SQLite for my program, but I need help on my next decision.\nHere is my situation\n1) It'll be run locally on each machine, all Windows computers\n2) I would really like a nice looking GUI with colors, nice screens, menus, lists, etc, \n3) I'm thinking about using a browser interface because (a) from what I've read, browser apps \ncan look really great, and (b) I understand there are lots of free tools to assist in setting up the GUI\/GUI code with drag and drop tools, so that helps my \"keep it simple\" goal.\n4) I want the program to be totally portable so it runs completely from one single folder on a user's PC, with no installation(s) needed for it to run\n(If I did it as a browser app, isn't there the possibility that a user's browser settings could affect or break the app.  How likely is this?)  \nFor my situation, should\/could I make it a browser app?  What would be the pros and cons for my situation?","AnswerCount":8,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":5638,"Q_Id":2924231,"Users Score":0,"Answer":"You question is a little broad. I'll try to cover as much as I can. \nFirst, what I understood and my assumptions.\nIn your situation, the sqlite database is just a data store. Only one process (unless your application is multiprocess) will be accessing it so you won't need to worry about locking issues. The application doesn't need to communicate with other instances etc. over the network. It's a single desktop app. The platform is Windows. \nHere are some thoughts that come to mind. \n\nIf you develop an application in Python (either web based or desktop), you will have to package it as a single executable and distribute it to your users. They might have to install the Python runtime as well as any extra modules that you might be using.\nGuis are in my experience easier to develop using a standalone widget system than in a browser with Javascript. There are things like Pyjamas that make this better but it's still hard. \nWhile it's not impossible to have local web applications running on each computer, your real benefits come if you centralise it. One place to update software. No need to \"distribute\" etc. This of course entails that you use a more powerful database system and you can actually manage multiple users. It will also require that you worry about browser specific quirks. \n\nI'd go with a simple desktop app that uses a prepackaged toolkit (perhaps Tkinter which ships with Python). It's not the best of approaches but it will avoid problems for you. I'd also consider using a language that's more \"first class\" on windows like C# so that the runtimes and other things are already there. You requirement for a fancy GUI is secondary and I'd recommend that you get the functionality working fine before you focus on the bells and whistles. \nGood luck.","Q_Score":5,"Tags":"python,sqlite,browser","A_Id":2979467,"CreationDate":"2010-05-27T19:28:00.000","Title":"Python\/Sqlite program, write as browser app or desktop app?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"When using SQL Alchemy for abstracting your data access layer and using controllers as the way to access objects from that abstraction layer, how should joins be handled?\nSo for example, say you have an Orders controller class that manages Order objects such that it provides getOrder, saveOrder, etc methods and likewise a similar controller for User objects.   \nFirst of all do you even need these controllers?  Should you instead just treat SQL Alchemy as \"the\" thing for handling data access.  Why bother with object oriented controller stuff there when you instead have a clean declarative way to obtain and persist objects without having to write SQL directly either.  \nWell one reason could be that perhaps you may want to replace SQL Alchemy with direct SQL or Storm or whatever else.  So having controller classes there to act as an intermediate layer helps limit what would need to change then.  \nAnyway - back to the main question - so assuming you have these two controllers, now lets say you want the list of orders for a certain set of users meeting some criteria.  How do you go about doing this?  Generally you don't want the controllers crossing domains - the Orders controllers knows only about Orders and the User controller just about Users - they don't mess with each other.  You also don't want to go fetch all the Users that match and then feed a big list of user ids to the Orders controller to go find the matching Orders.  \nWhat's needed is a join.  Here's where I'm stuck - that seems to mean either the controllers must cross domains or perhaps they should be done away with altogether and you simply do the join via SQL Alchemy directly and get the resulting User and \/ or Order objects as needed.  Thoughts?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":430,"Q_Id":2933796,"Users Score":2,"Answer":"Controllers are meant to encapsulate features for your convienience. Not to bind your hands. If you want to join, simply join. Use the controller that you think is logically fittest to make the query.","Q_Score":1,"Tags":"python,model-view-controller,sqlalchemy,dns,controllers","A_Id":2934084,"CreationDate":"2010-05-29T04:25:00.000","Title":"SQL Alchemy MVC and cross controller joins","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have large amounts of data (a few terabytes) and accumulating... They are contained in many tab-delimited flat text files (each about 30MB). Most of the task involves reading the data and aggregating (summing\/averaging + additional transformations) over observations\/rows based on a series of predicate statements, and then saving the output as text, HDF5, or SQLite files, etc. I normally use R for such tasks but I fear this may be a bit large. Some candidate solutions are to \n\nwrite the whole thing in C (or\nFortran)\nimport the files (tables) into a\nrelational database directly and\nthen pull off chunks in R or Python\n(some of the transformations are not\namenable for pure SQL solutions)\nwrite the whole thing in Python\n\nWould (3) be a bad idea? I know you can wrap C routines in Python but in this case since there isn't anything computationally prohibitive (e.g., optimization routines that require many iterative calculations), I think I\/O may be as much of a bottleneck as the computation itself. Do you have any recommendations on further considerations or suggestions? Thanks\nEdit Thanks for your responses. There seems to be conflicting opinions about Hadoop, but in any case I don't have access to a cluster (though I can use several unnetworked machines)...","AnswerCount":8,"Available Count":4,"Score":0.049958375,"is_accepted":false,"ViewCount":5360,"Q_Id":2937619,"Users Score":2,"Answer":"When you say \"accumulating\" then solution (2) looks most suitable to problem.\nAfter initial load up to database you only update database with new files (daily, weekly? depends how often you need this).\nIn cases (1) and (3) you need to process files each time (what was stated earlier as most time\/resources-consuming), unless you find a way to stored results and update them with new files.\nYou could use R to process files from csv to, for example, SQLite database.","Q_Score":32,"Tags":"python,sql,r,large-files,large-data-volumes","A_Id":2942419,"CreationDate":"2010-05-30T05:06:00.000","Title":"large amount of data in many text files - how to process?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have large amounts of data (a few terabytes) and accumulating... They are contained in many tab-delimited flat text files (each about 30MB). Most of the task involves reading the data and aggregating (summing\/averaging + additional transformations) over observations\/rows based on a series of predicate statements, and then saving the output as text, HDF5, or SQLite files, etc. I normally use R for such tasks but I fear this may be a bit large. Some candidate solutions are to \n\nwrite the whole thing in C (or\nFortran)\nimport the files (tables) into a\nrelational database directly and\nthen pull off chunks in R or Python\n(some of the transformations are not\namenable for pure SQL solutions)\nwrite the whole thing in Python\n\nWould (3) be a bad idea? I know you can wrap C routines in Python but in this case since there isn't anything computationally prohibitive (e.g., optimization routines that require many iterative calculations), I think I\/O may be as much of a bottleneck as the computation itself. Do you have any recommendations on further considerations or suggestions? Thanks\nEdit Thanks for your responses. There seems to be conflicting opinions about Hadoop, but in any case I don't have access to a cluster (though I can use several unnetworked machines)...","AnswerCount":8,"Available Count":4,"Score":0.0996679946,"is_accepted":false,"ViewCount":5360,"Q_Id":2937619,"Users Score":4,"Answer":"With terabytes, you will want to parallelize your reads over many disks anyway; so might as well go straight into Hadoop.\nUse Pig or Hive to query the data; both have extensive support for user-defined transformations, so you should be able to implement what you need to do using custom code.","Q_Score":32,"Tags":"python,sql,r,large-files,large-data-volumes","A_Id":2937664,"CreationDate":"2010-05-30T05:06:00.000","Title":"large amount of data in many text files - how to process?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have large amounts of data (a few terabytes) and accumulating... They are contained in many tab-delimited flat text files (each about 30MB). Most of the task involves reading the data and aggregating (summing\/averaging + additional transformations) over observations\/rows based on a series of predicate statements, and then saving the output as text, HDF5, or SQLite files, etc. I normally use R for such tasks but I fear this may be a bit large. Some candidate solutions are to \n\nwrite the whole thing in C (or\nFortran)\nimport the files (tables) into a\nrelational database directly and\nthen pull off chunks in R or Python\n(some of the transformations are not\namenable for pure SQL solutions)\nwrite the whole thing in Python\n\nWould (3) be a bad idea? I know you can wrap C routines in Python but in this case since there isn't anything computationally prohibitive (e.g., optimization routines that require many iterative calculations), I think I\/O may be as much of a bottleneck as the computation itself. Do you have any recommendations on further considerations or suggestions? Thanks\nEdit Thanks for your responses. There seems to be conflicting opinions about Hadoop, but in any case I don't have access to a cluster (though I can use several unnetworked machines)...","AnswerCount":8,"Available Count":4,"Score":0.024994793,"is_accepted":false,"ViewCount":5360,"Q_Id":2937619,"Users Score":1,"Answer":"Yes. You are right! I\/O would cost most of your processing time. I don't suggest you to use distributed systems, like hadoop, for this task. \nYour task could be done in a modest workstation. I am not an Python expert, I think it has support for asynchronous programming. In F#\/.Net, the platform has well support for that. I was once doing an image processing job, loading 20K images on disk and transform them into feature vectors only costs several minutes in parallel. \nall in all, load and process your data in parallel and save the result in memory (if small), in database (if big).","Q_Score":32,"Tags":"python,sql,r,large-files,large-data-volumes","A_Id":2937660,"CreationDate":"2010-05-30T05:06:00.000","Title":"large amount of data in many text files - how to process?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have large amounts of data (a few terabytes) and accumulating... They are contained in many tab-delimited flat text files (each about 30MB). Most of the task involves reading the data and aggregating (summing\/averaging + additional transformations) over observations\/rows based on a series of predicate statements, and then saving the output as text, HDF5, or SQLite files, etc. I normally use R for such tasks but I fear this may be a bit large. Some candidate solutions are to \n\nwrite the whole thing in C (or\nFortran)\nimport the files (tables) into a\nrelational database directly and\nthen pull off chunks in R or Python\n(some of the transformations are not\namenable for pure SQL solutions)\nwrite the whole thing in Python\n\nWould (3) be a bad idea? I know you can wrap C routines in Python but in this case since there isn't anything computationally prohibitive (e.g., optimization routines that require many iterative calculations), I think I\/O may be as much of a bottleneck as the computation itself. Do you have any recommendations on further considerations or suggestions? Thanks\nEdit Thanks for your responses. There seems to be conflicting opinions about Hadoop, but in any case I don't have access to a cluster (though I can use several unnetworked machines)...","AnswerCount":8,"Available Count":4,"Score":1.2,"is_accepted":true,"ViewCount":5360,"Q_Id":2937619,"Users Score":14,"Answer":"(3) is not necessarily a bad idea -- Python makes it easy to process \"CSV\" file (and despite the C standing for Comma, tab as a separator is just as easy to handle) and of course gets just about as much bandwidth in I\/O ops as any other language.  As for other recommendations, numpy, besides fast computation (which you may not need as per your statements) provides very handy, flexible multi-dimensional arrays, which may be quite handy for your tasks; and the standard library module multiprocessing lets you exploit multiple cores for any task that's easy to parallelize (important since just about every machine these days has multi-cores;-).","Q_Score":32,"Tags":"python,sql,r,large-files,large-data-volumes","A_Id":2937630,"CreationDate":"2010-05-30T05:06:00.000","Title":"large amount of data in many text files - how to process?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Should I invest a lot of time trying to figure out an ORM style implementation, or is it still common to just stick with standard SQL queries in python\/pylons\/sqlalchemy?","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":1032,"Q_Id":2947172,"Users Score":8,"Answer":"ORMs are very popular, for several reasons -- e.g.: some people would rather not learn SQL, ORMs can ease porting among different SQL dialects, they may fit in more smoothly with the mostly-OOP style of applications, indeed might even ease some porting to non-SQL implementations (e.g, moving a Django app to Google App Engine would be much more work if the storage access layer relied on SQL statements -- as it relies on the ORM, that reduces, a bit, the needed porting work).\nSQLAlchemy is the most powerful ORM I know of for Python -- it lets you work at several possible levels, from a pretty abstract declarative one all the way down to injecting actual SQL in some queries where your profiling work has determined it makes a big difference (I think most people use it mostly at the intermediate level where it essentially mediates between OOP and relational styles, just like other ORMs).\nYou haven't asked for my personal opinion in the matter, which is somewhat athwart of the popular one I summarized above -- I've never really liked \"code generators\" of any kind (they increase your productivity a bit when everything goes smoothly... but you can pay that back with interest when you find yourself debugging problems [[including performance bottlenecks]] due to issues occurring below the abstraction levels that generators strive to provide).\nWhen I get a chance to use a good relational engine, such as PostgreSQL, I believe I'm overall more productive than I would be with any ORM in between (incuding SQLAlchemy, despite its many admirable qualities).  However, I have to admit that the case is different when the relational engine is not all that good (e.g., I've never liked MySQL), or when porting to non-relational deployments is an important consideration.\nSo, back to your actual question, I do think that, overall, investing time in mastering SQLAlchemy is a good idea, and time well-spent.","Q_Score":1,"Tags":"python,sql,orm,sqlalchemy","A_Id":2947182,"CreationDate":"2010-06-01T03:49:00.000","Title":"Transitioning from php to python\/pylons\/SQLAlchemy -- Are ORMs the standard now?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Should I invest a lot of time trying to figure out an ORM style implementation, or is it still common to just stick with standard SQL queries in python\/pylons\/sqlalchemy?","AnswerCount":2,"Available Count":2,"Score":0.0996679946,"is_accepted":false,"ViewCount":1032,"Q_Id":2947172,"Users Score":1,"Answer":"If you have never use an ORM like SqlAlchemy before, I would suggest that you learn it - as long as you are learning the Python way. If nothing else, you will be better able to decide where\/when to use it vs plain SQL. I don't think you should have to invest a lot of time on it. Documentation for SQLAlchemy is decent, and you can always ask for help if you get stuck.","Q_Score":1,"Tags":"python,sql,orm,sqlalchemy","A_Id":2947191,"CreationDate":"2010-06-01T03:49:00.000","Title":"Transitioning from php to python\/pylons\/SQLAlchemy -- Are ORMs the standard now?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a table formatted similar to this:\nDate | ID | Value | Difference\nI need to get the difference between a record's value column, and the previous record's value column based off of the date.\nI.E\n2 days ago | cow | 1 | Null\nYesterday | cow | 2 | Null\nToday | cow | 3 | Null\nYesterdays difference would be 1, and today's difference would be 1.\nbasically, I need to get the previous record based off the date, I don't know the interval's between each record. I've been stumped on this for a while. I am using Mysql, and Python to do the majority of the calculations.","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":530,"Q_Id":2960481,"Users Score":0,"Answer":"Use a SELECT... WHERE date <= NOW() && date >= ( NOW() - 90000 ) (90,000 is 25 hours, giving you a little leeway with the insert time), and then take the difference between the rows in python.","Q_Score":0,"Tags":"python,mysql","A_Id":2960589,"CreationDate":"2010-06-02T18:35:00.000","Title":"Get the previous date in Mysql","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"In one of my Django projects that use MySQL as the database, I need to have a date fields that accept also \"partial\" dates like only year (YYYY) and year and month (YYYY-MM) plus normal date (YYYY-MM-DD).\nThe date field in MySQL can deal with that by accepting 00 for the month and the day. So 2010-00-00 is valid in MySQL and it represent 2010. Same thing for 2010-05-00 that represent May 2010.\nSo I started to create a PartialDateField to support this feature. But I hit a wall because, by default, and Django use the default, MySQLdb, the python driver to MySQL, return a datetime.date object for a date field AND datetime.date() support only real date. So it's possible to modify the converter for the date field used by MySQLdb and return only a string in this format 'YYYY-MM-DD'. Unfortunately the converter use by MySQLdb is set at the connection level so it's use for all MySQL date fields. But Django DateField rely on the fact that the database return a datetime.date object, so if I change the converter to return a string, Django is not happy at all.\nSomeone have an idea or advice to solve this problem? How to create a PartialDateField in Django ?\nEDIT\nAlso I should add that I already thought of 2 solutions, create 3 integer fields for year, month and day (as mention by Alison R.) or use a varchar field to keep date as string in this format YYYY-MM-DD.\nBut in both solutions, if I'm not wrong, I will loose the special properties of a date field like doing query of this kind on them: Get all entries after this date. I can probably re-implement this functionality on the client side but that will not be a valid solution in my case because the database can be query from other systems (mysql client, MS Access, etc.)","AnswerCount":5,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":4080,"Q_Id":2971198,"Users Score":7,"Answer":"First, thanks for all your answers. None of them, as is, was a good solution for my problem, but, for your defense, I should add that I didn't give all the requirements. But each one help me think about my problem and some of your ideas are part of my final solution.\nSo my final solution, on the DB side, is to use a varchar field (limited to 10 chars) and storing the date in it, as a string, in the ISO format (YYYY-MM-DD) with 00 for month and day when there's no month and\/or day (like a date field in MySQL). This way, this field can work with any databases, the data can be read, understand and edited directly and easily by a human using a simple client (like mysql client, phpmyadmin, etc.). That was a requirement. It can also be exported to Excel\/CSV without any conversion, etc. The disadvantage is that the format is not enforce (except in Django). Someone could write 'not a date' or do a mistake in the format and the DB will accept it (if you have an idea about this problem...).\nThis way it's also possible to do all of the special queries of a date field relatively easily. For queries with WHERE: <, >, <=, >= and = work directly. The IN and BETWEEN queries work directly also. For querying by day or month you just have to do it with EXTRACT (DAY|MONTH ...). Ordering work also directly. So I think it covers all the query needs and with mostly no complication.\nOn the Django side, I did 2 things. First, I have created a PartialDate object that look mostly like datetime.date but supporting date without month and\/or day. Inside this object I use a datetime.datetime object to keep the date. I'm using the hours and minutes as flag that tell if the month and day are valid when they are set to 1. It's the same idea that steveha propose but with a different implementation (and only on the client side). Using a datetime.datetime object gives me a lot of nice features for working with dates (validation, comparaison, etc.).\nSecondly, I have created a PartialDateField that mostly deal with the conversion between the PartialDate object and the database.\nSo far, it works pretty well (I have mostly finish my extensive unit tests).","Q_Score":8,"Tags":"python,mysql,database,django,date","A_Id":3027410,"CreationDate":"2010-06-04T02:49:00.000","Title":"How to deal with \"partial\" dates (2010-00-00) from MySQL in Django?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am writing an app to do a file conversion and part of that is replacing old account numbers with a new account numbers.\nRight now I have a CSV file mapping the old and new account numbers with around 30K records. I read this in and store it as dict and when writing the new file grab the new account from the dict by key.\nMy question is what is the best way to do this if the CSV file increases to 100K+ records?\nWould it be more efficient to convert the account mappings from a CSV to a sqlite database rather than storing them as a dict in memory?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":109,"Q_Id":2980257,"Users Score":1,"Answer":"As long as they will all fit in memory, a dict will be the most efficient solution.  It's also a lot easier to code.  100k records should be no problem on a modern computer.\nYou are right that switching to an SQLite database is a good choice when the number of records gets very large.","Q_Score":3,"Tags":"python,database,sqlite,dictionary,csv","A_Id":2980269,"CreationDate":"2010-06-05T12:08:00.000","Title":"Efficient way to access a mapping of identifiers in Python","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm doing a project with reasonalby big DataBase. It's not a probper DB file, but a class with format as follows:\nDataBase.Nodes.Data=[[] for i in range(1,1000)] f.e. this DataBase is all together something like few thousands rows. Fisrt question - is the way I'm doing efficient, or is it better to use SQL, or any other \"proper\" DB, which I've never used actually. \nAnd the main question - I'd like to save my DataBase class with all record, and then re-open it with Python in another session. Is that possible, what tool should I use? cPickle - it seems to be only for strings, any other?\nIn matlab there's very useful functionality named save workspace - it saves all Your variables to a file that You can open at another session - this would be vary useful in python!","AnswerCount":3,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":306,"Q_Id":2990995,"Users Score":3,"Answer":"Pickle (cPickle) can handle any (picklable) Python object. So as long, as you're not trying to pickle thread or filehandle or something like that, you're ok.","Q_Score":3,"Tags":"python,serialization,pickle,object-persistence","A_Id":2991030,"CreationDate":"2010-06-07T15:52:00.000","Title":"How to save big \"database-like\" class in python","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm building a web application, and I need to use an architecture that allows me to run it over two servers. The application scrapes information from other sites periodically, and on input from the end user. To do this I'm using Php+curl to  scrape the information, Php or python to parse it and store the results in a MySQLDB. \nThen I will use Python to run some algorithms on the data, this will happen both periodically and  on input from the end user. I'm going to cache some of the results in the MySQL DB and sometimes if it is specific to the user, skip storing the data and serve it to the user. \nI'm think of using Php for the website front end on a separate web server, running the Php spider, MySQL DB and python on another server. \nWhat frame work(s) should I use for this kind of job? Is MVC and Cakephp a good solution? If so will I be able to control and monitor the Python code using it?\nThanks","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1161,"Q_Id":3021921,"Users Score":2,"Answer":"How do go about implementing this? \n\nToo big a question for an answer here. Certainly you don't want 2 sets of code for the scraping (1 for scheduled, 1 for demand) in addition to the added complication, you really don't want to be running job which will take an indefinite time to complete within the thread generated by a request to your webserver - user requests for a scrape should be run via the scheduling mechanism and reported back to users (although if necessary you could use Ajax polling to give the illusion that it's happening in the same thread).\n\nWhat frame work(s) should I use?\n\nFrameworks are not magic bullets. And you shouldn't be choosing a framework based primarily on the nature of the application you are writing. Certainly if specific, critical functionality is precluded by a specific framework, then you are using the wrong framework - but in my experience that has never been the case - you just need to write some code yourself. \n\nusing something more complex than a cron job\n\nYes, a cron job is probably not the right way to go for lots of reasons. If it were me I'd look at writing a daemon which would schedule scrapes (and accept connections from web page scripts to enqueue additional scrapes). But I'd run the scrapes as separate processes. \n\nIs MVC a good architecture for this? (I'm new to MVC, architectures etc.)\n\nNo. Don't start by thinking whether a pattern fits the application - patterns are a useful tool for teaching but describe what code is not what it will be\n(Your application might include some MVC patterns - but it should also include lots of other ones).\nC.","Q_Score":3,"Tags":"php,python,model-view-controller,cakephp,application-server","A_Id":3022395,"CreationDate":"2010-06-11T10:12:00.000","Title":"Web application architecture, and application servers?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Criteria for 'better': fast in math and simple (few fields, many records) db transactions, convenient to develop\/read\/extend, flexible, connectible.\nThe task is to use a common web development scripting language to process and calculate long time series and multidimensional surfaces (mostly selecting\/inserting sets of floats and doing maths with them).\nThe choice is Ruby 1.9, Python 2, Python 3, PHP 5.3, Perl 5.12, or JavaScript (node.js).\nAll the data is to be stored in a relational database (due to its heavily multidimensional nature); all the communication with outer world is to be done by means of web services.","AnswerCount":2,"Available Count":2,"Score":0.3799489623,"is_accepted":false,"ViewCount":451,"Q_Id":3022232,"Users Score":4,"Answer":"The best option is probably the language you're most familiar with. My second consideration would be if you need to use any special maths libraries and whether they're supported in each of the languages.","Q_Score":4,"Tags":"php,python,ruby,performance,math","A_Id":3022304,"CreationDate":"2010-06-11T11:13:00.000","Title":"What's a better choice for SQL-backed number crunching - Ruby 1.9, Python 2, Python 3, or PHP 5.3?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Criteria for 'better': fast in math and simple (few fields, many records) db transactions, convenient to develop\/read\/extend, flexible, connectible.\nThe task is to use a common web development scripting language to process and calculate long time series and multidimensional surfaces (mostly selecting\/inserting sets of floats and doing maths with them).\nThe choice is Ruby 1.9, Python 2, Python 3, PHP 5.3, Perl 5.12, or JavaScript (node.js).\nAll the data is to be stored in a relational database (due to its heavily multidimensional nature); all the communication with outer world is to be done by means of web services.","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":451,"Q_Id":3022232,"Users Score":10,"Answer":"I would suggest Python with it's great Scientifical\/Mathematical libraries (SciPy, NumPy). Otherwise the languages are not differing so much, although I doubt that Ruby, PHP or JS can keep up with the speed of Python or Perl.\nAnd what the comments below here say: at this moment, go for the latest Python2 (which is Python2.7). This has mature versions of all needed libraries, and if you follow the coding guidelines, transferring some day to Python 3 will be only a small pain.","Q_Score":4,"Tags":"php,python,ruby,performance,math","A_Id":3022242,"CreationDate":"2010-06-11T11:13:00.000","Title":"What's a better choice for SQL-backed number crunching - Ruby 1.9, Python 2, Python 3, or PHP 5.3?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm doing some queries in Python on a large database to get some stats out of the database. I want these stats to be in-memory so other programs can use them without going to a database. \nI was thinking of how to structure them, and after trying to set up some complicated nested dictionaries, I realized that a good representation would be an SQL table. I don't want to store the data back into the persistent database, though. Are there any in-memory implementations of an SQL database that supports querying the data with SQL syntax?","AnswerCount":6,"Available Count":1,"Score":0.0333209931,"is_accepted":false,"ViewCount":44308,"Q_Id":3047412,"Users Score":1,"Answer":"In-memory databases usually do not support memory paging option (for the whole database or certain tables), i,e, total size of the database should be smaller than the available physical memory or maximum shared memory size.\nDepending on your application, data-access pattern, size of database and available system memory for database, you have a few choices:\na. Pickled Python Data in File System\nIt stores structured Python data structure (such as list of dictionaries\/lists\/tuples\/sets, dictionary of lists\/pandas dataframes\/numpy series, etc.) in pickled format so that they could be used immediately and convienently upon unpickled. AFAIK, Python does not use file system as backing store for Python objects in memory implicitly but host operating system may swap out Python processes for higher priority processes. This is suitable for static data, having smaller memory size compared to available system memory. These pickled data could be copied to other computers, read by multiple dependent or independent processes in the same computer. The actual database file or memory size has higher overhead than size of the data. It is the fastest way to access the data as the data is in the same memory of the Python process, and without a query parsing step.\nb. In-memory Database\nIt stores dynamic or static data in the memory. Possible in-memory libraries that with Python API binding are Redis, sqlite3, Berkeley Database, rqlite, etc.  Different in-memory databases offer different features\n\nDatabase may be locked in the physical memory so that it is not swapped to memory backing store by the host operating system. However the actual implementation for the same libray may vary across different operating systems.\nThe database may be served by a database server process.\nThe in-memory may be accessed by multiple dependent or independent processes.\nSupport full, partial or no ACID model.\nIn-memory database could be persistent to physical files so that it is available when the host operating is restarted.\nSupport snapshots or\/and different database copies for backup or database management.\nSupport distributed database using master-slave, cluster models.\nSupport from simple key-value lookup to advanced query, filter, group functions (such as SQL, NoSQL)\n\nc. Memory-map Database\/Data Structure\nIt stores static or dynamic data which could be larger than physical memory of the host operating system. Python developers could use API such as mmap.mmap() numpy.memmap() to map certain files into process memory space.  The files could be arranged into index and data so that data could be lookup\/accessed via index lookup.  This is actually the mechanism used by various database libraries.  Python developers could implement custom techniques to access\/update data efficiency.","Q_Score":32,"Tags":"python,sql,database,in-memory-database","A_Id":65153849,"CreationDate":"2010-06-15T17:13:00.000","Title":"in-memory database in Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm running a Django project on Postgresql 8.1.21 (using Django 1.1.1, Python2.5, psycopg2, Apache2 with mod_wsgi 3.2). We've recently encountered this lovely error:\nOperationalError: FATAL:  connection limit exceeded for non-superusers\nI'm not the first person to run up against this. There's a lot of discussion about this error, specifically with psycopg, but much of it centers on older versions of Django and\/or offer solutions involving edits to code in Django itself. I've yet to find a succinct explanation of how to solve the problem of the Django ORM (or psycopg, whichever is really responsible, in this case) leaving open Postgre connections.\nWill simply adding connection.close() at the end of every view solve this problem? Better yet, has anyone conclusively solved this problem and kicked this error's ass? \nEdit: we later upped Postgresql's limit to 500 connections; this prevented the error from cropping up, but replaced it with excessive memory usage.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":2568,"Q_Id":3049625,"Users Score":1,"Answer":"This could be caused by other things. For example, configuring Apache\/mod_wsgi in a way that theoretically it could accept more concurrent requests than what the database itself may be able to accept at the same time. Have you reviewed your Apache\/mod_wsgi configuration and compared limit on maximum clients to that of PostgreSQL to make sure something like that hasn't been done. Obviously this presumes though that you have managed to reach that limit in Apache some how and also depends on how any database connection pooling is set up.","Q_Score":3,"Tags":"python,database,django,postgresql,django-orm","A_Id":3049796,"CreationDate":"2010-06-15T22:45:00.000","Title":"Django ORM and PostgreSQL connection limits","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"THE TASK:\nI am in the process of migrating a DB from MS Access to Maximizer. In order to do this I must take 64 tables in MS ACCESS and merge them into one. The output must be in the form of a TAB or CSV file. Which will then be imported into Maximizer.\nTHE PROBLEM:\nAccess is unable to perform a query that is so complex it seems, as it crashes any time I run the query.\nALTERNATIVES:\nI have thought about a few alternatives, and would like to do the least time-consuming one, out of these, while also taking advantage of any opportunities to learn something new.\n\nExport each table into CSVs and import into SQLight and then make a query with it to do the same as what ACCESS fails to do (merge 64 tables).\nExport each table into CSVs and write a script to access each one and merge the CSVs into a single CSV.\nSomehow connect to the MS ACCESS DB (API), and write a script to pull data from each table and merge them into a CSV file.\n\nQUESTION:\nWhat do you recommend?\nCLARIFICATIONS:\n\nI am merging tables, not concatenating. Each table has a different structure and different data. It is a normalized CRM database. Companies->contacts->details = ~ 60 tables of details.\nAs the Access db will be scuttled after the db is migrated, I want to spend as little time in Access as possible.","AnswerCount":4,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":4410,"Q_Id":3064830,"Users Score":0,"Answer":"I'm not even clear on what you're trying to do. I assume your problem is that Jet\/ACE can't handle a UNION with that many SELECT statements. \nIf you have 64 identically-structured tables and you want them in a single CSV, I'd create a temp table in Access, append each table in turn, then export from the temp table to CSV. This is a simple solution and shouldn't be slow, either. The only possible issue might be if there are dupes, but if there are, you can export from a SELECT DISTINCT saved QueryDef.\nTangentially, I'm surprised Maximizer still exists. I had a client who used to use it, and the db structure was terribly unnormalized, just like all the other sales software like ACT.","Q_Score":2,"Tags":"python,sql,ms-access,crm","A_Id":3073339,"CreationDate":"2010-06-17T19:13:00.000","Title":"Query crashes MS Access","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"THE TASK:\nI am in the process of migrating a DB from MS Access to Maximizer. In order to do this I must take 64 tables in MS ACCESS and merge them into one. The output must be in the form of a TAB or CSV file. Which will then be imported into Maximizer.\nTHE PROBLEM:\nAccess is unable to perform a query that is so complex it seems, as it crashes any time I run the query.\nALTERNATIVES:\nI have thought about a few alternatives, and would like to do the least time-consuming one, out of these, while also taking advantage of any opportunities to learn something new.\n\nExport each table into CSVs and import into SQLight and then make a query with it to do the same as what ACCESS fails to do (merge 64 tables).\nExport each table into CSVs and write a script to access each one and merge the CSVs into a single CSV.\nSomehow connect to the MS ACCESS DB (API), and write a script to pull data from each table and merge them into a CSV file.\n\nQUESTION:\nWhat do you recommend?\nCLARIFICATIONS:\n\nI am merging tables, not concatenating. Each table has a different structure and different data. It is a normalized CRM database. Companies->contacts->details = ~ 60 tables of details.\nAs the Access db will be scuttled after the db is migrated, I want to spend as little time in Access as possible.","AnswerCount":4,"Available Count":2,"Score":0.049958375,"is_accepted":false,"ViewCount":4410,"Q_Id":3064830,"Users Score":1,"Answer":"I would recommend #2 if the merge is fairly simple and straightforward, and doesn't need the power of an RDBMS. I'd go with #1 if the merge is more complex and you will need to write some actual queries to get the data merged properly.","Q_Score":2,"Tags":"python,sql,ms-access,crm","A_Id":3064852,"CreationDate":"2010-06-17T19:13:00.000","Title":"Query crashes MS Access","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I've just started learning Python Django and have a lot of experience building high traffic websites using PHP and MySQL. What worries me so far is Python's overly optimistic approach that you will never need to write custom SQL and that it automatically creates all these Foreign Key relationships in your database. The one thing I've learned in the last few years of building Chess.com is that its impossible to NOT write custom SQL when you're dealing with something like MySQL that frequently needs to be told what indexes it should use (or avoid), and that Foreign Keys are a death sentence. Percona's strongest recommendation was for us to remove all FKs for optimal performance.\nIs there a way in Django to do this in the models file? create relationships without creating actual DB FKs? Or is there a way to start at the database level, design\/create my database, and then have Django reverse engineer the models file?","AnswerCount":5,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":640,"Q_Id":3066255,"Users Score":0,"Answer":"I concur with the 'no foreign keys' advice (with the disclaimer: I also work for Percona).\nThe reason why it is is recommended is for concurrency \/ reducing locking internally.\nIt can be a difficult \"optimization\" to sell, but if you consider that the database has transactions (and is more or less ACID compliant) then it should only be application-logic errors that cause foreign-key violations.  Not to say they don't exist, but if you enable foreign keys in development hopefully you should find at least a few bugs.\nIn terms of whether or not you need to write custom SQL:\nThe explanation I usually give is that \"optimization rarely decreases complexity\".   I think it is okay to stick with an ORM by default, but if in a profiler it looks like one particular piece of functionality is taking a lot more time than you suspect it would when written by hand, then you need to be prepared to fix it (assuming the code is called often enough).\nThe real secret here is that you need good instrumentation \/ profiling in order to be frugal with your complexity adding optimization(s).","Q_Score":2,"Tags":"python,mysql,django","A_Id":3320441,"CreationDate":"2010-06-17T23:07:00.000","Title":"Does Python Django support custom SQL and denormalized databases with no Foreign Key relationships?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I've just started learning Python Django and have a lot of experience building high traffic websites using PHP and MySQL. What worries me so far is Python's overly optimistic approach that you will never need to write custom SQL and that it automatically creates all these Foreign Key relationships in your database. The one thing I've learned in the last few years of building Chess.com is that its impossible to NOT write custom SQL when you're dealing with something like MySQL that frequently needs to be told what indexes it should use (or avoid), and that Foreign Keys are a death sentence. Percona's strongest recommendation was for us to remove all FKs for optimal performance.\nIs there a way in Django to do this in the models file? create relationships without creating actual DB FKs? Or is there a way to start at the database level, design\/create my database, and then have Django reverse engineer the models file?","AnswerCount":5,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":640,"Q_Id":3066255,"Users Score":0,"Answer":"django-admin inspectdb allows you to reverse engineer a models file from existing tables. That is only a very partial response to your question ;)","Q_Score":2,"Tags":"python,mysql,django","A_Id":3066274,"CreationDate":"2010-06-17T23:07:00.000","Title":"Does Python Django support custom SQL and denormalized databases with no Foreign Key relationships?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I've just started learning Python Django and have a lot of experience building high traffic websites using PHP and MySQL. What worries me so far is Python's overly optimistic approach that you will never need to write custom SQL and that it automatically creates all these Foreign Key relationships in your database. The one thing I've learned in the last few years of building Chess.com is that its impossible to NOT write custom SQL when you're dealing with something like MySQL that frequently needs to be told what indexes it should use (or avoid), and that Foreign Keys are a death sentence. Percona's strongest recommendation was for us to remove all FKs for optimal performance.\nIs there a way in Django to do this in the models file? create relationships without creating actual DB FKs? Or is there a way to start at the database level, design\/create my database, and then have Django reverse engineer the models file?","AnswerCount":5,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":640,"Q_Id":3066255,"Users Score":0,"Answer":"You can just create the model.py and avoid having SQL Alchemy automatically create the tables leaving it up to you to define the actual tables as you please.  So although there are foreign key relationships in the model.py this does not mean that they must exist in the actual tables.  This is a very good thing considering how ludicrously foreign key constraints are implemented in MySQL - MyISAM just ignores them and InnoDB creates a non-optional index on every single one regardless of whether it makes sense.","Q_Score":2,"Tags":"python,mysql,django","A_Id":3066360,"CreationDate":"2010-06-17T23:07:00.000","Title":"Does Python Django support custom SQL and denormalized databases with no Foreign Key relationships?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"How would I go around creating a MYSQL table schema inspecting an Excel(or CSV) file.\nAre there any ready Python libraries for the task?\nColumn headers would be sanitized to column names. Datatype would be estimated based on the contents of the spreadsheet column. When done, data would be loaded to the table.\nI have an Excel file of ~200 columns that I want to start normalizing.","AnswerCount":5,"Available Count":3,"Score":0.0399786803,"is_accepted":false,"ViewCount":7011,"Q_Id":3070094,"Users Score":1,"Answer":"As far as I know, there is no tool that can automate this process (I would love for someone to prove me wrong as I've had this exact problem before).\nWhen I did this, I came up with two options: \n(1) Manually create the columns in the db with the appropriate types and then import, or \n(2) Write some kind of filter that could \"figure out\" what data types the columns should be.\nI went with the first option mainly because I didn't think I could actually write a program to do the type inference.\nIf you do decide to write a type inference tool\/conversion, here are a couple of issues you may have to deal with:\n(1)  Excel dates are actually stored as the number of days since December 31st, 1899; how does one infer then that a column is dates as opposed to some piece of numerical data (population for example)?\n(2) For text fields, do you just make the columns of type varchar(n) where n is the longest entry in that column, or do you make it an unbounded char field if one of the entries is longer than some upper limit? If so, what's a good upper limit?\n(3) How do you automatically convert a float to a decimal with the correct precision and without loosing any places?\nObviously, this doesn't mean that you won't be able to (I'm a pretty bad programmer).  I hope you do, because it'd be a really useful tool to have.","Q_Score":6,"Tags":"python,mysql,excel,csv,import-from-excel","A_Id":3072109,"CreationDate":"2010-06-18T13:40:00.000","Title":"Generate table schema inspecting Excel(CSV) and import data","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"How would I go around creating a MYSQL table schema inspecting an Excel(or CSV) file.\nAre there any ready Python libraries for the task?\nColumn headers would be sanitized to column names. Datatype would be estimated based on the contents of the spreadsheet column. When done, data would be loaded to the table.\nI have an Excel file of ~200 columns that I want to start normalizing.","AnswerCount":5,"Available Count":3,"Score":0.0399786803,"is_accepted":false,"ViewCount":7011,"Q_Id":3070094,"Users Score":1,"Answer":"Quick and dirty workaround with phpmyadmin:\n\nCreate a table with the right amount of columns. Make sure the data fits the columns.\nImport the CSV into the table.\nUse the propose table structure.","Q_Score":6,"Tags":"python,mysql,excel,csv,import-from-excel","A_Id":3071074,"CreationDate":"2010-06-18T13:40:00.000","Title":"Generate table schema inspecting Excel(CSV) and import data","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"How would I go around creating a MYSQL table schema inspecting an Excel(or CSV) file.\nAre there any ready Python libraries for the task?\nColumn headers would be sanitized to column names. Datatype would be estimated based on the contents of the spreadsheet column. When done, data would be loaded to the table.\nI have an Excel file of ~200 columns that I want to start normalizing.","AnswerCount":5,"Available Count":3,"Score":1.2,"is_accepted":true,"ViewCount":7011,"Q_Id":3070094,"Users Score":1,"Answer":"Just for (my) reference, I documented below what I did:\n\nXLRD is practical, however I've just saved the Excel data as CSV, so I can use LOAD DATA INFILE\nI've copied the header row and started writing the import and normalization script\nScript does: CREATE TABLE with all columns as TEXT, except for Primary key\nquery mysql: LOAD DATA LOCAL INFILE loading all CSV data into TEXT fields.\nbased on the output of PROCEDURE ANALYSE, I was able to ALTER TABLE to give columns the right types and lengths. PROCEDURE ANALYSE returns ENUM for any column with few distinct values, which is not what I needed, but I found that useful later for normalization. Eye-balling 200 columns was a breeze with PROCEDURE ANALYSE. Output from PhpMyAdmin propose table structure was junk.\nI wrote some normalization mostly using SELECT DISTINCT on columns and INSERTing results to separate tables. I have added to the old table a column for FK first. Just after the INSERT, I've got its ID and UPDATEed the FK column. When loop finished I've dropped old column leaving only FK column. Similarly with multiple dependent columns. It was much faster than I expected.\nI ran (django) python manage.py inspctdb, copied output to models.py and added all those ForeignkeyFields as FKs do not exist on MyISAM. Wrote a little python views.py, urls.py, few templates...TADA","Q_Score":6,"Tags":"python,mysql,excel,csv,import-from-excel","A_Id":3169710,"CreationDate":"2010-06-18T13:40:00.000","Title":"Generate table schema inspecting Excel(CSV) and import data","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I currently work with Google's AppEngine and I could not find out, whether a Google DataStorage Object Entry has an ID by default, and if not, how I add such a field and let it increase automatically?\nregards,","AnswerCount":3,"Available Count":2,"Score":0.2605204458,"is_accepted":false,"ViewCount":282,"Q_Id":3077156,"Users Score":4,"Answer":"An object has a Key, part of which is either an automatically-generated numeric ID, or an assigned key name.  IDs are not guaranteed to be increasing, and they're almost never going to be consecutive because they're allocated to an instance in big chunks, and IDs unused by the instance to which they're allocated will never be used by another instance (at least, not currently).  They're also only unique within the same entity group for a kind; they're not unique to the entire kind if you have parent relationships.","Q_Score":1,"Tags":"python,google-app-engine,gql","A_Id":3078018,"CreationDate":"2010-06-19T20:38:00.000","Title":"Does GQL automatically add an \"ID\" Property","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I currently work with Google's AppEngine and I could not find out, whether a Google DataStorage Object Entry has an ID by default, and if not, how I add such a field and let it increase automatically?\nregards,","AnswerCount":3,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":282,"Q_Id":3077156,"Users Score":3,"Answer":"Yes, they have id's by default, and it is named ID as you mentioned.","Q_Score":1,"Tags":"python,google-app-engine,gql","A_Id":3077170,"CreationDate":"2010-06-19T20:38:00.000","Title":"Does GQL automatically add an \"ID\" Property","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I am trying to use the SimpleDB in following way. \nI want to keep 48 hrs worth data at anytime into simpledb and query it for different purposes. \nEach domain has 1 hr worth data, so at any time there are 48 domains present in the simpledb.\nAs the new data is constantly uploaded, I delete the oldest domain and create a new domain for each new hour.\nEach domain is about 50MB in size, the total size of all the domains is around 2.2 GB.\nThe item in the domain has following type of attributes\nidentifier - around 50 characters long  -- 1 per item\ntimestamp - timestamp value -- 1 per item\nserial_n_data - 500-1000 bytes data -- 200 per item \nI'm using python boto library to upload and query the data. \nI send 1 item\/sec with around 200 attributes in the domain.\nFor one of the application of this data, I need to get all the data from all the 48 domains. \nThe Query looks like, \"SELECT * FROM domain\", for all the domains.\nI use 8 threads to query data with each thread taking responsibility of few domains.\ne.g domain 1-6 thread 1\n    domain 7-12 thread 2 and so on   \nIt takes close to 13 minutes to get the entire data.I am using boto's select method for this.I need much more faster performance than this. Any suggestions on speed up the querying process? Is there any other language that I can use, which can speed up the things?","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1743,"Q_Id":3103145,"Users Score":0,"Answer":"I have had the same issue as you Charlie. After profiling the code, I have narrowed the performance problem down to SSL. It seems like that is where it is spending most of it's time and hence CPU cycles.\nI have read of a problem in the httplib library (which boto uses for SSL) where the performance doesn't increase unless the packets are over a certain size, though that was for Python 2.5 and may have already been fixed.","Q_Score":2,"Tags":"python,amazon-simpledb,boto","A_Id":9012699,"CreationDate":"2010-06-23T15:38:00.000","Title":"SimpleDB query performance improvement using boto","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Can I somehow work with remote databases (if they can do it) with the Django ORM?\nIt is understood that the sitting has spelled out the local database. And periodically to make connection to various external databases and perform any sort of commands such as load dump.","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":121,"Q_Id":3123801,"Users Score":1,"Answer":"If you can connect to the database remotely, then you can simply specify its host\/port in settings.py exactly as you would a local one.","Q_Score":0,"Tags":"python,django,orm","A_Id":3125012,"CreationDate":"2010-06-26T12:05:00.000","Title":"Remote execution of commands using the Django ORM","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"My two main requirements for the site are related to degrees of separation and graph matching (given two graphs, return some kind of similarity score).\nMy first thought was to use MySql to do it, which would probably work out okay for storing how I want to manage 'friends' (similar to Twitter), but I'm thinking if I want to show users results which will make use of graphing algorithms (like shortest path between two people) maybe it isn't the way to go for that.\nMy language of choice for the front end, would be Python using something like Pylons but I haven't committed to anything specific yet and would be willing to budge if it fitted well with a good backend solution.\nI'm thinking of using MySQL for storing user profile data, neo4j for the graph information of relations between users and then have a Python application talk to both of them.\nMaybe there is a simpler\/more efficient way to do this kind of thing. At the moment for me it's more getting a suitable prototype done than worrying about scalability but I'm willing to invest some time learning something new if it'll save me time rewriting\/porting in the future.\nPS: I'm more of a programmer than a database designer, so I'd prefer having rewrite the frontend later rather than say porting over the database, which is the main reason I'm looking for advice.","AnswerCount":4,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":749,"Q_Id":3126155,"Users Score":2,"Answer":"MySQL is really your best choice for the database unless you want to go proprietary.\nAs for the actual language, pick whatever you are familiar with. While Youtube and Reddit are written in python, many of the other large sites use Ruby (Hulu, Twitter, Techcrunch) or C++ (Google) or PHP (Facebook, Yahoo, etc).","Q_Score":4,"Tags":"python,sql,mysql,database","A_Id":3126208,"CreationDate":"2010-06-27T02:19:00.000","Title":"What should I use for the backend of a 'social' website?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"With PostgreSQL, one of my tables has an 'interval' column, values of which I would like to extract as something I can manipulate (datetime.timedelta?); however I am using PyGreSQL which seems to be returning intervals as strings, which is less than helpful.\nWhere should I be looking to either parse the interval or make PyGreSQL return it as a <something useful>?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1424,"Q_Id":3134699,"Users Score":3,"Answer":"Use Psycopg 2.  It correctly converts between Postgres's interval data type and Python's timedelta.","Q_Score":0,"Tags":"python,sql,postgresql,pygresql","A_Id":3137124,"CreationDate":"2010-06-28T17:33:00.000","Title":"python sql interval","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I've decided to give Python a try on Netbeans. The problem so far is when try to run program I know works, i.e. if I ran it through the terminal. For the project I selected the correct Python version (2.6.5). And received the following error:\n\nTraceback (most recent call last):   File\n  \"\/Users\/XXX\/NetBeansProjects\/NewPythonProject3\/src\/newpythonproject3.py\",\n  line 4, in \n      import sqlite3 ImportError: No module named sqlite3","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":184,"Q_Id":3149370,"Users Score":0,"Answer":"Search for PYTHONPATH. You probably have different settings in your OS and Netbeans.","Q_Score":0,"Tags":"python,sqlite","A_Id":3151119,"CreationDate":"2010-06-30T12:50:00.000","Title":"Netbeans + sqlite3 = Fail?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm writing a script for exporting some data.\nSome details about the environment:\n\nThe project is Django based\nI'm using raw\/custom SQL for the export\nThe database engine is MySQL.\nThe database and code are on the same box.-\n\nDetails about the SQL:\n\nA bunch of inner joins\nA bunch of columns selected, some with a basic multiplication calculation.\nThe sql result has about 55K rows\n\nWhen I run the SQL statement in the mysql command line, it takes 3-4 seconds\nWhen I run the SQL in my python script the line cursor.execute(sql, [id]) takes over 60 seconds.\nAny ideas on what might be causing this?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":705,"Q_Id":3188289,"Users Score":0,"Answer":"Two ideas: \n\nMySQL may have query caching enabled, which makes it difficult to get accurate timing when you run the same query repeatedly.  Try changing the ID in your query to make sure that it really does run in 3-4 seconds consistently.\nTry using strace on the python process to see what it is doing during this time.","Q_Score":0,"Tags":"python,mysql,performance","A_Id":3188555,"CreationDate":"2010-07-06T16:39:00.000","Title":"Python MySQL Performance: Runs fast in mysql command line, but slow with cursor.execute","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"As is mentioned in the doc for google app engine, it does not support group by and other aggregation functions. Is there any alternatives to implement the same functionality?\nI am working on a project where I need it on urgent basis, being a large database its not efficient to iterate the result set and then perform the logic.\nPlease suggest.\nThanks in advance.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":322,"Q_Id":3210577,"Users Score":1,"Answer":"The best way is to populate the summaries (aggregates) at the time of write. This way your reads will be faster, since they just read - at the cost of writes which will have to update the summaries if its likely to be effected by the write. \nHopefully you will be reading more often than writing\/updating summaries.","Q_Score":0,"Tags":"python,google-app-engine","A_Id":3211471,"CreationDate":"2010-07-09T07:21:00.000","Title":"Google application engine Datastore - any alternatives to aggregate functions and group by?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I'm using Google Appengine to store a list of favorites, linking a Facebook UserID to one or more IDs from Bing. I need function calls returning the number of users who have favorited an item, and the number of times an item has been favorited (and by whom).\nMy question is, should I resolve this relationship into two tables for efficiency? If I have a table with columns for Facebook ID and Bing ID, I can easily use select queries for both of the functions above, however this will require that each row is searched in each query. The alternative is having two tables, one for each Facebook user's favorites and the other for each Bing item's favorited users, and using transactions to keep them in sync. The two tables option has the advantage of being able to use JSON or CSV in the database so that only one row needs to be fetched, and little manipulation needs to be done for an API.\nWhich option is better, in terms of efficiency and minimising cost?\nThanks,\nMatt","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":280,"Q_Id":3210994,"Users Score":0,"Answer":"I don't think there's a hard and fast answer to questions like this. \"Is this optimization worth it\" always depends on many variables such as, is the lack of optimization actually a problem to start with? How much of a problem is it? What's the cost in terms of extra time and effort and risk of bugs of a more complex optimized implementation, relative to the benefits? What might be the extra costs of implementing the optimization later, such as data migration to a new schema?","Q_Score":1,"Tags":"python,google-app-engine,performance,many-to-many","A_Id":3213988,"CreationDate":"2010-07-09T08:21:00.000","Title":"Many-to-many relationships in Google AppEngine - efficient?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I'm using MySQLdb and when I perform an UPDATE to a table row I sometimes get an infinite process hang.\nAt first I thought, maybe its COMMIT since the table is Innodb, but even with autocommit(True) and db.commit() after each update I still get the hang.\nIs it possible there is a row lock and the query just fails to carry out? Is there a way to handle potential row locks or maybe even handle slow queries?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":544,"Q_Id":3216027,"Users Score":1,"Answer":"Depending on your user privileges, you can execute SHOW PROCESSLIST or SELECT from information_schema.processlist while the UPDATE hangs to see if there is a contention issue with another query.  Also do an EXPLAIN on a SELECT of the WHERE clause used in the UPDATE to see if you need to change the statement.  \nIf it's a lock contention, then you should eventually encounter a Lock Wait Timeout (default = 50 sec, I believe).  Otherwise, if you have timing constraints, you can make use of KILL QUERY and KILL CONNECTION to unblock the cursor execution.","Q_Score":0,"Tags":"python,mysql","A_Id":3216500,"CreationDate":"2010-07-09T19:47:00.000","Title":"MySQLdb Handle Row Lock","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Is there a good step by step online guide to install xampp (apache server,mysql server) together with zope-plone on the same linux machine and make it play nicely or do I have to go through their confusing documentations?\nOr how can I install this configuration in the best way? I can install and use both seperately but in tandem is an issue for me. Any help is appreciated.","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":486,"Q_Id":3233246,"Users Score":0,"Answer":"sorry for wrong site but I just figured out that it was not a problem at all. I installed XAMPP (a snap) and downloaded and ran the plone install script. Both sites XAMPP on port 80 and zope\/plone on 8080 are working without problems. Just to let everyone know. I don't know why I got nervous about this :)","Q_Score":0,"Tags":"python,apache,xampp,plone,zope","A_Id":3247954,"CreationDate":"2010-07-13T00:09:00.000","Title":"Guide to install xampp with zope-plone on the same linux machine?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I never thought I'd ever say this but I'd like to have something like the report generator in Microsoft Access. Very simple, just list data from a SQL query.\nI don't really care what language is used as long as I can get it done fast. \nC#,C++,Python,Javascript...\nI want to know the quickest (development sense) way to display data from a database.\nedit :\nI'm using MySQL with web interface for data input. I would be much better if the user had some kind of GUI.","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":325,"Q_Id":3242448,"Users Score":0,"Answer":"Some suggestions:\n1) ASP.NET Gridview\n   ---use the free Visual Studio to create an asp.net page\n      ...can do VB, C#, etc.\n   ---drag\/drop a gridview control on your page, then connect it to your data and display fields, all via wizard (you did say quick and dirty, correct?).  No coding required if you can live within the wizard's limitations (which aren't too bad actually).\nThe type of database (mySQL or otherwise) isn't relevant.\nOther quick and dirty approach might be Access itself -- it can create 'pages', I think, that are web publishable.\nIf you want to put a little more work into it, ASP.NET has some other great controls \/ layout capability (non-wizard derived).\nAlso, you could look at SSRS if you have access to it.  More initial setup work, but has the option to let your users create their own reports in a semi-Access-like fashion.  Web accessible.\nGood luck.","Q_Score":0,"Tags":"c#,javascript,python,sql,database","A_Id":3249163,"CreationDate":"2010-07-13T23:59:00.000","Title":"Quick and dirty reports based on a SQL query","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Installed Django from source (python setup.py install and such), installed MySQLdb from source (python setup.py build, python setup.py install). Using Python 2.4 which came installed on the OS (CentOS 5.5). Getting the following error message after launching the server:\nError loading MySQLdb module: No module named MySQLdb\nThe pythonpath the debug info provides includes\n'\/usr\/lib\/python2.4\/site-packages'\nand yet, if I ls that directory, I can plainly see\nMySQL_python-1.2.3-py2.4-linux-i686.egg\nUsing the python interactive shell, I can type import MySQLdb and it produces no errors. This leads me to believe it's a Django pathing issue, but I haven't the slightest clue where to start looking as I'm new to both Django and python.\nEDIT: And to be a bit more specific, everything is currently running as root. I haven't setup any users yet on the machine, so none exist other than root.\nEDITx2: And to be even more specific, web server is Cherokee, and deploying using uWSGI. All installed from source.","AnswerCount":10,"Available Count":1,"Score":0.0199973338,"is_accepted":false,"ViewCount":38547,"Q_Id":3243073,"Users Score":1,"Answer":"Try this if you are using \nlinux:-  sudo apt-get install python-mysqldb\nwindows:- pip install python-mysqldb    or\n          easy_install python-mysqldb\nHope this should work","Q_Score":19,"Tags":"python,django,mysql","A_Id":23076238,"CreationDate":"2010-07-14T02:49:00.000","Title":"Django unable to find MySQLdb python module","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am a PHP guy. In PHP I mainly use Doctrine ORM to deal with database issues. I am considering move to Python + Django recently. I know Python but don't have experience with Django. Can anyone who has good knowledge of both Doctrine and ORM in Django give me a comparison of features of these two ORM implementations?","AnswerCount":4,"Available Count":3,"Score":0.049958375,"is_accepted":false,"ViewCount":5103,"Q_Id":3249977,"Users Score":1,"Answer":"Ive used Doctrine over a 2 year project that ended 1.5 years ago, since then i've been doing mostly Django.\nI prefer Djangos ORM over Doctrine any day, more features, more consistency, faster and shinier.","Q_Score":3,"Tags":"php,python,django,orm,doctrine","A_Id":8543708,"CreationDate":"2010-07-14T20:01:00.000","Title":"ORM in Django vs. PHP Doctrine","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am a PHP guy. In PHP I mainly use Doctrine ORM to deal with database issues. I am considering move to Python + Django recently. I know Python but don't have experience with Django. Can anyone who has good knowledge of both Doctrine and ORM in Django give me a comparison of features of these two ORM implementations?","AnswerCount":4,"Available Count":3,"Score":0.2449186624,"is_accepted":false,"ViewCount":5103,"Q_Id":3249977,"Users Score":5,"Answer":"I am a rare person who had to switch from Django 1.4 to Symfony 2.1 so I had to use Doctrine 2 instead of current Django ORM.\nMaybe Doctrine can do many things but let me tell you that it is a nightmare for me to use it coming from Django.\nI'm bored with the verbosity of php\/Symfony\/Doctrine ...\nAlso I never needed something that Django's ORM didn't manage already (maybe projects not big enough to reach the limits).\nSimply compare the description of data between both orms (including setters & getters)...","Q_Score":3,"Tags":"php,python,django,orm,doctrine","A_Id":12267439,"CreationDate":"2010-07-14T20:01:00.000","Title":"ORM in Django vs. PHP Doctrine","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am a PHP guy. In PHP I mainly use Doctrine ORM to deal with database issues. I am considering move to Python + Django recently. I know Python but don't have experience with Django. Can anyone who has good knowledge of both Doctrine and ORM in Django give me a comparison of features of these two ORM implementations?","AnswerCount":4,"Available Count":3,"Score":-0.049958375,"is_accepted":false,"ViewCount":5103,"Q_Id":3249977,"Users Score":-1,"Answer":"Django isn't just an orm. It is a web framework like symfony. The form framework in symfony is modeled on django for example. It's orm part is more like doctrine 2 I think, but I haven't played with either much.","Q_Score":3,"Tags":"php,python,django,orm,doctrine","A_Id":3250203,"CreationDate":"2010-07-14T20:01:00.000","Title":"ORM in Django vs. PHP Doctrine","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"We need to be able to inform a Delphi application in case there are changes to some of our tables in MySQL.\nDelphi clients are in the Internet behind a firewall, and they have to be authenticated before connecting to the notification server we need to implement. The server can be programmed using for example Java, PHP or Python, and it has to support thousands of clients.\nTypically one change in the database needs to be informed only to a single client, and I don't believe performance will be a bottleneck. It just has to be possible to inform any of those thousands of clients when a change affecting the specific client occurs.\nI have been thinking of a solution where:\n\nMySQL trigger would inform to notification server\nDelphi client connects to a messaging queue and gets the notification using it\n\nMy questions:\n\nWhat would be the best to way from the trigger to inform the external server of the change\nWhich message queue solution to pick?","AnswerCount":3,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":1596,"Q_Id":3255330,"Users Score":0,"Answer":"Why not use the XMPP protocol (aka Jabbber) ?","Q_Score":4,"Tags":"java,php,python,mysql,delphi","A_Id":3255344,"CreationDate":"2010-07-15T12:02:00.000","Title":"How to create a notification server which informs Delphi application when database changes?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"We need to be able to inform a Delphi application in case there are changes to some of our tables in MySQL.\nDelphi clients are in the Internet behind a firewall, and they have to be authenticated before connecting to the notification server we need to implement. The server can be programmed using for example Java, PHP or Python, and it has to support thousands of clients.\nTypically one change in the database needs to be informed only to a single client, and I don't believe performance will be a bottleneck. It just has to be possible to inform any of those thousands of clients when a change affecting the specific client occurs.\nI have been thinking of a solution where:\n\nMySQL trigger would inform to notification server\nDelphi client connects to a messaging queue and gets the notification using it\n\nMy questions:\n\nWhat would be the best to way from the trigger to inform the external server of the change\nWhich message queue solution to pick?","AnswerCount":3,"Available Count":2,"Score":0.0665680765,"is_accepted":false,"ViewCount":1596,"Q_Id":3255330,"Users Score":1,"Answer":"There is apache camel and spring intergration, both provides some ways to send messages across.","Q_Score":4,"Tags":"java,php,python,mysql,delphi","A_Id":3255395,"CreationDate":"2010-07-15T12:02:00.000","Title":"How to create a notification server which informs Delphi application when database changes?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Due to the nature of my application, I need to support fast inserts of large volumes of data into the database. Using executemany() increases performance, but there's a caveat. For example, MySQL has a configuration parameter called max_allowed_packet, and if the total size of my insert queries exceeds its value, MySQL throws an error.\nQuestion #1: Is there a way to tell SQLAlchemy to split the packet into several smaller ones?\nQuestion #2: If other RDBS have similar constraints, how should I work around them as well?\n\nP.S. I had posted this question earlier but deleted it when I wrongly assumed that likely I will not encounter this problem after all. Sadly, that's not the case.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":2103,"Q_Id":3267580,"Users Score":2,"Answer":"I had a similar problem recently and used the - not very elegant - work-around:\n\nFirst I parsed my.cnf for a value for max_allow_packets, if I can't find it, the maximum is set to a default value.\nAll data items are stored in a list.\nNext, for each data item I count the approximate byte length (with strings, it's the length of the string in bytes, for other data types I take the maximum bytes used to be safe.)\nI add them up, committing after I have reached approx. 75% of max_allow_packets (as SQL queries will take up space as well, just to be on the safe side).\n\nThis approach is not really beautiful, but it worked flawlessly for me.","Q_Score":1,"Tags":"python,mysql,sqlalchemy,large-query","A_Id":3271153,"CreationDate":"2010-07-16T17:54:00.000","Title":"SQLAlchemy and max_allowed_packet problem","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am trying to setup a website in django which allows the user to send queries to a database containing information about their representatives in the European Parliament. I have the data in a comma seperated .txt file with the following format:\n\nParliament, Name, Country, Party_Group, National_Party,  Position\n7, Marta Andreasen, United Kingdom, Europe of freedom and democracy Group, United Kingdom Independence Party, Member\netc....\n\nI want to populate a SQLite3 database with this data, but so far all the tutorials I have found only show how to do this by hand. Since I have 736 observations in the file I dont really want to do this.\nI suspect this is a simple matter, but I would be very grateful if someone could show me how to do this.\nThomas","AnswerCount":6,"Available Count":1,"Score":0.0665680765,"is_accepted":false,"ViewCount":7034,"Q_Id":3270952,"Users Score":2,"Answer":"You asked what the create(**dict(zip(fields, row))) line did.\nI don't know how to reply directly to your comment, so I'll try to answer it here.\nzip takes multiple lists as args and returns a list of their correspond elements as tuples. \nzip(list1, list2) => [(list1[0], list2[0]), (list1[1], list2[1]), .... ]\ndict takes a list of 2-element tuples and returns a dictionary mapping each tuple's first element (key) to its second element (value).\ncreate is a function that takes keyword arguments. You can use **some_dictionary to pass that dictionary into a function as keyword arguments. \ncreate(**{'name':'john', 'age':5}) => create(name='john', age=5)","Q_Score":13,"Tags":"python,django,sqlite","A_Id":3275298,"CreationDate":"2010-07-17T09:38:00.000","Title":"Populating a SQLite3 database from a .txt file with Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm having all sorts of trouble trying to instal MySQLdb (1.2.2) on snow leopard. I am running python 2.5.1 and MySQL 5.1 32bit.\nPython and MySQL are running just fine.\nI've also installed django 1.2.1, although I don't think thats all that important, but wanted to give an idea of the stack i'm trying to install. I am using python 2.5.x as my webhost only has that version as an option and I want to be as close to my production env as possible.\nanyway...\nAfter following many of the existing articles and tutorials which mention modifying _mysql.c and setup_posix.py etc, I am still running into trouble.\nHere is my stack trace:\nxxxxxxx-mbp:MySQL-python-1.2.2 xxxxxxx$ sudo ARCHFLAGS=\"-arch x86_64\" python setup.py build\nrunning build\nrunning build_py\ncreating build\ncreating build\/lib.macosx-10.3-i386-2.5\ncopying _mysql_exceptions.py -> build\/lib.macosx-10.3-i386-2.5\ncreating build\/lib.macosx-10.3-i386-2.5\/MySQLdb\ncopying MySQLdb\/init.py -> build\/lib.macosx-10.3-i386-2.5\/MySQLdb\ncopying MySQLdb\/converters.py -> build\/lib.macosx-10.3-i386-2.5\/MySQLdb\ncopying MySQLdb\/connections.py -> build\/lib.macosx-10.3-i386-2.5\/MySQLdb\ncopying MySQLdb\/cursors.py -> build\/lib.macosx-10.3-i386-2.5\/MySQLdb\ncopying MySQLdb\/release.py -> build\/lib.macosx-10.3-i386-2.5\/MySQLdb\ncopying MySQLdb\/times.py -> build\/lib.macosx-10.3-i386-2.5\/MySQLdb\ncreating build\/lib.macosx-10.3-i386-2.5\/MySQLdb\/constants\ncopying MySQLdb\/constants\/init.py -> build\/lib.macosx-10.3-i386-2.5\/MySQLdb\/constants\ncopying MySQLdb\/constants\/CR.py -> build\/lib.macosx-10.3-i386-2.5\/MySQLdb\/constants\ncopying MySQLdb\/constants\/FIELD_TYPE.py -> build\/lib.macosx-10.3-i386-2.5\/MySQLdb\/constants\ncopying MySQLdb\/constants\/ER.py -> build\/lib.macosx-10.3-i386-2.5\/MySQLdb\/constants\ncopying MySQLdb\/constants\/FLAG.py -> build\/lib.macosx-10.3-i386-2.5\/MySQLdb\/constants\ncopying MySQLdb\/constants\/REFRESH.py -> build\/lib.macosx-10.3-i386-2.5\/MySQLdb\/constants\ncopying MySQLdb\/constants\/CLIENT.py -> build\/lib.macosx-10.3-i386-2.5\/MySQLdb\/constants\nrunning build_ext\nbuilding '_mysql' extension\ncreating build\/temp.macosx-10.3-i386-2.5\ngcc -isysroot \/Developer\/SDKs\/MacOSX10.4u.sdk -fno-strict-aliasing -Wno-long-double -no-cpp-precomp -mno-fused-madd -fno-common -dynamic -DNDEBUG -g -O3 -Dversion_info=(1,2,2,'final',0) -D__version__=1.2.2 -I\/usr\/local\/mysql-5.1.48-osx10.6-x86\/include -I\/Library\/Frameworks\/Python.framework\/Versions\/2.5\/include\/python2.5 -c _mysql.c -o build\/temp.macosx-10.3-i386-2.5\/_mysql.o -g -Os -arch i386 -fno-common -D_P1003_1B_VISIBLE -DSIGNAL_WITH_VIO_CLOSE -DSIGNALS_DONT_BREAK_READ -DIGNORE_SIGHUP_SIGQUIT -DDONT_DECLARE_CXA_PURE_VIRTUAL\nIn file included from \/Developer\/SDKs\/MacOSX10.4u.sdk\/usr\/include\/wchar.h:112,\n                 from \/Library\/Frameworks\/Python.framework\/Versions\/2.5\/include\/python2.5\/unicodeobject.h:118,\n                 from \/Library\/Frameworks\/Python.framework\/Versions\/2.5\/include\/python2.5\/Python.h:83,\n                 from pymemcompat.h:10,\n                 from _mysql.c:29:\n\/Developer\/SDKs\/MacOSX10.4u.sdk\/usr\/include\/stdarg.h:4:25: error: stdarg.h: No such file or directory\nIn file included from _mysql.c:35:\n\/usr\/local\/mysql-5.1.48-osx10.6-x86\/include\/my_config.h:1062:1: warning: \"HAVE_WCSCOLL\" redefined\nIn file included from \/Library\/Frameworks\/Python.framework\/Versions\/2.5\/include\/python2.5\/Python.h:8,\n                 from pymemcompat.h:10,\n                 from _mysql.c:29:\n\/Library\/Frameworks\/Python.framework\/Versions\/2.5\/include\/python2.5\/pyconfig.h:724:1: warning: this is the location of the previous definition\nerror: command 'gcc' failed with exit status 1\nDoes anyone have any ideas?","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":461,"Q_Id":3285631,"Users Score":0,"Answer":"I tried to solve this one for days myself and finally gave up.  \nI switched to postgres. It works pretty well with django on snow leopard,\nwith one minor problem. For some reason auto_inc pk ids don't get assigned\nto some models. I solved the problem by randomly assigning an id from a large\nrandom range, and relying on the unique column designation to prevent collisions.\nMy production server is linux. Mysql and postgres install fine on it.\nIn fact, many on the #django irc channel recommended running a virtual linux\ninstance on the mac to get around my mysql install problems on it.","Q_Score":2,"Tags":"python,mysql,django","A_Id":3285926,"CreationDate":"2010-07-19T22:34:00.000","Title":"Installing MySQLdb on Snow Leopard","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm playing around with a little web app in web.py, and am setting up a url to return a JSON object. What's the best way to convert a SQL table to JSON using python?","AnswerCount":14,"Available Count":1,"Score":0.0142847425,"is_accepted":false,"ViewCount":157377,"Q_Id":3286525,"Users Score":1,"Answer":"If you are using an MSSQL Server 2008 and above, you can perform your SELECT query to return json by using the FOR JSON AUTO clause E.G\nSELECT name, surname FROM users FOR JSON AUTO\nWill return Json as \n[{\"name\": \"Jane\",\"surname\": \"Doe\" }, {\"name\": \"Foo\",\"surname\": \"Samantha\" }, ..., {\"name\": \"John\", \"surname\": \"boo\" }]","Q_Score":54,"Tags":"python,sql,json","A_Id":55329857,"CreationDate":"2010-07-20T02:16:00.000","Title":"return SQL table as JSON in python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have 5 python cgi pages. I can navigate from one page to another. All pages get their data from the same database table just that they use different queries.\nThe problem is that the application as a whole is slow. Though they connect to the same database, each page creates a new handle every time I visit it and handles are not shared by the pages.\nI want to improve performance.\nCan I do that by setting up sessions for the user?\nSuggestions\/Advices are welcome.\nThanks","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":179,"Q_Id":3289330,"Users Score":0,"Answer":"Django and Pylons are both frameworks that solve this problem quite nicely, namely by abstracting the DB-frontend integration.  They are worth considering.","Q_Score":1,"Tags":"python,cgi","A_Id":3289546,"CreationDate":"2010-07-20T11:15:00.000","Title":"Improving performance of cgi","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I need to save an image file into sqlite database in python. I could not find a solution. How can I do it?\nThanks in advance.","AnswerCount":4,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":15288,"Q_Id":3309957,"Users Score":0,"Answer":"It's never a good idea to record raw types in databases. Couldn't you just save the file on the filesystem, and record the path to it in database?","Q_Score":8,"Tags":"python,image,sqlite,blob,pysqlite","A_Id":3310034,"CreationDate":"2010-07-22T14:29:00.000","Title":"pysqlite - how to save images","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I need to save an image file into sqlite database in python. I could not find a solution. How can I do it?\nThanks in advance.","AnswerCount":4,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":15288,"Q_Id":3309957,"Users Score":11,"Answer":"write - cursor.execute('insert into File \n(id, name, bin) values (?,?,?)', (id, name, sqlite3.Binary(file.read())))\nread - file = cursor.execute('select bin from File where id=?', (id,)).fetchone()\nif you need to return bin data in web app - return cStringIO.StringIO(file['bin'])","Q_Score":8,"Tags":"python,image,sqlite,blob,pysqlite","A_Id":3310995,"CreationDate":"2010-07-22T14:29:00.000","Title":"pysqlite - how to save images","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"This is a tricky question, we've been talking about this for a while (days) and haven't found a convincingly good solution. This is the situation:\n\nWe have users and groups. A user can belong to many groups (many to many relation)\nThere are certain parts of the site that need access control, but:\nThere are certain ROWS of certain tables that need access control, ie. a certain user (or certain group) should not be able to delete a certain row, but other rows of the same table could have a different permission setting for that user (or group)\n\nIs there an easy way to acomplish this? Are we missing something?\nWe need to implement this in python (if that's any help).","AnswerCount":4,"Available Count":3,"Score":0.0996679946,"is_accepted":false,"ViewCount":214,"Q_Id":3327279,"Users Score":2,"Answer":"This problem is not really new; it's basically the general problem of authorization and access rights\/control.\nIn order to avoid having to model and maintain a complete graph of exactly what objects each user can access in each possible way, you have to make decisions (based on what your application does) about how to start reigning in the multiplicative scale factors. So first: where do users get their rights? If each user is individually assigned rights, you're going to pose a significant ongoig management challenge to whoever needs to add users, modify users, etc.\nPerhaps users can get their rights from the groups they're members of. Now you have a scale factor that simplifies management and makes the system easier to understand. Changing a group changes the effective rights for all users who are members.\nNow, what do these rights look like? It's still probably not wise to assign rights on a target object by object basis. Thus maybe rights should be thought of as a set of abstract \"access cards\".  Objects in the system can be marked as requiring \"blue\" access for read, \"red\" access for update, and \"black\" access for delete. Those abstract rights might be arranged in some sort of topology, such that having \"black\" access means you implicitly also have \"red\" and \"blue\", or maybe they're all disjoint; it's up to you and how your application has to work. (Note also that you may want to consider that object types \u2014 tables, if you like \u2014 may need their own access rules, at least for \"create\".\nBy introducing collection points in the graph pictures you draw relating actors in the system to objects they act upon, you can handle scale issues and keep the complexity of authorization under control. It's never easy, however, and often it's the case that voiced customer desires result in something that will never work out and never in fact achieve what the customer (thinks she) wants.\nThe implementation language doesn't have a lot to do with the architectural decisions you need to make.","Q_Score":2,"Tags":"python,access-control","A_Id":3327313,"CreationDate":"2010-07-24T23:11:00.000","Title":"Control access to parts of a system, but also to certain pieces of information","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"This is a tricky question, we've been talking about this for a while (days) and haven't found a convincingly good solution. This is the situation:\n\nWe have users and groups. A user can belong to many groups (many to many relation)\nThere are certain parts of the site that need access control, but:\nThere are certain ROWS of certain tables that need access control, ie. a certain user (or certain group) should not be able to delete a certain row, but other rows of the same table could have a different permission setting for that user (or group)\n\nIs there an easy way to acomplish this? Are we missing something?\nWe need to implement this in python (if that's any help).","AnswerCount":4,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":214,"Q_Id":3327279,"Users Score":0,"Answer":"It's hard to be specific without knowing more about your setup and about why exactly you need different users to have different permissions on different rows. But generally, I would say that whenever you access any data in the database in your code, you should precede it by an authorization check, which examines the current user and group and the row being inserted\/updated\/deleted\/etc. and decides whether the operation should be allowed or not. Consider designing your system in an encapsulated manner - for example you could put all the functions that directly access the database in one module, and make sure that each of them contains the proper authorization check. (Having them all in one file makes it less likely that you'll miss one)\nIt might be helpful to add a permission_class column to the table, and have another table specifying which users or groups have which permission classes. Then your authorization check simply has to take the value of the permission class for the current row, and see if the permissions table contains an association between that permission class and either the current user or any of his\/her groups.","Q_Score":2,"Tags":"python,access-control","A_Id":3327325,"CreationDate":"2010-07-24T23:11:00.000","Title":"Control access to parts of a system, but also to certain pieces of information","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"This is a tricky question, we've been talking about this for a while (days) and haven't found a convincingly good solution. This is the situation:\n\nWe have users and groups. A user can belong to many groups (many to many relation)\nThere are certain parts of the site that need access control, but:\nThere are certain ROWS of certain tables that need access control, ie. a certain user (or certain group) should not be able to delete a certain row, but other rows of the same table could have a different permission setting for that user (or group)\n\nIs there an easy way to acomplish this? Are we missing something?\nWe need to implement this in python (if that's any help).","AnswerCount":4,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":214,"Q_Id":3327279,"Users Score":0,"Answer":"Add additional column \"category\" or \"type\" to the table(s), that will categorize the rows (or if you will, group\/cluster them) - and then create a pivot table that defines the access control between (rowCategory, userGroup). So for each row, by its category you can pull which userGroups have access (and what kind of access).","Q_Score":2,"Tags":"python,access-control","A_Id":3327726,"CreationDate":"2010-07-24T23:11:00.000","Title":"Control access to parts of a system, but also to certain pieces of information","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm using MongoDB an nosql database. Basically as a result of a query I have a list of dicts which themselves contains lists of dictionaries... which I need to work with.\nUnfortunately dealing with all this data within Python can be brought to a crawl when the data is too much.\n\nI have never had to deal with this problem, and it would be great if someone with experience could give a few suggestions. =)","AnswerCount":3,"Available Count":2,"Score":0.0665680765,"is_accepted":false,"ViewCount":406,"Q_Id":3330668,"Users Score":1,"Answer":"Are you loading all the data into memory at once?  If so you could be causing the OS to swap memory to disk, which can bring any system to a crawl.  Dictionaries are hashtables so even an empty dict will use up a lot of memory, and from what you say you are creating a lot of them at once.  I don't know the MongoDB API, but I presume there is a way of iterating through the results one at a time instead of reading in the entire set of result at once - try using that.  Or rewrite your query to return a subset of the data.\nIf disk swapping is not the problem then profile the code to see what the bottleneck is, or put some sample code in your question.  Without more specific information it is hard to give a more specific answer.","Q_Score":0,"Tags":"python,parsing,list,sorting,dictionary","A_Id":3333193,"CreationDate":"2010-07-25T19:23:00.000","Title":"Speeding up parsing of HUGE lists of dictionaries - Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm using MongoDB an nosql database. Basically as a result of a query I have a list of dicts which themselves contains lists of dictionaries... which I need to work with.\nUnfortunately dealing with all this data within Python can be brought to a crawl when the data is too much.\n\nI have never had to deal with this problem, and it would be great if someone with experience could give a few suggestions. =)","AnswerCount":3,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":406,"Q_Id":3330668,"Users Score":3,"Answer":"Do you really want all of that data back in your Python program? If so fetch it back a little at a time, but if all you want to do is summarise the data then use mapreduce in MongoDB to distribute the processing and just return the summarised data.\nAfter all, the point about using a NoSQL database that cleanly shards all the data across multiple machines is precisely to avoid having to pull it all back onto a single machine for processing.","Q_Score":0,"Tags":"python,parsing,list,sorting,dictionary","A_Id":3333236,"CreationDate":"2010-07-25T19:23:00.000","Title":"Speeding up parsing of HUGE lists of dictionaries - Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I was using Python 2.6.5 to build my application, which came with sqlite3 3.5.9. Apparently though, as I found out in another question of mine, foreign key support wasn't introduced in sqlite3 until version 3.6.19. However, Python 2.7 comes with sqlite3 3.6.21, so this work -- I decided I wanted to use foreign keys in my application, so I tried upgrading to python 2.7.\nI'm using twisted, and I couldn't for the life of me get it to build. Twisted relies on zope.interface and I can't find zope.interface for python 2.7 -- I thought it might just \"work\" anyway, but I'd have to just copy all the files over myself, and get everything working myself, rather than just using the self-installing packages.\nSo I thought it might be wiser to just re-build python 2.6 and link it against a new version of sqlite3. But I don't know how--\nHow would I do this?\nI have Visual Studio 2008 installed as a compiler, I read that that is the only one that is really supported for Windows, and I am running a 64 bit operating system","AnswerCount":3,"Available Count":2,"Score":1.0,"is_accepted":false,"ViewCount":4281,"Q_Id":3333095,"Users Score":6,"Answer":"download the latest version of sqlite3.dll from sqlite website and replace the the sqlite3.dll in the python dir.","Q_Score":9,"Tags":"python,build,linker,sqlite","A_Id":3341117,"CreationDate":"2010-07-26T07:54:00.000","Title":"How can I upgrade the sqlite3 package in Python 2.6?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I was using Python 2.6.5 to build my application, which came with sqlite3 3.5.9. Apparently though, as I found out in another question of mine, foreign key support wasn't introduced in sqlite3 until version 3.6.19. However, Python 2.7 comes with sqlite3 3.6.21, so this work -- I decided I wanted to use foreign keys in my application, so I tried upgrading to python 2.7.\nI'm using twisted, and I couldn't for the life of me get it to build. Twisted relies on zope.interface and I can't find zope.interface for python 2.7 -- I thought it might just \"work\" anyway, but I'd have to just copy all the files over myself, and get everything working myself, rather than just using the self-installing packages.\nSo I thought it might be wiser to just re-build python 2.6 and link it against a new version of sqlite3. But I don't know how--\nHow would I do this?\nI have Visual Studio 2008 installed as a compiler, I read that that is the only one that is really supported for Windows, and I am running a 64 bit operating system","AnswerCount":3,"Available Count":2,"Score":0.0665680765,"is_accepted":false,"ViewCount":4281,"Q_Id":3333095,"Users Score":1,"Answer":"I decided I'd just give this a shot when I realized that every library I've ever installed in python 2.6 resided in my site-packages folder. I just... copied site-packages to my 2.7 installation, and it works so far. This is by far the easiest route for me if this works -- I'll look further into it but at least I can continue to develop now.\nI won't accept this answer, because it doesn't even answer my question, but it does solve my problem, as far as I can tell so far.","Q_Score":9,"Tags":"python,build,linker,sqlite","A_Id":3333348,"CreationDate":"2010-07-26T07:54:00.000","Title":"How can I upgrade the sqlite3 package in Python 2.6?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have some MySQL database server information that needs to be shared between a Python backend and a PHP frontend.\nWhat is the best way to go about storing the information in a manner wherein it can be read easily by Python and PHP?\nI can always brute force it with a bunch of str.replace() calls in Python and hope it works if nobody has a solution, or I can just maintain two separate files, but it would be a bunch easier if I could do this automatically.\nI assume it would be easiest to store the variables in PHP format directly and do conversions in Python, and I know there exist Python modules for serializing and unserializing PHP, but I haven't been able to get it all figured out.\nAny help is appreciated!","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":200,"Q_Id":3349445,"Users Score":4,"Answer":"Store the shared configuration in a plain text file, preferably in a standard format.\nYou might consider yaml, ini, or json. \nI'm pretty sure both PHP and python can very trivially read and parse all three of those formats.","Q_Score":0,"Tags":"php,python,mysql,variables,share","A_Id":3349485,"CreationDate":"2010-07-28T02:23:00.000","Title":"Python - PHP Shared MySQL server connection info?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I store groups of entities in the google app engine Data Store with the same ancestor\/parent\/entityGroup. This is so that the entities can be updated in one atomic datastore transaction.\nThe problem is as follows:\n\nI start a db transaction\nI update entityX by setting entityX.flag = True\nI save entityX\nI query for entity where flag == True. BUT, here is the problem. This query does NOT return any results. It should have returned entityX, but it did not.\n\nWhen I remove the transaction, my code works perfectly, so it must be the transaction that is causing this strange behavior.\nShould updates to entities in the entity group not be visible elsewhere in the same transaction?\nPS: I am using Python. And GAE tells me I can't use nested transactions :(","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":215,"Q_Id":3350068,"Users Score":0,"Answer":"Looks like you are not doing a commit on the  transaction before querying\n\nstart a db transaction\nupdate entityX by setting entityX.flag = True\nsave entityX\nCOMMIT TRANSACTION\nquery for entity where flag == True. BUT, here is the problem. This query does NOT return any results. It should have returned entityX, but it did not.\n\nIn a transaction, entities will not be persisted until the transaction is commited","Q_Score":2,"Tags":"python,google-app-engine","A_Id":3350082,"CreationDate":"2010-07-28T05:06:00.000","Title":"On the google app engine, why do updates not reflect in a transaction?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"We need to bulk load many long strings (>4000 Bytes, but <10,000 Bytes) using cx_Oracle. The data type in the table is CLOB. We will need to load >100 million of these strings. Doing this one by one would suck. Doing it in a bulk fashion, ie using cursor.arrayvar() would be ideal. However, CLOB does not support arrays. BLOB, LOB, LONG_STRING LONG_RAW don't either. Any help would be greatly appreciated.","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1252,"Q_Id":3358666,"Users Score":0,"Answer":"In the interest of getting shit done that is good enough, we did the abuse of the CLOB I mentioned in my comment. It took less than 30 minutes to get coded up, runs fast and works.","Q_Score":0,"Tags":"python,oracle,cx-oracle","A_Id":3373296,"CreationDate":"2010-07-29T00:41:00.000","Title":"Passing an array of long strings ( >4000 bytes) to an Oracle (11gR2) stored procedure using cx_Oracle","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am connecting to an MS SQL Server db from Python in Linux.  I am connecting via pyodbc using the FreeTDS driver.  When I return a money field from MSSQL it comes through as a float, rather than a Python Decimal.\nThe problem is with FreeTDS.  If I run the exact same Python code from Windows (where I do not need to use FreeTDS), pyodbc returns a Python Decimal.\nHow can I get back a Python Decimal when I'm running the code in Linux?","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":1284,"Q_Id":3371795,"Users Score":1,"Answer":"You could always just convert it to Decimal when it comes back...","Q_Score":0,"Tags":"python,sql-server,pyodbc,freetds","A_Id":3372035,"CreationDate":"2010-07-30T13:19:00.000","Title":"FreeTDS translating MS SQL money type to python float, not Decimal","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I set up Mysql5, mysql5-server and py26-mysql using Macports. I then started the mysql server and was able to start the prompt with mysql5\nIn my settings.py i changed database_engine to \"mysql\" and put \"dev.db\" in database_name.\nI left the username and password blank as the database doesnt exist yet.\nWhen I ran python manage.py syncdb, django raised an error\n'django.core.exceptions.ImproperlyConfigured: Error loading MySQLdb module: dynamic module does not define init function (init_mysql)`\nHow do I fix this? Do I have to create the database first? is it something else?","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":5039,"Q_Id":3376673,"Users Score":1,"Answer":"syncdb will not create a database for you -- it only creates tables that don't already exist in your schema.  You need to:\n\nCreate a user to 'own' the database (root is a bad choice).\nCreate the database with that user.\nUpdate the Django database settings with the correct database name, user, and password.","Q_Score":0,"Tags":"python,mysql,django","A_Id":3377350,"CreationDate":"2010-07-31T03:34:00.000","Title":"Django MySql setup","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I had my sqlalchemy related code in my main() method in my script.\nBut then when I created a function, I wasn't able to reference my 'products' mapper because it was in the main() method.\nShould I be putting the sqlalchemy related code (session, mapper, and classes) in global scope so all functions in my single file script can refer to it?\nI was told a script is usually layout out as:\nglobals\nfunctions\nclasses\nmain\nBut if I put sqlalchemy at the top to make it global, I have to move my classes to the top also.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":87,"Q_Id":3382739,"Users Score":2,"Answer":"Typical approach is to define all mappings in separate model module, with one file per class\/table.\nThen you just import needed classes whenever need them.","Q_Score":1,"Tags":"python,sqlalchemy","A_Id":3382810,"CreationDate":"2010-08-01T16:20:00.000","Title":"Where to put my sqlalchemy code in my script?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Lets say I have a database table which consists of three columns: id, field1 and field2.  This table may have anywhere between 100 and 100,000 rows in it.  I have a python script that should insert 10-1,000 new rows into this table.  However, if the new field1 already exists in the table, it should do an UPDATE, not an INSERT.\nWhich of the following approaches is more efficient?\n\nDo a SELECT field1 FROM table (field1 is unique) and store that in a list.  Then, for each new row, use list.count() to determine whether to INSERT or UPDATE\nFor each row, run two queries.  Firstly, SELECT count(*) FROM table WHERE field1=\"foo\" then either the INSERT or UPDATE.\n\nIn other words, is it more efficient to perform n+1 queries and search a list, or 2n queries and get sqlite to search?","AnswerCount":4,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":2505,"Q_Id":3404556,"Users Score":0,"Answer":"You appear to be comparing apples with oranges.\nA python list is only useful if your data fit into the address-space of the process. Once the data get big, this won't work any more.\nMoreover, a python list is not indexed - for that you should use a dictionary.\nFinally, a python list is non-persistent - it is forgotten when the process quits.\nHow can you possibly compare these?","Q_Score":2,"Tags":"python,performance,sqlite","A_Id":3536835,"CreationDate":"2010-08-04T10:18:00.000","Title":"Python performance: search large list vs sqlite","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Lets say I have a database table which consists of three columns: id, field1 and field2.  This table may have anywhere between 100 and 100,000 rows in it.  I have a python script that should insert 10-1,000 new rows into this table.  However, if the new field1 already exists in the table, it should do an UPDATE, not an INSERT.\nWhich of the following approaches is more efficient?\n\nDo a SELECT field1 FROM table (field1 is unique) and store that in a list.  Then, for each new row, use list.count() to determine whether to INSERT or UPDATE\nFor each row, run two queries.  Firstly, SELECT count(*) FROM table WHERE field1=\"foo\" then either the INSERT or UPDATE.\n\nIn other words, is it more efficient to perform n+1 queries and search a list, or 2n queries and get sqlite to search?","AnswerCount":4,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":2505,"Q_Id":3404556,"Users Score":0,"Answer":"I imagine using a python dictionary would allow for much faster searching than using a python list. (Just set the values to 0, you won't need them, and hopefully a '0' stores compactly.)\nAs for the larger question, I'm curious too. :)","Q_Score":2,"Tags":"python,performance,sqlite","A_Id":3404589,"CreationDate":"2010-08-04T10:18:00.000","Title":"Python performance: search large list vs sqlite","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"i am reading a csv file into a list of a list in python. it is around 100mb right now. in a couple of years that file will go to 2-5gigs. i am doing lots of log calculations on the data. the 100mb file is taking the script around 1 minute to do. after the script does a lot of fiddling with the data, it creates URL's that point to google charts and then downloads the charts locally. \ncan i continue to use python on a 2gig file or should i move the data into a database?","AnswerCount":5,"Available Count":5,"Score":1.2,"is_accepted":true,"ViewCount":1357,"Q_Id":3419624,"Users Score":4,"Answer":"I don't know exactly what you are doing.  But a database will just change how the data is stored.  and in fact it might take longer since most reasonable databases may have constraints put on columns and additional processing for the checks.  In many cases having the whole file local, going through and doing calculations is going to be more efficient than querying and writing it back to the database (subject to disk speeds, network and database contention, etc...).  But in some cases the database may speed things up, especially because if you do indexing it is easy to get subsets of the data.\nAnyway you mentioned logs, so before you go database crazy I have the following ideas for you to check out.  Anyway I'm not sure if you have to keep going through every log since the beginning of time to download charts and you expect it to grow to 2 GB or if eventually you are expecting 2 GB of traffic per day\/week.\n\nARCHIVING -- you can archive old logs, say every few months.  Copy the production logs to an archive location and clear the live logs out.  This will keep the file size reasonable.  If you are wasting time accessing the file to find the small piece you need then this will solve your issue.\nYou might want to consider converting to Java or C.  Especially on loops and calculations  you might see a factor of 30 or more speedup.  This will probably reduce the time immediately.  But over time as data creeps up, some day this will slow down as well.  if you have no bound on the amount of data, eventually even hand optimized Assembly by the world's greatest programmer will be too slow.  But it might give you 10x the time...\nYou also may want to think about figuring out the bottleneck (is it disk access, is it cpu time) and based on that figuring out a scheme to do this task in parallel.  If it is processing, look into multi-threading (and eventually multiple computers), if it is disk access consider splitting the file among multiple machines...It really depends on your situation.  But I suspect archiving might eliminate the need here.\nAs was suggested, if you are doing the same calculations over and over again, then just store them.  Whether you use a database or a file this will give you a huge speedup.  \nIf you are downloading stuff and that is a bottleneck, look into conditional gets using the if modified request.  Then only download changed items.  If you are just processing new charts then ignore this suggestion.\nOh and if you are sequentially reading a giant log file, looking for a specific place in the log line by line, just make another file storing the last file location you worked with and then do a seek each run.\nBefore an entire database, you may want to think of SQLite.\nFinally a \"couple of years\" seems like a long time in programmer time.  Even if it is just 2, a lot can change.  Maybe your department\/division will be laid off.  Maybe you will have moved on and your boss.  Maybe the system will be replaced by something else.  Maybe there will no longer be a need for what you are doing.  If it was 6 months I'd say fix it.  but for a couple of years, in most cases, I'd say just use the solution you have now and once it gets too slow then look to do something else.  You could make a comment in the code with your thoughts on the issue and even an e-mail to your boss so he knows it as well.  But as long as it works and will continue doing so for a reasonable amount of time, I would consider it \"done\" for now.  No matter what solution you pick, if data grows unbounded you will need to reconsider it.  Adding more machines, more disk space, new algorithms\/systems\/developments.  Solving it for a \"couple of years\" is probably pretty good.","Q_Score":4,"Tags":"python,sql","A_Id":3419835,"CreationDate":"2010-08-05T22:13:00.000","Title":"python or database?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"i am reading a csv file into a list of a list in python. it is around 100mb right now. in a couple of years that file will go to 2-5gigs. i am doing lots of log calculations on the data. the 100mb file is taking the script around 1 minute to do. after the script does a lot of fiddling with the data, it creates URL's that point to google charts and then downloads the charts locally. \ncan i continue to use python on a 2gig file or should i move the data into a database?","AnswerCount":5,"Available Count":5,"Score":0.0798297691,"is_accepted":false,"ViewCount":1357,"Q_Id":3419624,"Users Score":2,"Answer":"I always reach for a database for larger datasets. \nA database gives me some stuff for \"free\"; that is, I don't have to code it.\n\nsearching \nsorting\nindexing\nlanguage-independent connections\n\nSomething like SQLite might be the answer for you. \nAlso, you should investigate the \"nosql\" databases; it sounds like your problem might fit well into one of them.","Q_Score":4,"Tags":"python,sql","A_Id":3419871,"CreationDate":"2010-08-05T22:13:00.000","Title":"python or database?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"i am reading a csv file into a list of a list in python. it is around 100mb right now. in a couple of years that file will go to 2-5gigs. i am doing lots of log calculations on the data. the 100mb file is taking the script around 1 minute to do. after the script does a lot of fiddling with the data, it creates URL's that point to google charts and then downloads the charts locally. \ncan i continue to use python on a 2gig file or should i move the data into a database?","AnswerCount":5,"Available Count":5,"Score":0.1586485043,"is_accepted":false,"ViewCount":1357,"Q_Id":3419624,"Users Score":4,"Answer":"If you need to go through all lines each time you perform the \"fiddling\" it wouldn't really make much difference, assuming the actual \"fiddling\" is whats eating your cycles.\nPerhaps you could store the results of your calculations somehow, then a database would probably be nice. Also, databases have methods for ensuring data integrity and stuff like that, so a database is often a great place for storing large sets of data (duh! ;)).","Q_Score":4,"Tags":"python,sql","A_Id":3419726,"CreationDate":"2010-08-05T22:13:00.000","Title":"python or database?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"i am reading a csv file into a list of a list in python. it is around 100mb right now. in a couple of years that file will go to 2-5gigs. i am doing lots of log calculations on the data. the 100mb file is taking the script around 1 minute to do. after the script does a lot of fiddling with the data, it creates URL's that point to google charts and then downloads the charts locally. \ncan i continue to use python on a 2gig file or should i move the data into a database?","AnswerCount":5,"Available Count":5,"Score":0.1586485043,"is_accepted":false,"ViewCount":1357,"Q_Id":3419624,"Users Score":4,"Answer":"I'd only put it into a relational database if:\n\nThe data is actually relational and expressing it that way helps shrink the size of the data set by normalizing it.\nYou can take advantage of triggers and stored procedures to offload some of the calculations that your Python code is performing now.\nYou can take advantage of queries to only perform calculations on data that's changed, cutting down on the amount of work done by Python.\n\nIf neither of those things is true, I don't see much difference between a database and a file.  Both ultimately have to be stored on the file system.\nIf Python has to process all of it, and getting it into memory means loading an entire data set, then there's no difference between a database and a flat file.\n2GB of data in memory could mean page swapping and thrashing by your application.  I would be careful and get some data before I blamed the problem on the file.  Just because you access the data from a database won't solve a paging problem.\nIf your data's flat, I see less advantage in a database, unless \"flat\" == \"highly denormalized\".\nI'd recommend some profiling to see what's consuming CPU and memory before I made a change.  You're guessing about the root cause right now.  Better to get some data so you know where the time is being spent.","Q_Score":4,"Tags":"python,sql","A_Id":3419718,"CreationDate":"2010-08-05T22:13:00.000","Title":"python or database?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"i am reading a csv file into a list of a list in python. it is around 100mb right now. in a couple of years that file will go to 2-5gigs. i am doing lots of log calculations on the data. the 100mb file is taking the script around 1 minute to do. after the script does a lot of fiddling with the data, it creates URL's that point to google charts and then downloads the charts locally. \ncan i continue to use python on a 2gig file or should i move the data into a database?","AnswerCount":5,"Available Count":5,"Score":0.0399786803,"is_accepted":false,"ViewCount":1357,"Q_Id":3419624,"Users Score":1,"Answer":"At 2 gigs, you may start running up against speed issues.  I work with model simulations for which it calls hundreds of csv files and it takes about an hour to go through 3 iterations, or about 20 minutes per loop. \nThis is a matter of personal preference, but I would go with something like PostGreSql because it integrates the speed of python with the capacity of a sql-driven relational database.  I encountered the same issue a couple of years ago when my Access db was corrupting itself and crashing on a daily basis.  It was either MySQL or PostGres and I chose Postgres because of its python friendliness.  Not to say MySQL would not work with Python, because it does, which is why I say its personal preference.  \nHope that helps with your decision-making!","Q_Score":4,"Tags":"python,sql","A_Id":3419687,"CreationDate":"2010-08-05T22:13:00.000","Title":"python or database?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have an sqlite database whose data I need to transfer over the network, the server needs to modify the data, and then I need to get the db back and either update my local version or overwrite it with the new db. How should I do this? My coworker at first wanted to scrap the db and just use an .ini file, but this is going to be data that we have to parse pretty frequently (it's a user defined schedule that can change at the user's will, as well as the server's). I said we should just transfer the entire .db as a binary file and let them do with it what they will and then take it back. Or is there a way in sqlite to dump the db to a .sql file like you can do in MySQL so we can transfer it as text?\nAny other solutions? This is in python if it makes a difference\nupdate: This is on an embedded platform running linux (I'm not sure what version\/kernel or what OS commands we have except the basics that are obvious)","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":471,"Q_Id":3451708,"Users Score":3,"Answer":"Use the copy command in your OS.  No reason to overthink this.","Q_Score":0,"Tags":"python,sqlite,embedded,binary-data","A_Id":3451733,"CreationDate":"2010-08-10T17:29:00.000","Title":"Sending sqlite db over network","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm trying to copy an excel sheet with python, but I keep getting \"access denied\" error message. The file is closed and is not shared. It has macros though.\nIs their anyway I can copy the file forcefully with python?\nthanks.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":94,"Q_Id":3465231,"Users Score":0,"Answer":"If you do not have sufficient file permissions you will not be able to access the file. In that case you will have to execute your Python program as an user with sufficient permissions.\nIf on the other hand the file is locked using other means specific to Excel then I am not sure what exactly is the solution. You might have to work around the protection using other means which will require a fair amount of understanding of how Excel sheets are \"locked\". I don't know of any Python libraries that will do this for you.","Q_Score":0,"Tags":"python,excel-2003","A_Id":3466751,"CreationDate":"2010-08-12T06:32:00.000","Title":"Copying a file with access locks, forcefully with python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"is there a python ORM (object relational mapper) that has a tool for automatically creating python classes (as code so I can expand them) from a given database schema?\nI'm frequently faced with small tasks involving different databases (like importing\/exporting from various sources etc.) and I thought python together with the abovementioned tool would be perfect for that.\nIt should work like Visual Studios ADO.NET\/Linq for SQL designer, where I can just drop DB tables and VS creates classes for me ...\nThanks in advance.","AnswerCount":3,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":1411,"Q_Id":3478780,"Users Score":3,"Answer":"You do not need to produce a source code representation of your classes to be able to expand them.\nThe only trick is that you need the ORM to generate the classes BEFORE importing the module that defines the derived classes.\nEven better, don't use derivation, but use __getattr__ and __setattr__ to implement transparent delegation to the ORM classes.","Q_Score":2,"Tags":"python,orm,code-generation","A_Id":3481115,"CreationDate":"2010-08-13T16:18:00.000","Title":"Python ORM that automatically creates classes from DB schema","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a couple of sqlite dbs (i'd say about 15GBs), with about 1m rows in total - so not super big. I was looking at mongodb, and it looks pretty easy to work with, especially if I want to try and do some basic natural language processing on the documents which make up  the databases.\nI've never worked with Mongo in the past, no would have to learn from scratch (will be working in python). After googling around a bit, I came across a number of somewhat horrific stories about Mongodb re. reliability. Is this still a major problem ? In a crunch, I will of course retain the sqlite backups, but I'd rather not have to reconstruct my mongo databases constantly.\nJust wondering what sort data corruption issues people have actually faced recently with Mongo ? Is this a big concern?\nThanks!","AnswerCount":5,"Available Count":3,"Score":1.0,"is_accepted":false,"ViewCount":3302,"Q_Id":3487456,"Users Score":10,"Answer":"As others have said, MongoDB does not have single-server durability right now. Fortunately, it's dead easy to set up multi-node replication. You can even set up a second machine in another data center and have data automatically replicated to it live!\nIf a write must succeed, you can cause Mongo to not return from an insert\/update until that data has been replicated to n slaves. This ensures that you have at least n copies of the data. Replica sets allow you to add and remove nodes from your cluster on the fly without any significant work; just add a new node and it'll automatically sync a copy of the data. Remove a node and the cluster rebalances itself. It is very much designed to be used across multiple machines, with multiple nodes acting in parallel; this is it's preferred default setup, compared to something like MySQL, which expects one giant machine to do its work on, which you can then pair slaves against when you need to scale out. It's a different approach to data storage and scaling, but a very comfortable one if you take the time to understand its difference in assumptions, and how to build an architecture that capitalizes on its strengths.","Q_Score":12,"Tags":"python,sqlite,mongodb","A_Id":3491117,"CreationDate":"2010-08-15T13:00:00.000","Title":"Mongodb - are reliability issues significant still?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a couple of sqlite dbs (i'd say about 15GBs), with about 1m rows in total - so not super big. I was looking at mongodb, and it looks pretty easy to work with, especially if I want to try and do some basic natural language processing on the documents which make up  the databases.\nI've never worked with Mongo in the past, no would have to learn from scratch (will be working in python). After googling around a bit, I came across a number of somewhat horrific stories about Mongodb re. reliability. Is this still a major problem ? In a crunch, I will of course retain the sqlite backups, but I'd rather not have to reconstruct my mongo databases constantly.\nJust wondering what sort data corruption issues people have actually faced recently with Mongo ? Is this a big concern?\nThanks!","AnswerCount":5,"Available Count":3,"Score":0.1194272985,"is_accepted":false,"ViewCount":3302,"Q_Id":3487456,"Users Score":3,"Answer":"Mongo does not have ACID properties, specifically durability.  So you can face issues if the process does not shut down cleanly or the machine loses power.  You are supposed to implement backups and redundancy to handle that.","Q_Score":12,"Tags":"python,sqlite,mongodb","A_Id":3488244,"CreationDate":"2010-08-15T13:00:00.000","Title":"Mongodb - are reliability issues significant still?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a couple of sqlite dbs (i'd say about 15GBs), with about 1m rows in total - so not super big. I was looking at mongodb, and it looks pretty easy to work with, especially if I want to try and do some basic natural language processing on the documents which make up  the databases.\nI've never worked with Mongo in the past, no would have to learn from scratch (will be working in python). After googling around a bit, I came across a number of somewhat horrific stories about Mongodb re. reliability. Is this still a major problem ? In a crunch, I will of course retain the sqlite backups, but I'd rather not have to reconstruct my mongo databases constantly.\nJust wondering what sort data corruption issues people have actually faced recently with Mongo ? Is this a big concern?\nThanks!","AnswerCount":5,"Available Count":3,"Score":0.0798297691,"is_accepted":false,"ViewCount":3302,"Q_Id":3487456,"Users Score":2,"Answer":"I don't see the problem if you have the same data also in the sqlite backups. You can always refill your MongoDb databases. Refilling will only take a few minutes.","Q_Score":12,"Tags":"python,sqlite,mongodb","A_Id":3490547,"CreationDate":"2010-08-15T13:00:00.000","Title":"Mongodb - are reliability issues significant still?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I want to encrypt a string using RSA algorithm and then store that string into postgres database using SQLAlchemy in python. Then Retrieve the encrypted string and decrypt it using the same key. My problem is that the value gets stored in the database is not same as the actual encrypted string. The datatype of column which is storing the encrypted value is bytea. I am using pycrypto library. Do I need to change the data in a particular format before inserting it to database table?\nAny suggestions please.\nThanks,\nTara Singh","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":3897,"Q_Id":3507543,"Users Score":1,"Answer":"By \"same key\" you mean \"the other key\", right? RSA gives you a keypair, if you encrypt with one you decrypt with the other ...\nOther than that, it sounds like a encoding problem. Try storing the data as binary or encode the string with your databases collation.\nBasically encryption gives you bytes but you store them as a string (encoded bytes).","Q_Score":1,"Tags":"python,postgresql,sqlalchemy,rsa,pycrypto","A_Id":3507558,"CreationDate":"2010-08-17T22:39:00.000","Title":"Inserting Encrypted Data in Postgres via SQLALchemy","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'd like to query the database and get read-only objects with session object. I need to save the objects in my server and use them through the user session. If I use a object outside of the function that calls the database, I get this error:\n\"DetachedInstanceError: Parent instance is not bound to a Session; lazy load operation of attribute 'items' cannot proceed\"\nI don't need to make any change in those objects, so I don't need to load them again.\nIs there any way that I can get that?\nThanks in advance!","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":244,"Q_Id":3513433,"Users Score":0,"Answer":"You must load the parent object again.","Q_Score":0,"Tags":"python,sqlalchemy","A_Id":3513490,"CreationDate":"2010-08-18T14:57:00.000","Title":"How to get read-only objects from database?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm in the settings.py module, and I'm supposed to add the directory to the sqlite database.  How do I know where the database is and what the full directory is?\nI'm using Windows 7.","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":3575,"Q_Id":3524236,"Users Score":1,"Answer":"if you don't provide full path, it will use the current directory of settings.py,\nand if you wish to specify static path you can specify it like: c:\/projects\/project1\/my_proj.db\nor in case you want to make it dynamic then you can use os.path module\nso os.path.dirname(file) will give you the path of settings.py and accordingly you can alter the path for your database like os.path.join(os.path.dirname(file),'my_proj.db')","Q_Score":5,"Tags":"python,database,django,sqlite","A_Id":3524305,"CreationDate":"2010-08-19T17:02:00.000","Title":"Trouble setting up sqlite3 with django! :\/","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm working with two databases, a local version and the version on the server.  The server is the most up to date version and instead of recopying all values on all tables from the server to my local version, \nI would like to enter each table and only insert\/update the values that have changed, from server, and copy those values to my local version.\nIs there some simple method to handling such a case? Some sort of batch insert\/update? Googl'ing up the answer isn't working and I've tried my hand at coding one but am starting to get tied up in error handling..\nI'm using Python and MySQLDB... Thanks for any insight\nSteve","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1035,"Q_Id":3526629,"Users Score":0,"Answer":"If all of your tables' records had timestamps, you could identify \"the values that have changed in the server\" -- otherwise, it's not clear how you plan to do that part (which has nothing to do with insert or update, it's a question of \"selecting things right\").\nOnce you have all the important values, somecursor.executemany will let you apply them all as a batch.  Depending on your indexing it may be faster to put them into a non-indexed auxiliary temporary table, then insert\/update from all of that table into the real one (before dropping the aux\/temp one), the latter of course being a single somecursor.execute.\nYou can reduce wall-clock time for the whole job by using one (or a few) threads to do the selects and put the results onto a Queue.Queue, and a few worker threads to apply results plucked from the queue into the internal\/local server.  (Best balance of reading vs writing threads is best obtained by trying a few and measuring -- writing per se is slower than reading, but your bandwidth to your local server may be higher than to the other one, so it's difficult to predict).\nHowever, all of this is moot unless you do have a strategy to identify  \"the values that have changed in the server\", so it's not necessarily very useful to enter into more discussion about details \"downstream\" from that identification.","Q_Score":1,"Tags":"python,mysql,batch-file","A_Id":3527732,"CreationDate":"2010-08-19T21:59:00.000","Title":"Python + MySQLDB Batch Insert\/Update command for two of the same databases","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Sometimes, when fetching data from the database either through the python shell or through a python script, the python process dies, and one single word is printed to the terminal: Killed\nThat's literally all it says. It only happens with certain scripts, but it always happens for those scripts. It consistently happens with this one single query that takes a while to run, and also with a south migration that adds a bunch of rows one-by-one to the database.\nMy initial hunch was that a single transaction was taking too long, so I turned on autocommit for Postgres. Didn't solve the problem.\nI checked the Postgres logs, and this is the only thing in there:\n2010-08-19 22:06:34 UTC LOG:  could not receive data from client: Connection reset by peer\n2010-08-19 22:06:34 UTC LOG:  unexpected EOF on client connection\nI've tried googling, but as you might expect, a one-word error message is tough to google for. \nI'm using Django 1.2 with Postgres 8.4 on a single Ubuntu 10.4 rackspace cloud VPS, stock config for everything.","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1944,"Q_Id":3526748,"Users Score":6,"Answer":"Only one thing I could think of that will kill automatically a process on Linux - the OOM killer. What's in the system logs?","Q_Score":7,"Tags":"python,django,postgresql","A_Id":3529637,"CreationDate":"2010-08-19T22:19:00.000","Title":"Why do some Django ORM queries end abruptly with the message \"Killed\"?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I've been diving into MongoDB with kind help of MongoKit and MongoEngine, but then I started thinking whether the data mappers are necessary here. Both mappers I mentioned enable one to do simple things without any effort. But is any effort required to do simple CRUD? It appears to me that in case of NoSQL the mappers just substitute one api with another (but of course there is data validation, more strict schema, automatic referencing\/dereferencing) \nDo you use Data Mappers in your applications? How big are they (apps)? Why yes, why no?\nThanks","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":366,"Q_Id":3533064,"Users Score":1,"Answer":"We are running a production site using Mongodb for the backend (no direct queries to Mongo, we have a search layer in between).  We wrote our own business \/ object layer, i suppose it just seemed natural enough for the programmers to write in the custom logic.  We did separate the database and business layers, but they just didn't see a need to go for a separate library.  As the software keeps evolving I think it makes sense.  We have 15 million records.","Q_Score":2,"Tags":"python,orm,mongodb,mongoengine,mongokit","A_Id":3553262,"CreationDate":"2010-08-20T16:54:00.000","Title":"Do you use data mappers with MongoDB?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":0},{"Question":"I have an SQL database and am wondering what command you use to just get a list of the table names within that database.","AnswerCount":4,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":62222,"Q_Id":3556305,"Users Score":10,"Answer":"SHOW tables \n15 chars","Q_Score":35,"Tags":"python,mysql,mysql-python","A_Id":3556313,"CreationDate":"2010-08-24T12:18:00.000","Title":"How to retrieve table names in a mysql database with Python and MySQLdb?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"While I see a bunch of links\/binaries for mysql connector for python 2.6, I don't see one for 2.7\nTo use django, should I just revert to 2.6 or is there a way out ?\nI'm using windows 7 64bit\ndjango - 1.1\nMysql 5.1.50\nAny pointers would be great.","AnswerCount":3,"Available Count":1,"Score":0.0665680765,"is_accepted":false,"ViewCount":2224,"Q_Id":3562406,"Users Score":1,"Answer":"For Python 2.7 on specific programs:\n\nsudo chown -R $USER \/Library\/Python\/2.7\nbrew install mysql@5.7\nbrew install mysql-connector-c\nbrew link --overwrite mysql@5.7\necho 'export PATH=\"\/usr\/local\/opt\/mysql@5.7\/bin:$PATH\"' >> ~\/.bash_profile\nsed -i -e 's\/libs=\"$libs -l \"\/libs=\"$libs -lmysqlclient -lssl -lcrypto\"\/g' \/usr\/local\/bin\/mysql_config\npip install MySql-python\n\nThis solved all issues I was having running a program that ran on Python 2.7 on and older version of MySql","Q_Score":1,"Tags":"mysql,python-2.7","A_Id":58359370,"CreationDate":"2010-08-25T02:15:00.000","Title":"Is there no mysql connector for python 2.7 on windows","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I wanted to get the community's feedback on a language choice our team is looking to make in the near future.  We are a software developer, and I work in a team of Oracle and SQL Server DBAs supporting a cross platform Java application which runs on Oracle Application Server.  We have SQL Server and Oracle code bases, and support customers on Windows, Solaris and Linux servers.\nMany of the tasks we do on a frequent basis are insufficiently automated, and where they are, tend to be much more automated via shell scripts, with little equivalent functionality on Windows.  Unfortunately, we now have this problem of redeveloping scripts and so on, on two platforms.  So, I wish for us to choose a cross platform language to script in, instead of using Bash and awkwardly translating to Cygwin or Batch files where necessary.\nIt would need to be:\n\nDynamic (so don't suggest Java or C!)\nEasily available on each platform (Windows, Solaris, Linux, perhaps AIX)\nRequire very little in the way of setup (root access not always available!)\nBe easy for shell scripters, i.e. DBAs, to adopt, who are not hardcore developers.\nBe easy to understand other people's code\nFriendly with SQL Server and Oracle, without messing around.\nA few nice XML features wouldn't go amiss.\n\nIt would be preferable if it would run on the JVM, since this will almost always be installed on every server (certainly on all application servers) and we have many Java developers in our company, so sticking to the JVM makes sense.  This isn't exclusive though, since I know Python is a very viable language here.\nI have created a list of options, but there may be more: Groovy, Scala, Jython, Python, Ruby, Perl. \nNo one has much experience of any, except I have quite a lot of Java and Groovy experience myself.  We are looking for something dynamic, easy to pick up, will work with both SQL server and Oracle effortlessly, has some XML simplifying features, and that won't be a turnoff for DBAs.  Many of us are very Bash orientated - what could move us away from this addiction?\nWhat are people's opinions on this?\nthanks!\nChris","AnswerCount":6,"Available Count":5,"Score":0.0333209931,"is_accepted":false,"ViewCount":3213,"Q_Id":3564177,"Users Score":1,"Answer":"Although I prefer working on the JVM, one thing that turns me off is having to spin up a JVM to run a script. If you can work in a REPL this is not such a big deal, but it really slows you down when doing edit-run-debug scripting. \nNow of course Oracle has a lot of Java stuff where interaction moght be needed, but that is something only you can estimate how important it is. For plain Oracle DB work I have seen very little Java and lots fo PLSQL\/SQL.\nIf your dba now do their work in bash, then they will very likely pickup perl in a short time as there is a nice, logical progression path.\nSince ruby was designed to be an improved version of perl, it might fit in that category too. Actually python also. \nScala is statically typed like Java, albeit with much better type inference.\nMy recommendation would be to go the Perl route. The CPAN is its ace in the hole, you do not have to deal with the OO stuff which might turn off some DBA's (although it is there for the  power users).","Q_Score":6,"Tags":"python,scala,groovy,shell,jython","A_Id":3564251,"CreationDate":"2010-08-25T08:47:00.000","Title":"Which cross platform scripting language should we adopt for a group of DBAs?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":0},{"Question":"I wanted to get the community's feedback on a language choice our team is looking to make in the near future.  We are a software developer, and I work in a team of Oracle and SQL Server DBAs supporting a cross platform Java application which runs on Oracle Application Server.  We have SQL Server and Oracle code bases, and support customers on Windows, Solaris and Linux servers.\nMany of the tasks we do on a frequent basis are insufficiently automated, and where they are, tend to be much more automated via shell scripts, with little equivalent functionality on Windows.  Unfortunately, we now have this problem of redeveloping scripts and so on, on two platforms.  So, I wish for us to choose a cross platform language to script in, instead of using Bash and awkwardly translating to Cygwin or Batch files where necessary.\nIt would need to be:\n\nDynamic (so don't suggest Java or C!)\nEasily available on each platform (Windows, Solaris, Linux, perhaps AIX)\nRequire very little in the way of setup (root access not always available!)\nBe easy for shell scripters, i.e. DBAs, to adopt, who are not hardcore developers.\nBe easy to understand other people's code\nFriendly with SQL Server and Oracle, without messing around.\nA few nice XML features wouldn't go amiss.\n\nIt would be preferable if it would run on the JVM, since this will almost always be installed on every server (certainly on all application servers) and we have many Java developers in our company, so sticking to the JVM makes sense.  This isn't exclusive though, since I know Python is a very viable language here.\nI have created a list of options, but there may be more: Groovy, Scala, Jython, Python, Ruby, Perl. \nNo one has much experience of any, except I have quite a lot of Java and Groovy experience myself.  We are looking for something dynamic, easy to pick up, will work with both SQL server and Oracle effortlessly, has some XML simplifying features, and that won't be a turnoff for DBAs.  Many of us are very Bash orientated - what could move us away from this addiction?\nWhat are people's opinions on this?\nthanks!\nChris","AnswerCount":6,"Available Count":5,"Score":0.0,"is_accepted":false,"ViewCount":3213,"Q_Id":3564177,"Users Score":0,"Answer":"I've been in a similar situation, though on a small scale. The previous situation was that any automation on the SQL Server DBs was done with VBScript, which I did start out using. As I wanted something cross-platform (and less annoying than VBScript) I went with Python. \nWhat I learnt is:\n\nObviously you want a language that comes with libraries to access your databases comfortably. I wasn't too concerned with abstracting the differences away (ie, I still wrote SQL queries in the relevant dialect, with parameters). However, I'd be a bit less happy with PHP, for example, which has only very vendor-specific libraries and functions for certain databases. I see it's not on your list.\nTHE major obstacle was authentication. If your SQL Server uses Windows domain authentication, you'll have to work to get in. Another system also had specific needs as it required RSA tokens to be supported. \n\nFor the second point, Python is quite versatile enough to work around the difficulties, but it was getting into \"badly supported\" territory, especially on Windows. It was easy to work around the first problem from a Windows host, and for a Unix host it is possible though not easy. If you're using SQL Server authentication, it becomes a lot easier.\nFrom your other choices, I'd expect various ways of authenticating and DB drivers to exist for Perl, which philosophically would be easier for DBAs used to shell scripting. Ruby - no experience, but it tends to have spotty support for some of the odder authentication methods and connectors. Scala I'd expect to be a bit too much of a \"programmer's programming language\" -- OOO and FP? It's a very interesting language, but maybe not the one I'd chose at first. As for the rest of the Java-based options, I don't have an opinion, but do check that all the connection types you want to make are solidly supported.","Q_Score":6,"Tags":"python,scala,groovy,shell,jython","A_Id":3564285,"CreationDate":"2010-08-25T08:47:00.000","Title":"Which cross platform scripting language should we adopt for a group of DBAs?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":0},{"Question":"I wanted to get the community's feedback on a language choice our team is looking to make in the near future.  We are a software developer, and I work in a team of Oracle and SQL Server DBAs supporting a cross platform Java application which runs on Oracle Application Server.  We have SQL Server and Oracle code bases, and support customers on Windows, Solaris and Linux servers.\nMany of the tasks we do on a frequent basis are insufficiently automated, and where they are, tend to be much more automated via shell scripts, with little equivalent functionality on Windows.  Unfortunately, we now have this problem of redeveloping scripts and so on, on two platforms.  So, I wish for us to choose a cross platform language to script in, instead of using Bash and awkwardly translating to Cygwin or Batch files where necessary.\nIt would need to be:\n\nDynamic (so don't suggest Java or C!)\nEasily available on each platform (Windows, Solaris, Linux, perhaps AIX)\nRequire very little in the way of setup (root access not always available!)\nBe easy for shell scripters, i.e. DBAs, to adopt, who are not hardcore developers.\nBe easy to understand other people's code\nFriendly with SQL Server and Oracle, without messing around.\nA few nice XML features wouldn't go amiss.\n\nIt would be preferable if it would run on the JVM, since this will almost always be installed on every server (certainly on all application servers) and we have many Java developers in our company, so sticking to the JVM makes sense.  This isn't exclusive though, since I know Python is a very viable language here.\nI have created a list of options, but there may be more: Groovy, Scala, Jython, Python, Ruby, Perl. \nNo one has much experience of any, except I have quite a lot of Java and Groovy experience myself.  We are looking for something dynamic, easy to pick up, will work with both SQL server and Oracle effortlessly, has some XML simplifying features, and that won't be a turnoff for DBAs.  Many of us are very Bash orientated - what could move us away from this addiction?\nWhat are people's opinions on this?\nthanks!\nChris","AnswerCount":6,"Available Count":5,"Score":0.1325487884,"is_accepted":false,"ViewCount":3213,"Q_Id":3564177,"Users Score":4,"Answer":"The XML thing almost calls for Scala. Now, I love Scala, but I suggest Python here.","Q_Score":6,"Tags":"python,scala,groovy,shell,jython","A_Id":3565446,"CreationDate":"2010-08-25T08:47:00.000","Title":"Which cross platform scripting language should we adopt for a group of DBAs?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":0},{"Question":"I wanted to get the community's feedback on a language choice our team is looking to make in the near future.  We are a software developer, and I work in a team of Oracle and SQL Server DBAs supporting a cross platform Java application which runs on Oracle Application Server.  We have SQL Server and Oracle code bases, and support customers on Windows, Solaris and Linux servers.\nMany of the tasks we do on a frequent basis are insufficiently automated, and where they are, tend to be much more automated via shell scripts, with little equivalent functionality on Windows.  Unfortunately, we now have this problem of redeveloping scripts and so on, on two platforms.  So, I wish for us to choose a cross platform language to script in, instead of using Bash and awkwardly translating to Cygwin or Batch files where necessary.\nIt would need to be:\n\nDynamic (so don't suggest Java or C!)\nEasily available on each platform (Windows, Solaris, Linux, perhaps AIX)\nRequire very little in the way of setup (root access not always available!)\nBe easy for shell scripters, i.e. DBAs, to adopt, who are not hardcore developers.\nBe easy to understand other people's code\nFriendly with SQL Server and Oracle, without messing around.\nA few nice XML features wouldn't go amiss.\n\nIt would be preferable if it would run on the JVM, since this will almost always be installed on every server (certainly on all application servers) and we have many Java developers in our company, so sticking to the JVM makes sense.  This isn't exclusive though, since I know Python is a very viable language here.\nI have created a list of options, but there may be more: Groovy, Scala, Jython, Python, Ruby, Perl. \nNo one has much experience of any, except I have quite a lot of Java and Groovy experience myself.  We are looking for something dynamic, easy to pick up, will work with both SQL server and Oracle effortlessly, has some XML simplifying features, and that won't be a turnoff for DBAs.  Many of us are very Bash orientated - what could move us away from this addiction?\nWhat are people's opinions on this?\nthanks!\nChris","AnswerCount":6,"Available Count":5,"Score":0.1651404129,"is_accepted":false,"ViewCount":3213,"Q_Id":3564177,"Users Score":5,"Answer":"I think your best three options are Groovy, Python, and Scala.  All three let you write code at a high level (compared to C\/Java).  Python has its own perfectly adequate DB bindings, and Groovy and Scala can use ones made for Java.\nThe advantages of Python are that it is widely used already, so there are tons of tools, libraries, expertise, etc. available around it.  It has a particularly clean syntax, which makes working with it aesthetically pleasing.  The disadvantages are that it is slow (which may not be an issue for you), untyped (so you have runtime errors instead of compile-time errors), and you can't really switch back and forth between Jython and Python, so you have to pick whether you want the large amount of Python stuff, or the huge amount of Java stuff, minus a lot of the nice Python stuff.\nThe advantages of Groovy are that you know it already and it interoperates well with Java libraries.  Its disadvantages are also slowness and lack of static typing.  (So in contrast to Python, the choice is: do you value Python's clean syntax and wide adoption more, or do you value the vast set of Java libraries more in a language made to work well in that environment?)\nThe advantages of Scala are that it is statically typed (i.e. if the code gets past the compiler, it has a greater chance of working), is fast (as fast as Java if you care to work hard enough), and interoperates well with Java libraries.  The disadvantages are that it imposes a bit more work on you to make the static typing work (though far, far less than Java while simultaneously being more safe), and that the canonical style for Scala is a hybrid object\/functional blend that feels more different than the other two (and thus requires more training to use at full effectiveness IMO).  In contrast to Groovy, the question would be whether familiarity and ease of getting started is more important than speed and correctness.\nPersonally, I now do almost all of my work in Scala because my work requires speed and because the compiler catches those sort of errors in coding that I commonly make (so it is the only language I've used where I am not surprised when large blocks of code run correctly once I get them to compile).  But I've had good experiences with Python in other contexts--interfacing with large databases seems like a good use-case.\n(I'd rule out Perl as being harder to maintain with no significant benefits over e.g. Python, and I'd rule out Ruby as being not enough more powerful than Python to warrant the less-intuitive syntax and lower rate of adoption\/tool availability.)","Q_Score":6,"Tags":"python,scala,groovy,shell,jython","A_Id":3568609,"CreationDate":"2010-08-25T08:47:00.000","Title":"Which cross platform scripting language should we adopt for a group of DBAs?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":0},{"Question":"I wanted to get the community's feedback on a language choice our team is looking to make in the near future.  We are a software developer, and I work in a team of Oracle and SQL Server DBAs supporting a cross platform Java application which runs on Oracle Application Server.  We have SQL Server and Oracle code bases, and support customers on Windows, Solaris and Linux servers.\nMany of the tasks we do on a frequent basis are insufficiently automated, and where they are, tend to be much more automated via shell scripts, with little equivalent functionality on Windows.  Unfortunately, we now have this problem of redeveloping scripts and so on, on two platforms.  So, I wish for us to choose a cross platform language to script in, instead of using Bash and awkwardly translating to Cygwin or Batch files where necessary.\nIt would need to be:\n\nDynamic (so don't suggest Java or C!)\nEasily available on each platform (Windows, Solaris, Linux, perhaps AIX)\nRequire very little in the way of setup (root access not always available!)\nBe easy for shell scripters, i.e. DBAs, to adopt, who are not hardcore developers.\nBe easy to understand other people's code\nFriendly with SQL Server and Oracle, without messing around.\nA few nice XML features wouldn't go amiss.\n\nIt would be preferable if it would run on the JVM, since this will almost always be installed on every server (certainly on all application servers) and we have many Java developers in our company, so sticking to the JVM makes sense.  This isn't exclusive though, since I know Python is a very viable language here.\nI have created a list of options, but there may be more: Groovy, Scala, Jython, Python, Ruby, Perl. \nNo one has much experience of any, except I have quite a lot of Java and Groovy experience myself.  We are looking for something dynamic, easy to pick up, will work with both SQL server and Oracle effortlessly, has some XML simplifying features, and that won't be a turnoff for DBAs.  Many of us are very Bash orientated - what could move us away from this addiction?\nWhat are people's opinions on this?\nthanks!\nChris","AnswerCount":6,"Available Count":5,"Score":1.0,"is_accepted":false,"ViewCount":3213,"Q_Id":3564177,"Users Score":6,"Answer":"You can opt for Python. Its dynamic(interpreted) , is available on Windows\/Linux\/Solaris, has easy to read syntax so that your code maintenance is easy. There modules\/libraries for Oracle interaction and various other database servers as well. there are also library support for XML. All 7 points are covered.","Q_Score":6,"Tags":"python,scala,groovy,shell,jython","A_Id":3564413,"CreationDate":"2010-08-25T08:47:00.000","Title":"Which cross platform scripting language should we adopt for a group of DBAs?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":0},{"Question":"I have been developing under Python\/Snowleopard happily for the part 6 months. I just upgraded Python to 2.6.5 and a whole bunch of libraries, including psycopg2 and Turbogears. I can start up tg-admin and run some queries with no problems. Similarly, I can run my web site from the command line with no problems. \nHowever, if I try to start my application under Aptana Studio, I get the following exception while trying to import psychopg2:\n('dlopen(\/Library\/Frameworks\/Python.framework\/Versions\/2.6\/lib\/python2.6\/site-packages\/psycopg2\/_psycopg.so, 2): Symbol not found: _PQbackendPID\\n  Referenced from: \/Library\/Frameworks\/Python.framework\/Versions\/2.6\/lib\/python2.6\/site-packages\/psycopg2\/_psycopg.so\\n  Expected in: flat namespace\\n in \/Library\/Frameworks\/Python.framework\/Versions\/2.6\/lib\/python2.6\/site-packages\/psycopg2\/_psycopg.so',)\nThis occurs after running the following code:\n    try:\n        import psycopg2 as psycopg\n    except ImportError as ex:\n         print \"import failed :-( xxxxxxxx = \"\n         print ex.args\nI have confirmed that the same version of python is being run as follows:\n        import sys\n        print \"python version: \", sys.version_info\nDoes anyone have any ideas? I've seem some references alluding to this being a 64-bit issue.\n- dave","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":296,"Q_Id":3571495,"Users Score":0,"Answer":"Problem solved (to a point). I was running 64 bit python from Aptana Studio and 32 bit python on the command line. By forcing Aptana to use 32 bit python, the libraries work again and all is happy.","Q_Score":0,"Tags":"python,turbogears,psycopg","A_Id":3571749,"CreationDate":"2010-08-26T01:41:00.000","Title":"Psycopg2 under osx works on commandline but fails in Aptana studio","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm using a linux machine to make a little python program that needs to input its result in a SQL Server 2000 DB.\nI'm new to python so I'm struggling quite a bit to find what's the best solution to connect to the DB using python 3, since most of the libs I looked only work in python 2.\nAs an added bonus question, the finished version of this will be compiled to a windows program using py2exe. Is there anything I should be aware of, any changes to make?\nThanks","AnswerCount":3,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":1786,"Q_Id":3571819,"Users Score":0,"Answer":"If you want to have portable mssql server library, you can try the module from www.pytds.com. It works with 2.5+ AND 3.1, have a good stored procedure support. It's api is more \"functional\", and has some good features you won't find anywhere else.","Q_Score":1,"Tags":"python,sql-server,python-3.x,py2exe","A_Id":4062244,"CreationDate":"2010-08-26T03:18:00.000","Title":"How to access a MS SQL Server using Python 3?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm using a linux machine to make a little python program that needs to input its result in a SQL Server 2000 DB.\nI'm new to python so I'm struggling quite a bit to find what's the best solution to connect to the DB using python 3, since most of the libs I looked only work in python 2.\nAs an added bonus question, the finished version of this will be compiled to a windows program using py2exe. Is there anything I should be aware of, any changes to make?\nThanks","AnswerCount":3,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":1786,"Q_Id":3571819,"Users Score":0,"Answer":"I can't answer your question directly, but given that many popular Python packages and frameworks are not yet fully supported on Python 3, you might consider just using Python 2.x. Unless there are features you absolutely cannot live without in Python 3, of course.\nAnd it isn't clear from your post if you plan to deploy to Windows only, or Windows and Linux. If it's only Windows, then you should probably just develop on Windows to start with: the native MSSQL drivers are included in most recent versions so you don't have anything extra to install, and it gives you more options, such as adodbapi.","Q_Score":1,"Tags":"python,sql-server,python-3.x,py2exe","A_Id":3573005,"CreationDate":"2010-08-26T03:18:00.000","Title":"How to access a MS SQL Server using Python 3?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Since mongo doesn't have a schema, does that mean that we won't have to do migrations when we change the models?\nWhat does the migration process look like with a non-relational db?","AnswerCount":3,"Available Count":2,"Score":0.0665680765,"is_accepted":false,"ViewCount":5660,"Q_Id":3604565,"Users Score":1,"Answer":"What does the migration process look like with a non-relational db?\n\nDepends on if you need to update all the existing data or not. \nIn many cases, you may not need to touch the old data, such as when adding a new optional field. If that field also has a default value, you may also not need to update the old documents, if your application can handle a missing field correctly. However, if you want to build an index on the new field to be able to search\/filter\/sort, you need to add the default value back into the old documents.\nSomething like field renaming (trivial in a relational db, because you only need to update the catalog and not touch any data) is a major undertaking in MongoDB (you need to rewrite all documents).\nIf you need to update the existing data, you usually have to write a migration function that iterates over all the documents and updates them one by one (although this process can be shared and run in parallel). For large data sets, this can take a lot of time (and space), and you may miss transactions (if you end up with a crashed migration that went half-way through).","Q_Score":18,"Tags":"python,django,mongodb","A_Id":3605615,"CreationDate":"2010-08-30T22:01:00.000","Title":"Does django with mongodb make migrations a thing of the past?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Since mongo doesn't have a schema, does that mean that we won't have to do migrations when we change the models?\nWhat does the migration process look like with a non-relational db?","AnswerCount":3,"Available Count":2,"Score":0.1325487884,"is_accepted":false,"ViewCount":5660,"Q_Id":3604565,"Users Score":2,"Answer":"There is no silver bullet. Adding or removing fields is easier with non-relational db (just don't use unneeded fields or use new fields), renaming a field is easier with traditional db (you'll usually have to change a lot of data in case of field rename in schemaless db), data migration is on par - depending on task.","Q_Score":18,"Tags":"python,django,mongodb","A_Id":3604687,"CreationDate":"2010-08-30T22:01:00.000","Title":"Does django with mongodb make migrations a thing of the past?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Is it even possible to create an abstraction layer that can accommodate relational and non-relational databases? The purpose of this layer is to minimize repetition and allows a web application to use any kind of database by just changing\/modifying the code in one place (ie, the abstraction layer). The part that sits on top of the abstraction layer must not need to worry whether the underlying database is relational (SQL) or non-relational (NoSQL) or whatever new kind of database that may come out later in the future.","AnswerCount":5,"Available Count":3,"Score":1.2,"is_accepted":true,"ViewCount":1721,"Q_Id":3606215,"Users Score":0,"Answer":"Thank you for all the answers. To summarize the answers, currently only web2py and Django supports this kind of abstraction. \nIt is not about a SQL-NoSQL holy grail, using abstraction can make the apps more flexible. Lets assume that you started a project using NoSQL, and then later on you need to switch over to SQL. It is desirable that you only make changes to the codes in a few spots instead of all over the place. For some cases, it does not really matter whether you store the data in a relational or non-relational db. For example, storing user profiles, text content for dynamic page, or blog entries.\nI know there must be a trade off by using the abstraction, but my question is more about the existing solution or technical insight, instead of the consequences.","Q_Score":2,"Tags":"python,sql,database,google-app-engine,nosql","A_Id":3649176,"CreationDate":"2010-08-31T05:18:00.000","Title":"Is there any python web app framework that provides database abstraction layer for SQL and NoSQL?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Is it even possible to create an abstraction layer that can accommodate relational and non-relational databases? The purpose of this layer is to minimize repetition and allows a web application to use any kind of database by just changing\/modifying the code in one place (ie, the abstraction layer). The part that sits on top of the abstraction layer must not need to worry whether the underlying database is relational (SQL) or non-relational (NoSQL) or whatever new kind of database that may come out later in the future.","AnswerCount":5,"Available Count":3,"Score":0.0399786803,"is_accepted":false,"ViewCount":1721,"Q_Id":3606215,"Users Score":1,"Answer":"Regarding App Engine, all existing attempts limit you in some way (web2py doesn't support transactions or namespaces and probably many other stuff, for example). If you plan to work with GAE, use what GAE provides and forget looking for a SQL-NoSQL holy grail. Existing solutions are inevitably limited and affect performance negatively.","Q_Score":2,"Tags":"python,sql,database,google-app-engine,nosql","A_Id":3609648,"CreationDate":"2010-08-31T05:18:00.000","Title":"Is there any python web app framework that provides database abstraction layer for SQL and NoSQL?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Is it even possible to create an abstraction layer that can accommodate relational and non-relational databases? The purpose of this layer is to minimize repetition and allows a web application to use any kind of database by just changing\/modifying the code in one place (ie, the abstraction layer). The part that sits on top of the abstraction layer must not need to worry whether the underlying database is relational (SQL) or non-relational (NoSQL) or whatever new kind of database that may come out later in the future.","AnswerCount":5,"Available Count":3,"Score":0.0399786803,"is_accepted":false,"ViewCount":1721,"Q_Id":3606215,"Users Score":1,"Answer":"Yo may also check web2py, they support relational databases and GAE on the core.","Q_Score":2,"Tags":"python,sql,database,google-app-engine,nosql","A_Id":3606610,"CreationDate":"2010-08-31T05:18:00.000","Title":"Is there any python web app framework that provides database abstraction layer for SQL and NoSQL?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Can you recommend a high-performance, thread-safe and stable ORM for Python? The data I need to work with isn't complex, so SQLAlchemy is probably an overkill.","AnswerCount":4,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":3631,"Q_Id":3607285,"Users Score":6,"Answer":"If you are looking for something thats high performance, and based on one of your comments \"something that can handle >5k queries per second\". You need to keep in mind that an ORM is not built specifically for speed and performance, it is built for maintainability and ease of use. If the data is so basic that even SqlAlchemy might be overkill, and your mostly doing writes, it might be easier to just do straight inserts and skip the ORM altogether.","Q_Score":3,"Tags":"python,orm","A_Id":3609616,"CreationDate":"2010-08-31T08:25:00.000","Title":"Fast, thread-safe Python ORM?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"i'm using IronPython 2.6 for .Net4 to build an GUI logging application.\nThis application received data via serialport and stores these data in an sqlite3 database while showing the last 100 received items in an listview. The listview gathers it's data via an SQL SELECT from the database every 100ms. It only querys data that is not already visible in the listview.\nAt first, the useage of the sqlite3 module was good and solid but i'm now stuck with several issues that i can't solve. \nThe sqlite3 module throws after a while exceptions like: \n\ndatabase disk image is malformed\ndatabase or disk is full.\n\nThese errors occur sporadic and never under high system load.\nI stuck with this kind if issues for some weeks now and i'm looking for an alternative way to store binary and ascii data in a database-like object.\nPlease, does somebody know a good database solution i could use with IronPython 2.6 for .Net4?\nThanks","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":495,"Q_Id":3616078,"Users Score":0,"Answer":"good \n\nThat is highly subjective without far more detailed requirements.\nYou should be able to use any database with .NET support, whether out of the box (notably SQL Server Express and Compact) or installed separately (SQL Server-other editions, DB2, MySQL, Oracle, ...).\nTen select commands per second should be easily in each of any of the databases above, unless there is some performance issue (e.g. huge amount of data and not able to use an index).","Q_Score":0,"Tags":"database,ironpython","A_Id":3616111,"CreationDate":"2010-09-01T08:04:00.000","Title":"IronPython - What kind of database is useable","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I use Python and MySQLdb to download web pages and store them into database. The problem I have is that I can't save complicated strings in the database because they are not properly escaped.\nIs there a function in Python that I can use to escape a string for MySQL? I tried with ''' (triple simple quotes) and \"\"\", but it didn't work. I know that PHP has mysql_escape_string(), is something similar in Python?\nThanks.","AnswerCount":7,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":144313,"Q_Id":3617052,"Users Score":0,"Answer":"One other way to work around this is using something like this when using mysqlclient in python.\nsuppose the data you want to enter is like this <ol><li><strong style=\"background-color: rgb(255, 255, 0);\">Saurav\\'s List<\/strong><\/li><\/ol>. It contains both double qoute and single quote.\nYou can use the following method to escape the quotes:\n\nstatement = \"\"\" Update chats set html='{}' \"\"\".format(html_string.replace(\"'\",\"\\\\\\'\"))\n\nNote: three \\ characters are needed to escape the single quote which is there in unformatted python string.","Q_Score":77,"Tags":"python,mysql,escaping","A_Id":61042304,"CreationDate":"2010-09-01T10:23:00.000","Title":"Escape string Python for MySQL","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm having a right old nightmare with JPype. I have got my dev env on Windows and so tried installing it there with no luck. I then tried on Ubunto also with no luck. I'm getting a bit desperate now. I am using Mingw32 since I tried installing VS2008 but it told me I had to install XP SP2 but I am on Vista. I tried VS2010 but no luck, I got the 'error: Unable to find vcvarsall.bat' error. Anyway, I am now on Mingw32\nUltimately I am trying to use Neo4j and Python hence my need to use JPype. I have found so many references to the problem on the net for MySQL etc but they don't help me with JPype. \nIf I could fix unix or windows I could get going so help on either will be really appreciated. \nHere's the versions..\nWindows: Vista 64\nPython: 2.6\nCompiler Mingw32: latest version\nJpype: 0.5.4.1\nJava info: \njava version \"1.6.0_13\"\nJava(TM) SE Runtime Environment (build 1.6.0_13-b03)\nJava HotSpot(TM) 64-Bit Server VM (build 11.3-b02, mixed mode)\nI run:\npython setup.py install --compiler=wingw32 \nand get the following output.\nChoosing the Windows profile\nrunning install\nrunning build\nrunning build_py\nrunning build_ext\nbuilding '_jpype' extension\nC:\\MinGW\\bin\\gcc.exe -mno-cygwin -mdll -O -Wall -DWIN32=1 \"-IC:\\Program Files (x86)\\Java\\jdk1.6.0_21\/include\" \"-IC:\\Program Files (x86)\\Java\\jdk1.6.0_21\/include\/win32\" -Isrc\/native\/common\/include -Isrc\/native\/python\/include -Ic:\\Python26\\include -Ic:\\Python26\\PC -c src\/native\/common\/jp_array.cpp -o build\\temp.win32-2.6\\Release\\src\\native\\common\\jp_array.o \/EHsc\nsrc\/native\/common\/jp_array.cpp: In member function 'void JPArray::setRange(int, int, std::vector&)':\nsrc\/native\/common\/jp_array.cpp:56:13: warning: comparison between signed and unsigned integer expressions\nsrc\/native\/common\/jp_array.cpp:68:4: warning: deprecated conversion from string constant to 'char*'\nsrc\/native\/common\/jp_array.cpp: In member function 'void JPArray::setItem(int, HostRef*)':\nsrc\/native\/common\/jp_array.cpp:80:3: warning: deprecated conversion from string constant to 'char*'\ngcc: \/EHsc: No such file or directory\nerror: command 'gcc' failed with exit status 1\nSo on unix Ubunto the problem is as follows:\nJava version: 1.6.0_18\nJPype: 0.5.4.1\nPython: 2.6\nJava is in the path and I did apt-get install build-essentials just now so have latest GCC etc. \nI won't paste all the output as it's massive. So many errors it's like I have missed the install of Java or similar but I haven't. typing java takes me into version above. This is the beginning:\nrunning install\nrunning build\nrunning build_py\nrunning build_ext\nbuilding '_jpype' extension\ngcc -pthread -fno-strict-aliasing -DNDEBUG -g -fwrapv -O2 -Wall -Wstrict-prototypes -fPIC -I\/usr\/lib\/jvm\/java-1.5.0-sun-1.5.0.08\/include -I\/usr\/lib\/jvm\/java-1.5.0-sun-1.5.0.08\/include\/linux -Isrc\/native\/common\/include -Isrc\/native\/python\/include -I\/usr\/include\/python2.6 -c src\/native\/common\/jp_javaenv_autogen.cpp -o build\/temp.linux-i686-2.6\/src\/native\/common\/jp_javaenv_autogen.o\ncc1plus: warning: command line option \"-Wstrict-prototypes\" is valid for Ada\/C\/ObjC but not for C++\nIn file included from src\/native\/common\/jp_javaenv_autogen.cpp:21:\nsrc\/native\/common\/include\/jpype.h:45:17: error: jni.h: No such file or directory\nIn file included from src\/native\/common\/jp_javaenv_autogen.cpp:21:\nsrc\/native\/common\/include\/jpype.h:77: error: ISO C++ forbids declaration of \u2018jchar\u2019 with no type\nsrc\/native\/common\/include\/jpype.h:77: error: expected \u2018,\u2019 or \u2018...\u2019 before \u2018\u2019 token\nsrc\/native\/common\/include\/jpype.h:82: error: ISO C++ forbids declaration of \u2018jchar\u2019 with no type\nsrc\/native\/common\/include\/jpype.h:82: error: expected \u2018;\u2019 before \u2018\u2019 token\nsrc\/native\/common\/include\/jpype.h:86: error: ISO C++ forbids declaration of \u2018jchar\u2019 with no type\nsrc\/native\/common\/include\/jpype.h:86: error: expected \u2018;\u2019 before \u2018&\u2019 token\nsrc\/native\/common\/include\/jpype.h:88: error: expected \u2018;\u2019 before \u2018private\u2019\nsrc\/native\/common\/include\/jpype.h:89: error: ISO C++ forbids declaration of \u2018jchar\u2019 with no type\nsrc\/native\/common\/include\/jpype.h:89: error: expected \u2018;\u2019 before \u2018*\u2019 token\nIn file included from src\/native\/common\/include\/jpype.h:96,\n                 from src\/native\/common\/jp_javaenv_autogen.cpp:21:\nAnd this is the end:\nsrc\/native\/common\/include\/jp_monitor.h:27: error: \u2018jobject\u2019 does not name a type\nsrc\/native\/common\/jp_javaenv_autogen.cpp:30: error: \u2018jbyte\u2019 does not name a type\nsrc\/native\/common\/jp_javaenv_autogen.cpp:38: error: \u2018jbyte\u2019 does not name a type\nsrc\/native\/common\/jp_javaenv_autogen.cpp:45: error: variable or field \u2018SetStaticByteField\u2019 declared void\nsrc\/native\/common\/jp_javaenv_autogen.cpp:45: error: \u2018jclass\u2019 was not declared in this scope\nsrc\/native\/common\/jp_javaenv_autogen.cpp:45: error: \u2018jfieldID\u2019 was not declared in this scope\nsrc\/native\/common\/jp_javaenv_autogen.cpp:45: error: \u2018jbyte\u2019 was not declared in this scope\nerror: command 'gcc' failed with exit status 1","AnswerCount":3,"Available Count":1,"Score":0.0665680765,"is_accepted":false,"ViewCount":3736,"Q_Id":3649577,"Users Score":1,"Answer":"Edit the Setup.py and remove the \/EHsc option.","Q_Score":3,"Tags":"java,python","A_Id":6258169,"CreationDate":"2010-09-06T06:54:00.000","Title":"JPype compile problems","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":1,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a Twisted application that runs in an x86 64bit machine with Win 2008 server. \nIt needs to be connected to a SQL Server database that runs in another machine (in a cloud actually but I have IP, port, db name, credentials).\nDo I need to install anything more that Twisted to my machine?\nAnd which API should be used?","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":1128,"Q_Id":3657271,"Users Score":1,"Answer":"If you want to have portable mssql server library, you can try the module from www.pytds.com.\nIt works with 2.5+ and 3.1, have a good stored procedure support. It's api is more \"functional\", and has some good features you won't find anywhere else.","Q_Score":0,"Tags":"python,sql-server,twisted","A_Id":4059366,"CreationDate":"2010-09-07T09:07:00.000","Title":"Twisted and connection to SQL Server","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":0},{"Question":"I'm creating a basic database utility class in Python. I'm refactoring an old module into a class. I'm now working on an executeQuery() function, and I'm unsure of whether to keep the old design or change it. Here are the 2 options:\n\n(The old design:) Have one generic executeQuery method that takes the query to execute and a boolean commit parameter that indicates whether to commit (insert, update, delete) or not (select), and determines with an if statement whether to commit or to select and return.\n(This is the way I'm used to, but that might be because you can't have a function that sometimes returns something and sometimes doesn't in the languages I've worked with:) Have 2 functions, executeQuery and executeUpdateQuery (or something equivalent). executeQuery will execute a simple query and return a result set, while executeUpdateQuery will make changes to the DB (insert, update, delete) and return nothing.\n\nIs it accepted to use the first way? It seems unclear to me, but maybe it's more Pythonistic...? Python is very flexible, maybe I should take advantage of this feature that can't really be accomplished in this way in more strict languages...\nAnd a second part of this question, unrelated to the main idea - what is the best way to return query results in Python? Using which function to query the database, in what format...?","AnswerCount":3,"Available Count":1,"Score":0.2605204458,"is_accepted":false,"ViewCount":174,"Q_Id":3662134,"Users Score":4,"Answer":"It's propably just me and my FP fetish, but I think a function executed solely for side effects is very different from a non-destructive function that fetches some data, and therefore have different names. Especially if the generic function would do something different depending on exactly that (the part on the commit parameter seems to imply that).\nAs for how to return results... I'm a huge fan of generators, but if the library you use for database connections returns a list anyway, you might as well pass this list on - a generator wouldn't buy you anything in this case. But if it allows you to iterate over the results (one at a time), seize the opportunity to save a lot of memory on larger queries.","Q_Score":3,"Tags":"python,oop","A_Id":3662258,"CreationDate":"2010-09-07T19:47:00.000","Title":"Design question in Python: should this be one generic function or two specific ones?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"AFAIK SQLite returns unicode objects for TEXT in Python. Is it possible to get SQLite to return string objects instead?","AnswerCount":3,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":7275,"Q_Id":3666328,"Users Score":0,"Answer":"Use Python 3.2+. It will automatically return string instead of unicode (as in Python 2.7)","Q_Score":3,"Tags":"python,string,sqlite,unicode","A_Id":25273292,"CreationDate":"2010-09-08T09:31:00.000","Title":"Can I get SQLite to string instead of unicode for TEXT in Python?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"AFAIK SQLite returns unicode objects for TEXT in Python. Is it possible to get SQLite to return string objects instead?","AnswerCount":3,"Available Count":2,"Score":0.2605204458,"is_accepted":false,"ViewCount":7275,"Q_Id":3666328,"Users Score":4,"Answer":"TEXT is intended to store text. Use BLOB if you want to store bytes.","Q_Score":3,"Tags":"python,string,sqlite,unicode","A_Id":3666433,"CreationDate":"2010-09-08T09:31:00.000","Title":"Can I get SQLite to string instead of unicode for TEXT in Python?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I created a new Pylons project, and would like to use Cassandra as my database server. I plan on using Pycassa to be able to use cassandra 0.7beta.\nUnfortunately, I don't know where to instantiate the connection to make it available in my application. \nThe goal would be to :\n\nCreate a pool when the application is launched\nGet a connection from the pool for each request, and make it available to my controllers and libraries (in the context of the request). The best would be to get a connexion from the pool \"lazily\", i.e. only if needed\nIf a connexion has been used, release it when the request has been processed\n\nAdditionally, is there something important I should know about it ? When I see some comments like \"Be careful when using a QueuePool with use_threadlocal=True, especially with retries enabled.  Synchronization may be required to prevent the connection from changing while another thread is using it.\", what does it mean exactly ?\nThanks.\n--\nPierre","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":885,"Q_Id":3671535,"Users Score":2,"Answer":"Well. I worked a little more. In fact, using a connection manager was probably not a good idea as this should be the template context. Additionally, opening a connection for each thread is not really a big deal. Opening a connection per request would be.\nI ended up with just pycassa.connect_thread_local() in app_globals, and there I go.","Q_Score":10,"Tags":"python,pylons,cassandra","A_Id":3687133,"CreationDate":"2010-09-08T20:14:00.000","Title":"How to connect to Cassandra inside a Pylons app?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":0},{"Question":"We have a Django project which runs on Google App Engine and used db.UserProperty in several models. We don't have an own User model.\nMy boss would like to use RPXNow (Janrain) for authentication, but after I integrated it, the users.get_current_user() method returned None. It makes sense, because not Google authenticated me. But what should I use for db.UserProperty attributes? Is it possible to use rpxnow and still can have Google's User object as well?\nAfter this I tried to use OpenID authentication (with federated login) in my application, and it works pretty good: I still have users.get_current_user() object. As far as I know, rpxnow using openID as well, which means (for me) that is should be possible to get User objects with rpxnow. But how?\nCheers,\npsmith","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":389,"Q_Id":3699751,"Users Score":1,"Answer":"You can only get a User object if you're using one of the built-in authentication methods. User objects provide an interface to the Users API, which is handled by the App Engine infrastructure. If you're using your own authentication library, regardless of what protocol it uses, you will have to store user information differently.","Q_Score":0,"Tags":"python,google-app-engine,rpxnow","A_Id":3707639,"CreationDate":"2010-09-13T10:55:00.000","Title":"Google App Engine's db.UserProperty with rpxnow","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"Short story\nI have a technical problem with a third-party library at my hands that I seem to be unable to easily solve in a way other than creating a surrogate key (despite the fact that I'll never need it). I've read a number of articles on the Net discouraging the use of surrogate keys, and I'm a bit at a loss if it is okay to do what I intend to do.\nLong story\nI need to specify a primary key, because I use SQLAlchemy ORM (which requires one), and I cannot just set it in __mapper_args__, since the class is being built with classobj, and I have yet to find a way to reference the field of a not-yet-existing class in the appropriate PK definition argument. Another problem is that the natural equivalent of the PK is a composite key that is too long for the version of MySQL I use (and it's generally a bad idea to use such long primary keys anyway).","AnswerCount":3,"Available Count":3,"Score":1.2,"is_accepted":true,"ViewCount":698,"Q_Id":3712949,"Users Score":2,"Answer":"I always make surrogate keys when using ORMs (or rather, I let the ORMs make them for me). They solve a number of problems, and don't introduce any (major) problems.\nSo, you've done your job by acknowledging that there are \"papers on the net\" with valid reasons to avoid surrogate keys, and that there's probably a better way to do it.\nNow, write \"# TODO: find a way to avoid surrogate keys\" somewhere in your source code and go get some work done.","Q_Score":2,"Tags":"python,sqlalchemy,primary-key","A_Id":3713061,"CreationDate":"2010-09-14T21:11:00.000","Title":"How badly should I avoid surrogate primary keys in SQL?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Short story\nI have a technical problem with a third-party library at my hands that I seem to be unable to easily solve in a way other than creating a surrogate key (despite the fact that I'll never need it). I've read a number of articles on the Net discouraging the use of surrogate keys, and I'm a bit at a loss if it is okay to do what I intend to do.\nLong story\nI need to specify a primary key, because I use SQLAlchemy ORM (which requires one), and I cannot just set it in __mapper_args__, since the class is being built with classobj, and I have yet to find a way to reference the field of a not-yet-existing class in the appropriate PK definition argument. Another problem is that the natural equivalent of the PK is a composite key that is too long for the version of MySQL I use (and it's generally a bad idea to use such long primary keys anyway).","AnswerCount":3,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":698,"Q_Id":3712949,"Users Score":0,"Answer":"I use surrogate keys in a db that I use reflection on with sqlalchemy. The pro is that you can more easily manage the foreign keys \/ relationships that exists in your tables \/ models. Also, the rdbms is managing the data more efficiently. The con is the data inconsistency: duplicates. To avoid this - always use the unique constraint on your natural key.\nNow, I understand from your long story that you can't enforce this uniqueness because of your mysql limitations. For long composite keys mysql causes problems. I suggest you move to postgresql.","Q_Score":2,"Tags":"python,sqlalchemy,primary-key","A_Id":4160811,"CreationDate":"2010-09-14T21:11:00.000","Title":"How badly should I avoid surrogate primary keys in SQL?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Short story\nI have a technical problem with a third-party library at my hands that I seem to be unable to easily solve in a way other than creating a surrogate key (despite the fact that I'll never need it). I've read a number of articles on the Net discouraging the use of surrogate keys, and I'm a bit at a loss if it is okay to do what I intend to do.\nLong story\nI need to specify a primary key, because I use SQLAlchemy ORM (which requires one), and I cannot just set it in __mapper_args__, since the class is being built with classobj, and I have yet to find a way to reference the field of a not-yet-existing class in the appropriate PK definition argument. Another problem is that the natural equivalent of the PK is a composite key that is too long for the version of MySQL I use (and it's generally a bad idea to use such long primary keys anyway).","AnswerCount":3,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":698,"Q_Id":3712949,"Users Score":0,"Answer":"\"Using a surrogate key allows duplicates to be created when using a natural key would have prevented such problems\" Exactly, so you should have both keys, not just a surrogate. The error you seem to be making is not that you are using a surrogate, it's that you are assuming the table only needs one key. Make sure you create all the keys you need to ensure the integrity of your data.\nHaving said that, in this case it seems like a deficiency of the ORM software (apparently not being able to use a composite key) is the real cause of your problems. It's unfortunate that a software limitation like that should force you to create keys you don't otherwise need. Maybe you could consider using different software.","Q_Score":2,"Tags":"python,sqlalchemy,primary-key","A_Id":3713270,"CreationDate":"2010-09-14T21:11:00.000","Title":"How badly should I avoid surrogate primary keys in SQL?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have created a database in PostgreSQL, let's call it testdb.\nI have a generic set of tables inside this database, xxx_table_one, xxx_table_two and xxx_table_three.\nNow, I have Python code where I want to dynamically create and remove \"sets\" of these 3 tables to my database with a unique identifier in the table name distinguishing different \"sets\" from each other, e.g.  \nSet 1\ntestdb.aaa_table_one\ntestdb.aaa_table_two\ntestdb.aaa_table_three  \nSet 2\ntestdb.bbb_table_one\ntestdb.bbb_table_two\ntestdb.bbb_table_three  \nThe reason I want to do it this way is to keep multiple LARGE data collections of related data separate from each other. I need to regularly overwrite individual data collections, and it's easy if we can just drop the data collections table and recreate a complete new set of tables. Also, I have to mention, the different data collections fit into the same schemas, so I could save all the data collections in 1 set of tables using an identifier to distinguish data collections instead of separating them by using different tables.\nI want to know, a few things  \n Does PostgreSQL limit the number of tables per database?\nWhat is the effect on performance, if any, of having a large number of tables in 1 database?\nWhat is the effect on performance of saving the data collections in different sets of tables compared to saving them all in the same set, e.g. I guess would need to write more queries if I want to query multiple data collections at once when the data is spread accross tables as compared to just 1 set of tables.","AnswerCount":3,"Available Count":2,"Score":0.1973753202,"is_accepted":false,"ViewCount":5102,"Q_Id":3715456,"Users Score":3,"Answer":"PostgreSQL doesn't impose a direct limit on this, your OS does (it depends on maximum directory size)\nThis may depend on your OS as well. Some filesystems get slower with large directories.\nPostgreSQL won't be able to optimize queries if they're across different tables. So using less tables (or a single table) should be more efficient","Q_Score":7,"Tags":"python,mysql,database,database-design,postgresql","A_Id":3715621,"CreationDate":"2010-09-15T07:15:00.000","Title":"Is there a limitation on the number of tables a PostgreSQL database can have?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have created a database in PostgreSQL, let's call it testdb.\nI have a generic set of tables inside this database, xxx_table_one, xxx_table_two and xxx_table_three.\nNow, I have Python code where I want to dynamically create and remove \"sets\" of these 3 tables to my database with a unique identifier in the table name distinguishing different \"sets\" from each other, e.g.  \nSet 1\ntestdb.aaa_table_one\ntestdb.aaa_table_two\ntestdb.aaa_table_three  \nSet 2\ntestdb.bbb_table_one\ntestdb.bbb_table_two\ntestdb.bbb_table_three  \nThe reason I want to do it this way is to keep multiple LARGE data collections of related data separate from each other. I need to regularly overwrite individual data collections, and it's easy if we can just drop the data collections table and recreate a complete new set of tables. Also, I have to mention, the different data collections fit into the same schemas, so I could save all the data collections in 1 set of tables using an identifier to distinguish data collections instead of separating them by using different tables.\nI want to know, a few things  \n Does PostgreSQL limit the number of tables per database?\nWhat is the effect on performance, if any, of having a large number of tables in 1 database?\nWhat is the effect on performance of saving the data collections in different sets of tables compared to saving them all in the same set, e.g. I guess would need to write more queries if I want to query multiple data collections at once when the data is spread accross tables as compared to just 1 set of tables.","AnswerCount":3,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":5102,"Q_Id":3715456,"Users Score":0,"Answer":"If your data were not related, I think your tables could be in different schema, and then you would use SET search_path TO schema1, public for example, this way you wouldn't have to dynamically generate table names in your queries. I am planning to try this structure on a large database which stores logs and other tracking information.\nYou can also change your tablespace if your os has a limit or suffers from large directory size.","Q_Score":7,"Tags":"python,mysql,database,database-design,postgresql","A_Id":5603789,"CreationDate":"2010-09-15T07:15:00.000","Title":"Is there a limitation on the number of tables a PostgreSQL database can have?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am into a project where zope web server is used. With this PostgreSQL database is used. But I am not able to add a new PostgreSQL connection via zope. Actually, I am not aware of what else I need to install so that I can use PostgreSQL dB with zope. From whatever I have explored about this I have come to know that I will require a Zope Database Adapter so that I can use PostgreSQL dB with Zope. But still I am not confirmed about this. Also I don't know which version of Zope Database Adapter will I require to install? The zope version I am using is 2.6 and PostgreSQL dB version is 7.4.13 and the Python version is 2.1.3 . Also from where should I download that Zope Database Adapter?","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":110,"Q_Id":3719145,"Users Score":0,"Answer":"Look at psycopg, it ships with a Zope Database Adapter.","Q_Score":3,"Tags":"python,zope","A_Id":3719408,"CreationDate":"2010-09-15T15:24:00.000","Title":"What are the essentials I need to install if I want to use PostgreSQL DB with zope? for eg: Zope Database Adapter?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm running a web crawler that gets called as a separate thread via Django. When it tries to store the scraped information I get this error:\nFile \"\/usr\/lib\/pymodules\/python2.6\/MySQLdb\/cursors.py\", line 147, in execute\n    charset = db.character_set_name()\nInterfaceError: (0, '')\nIf I manually run the script from the command line I don't get this error. Any ideas?\nMy guess is that I do about 4 cursor.execute()s in one iteration of a loop. Could this be throwing something off?\nThanks!","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1854,"Q_Id":3722120,"Users Score":0,"Answer":"Since it mentions the character set, my gut says you are running a different Django\/Python\/something from the command line than you are from the webserver. In your settings file, turn on DEBUG=True, restart the server, and then run this again. In particular, look at the list of paths shown. If they are not exactly what you expect them to be, then this is a Red Flag.","Q_Score":0,"Tags":"python,mysql,django,multithreading","A_Id":3722799,"CreationDate":"2010-09-15T21:49:00.000","Title":"mySQL interface error only occuring if ran in Django","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have zope 2.11 installed. Now i want to use Posgresql 7.4.13 DB with it. So i know i need to install psycopg2 Database Adapter. Can any one tell me Is psycopg2 compatible with zope2??","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":142,"Q_Id":3725699,"Users Score":1,"Answer":"Yes, you can use psycopg2 with Zope2. \nJust install it in your Python with easy_install or setup.py. You will also need a matching ZPsycopgDA Product in Zope. You find the ZPsycopgDA folder in the psycopg2 source distribution tarball.","Q_Score":1,"Tags":"python,database,zope","A_Id":4018666,"CreationDate":"2010-09-16T10:19:00.000","Title":"Is Zpsycopg2 compatible with zope 2?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am building an application with objects which have their data stored in mysql tables (across multiple tables). When I need to work with the object (retrieve object attributes \/ change the attributes) I am querying the sql database using mysqldb (select \/ update). However, since the application is quite computation intensive, the execution time is killing me.\nWanted to understand if there are approaches where all of the data is loaded into python, the computations \/ modifications are done on those objects and then subsequently a full data update is done to the mysql database? Will loading the data initially into lists of those objects in one go from the database improve the performance? Also since the db size is close to around 25 mb, will it cause any memory problems.\nThanks in advance.","AnswerCount":2,"Available Count":1,"Score":0.4621171573,"is_accepted":false,"ViewCount":1287,"Q_Id":3770394,"Users Score":5,"Answer":"25Mb is tiny.  Microscopic.  SQL is slow.  Glacial.\nDo not waste time on SQL unless you have transactions (with locking and multiple users).\nIf you're doing \"analysis\", especially computationally-intensive analysis, load all the data into memory.\nIn the unlikely event that data doesn't fit into memory, then do this.\n\nQuery data into flat files.  This can be fast.  It's fastest if you don't use Python, but use the database native tools to extract data into CSV or something small.\nRead flat files and do computations, writing flat files.  This is really fast.\nDo bulk updates from the flat files.  Again, this is fastest if you use database native toolset for insert or update.\n\n\nIf you didn't need SQL in the first place, consider the data as you originally received it and what you're going to do with it.\n\nRead the original file once, parse it, create your Python objects and pickle the entire list or dictionary.  This means that each subsequent program can simply load the pickled file and start doing analysis.  However.  You can't easily update the pickled file.  You have to create a new one.  This is not a bad thing.  It gives you complete processing history.\nRead the original file once, parse it, create your Python objects using shelve.  This means you can \nupdate the file.  \nRead the original file once, parse it, create your Python objects and save the entire list or dictionary as a JSON or YAML file.  This means that each subsequent program can simply load the JSON (or YAML) file and start doing analysis.  However.  You can't easily update the file.  You have to create a new one.  This is not a bad thing.  It gives you complete processing history. \nThis will probably be slightly slower than pickling.  And it will require that you write some helpers so that the JSON objects are dumped and loaded properly.  However, you can read JSON (and YAML) giving you some advantages in working with the file.","Q_Score":2,"Tags":"python,mysql,optimization","A_Id":3770439,"CreationDate":"2010-09-22T14:43:00.000","Title":"Optimizing Python Code for Database Access","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"We've worked hard to work up a full dimensional database model of our problem, and now it's time to start coding. Our previous projects have used hand-crafted queries constructed by string manipulation.\nIs there any best\/standard practice for interfacing between python and a complex database layout?\nI've briefly evaluated SQLAlchemy, SQLObject, and Django-ORM, but (I may easily be missing something) they seem tuned for tiny web-type (OLTP) transactions, where I'm doing high-volume analytical (OLAP) transactions.\nSome of my requirements, that may be somewhat different than usual:\n\nload large amounts of data relatively quickly\nupdate\/insert small amounts of data quickly and easily\nhandle large numbers of rows easily (300 entries per minute over 5 years)\nallow for modifications in the schema, for future requirements\n\nWriting these queries is easy, but writing the code to get the data all lined up is tedious, especially as the schema evolves. This seems like something that a computer might be good at?","AnswerCount":3,"Available Count":3,"Score":0.1973753202,"is_accepted":false,"ViewCount":3376,"Q_Id":3782386,"Users Score":3,"Answer":"I'm using SQLAlchemy with a pretty big datawarehouse and I'm using it for the full ETL process with success. Specially in certain sources where I have some complex transformation rules or with some heterogeneous sources (such as web services). I'm not using the Sqlalchemy ORM but rather using its SQL Expression Language because I don't really need to map anything with objects in the ETL process. Worth noticing that when I'm bringing a verbatim copy of some of the sources I rather use the db tools for that -such as PostgreSQL dump utility-. You can't beat that.\nSQL Expression Language is the closest you will get with SQLAlchemy (or any ORM for the matter) to handwriting SQL but since you can programatically generate the SQL from python you will save time, specially if you have some really complex transformation rules to follow.\nOne thing though, I rather modify my schema by hand. I don't trust any tool for that job.","Q_Score":10,"Tags":"python,django-models,sqlalchemy,data-warehouse,olap","A_Id":3782627,"CreationDate":"2010-09-23T20:40:00.000","Title":"Python: interact with complex data warehouse","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"We've worked hard to work up a full dimensional database model of our problem, and now it's time to start coding. Our previous projects have used hand-crafted queries constructed by string manipulation.\nIs there any best\/standard practice for interfacing between python and a complex database layout?\nI've briefly evaluated SQLAlchemy, SQLObject, and Django-ORM, but (I may easily be missing something) they seem tuned for tiny web-type (OLTP) transactions, where I'm doing high-volume analytical (OLAP) transactions.\nSome of my requirements, that may be somewhat different than usual:\n\nload large amounts of data relatively quickly\nupdate\/insert small amounts of data quickly and easily\nhandle large numbers of rows easily (300 entries per minute over 5 years)\nallow for modifications in the schema, for future requirements\n\nWriting these queries is easy, but writing the code to get the data all lined up is tedious, especially as the schema evolves. This seems like something that a computer might be good at?","AnswerCount":3,"Available Count":3,"Score":0.1325487884,"is_accepted":false,"ViewCount":3376,"Q_Id":3782386,"Users Score":2,"Answer":"SQLAlchemy definitely. Compared to SQLAlchemy, all other ORMs look like child's toy. Especially the Django-ORM. What's Hibernate to Java, SQLAlchemy is to Python.","Q_Score":10,"Tags":"python,django-models,sqlalchemy,data-warehouse,olap","A_Id":3782432,"CreationDate":"2010-09-23T20:40:00.000","Title":"Python: interact with complex data warehouse","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"We've worked hard to work up a full dimensional database model of our problem, and now it's time to start coding. Our previous projects have used hand-crafted queries constructed by string manipulation.\nIs there any best\/standard practice for interfacing between python and a complex database layout?\nI've briefly evaluated SQLAlchemy, SQLObject, and Django-ORM, but (I may easily be missing something) they seem tuned for tiny web-type (OLTP) transactions, where I'm doing high-volume analytical (OLAP) transactions.\nSome of my requirements, that may be somewhat different than usual:\n\nload large amounts of data relatively quickly\nupdate\/insert small amounts of data quickly and easily\nhandle large numbers of rows easily (300 entries per minute over 5 years)\nallow for modifications in the schema, for future requirements\n\nWriting these queries is easy, but writing the code to get the data all lined up is tedious, especially as the schema evolves. This seems like something that a computer might be good at?","AnswerCount":3,"Available Count":3,"Score":1.0,"is_accepted":false,"ViewCount":3376,"Q_Id":3782386,"Users Score":6,"Answer":"Don't get confused by your requirements.  One size does not fit all.\n\nload large amounts of data relatively quickly\n\nWhy not use the databases's native loaders for this?  Use Python to prepare files, but use database tools to load.  You'll find that this is amazingly fast.  \n\nupdate\/insert small amounts of data quickly and easily\n\nThat starts to bend the rules of a data warehouse.  Unless you're talking about Master Data Management to update reporting attributes of a dimension.\nThat's what ORM's and web frameworks are for.\n\nhandle large numbers of rows easily (300 entries per minute over 5 years)\n\nAgain, that's why you use a pipeline of Python front-end processing, but the actual INSERT's are done by database tools.  Not Python. \n\nalter schema (along with python interface) easily, for future requirements\n\nYou have almost no use for automating this.  It's certainly your lowest priority task for \"programming\".  You'll often do this manually in order to preserve data properly.\nBTW, \"hand-crafted queries constructed by string manipulation\" is probably the biggest mistake ever.  These are hard for the RDBMS parser to handle -- they're slower than using queries that have bind variables inserted.","Q_Score":10,"Tags":"python,django-models,sqlalchemy,data-warehouse,olap","A_Id":3782509,"CreationDate":"2010-09-23T20:40:00.000","Title":"Python: interact with complex data warehouse","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Howdie stackoverflow people!\nSo I've been doing some digging regarding these NoSQL databases, MongoDB, CouchDB etc. Though I am still not sure about real time-ish stuff therefore I thought i'd ask around to see if someone have any practical experience.\nLet's think about web stuff, let's say we've got a very dynamic super ajaxified webapp that asks for various types of data every 5-20 seconds, our backend is python or php or anything other than java really... in cases such as these obviously a MySQL or similar db would be under heavy pressure (with lots of users), would MongoDB \/ CouchDB run this without breaking a sweat and without the need to create some super ultra complex cluster\/caching etc solution?\nYes, that's basically my question, if you think that no.. then yes I know there are several types of solutions for this, nodeJS\/websockets\/antigravity\/worm-hole super tech, but I am just interested in these NoSQL things atm and more specifically if they can handle this type of thing.\nLet's say we have 5000 users at the same time, every 5, 10 or 20 seconds ajax requests that updates various interfaces.\nShoot ;]","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":1738,"Q_Id":3798728,"Users Score":0,"Answer":"It depends heavily on the server running said NoSQL solution, amount of data etc... I have played around with Mongo a bit and it is very easy to setup multiple servers to run simultaneously and you would most likely be able to accomplish high concurrency by starting multiple instances on the same box and having them act like a cluster. Luckily Mongo, at least, handles all the specifics so servers can be killed and introduced without skipping a beat (depending on version). By default I believe the max connections is 1000 so starting 5 servers with said configuration would suffice (if your server can handle it obviously) but realistically you would most likely never be hitting 5000 users at the exact same time.\nI hope for your hardware's sake you would at least come up with a solution that can check to see if new data is available before a full-on fetch. Either via timestamps or Memcache etc...\nOverall I would tend to believe NoSQL would be much faster than traditional databases assuming you are fetching data and not running reports etc... and your datastore design is intelligent enough to compensate for the lack of complex joins.","Q_Score":2,"Tags":"php,python,ajax,mongodb,real-time","A_Id":3799207,"CreationDate":"2010-09-26T16:31:00.000","Title":"MongoDB for realtime ajax stuff?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Howdie stackoverflow people!\nSo I've been doing some digging regarding these NoSQL databases, MongoDB, CouchDB etc. Though I am still not sure about real time-ish stuff therefore I thought i'd ask around to see if someone have any practical experience.\nLet's think about web stuff, let's say we've got a very dynamic super ajaxified webapp that asks for various types of data every 5-20 seconds, our backend is python or php or anything other than java really... in cases such as these obviously a MySQL or similar db would be under heavy pressure (with lots of users), would MongoDB \/ CouchDB run this without breaking a sweat and without the need to create some super ultra complex cluster\/caching etc solution?\nYes, that's basically my question, if you think that no.. then yes I know there are several types of solutions for this, nodeJS\/websockets\/antigravity\/worm-hole super tech, but I am just interested in these NoSQL things atm and more specifically if they can handle this type of thing.\nLet's say we have 5000 users at the same time, every 5, 10 or 20 seconds ajax requests that updates various interfaces.\nShoot ;]","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":1738,"Q_Id":3798728,"Users Score":2,"Answer":"Let's say we have 5000 users at the\n  same time, every 5, 10 or 20 seconds\n  ajax requests that updates various\n  interfaces.\n\nOK, so to get this right, you're talking about 250 to 1000 writes per second? Yeah, MongoDB can handle that.\nThe real key on performance is going to be whether or not these are queries, updates or inserts.\nFor queries, Mongo can probably handle this load. It's really going to be about data size to memory size ratios. If you have a server with 1GB of RAM and 150GB of data, then you're probably not going to get 250 queries \/ second (with any DB technology). But with reasonable hardware specs, Mongo can hit this speed on a single 64-bit server.\nIf you have 5,000 active users and you're constantly updating existing records then Mongo will be really fast (on par with updating memcached on a single machine). The reason here is simply that Mongo will likely keep the record in memory. So a user will send updates every 5 seconds and the in-memory object will be updated.\nIf you are constantly inserting new records, then the limitation is really going to be one of throughput. When you're writing lots of new data, you're also forcing the index to expand. So if you're planning to pump in Gigs of new data, then you risk saturating the disk throughput and you'll need to shard.\nSo based on your questions, it looks like you're mostly querying\/updating. You'll be writing new records, but not 1000 new records \/ second. If this is the case, then MongoDB is probably right for you. It will definitely get around a lot of caching concerns.","Q_Score":2,"Tags":"php,python,ajax,mongodb,real-time","A_Id":3801074,"CreationDate":"2010-09-26T16:31:00.000","Title":"MongoDB for realtime ajax stuff?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I've heard of redis-cache but how exactly does it work? Is it used as a layer between django and my rdbms, by caching the rdbms queries somehow? \nOr is it supposed to be used directly as the database? Which I doubt, since that github page doesn't cover any login details, no setup.. just tells you to set some config property.","AnswerCount":5,"Available Count":1,"Score":1.0,"is_accepted":false,"ViewCount":75541,"Q_Id":3801379,"Users Score":61,"Answer":"Just because Redis stores things in-memory does not mean that it is meant to be a cache. I have seen people using it as a persistent store for data.\nThat it can be used as a cache is a hint that it is useful as a high-performance storage. If your Redis system goes down though you might loose data that was not been written back onto the disk again. There are some ways to mitigate such dangers, e.g. a hot-standby replica.\nIf your data is 'mission-critical', like if you run a bank or a shop, Redis might not be the best pick for you. But if you write a high-traffic game with persistent live data or some social-interaction stuff and manage the probability of data-loss to be quite acceptable, then Redis might be worth a look.\nAnyway, the point remains, yes, Redis can be used as a database.","Q_Score":107,"Tags":"python,django,redis","A_Id":7722260,"CreationDate":"2010-09-27T05:48:00.000","Title":"How can I use redis with Django?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"FTS3\/FTS4 doesn't work in python by default (up to 2.7). I get the error: sqlite3.OperationalError: no such module: fts3\nor\nsqlite3.OperationalError: no such module: fts4\nHow can this be resolved?","AnswerCount":4,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":6571,"Q_Id":3823659,"Users Score":0,"Answer":"What Naveen said but =>\nFor Windows installations:\nWhile running setup.py for for package installations... Python 2.7 searches for an installed Visual Studio 2008. You can trick Python to use Visual Studio by setting\n\nSET VS90COMNTOOLS=%VS100COMNTOOLS%\n\nbefore calling setup.py.","Q_Score":13,"Tags":"python,sqlite,full-text-search,fts3,fts4","A_Id":12372189,"CreationDate":"2010-09-29T16:22:00.000","Title":"How to setup FTS3\/FTS4 with python2.7 on Windows","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"FTS3\/FTS4 doesn't work in python by default (up to 2.7). I get the error: sqlite3.OperationalError: no such module: fts3\nor\nsqlite3.OperationalError: no such module: fts4\nHow can this be resolved?","AnswerCount":4,"Available Count":2,"Score":0.0996679946,"is_accepted":false,"ViewCount":6571,"Q_Id":3823659,"Users Score":2,"Answer":"never mind.\ninstalling pysqlite from source was easy and sufficient.\npython setup.py build_static install fts3 is enabled by default when installing from source.","Q_Score":13,"Tags":"python,sqlite,full-text-search,fts3,fts4","A_Id":3826412,"CreationDate":"2010-09-29T16:22:00.000","Title":"How to setup FTS3\/FTS4 with python2.7 on Windows","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a 100 mega bytes sqlite db file that I would like to load to memory before performing sql queries. Is it possible to do that in python?\nThanks","AnswerCount":4,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":12928,"Q_Id":3826552,"Users Score":2,"Answer":"If you are using Linux, you can try tmpfs which is a memory-based file system.\nIt's very easy to use it:\n\nmount tmpfs to a directory.\ncopy sqlite db file to the directory.\nopen it as normal sqlite db file.\n\nRemember, anything in tmpfs will be lost after reboot. So, you may copy db file back to disk if it changed.","Q_Score":8,"Tags":"python,sql,memory,sqlite","A_Id":25521707,"CreationDate":"2010-09-29T23:10:00.000","Title":"In python, how can I load a sqlite db completely to memory before connecting to it?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have been working on developing this analytical tool to help interpret and analyze a database that is bundled within the package. It is very important for us to secure the database in a way that can only be accessed with our software. What is the best way of achieving it in Python? \nI am aware that there may not be a definitive solution, but deterrence is what really matters here.\nThank you very much.","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":4184,"Q_Id":3848658,"Users Score":3,"Answer":"This question comes up on the SQLite users mailing list about once a month.\nNo matter how much encryption etc you do, if the database is on the client machine then the key to decrypt will also be on the machine at some point.  An attacker will be able to get that key since it is their machine.\nA better way of looking at this is in terms of money - how much would a bad guy need to spend in order to get the data.  This will generally be a few hundred dollars at most.  And all it takes is any one person to get the key and they can then publish the database for everyone.\nSo either go for a web service as mentioned by Donal or just spend a few minutes obfuscating the database.  For example if you use APSW then you can write a VFS in a few lines that XORs the database content so regular SQLite will not open it, nor will a file viewer show the normal SQLite header.  (There is example code in APSW showing how to do this.)\nConsequently anyone who does have the database content had to knowingly do so.","Q_Score":4,"Tags":"python,database,sqlite,encryption","A_Id":3850560,"CreationDate":"2010-10-03T04:55:00.000","Title":"Encrypting a Sqlite db file that will be bundled in a pyexe file","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have an existing sqlite3 db file, on which I need to make some extensive calculations. Doing the calculations from the file is painfully slow, and as the file is not large (~10 MB), so there should be no problem to load it into memory.\nIs there a Pythonic way to load the existing file into memory in order to speed up the calculations?","AnswerCount":10,"Available Count":2,"Score":-0.0199973338,"is_accepted":false,"ViewCount":46619,"Q_Id":3850022,"Users Score":-1,"Answer":"sqlite supports in-memory databases.\nIn python, you would use a :memory: database name for that.\nPerhaps you could open two databases (one from the file, an empty one in-memory), migrate everything from the file database into memory, then use the in-memory database further to do calculations.","Q_Score":72,"Tags":"python,performance,sqlite","A_Id":3850164,"CreationDate":"2010-10-03T13:55:00.000","Title":"How to load existing db file to memory in Python sqlite3?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have an existing sqlite3 db file, on which I need to make some extensive calculations. Doing the calculations from the file is painfully slow, and as the file is not large (~10 MB), so there should be no problem to load it into memory.\nIs there a Pythonic way to load the existing file into memory in order to speed up the calculations?","AnswerCount":10,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":46619,"Q_Id":3850022,"Users Score":0,"Answer":"With the solution of Cenk Alti, I always had a MemoryError with Python 3.7, when the process reached 500MB. Only with the use of the backup functionality of sqlite3 (mentioned by thinwybk), I was able to to load and save bigger SQLite databases. Also you can do the same with just 3 lines of code, both ways.","Q_Score":72,"Tags":"python,performance,sqlite","A_Id":57569063,"CreationDate":"2010-10-03T13:55:00.000","Title":"How to load existing db file to memory in Python sqlite3?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Looking around for a noSQL database implementation that has an ORM syntax (pref. like Django's), lets me store and retrieve nested dictionary attributes but written entirely in Python to ease deployment and avoids Javascript syntax for map\/reduce. Even better if it has a context-aware (menus), python-based console, as well as being able to run as a separate daemon task. Is there such an initiative already (I can't find it) or should I start one?","AnswerCount":4,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":1830,"Q_Id":3865283,"Users Score":2,"Answer":"I don't know about a noSQL solution, but sqlite+sqlalchemy's ORM works pretty well for me. As long as it gives you the interface and features you need, I don't see a reason to care whether it uses sql internally.","Q_Score":4,"Tags":"python,mongodb,nosql","A_Id":3865523,"CreationDate":"2010-10-05T15:39:00.000","Title":"Pure Python implementation of MongoDB?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm using Python and SQLAlchemy to query a SQLite FTS3 (full-text) store and I would like to prevent my users from using the - as an operator. How should I escape the - so users can search for a term containing the - (enabled by changing the default tokenizer) instead of it signifying \"does not contain the term following the -\"?","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":1200,"Q_Id":3865733,"Users Score":1,"Answer":"From elsewhere on the internet it seems it may be possible to surround each search term with double quotes \"some-term\". Since we do not need the subtraction operation, my solution was to replace hyphens - with underscores _ when populating the search index and when performing searches.","Q_Score":2,"Tags":"python,sqlite,sqlalchemy,fts3","A_Id":3942449,"CreationDate":"2010-10-05T16:32:00.000","Title":"How do I escape the - character in SQLite FTS3 queries?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm trying to restore the current working database to the data stored in a .sql file from within Django. Whats the best way to do this? Does django have an good way to do this or do I need to grab the connection string from the settings.py file and send command line mysql commands to do this?\nThanks for your help.","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":182,"Q_Id":3866989,"Users Score":1,"Answer":"You can't import sql dumps through django; import it through mysql directly, if you run mysql locally you can find various graphical mysql clients that can help you with doing so; if you need to do it remotely, find out if your server has any web interfaces for that installed!","Q_Score":0,"Tags":"python,mysql,django","A_Id":3868544,"CreationDate":"2010-10-05T19:28:00.000","Title":"How do I replace the current working MySQL database with a .sql file?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"i just want to use an entity modify it to show something,but don't want to change to the db,\nbut after i use it ,and in some other place do the session.commit()\nit will add this entity to db,i don't want this happen,\nany one could help me?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":85,"Q_Id":3881364,"Users Score":1,"Answer":"You can expunge it from session before modifying object, then this changes won't be accounted on next commits unless you add the object back to session. Just call session.expunge(obj).","Q_Score":0,"Tags":"python,sqlalchemy,entity","A_Id":3896280,"CreationDate":"2010-10-07T11:56:00.000","Title":"use sqlalchemy entity isolately","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am trying out Sphinx search in my Django project. All setup done & it works but need some clarification from someone who has actually used this setup.\nIn my Sphinx search while indexing, I have used 'name' as the field in my MySQL to be searchable & all other fields in sql_query to be as attributes (according to Sphinx lingo). \nSo when I search from my Model instance in Django, I get the search results alright but it does not have the 'name' field in the search results. I get all the other attributes. \nHowever, I get the 'id' of the search term. Technically, I could get the 'name' by again querying MySQL but I want to avoid this. Is there anything I am not doing here?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":395,"Q_Id":3897650,"Users Score":1,"Answer":"Here's a shot in the dark - \nTry to get the name of your index in sphinx.conf same as the table_name you are trying to index. This is a quirk which is missed by lot of people.","Q_Score":0,"Tags":"python,django,search,full-text-search,django-sphinx","A_Id":4121651,"CreationDate":"2010-10-09T20:02:00.000","Title":"Django Sphinx Text Search","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm currently busy making a Python ORM which gets all of its information from a RDBMS via introspection (I would go with XRecord if I was happy with it in other respects) \u2014 meaning, the end-user only tells which tables\/views to look at, and the ORM does everything else automatically (if it makes you actually write something and you're not looking for weird things and dangerous adventures, it's a bug).\nThe major part of that is detecting relationships, provided that the database has all relevant constraints in place and you have no naming conventions at all \u2014\u00a0I want to be able to have this ORM work with a database made by any crazy DBA which has his own views on what the columns and tables should be named like. And I'm stuck at many-to-many relationships.\nFirst, there can be compound keys. Then, there can be MTM relationships with three or more tables. Then, a MTM intermediary table might have its own data apart from keys \u2014\u00a0some data common to all tables it ties together.\nWhat I want is a method to programmatically detect that a table X is an intermediary table tying tables A and B, and that any non-key data it has must belong to both A and B (and if I change a common attribute from within A, it should affect the same attribute in B). Are there common algorithms to do that? Or at least to make guesses which are right in 80% of the cases (provided the DBA is sane)?","AnswerCount":3,"Available Count":3,"Score":1.2,"is_accepted":true,"ViewCount":241,"Q_Id":3901961,"Users Score":0,"Answer":"So far, I see the only one technique covering more than two tables in relation. A table X is assumed related to table Y, if and only if X is referenced to Y no more than one table away. That is:\n\"Zero tables away\" means X contains the foreign key to Y. No big deal, that's how we detect many-to-ones.\n\"One table away\" means there is a table Z which itself has a foreign key referencing table X (these are easy to find), and a foreign key referencing table Y.\nThis reduces the scope of traits to look for a lot (we don't have to care if the intermediary table has any other attributes), and it covers any number of tables tied together in a MTM relation.\nIf there are some interesting links or other methods, I'm willing to hear them.","Q_Score":2,"Tags":"python,orm,metaprogramming,introspection,relationships","A_Id":3902410,"CreationDate":"2010-10-10T19:59:00.000","Title":"What are methods of programmatically detecting many-to-many relationships in a RDMBS?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm currently busy making a Python ORM which gets all of its information from a RDBMS via introspection (I would go with XRecord if I was happy with it in other respects) \u2014 meaning, the end-user only tells which tables\/views to look at, and the ORM does everything else automatically (if it makes you actually write something and you're not looking for weird things and dangerous adventures, it's a bug).\nThe major part of that is detecting relationships, provided that the database has all relevant constraints in place and you have no naming conventions at all \u2014\u00a0I want to be able to have this ORM work with a database made by any crazy DBA which has his own views on what the columns and tables should be named like. And I'm stuck at many-to-many relationships.\nFirst, there can be compound keys. Then, there can be MTM relationships with three or more tables. Then, a MTM intermediary table might have its own data apart from keys \u2014\u00a0some data common to all tables it ties together.\nWhat I want is a method to programmatically detect that a table X is an intermediary table tying tables A and B, and that any non-key data it has must belong to both A and B (and if I change a common attribute from within A, it should affect the same attribute in B). Are there common algorithms to do that? Or at least to make guesses which are right in 80% of the cases (provided the DBA is sane)?","AnswerCount":3,"Available Count":3,"Score":0.0665680765,"is_accepted":false,"ViewCount":241,"Q_Id":3901961,"Users Score":1,"Answer":"If you have to ask, you shouldn't be doing this. I'm not saying that to be cruel, but Python already has several excellent ORMs that are well-tested and widely used. For example, SQLAlchemy supports the autoload=True attribute when defining tables that makes it read the table definition - including all the stuff you're asking about - directly from the database. Why re-invent the wheel when someone else has already done 99.9% of the work?\nMy answer is to pick a Python ORM (such as SQLAlchemy) and add any \"missing\" functionality to that instead of starting from scratch. If it turns out to be a good idea, release your changes back to the main project so that everyone else can benefit from them. If it doesn't work out like you hoped, at least you'll already be using a common ORM that many other programmers can help you with.","Q_Score":2,"Tags":"python,orm,metaprogramming,introspection,relationships","A_Id":3902041,"CreationDate":"2010-10-10T19:59:00.000","Title":"What are methods of programmatically detecting many-to-many relationships in a RDMBS?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm currently busy making a Python ORM which gets all of its information from a RDBMS via introspection (I would go with XRecord if I was happy with it in other respects) \u2014 meaning, the end-user only tells which tables\/views to look at, and the ORM does everything else automatically (if it makes you actually write something and you're not looking for weird things and dangerous adventures, it's a bug).\nThe major part of that is detecting relationships, provided that the database has all relevant constraints in place and you have no naming conventions at all \u2014\u00a0I want to be able to have this ORM work with a database made by any crazy DBA which has his own views on what the columns and tables should be named like. And I'm stuck at many-to-many relationships.\nFirst, there can be compound keys. Then, there can be MTM relationships with three or more tables. Then, a MTM intermediary table might have its own data apart from keys \u2014\u00a0some data common to all tables it ties together.\nWhat I want is a method to programmatically detect that a table X is an intermediary table tying tables A and B, and that any non-key data it has must belong to both A and B (and if I change a common attribute from within A, it should affect the same attribute in B). Are there common algorithms to do that? Or at least to make guesses which are right in 80% of the cases (provided the DBA is sane)?","AnswerCount":3,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":241,"Q_Id":3901961,"Users Score":0,"Answer":"Theoretically, any table with multiple foreign keys is in essence a many-to-many relation, which makes your question trivial. I suspect that what you need is a heuristic of when to use MTM patterns (rather than standard classes) in the object model. In that case, examine what are the limitations of the patterns you chose.\nFor example, you can model a simple MTM relationship (two tables, no attributes) by having lists as attributes on both types of objects. However, lists will not be enough if you have additional data on the relationship itself. So only invoke this pattern for tables with two columns, both with foreign keys.","Q_Score":2,"Tags":"python,orm,metaprogramming,introspection,relationships","A_Id":3902030,"CreationDate":"2010-10-10T19:59:00.000","Title":"What are methods of programmatically detecting many-to-many relationships in a RDMBS?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Well, the question pretty much summarises it. My db activity is very update intensive, and I want to programmatically issue a Vacuum Analyze. However I get an error that says that the query cannot be executed within a transaction. Is there some other way to do it?","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":5030,"Q_Id":3931951,"Users Score":14,"Answer":"This is a flaw in the Python DB-API: it starts a transaction for you.  It shouldn't do that; whether and when to start a transaction should be up to the programmer.  Low-level, core APIs like this shouldn't babysit the developer and do things like starting transactions behind our backs.  We're big boys--we can start transactions ourself, thanks.\nWith psycopg2, you can disable this unfortunate behavior with an API extension: run connection.autocommit = True.  There's no standard API for this, unfortunately, so you have to depend on nonstandard extensions to issue commands that must be executed outside of a transaction.\nNo language is without its warts, and this is one of Python's.  I've been bitten by this before too.","Q_Score":9,"Tags":"python,postgresql,sqlalchemy,psycopg2,vacuum","A_Id":3932055,"CreationDate":"2010-10-14T09:49:00.000","Title":"Is it possible to issue a \"VACUUM ANALYZE \" from psycopg2 or sqlalchemy for PostgreSQL?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Hi so this is what I understand how Openid works:-\n\nthe user enters his openid url on the site say\"hii.com\"\nThe app does a redirect to the openid provider and either does the login or denies it and sends the response back to the site i.e\"hii.com\"\nIf authentication was succesful then the response object provided by the openid provider can contain other data too like email etc if \"hii.com\" had requested for it.\nI can save this data in the database.\n\nPlease correct me if I am wrong. However what I am not understanding here is the concept of stores. I see openid.store.filestore,nonce,sqlstore. Could someone please provide some clarity on it. What role does this store play here.\nI have gone through python openid docs but end up feeling clueless.\nThanks","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":488,"Q_Id":3937456,"Users Score":1,"Answer":"upd.: my previous answer was wrong\nThe store you are referring to is where your app stores the data during auth.\nStoring it in a shared memcached instance should be the best option (faster than db and reliable enough).","Q_Score":3,"Tags":"python,openid,store","A_Id":3937506,"CreationDate":"2010-10-14T20:51:00.000","Title":"what is the concept of store in OpenID","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"... vs declarative sqlalchemy ?","AnswerCount":3,"Available Count":1,"Score":0.0665680765,"is_accepted":false,"ViewCount":4024,"Q_Id":3957938,"Users Score":1,"Answer":"The Elixir syntax is something I find useful when building a database for a given app from scratch and everything is all figured out beforehand.\nI have had my best luck with SQLAlchemy when using it on legacy databases (and on other similarly logistically immutable schemas). Particularly useful is the plugin SQLSoup, for read-only one-time extractions of data in preparation for migrating it elsewhere.\nYMMV but Elixir isn't really designed to adapt to older schemas -- and SQLAlchemy proper is overkill for most small- to mid-size projects (in my opinion of course).","Q_Score":7,"Tags":"python,sqlalchemy,python-elixir","A_Id":3975114,"CreationDate":"2010-10-18T09:36:00.000","Title":"What are the benefits of using Elixir","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I will be writing a little Python script tomorrow, to retrieve all the data from an old MS Access database into a CSV file first, and then after some data cleansing, munging etc, I will import the data into a mySQL database on Linux.\nI intend to use pyodbc to make a connection to the MS Access db. I will be running the initial script in a Windows environment.\nThe db has IIRC well over half a million rows of data. My questions are:\n\nIs the number of records a cause for concern? (i.e. Will I hit some limits)?\nIs there a better file format for the transitory data (instead of CSV)?\n\nI chose CSv because it is quite simple and straightforward (and I am a Python newbie) - but \nI would like to hear from someone who may have done something similar before.","AnswerCount":4,"Available Count":3,"Score":1.2,"is_accepted":true,"ViewCount":8978,"Q_Id":3964378,"Users Score":5,"Answer":"Memory usage for csvfile.reader and csvfile.writer isn't proportional to the number of records, as long as you iterate correctly and don't try to load the whole file into memory.  That's one reason the iterator protocol exists.  Similarly, csvfile.writer writes directly to disk; it's not limited by available memory.  You can process any number of records with these without memory limitations.\nFor simple data structures, CSV is fine.  It's much easier to get fast, incremental access to CSV than more complicated formats like XML (tip: pulldom is painfully slow).","Q_Score":1,"Tags":"python,ms-access,csv,odbc","A_Id":3964635,"CreationDate":"2010-10-18T23:49:00.000","Title":"is there a limit to the (CSV) filesize that a Python script can read\/write?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I will be writing a little Python script tomorrow, to retrieve all the data from an old MS Access database into a CSV file first, and then after some data cleansing, munging etc, I will import the data into a mySQL database on Linux.\nI intend to use pyodbc to make a connection to the MS Access db. I will be running the initial script in a Windows environment.\nThe db has IIRC well over half a million rows of data. My questions are:\n\nIs the number of records a cause for concern? (i.e. Will I hit some limits)?\nIs there a better file format for the transitory data (instead of CSV)?\n\nI chose CSv because it is quite simple and straightforward (and I am a Python newbie) - but \nI would like to hear from someone who may have done something similar before.","AnswerCount":4,"Available Count":3,"Score":0.049958375,"is_accepted":false,"ViewCount":8978,"Q_Id":3964378,"Users Score":1,"Answer":"I wouldn't bother using an intermediate format. Pulling from Access via ADO and inserting right into MySQL really shouldn't be an issue.","Q_Score":1,"Tags":"python,ms-access,csv,odbc","A_Id":3964404,"CreationDate":"2010-10-18T23:49:00.000","Title":"is there a limit to the (CSV) filesize that a Python script can read\/write?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I will be writing a little Python script tomorrow, to retrieve all the data from an old MS Access database into a CSV file first, and then after some data cleansing, munging etc, I will import the data into a mySQL database on Linux.\nI intend to use pyodbc to make a connection to the MS Access db. I will be running the initial script in a Windows environment.\nThe db has IIRC well over half a million rows of data. My questions are:\n\nIs the number of records a cause for concern? (i.e. Will I hit some limits)?\nIs there a better file format for the transitory data (instead of CSV)?\n\nI chose CSv because it is quite simple and straightforward (and I am a Python newbie) - but \nI would like to hear from someone who may have done something similar before.","AnswerCount":4,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":8978,"Q_Id":3964378,"Users Score":0,"Answer":"The only limit should be operating system file size.\nThat said, make sure when you send the data to the new database, you're writing it a few records at a time; I've seen people do things where they try to load the entire file first, then write it.","Q_Score":1,"Tags":"python,ms-access,csv,odbc","A_Id":3964398,"CreationDate":"2010-10-18T23:49:00.000","Title":"is there a limit to the (CSV) filesize that a Python script can read\/write?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"As the title says, what is the equivalent of Python's '%s %s' % (first_string, second_string) in SQLite? I know I can do concatenation like first_string || \" \" || second_string, but it looks very ugly.","AnswerCount":5,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":2632,"Q_Id":3976313,"Users Score":0,"Answer":"There isn't one.","Q_Score":0,"Tags":"python,sqlite,string","A_Id":3976347,"CreationDate":"2010-10-20T09:16:00.000","Title":"SQLite equivalent of Python's \"'%s %s' % (first_string, second_string)\"","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"As the title says, what is the equivalent of Python's '%s %s' % (first_string, second_string) in SQLite? I know I can do concatenation like first_string || \" \" || second_string, but it looks very ugly.","AnswerCount":5,"Available Count":2,"Score":0.0798297691,"is_accepted":false,"ViewCount":2632,"Q_Id":3976313,"Users Score":2,"Answer":"I can understand not liking first_string || ' ' || second_string, but that's the equivalent. Standard SQL (which SQLite speaks in this area) just isn't the world's prettiest string manipulation language. You could try getting the results of the query back into some other language (e.g., Python which you appear to like) and doing the concatenation there; it's usually best to not do \"presentation\" in the database layer (and definitely not a good idea to use the result of concatenation as something to search against; that makes it impossible to optimize with indices!)","Q_Score":0,"Tags":"python,sqlite,string","A_Id":3976353,"CreationDate":"2010-10-20T09:16:00.000","Title":"SQLite equivalent of Python's \"'%s %s' % (first_string, second_string)\"","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I've been asked to encrypt various db fields within the db.\nProblem is that these fields need be decrypted after being read.\n\nI'm using Django and SQL Server 2005.\nAny good ideas?","AnswerCount":4,"Available Count":2,"Score":0.0996679946,"is_accepted":false,"ViewCount":13590,"Q_Id":3979385,"Users Score":2,"Answer":"If you are storing things like passwords, you can do this:\n\nstore users' passwords as their SHA256 hashes\nget the user's password\nhash it\nList item\n\ncheck it against the stored password\nYou can create a SHA-256 hash in Python by using the hashlib module.\nHope this helps","Q_Score":17,"Tags":"python,sql,sql-server,django,encryption","A_Id":3979447,"CreationDate":"2010-10-20T15:12:00.000","Title":"A good way to encrypt database fields?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I've been asked to encrypt various db fields within the db.\nProblem is that these fields need be decrypted after being read.\n\nI'm using Django and SQL Server 2005.\nAny good ideas?","AnswerCount":4,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":13590,"Q_Id":3979385,"Users Score":6,"Answer":"Yeah. Tell whoever told you to get real. Makes no \/ little sense. If it is about the stored values - enterprise edition 2008 can store encrypted DB files.\nOtherwise, if you really need to (with all disadvantages) just encrypt them and store them as byte fields.","Q_Score":17,"Tags":"python,sql,sql-server,django,encryption","A_Id":3979446,"CreationDate":"2010-10-20T15:12:00.000","Title":"A good way to encrypt database fields?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'd like to build a \"feed\" for recent activity related to a specific section of my site.  I haven't used memcache before, but I'm thinking of something like this:\n\nWhen a new piece of information is submitted to the site, assign a unique key to it and also add it to memcache.\nAdd this key to the end of an existing list in memcache, so it can later be referenced.\nWhen retrieving, first retrieve the list of keys from memcache\nFor each key retrieved, retrieve the individual piece of information\nString the pieces together and return them as the \"feed\"\n\nE.g., user comments: user writes, \"Nice idea\"\n\nAssign a unique key to \"Nice idea,\" let's say key \"1234\"\nInsert a key\/data pair into memcache, 1234 -> \"Nice Idea\"\nAppend \"1234\" to an existing list of keys: key_list -> {2341,41234,124,341,1234}\nNow when retrieving, first query the key list: {2341,41234,124,341,1234}\nFor each key in the key list, retrieve the data:\n2341 -> \"Yes\"\n41234 -> \"Good point\"\n124 -> \"That's funny\"\n341 -> \"I don't agree\"\n1234 -> \"Nice Idea\"\n\nIs this a good approach?\nThanks!","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":351,"Q_Id":3999496,"Users Score":0,"Answer":"If the list of keys is bounded in size then it should be ok.  memcache by default has a 1MB item size limit.\nSounds like memcache is the only storage for the data, is it a good idea?","Q_Score":0,"Tags":"python,memcached,feed","A_Id":4006612,"CreationDate":"2010-10-22T17:43:00.000","Title":"Best way to keep an activity log in memcached","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am trying to implement a python script which writes and reads to a database to track changes within a 3d game (Minecraft) These changes are done by various clients and can be represented by player name, coordinates (x,y,z), and a description. I am storing a high volume of changes and would like to know what would be an easy and preferably fast way to store and retrieve these changes. What kinds of databases that would be suited to this job?","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":144,"Q_Id":4000072,"Users Score":0,"Answer":"Any kind.  A NoSQL option like MongoDB might be especially interesting.","Q_Score":0,"Tags":"python,database,change-tracking","A_Id":4000101,"CreationDate":"2010-10-22T19:02:00.000","Title":"Suitable kind of database to track a high volume of changes","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have some things that do not need to be indexed or searched (game configurations) so I was thinking of storing JSON on a BLOB. Is this a good idea at all? Or are there alternatives?","AnswerCount":4,"Available Count":4,"Score":0.0996679946,"is_accepted":false,"ViewCount":1335,"Q_Id":4001314,"Users Score":2,"Answer":"I don't see why not. As a related real-world example, WordPress stores serialized PHP arrays as a single value in many instances.","Q_Score":1,"Tags":"python,mysql,json","A_Id":4001358,"CreationDate":"2010-10-22T22:05:00.000","Title":"Storing JSON in MySQL?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have some things that do not need to be indexed or searched (game configurations) so I was thinking of storing JSON on a BLOB. Is this a good idea at all? Or are there alternatives?","AnswerCount":4,"Available Count":4,"Score":0.0,"is_accepted":false,"ViewCount":1335,"Q_Id":4001314,"Users Score":0,"Answer":"I think,It's beter serialize your XML.If you are using python language ,cPickle is good choice.","Q_Score":1,"Tags":"python,mysql,json","A_Id":4008102,"CreationDate":"2010-10-22T22:05:00.000","Title":"Storing JSON in MySQL?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have some things that do not need to be indexed or searched (game configurations) so I was thinking of storing JSON on a BLOB. Is this a good idea at all? Or are there alternatives?","AnswerCount":4,"Available Count":4,"Score":1.2,"is_accepted":true,"ViewCount":1335,"Q_Id":4001314,"Users Score":5,"Answer":"If you need to query based on the values within the JSON, it would be better to store the values separately.\nIf you are just loading a set of configurations like you say you are doing, storing the JSON directly in the database works great and is a very easy solution.","Q_Score":1,"Tags":"python,mysql,json","A_Id":4001338,"CreationDate":"2010-10-22T22:05:00.000","Title":"Storing JSON in MySQL?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have some things that do not need to be indexed or searched (game configurations) so I was thinking of storing JSON on a BLOB. Is this a good idea at all? Or are there alternatives?","AnswerCount":4,"Available Count":4,"Score":0.0996679946,"is_accepted":false,"ViewCount":1335,"Q_Id":4001314,"Users Score":2,"Answer":"No different than people storing XML snippets in a database (that doesn't have XML support). Don't see any harm in it, if it really doesn't need to be searched at the DB level. And the great thing about JSON is how parseable it is.","Q_Score":1,"Tags":"python,mysql,json","A_Id":4001334,"CreationDate":"2010-10-22T22:05:00.000","Title":"Storing JSON in MySQL?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"A new requirement has come down from the top: implement 'proprietary business tech' with the awesome, resilient Elixir database I have set up. I've tried a lot of different things, such as creating an implib from the provided interop DLL (which apparently doesn't work like COM dlls) which didn't work at all. CPython doesn't like the MFC stuff either, so all attempts to create a Python lib have failed (using C anyway, not sure you can create a python library from .NET directly).\nThe only saving grace is the developer saw fit to provide VBA, .NET and MFC Interop C++ hooks into his library, so there are \"some\" choices, though they all ultimately lead back to the same framework. What would be the best method to: \nA) Keep my model definitions in one place, in one language (Python\/Elixir\/SQLAlchemy)\nB) Have this new .NET access the models without resorting to brittle, hard-coded SQL.\nAny and all suggestions are welcome.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":502,"Q_Id":4017164,"Users Score":0,"Answer":"After a day or so of deliberation, I'm attempting to load the new business module in IronPython. Although I don't really want to introduce to python interpreters into my environment, I think that this will be the glue I need to get this done efficiently.","Q_Score":0,"Tags":"sqlalchemy,python-elixir","A_Id":4025154,"CreationDate":"2010-10-25T17:23:00.000","Title":"Loading Elixir\/SQLAlchemy models in .NET?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Django: If I added new tables to database, how can I query them?\nDo I need to create the relevant models first? Or django creates it by itself?\nMore specifically,  I installed another django app, it created several database tables in database, and now I want to get some specific data from them? What are the correct approaches? Thank you very much!","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":78,"Q_Id":4042286,"Users Score":0,"Answer":"Django doen't  follow convention over configuration philosophy. you have to explicitly create the backing model for the table and in the meta tell it about the table name...","Q_Score":0,"Tags":"python,django,django-models,django-admin","A_Id":4042305,"CreationDate":"2010-10-28T11:11:00.000","Title":"Django: If I added new tables to database, how can I query them?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Django: If I added new tables to database, how can I query them?\nDo I need to create the relevant models first? Or django creates it by itself?\nMore specifically,  I installed another django app, it created several database tables in database, and now I want to get some specific data from them? What are the correct approaches? Thank you very much!","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":78,"Q_Id":4042286,"Users Score":1,"Answer":"I suppose another django app has all model files needed to access those tables, you should just try importing those packages and use this app's models.","Q_Score":0,"Tags":"python,django,django-models,django-admin","A_Id":4042337,"CreationDate":"2010-10-28T11:11:00.000","Title":"Django: If I added new tables to database, how can I query them?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm having a problem with file uploading. I'm using FastCGI on Apache2 (unix) to run a WSGI-compliant application. File uploads, in the form of images, are begin saved in a MySQL database. However, larger images are being truncated at 65535 bytes. As far as I can tell, nothing should be limiting the size of the files and I'm not sure which one of the pieces in my solution would be causing the problem.\nIs it FastCGI; can it limit file upload sizes?\nIs it Python? The cgi.FieldStorage object gives me a file handle to the uploaded file which I then read: file.read(). Does this limit file sizes in any way?\nIs it MySQL? The type of the column for saving the image data is a longblob. I figured this could store a couple of GB worth of data. So a few MB shouldn't be a problem, right?\nIs it the flups WSGIServer? I can't find any information regarding this.\nMy file system can definitely handle huge files, so that's not a problem. Any ideas?\nUPDATE:\nIt is MySQL. I got python to output the number of bytes uploaded and it's greater than 65535. So I looked into max_allowed_packet for mysqld and set it to 128M. Overkill, but wanting to be sure for the moment. \nMy only problem now is getting python's MySQLdb to allow the transfer of more than 65535 bytes. Does anyone know how to do this? Might post as a separate question.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1279,"Q_Id":4047899,"Users Score":2,"Answer":"If the web server\/gateway layer were truncating incoming form submissions I'd expect an error from FieldStorage, since the truncation would not just interrupt the file upload but also the whole multipart\/form-data structure. Even if cgi.py tolerated this, it would be very unlikely to have truncated the multipart at just the right place to leave exactly 2**16-1 bytes of file upload.\nSo I would suspect MySQL. LONGBLOB should be fine up to 2**32-1, but 65535 would be the maximum length of a normal BLOB. Are you sure the types are what you think? Check with SHOW CREATE TABLE x. Which database layer are you using to get the data in?","Q_Score":3,"Tags":"python,mysql,file-upload,apache2,fastcgi","A_Id":4047955,"CreationDate":"2010-10-28T23:16:00.000","Title":"Does FastCGI or Apache2 limit upload sizes?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"It seems as if MySQLdb is restricting the maximum transfer size for SQL statements. I have set the max_allowed_packet to 128M for mysqld. MySQL documentation says that this needs to be done for the client as well.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1923,"Q_Id":4050257,"Users Score":1,"Answer":"You need to put max_allowed_packet into the [client] section of my.cnf on the machine where the client runs. If you want to, you can specify a different file or group in mysqldb.connect.","Q_Score":3,"Tags":"python,mysql","A_Id":4051531,"CreationDate":"2010-10-29T08:36:00.000","Title":"How do I set max_allowed_packet or equivalent for MySQLdb in python?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"When connected to a postgresql database using psycopg and I pull the network cable I get no errors.   How can I detect this in code to notify the user?","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":214,"Q_Id":4061635,"Users Score":0,"Answer":"You will definitely get an error the next time you try and execute a query, so I wouldn't worry if you can't alert the user at the exact instance they lose there network connection.","Q_Score":2,"Tags":"python,postgresql,psycopg","A_Id":4061641,"CreationDate":"2010-10-31T02:54:00.000","Title":"Python and psycopg detect network error","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"When connected to a postgresql database using psycopg and I pull the network cable I get no errors.   How can I detect this in code to notify the user?","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":214,"Q_Id":4061635,"Users Score":0,"Answer":"psycopg can't detect what happens with the network. For example, if you unplug your ethernet cable, replug it and execute a query everything will work OK. You should definitely get an exception when psycopg tries to send some SQL to the backend and there is no network connection but depending on the exact netwokr problem it can take some time. In the worst case you'll have to wait for a TCP timeout on the connection (several tens of seconds).","Q_Score":2,"Tags":"python,postgresql,psycopg","A_Id":4069833,"CreationDate":"2010-10-31T02:54:00.000","Title":"Python and psycopg detect network error","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am using Redis database where we store the navigational information. These data must be persistent and should be fetched faster. I don't have more than 200 MB data in this data set.\nI face problem when writing admin modules for redis db and I really missing the sql schema and power of django style admin modules.\nNow I am thinking of using MySQL. The requirement is, I want the persistent database but the data can be loaded into the memory like redis so that I can do the SQL queries REALLY faster.\nIs it possible to use MySQL in persistent mode and instruct MySQL to use the memory for querying purpose? What is the best suitable MySQL DB where I do not worry much on consistencies where our writes are very few.","AnswerCount":3,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":1165,"Q_Id":4061828,"Users Score":1,"Answer":"I would create a read only slave to your mysql database and force its database engines to memory.  You'd have to handle failures by re-initializing the read only database, but that can be scripted rather easily.\nThis way you still have your persistence in the regular mysql database and your read speed in the read only memory tables.","Q_Score":1,"Tags":"python,mysql,sqlalchemy,performance","A_Id":4061902,"CreationDate":"2010-10-31T04:18:00.000","Title":"fit mysql db in memory","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am using Redis database where we store the navigational information. These data must be persistent and should be fetched faster. I don't have more than 200 MB data in this data set.\nI face problem when writing admin modules for redis db and I really missing the sql schema and power of django style admin modules.\nNow I am thinking of using MySQL. The requirement is, I want the persistent database but the data can be loaded into the memory like redis so that I can do the SQL queries REALLY faster.\nIs it possible to use MySQL in persistent mode and instruct MySQL to use the memory for querying purpose? What is the best suitable MySQL DB where I do not worry much on consistencies where our writes are very few.","AnswerCount":3,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":1165,"Q_Id":4061828,"Users Score":0,"Answer":"I would think you could have a persistent table, copy all of the data into a MEMORY engine table whenever the server starts, and have triggers on the memory db for INSERT UPDATE and DELETE write to the persistent table so it is hidden for the user.  Correct me if I'm wrong though, it's just the approach I would first try.","Q_Score":1,"Tags":"python,mysql,sqlalchemy,performance","A_Id":4061848,"CreationDate":"2010-10-31T04:18:00.000","Title":"fit mysql db in memory","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a csv file which contains rows from a sqlite3 database. I wrote the rows to the csv file using python.\nWhen I open the csv file with Ms Excel, a blank row appears below every row, but the file on notepad is fine(without any blanks).\nDoes anyone know why this is happenning and how I can fix it?\nEdit: I used the strip() function for all the attributes before writing a row.\nThanks.","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":7209,"Q_Id":4122794,"Users Score":34,"Answer":"You're using open('file.csv', 'w')--try open('file.csv', 'wb'). \nThe Python csv module requires output files be opened in binary mode.","Q_Score":15,"Tags":"python,excel,csv","A_Id":4122980,"CreationDate":"2010-11-08T10:00:00.000","Title":"Csv blank rows problem with Excel","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a csv file which contains rows from a sqlite3 database. I wrote the rows to the csv file using python.\nWhen I open the csv file with Ms Excel, a blank row appears below every row, but the file on notepad is fine(without any blanks).\nDoes anyone know why this is happenning and how I can fix it?\nEdit: I used the strip() function for all the attributes before writing a row.\nThanks.","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":7209,"Q_Id":4122794,"Users Score":0,"Answer":"the first that comes into my mind (just an idea) is that you might have used \"\\r\\n\" as row delimiter (which is shown as one linebrak in notepad) but excel expects to get only \"\\n\" or only \"\\r\" and so it interprets this as two line-breaks.","Q_Score":15,"Tags":"python,excel,csv","A_Id":4122816,"CreationDate":"2010-11-08T10:00:00.000","Title":"Csv blank rows problem with Excel","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a simple question. I'm doing some light crawling so new content arrives every few days. I've written a tokenizer and would like to use it for some text mining purposes. Specifically, I'm using Mallet's topic modeling tool and one of the pipe is to tokenize the text into tokens before further processing can be done. With the amount of text in my database, it takes a substantial amount of time tokenizing the text (I'm using regex here). \nAs such, is it a norm to store the tokenized text in the db so that tokenized data can be readily available and tokenizing can be skipped if I need them for other text mining purposes such as Topic modeling, POS tagging? What are the cons of this approach?","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":894,"Q_Id":4122940,"Users Score":1,"Answer":"I store tokenized text in a MySQL database. While I don't always like the overhead of communication with the database, I've found that there are lots of processing tasks that I can ask the database to do for me (like search the dependency parse tree for complex syntactic patterns).","Q_Score":2,"Tags":"python,caching,postgresql,nlp,tokenize","A_Id":4151273,"CreationDate":"2010-11-08T10:17:00.000","Title":"Storing tokenized text in the db?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I noticed that a significant part of my (pure Python) code deals with tables. Of course, I have class Table which supports the basic functionality, but I end up adding more and more features to it, such as queries, validation, sorting, indexing, etc.\nI to wonder if it's a good idea to remove my class Table, and refactor the code to use a regular relational database that I will instantiate  in-memory.\nHere's my thinking so far:\n\nPerformance of queries and indexing would improve but communication between Python code and the separate database process might be less efficient than between Python functions. I assume that is too much overhead, so I would have to go with sqlite which comes with Python and lives in the same process. I hope this means it's a pure performance gain (at the cost of non-standard SQL definition and limited features of sqlite).\nWith SQL, I will get a lot more powerful features than I would ever want to code myself. Seems like a clear advantage (even with sqlite).\nI won't need to debug my own implementation of tables, but debugging mistakes in SQL are hard since I can't put breakpoints or easily print out interim state. I don't know how to judge the overall impact of my code reliability and debugging time.\nThe code will be easier to read, since instead of calling my own custom methods I would write SQL (everyone who needs to maintain this code knows SQL). However, the Python code to deal with database might be uglier and more complex than the code that uses pure Python class Table. Again, I don't know which is better on balance.\n\nAny corrections to the above, or anything else I should think about?","AnswerCount":3,"Available Count":3,"Score":1.2,"is_accepted":true,"ViewCount":903,"Q_Id":4136800,"Users Score":5,"Answer":"SQLite does not run in a separate process. So you don't actually have any extra overhead from IPC. But IPC overhead isn't that big, anyway, especially over e.g., UNIX sockets. If you need multiple writers (more than one process\/thread writing to the database simultaneously), the locking overhead is probably worse, and MySQL or PostgreSQL would perform better, especially if running on the same machine. The basic SQL supported by all three of these databases is the same, so benchmarking isn't that painful.\nYou generally don't have to do the same type of debugging on SQL statements as you do on your own implementation. SQLite works, and is fairly well debugged already. It is very unlikely that you'll ever have to debug \"OK, that row exists, why doesn't the database find it?\" and track down a bug in index updating. Debugging SQL is completely different than procedural code, and really only ever happens for pretty complicated queries.\nAs for debugging your code, you can fairly easily centralize your SQL calls and add tracing to log the queries you are running, the results you get back, etc. The Python SQLite interface may already have this (not sure, I normally use Perl). It'll probably be easiest to just make your existing Table class a wrapper around SQLite.\nI would strongly recommend not reinventing the wheel. SQLite will have far fewer bugs, and save you a bunch of time. (You may also want to look into Firefox's fairly recent switch to using SQLite to store history, etc., I think they got some pretty significant speedups from doing so.)\nAlso, SQLite's well-optimized C implementation is probably quite a bit faster than any pure Python implementation.","Q_Score":4,"Tags":"python,performance,sqlite","A_Id":4136841,"CreationDate":"2010-11-09T17:49:00.000","Title":"Pros and cons of using sqlite3 vs custom table implementation","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I noticed that a significant part of my (pure Python) code deals with tables. Of course, I have class Table which supports the basic functionality, but I end up adding more and more features to it, such as queries, validation, sorting, indexing, etc.\nI to wonder if it's a good idea to remove my class Table, and refactor the code to use a regular relational database that I will instantiate  in-memory.\nHere's my thinking so far:\n\nPerformance of queries and indexing would improve but communication between Python code and the separate database process might be less efficient than between Python functions. I assume that is too much overhead, so I would have to go with sqlite which comes with Python and lives in the same process. I hope this means it's a pure performance gain (at the cost of non-standard SQL definition and limited features of sqlite).\nWith SQL, I will get a lot more powerful features than I would ever want to code myself. Seems like a clear advantage (even with sqlite).\nI won't need to debug my own implementation of tables, but debugging mistakes in SQL are hard since I can't put breakpoints or easily print out interim state. I don't know how to judge the overall impact of my code reliability and debugging time.\nThe code will be easier to read, since instead of calling my own custom methods I would write SQL (everyone who needs to maintain this code knows SQL). However, the Python code to deal with database might be uglier and more complex than the code that uses pure Python class Table. Again, I don't know which is better on balance.\n\nAny corrections to the above, or anything else I should think about?","AnswerCount":3,"Available Count":3,"Score":0.2605204458,"is_accepted":false,"ViewCount":903,"Q_Id":4136800,"Users Score":4,"Answer":"You could try to make a sqlite wrapper with the same interface as your class Table, so that you keep your code clean and you get the sqlite performences.","Q_Score":4,"Tags":"python,performance,sqlite","A_Id":4136876,"CreationDate":"2010-11-09T17:49:00.000","Title":"Pros and cons of using sqlite3 vs custom table implementation","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I noticed that a significant part of my (pure Python) code deals with tables. Of course, I have class Table which supports the basic functionality, but I end up adding more and more features to it, such as queries, validation, sorting, indexing, etc.\nI to wonder if it's a good idea to remove my class Table, and refactor the code to use a regular relational database that I will instantiate  in-memory.\nHere's my thinking so far:\n\nPerformance of queries and indexing would improve but communication between Python code and the separate database process might be less efficient than between Python functions. I assume that is too much overhead, so I would have to go with sqlite which comes with Python and lives in the same process. I hope this means it's a pure performance gain (at the cost of non-standard SQL definition and limited features of sqlite).\nWith SQL, I will get a lot more powerful features than I would ever want to code myself. Seems like a clear advantage (even with sqlite).\nI won't need to debug my own implementation of tables, but debugging mistakes in SQL are hard since I can't put breakpoints or easily print out interim state. I don't know how to judge the overall impact of my code reliability and debugging time.\nThe code will be easier to read, since instead of calling my own custom methods I would write SQL (everyone who needs to maintain this code knows SQL). However, the Python code to deal with database might be uglier and more complex than the code that uses pure Python class Table. Again, I don't know which is better on balance.\n\nAny corrections to the above, or anything else I should think about?","AnswerCount":3,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":903,"Q_Id":4136800,"Users Score":0,"Answer":"If you're doing database work, use a database, if your not, then don't. Using tables, it sound's like you are. I'd recommend using an ORM to make it more pythonic. SQLAlchemy is the most flexible (though it's not strictly just an ORM).","Q_Score":4,"Tags":"python,performance,sqlite","A_Id":4136862,"CreationDate":"2010-11-09T17:49:00.000","Title":"Pros and cons of using sqlite3 vs custom table implementation","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"The context: I'm working on some Python scripts on an Ubuntu server. I need to use some code written in Python 2.7 but our server has Python 2.5. We installed 2.7 as a second instance of Python so we wouldn't break anything reliant on 2.5. Now I need to install the MySQLdb package. I assume I can't do this the easy way by running apt-get install python-mysqldb because it will likely just reinstall to python 2.5, so I am just trying to install it manually.\nThe Problem: In the MySQL-python-1.2.3 directory I try to run python2.7 setup.py build and get an error that states: \n\nsh: \/etc\/mysql\/my.cnf: Permission denied\n\nalong with a Traceback that says setup.py couldn't find the file. \nNote that the setup.py script looks for a mysql_config file in the $PATH directories by default, but the mysql config file for our server is \/etc\/mysql\/my.cnf, so I changed the package's site.cfg file to match. I checked the permissions for the file, which are -rw-r--r--. I tried running the script as root and got the same error.\nAny suggestions?","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":429,"Q_Id":4138504,"Users Score":0,"Answer":"Are you sure that file isn't hardcoded in some other portion of the build process? Why not just add it to you $PATH for the duration of the build?\nDoes the script need to write that file for some reason? Does the build script use su or sudo to attempt to become some other user? Are you absolutely sure about both the permissions and the fact that you ran the script as root?\nIt's a really weird thing if you still can't get to it. Are you using a chroot or a virtualenv?","Q_Score":3,"Tags":"python,mysql,permissions,configuration-files","A_Id":4139191,"CreationDate":"2010-11-09T20:52:00.000","Title":"Trouble installing MySQLdb for second version of Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":0},{"Question":"The context: I'm working on some Python scripts on an Ubuntu server. I need to use some code written in Python 2.7 but our server has Python 2.5. We installed 2.7 as a second instance of Python so we wouldn't break anything reliant on 2.5. Now I need to install the MySQLdb package. I assume I can't do this the easy way by running apt-get install python-mysqldb because it will likely just reinstall to python 2.5, so I am just trying to install it manually.\nThe Problem: In the MySQL-python-1.2.3 directory I try to run python2.7 setup.py build and get an error that states: \n\nsh: \/etc\/mysql\/my.cnf: Permission denied\n\nalong with a Traceback that says setup.py couldn't find the file. \nNote that the setup.py script looks for a mysql_config file in the $PATH directories by default, but the mysql config file for our server is \/etc\/mysql\/my.cnf, so I changed the package's site.cfg file to match. I checked the permissions for the file, which are -rw-r--r--. I tried running the script as root and got the same error.\nAny suggestions?","AnswerCount":2,"Available Count":2,"Score":0.1973753202,"is_accepted":false,"ViewCount":429,"Q_Id":4138504,"Users Score":2,"Answer":"As far as I'm aware, there is a very significant difference between \"mysql_config\" and \"my.cnf\".\n\n\"mysql_config\" is usually located in the \"bin\" folder of your MySQL install and when executed, spits out various filesystem location information about your install.\n\"my.cnf\" is a configuration script used by MySQL itself.\n\nIn short, when the script asks for \"mysql_config\", it should be taken to literally mean the executable file with a name of \"mysql_config\" and not the textual configuration file you're feeding it. MYSQLdb needs the \"mysql_config\" file so that it knows which libraries to use. That's it. It does not read your MySQL configuration directly.\nThe errors you are experiencing can be put down to;\n\nIt's trying to open the wrong file and running into permission trouble.\nEven after it has tried to open that file, it still can't find the \"mysql_config\" file.\n\nFrom here, you need to locate your MySQL installation's \"bin\" folder and check it contains \"mysql_config\". Then you can edit the folder path into the \"site.cnf\" file and you should be good to go.","Q_Score":3,"Tags":"python,mysql,permissions,configuration-files","A_Id":4139563,"CreationDate":"2010-11-09T20:52:00.000","Title":"Trouble installing MySQLdb for second version of Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":0},{"Question":"I'd like to develop a small\/medium-size cross-platform application (including GUI).\nMy background: mostly web applications with MVC architectures, both Python (Pylons + SqlAlchemy) and Java (know the language well, but don't like it that much). I also know some C#. So far, I have no GUI programming experience (neither Windows Forms, Swing nor QT).\nI plan to use SQLite for data storage: It seems to be a nice cross-platform solution and has some powerful features (e.g. full text search, which SQL Server Compact lacks).\nI have done some research and these are my favorite options:\n\n\n1) QT, Python (PyQT or PySide), and SQLAlchemy\npros:\n\nPython the language\nopen source is strong in the Python world (lots of libraries and users)\nSQLAlchemy: A fantastic way to interact with a DB and incredibly well documented!\n\ncons:\n\ncompilation, distribution and deployment more difficult?\nno QT experience\nQT Designer not as nice as the Visual Studio Winforms designer\n\n\n\n2) .NET\/Mono, Windows Forms, C#, (Fluent) NHibernate, System.Data.SQLite\npros:\n\nC# (I like it, especially compared to Java and would like to get more experience in it)\nThe Winforms GUI designer in Visual Studio seems really slick\nIntelliSense\nClickOnce Deployment(?)\nWindows Forms look and feel good on Windows\n\ncons:\n\n(Fluent) NHibernate far less documented than SQLAlchemy; also annoying: Fluent docs refer to NHibernate docs which refer to Hibernate (aargh!). But plain NHibernate + XML does not look very comfortable.\nWindows Forms will not look + behave native on Linux\/Mac OS (correct?)\nfewer open source libraries in the .NET world, fewer OSS users, less documentation in general\nno WinForms and NHibernate experience\n\n\n\n3) JVM, Java + Jython, Swing, SQLAlchemy\n(I'm emotionally biased against this one, but listed for completeness sake)\npros:\n\nJVM\/Swing work well as cross-platform basis\nJython\nSQLAlchemy\nlots of open source libraries\n\ncons:\n\nSwing seems ugly and difficult to layout\nlacks a good GUI designer\nGuessing that I won't be able to avoid Java for UI stuff\nNot sure how stable the Jython\/Java integration is\n\n(Options that I have ruled out... just to avoid discussion on these):\n- wxWidgets\/wxPython (now that QT is LGPLed)\n- GTK\/PyGTK\nThe look and feel of the final application is very important to me. The above technology stacks are very different (PyQT, .NET WinForms, JVM Swing) and require some time to get proficient, so:\nWhich alternative would you recommend and why?","AnswerCount":1,"Available Count":1,"Score":0.761594156,"is_accepted":false,"ViewCount":3111,"Q_Id":4145350,"Users Score":5,"Answer":"I'm a Python guy and use PyQt myself, and I can wholly recommend it. Concerning your cons:\n\ncompilation, distribution and deployment more difficult?\n\nNo, not really. For many projects, a full setup.py for e.g. cx_Freeze can be less than 30 lines that rarely need to change (most import dependencies are detected automatically, only need to specify the few modules that are not recognized), and then python setup.py will build a standalone executable. Then you can distribute it just like e.g. a C++ .exe.\n\nno QT experience\n\nI didn't have notable GUI experience either when I started out with Qt (only a bit of fiddling with Tkinter), but I grew to love Qt. Most of the time, all widgets work seamlessly and do what they're supposed to do - and there's a lot of them for many purposes. You name it, there's probably a widget that does it, and doesn't annoy the user by being half-assed. All the nice things we've been spoiled with are there.\nQt is huge, but the PyQt documentation answer most question with reasonable search effort. And if all else fails and you know a bit of C++, you can also look at Qt resources.\n\nQT Designer not as nice as the Visual Studio Winforms designer \n\nI don't know the VS Winforms designer, but I must admit that the Qt Designer is lacking. I ended up making a sketch of the UI in the designer, generating the code, cleaning that up and taking care all remaining details by hand. It works out okay so far, but my projects are rather small.\n\nPS:\n\n(now that QT is LGPLed)\n\nPyQt is still GPL only. PySide is LGPL, yes, but it's not that mature, if that's a concern. The project website states that \"starting development on PySide should be pretty safe now\" though.","Q_Score":11,"Tags":"c#,java,python,user-interface,cross-platform","A_Id":4145581,"CreationDate":"2010-11-10T14:11:00.000","Title":"Python + QT, Windows Forms or Swing for a cross-platform application?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":1,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm programming a web application using sqlalchemy. Everything was smooth during the first phase of development when the site was not in production. I could easily change the database schema by simply deleting the old sqlite database and creating a new one from scratch. \nNow the site is in production and I need to preserve the data, but I still want to keep my original development speed by easily converting the database to the new schema. \nSo let's say that I have model.py at revision 50 and model.py a revision 75, describing the schema of the database. Between those two schema most changes are trivial, for example a new column is declared with a default value and I just want to add this default value to old records. \nEventually a few changes may not be trivial and require some pre-computation. \nHow do (or would) you handle fast changing web applications with, say, one or two new version of the production code per day  ?\nBy the way, the site is written in Pylons if this makes any difference.","AnswerCount":4,"Available Count":1,"Score":1.0,"is_accepted":false,"ViewCount":32073,"Q_Id":4165452,"Users Score":16,"Answer":"What we do.\n\nUse \"major version\".\"minor version\" identification of your applications.  Major version is  the schema version number.  The major number is no some random \"enough new functionality\" kind of thing.  It's a formal declaration of compatibility with database schema.\nRelease 2.3 and 2.4 both use schema version 2.\nRelease 3.1 uses the version 3 schema.\nMake the schema version very, very visible.  For SQLite, this means keep the schema version number in the database file name.  For MySQL, use the database name.  \nWrite migration scripts.  2to3.py,  3to4.py.  These scripts work in two phases.  (1) Query the old data into the new structure creating simple CSV or JSON files.  (2) Load the new structure from the simple CSV or JSON files with no further processing.  These extract files -- because they're in the proper structure, are fast to load and can easily be used as unit test fixtures.  Also, you never have two databases open at the same time. This makes the scripts slightly simpler.  Finally, the load files can be used to move the data to another database server.\n\nIt's very, very hard to \"automate\" schema migration.  It's easy (and common) to have database surgery so profound that an automated script can't easily map data from old schema to new schema.","Q_Score":63,"Tags":"python,sqlalchemy,pylons,data-migration,migrate","A_Id":4165496,"CreationDate":"2010-11-12T14:08:00.000","Title":"How to efficiently manage frequent schema changes using sqlalchemy?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Can anyone help me install Apache with mod_wsgi to run Python for implementation of RESTful Web services. We're trying to get rid of our existing Java REST services with Apache Tomcat.\nThe installation platform is SUSE Linux Enterprise. Please provide a step by step installation procedure with required modules, as I tried it and everytime was missinhg one module or other either in Python installation or Apache installation.\nI followed the standard Installation steps for all 3, Apache, Python and mod_wsgi, but didn't work out for me.\nWould this work at all? Do you have any other suggestions?","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":2568,"Q_Id":4167684,"Users Score":0,"Answer":"Check if mod_wsgi is loaded as a module into the httpd.conf\nAdd apache host that points to a python\/wsgi module which contains the 'def application' definition for your web-service. \nResolve any path issues that maybe arise from your import handling.\n\nIf this doesn't work, drop some error-dump here and we'll check.","Q_Score":0,"Tags":"python,apache,rest,mod-wsgi,mod-python","A_Id":4168054,"CreationDate":"2010-11-12T18:07:00.000","Title":"Install Apache with mod_wsgi to use Python for RESTful web services and Apache for web pages","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"i want to create application in windows. i need to use databases which would be preferable best for pyqt application\nlike\nsqlalchemy\nmysql\netc.","AnswerCount":4,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":535,"Q_Id":4168020,"Users Score":0,"Answer":"i guess its totally upto you ..but as far as i am concerned i personlly use sqlite, becoz it is easy to use and amazingly simple syntax whereas for MYSQL u can use it for complex apps and has  options for performance tuning. but in end its totally upto u and wt your app requires","Q_Score":0,"Tags":"python,database,pyqt","A_Id":4208750,"CreationDate":"2010-11-12T18:49:00.000","Title":"which databases can be used better for pyqt application","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":1,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"i want to create application in windows. i need to use databases which would be preferable best for pyqt application\nlike\nsqlalchemy\nmysql\netc.","AnswerCount":4,"Available Count":3,"Score":0.049958375,"is_accepted":false,"ViewCount":535,"Q_Id":4168020,"Users Score":1,"Answer":"SQlite is fine for a single user. \nIf you are going over a network to talk to a central database, then you need a database woith a decent Python lirary. \nTake a serious look at MySQL if you need\/want SQL. \nOtherwise, there is CouchDB in the Not SQL camp, which is great if you are storing documents, and can express searches as Map\/reduce functions. Poor for adhoc queries.","Q_Score":0,"Tags":"python,database,pyqt","A_Id":4294636,"CreationDate":"2010-11-12T18:49:00.000","Title":"which databases can be used better for pyqt application","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":1,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"i want to create application in windows. i need to use databases which would be preferable best for pyqt application\nlike\nsqlalchemy\nmysql\netc.","AnswerCount":4,"Available Count":3,"Score":0.049958375,"is_accepted":false,"ViewCount":535,"Q_Id":4168020,"Users Score":1,"Answer":"If you want a relational database I'd recommend you to use SQLAlchemy, as you then get a choice as well as an ORM. Bu default go with SQLite, as per other recommendations here.\nIf you don't need a relational database, take a look at ZODB. It's an awesome Python-only object-oriented database.","Q_Score":0,"Tags":"python,database,pyqt","A_Id":4512428,"CreationDate":"2010-11-12T18:49:00.000","Title":"which databases can be used better for pyqt application","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":1,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have my own unit testing suite based on the unittest library. I would like to track the history of each test case being run. I would also like to identify after each run tests which flipped from PASS to FAIL or vice versa.\nI have very little knowledge about databases, but it seems that I could utilize sqlite3 for this task.\nAre there any existing solutions which integrate unittest and a database?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":280,"Q_Id":4170442,"Users Score":0,"Answer":"Technically, yes. The only thing that you need is some kind of scripting language or shell script that can talk to sqlite.\nYou should think of a database like a file in a file system where you don't have to care about the file format. You just say, here are tables of data, with columns. And each row of that is one record. Much like in a Excel table.\nSo if you are familiar with shell scripts or calling command line tools, you can install sqlite and use the sqlitecommand to interact with the database.\nAlthough I think the first thing you should do is to learn basic SQL. There are a lot of SQL tutorials out there.","Q_Score":1,"Tags":"python,unit-testing,sqlite","A_Id":4170458,"CreationDate":"2010-11-13T01:33:00.000","Title":"Using sqlite3 to track unit test results","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm trying to use a MongoDB Database from a Google App Engine service is that possible? How do I install the PyMongo driver on Google App Engine? Thanks","AnswerCount":3,"Available Count":1,"Score":0.0665680765,"is_accepted":false,"ViewCount":1355,"Q_Id":4178742,"Users Score":1,"Answer":"It's not possible because you don't have access to networks sockets in App Engine. As long as you cannot access the database via HTTP, it's impossible.","Q_Score":4,"Tags":"python,google-app-engine,mongodb,pymongo","A_Id":4179091,"CreationDate":"2010-11-14T17:42:00.000","Title":"is it possible to use PyMongo in Google App Engine?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"We're rewriting a website used by one of our clients. The user traffic on it is very low, less than 100 unique visitors a week. It's basically just a nice interface to their data in our databases. It allows them to query and filter on different sets of data of theirs.\nWe're rewriting the site in Python, re-using the same Oracle database that the data is currently on. The current version is written in an old, old version of Coldfusion. One of the things that Coldfusion does well though is displays tons of database records on a single page. It's capable of displaying hundreds of thousands of rows at once without crashing the browser. It uses a Java applet, and it looks like the contents of the rows are perhaps compressed and passed in through the HTML or something. There is a large block of data in the HTML but it's not displayed - it's just rendered by the Java applet.\nI've tried several JavaScript solutions but they all hinge on the fact that the data will be present in an HTML table or something along those lines. This causes browsers to freeze and run out of memory.\nDoes anyone know of any solutions to this situation? Our client loves the ability to scroll through all of this data without clicking a \"next page\" link.","AnswerCount":6,"Available Count":1,"Score":0.0333209931,"is_accepted":false,"ViewCount":3442,"Q_Id":4186384,"Users Score":1,"Answer":"Most people, in this case, would use a framework. The best documented and most popular framework in Python is Django. It has good database support (including Oracle), and you'll have the easiest time getting help using it since there's such an active Django community.\nYou can try some other frameworks, but if you're tied to Python I'd recommend Django.\nOf course, Jython (if it's an option), would make your job very easy. You could take the existing Java framework you have and just use Jython to build a frontend (and continue to use your Java applet and Java classes and Java server).\nThe memory problem is an interesting one; I'd be curious to see what you come up with.","Q_Score":7,"Tags":"python,html,oracle,coldfusion","A_Id":4186505,"CreationDate":"2010-11-15T16:18:00.000","Title":"How to display database query results of 100,000 rows or more with HTML?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am implementing a class that resembles a typical database table: \n\nhas named columns and unnamed rows\nhas a primary key by which I can refer to the rows\nsupports retrieval and assignment by primary key and column title\ncan be asked to add unique or non-unique index for any of the columns, allowing fast retrieval of a row (or set of rows) which have a given value in that column\nremoval of a row is fast and is implemented as \"soft-delete\": the row is kept physically, but is marked for deletion and won't show up in any subsequent retrieval operations\naddition of a column is fast\nrows are rarely added\ncolumns are rarely deleted\n\nI decided to implement the class directly rather than use a wrapper around sqlite. \nWhat would be a good data structure to use?\n\nJust as an example, one approach I was thinking about is a dictionary. Its keys are the values in the primary key column of the table; its values are the rows implemented in one of these ways:\n\nAs lists. Column numbers are mapped into column titles (using a list for one direction and a map for the other). Here, a retrieval operation would first convert column title into column number, and then find the corresponding element in the list.\nAs dictionaries. Column titles are the keys of this dictionary.\n\nNot sure about the pros\/cons of the two.\n\nThe reasons I want to write my own code are:\n\nI need to track row deletions. That is, at any time I want to be able to report which rows where deleted and for what \"reason\" (the \"reason\" is passed to my delete method).\nI need some reporting during indexing (e.g., while an non-unique index is being built, I want to check certain conditions and report if they are violated)","AnswerCount":3,"Available Count":2,"Score":0.1325487884,"is_accepted":false,"ViewCount":1361,"Q_Id":4188202,"Users Score":2,"Answer":"I would consider building a dictionary with keys that are tuples or lists. Eg: my_dict((\"col_2\", \"row_24\")) would get you this element. Starting from there, it would be pretty easy (if not extremely fast for very large databases) to write 'get_col' and 'get_row' methods, as well as 'get_row_slice' and 'get_col_slice' from the 2 preceding ones to gain access to your methods.\nUsing a whole dictionary like that will have 2 advantages. 1) Getting a single element will be faster than your 2 proposed methods; 2) If you want to have different number of elements (or missing elements) in your columns, this will make it extremely easy and memory efficient.\nJust a thought :) I'll be curious to see what packages people will suggest!\nCheers","Q_Score":6,"Tags":"python,performance,data-structures,implementation","A_Id":4188260,"CreationDate":"2010-11-15T19:48:00.000","Title":"How to implement database-style table in Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am implementing a class that resembles a typical database table: \n\nhas named columns and unnamed rows\nhas a primary key by which I can refer to the rows\nsupports retrieval and assignment by primary key and column title\ncan be asked to add unique or non-unique index for any of the columns, allowing fast retrieval of a row (or set of rows) which have a given value in that column\nremoval of a row is fast and is implemented as \"soft-delete\": the row is kept physically, but is marked for deletion and won't show up in any subsequent retrieval operations\naddition of a column is fast\nrows are rarely added\ncolumns are rarely deleted\n\nI decided to implement the class directly rather than use a wrapper around sqlite. \nWhat would be a good data structure to use?\n\nJust as an example, one approach I was thinking about is a dictionary. Its keys are the values in the primary key column of the table; its values are the rows implemented in one of these ways:\n\nAs lists. Column numbers are mapped into column titles (using a list for one direction and a map for the other). Here, a retrieval operation would first convert column title into column number, and then find the corresponding element in the list.\nAs dictionaries. Column titles are the keys of this dictionary.\n\nNot sure about the pros\/cons of the two.\n\nThe reasons I want to write my own code are:\n\nI need to track row deletions. That is, at any time I want to be able to report which rows where deleted and for what \"reason\" (the \"reason\" is passed to my delete method).\nI need some reporting during indexing (e.g., while an non-unique index is being built, I want to check certain conditions and report if they are violated)","AnswerCount":3,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":1361,"Q_Id":4188202,"Users Score":0,"Answer":"You really should use SQLite.\nFor your first reason (tracking deletion reasons) you can easily implement this by having a second table that you \"move\" rows to on deletion.  The reason can be tracked in additional column in that table or another table you can join.  If a deletion reason isn't always required then you can even use triggers on your source table to copy rows about to be deleted, and\/or have a user defined function that can get the reason.\nThe indexing reason is somewhat covered by constraints etc but I can't directly address it without more details.","Q_Score":6,"Tags":"python,performance,data-structures,implementation","A_Id":4231416,"CreationDate":"2010-11-15T19:48:00.000","Title":"How to implement database-style table in Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am using the mysql connector (https:\/\/launchpad.net\/myconnpy) with SQLAlchemy and, though the table is definitely UTF8, any string columns returned are just normal strings not unicode. The documentation doesn't list any specific parameters for UTF8\/unicode support for the mysql connector driver so I borrowed from the mysqldb driver. Here is my connect string:\nmysql+mysqlconnector:\/\/user:pass@myserver.com\/mydbname?charset=utf8&use_unicode=0\nI'd really prefer to keep using this all-python mysql driver. Any suggestions?","AnswerCount":2,"Available Count":1,"Score":-0.2913126125,"is_accepted":false,"ViewCount":1239,"Q_Id":4191370,"Users Score":-3,"Answer":"Sorry, i don't know about the connector, i use MySQLDB and it is working quite nicely. I work in UTF8 as well and i didn't have any problem.","Q_Score":1,"Tags":"python,mysql,unicode,sqlalchemy","A_Id":4192633,"CreationDate":"2010-11-16T05:06:00.000","Title":"MySql Connector (python) and SQLAlchemy Unicode problem","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"What the difference is between flush() and commit() in SQLAlchemy?\nI've read the docs, but am none the wiser - they seem to assume a pre-understanding that I don't have.\nI'm particularly interested in their impact on memory usage. I'm loading some data into a database from a series of files (around 5 million rows in total) and my session is occasionally falling over - it's a large database and a machine with not much memory. \nI'm wondering if I'm using too many commit() and not enough flush() calls - but without really understanding what the difference is, it's hard to tell!","AnswerCount":6,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":180674,"Q_Id":4201455,"Users Score":0,"Answer":"commit () records these changes in the database. flush () is always called as part of the commit () (1) call. When you use a Session object to query a database, the query returns results from both the database and the reddened parts of the unrecorded transaction it is performing.","Q_Score":569,"Tags":"python,sqlalchemy","A_Id":65843088,"CreationDate":"2010-11-17T04:20:00.000","Title":"SQLAlchemy: What's the difference between flush() and commit()?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm using sqlite with python. I'm implementing the POP3 protocol. I have a table \n\nmsg_id text\ndate text\nfrom_sender text\nsubject text\nbody text\nhashkey text\n\nNow I need to check for duplicate messages by checking the message id of the message retrieved against the existing msg_id's in the table. I encrypted the msg_id using md5 and put it in the hashkey column. Whenever I retrieve mail, I hash the message id and check it with the table values. Heres what I do.\n\n\ndef check_duplicate(new):\n    conn = sql.connect(\"mail\")\n    c = conn.cursor()\n    m = hashlib.md5()\n    m.update(new)\n    c.execute(\"select hashkey from mail\")\n    for row in c:\n        if m.hexdigest() == row:\n            return 0\n        else:\n            continue\n\n    return 1\n\nIt just refuses to work correctly. I tried printing the row value, it shows it in unicode, thats where the problem lies as it cannot compare properly. \nIs there a better way to do this, or to improve my method?","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":481,"Q_Id":4208146,"Users Score":0,"Answer":"The main issue is that you're trying to compare a Python string (m.hexdigest()) with a tuple.\nAdditionally, another poster's suggestion that you use SQL for the comparison is probably good advice. Another SQL suggestion would be to fix your columns -- TEXT for everything probably isn't what you want; an index on your hashkey column is very likely a good thing.","Q_Score":0,"Tags":"python,sql,sqlite","A_Id":4208359,"CreationDate":"2010-11-17T19:08:00.000","Title":"Comparing sql values","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Which is more expensive to do in terms of resources and efficiency, File read\/write operation or Database Read\/Write operation? \nI'm using MongoDB, with Python. I't be preforming about 100k requests on the db\/file per minute. Also, there's about 15000 documents in the database \/ file.\nWhich would be faster? thanks in advance.","AnswerCount":5,"Available Count":5,"Score":1.0,"is_accepted":false,"ViewCount":3529,"Q_Id":4210057,"Users Score":6,"Answer":"It depends.. if you need to read sequenced data, file might be faster, if you need to read random data, database has better chances to be optimized to your needs.\n(after all - database reads it's records from a file as well, but it has an internal structure and algorithms to enhance performance, it can use the memory in a smarter way, and do a lot in the background so the results will come faster)\nin an intensive case of random reading - I will go with the database option.","Q_Score":4,"Tags":"python,performance,mongodb","A_Id":4210090,"CreationDate":"2010-11-17T22:58:00.000","Title":"Is a file read faster than reading data from the database?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"Which is more expensive to do in terms of resources and efficiency, File read\/write operation or Database Read\/Write operation? \nI'm using MongoDB, with Python. I't be preforming about 100k requests on the db\/file per minute. Also, there's about 15000 documents in the database \/ file.\nWhich would be faster? thanks in advance.","AnswerCount":5,"Available Count":5,"Score":0.0399786803,"is_accepted":false,"ViewCount":3529,"Q_Id":4210057,"Users Score":1,"Answer":"Reading from a database can be more efficient, because you can access records directly and make use of indexes etc. With normal flat files you basically have to read them sequentially. (Mainframes support direct access files, but these are sort of halfway between flat files and databases).\nIf you are in a multi-user environment, you must make sure that your data remain consistent even if multiple users try updates at the same time. With flat files, you have to lock the file for all but one user until she is ready with her update, and then lock for the next. Databases can do locking on row level.\nYou can make a file based system as efficient as a database, but that effort amounts to writing a database system yourself.","Q_Score":4,"Tags":"python,performance,mongodb","A_Id":49248435,"CreationDate":"2010-11-17T22:58:00.000","Title":"Is a file read faster than reading data from the database?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"Which is more expensive to do in terms of resources and efficiency, File read\/write operation or Database Read\/Write operation? \nI'm using MongoDB, with Python. I't be preforming about 100k requests on the db\/file per minute. Also, there's about 15000 documents in the database \/ file.\nWhich would be faster? thanks in advance.","AnswerCount":5,"Available Count":5,"Score":0.1194272985,"is_accepted":false,"ViewCount":3529,"Q_Id":4210057,"Users Score":3,"Answer":"There are too many factors to offer a concrete answer, but here's a list for you to consider:\n\nDisk bandwidth\nDisk latency\nDisk cache\nNetwork bandwidth\nMongoDB cluster size\nVolume of MongoDB client activity (the disk only has one \"client\" unless your machine is busy with other workloads)","Q_Score":4,"Tags":"python,performance,mongodb","A_Id":4210106,"CreationDate":"2010-11-17T22:58:00.000","Title":"Is a file read faster than reading data from the database?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"Which is more expensive to do in terms of resources and efficiency, File read\/write operation or Database Read\/Write operation? \nI'm using MongoDB, with Python. I't be preforming about 100k requests on the db\/file per minute. Also, there's about 15000 documents in the database \/ file.\nWhich would be faster? thanks in advance.","AnswerCount":5,"Available Count":5,"Score":0.0,"is_accepted":false,"ViewCount":3529,"Q_Id":4210057,"Users Score":0,"Answer":"If caching is not used sequential IO operations are faster with files by definition. Databases eventually use files, but they have more layers to pass before data hit the file. But if you want to query data using database is more efficient, because if you choose files you will have to implement it yourselves. For your task i recommend to research clustering for different databases, they can scale to your rate.","Q_Score":4,"Tags":"python,performance,mongodb","A_Id":4210113,"CreationDate":"2010-11-17T22:58:00.000","Title":"Is a file read faster than reading data from the database?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"Which is more expensive to do in terms of resources and efficiency, File read\/write operation or Database Read\/Write operation? \nI'm using MongoDB, with Python. I't be preforming about 100k requests on the db\/file per minute. Also, there's about 15000 documents in the database \/ file.\nWhich would be faster? thanks in advance.","AnswerCount":5,"Available Count":5,"Score":0.1586485043,"is_accepted":false,"ViewCount":3529,"Q_Id":4210057,"Users Score":4,"Answer":"Try it and tell us the answer.","Q_Score":4,"Tags":"python,performance,mongodb","A_Id":4210368,"CreationDate":"2010-11-17T22:58:00.000","Title":"Is a file read faster than reading data from the database?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"i have a noob question.\nI have a record in a table that looks like '\\1abc'\nI then use this string as a regex replacement in re.sub(\"([0-9])\",thereplacement,\"2\")\nI'm a little confused with the backslashes. The string i got back was \"\\\\1abc\"","AnswerCount":2,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":191,"Q_Id":4224400,"Users Score":2,"Answer":"Note that you can make \\ stop being an escape character by setting standard_conforming_strings to on.","Q_Score":0,"Tags":"python,postgresql","A_Id":4226375,"CreationDate":"2010-11-19T11:11:00.000","Title":"regarding backslash from postgresql","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Short Question:\nIs there any nosql flat-file database available as sqlite?\nExplanation:\nFlat file database can be opened in different processes to read, and keep one process to write. I think its perfect for read cache if there's no strict consistent needed. Say 1-2 secs write to the file or even memory block and the readers get updated data after that.\nSo I almost choose to use sqlite, as my python server read cache. But there's still one problem. I don't like to rewrite sqls again in another place and construct another copy of my data tables in sqlite just as the same as I did in PostgreSql which used as back-end database.\nso is there any other choice?thanks!","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":28380,"Q_Id":4245438,"Users Score":0,"Answer":"Something trivial but workable, if you are looking storage backed up key value data structure use pickled dictionary. Use cPickle for better performance if needed.","Q_Score":49,"Tags":"python,database,caching,sqlite,nosql","A_Id":15588028,"CreationDate":"2010-11-22T12:36:00.000","Title":"Is there any nosql flat file database just as sqlite?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Is there a Python module that writes Excel 2007+ files?\nI'm interested in writing a file longer than 65535 lines and only Excel 2007+ supports it.","AnswerCount":8,"Available Count":1,"Score":0.024994793,"is_accepted":false,"ViewCount":21620,"Q_Id":4257771,"Users Score":1,"Answer":"If you are on Windows and have Excel 2007+ installed, you should be able to use pywin32 and COM to write XLSX files using almost the same code as you would would to write XLS files ... just change the \"save as ....\" part at the end.\nProbably, you can also write XLSX files using Excel 2003 with the freely downloadable add-on kit but the number of rows per sheet would be limited to 64K.","Q_Score":14,"Tags":"python,excel,excel-2007,openpyxl","A_Id":4258896,"CreationDate":"2010-11-23T15:36:00.000","Title":"Python: Writing to Excel 2007+ files (.xlsx files)","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I've built a number of python driven sites that utilize mongodb as a database backend and am very happy with it's ObjectId system, however, I'd love to be able encode the ids in a shorter fashion without building a mapping collection or utilizing a url-shortener service.\nSuggestions? Success stories?","AnswerCount":5,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":4165,"Q_Id":4261129,"Users Score":0,"Answer":"If you can generate auto-incrementing unique numbers, there's absolutely no need to use ObjectId for _id. Doing this in a distributed environment will most likely be more expensive than using ObjectId. That's your tradeoff.","Q_Score":14,"Tags":"python,mongodb","A_Id":8654689,"CreationDate":"2010-11-23T21:26:00.000","Title":"How can one shorten mongo ids for better use in URLs?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I've built a number of python driven sites that utilize mongodb as a database backend and am very happy with it's ObjectId system, however, I'd love to be able encode the ids in a shorter fashion without building a mapping collection or utilizing a url-shortener service.\nSuggestions? Success stories?","AnswerCount":5,"Available Count":2,"Score":0.0399786803,"is_accepted":false,"ViewCount":4165,"Q_Id":4261129,"Users Score":1,"Answer":"If you are attempting to retain the original value then there really is not a good way. You could encode it, but the likeliness of it being smaller is minimal. You could hash it, but then it's not reversible.\nIf this is a REQUIREMENT, I'd probably recommend creating a lookup table or collection where a small incremental number references entries in a Mongo Collection.","Q_Score":14,"Tags":"python,mongodb","A_Id":4261319,"CreationDate":"2010-11-23T21:26:00.000","Title":"How can one shorten mongo ids for better use in URLs?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"When creating a virtual environment with no -site packages do I need to install mysql & the mysqldb adapter which is in my global site packages in order to use them in my virtual project environment?","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":920,"Q_Id":4273729,"Users Score":5,"Answer":"You can also (on UNIX) symlink specific packages from the Python site-packages into your virtualenv's site-packages.","Q_Score":4,"Tags":"python,virtualenv","A_Id":4273823,"CreationDate":"2010-11-25T04:29:00.000","Title":"Python Virtualenv","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm using SqlAlchemy in my Pylons application to access data and SqlAlchemy-migrate to maintain the database schema.\nIt works fine for managing the schema itself. However, I also want to manage seed data in a migrate-like way. E.g. when ProductCategory table is created it would make sense to seed it with categories data.\nLooks like SqlAlchemy-migrate does not support this directly. What would be a good approach to do this with Pylons+SqlAlchemy+SqlAlchemy-migrate?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":2454,"Q_Id":4298886,"Users Score":2,"Answer":"Well what format is your seed data starting out in? The migrate calls are just python methods so you're free to open some csv, create SA object instances, loop, etc. I usually have my seed data as a series of sql insert statements and just loop over them executing a migate.execute(query) for each one. \nSo I'll first create the table, loop and run seed data, and then empty\/drop table on the downgrade method.","Q_Score":2,"Tags":"python,sqlalchemy,pylons,sqlalchemy-migrate","A_Id":4300116,"CreationDate":"2010-11-28T20:24:00.000","Title":"Managing seed data with SqlAlchemy and SqlAlchemy-migrate","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm learning to use SQLAlchemy connected to a SQL database for 12 standard relational tables (e.g. SQLite or PostgreSQL). But then I'd like to use Redis with Python for a couple of tables, particularly for Redis's fast set manipulation. I realise that Redis is NoSQL, but can I integrate this with SQLAlchemy for the benefit of the session and thread handling that SQLAlchemy has?\nIs there a Redis SA dialect? I couldn't find it, which probably means that I'm missing some basic point. Is there a better architecture I should look at to use two different types of database?","AnswerCount":2,"Available Count":2,"Score":1.0,"is_accepted":false,"ViewCount":13868,"Q_Id":4324407,"Users Score":17,"Answer":"While it is possible to set up an ORM that puts data in redis, it isn't a particularly good idea. ORMs are designed to expose standard SQL features. Many things that are standard in SQL such as querying on arbitrary columns are not available in redis unless you do a lot of extra work. At the same time redis has features such as set manipulation that do not exist in standard SQL so will not be used by the ORM.\nYour best option is probably to write your code to interact directly with redis rather than trying to use an inappropriate abstraction - Generally you will find that the code to get data out of redis is quite a bit simpler than the SQL code that justifies using an ORM.","Q_Score":15,"Tags":"python,sqlalchemy,nosql,redis","A_Id":4331070,"CreationDate":"2010-12-01T12:36:00.000","Title":"How to integrate Redis with SQLAlchemy","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm learning to use SQLAlchemy connected to a SQL database for 12 standard relational tables (e.g. SQLite or PostgreSQL). But then I'd like to use Redis with Python for a couple of tables, particularly for Redis's fast set manipulation. I realise that Redis is NoSQL, but can I integrate this with SQLAlchemy for the benefit of the session and thread handling that SQLAlchemy has?\nIs there a Redis SA dialect? I couldn't find it, which probably means that I'm missing some basic point. Is there a better architecture I should look at to use two different types of database?","AnswerCount":2,"Available Count":2,"Score":1.0,"is_accepted":false,"ViewCount":13868,"Q_Id":4324407,"Users Score":14,"Answer":"Redis is very good at what it does, storing key values and making simple atomic operations, but if you want to use it as a relational database you're really gonna SUFFER!, as I had... and here is my story...\nI've done something like that, making several objects to abstracting all the redis internals exposing primitives queries (I called filters in my code), get, set, updates, and a lot more methods that you can expect from a ORM and in fact if you are dealing only with localhost, you're not going to perceive any slowness in your application, you can use redis as a relational database but if in any time you try to move your database into another host, that will represent a lot of problems in terms of network transmission, I end up with a bunch of re-hacked classes using redis and his pipes, which it make my program like 900% faster, making it usable in the local network, anyway I'm starting to move my database library to postgres.\nThe lesson of this history is to never try to make a relational database with the key value model, works great at basic operations, but the price of not having the possibility to make relations in your server comes with a high cost.\nReturning to your question, I don't know any project to make an adapter to sqlalchemy for redis, and I think that nobody are going to be really interested in something like that, because of the nature of each project.","Q_Score":15,"Tags":"python,sqlalchemy,nosql,redis","A_Id":4332791,"CreationDate":"2010-12-01T12:36:00.000","Title":"How to integrate Redis with SQLAlchemy","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a database full of data, including a date and time string, e.g. Tue, 21 Sep 2010 14:16:17 +0000\nWhat I would like to be able to do is extract various documents (records) from the database based on the time contained within the date string, Tue, 21 Sep 2010 14:16:17 +0000.\nFrom the above date string, how would I use python and regex to extract documents that have the time 15:00:00? I'm using MongoDB by the way, in conjunction with Python.","AnswerCount":4,"Available Count":1,"Score":0.049958375,"is_accepted":false,"ViewCount":563,"Q_Id":4325194,"Users Score":1,"Answer":"I agree with the other poster. Though this doesn't solve your immediate problem, if you have any control over the database, you should seriously consider creating a time\/column, with either a DATE or TIMESTAMP datatype. That would make your system much more robust, & completely avoid the problem of trying to parse dates from string (an inherently fragile technique).","Q_Score":3,"Tags":"python,regex,mongodb,datetime,database","A_Id":4325260,"CreationDate":"2010-12-01T14:10:00.000","Title":"Extracting Date and Time info from a string.","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am implementing a database model to store the 20+ fields of the iCal calendar format and am faced with tediously typing in all these into an SQLAlchemy model.py file.  Is there a smarter approach?  I am looking for a GUI or model designer that can create the model.py file for me.  I would specify the column names and some attributes, e.g, type, length, etc.\nAt the minimum, I need this designer to output a model for one table.  Additional requirements, in decreasing order of priority:\n\nCreate multiple tables\nSupport basic relationships between the multiple tables (1:1, 1:n)\nSupport constraints on the columns.\n\nI am also open to other ways of achieving the goal, perhaps using a GUI to create the tables in the database and then reflecting them back into a model.\nI appreciate your feedback in advance.","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":2698,"Q_Id":4330339,"Users Score":0,"Answer":"\"I would specify the column names and some attributes, e.g, type, length, etc.\"\nIsn't that the exact same thing as \n\"tediously typing in all these into an SQLAlchemy model.py file\"?\nIf those two things aren't identical, please explain how they're different.","Q_Score":5,"Tags":"python,model,sqlalchemy,data-modeling","A_Id":4330995,"CreationDate":"2010-12-01T23:52:00.000","Title":"Is there any database model designer that can output SQLAlchemy models?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I just downloaded sqlite3.exe. It opens up as a command prompt. I created a table test & inserted a few entries in it. I used .backup test just in case. After I exit the program using .exit and reopened it I don't find the table listed under .tables nor can I run any query on it.\nI need to quickly run an open source python program that makes use of this table & although I have worked with MySQL, I have no clue about sqlite. I need the minimal basics of sqlite. Can someone guide me through this or at least tell me how to permanently store my tables.\nI have put this sqlite3.exe in Python folder assuming that python would then be able to read the sqlite files. Any ideas on this?","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":2598,"Q_Id":4348658,"Users Score":0,"Answer":"Just execute sqlite3 foo.db? This will permanently store everything you do afterwards in this file. (No need for .backup.)","Q_Score":0,"Tags":"python,sqlite","A_Id":4348768,"CreationDate":"2010-12-03T18:30:00.000","Title":"How to create tables in sqlite 3?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have some (Excel 2000) workbooks. I want to extract the data in each worksheet to a separate file.\nI am running on Linux.\nIs there a library I can use to access (read) XLS files on Linux from Python?","AnswerCount":4,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":2104,"Q_Id":4355435,"Users Score":0,"Answer":"The easiest way would be to run excel up under Wine or as a VM and do it from Windows.  You can use Mark Hammond's COM bindings, which come bundled with ActiveState Python.  Alternatively, you could export the data in CSV format and read it from that.","Q_Score":3,"Tags":"python,excel","A_Id":4355455,"CreationDate":"2010-12-04T19:41:00.000","Title":"Cross platform way to read Excel files in Python?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"With the rise of NoSQL, is it more common these days to have a webapp without any model and process everything in the controller? Is this a bad pattern in web development? Why should we abstract our database related function in a model when it is easy enough to fetch the data in nosql?\nNote\nI am not asking whether RDBMS\/SQL is not relevant because that will only start flamewar.","AnswerCount":3,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":210,"Q_Id":4355909,"Users Score":0,"Answer":"The NoSQL effort has to do with creating a persistence layer that scales with modern applications using non-normalized data structures for fast reads & writes and data formats like JSON, the standard format used by ajax based systems. It is sometimes the case that transaction based relational databases do not scale well, but more often than not poor performance is directly related to poor data modeling, poor query creation and poor planning.\nNo persistence layer should have anything to do with your domain model. Using a data abstraction layer, you transform the data contained in your objects to the schema implemented in your data store. You would then use the same DAL to read data from your data store, transform and load it into your objects.\nYour data store could be XML files, an RDBMS like SQL Server or a NoSQL implementation like CouchDB. It doesn't matter.\nFWIW, I've built and inherited plenty of applications that used no model at all. For some, there's no need, but if you're using an object model it has to fit the needs of the application, not the data store and not the presentation layer.","Q_Score":0,"Tags":"python,mysql,ruby-on-rails,nosql","A_Id":4357332,"CreationDate":"2010-12-04T21:24:00.000","Title":"With the rise of NoSQL, Is it more common these days to have a webapp without any model?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"With the rise of NoSQL, is it more common these days to have a webapp without any model and process everything in the controller? Is this a bad pattern in web development? Why should we abstract our database related function in a model when it is easy enough to fetch the data in nosql?\nNote\nI am not asking whether RDBMS\/SQL is not relevant because that will only start flamewar.","AnswerCount":3,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":210,"Q_Id":4355909,"Users Score":0,"Answer":"SQL databases are still the order of the day. But it's becoming more common to use unstructured stores. NoSQL databases are well suited for some web apps, but not necessarily all of them.","Q_Score":0,"Tags":"python,mysql,ruby-on-rails,nosql","A_Id":4355924,"CreationDate":"2010-12-04T21:24:00.000","Title":"With the rise of NoSQL, Is it more common these days to have a webapp without any model?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"With the rise of NoSQL, is it more common these days to have a webapp without any model and process everything in the controller? Is this a bad pattern in web development? Why should we abstract our database related function in a model when it is easy enough to fetch the data in nosql?\nNote\nI am not asking whether RDBMS\/SQL is not relevant because that will only start flamewar.","AnswerCount":3,"Available Count":3,"Score":1.2,"is_accepted":true,"ViewCount":210,"Q_Id":4355909,"Users Score":4,"Answer":"I don't think \"NoSQL\" has anything to do with \"no model\".\nFor one, MVC originated in the Smalltalk world for desktop applications, long before the current web server architecture (or even the web itself) existed.  Most apps I've written have used MVC (including the M), even those that didn't use a DBMS (R or otherwise).\nFor another, some kinds of \"NoSQL\" explicitly have a model.  An object database might look, to the application code, almost just like the interface that your \"SQL RDBMS + ORM\" are trying to expose, but without all the weird quirks and explicit mapping and so on.\nFinally, you can obviously go the other way, and write SQL-based apps with no model.  It may not be pretty, but I've seen it done.","Q_Score":0,"Tags":"python,mysql,ruby-on-rails,nosql","A_Id":4355976,"CreationDate":"2010-12-04T21:24:00.000","Title":"With the rise of NoSQL, Is it more common these days to have a webapp without any model?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"When committing data that has originally come from a webpage, sometimes data has to be converted to a data type or format which is suitable for the back-end database.  For instance, a date in 'dd\/mm\/yyyy' format needs to be converted to a Python date-object or 'yyyy-mm-dd' in order to be stored in a SQLite date column (SQLite will accept 'dd\/mm\/yyyy', but that can cause problems when data is retrieved).\nQuestion - at what point should the data be converted?\n    a) As part of a generic web_page_save() method (immediately after data validation, but before a row.table_update() method is called).\n    b) As part of row.table_update() (a data-object method called from web- or non-web-based applications, and includes construction of a field-value parameter list prior to executing the UPDATE command).\nIn other words, from a framework point-of-view, does the data-conversion belong to page-object processing or data-object processing?\nAny opinions would be appreciated.\nAlan","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":75,"Q_Id":4360407,"Users Score":1,"Answer":"I could be wrong, but I think there is no definite answer to this question. It depends on \"language\" level your framework provides. For example, if another parts of the framework accept data in non-canonical form and then convert it to an internal canonical form, it this case it would worth to support some input date formats that are expected.\nI always prefer to build strict frameworks and convert data in front-ends.","Q_Score":0,"Tags":"python,sqlite","A_Id":4360475,"CreationDate":"2010-12-05T18:24:00.000","Title":"Framework design question","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"When committing data that has originally come from a webpage, sometimes data has to be converted to a data type or format which is suitable for the back-end database.  For instance, a date in 'dd\/mm\/yyyy' format needs to be converted to a Python date-object or 'yyyy-mm-dd' in order to be stored in a SQLite date column (SQLite will accept 'dd\/mm\/yyyy', but that can cause problems when data is retrieved).\nQuestion - at what point should the data be converted?\n    a) As part of a generic web_page_save() method (immediately after data validation, but before a row.table_update() method is called).\n    b) As part of row.table_update() (a data-object method called from web- or non-web-based applications, and includes construction of a field-value parameter list prior to executing the UPDATE command).\nIn other words, from a framework point-of-view, does the data-conversion belong to page-object processing or data-object processing?\nAny opinions would be appreciated.\nAlan","AnswerCount":2,"Available Count":2,"Score":0.1973753202,"is_accepted":false,"ViewCount":75,"Q_Id":4360407,"Users Score":2,"Answer":"I think it belongs in the validation. You want a date, but the web page inputs strings only, so the validator needs to check if the value van be converted to a date, and from that point on your application should process it like a date.","Q_Score":0,"Tags":"python,sqlite","A_Id":4360452,"CreationDate":"2010-12-05T18:24:00.000","Title":"Framework design question","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Which one of Ruby-PHP-Python is best suited for Cassandra\/Hadoop on 500M+ users?  I know language itself is not a big concern but I like to know base on proven success, infrastructure and available utilities around those frameworks! thanks so much.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":339,"Q_Id":4398341,"Users Score":0,"Answer":"Because Cassandra is written in Java, a client also in Java would likely have the best stability and maturity for your application.\nAs far as choosing between those 3 dynamic languages, I'd say whatever you're most comfortable with is best.  I don't know of any significant differences between client libraries in those languages.","Q_Score":0,"Tags":"php,python,ruby-on-rails,scalability,cassandra","A_Id":9921879,"CreationDate":"2010-12-09T12:46:00.000","Title":"Scability of Ruby-PHP-Python on Cassandra\/Hadoop on 500M+ users","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"The question pretty much says it all.  The database is in MySQL using phpMyAdmin.  \nA little background: I'm writing the interface for a small non-profit organization.  They need to be able to see which customers to ship to this month, which customers have recurring orders, etc.  The current system is ancient, written in PHP 4, and I'm in charge of upgrading it.  I spoke with the creator of the current system, and he agreed that it would be better to just write a new interface.\nI'm new to Python, SQL and PHP, so this is a big learning opportunity for me.  I'm pretty excited.  I do have a lot of programming experience though (C, Java, Objective-C), and I don't anticipate any problems picking up Python.\nSo here I am!\nThanks in advance for all your help.","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":186,"Q_Id":4413840,"Users Score":0,"Answer":"What can I say? Just download the various software, dig in and ask questions here when you run into specific problems.","Q_Score":0,"Tags":"php,python,mysql,phpmyadmin","A_Id":4413898,"CreationDate":"2010-12-10T22:23:00.000","Title":"I have a MySQL database, I want to write an interface for it using Python. Help me get started, please!","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am writing a Python logger script which writes to a CSV file in the following manner:\n\nOpen the file\nAppend data\nClose the file (I think this is necessary to save the changes, to be safe after every logging routine.)\n\nPROBLEM:\nThe file is very much accessible through Windows Explorer (I'm using XP). If the file is opened in Excel, access to it is locked by Excel. When the script tries to append data, obviously it fails, then it aborts altogether.\nOBJECTIVE:\nIs there a way to lock a file using Python so that any access to it remains exclusive to the script? Or perhaps my methodology is poor in the first place?","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":2562,"Q_Id":4427936,"Users Score":0,"Answer":"As far as I know, Windows does not support file locking. In other words, applications that don't know about your file being locked can't be prevented from reading a file.\nBut the remaining question is: how can Excel accomplish this?\nYou might want to try to write to a temporary file first (one that Excel does not know about) and replace the original file by it lateron.","Q_Score":1,"Tags":"python,logging,file-locking","A_Id":4427958,"CreationDate":"2010-12-13T10:36:00.000","Title":"Prevent a file from being opened","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Many times while creating database structure, I get stuck at the question, what would be more effective, storing data in pickled format in a column in the same table or create additional table and then use JOIN.\nWhich path should be followed, any advice ?\nFor example:\nThere is a table of Customers, containing fields like Name, Address\nNow for managing Orders (each customer can have many), you can either create an Order table or store the orders in a serialized format in a separate column in the Customers table only.","AnswerCount":5,"Available Count":4,"Score":0.0399786803,"is_accepted":false,"ViewCount":159,"Q_Id":4428613,"Users Score":1,"Answer":"I agree with Mchi, there is no problem storing \"pickled\" data if you don't need to search or do relational type operations.\nDenormalisation is also an important tool that can scale up database performance when applied correctly.\nIt's probably a better idea to use JSON instead of pickles. It only uses a little more space, and makes it possible to use the database from languages other than Python","Q_Score":2,"Tags":"python,mysql","A_Id":4428933,"CreationDate":"2010-12-13T12:04:00.000","Title":"Is it a good practice to use pickled data instead of additional tables?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Many times while creating database structure, I get stuck at the question, what would be more effective, storing data in pickled format in a column in the same table or create additional table and then use JOIN.\nWhich path should be followed, any advice ?\nFor example:\nThere is a table of Customers, containing fields like Name, Address\nNow for managing Orders (each customer can have many), you can either create an Order table or store the orders in a serialized format in a separate column in the Customers table only.","AnswerCount":5,"Available Count":4,"Score":1.2,"is_accepted":true,"ViewCount":159,"Q_Id":4428613,"Users Score":2,"Answer":"Mixing SQL databases and pickling seems to ask for trouble. I'd go with either sticking all data in the SQL databases or using only pickling, in the form of the ZODB, which is a Python only OO database that is pretty damn awesome. \nMixing makes case sometimes, but is usually just more trouble than it's worth.","Q_Score":2,"Tags":"python,mysql","A_Id":4429509,"CreationDate":"2010-12-13T12:04:00.000","Title":"Is it a good practice to use pickled data instead of additional tables?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Many times while creating database structure, I get stuck at the question, what would be more effective, storing data in pickled format in a column in the same table or create additional table and then use JOIN.\nWhich path should be followed, any advice ?\nFor example:\nThere is a table of Customers, containing fields like Name, Address\nNow for managing Orders (each customer can have many), you can either create an Order table or store the orders in a serialized format in a separate column in the Customers table only.","AnswerCount":5,"Available Count":4,"Score":0.0,"is_accepted":false,"ViewCount":159,"Q_Id":4428613,"Users Score":0,"Answer":"I agree with @Lennart Regebro. You should probably see whether you need a Relational DB or an OODB. If RDBMS is your choice, I would suggest you stick with more tables. IMHO, pickling may have issues with scalability. If thats what you want, you should look at ZODB. It is pretty good and supports caching etc for better performance","Q_Score":2,"Tags":"python,mysql","A_Id":4432349,"CreationDate":"2010-12-13T12:04:00.000","Title":"Is it a good practice to use pickled data instead of additional tables?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Many times while creating database structure, I get stuck at the question, what would be more effective, storing data in pickled format in a column in the same table or create additional table and then use JOIN.\nWhich path should be followed, any advice ?\nFor example:\nThere is a table of Customers, containing fields like Name, Address\nNow for managing Orders (each customer can have many), you can either create an Order table or store the orders in a serialized format in a separate column in the Customers table only.","AnswerCount":5,"Available Count":4,"Score":0.1194272985,"is_accepted":false,"ViewCount":159,"Q_Id":4428613,"Users Score":3,"Answer":"Usually it's best to keep your data normalized (i.e. create more tables). Storing data 'pickled' as you say, is acceptable, when you don't need to perform relational operations on them.","Q_Score":2,"Tags":"python,mysql","A_Id":4428635,"CreationDate":"2010-12-13T12:04:00.000","Title":"Is it a good practice to use pickled data instead of additional tables?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I would like to be able to plot a call graph of a stored procedure. I am not interested in every detail, and I am not concerned with dynamic SQL (although it would be cool to detect it and skip it maybe or mark it as such.)\nI would like the tool to generate a tree for me, given the server name, db name, stored proc name, a \"call tree\", which includes:\n\nParent stored procedure.\nEvery other stored procedure that is being called as a child of the caller.\nEvery table that is being modified (updated or deleted from) as a child of the stored proc which does it.\n\nHopefully it is clear what I am after; if not - please do ask. If there is not a tool that can do this, then I would like to try to write one myself. Python 2.6 is my language of choice, and I would like to use standard libraries as much as possible. Any suggestions?\nEDIT: For the purposes of bounty Warning: SQL syntax is COMPLEX. I need something that can parse all kinds of SQL 2008, even if it looks stupid. No corner cases barred :)\nEDIT2: I would be OK if all I am missing is graphics.","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":6375,"Q_Id":4445117,"Users Score":0,"Answer":"SQL Negotiator Pro has a free lite version at www.aphilen.com\nThe full version is the only product out there that will find all dependencies and not stop after finding the first 10 child dependencies. Other products fail when there is a circular reference and just hang, these guys have covered this off. Also a neat feature is the ability to add notes to the diagram so that it can be easily distributed.\nFull version is not cheap but has saved us plenty of hours usually required figuring out complex database procedures. apex also provide a neat tool","Q_Score":8,"Tags":"sql-server-2008,stored-procedures,python-2.6,call-graph","A_Id":18523367,"CreationDate":"2010-12-14T22:54:00.000","Title":"Is there a free tool which can help visualize the logic of a stored procedure in SQL Server 2008 R2?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I create hangman game with silverlight ironpython and I use data in postgresql for random word but I don't know to access data in postgresql in silverlight.\nhow can or should it be done?\nThanks!!","AnswerCount":1,"Available Count":1,"Score":0.537049567,"is_accepted":false,"ViewCount":950,"Q_Id":4470073,"Users Score":3,"Answer":"From Silverlight you cannot access a database directly (remember it's a web technology that actually runs locally on the client and the client cannot access your database directly over the internet). \nTo communicate with the server from Silverlight, you must create a separated WebService either with SOAP, WCF or RIA Services for example.  \nThat Webservice will expose your data on the web.  Call the WebService method to get your data from your Silverlight program.\nThis WebService layer will be your middle tiers that actually makes the bridge between your postgresql database and your Silverlight application.","Q_Score":0,"Tags":"silverlight,postgresql,silverlight-4.0,silverlight-3.0,ironpython","A_Id":4470466,"CreationDate":"2010-12-17T11:37:00.000","Title":"How to access PostgreSQL with Silverlight","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I need to implement a function that takes a lambda as the argument and queries the database. I use SQLAlchemy for ORM. Is there a way to pass the lambda, that my function receives, to SQLAlchemy to create a query?\nSincerely,\nRoman Prykhodchenko","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1681,"Q_Id":4470481,"Users Score":2,"Answer":"I guess you want to filter the data with the lambda, like a WHERE clause? Well, no, functions nor lambdas cannot be turned into a SQL query. Sure, you could just fetch all the data and filter it in Python, but that completely defeats the purpose of the database.\nYou'll need to recreate the logic you put into the lambda with SQLAlchemy.","Q_Score":2,"Tags":"python,sqlalchemy","A_Id":4470921,"CreationDate":"2010-12-17T12:33:00.000","Title":"Can I use lambda to create a query in SQLAlchemy?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"The desire is to have the user provide information in an OpenOffice Writer or MS Word file that is inserted into part of a ReportLab generated PDF. I am comfortable with ReportLab; but, I don't have any experience with using Writer or Word data in this way. How would you automate the process of pulling in the Writer\/Word data? Is it possible to retain tables and graphs?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":147,"Q_Id":4478478,"Users Score":0,"Answer":"You can not embed such objects as is within a PDF, adobe specification does not support that. However you could always parse the data from the Office document and reproduce it as a table\/graph\/etc using reportlab in the output PDF. If you don't care about the data being an actual text you could always save it in the PDF as an image.","Q_Score":1,"Tags":"python,ms-word,reportlab,openoffice-writer","A_Id":4691989,"CreationDate":"2010-12-18T14:36:00.000","Title":"Is it possible to include OpenOffice Writer or MS Word data in a ReportLab generated PDF?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am developing an application for managers that might be used in a large organisation. The app is improved and extended step by step on a frequent (irregular) basis. The app will have SQL connections to several databases and has a complex GUI.\nWhat would you advise to deploy the app ?\nBased on my current (limited) knowledge of apps in lager organisations I prefer a setup where the app runs on a server and the user uses a thin client via the web. I prefer not to use a webbrowser because of (possible)limitations of the user GUI. The user experience should be as if the app was running on his own laptop\/pc\/tablet(?)\nWhat opensource solution would you advise ?\nThanks !","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":318,"Q_Id":4485404,"Users Score":1,"Answer":"If possible, make the application run without any installation procedure, and provide it on a network share (e.g. with a fixed UNC path). You didn't specify the client operating system: if it's Windows, create an MSI that sets up something in the start menu that will still make the application launch from the network share.\nWith that approach, updates will be as simple as replacing the files on the file server - yet it will always run on the client.","Q_Score":1,"Tags":"python,client-server,rich-internet-application","A_Id":4485440,"CreationDate":"2010-12-19T22:13:00.000","Title":"Deploy python application","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Okay, so what I want to do is upload an excel sheet and display it on my website, in html. What are my options here ? I've found this xlrd module that allows you to read the data from spreadsheets, but I don't really need that right now.","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1961,"Q_Id":4498678,"Users Score":4,"Answer":"Why don't you need xlrd? It sounds like exactly what you need. \nCreate a Django model with a FileField that holds the spreadsheet. Then your view uses xlrd to loop over the rows and columns and put them into an HTML table. Job done.\nPossible complications: multiple sheets in one Excel file; formulas; styles.","Q_Score":1,"Tags":"python,html,django,excel","A_Id":4499265,"CreationDate":"2010-12-21T11:20:00.000","Title":"Python\/Django excel to html","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a CSV file which is about 1GB big and contains about 50million rows of data, I am wondering is it better to keep it as a CSV file or store it as some form of a database. I don't know a great deal about MySQL to argue for why I should use it or another database framework over just keeping it as a CSV file. I am basically doing a Breadth-First Search with this dataset, so once I get the initial \"seed\" set the 50million I use this as the first values in my queue.\nThanks,","AnswerCount":5,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":1161,"Q_Id":4505170,"Users Score":0,"Answer":"How about some key-value storages like MongoDB","Q_Score":2,"Tags":"python,mysql,database,optimization,csv","A_Id":4505300,"CreationDate":"2010-12-22T00:20:00.000","Title":"50 million+ Rows of Data - CSV or MySQL","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a CSV file which is about 1GB big and contains about 50million rows of data, I am wondering is it better to keep it as a CSV file or store it as some form of a database. I don't know a great deal about MySQL to argue for why I should use it or another database framework over just keeping it as a CSV file. I am basically doing a Breadth-First Search with this dataset, so once I get the initial \"seed\" set the 50million I use this as the first values in my queue.\nThanks,","AnswerCount":5,"Available Count":3,"Score":1.2,"is_accepted":true,"ViewCount":1161,"Q_Id":4505170,"Users Score":3,"Answer":"I would say that there are a wide variety of benefits to using a database over a CSV for such large structured data so I would suggest that you learn enough to do so. However, based on your description you might want to check out non-server\/lighter weight databases. Such as SQLite, or something similar to JavaDB\/Derby... or depending on the structure of your data a non-relational (Nosql) database- obviously you will need one with some type of python support though.","Q_Score":2,"Tags":"python,mysql,database,optimization,csv","A_Id":4505218,"CreationDate":"2010-12-22T00:20:00.000","Title":"50 million+ Rows of Data - CSV or MySQL","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a CSV file which is about 1GB big and contains about 50million rows of data, I am wondering is it better to keep it as a CSV file or store it as some form of a database. I don't know a great deal about MySQL to argue for why I should use it or another database framework over just keeping it as a CSV file. I am basically doing a Breadth-First Search with this dataset, so once I get the initial \"seed\" set the 50million I use this as the first values in my queue.\nThanks,","AnswerCount":5,"Available Count":3,"Score":0.0399786803,"is_accepted":false,"ViewCount":1161,"Q_Id":4505170,"Users Score":1,"Answer":"Are you just going to slurp in everything all at once? If so, then CSV is probably the way to go. It's simple and works.\nIf you need to do lookups, then something that lets you index the data, like MySQL, would be better.","Q_Score":2,"Tags":"python,mysql,database,optimization,csv","A_Id":4505180,"CreationDate":"2010-12-22T00:20:00.000","Title":"50 million+ Rows of Data - CSV or MySQL","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm looking to write a small web app to utilise a dataset I already have stored in a MongoDB collection. I've been writing more Python than other languages lately and would like to broaden my repertoire and write a Python web app. \nIt seems however that most if not all of the current popular Python web development frameworks favour MySQL and others with no mention given to MongoDB. \nI am aware that there are more than likely plugins written to allow Mongo be used with existing frameworks but so far have found little as to documentation that compares and contrasts them. \nI was wondering what in people's experience is the Python web development framework with the best MongoDB support?\nMany thanks in advance,\nPatrick","AnswerCount":4,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":9196,"Q_Id":4534684,"Users Score":0,"Answer":"There is no stable support for mongodb using django framework. I tried using mongoengine, but unlike models, provided for admin in django framework, there is no support for mongoengine.\nCorrect if I am wrong.","Q_Score":17,"Tags":"python,mongodb","A_Id":50201839,"CreationDate":"2010-12-26T17:14:00.000","Title":"Python Web Framework with best Mongo support","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm new to MySQL, and I have a question about the memory. \nI have a 200mb table(MyISAM, 2,000,000 rows), and I try to load all of it to the \nmemory. \nI use python(actually MySQLdb in python) with sql: SELECT * FROM table. \nHowever, from my linux \"top\" I saw this python process uses 50% of my memory(which is total 6GB) \nI'm curious about why it uses about 3GB memory only for a 200 mb table. \nThanks in advance!","AnswerCount":4,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":4116,"Q_Id":4559402,"Users Score":0,"Answer":"In pretty much any scripting language, a variable will always take up more memory than its actual contents would suggest. An INT might be 32 or 64bits, suggesting it would require 4 or 8 bytes of memory, but it will take up 16 or 32bytes (pulling numbers out of my hat), because the language interpreter has to attach various metadata to that value along the way.\nThe database might only require 200megabytes of raw storage space, but once you factor in the metadata, it will definitely occupy much much more.","Q_Score":1,"Tags":"python,mysql","A_Id":4559691,"CreationDate":"2010-12-30T01:47:00.000","Title":"the Memory problem about MySQL \"SELECT *\"","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm new to MySQL, and I have a question about the memory. \nI have a 200mb table(MyISAM, 2,000,000 rows), and I try to load all of it to the \nmemory. \nI use python(actually MySQLdb in python) with sql: SELECT * FROM table. \nHowever, from my linux \"top\" I saw this python process uses 50% of my memory(which is total 6GB) \nI'm curious about why it uses about 3GB memory only for a 200 mb table. \nThanks in advance!","AnswerCount":4,"Available Count":2,"Score":-0.049958375,"is_accepted":false,"ViewCount":4116,"Q_Id":4559402,"Users Score":-1,"Answer":"This is almost certainly a bad design.\nWhat are you doing with all that data in memory at once?  \nIf it's for one user, why not pare the size down so you can support multiple users?\nIf you're doing a calculation on the middle tier, is it possible to shift the work to the database server so you don't have to bring all the data into memory?\nYou know you can do this, but the larger questions are (1) why? and (2) what else could you do?  We'd need more context to answer these.","Q_Score":1,"Tags":"python,mysql","A_Id":4559443,"CreationDate":"2010-12-30T01:47:00.000","Title":"the Memory problem about MySQL \"SELECT *\"","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"How can I update multiple records in a queryset efficiently? \nDo I just loop over the queryset, edit , and call save() for each one of them? Is it equivalent to psycopg2's executemany?","AnswerCount":3,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":6395,"Q_Id":4600938,"Users Score":6,"Answer":"If you have to update each record with a different value, then of couse you have to iterate over each record. If you wish to do update them all with the same value, then just use the update method of the queryset.","Q_Score":1,"Tags":"python,django","A_Id":4601203,"CreationDate":"2011-01-05T04:53:00.000","Title":"Django: how can I update more than one record at once?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a project coming up that involves a desktop application (tournament scoring for an amateur competition) that probably 99+% of the time will be a single-user on a single machine, no network connectivity, etc.  For that, sqlite will likely work beautifully.  For those other few times when there are more than one person, with more than one computer, and some form of network... they would ideally need to be able to enter data (event registration and putting in scores) to a central database such as a MySQL or PostgreSQL server.  I don't envision a need for synchronizing data between the local (sqlite) and remote databases, just a need to be able to switch via preferences or configuration file which kind of database the program should connect to the next time its started (along with the connection info for any remote database).\nI'm fairly new at this kind of programming, and this will likely take me a good while to get where I want it... but I'd prefer to avoid going down the wrong path early on (at least on major things like this).  Given my limited understanding of things like ORMs it seems like this would be a near-ideal use for something like SQLAlchemy, no?  Or would the 'batteries included' python db-api be generic enough for this kind of task?\nTIA,\nMonte","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":245,"Q_Id":4610698,"Users Score":1,"Answer":"Yes, SQLAlchemy will help you to be independent on what SQL database you use, and you get a nice ORM as well. Highly recommended.","Q_Score":2,"Tags":"python,database,sqlite,orm,sqlalchemy","A_Id":4612684,"CreationDate":"2011-01-06T00:31:00.000","Title":"creating a database-neutral app in python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a project coming up that involves a desktop application (tournament scoring for an amateur competition) that probably 99+% of the time will be a single-user on a single machine, no network connectivity, etc.  For that, sqlite will likely work beautifully.  For those other few times when there are more than one person, with more than one computer, and some form of network... they would ideally need to be able to enter data (event registration and putting in scores) to a central database such as a MySQL or PostgreSQL server.  I don't envision a need for synchronizing data between the local (sqlite) and remote databases, just a need to be able to switch via preferences or configuration file which kind of database the program should connect to the next time its started (along with the connection info for any remote database).\nI'm fairly new at this kind of programming, and this will likely take me a good while to get where I want it... but I'd prefer to avoid going down the wrong path early on (at least on major things like this).  Given my limited understanding of things like ORMs it seems like this would be a near-ideal use for something like SQLAlchemy, no?  Or would the 'batteries included' python db-api be generic enough for this kind of task?\nTIA,\nMonte","AnswerCount":2,"Available Count":2,"Score":-0.0996679946,"is_accepted":false,"ViewCount":245,"Q_Id":4610698,"Users Score":-1,"Answer":"I don't see how those 2 use cases would use the same methods. Just create a wrapper module that conditionally imports either the sqlite or sqlalchemy modules or whatever else you need.","Q_Score":2,"Tags":"python,database,sqlite,orm,sqlalchemy","A_Id":4610735,"CreationDate":"2011-01-06T00:31:00.000","Title":"creating a database-neutral app in python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm developing a web app that uses stock data. The stock data can be stored in:\n\nFiles \nDB\n\nThe structure of the data is simple: there's a daily set and a weekly set. If files are used, then I can store a file per symbol\/set, such as GOOGLE_DAILY and GOOGLE_WEEKLY. Each set includes a simple list of (Date, open\/hight\/low\/close, volume, dividend) fields.\nBut how can I do it with DB? Should I use relational or other db? I thought about using 2 tables per each symbol, but that would generate thousands of tables, which doesn't feel right.\nThanks.","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":81,"Q_Id":4613251,"Users Score":3,"Answer":"You don't need a table per stock symbol, you just need one of the fields in the table to be the stock symbol. The table might be called StockPrices and its fields might be\n\nticker_symbol - the stock ticker symbol\ntime - the time of the stock quote\nprice - the price of the stock at that time\n\nAs long as ticker_symbol is an indexed field you can do powerful queries like SELECT time,price FROM StockPrices WHERE ticker_symbol='GOOG' ORDER BY time DESC and they will be very efficient. You can also store as many symbols as you like in this table.\nYou could add other tables for dividends, volume information and such. In all cases you probably have a composite key of ticker_symbol and time.","Q_Score":0,"Tags":"python,django,data-structures","A_Id":4613300,"CreationDate":"2011-01-06T09:02:00.000","Title":"Help needed with db structure","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Im setting a VM. \nBoth host and VM machine have Mysql. \nHow do keep the VM Mysql sync'd to to the host Mysql. \nHost is using MYsql 5.5 on XP.\nVM is Mysql 5.1 on Fedora 14. \n1) I could DUMP to \"shared,\" Restore. Not sure if this will work.\n2) I could network Mysql Host to Mysql VM. Not how to do this \nHow would I do this with python 2.7?   \nI dont want them in sync after set-up phase. But, maybe sync some tables or SP occasionly on-rewrites. After I build out Linux Env. I would like to be able to convert V2P and have a dual-boot system.","AnswerCount":3,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":2319,"Q_Id":4619392,"Users Score":0,"Answer":"Do you want it synced in realtime?\nWhy not just connect the guest's mysql process to the host?","Q_Score":1,"Tags":"python,mysql,virtual-machine","A_Id":4621472,"CreationDate":"2011-01-06T20:15:00.000","Title":"How to Sync MySQL with python?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Im setting a VM. \nBoth host and VM machine have Mysql. \nHow do keep the VM Mysql sync'd to to the host Mysql. \nHost is using MYsql 5.5 on XP.\nVM is Mysql 5.1 on Fedora 14. \n1) I could DUMP to \"shared,\" Restore. Not sure if this will work.\n2) I could network Mysql Host to Mysql VM. Not how to do this \nHow would I do this with python 2.7?   \nI dont want them in sync after set-up phase. But, maybe sync some tables or SP occasionly on-rewrites. After I build out Linux Env. I would like to be able to convert V2P and have a dual-boot system.","AnswerCount":3,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":2319,"Q_Id":4619392,"Users Score":1,"Answer":"You can use mysqldump to make snapshots of the database, and to restore it to known states after tests. \nBut instead or going into the complication of synchronizing different database instances, it would be best to open the host machine's instance to local network access, and have the applications in the virtual machine access that as if it was a remote server. Overall performance should improve too. \nEven if you decide to run different databases for the host and the guest, run then both on the host's MySQL instance. Performance will be better, configuration management will be easier, and the apps in the guest will be tested against a realistic deployment environment.","Q_Score":1,"Tags":"python,mysql,virtual-machine","A_Id":4619503,"CreationDate":"2011-01-06T20:15:00.000","Title":"How to Sync MySQL with python?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I know of PyMySQLDb, is that pretty much the thinnest\/lightest way of accessing MySql?","AnswerCount":3,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":2598,"Q_Id":4620340,"Users Score":0,"Answer":"MySQLDb is faster while SQLAlchemy makes code more user friendly -:)","Q_Score":2,"Tags":"python,mysql","A_Id":9090731,"CreationDate":"2011-01-06T21:56:00.000","Title":"What is the fastest\/most performant SQL driver for Python?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I know of PyMySQLDb, is that pretty much the thinnest\/lightest way of accessing MySql?","AnswerCount":3,"Available Count":3,"Score":0.3215127375,"is_accepted":false,"ViewCount":2598,"Q_Id":4620340,"Users Score":5,"Answer":"The fastest is SQLAlchemy. \n\"Say what!?\"\nWell, a nice ORM, and I like SQLAlchemy, you will get your code finished much faster. If your code then runs 0.2 seconds slower isn't really gonna make any noticeable difference. :)\nNow if you get performance problems, then you can look into improving the code. But choosing the access module after who in theory is \"fastest\" is premature optimization.","Q_Score":2,"Tags":"python,mysql","A_Id":4620669,"CreationDate":"2011-01-06T21:56:00.000","Title":"What is the fastest\/most performant SQL driver for Python?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I know of PyMySQLDb, is that pretty much the thinnest\/lightest way of accessing MySql?","AnswerCount":3,"Available Count":3,"Score":0.1973753202,"is_accepted":false,"ViewCount":2598,"Q_Id":4620340,"Users Score":3,"Answer":"The lightest possible way is to use ctypes and directly call into the MySQL API, of course, without using any translation layers. Now, that's ugly and will make your life miserable unless you also write C, so yes, the MySQLDb extension is the standard and most performant way to use MySQL while still using the Python Database API. Almost anything else will be built on top of that or one of its predecessors.\nOf course, the connection layer is rarely where all of the database speed problems come from. That's mostly from misusing the API you have or building a bad database or queries.","Q_Score":2,"Tags":"python,mysql","A_Id":4620433,"CreationDate":"2011-01-06T21:56:00.000","Title":"What is the fastest\/most performant SQL driver for Python?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I work with Oracle Database and lastest Django but when i use the default user model is the query very slow\nwhat can i do?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":305,"Q_Id":4625835,"Users Score":2,"Answer":"The solution was to add an index.","Q_Score":2,"Tags":"python,django,oracle,django-models,model","A_Id":6583775,"CreationDate":"2011-01-07T13:18:00.000","Title":"how can i optimize a django oracle connection?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I know that with an InnoDB table, transactions are autocommit, however I understand that to mean for a single statement? For example, I want to check if a user exists in a table, and then if it doesn't, create it. However there lies a race condition. I believe using a transaction prior to doing the select, will ensure that the table remains untouched until the subsequent insert, and the transaction is committed. How can you do this with MySQLdb and Python?","AnswerCount":2,"Available Count":1,"Score":0.3799489623,"is_accepted":false,"ViewCount":363,"Q_Id":4637886,"Users Score":4,"Answer":"There exists a SELECT ... FOR UPDATE that allows you to lock the rows from being read by another transaction but I believe the records have to exist in the first place. Then you can do as you say, and unlock it once you commit. \nIn your case I think the best approach is to simply set a unique constraint on the username and try to insert. If you get a key exception you can notify the user that the name was already taken.","Q_Score":2,"Tags":"python,mysql","A_Id":4656098,"CreationDate":"2011-01-09T05:47:00.000","Title":"How do you create a transaction that spans multiple statements in Python with MySQLdb?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"i have a django project with a long running (~3hour) management command\nin my production environment ( apache mod_wsgi ) this process fails with a broken pipe(32) at the end, when trying to update the database.\nthank you","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":571,"Q_Id":4644317,"Users Score":1,"Answer":"The broken pipe mostly mean that one socket in the canal of transmission has been closed without notifying the other one , in your case i think it mean that the database connection that you have establish was closed from the database part, so when you code try to use it, it raise the exception.\nUsually the database connection has a time out which \"usually\" you can configure by making it more bigger to solve this kind of problem , check your database documentation to see how.\nN.B: you don't give us much detail so i'm just trying to make assumption here.\nWell hope this can help.","Q_Score":1,"Tags":"python,django,apache,mod-wsgi","A_Id":4644443,"CreationDate":"2011-01-10T06:42:00.000","Title":"django long running process database connection","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a medium size (~100mb) read-only database that I want to put on google app engine. I  could put it into the datastore, but the datastore is kind of slow, has no relational features, and has many other frustrating limitations (not going into them here).  Another option is loading all the data into memory, but I quickly hit the quota imposed by google. A final option is to use django-nonrel + djangoappengine, but I'm afraid that package is still in its infancy.\nIdeally, I'd like to create a read-only sqlite database that uses a blobstore as its data source. Is this possible?","AnswerCount":3,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":803,"Q_Id":4663071,"Users Score":2,"Answer":"I don't think you're likely to find anything like that...surely not over blobstore. Because if all your data is stored in a single blob, you'd have to read the entire database into memory for any operation, and you said you can't do that.\nUsing the datastore as your backend is more plausible, but not much. The big issue with providing a SQLite driver there would be implementing transaction semantics, and since that's the key thing GAE takes away from you for the sake of high availability, it's hard to imagine somebody going to much trouble to write such a thing.","Q_Score":2,"Tags":"python,google-app-engine,sqlite,relational-database,non-relational-database","A_Id":4663353,"CreationDate":"2011-01-11T21:55:00.000","Title":"A Read-Only Relational Database on Google App Engine?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I have a medium size (~100mb) read-only database that I want to put on google app engine. I  could put it into the datastore, but the datastore is kind of slow, has no relational features, and has many other frustrating limitations (not going into them here).  Another option is loading all the data into memory, but I quickly hit the quota imposed by google. A final option is to use django-nonrel + djangoappengine, but I'm afraid that package is still in its infancy.\nIdeally, I'd like to create a read-only sqlite database that uses a blobstore as its data source. Is this possible?","AnswerCount":3,"Available Count":2,"Score":0.1325487884,"is_accepted":false,"ViewCount":803,"Q_Id":4663071,"Users Score":2,"Answer":"django-nonrel does not magically provide an SQL database - so it's not really a solution to your problem.\nAccessing a blobstore blob like a file is possible, but the SQLite module requires a native C extension, which is not enabled on App Engine.","Q_Score":2,"Tags":"python,google-app-engine,sqlite,relational-database,non-relational-database","A_Id":4663631,"CreationDate":"2011-01-11T21:55:00.000","Title":"A Read-Only Relational Database on Google App Engine?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I'm trying to use clr.AddReference to add sqlite3 functionality to a simple IronPython program I'm writing; but everytime I try to reference System.Data.SQLite I get this error:\n\nTraceback (most recent call last):\n    File \"\", line 1, in \n  IOError: System.IO.IOException: Could not add reference to assembly System.Data.SQLite\n     at Microsoft.Scripting.Actions.Calls.MethodCandidate.Caller.Call(Object[] args, Boolean&shouldOptimize)\n     at IronPython.Runtime.Types.BuiltinFunction.BuiltinFunctionCaller2.Call1(CallSite site, CodeContext context, TFuncType func, T0 arg0)\n     at System.Dynamic.UpdateDelegates.UpdateAndExecute3[T0,T1,T2,TRet](CallSite site, T0 arg0, T1 arg1, T2 arg2)\n     at CallSite.Target(Closure , CallSite , CodeContext , Object , Object )\n     at IronPython.Compiler.Ast.CallExpression.Invoke1Instruction.Run(InterpretedFrame frame)\n     at Microsoft.Scripting.Interpreter.Interpreter.Run(InterpretedFrame frame)\n     at Microsoft.Scripting.Interpreter.LightLambda.Run2[T0,T1,TRet](T0 arg0, T1 arg1)\n     at IronPython.Runtime.FunctionCode.Call(CodeContext context)\n     at IronPython.Runtime.Operations.PythonOps.QualifiedExec(CodeContext context, Object code, PythonDictionary globals, Object locals)\n     at Microsoft.Scripting.Interpreter.ActionCallInstruction4.Run(InterpretedFrame frame)\n     at Microsoft.Scripting.Interpreter.Interpreter.Run(InterpretedFrame frame)\n\nI've been testing out the imports and references in the interpreter mainly, and these are the lines I test:\n\nimport sys\n  import clr\n  sys.path.append(\"C:\/Program Files (x86)\/SQLite.NET\/bin\")\n  clr.AddReference(\"System.Data.SQLite\")  \n\nThe error happens after the clr.AddReference line is entered. How would I add System.Data.SQLite properly?","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":1695,"Q_Id":4682960,"Users Score":1,"Answer":"My first guess is that you're trying to load the x86 (32-bit) System.Data.SQLite.dll in a x64 (64-bit) process, or vice versa. System.Data.SQLite.dll contains the native sqlite3 library, which must be compiled for x86 or x64, so there is a version of System.Data.SQLite.dll for each CPU.\nIf you're using the console, ipy.exe is always 32-bit (even on 64-bit platforms) while ipy64.exe is AnyCPU, so it matches the current platform. If you're hosting IronPython, and the host app is AnyCPU, you need to load the right copy of System.Data.SQLite.dll for the machine you're running on (or just force the host app x86).","Q_Score":1,"Tags":"ado.net,ironpython,system.data.sqlite","A_Id":4696478,"CreationDate":"2011-01-13T17:11:00.000","Title":"Adding System.Data.SQLite reference in IronPython","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":1,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I read somewhere that to save data to a SQLite3 database in Python, the method commit of the connection object should be called. Yet I have never needed to do this. Why?","AnswerCount":5,"Available Count":1,"Score":0.1194272985,"is_accepted":false,"ViewCount":20808,"Q_Id":4699605,"Users Score":3,"Answer":"Python sqlite3 issues a BEGIN statement automatically before \"INSERT\" or \"UPDATE\". After that it automatically commits on any other command or db.close()","Q_Score":18,"Tags":"python,transactions,sqlite,autocommit","A_Id":15967816,"CreationDate":"2011-01-15T12:36:00.000","Title":"Why doesn\u2019t SQLite3 require a commit() call to save data?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I've got a situation where I'm contemplating using subversion\/svn as the repository\/version control system for a project. I'm trying to figure out if it's possible, (and if so, how) to be able to have the subversion system, on a post commit hook\/process to to write the user\/file\/time (and maybe msg) to either an external file (csv) or to a mysql db. \nOnce I can figure out how to invoke the post commit hook to write the output to a file, I can then modify my issue tracker\/project app to then implement a basic workflow process based on the user role, as well as the success\/failure of the repository files.\nShort sample\/pointers would be helpful.\nMy test env, is running subversion\/svnserve on centos5. The scripting languages in use are Php\/Python.","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":1005,"Q_Id":4701902,"Users Score":0,"Answer":"I would say that's possible, but you are going to need a bit of work to retrieve the username, date and commit message.\nSubversion invokes the post-commit hook with the repo path and the number of revision which was just committed as arguments.\nIn order to retrieve the information you're looking for, you will need to use an executable by the name of svnlook, which is bundled with Subversion.\nSee repo\\hooks\\post-commit.tmpl for a rather clear explanation about how to use it\nAlso, take a look at svnlook help, it's not difficult to use.","Q_Score":1,"Tags":"php,python,svn,hook,svn-hooks","A_Id":4701984,"CreationDate":"2011-01-15T20:14:00.000","Title":"subversion post commit hooks","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I've got a situation where I'm contemplating using subversion\/svn as the repository\/version control system for a project. I'm trying to figure out if it's possible, (and if so, how) to be able to have the subversion system, on a post commit hook\/process to to write the user\/file\/time (and maybe msg) to either an external file (csv) or to a mysql db. \nOnce I can figure out how to invoke the post commit hook to write the output to a file, I can then modify my issue tracker\/project app to then implement a basic workflow process based on the user role, as well as the success\/failure of the repository files.\nShort sample\/pointers would be helpful.\nMy test env, is running subversion\/svnserve on centos5. The scripting languages in use are Php\/Python.","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":1005,"Q_Id":4701902,"Users Score":0,"Answer":"Indeed it is very possible, in your repository root there should be a folder named hooks, inside which should be a file named post-commit (if not, create one), add whatever bash code you put there and it will execute after every commit.\nNote, there are 2 variables that are passed into the script $1 is the repository, and $2 is the revision number (i think), you can use those two variables to execute some svn commands\/queries, and pull out the required data, and do with it whatever your heart desires.","Q_Score":1,"Tags":"php,python,svn,hook,svn-hooks","A_Id":4701973,"CreationDate":"2011-01-15T20:14:00.000","Title":"subversion post commit hooks","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"According to the Bigtable original article, a column key of a Bigtable is named using \"family:qualifier\" syntax where column family names must be printable but qualifiers may be arbitrary strings. In the application I am working on, I would like to specify the qualifiers using Chinese words (or phrase). Is it possible to do this in Google App Engine? Is there a Bigtable API other than provided datastore API? It seems Google is tightly protecting its platform for good reasons.\nThanks in advance.\nMarvin","AnswerCount":1,"Available Count":1,"Score":0.3799489623,"is_accepted":false,"ViewCount":134,"Q_Id":4712143,"Users Score":2,"Answer":"The Datastore is the only interface to the underlying storage on App Engine. You should be able to use any valid UTF-8 string as a kind name, key name, or property name, however.","Q_Score":1,"Tags":"python,google-app-engine","A_Id":4718951,"CreationDate":"2011-01-17T10:32:00.000","Title":"Is there an API of Google App Engine provided to better configure the Bigtable besides Datastore?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I want to try Mongodb w\/ mongoengine.  I'm new to Django and databases and I'm having a fit with Foreign Keys, Joins, Circular Imports (you name it).  I know I could eventually work through these issues but Mongo just seems like a simpler solution for what I am doing.  My question is I'm using a lot of pluggable apps (Imagekit, Haystack, Registration, etc) and wanted to know if these apps will continue to work if I make the switch. Are there any known headaches that I will encounter, if so I might just keep banging my head with MySQL.","AnswerCount":6,"Available Count":5,"Score":0.0333209931,"is_accepted":false,"ViewCount":2780,"Q_Id":4718580,"Users Score":1,"Answer":"I've used mongoengine with django but you need to create a file like mongo_models.py for example. In that file you define your Mongo documents. You then create forms to match each Mongo document. Each form has a save method which inserts or updates whats stored in Mongo. Django forms are designed to plug into any data back end ( with a bit of craft )\nBEWARE: If you have very well defined and structured data that can be described in documents or models then don't use Mongo. Its not designed for that and something like PostGreSQL will work much better.\n\nI use PostGreSQL for relational or well structured data because its good for that. Small memory footprint and good response.\nI use Redis to cache or operate in memory queues\/lists because its very good for that. great performance providing you have the memory to cope with it.\nI use Mongo to store large JSON documents and to perform Map and reduce on them ( if needed ) because its very good for that. Be sure to use indexing on certain columns if you can to speed up lookups.\n\nDon't circle to fill a square hole. It won't fill it.\nI've seen too many posts where someone wanted to swap a relational DB for Mongo because Mongo is a buzz word. Don't get me wrong, Mongo is really great... when you use it appropriately. I love using Mongo appropriately","Q_Score":2,"Tags":"python,django,mongodb,mongoengine","A_Id":10204815,"CreationDate":"2011-01-17T22:22:00.000","Title":"Converting Django project from MySQL to Mongo, any major pitfalls?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I want to try Mongodb w\/ mongoengine.  I'm new to Django and databases and I'm having a fit with Foreign Keys, Joins, Circular Imports (you name it).  I know I could eventually work through these issues but Mongo just seems like a simpler solution for what I am doing.  My question is I'm using a lot of pluggable apps (Imagekit, Haystack, Registration, etc) and wanted to know if these apps will continue to work if I make the switch. Are there any known headaches that I will encounter, if so I might just keep banging my head with MySQL.","AnswerCount":6,"Available Count":5,"Score":1.2,"is_accepted":true,"ViewCount":2780,"Q_Id":4718580,"Users Score":9,"Answer":"There's no reason why you can't use one of the standard RDBMSs for all the standard Django apps, and then Mongo for your app. You'll just have to replace all the standard ways of processing things from the Django ORM with doing it the Mongo way.\nSo you can keep urls.py and its neat pattern matching, views will still get parameters, and templates can still take objects. \nYou'll lose querysets because I suspect they are too closely tied to the RDBMS models - but they are just lazily evaluated lists really. Just ignore the Django docs on writing models.py and code up your database business logic in a Mongo paradigm.\nOh, and you won't have the Django Admin interface for easy access to your data.","Q_Score":2,"Tags":"python,django,mongodb,mongoengine","A_Id":4718924,"CreationDate":"2011-01-17T22:22:00.000","Title":"Converting Django project from MySQL to Mongo, any major pitfalls?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I want to try Mongodb w\/ mongoengine.  I'm new to Django and databases and I'm having a fit with Foreign Keys, Joins, Circular Imports (you name it).  I know I could eventually work through these issues but Mongo just seems like a simpler solution for what I am doing.  My question is I'm using a lot of pluggable apps (Imagekit, Haystack, Registration, etc) and wanted to know if these apps will continue to work if I make the switch. Are there any known headaches that I will encounter, if so I might just keep banging my head with MySQL.","AnswerCount":6,"Available Count":5,"Score":-0.0333209931,"is_accepted":false,"ViewCount":2780,"Q_Id":4718580,"Users Score":-1,"Answer":"Primary pitfall (for me): no JOINs!","Q_Score":2,"Tags":"python,django,mongodb,mongoengine","A_Id":4719398,"CreationDate":"2011-01-17T22:22:00.000","Title":"Converting Django project from MySQL to Mongo, any major pitfalls?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I want to try Mongodb w\/ mongoengine.  I'm new to Django and databases and I'm having a fit with Foreign Keys, Joins, Circular Imports (you name it).  I know I could eventually work through these issues but Mongo just seems like a simpler solution for what I am doing.  My question is I'm using a lot of pluggable apps (Imagekit, Haystack, Registration, etc) and wanted to know if these apps will continue to work if I make the switch. Are there any known headaches that I will encounter, if so I might just keep banging my head with MySQL.","AnswerCount":6,"Available Count":5,"Score":0.0,"is_accepted":false,"ViewCount":2780,"Q_Id":4718580,"Users Score":0,"Answer":"Upfront, it won't work for any existing Django app that ships it's models. There's no backend for storing Django's Model data in mongodb or other NoSQL storages at the moment and, database backends aside, models themselves are somewhat of a moot point, because once you get in to using someones app (django.contrib apps included) that ships model-template-view triads, whenever you require a slightly different model for your purposes you either have to edit the application code (plain wrong), dynamically edit the contents of imported Python modules at runtime (magical), fork the application source altogether (cumbersome) or provide additional settings (good, but it's a rare encounter, with django.contrib.auth probably being the only widely known example of an application that allows you to dynamically specify which model it will use, as is the case with user profile models through the AUTH_PROFILE_MODULE setting).\nThis might sound bad, but what it really means is that you'll have to deploy SQL and NoSQL databases in parallel and go from an app-to-app basis--like Spacedman suggested--and if mongodb is the best fit for a certain app, hell, just roll your own custom app.\nThere's a lot of fine Djangonauts with NoSQL storages on their minds. If you followed the streams from the past Djangocon presentations, every year there's been important discussions about how Django should leverage NoSQL storages. I'm pretty sure, in this year or the next, someone will refactor the apps and models API to pave the path to a clean design that can finally unify all the different flavors of NoSQL storages as part of the Django core.","Q_Score":2,"Tags":"python,django,mongodb,mongoengine","A_Id":4719167,"CreationDate":"2011-01-17T22:22:00.000","Title":"Converting Django project from MySQL to Mongo, any major pitfalls?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I want to try Mongodb w\/ mongoengine.  I'm new to Django and databases and I'm having a fit with Foreign Keys, Joins, Circular Imports (you name it).  I know I could eventually work through these issues but Mongo just seems like a simpler solution for what I am doing.  My question is I'm using a lot of pluggable apps (Imagekit, Haystack, Registration, etc) and wanted to know if these apps will continue to work if I make the switch. Are there any known headaches that I will encounter, if so I might just keep banging my head with MySQL.","AnswerCount":6,"Available Count":5,"Score":0.0,"is_accepted":false,"ViewCount":2780,"Q_Id":4718580,"Users Score":0,"Answer":"I have recently tried this (although without Mongoengine).  There are a huge number of pitfalls, IMHO:\n\nNo admin interface. \nNo Auth  django.contrib.auth relies on the DB interface. \nMany things rely on django.contrib.auth.User.  For example, the RequestContext class.  This is a huge hindrance.\nNo Registration (Relies on the DB interface and django.contrib.auth) \n\nBasically, search through the django interface for references to django.contrib.auth and you'll see how many things will be broken.\nThat said, it's possible that MongoEngine provides some support to replace\/augment django.contrib.auth with something better, but there are so many things that depend on it that it's hard to say how you'd monkey patch something that much.","Q_Score":2,"Tags":"python,django,mongodb,mongoengine","A_Id":4728500,"CreationDate":"2011-01-17T22:22:00.000","Title":"Converting Django project from MySQL to Mongo, any major pitfalls?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a .sql file containing thousands of individual insert statements.  It takes forever to do them all.  I am trying to figure out a way to do this more efficiently.  In python the sqlite3 library can't do things like \".read\" or \".import\" but executescript is too slow for that many inserts.  \nI installed the sqlite3.exe shell in hopes of using \".read\" or \".import\" but I can't quite figure out how to use it.  Running it through django in eclipse doesn't work because it expects the database to be at the root of my C drive which seems silly.  Running it through the command line doesn't work because it can't find my database file (unless I'm doing something wrong)\nAny tips?\nThanks!","AnswerCount":4,"Available Count":2,"Score":0.049958375,"is_accepted":false,"ViewCount":1859,"Q_Id":4719836,"Users Score":1,"Answer":"Use a parameterized query \nand\nUse a transaction.","Q_Score":6,"Tags":"python,sql,django,sqlite","A_Id":4724461,"CreationDate":"2011-01-18T02:01:00.000","Title":"Python and sqlite3 - adding thousands of rows","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a .sql file containing thousands of individual insert statements.  It takes forever to do them all.  I am trying to figure out a way to do this more efficiently.  In python the sqlite3 library can't do things like \".read\" or \".import\" but executescript is too slow for that many inserts.  \nI installed the sqlite3.exe shell in hopes of using \".read\" or \".import\" but I can't quite figure out how to use it.  Running it through django in eclipse doesn't work because it expects the database to be at the root of my C drive which seems silly.  Running it through the command line doesn't work because it can't find my database file (unless I'm doing something wrong)\nAny tips?\nThanks!","AnswerCount":4,"Available Count":2,"Score":0.0996679946,"is_accepted":false,"ViewCount":1859,"Q_Id":4719836,"Users Score":2,"Answer":"In addition to running the queries in bulk inside a single transaction, also try VACUUM and ANALYZEing the database file. It helped a similar problem of mine.","Q_Score":6,"Tags":"python,sql,django,sqlite","A_Id":13787939,"CreationDate":"2011-01-18T02:01:00.000","Title":"Python and sqlite3 - adding thousands of rows","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"At my organization, PostgreSQL databases are created with a 20-connection limit as a matter of policy. This tends to interact poorly when multiple applications are in play that use connection pools, since many of those open up their full suite of connections and hold them idle.\nAs soon as there are more than a couple of applications in contact with the DB, we run out of connections, as you'd expect.\nPooling behaviour is a new thing here; until now we've managed pooled connections by serializing access to them through a web-based DB gateway (?!) or by not pooling anything at all. As a consequence, I'm having to explain (literally, 5 trouble tickets from one person over the course of the project) over and over again how the pooling works.\nWhat I want is one of the following:\n\nA solid, inarguable rationale for increasing the number of available connections to the database in order to play nice with pools.\nIf so, what's a safe limit? Is there any reason to keep the limit to 20?\nA reason why I'm wrong and we should cut the size of the pools down or eliminate them altogether.\n\nFor what it's worth, here are the components in play. If it's relevant how one of these is configured, please weigh in:\nDB: PostgreSQL 8.2.  No, we won't be upgrading it as part of this.\nWeb server: Python 2.7, Pylons 1.0, SQLAlchemy 0.6.5, psycopg2  \n\nThis is complicated by the fact that some aspects of the system access data using SQLAlchemy ORM using a manually configured engine, while others access data using a different engine factory (Still sqlalchemy) written by one of my associates that wraps the connection in an object that matches an old PHP API.\n\nTask runner: Python 2.7, celery 2.1.4, SQLAlchemy 0.6.5, psycopg2","AnswerCount":1,"Available Count":1,"Score":0.3799489623,"is_accepted":false,"ViewCount":303,"Q_Id":4729361,"Users Score":2,"Answer":"I think it's reasonable to require one connection per concurrent activity, and it's reasonable to assume that concurrent HTTP requests are concurrently executed.\nNow, the number of concurrent HTTP requests you want to process should scale with a) the load on your server, and b) the number of CPUs you have available. If all goes well, each request will consume CPU time somewhere (in the web server, in the application server, or in the database server), meaning that you couldn't process more requests concurrently than you have CPUs. In practice, it's not that all goes well: some requests will wait for IO at some point, and not consume any CPU. So it's ok to process some more requests concurrently than you have CPUs.\nStill, assuming that you have, say, 4 CPUs, allowing 20 concurrent requests is already quite some load. I'd rather throttle HTTP requests than increasing the number of requests that can be processed concurrently. If you find that a single request needs more than one connection, you have a flaw in your application.\nSo my recommendation is to cope with the limit, and make sure that there are not too many idle connections (compared to the number of requests that you are actually processing concurrently).","Q_Score":3,"Tags":"python,database,sqlalchemy,pylons,connection-pooling","A_Id":4729629,"CreationDate":"2011-01-18T21:40:00.000","Title":"How can I determine what my database's connection limits should be?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Question is rather conceptual, then direct.\nWhat's the best solution to keep two different calendars synchronised? I can run a cron job for example every minute, I can keep additional information in database. How to avoid events conflicts?\nAs far I was thinking about these two solutions. First one is keeping a database which gathers information from both calendars and each time compares if something new appeared in any of them. Inside this database we can judge, which events should be added, edited or removed and then send those information back to both calendars.\nSecond one is keepien two databases for both calendars and collecting information separately. Then, after those databases are compared, we can say, where did the changes occure and send information from database A to calendar B or from database B to calendar A. I'm afraid this solution leads to more conflicts when changes were made to both databases.  \nWhat do you think of these? To be more accurate, I mean two google calendars and script written in python using gdata. Any idea of more simple solution?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":516,"Q_Id":4737852,"Users Score":0,"Answer":"Most calendars, including the Google calendar, has ways to import and synchronize data. You can use these ways. Just import the gdata information (perhaps you need to make it into ics first, I don't know) into the Google calendar.","Q_Score":0,"Tags":"python,synchronization,calendar","A_Id":4738228,"CreationDate":"2011-01-19T16:27:00.000","Title":"Two calendars synchronization","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I can connect to a Oracle 10g release 2 server using instant client. Using pyodbc and cx_Oracle.\nUsing either module, I can execute a select query without any problems, but when I try to update a table, my program crashes.\nFor example,\nSELECT * FROM table WHERE col1 = 'value'; works fine.\nUPDATE table SET col2 = 'value' WHERE col1 = 'val'; does not work\nIs this a known limitation with instant client, or is there a problem with my installation?\nThanks in advance for your help.","AnswerCount":2,"Available Count":2,"Score":0.0996679946,"is_accepted":false,"ViewCount":587,"Q_Id":4748962,"Users Score":1,"Answer":"Use the instant client with SQL*Plus and see if you can run the update. If there's a problem, SQL*Plus is production quality, so won't crash and it should give you a reasonable error message.","Q_Score":2,"Tags":"python,oracle,pyodbc,cx-oracle,instantclient","A_Id":4753975,"CreationDate":"2011-01-20T15:26:00.000","Title":"Oracle instant client can't execute sql update","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I can connect to a Oracle 10g release 2 server using instant client. Using pyodbc and cx_Oracle.\nUsing either module, I can execute a select query without any problems, but when I try to update a table, my program crashes.\nFor example,\nSELECT * FROM table WHERE col1 = 'value'; works fine.\nUPDATE table SET col2 = 'value' WHERE col1 = 'val'; does not work\nIs this a known limitation with instant client, or is there a problem with my installation?\nThanks in advance for your help.","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":587,"Q_Id":4748962,"Users Score":0,"Answer":"Sounds more like your user you are connecting with doesn't have those privileges on that table.  Do you get an ORA error indicating insufficient permissions when performing the update?","Q_Score":2,"Tags":"python,oracle,pyodbc,cx-oracle,instantclient","A_Id":4749022,"CreationDate":"2011-01-20T15:26:00.000","Title":"Oracle instant client can't execute sql update","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a massive data set of customer information (100s of millions of records, 50+ tables).\nI am writing a python (twisted) app that I would like to interact with the dataset, performing table manipulation.  What I really need is an abstraction of 'table', so I can add\/remove\/alter columns\/tables without having to resort to only creating SQL.\nIs there an ORM that will not add significant overhead to my application, considering the size of the dataset?","AnswerCount":4,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":858,"Q_Id":4764476,"Users Score":0,"Answer":"I thought that ORM solutions had to do with DQL (Data Query Language), not DDL (Data Definition Language).  You don't use ORM to add, alter, or remove columns at runtime.  You'd have to be able to add, alter, or remove object attributes and their types at the same time.\nORM is about dynamically generating SQL and developer's lift, not what you're alluding to.","Q_Score":1,"Tags":"python,orm","A_Id":4764551,"CreationDate":"2011-01-21T22:26:00.000","Title":"Python ORM for massive data set","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm trying to use sqlalchemy on Cygwin with a MSSQL backend but I cannot seem to get any of the MSSQL Python DB APIs installed on Cygwin. Is there one that is known to work?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":682,"Q_Id":4770083,"Users Score":0,"Answer":"FreeTDS + unixodbc + pyodbc stack will work on Unix-like systems and should therefore work just as well in Cygwin. You should use version 8.0 of TDS protocol. This can be configured in connection string.","Q_Score":2,"Tags":"python,sql-server,cygwin,sqlalchemy","A_Id":5013126,"CreationDate":"2011-01-22T19:34:00.000","Title":"Which Python (sqlalchemy) mssql DB API works in Cygwin?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"A website I am making revolves around a search utility, and a want to have something on the homepage that lists the top 10 (or something) most searched queries of the day.\nWhat would be the easiest \/ most efficient way of doing this?\nShould I use a sql database, or just a text file containing the top 10 queries and a cronjob erasing the data every day?\nAlso, how would I avoid the problem of two users searching for something at the same and it only recording one of them, i.e multithreading?\nThe back-end of the site is all written in python","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":98,"Q_Id":4778058,"Users Score":2,"Answer":"Put the queries in a table, with one row per distinct query, and a column to count. Insert if the query doesn't exist already, or otherwise increment the query row counter. \nPut a cron job together than empties the table at 12 midnight. Use transactions to prevent two different requests from colliding.","Q_Score":0,"Tags":"python,sql,multithreading","A_Id":4778081,"CreationDate":"2011-01-24T02:23:00.000","Title":"How to make a \"top queries\" page","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"In some project I implement user-requested mapping (at runtime) of two tables which are connected by a 1-to-n relation (one table has a ForeignKey field).\nFrom what I get from the documentation, the usual way is to add a orm.relation to the mapped properties with a mapped_collection as collection_class on the non-foreignkey table with a backref, so that in the end both table orm objects have each other mapped on an attribute (one has a collection through the collection_class of the orm.relation used on it, the other has an attribute placed on it by the backref).\nI am in a situation where I sometimes do just want the ForeignKey-side to have a mapped attribute to the other table (that one, that is created by the backref), depending on what the user decides (he might just want to have that side mapped).\nNow I'm wondering whether I can simply use an orm.relation on the ForeignKey table aswell, so I'd probably end up with an orm.relation on the non-foreignkey table as before with a mapped_collection but no backref, and another orm.relation on the foreignkey table replacing that automagic backref (making two orm.relations on both tables mapping each other from both sides).\nWill that get me into trouble? Is the result equivalent (to just one orm.relation on the non-foreignkey table with a backref)? Is there another way how I could map just on the ForeignKey-side without having to map the dictionary on the non-ForeignKey table aswell with that backref?","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":664,"Q_Id":4782344,"Users Score":1,"Answer":"I found the answer myself by now:\nIf you use an orm.relation from each side and no backrefs, you have to use back_populates or if you mess around at one side, it won't be properly updated in the mapping on the other side.\nTherefore, an orm.relation from each side instead of an automated backref IS possible but you have to use back_populates accordingly.","Q_Score":0,"Tags":"python,database,sqlalchemy,relation","A_Id":5594860,"CreationDate":"2011-01-24T13:10:00.000","Title":"SQLAlchemy - difference between mapped orm.relation with backref or two orm.relation from both sides","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm writing a network scheduling like program in Python 2.6+ in which I have a complex queue requirement: Queue should store packets, should retrieve by timestamp or by packet ID in O(1), should be able to retrieve all the packets below a certain threshold, sort packet by priorities etc. It should insert and delete with reasonable complexity as well.\nNow I have two choices:\n\nCombine a few data structures and synchronize them properly to fulfill my requirement.\nUse some in-memory database so that I can perform all sorts of operations easily.\n\nAny suggestions please?","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":94,"Q_Id":4802900,"Users Score":0,"Answer":"A database is just some indexes and fancy algorithms wrapped around a single data structure -- a table.  You don't have a lot of control about what happens under the hood.\nI'd try using the built-in Python datastructures.","Q_Score":0,"Tags":"python,data-structures","A_Id":4803269,"CreationDate":"2011-01-26T09:20:00.000","Title":"Need advice on customized datastructure vs using in-memory DB?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am new to python and its workings.\nI have an excel spreadsheet which was got using some VBA's.\nNow I want to invoke Python to do some of the jobs...\nMy question then is: How can I use python script instead of VBA in an excel spreadsheet?\nAn example of such will be appreciated.","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":2789,"Q_Id":4829509,"Users Score":0,"Answer":"I've always done the manipulation of Excel spreadsheets and Word documents with standalone scripts which use COM objects to manipulate the documents. I've never come across a good use case for putting Python into a spreadsheet in place of VBA.","Q_Score":2,"Tags":"python,excel","A_Id":4872985,"CreationDate":"2011-01-28T14:49:00.000","Title":"Use of python script instead of VBA in Excel","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"How do I use the Werkzeug framework without any ORM like SQLAlchemy? In my case, it's a lot of effort to rewrite all the tables and columns in SQLAlchemy from existing tables & data.\nHow do I query the database and make an object from the database output?\nIn my case now, I use Oracle with cx_Oracle. If you have a solution for MySQL, too, please mention it.\nThanks.","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":445,"Q_Id":4838528,"Users Score":0,"Answer":"Is it a problem to use normal DB API, issue regular SQL queries, etc? cx_Oracle even has connection pooling biolt in to help you manage connections.","Q_Score":1,"Tags":"python,orm,werkzeug","A_Id":4838669,"CreationDate":"2011-01-29T18:09:00.000","Title":"Werkzeug without ORM","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have several occasions where I want to collect data when in the field. This is in situations where I do not always have access to my postgres database.\nTo keep things in sync, it would be excellent if I could use psycopg2 functions offline to generate queries that can be held back and once I am able to connect to the database; process everything that is held back.\nOne thing I am currently struggling with is that the psycopg2 cursor requires a connection to be constructed.\nMy question is:\nIs there a way to use a cursor to do things like mogrify without an active connection object? Or with a connection object that is not connected to a database? I would then like to write the mogrify results temporarily to file so they can be processed later.","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":3099,"Q_Id":4879804,"Users Score":0,"Answer":"It seems like it would be easier and more versatile to store the data to be inserted later in another structure. Perhaps a csv file. Then when you connect you can run through that table, but you can also easily do other things with that CSV if necessary.","Q_Score":12,"Tags":"python,psycopg2,offline-mode","A_Id":4880978,"CreationDate":"2011-02-02T21:00:00.000","Title":"Use psycopg2 to construct queries without connection","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"After setting up a django site and running on the dev server, I have finally gotten around to figuring out deploying it in a production environment using the recommended mod_wsgi\/apache22. I am currently limited to deploying this on a Windows XP machine.\nMy problem is that several django views I have written use the python subprocess module to run programs on the filesystem. I keep getting errors when running the subprocess.Popen I have seen several SO questions that have asked about this, and the accepted answer is to use WSGIDaemonProcess to handle the problem (due to permissions of the apache user, I believe).\nThe only problem with this is that WSGIDaemonProcess is not available for mod_wsgi on Windows. Is there any way that I can use mod_wsgi\/apache\/windows\/subprocess together?","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":2617,"Q_Id":4882605,"Users Score":1,"Answer":"I ran into a couple of issues trying to use subprocess under this configuration. Since I am not sure what specifically you had trouble with I can share a couple of things that were not easy for me to solve but in hindsight seem pretty trivial.\n\nI was receiving permissions related errors when trying to execute an application. I searched quite a bit but was having a hard time finding Windows specific answers. This one was obvious: I changed the user under which Apache runs to a user with higher permissions. (Note, there are security implications with that so you want to be sure you understand what you are getting in to).\nDjango (depending on your configuration) may store strings as Unicode. I had a command line application I was trying to run with some parameters from my view which was crashing despite having the correct arguments passed in. After a couple hours of frustration I did a type(args) which returned <type 'unicode'> rather than my expected string. A quick conversion resolved that issue.","Q_Score":6,"Tags":"python,django,apache,subprocess,mod-wsgi","A_Id":8750220,"CreationDate":"2011-02-03T04:07:00.000","Title":"Django + Apache + Windows WSGIDaemonProcess Alternative","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm storing MySQL DateTimes in UTC, and let the user select their time zone, storing that information.\nHowever, I want to to some queries that uses group by a date.  Is it better to store that datetime information in UTC (and do the calculation every time) or is it better to save it in the timezone given?  Since time zones for users can change, I wonder.\nThanks","AnswerCount":2,"Available Count":2,"Score":0.0996679946,"is_accepted":false,"ViewCount":123,"Q_Id":4928220,"Users Score":1,"Answer":"It's almost always better to save the time information in UTC, and convert it to local time when needed for presentation and display.\nOtherwise, you will go stark raving mad trying to manipulate and compare dates and times in your system because you will have to convert each time to UTC time for comparison and manipulation.","Q_Score":0,"Tags":"python,mysql,timezone","A_Id":4928246,"CreationDate":"2011-02-08T00:10:00.000","Title":"How to handle time zones in a CMS?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm storing MySQL DateTimes in UTC, and let the user select their time zone, storing that information.\nHowever, I want to to some queries that uses group by a date.  Is it better to store that datetime information in UTC (and do the calculation every time) or is it better to save it in the timezone given?  Since time zones for users can change, I wonder.\nThanks","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":123,"Q_Id":4928220,"Users Score":3,"Answer":"Generally always store in UTC and convert for display, it's the only sane way to do time differences etc. Or when somebody next year decides to change the summer time dates.","Q_Score":0,"Tags":"python,mysql,timezone","A_Id":4928244,"CreationDate":"2011-02-08T00:10:00.000","Title":"How to handle time zones in a CMS?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am having problem when I do a query to mongodb using pymongo.\nI do not know how to avoid getting the _id for each record.\nI am doing something like this,\nresult = db.meta.find(filters, [\n                                   'model',\n                                'fields.parent',\n                                'fields.status',\n                               'fields.slug',\n                               'fields.firm',\n                               'fields.properties'])\nI do not want to iterate the cursor elements only to delete a field.\nThanks,\nJoaquin","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":803,"Q_Id":4937817,"Users Score":0,"Answer":"Does make any sense. The object id is core part of each document. Convert the BSON\/JSON document to a native datastructure (depending on your implementation language) and remove _id on this level. Apart from that it does not make much sense what you are trying to accomplish.","Q_Score":1,"Tags":"python,mongodb,pymongo","A_Id":4941686,"CreationDate":"2011-02-08T20:08:00.000","Title":"PYMongo: Keep returning _id in every record after quering, How can I exclude this record?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am in the middle of a project involving trying to grab numerous pieces of information out of 70GB worth of xml documents and loading it into a relational database (in this case postgres) I am currently using python scripts and psycopg2 to do this inserts and whatnot. I have found that as the number of rows in the some of the tables increase. (The largest of which is at around 5 million rows) The speed of the script (inserts) has slowed to a crawl. What was once taking a couple of minutes now takes about an hour.\nWhat can I do to speed this up? Was I wrong in using python and psycopg2 for this task? Is there anything I can do to the database that may speed up this process. I get the feeling I am going about this in entirely the wrong way.","AnswerCount":7,"Available Count":2,"Score":0.057080742,"is_accepted":false,"ViewCount":4138,"Q_Id":4968837,"Users Score":2,"Answer":"Considering the process was fairly efficient before and only now when the dataset grew up it slowed down my guess is it's the indexes. You may try dropping indexes on the table before the import and recreating them after it's done. That should speed things up.","Q_Score":4,"Tags":"python,database-design,postgresql,psycopg2","A_Id":4969077,"CreationDate":"2011-02-11T12:11:00.000","Title":"Postgres Performance Tips Loading in billions of rows","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am in the middle of a project involving trying to grab numerous pieces of information out of 70GB worth of xml documents and loading it into a relational database (in this case postgres) I am currently using python scripts and psycopg2 to do this inserts and whatnot. I have found that as the number of rows in the some of the tables increase. (The largest of which is at around 5 million rows) The speed of the script (inserts) has slowed to a crawl. What was once taking a couple of minutes now takes about an hour.\nWhat can I do to speed this up? Was I wrong in using python and psycopg2 for this task? Is there anything I can do to the database that may speed up this process. I get the feeling I am going about this in entirely the wrong way.","AnswerCount":7,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":4138,"Q_Id":4968837,"Users Score":0,"Answer":"I'd look at the rollback logs.  They've got to be getting pretty big if you're doing this in one transaction.\nIf that's the case, perhaps you can try committing a smaller transaction batch size.  Chunk it into smaller blocks of records (1K, 10K, 100K, etc.) and see if that helps.","Q_Score":4,"Tags":"python,database-design,postgresql,psycopg2","A_Id":4968869,"CreationDate":"2011-02-11T12:11:00.000","Title":"Postgres Performance Tips Loading in billions of rows","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am trying to find the best solution (perfomance\/easy code) for the following situation:\nConsidering a database system with two tables, A (production table) and A'(cache table):\n\nFuture rows are added first into A' table in order to not disturb the production one.\nWhen a timer says go (at midnight, for example) rows from A' are incorporated to A.\nDealing with duplicates, inexistent rows, etc have to be considerated. \n\nI've been reading some about Materialized Views, Triggers, etc. The problem is that I should not introduce so much noise in the production table because is the reference table for a server (a PowerDNS server in fact).\nSo, what do you guys make of it? Should I better use triggers, MV, or programatically outside of the database?? (I'm using python, BTW)\nThanks in advance for helping me.","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":611,"Q_Id":4973316,"Users Score":1,"Answer":"The \"best\" solution according to the criteria you've laid out so far would just be to insert into the production table.\n...unless there's actually something extremely relevant you're not telling us","Q_Score":0,"Tags":"python,postgresql,triggers,materialized-views","A_Id":4973738,"CreationDate":"2011-02-11T19:46:00.000","Title":"Materialize data from cache table to production table [PostgreSQL]","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"When exactly the database transaction is being commited? Is it for example at the end of every response generation?\nTo explain the question: I need to develop a bit more sophisticated application where I have to control DB transactions less or more manually. Especialy I have to be able to design a set of forms with some complex logics behind the forms (some kind of 'wizard') but the database operations must not be commited until the last form and the confirmation.\nOf course I could put everything to the session without making any DB change but it's not a solution, the changes are quite complex and realy have to be performed. So the only way is to keep it uncommited.\nNow back to the question: if I undertand how is it working in web2py it will be easier for me to decide if thats a good framework for me. I am a java and php programmer, I know python but I don't know web2py yet ...\nIf you know any web page when it's explained I also wppreciate.\nTHanks!","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":1224,"Q_Id":4979392,"Users Score":1,"Answer":"you can call db.commit() and db.rollback() pretty much everywhere. If you do not and the action does not raise an exception, it commits before returning a response to the client. If it raises an exception and it is not explicitly caught, it rollsback.","Q_Score":2,"Tags":"python,web2py","A_Id":5443158,"CreationDate":"2011-02-12T17:14:00.000","Title":"web2py and DB transactions","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am using TG2.1 on WinXP.\nPython ver is 2.6.\nTrying to use sqlautocode (0.5.2) for working with my existing MySQL schema.\nSQLAlchemy ver is 0.6.6\n\n\nimport sqlautocode  # works OK\n\n\nWhile trying to reflect the schema ----\n\n\nsqlautocode mysql:\\\\username:pswd@hostname:3306\\schema_name -o tables.py\n\n\nSyntaxError: invalid syntax\nis raised.\nCan someone please point out what's going wrong, & how to handle the same?\nThanks,\nVineet.","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":659,"Q_Id":4994838,"Users Score":1,"Answer":"Hey, I got it right somehow.\nThe problem seems to be version mismatch between SA 0.6 & sqlautocode 0.6\nSeems that they don't work in tandom.\nSo I removed those & installed SA 0.5\nNow it's working.\nThanks,\nVineet Deodhar.","Q_Score":2,"Tags":"python,web-applications,turbogears2","A_Id":5003413,"CreationDate":"2011-02-14T16:55:00.000","Title":"sqlautocode for mysql giving syntax error","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"This relates to primary key constraint in SQLAlchemy & sqlautocode.\nI have SA 0.5.1 & sqlautocode 0.6b1\nI have a MySQL table without primary key.\nsqlautocode spits traceback that \"could not assemble any primary key columns\".\nCan I rectify this with a patch sothat it will reflect tables w\/o primary key?\nThanks,\nVineet Deodhar","AnswerCount":3,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":321,"Q_Id":5003475,"Users Score":0,"Answer":"We've succeeded in faking sqa if the there's combination of columns on the underlying table that uniquely identify it.\nIf this is your own table and you're not live, add a primary key integer column or something.\nWe've even been able to map an existing legacy table in a database with a) no pk and b) no proxy for a primary key in the other columns. It was Oracle not MySQL but we were able to hack sqa to see Oracle's rowid as a pk, though this is only safe for insert and query...update is not possible since it can't uniquely identify which row it should be updating. But these are ugly hacks so if you can help it, don't go down that road.","Q_Score":0,"Tags":"python,web-applications,turbogears,turbogears2","A_Id":5292555,"CreationDate":"2011-02-15T12:11:00.000","Title":"sqlautocode : primary key required in tables?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"This relates to primary key constraint in SQLAlchemy & sqlautocode.\nI have SA 0.5.1 & sqlautocode 0.6b1\nI have a MySQL table without primary key.\nsqlautocode spits traceback that \"could not assemble any primary key columns\".\nCan I rectify this with a patch sothat it will reflect tables w\/o primary key?\nThanks,\nVineet Deodhar","AnswerCount":3,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":321,"Q_Id":5003475,"Users Score":0,"Answer":"If the problem is that sqlautocode will not generate your class code because it cannot determine the PKs of the table, then you would probably be able to change that code to fit your needs (even if it means generating SQLA code that doesn't have PKs). Eventually, if you're using the ORM side of SQLA, you're going to need fields defined as PKs, even if the database doesn't explicitly label them as such.","Q_Score":0,"Tags":"python,web-applications,turbogears,turbogears2","A_Id":5292729,"CreationDate":"2011-02-15T12:11:00.000","Title":"sqlautocode : primary key required in tables?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"This relates to primary key constraint in SQLAlchemy & sqlautocode.\nI have SA 0.5.1 & sqlautocode 0.6b1\nI have a MySQL table without primary key.\nsqlautocode spits traceback that \"could not assemble any primary key columns\".\nCan I rectify this with a patch sothat it will reflect tables w\/o primary key?\nThanks,\nVineet Deodhar","AnswerCount":3,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":321,"Q_Id":5003475,"Users Score":0,"Answer":"I don't think so. How an ORM is suposed to persist an object to the database without any way to uniquely identify records? \nHowever, most ORMs accept a primary_key argument so you can indicate the key if it is not explicitly defined in the database.","Q_Score":0,"Tags":"python,web-applications,turbogears,turbogears2","A_Id":5003573,"CreationDate":"2011-02-15T12:11:00.000","Title":"sqlautocode : primary key required in tables?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"The python unit testing framework called nosetest has a plugin for sqlalchemy, however there is no documentation for it that I can find. I'd like to know how it works, and if possible, see a code example.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":340,"Q_Id":5009112,"Users Score":0,"Answer":"It is my understanding that this plugin is only meant for unit testing SQLAlchemy itself and not as a general tool. Perhaps that is why there are no examples or documentation? Posting to the SQLAlchemy mailing list is likely to give you a better answer \"straight from the horse's mouth\".","Q_Score":3,"Tags":"python,sqlalchemy,nosetests","A_Id":10268378,"CreationDate":"2011-02-15T20:26:00.000","Title":"How does the nosetests sqlalchemy plugin work?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"We have a system which generates reports in XLS using Spreadsheet_Excel_Writer for smaller files and in case of huge files we just export them as CSVs.   \nWe now want to export excel sheets which are multicolor etc. as a part of report generation, which in excel could be done through a few macros.  \nIs there any good exporter which generates the excel sheets with macros?(Spreadsheet_Excel_Writer cant do this) If it exists for PHP it would be amazing but if it exists for any other language, its fine we could interface it.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":515,"Q_Id":5028536,"Users Score":0,"Answer":"It's your \"excel sheets with macros\" that is going to cause you all end of problems. If you're on a Windows platform, with Excel installed, then PHP's COM extension should allow you to do this. Otherwise, I'm nor aware of any PHP library which allows you to create macros... not even PHPExcel. I suspect the same will apply with most languages, other than perhaps those running with .Net (and possibly Mono).\nHowever, do you really need macros to play with colour? Can't you do this more simply with styles, and perhaps conditional formatting?\nPS. What's your definition of \"huge\"?","Q_Score":0,"Tags":"java,php,python,macros,xls","A_Id":5028703,"CreationDate":"2011-02-17T11:49:00.000","Title":"Good xls exporter to generate excel sheets automatically with a few macros from any programming language?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Basically I'm looking for an equivalent of DataMapper.auto_upgrade! from the Ruby world.\nIn other words:\n\nchange the model\nrun some magic -> current db schema is investigated and changed to reflect the model\nprofit\n\nOf course, there are cases when it's impossible for such alteration to be non-desctructive, eg. when you deleted some attribute. But I don't mean such case. I'm looking for a general solution which doesn't get in the way when rapidly prototyping and changing the schema.\nTIA","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":220,"Q_Id":5036118,"Users Score":0,"Answer":"Sqlalchemy-migrate (http:\/\/packages.python.org\/sqlalchemy-migrate\/) is intended to help do these types of operations.","Q_Score":0,"Tags":"python,orm,sqlalchemy","A_Id":5037471,"CreationDate":"2011-02-17T23:44:00.000","Title":"Can SQLAlchemy do a non-destructive alter of the db comparing the current model with db schema?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have recently converted my workspace file format for my application to sqlite.  In order to ensure robust operation on NFS I've used a common update policy, I do all modifications to a copy stored in a temp location on the local harddisk.  Only when saving do I modify the original file (potentially on NFS) by copying over the original file with the temp file.  I only open the orginal file to keep an exclusive lock on it so it someone else tries to open they will be warned that someone else is using it.\nThe problem is this:  When I go to save my temp file back over the original file I must release the lock on the orginal file, this provides a window for someone else to get in and take the original, albeit a small window.\nI can think of a few ways around this: \n(1) being to simply dump the contents of the temp in to the orginal by using sql, i.e. drop tables on original, vacumm original, select from temp and insert into orginal.  I don't like doing sql operations on a sqlite file stored on NFS though.  This scares me with corruptions issues.  Am I right to think like this?\n(2) Use various extra files to act as a guard to prevent other from coming in while copying the temp over the original.   Using files as a mutex is problematic at best.  I also don't like the idea of having extra files hanging around if the application crashes.\nI'm wondering if anyone has any different solutions for this.  Again to copy the temp file over the original file while ensuring other application don't sneak in and grab the original file while doing so?\nI'm using python2.5, sqlalchemy 0.6.6 and sqlite 3.6.20\nThanks,\nDean","AnswerCount":1,"Available Count":1,"Score":0.3799489623,"is_accepted":false,"ViewCount":2749,"Q_Id":5043327,"Users Score":2,"Answer":"SQLite NFS issues are due to broken caching and locking.  If your process is the only one accessing the file on NFS then you'll be ok.\nThe SQLite backup API was designed to solve exactly your problem.  You can either backup directly to the NFS database or to another local temp file and then copy that.  The backup API deals with all the locking and concurrency issues.\nYou can use APSW to get access to the backup API or the most recent version of pysqlite.  (Disclosure: I am the APSW author.)","Q_Score":3,"Tags":"python,sqlite,sqlalchemy,nfs","A_Id":5095693,"CreationDate":"2011-02-18T15:44:00.000","Title":"How to ensure a safe file sync with sqlite and NFS","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Consider this test case:\nimport sqlite3\n\ncon1 = sqlite3.connect('test.sqlite')\ncon1.isolation_level = None\ncon2 = sqlite3.connect('test.sqlite')\ncon2.isolation_level = None\ncur1 = con1.cursor()\ncur2 = con2.cursor()\ncur1.execute('CREATE TABLE foo (bar INTEGER, baz STRING)')\ncon1.isolation_level = 'IMMEDIATE'\ncur1.execute('INSERT INTO foo VALUES (1, \"a\")')\ncur1.execute('INSERT INTO foo VALUES (2, \"b\")')\nprint cur2.execute('SELECT * FROM foo').fetchall()\ncon1.commit()\nprint cur2.execute('SELECT * FROM foo').fetchall()\ncon1.rollback()\nprint cur2.execute('SELECT * FROM foo').fetchall()\nFrom my knowledge I was expecting to see this as a result:\n[]\n[(1, u'a'), (2, u'b')]\n[]\nBut here it's resulting in this:\n[]\n[(1, u'a'), (2, u'b')]\n[(1, u'a'), (2, u'b')]\nSo the call to rollback() method in the first connection didn't reverted the previously commited changes. Why? Shouldn't it roll back them?\nThank you in advance.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":488,"Q_Id":5051151,"Users Score":3,"Answer":"You can't both commit and rollback the same transaction.  con1.commit() ends your transaction on that cursor.  The next con1.rollback() is either being silently ignored or is rolling back an empty transaction.","Q_Score":0,"Tags":"python,sqlite,rollback","A_Id":5051345,"CreationDate":"2011-02-19T13:59:00.000","Title":"Python sqlite3 module not rolling back transactions","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am developing a multiplayer gaming server that uses Django for the webserver (HTML frontend, user authentication, games available, leaderboard, etc.) and Twisted to handle connections between the players and the games and to interface with the games themselves.  The gameserver, the webserver, and the database may run on different machines.\nWhat is the \"best\" way to architect the shared database, in a manner that supports changes to the database schema going forward.  Should I try incorporating Django's ORM in the Twisted framework and used deferreds to make it non-blocking?  Should I be stuck creating and maintaining two separate databases schemas \/ interfaces, one in Django's model and the other using twisted.enterprise.row?\nSimilarly, with user authentication, should I utilize twisted's user authentication functionality, or try to include Django modules into the gameserver to handle user authentication on the game side?","AnswerCount":2,"Available Count":2,"Score":0.1973753202,"is_accepted":false,"ViewCount":2454,"Q_Id":5051408,"Users Score":2,"Answer":"I would just avoid the Django ORM, it's not all that and it would be a pain to access outside of a Django context (witness the work that was required to make Django support multiple databases). Twisted database access always requires threads (even with twisted.adbapi), and threads give you access to any ORM you choose. SQLalchemy would be a good choice.","Q_Score":9,"Tags":"python,database,django,twisted","A_Id":5051832,"CreationDate":"2011-02-19T14:42:00.000","Title":"Sharing a database between Twisted and Django","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am developing a multiplayer gaming server that uses Django for the webserver (HTML frontend, user authentication, games available, leaderboard, etc.) and Twisted to handle connections between the players and the games and to interface with the games themselves.  The gameserver, the webserver, and the database may run on different machines.\nWhat is the \"best\" way to architect the shared database, in a manner that supports changes to the database schema going forward.  Should I try incorporating Django's ORM in the Twisted framework and used deferreds to make it non-blocking?  Should I be stuck creating and maintaining two separate databases schemas \/ interfaces, one in Django's model and the other using twisted.enterprise.row?\nSimilarly, with user authentication, should I utilize twisted's user authentication functionality, or try to include Django modules into the gameserver to handle user authentication on the game side?","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":2454,"Q_Id":5051408,"Users Score":10,"Answer":"First of all I'd identify why you need both Django and Twisted.  Assuming you are comfortable with Twisted using twisted.web and auth will easily be sufficient and you'll be able to reuse your database layer for both the frontend and backend apps.\nAlternatively you could look at it the other way, what is Twisted doing better as a game server?  Are you hoping to support more players (more simultaneous connections) or something else?  Consider that if you must use threaded within twisted to do blocking database access that you are most likely not going to be able to efficently\/reliably support hundreds of simultaneous threads.  Remember python has a Global Interpreter Lock so threads are not necessarily the best way to scale.  \nYou should also consider why you are looking to use a SQL Database and an ORM.  Does your game have data that is really best suited to being stored in an relational database?  Perhaps it's worth examining something like MongoDB or another key-value or object database for storing game state.  Many of these NoSQL stores have both blocking drivers for use in Django and non-blocking drivers for use in Twisted (txmongo for example).  \nThat said, if you're dead set on using both Django and Twisted there are a few techniques for embedding blocking DB access into a non-blocking Twisted server.\n\nadbapi (uses twisted thread pool)\nDirect use of the twisted thread pool using reactor.deferToThread\nThe Storm ORM has a branch providing Twisted support (it handles deferToThread calls internally)\nSAsync is a library that tries to make SQLAlchemy work in an Async way\nHave twisted interact via RPC with a process that manages the blocking DB\n\nSo you should be able to manage the Django ORM objects yourself by importing them in twisted and being very careful making calls to reactor.deferToThread.  There are many possible issues when working with these objects within twisted in that some ORM objects can issue SQL when accessing\/setting a property, etc.  \nI realize this isn't necessarily the answer you were expecting but perhaps more detail about what you're hoping to accomplish and why you are choosing these specific technologies will allow folks to get you better answers.","Q_Score":9,"Tags":"python,database,django,twisted","A_Id":5051760,"CreationDate":"2011-02-19T14:42:00.000","Title":"Sharing a database between Twisted and Django","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am trying to MySQL for Python (MySQLdb package) in Windows so that I can use it in the Django web frame.\nI have just installed MySQL Community Server 5.5.9 and I have managed to run it and test it using the testing procedures suggested in the MySQL 5.5 Reference Manual. However, I discovered that I still don't have the MySQL AB folder, the subsequent MySQL Server 5.5 folder and regkey in the HKEY_LOCAL_MACHINE, which is needed to build the MySQLdb package.\nFrom the MySQL 5.5 Reference Manual, it says that:\n\nThe MySQL Installation Wizard creates one Windows registry key in a typical install situation, located in HKEY_LOCAL_MACHINE\\SOFTWARE\\MySQL AB.\n\nHowever, I do have the Start Menu short cut and all the program files installed. I have used the msi installation and installed without problems. Should I be getting the MySQL AB folder? Does anyone know what has happened and how I should get the MySQL AB\/MySQL Server 5.5 folder and the regkey?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":854,"Q_Id":5059883,"Users Score":2,"Answer":"I found that the key was actually generated under HKEY_CURRENT_USER instead of HKEY_LOCAL_MACHINE. Thanks.","Q_Score":5,"Tags":"python,mysql,django","A_Id":5412380,"CreationDate":"2011-02-20T20:43:00.000","Title":"MySQL AB, MySQL Server 5.5 Folder in HKEY_LOCAL_MACHINE not present","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm creating a small website with Django, and I need to calculate statistics with data taken from several tables in the database.\nFor example (nothing to do with my actual models), for a given user, let's say I want all birthday parties he has attended, and people he spoke with in said parties. For this, I would need a wide query, accessing several tables.\nNow, from the object-oriented perspective, it would be great if the User class implemented a method that returned that information. From a database model perspective, I don't like at all the idea of adding functionality to a \"row instance\" that needs to query other tables. I would like to keep all properties and methods in the Model classes relevant to that single row, so as to avoid scattering the business logic all over the place.\nHow should I go about implementing database-wide queries that, from an object-oriented standpoint, belong to a single object? Should I have an external kinda God-object that knows how to collect and organize this information? Or is there a better, more elegant solution?","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":110,"Q_Id":5063658,"Users Score":1,"Answer":"I recommend extending Django's Model-Template-View approach with a controller. I usually have a controller.py within my apps which is the only interface to the data sources. So in your above case I'd have something like get_all_parties_and_people_for_user(user).\nThis is especially useful when your \"data taken from several tables in the database\" becomes \"data taken from several tables in SEVERAL databases\" or even \"data taken from various sources, e.g. databases, cache backends, external apis, etc.\".","Q_Score":3,"Tags":"python,database,django,django-models,coding-style","A_Id":5064564,"CreationDate":"2011-02-21T08:17:00.000","Title":"Correct way of implementing database-wide functionality","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm creating a small website with Django, and I need to calculate statistics with data taken from several tables in the database.\nFor example (nothing to do with my actual models), for a given user, let's say I want all birthday parties he has attended, and people he spoke with in said parties. For this, I would need a wide query, accessing several tables.\nNow, from the object-oriented perspective, it would be great if the User class implemented a method that returned that information. From a database model perspective, I don't like at all the idea of adding functionality to a \"row instance\" that needs to query other tables. I would like to keep all properties and methods in the Model classes relevant to that single row, so as to avoid scattering the business logic all over the place.\nHow should I go about implementing database-wide queries that, from an object-oriented standpoint, belong to a single object? Should I have an external kinda God-object that knows how to collect and organize this information? Or is there a better, more elegant solution?","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":110,"Q_Id":5063658,"Users Score":0,"Answer":"User.get_attended_birthday_parties() or Event.get_attended_parties(user) work fine: it's an interface that makes sense when you use it. Creating an additional \"all-purpose\" object will not make your code cleaner or easier to maintain.","Q_Score":3,"Tags":"python,database,django,django-models,coding-style","A_Id":5065280,"CreationDate":"2011-02-21T08:17:00.000","Title":"Correct way of implementing database-wide functionality","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"So I am trying to take a large number of xml files (None are that big in particular and I can split them up as I see fit.) In all there is about 70GB worth of data. For the sake of reference the loading script is written in python and uses psycopg2 to interface with a postgres table. \nAnyway, what I am trying to do is to deal with data that works something like this. The relation count being the number of time the two tags are seen together and the tag count being the number of time the tag has been seen. I have all the tags already its just getting the times they appear and the times they appear together of the xml that has become a problem.\n         Tag Table                |              Relations Table              \n TagID      TagName   TagCount    |         tag1       tag2    relationCount  \n   1         Dogs        20       |          1           2            5  \n   2         Beagles     10       |          1           3            2  \n   3         Birds       11       |          2           3            7  \nThe problem I am encountering is getting the data to load in a reasonable amount of time. I have been iterating over the update methods as I count how often the tags come up in the xml files.\nI suppose I am asking if anyone has any ideas. Should I create some sort of buffer to hold the update info and try to use cur.executeall() periodically and\/or should I restructure the database somehow. Anyway, any and all thoughts on this issue are appreciated.","AnswerCount":1,"Available Count":1,"Score":0.537049567,"is_accepted":false,"ViewCount":126,"Q_Id":5066569,"Users Score":3,"Answer":"If I understand this \"...I have been iterating over the update methods\" it sounds like you are updating the database rows as you go?  If this is so, consider writing some code that passes the XML, accumulates the totals you are tracking, outputs them to a file, and then loads that file with COPY.\nIf you are updating existing data, try something like this:\n1) Pass the XML file(s) to generate all new totals from the new data\n2) COPY that into a working table - a table that you clear out before and after every batch\n3) Issue an INSERT from the working table to the real tables for all rows that cannot be found, inserting zeros for all values\n4) Issue an UPDATE from the working table to the real tables to increment the counters.\n5) Truncate the working table.","Q_Score":0,"Tags":"python,database-design,postgresql,psycopg2","A_Id":5066699,"CreationDate":"2011-02-21T13:30:00.000","Title":"Efficiently creating a database to analyze relationships between information","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am using Python 2.7 and trying to get a Django project running on a MySQL backend.\nI have downloaded mysqldb and followed the guide here:http:\/\/cd34.com\/blog\/programming\/python\/mysql-python-and-snow-leopard\/\nYet when I go to run the django project the following traceback occurs:\n\nTraceback (most recent call last):\n  File \"\/Users\/andyarmstrong\/Documents\/workspace\/BroadbandMapper\/src\/BroadbandMapper\/manage.py\", line 11, in \n    execute_manager(settings)\n  File \"\/Library\/Frameworks\/Python.framework\/Versions\/2.7\/lib\/python2.7\/site-packages\/django\/core\/management\/__init__.py\", line 438, in execute_manager\n    utility.execute()\n  File \"\/Library\/Frameworks\/Python.framework\/Versions\/2.7\/lib\/python2.7\/site-packages\/django\/core\/management\/__init__.py\", line 379, in execute\n    self.fetch_command(subcommand).run_from_argv(self.argv)\n  File \"\/Library\/Frameworks\/Python.framework\/Versions\/2.7\/lib\/python2.7\/site-packages\/django\/core\/management\/base.py\", line 191, in run_from_argv\n    self.execute(*args, **options.__dict__)\n  File \"\/Library\/Frameworks\/Python.framework\/Versions\/2.7\/lib\/python2.7\/site-packages\/django\/core\/management\/base.py\", line 209, in execute\n    translation.activate('en-us')\n  File \"\/Library\/Frameworks\/Python.framework\/Versions\/2.7\/lib\/python2.7\/site-packages\/django\/utils\/translation\/__init__.py\", line 66, in activate\n    return real_activate(language)\n  File \"\/Library\/Frameworks\/Python.framework\/Versions\/2.7\/lib\/python2.7\/site-packages\/django\/utils\/functional.py\", line 55, in _curried\n    return _curried_func(*(args+moreargs), **dict(kwargs, **morekwargs))\n  File \"\/Library\/Frameworks\/Python.framework\/Versions\/2.7\/lib\/python2.7\/site-packages\/django\/utils\/translation\/__init__.py\", line 36, in delayed_loader\n    return getattr(trans, real_name)(*args, **kwargs)\n  File \"\/Library\/Frameworks\/Python.framework\/Versions\/2.7\/lib\/python2.7\/site-packages\/django\/utils\/translation\/trans_real.py\", line 193, in activate\n    _active[currentThread()] = translation(language)\n  File \"\/Library\/Frameworks\/Python.framework\/Versions\/2.7\/lib\/python2.7\/site-packages\/django\/utils\/translation\/trans_real.py\", line 176, in translation\n    default_translation = _fetch(settings.LANGUAGE_CODE)\n  File \"\/Library\/Frameworks\/Python.framework\/Versions\/2.7\/lib\/python2.7\/site-packages\/django\/utils\/translation\/trans_real.py\", line 159, in _fetch\n    app = import_module(appname)\n  File \"\/Library\/Frameworks\/Python.framework\/Versions\/2.7\/lib\/python2.7\/site-packages\/django\/utils\/importlib.py\", line 35, in import_module\n    __import__(name)\n  File \"\/Library\/Frameworks\/Python.framework\/Versions\/2.7\/lib\/python2.7\/site-packages\/django\/contrib\/admin\/__init__.py\", line 1, in \n    from django.contrib.admin.helpers import ACTION_CHECKBOX_NAME\n  File \"\/Library\/Frameworks\/Python.framework\/Versions\/2.7\/lib\/python2.7\/site-packages\/django\/contrib\/admin\/helpers.py\", line 1, in \n    from django import forms\n  File \"\/Library\/Frameworks\/Python.framework\/Versions\/2.7\/lib\/python2.7\/site-packages\/django\/forms\/__init__.py\", line 17, in \n    from models import *\n  File \"\/Library\/Frameworks\/Python.framework\/Versions\/2.7\/lib\/python2.7\/site-packages\/django\/forms\/models.py\", line 6, in \n    from django.db import connections\n  File \"\/Library\/Frameworks\/Python.framework\/Versions\/2.7\/lib\/python2.7\/site-packages\/django\/db\/__init__.py\", line 77, in \n    connection = connections[DEFAULT_DB_ALIAS]\n  File \"\/Library\/Frameworks\/Python.framework\/Versions\/2.7\/lib\/python2.7\/site-packages\/django\/db\/utils.py\", line 92, in __getitem__\n    backend = load_backend(db['ENGINE'])\n  File \"\/Library\/Frameworks\/Python.framework\/Versions\/2.7\/lib\/python2.7\/site-packages\/django\/db\/utils.py\", line 33, in load_backend\n    return import_module('.base', backend_name)\n  File \"\/Library\/Frameworks\/Python.framework\/Versions\/2.7\/lib\/python2.7\/site-packages\/django\/utils\/importlib.py\", line 35, in import_module\n    __import__(name)\n  File \"\/Library\/Frameworks\/Python.framework\/Versions\/2.7\/lib\/python2.7\/site-packages\/django\/db\/backends\/mysql\/base.py\", line 14, in \n    raise ImproperlyConfigured(\"Error loading MySQLdb module: %s\" % e)\ndjango.core.exceptions.ImproperlyConfigured: Error loading MySQLdb module: dlopen(\/Users\/andyarmstrong\/.python-eggs\/MySQL_python-1.2.3-py2.7-macosx-10.6-x86_64.egg-tmp\/_mysql.so, 2): Library not loaded: libmysqlclient.16.dylib\n  Referenced from: \/Users\/andyarmstrong\/.python-eggs\/MySQL_python-1.2.3-py2.7-macosx-10.6-x86_64.egg-tmp\/_mysql.so\n  Reason: image not found\n\nI have tried the following also:http:\/\/whereofwecannotspeak.wordpress.com\/2007\/11\/02\/mysqldb-python-module-quirk-in-os-x\/\nadding a link between the mysql lib directory and somewhere else...\nHelp!","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":1535,"Q_Id":5072066,"Users Score":2,"Answer":"I eventually managed to solve the problem by Installing python 2.7 with Mac Ports and installing mysqldb using Mac Ports - was pretty simple after that.","Q_Score":2,"Tags":"python,mysql,django,macos","A_Id":5072940,"CreationDate":"2011-02-21T22:35:00.000","Title":"Python mysqldb on Mac OSX 10.6 not working","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I am using Python 2.7 and trying to get a Django project running on a MySQL backend.\nI have downloaded mysqldb and followed the guide here:http:\/\/cd34.com\/blog\/programming\/python\/mysql-python-and-snow-leopard\/\nYet when I go to run the django project the following traceback occurs:\n\nTraceback (most recent call last):\n  File \"\/Users\/andyarmstrong\/Documents\/workspace\/BroadbandMapper\/src\/BroadbandMapper\/manage.py\", line 11, in \n    execute_manager(settings)\n  File \"\/Library\/Frameworks\/Python.framework\/Versions\/2.7\/lib\/python2.7\/site-packages\/django\/core\/management\/__init__.py\", line 438, in execute_manager\n    utility.execute()\n  File \"\/Library\/Frameworks\/Python.framework\/Versions\/2.7\/lib\/python2.7\/site-packages\/django\/core\/management\/__init__.py\", line 379, in execute\n    self.fetch_command(subcommand).run_from_argv(self.argv)\n  File \"\/Library\/Frameworks\/Python.framework\/Versions\/2.7\/lib\/python2.7\/site-packages\/django\/core\/management\/base.py\", line 191, in run_from_argv\n    self.execute(*args, **options.__dict__)\n  File \"\/Library\/Frameworks\/Python.framework\/Versions\/2.7\/lib\/python2.7\/site-packages\/django\/core\/management\/base.py\", line 209, in execute\n    translation.activate('en-us')\n  File \"\/Library\/Frameworks\/Python.framework\/Versions\/2.7\/lib\/python2.7\/site-packages\/django\/utils\/translation\/__init__.py\", line 66, in activate\n    return real_activate(language)\n  File \"\/Library\/Frameworks\/Python.framework\/Versions\/2.7\/lib\/python2.7\/site-packages\/django\/utils\/functional.py\", line 55, in _curried\n    return _curried_func(*(args+moreargs), **dict(kwargs, **morekwargs))\n  File \"\/Library\/Frameworks\/Python.framework\/Versions\/2.7\/lib\/python2.7\/site-packages\/django\/utils\/translation\/__init__.py\", line 36, in delayed_loader\n    return getattr(trans, real_name)(*args, **kwargs)\n  File \"\/Library\/Frameworks\/Python.framework\/Versions\/2.7\/lib\/python2.7\/site-packages\/django\/utils\/translation\/trans_real.py\", line 193, in activate\n    _active[currentThread()] = translation(language)\n  File \"\/Library\/Frameworks\/Python.framework\/Versions\/2.7\/lib\/python2.7\/site-packages\/django\/utils\/translation\/trans_real.py\", line 176, in translation\n    default_translation = _fetch(settings.LANGUAGE_CODE)\n  File \"\/Library\/Frameworks\/Python.framework\/Versions\/2.7\/lib\/python2.7\/site-packages\/django\/utils\/translation\/trans_real.py\", line 159, in _fetch\n    app = import_module(appname)\n  File \"\/Library\/Frameworks\/Python.framework\/Versions\/2.7\/lib\/python2.7\/site-packages\/django\/utils\/importlib.py\", line 35, in import_module\n    __import__(name)\n  File \"\/Library\/Frameworks\/Python.framework\/Versions\/2.7\/lib\/python2.7\/site-packages\/django\/contrib\/admin\/__init__.py\", line 1, in \n    from django.contrib.admin.helpers import ACTION_CHECKBOX_NAME\n  File \"\/Library\/Frameworks\/Python.framework\/Versions\/2.7\/lib\/python2.7\/site-packages\/django\/contrib\/admin\/helpers.py\", line 1, in \n    from django import forms\n  File \"\/Library\/Frameworks\/Python.framework\/Versions\/2.7\/lib\/python2.7\/site-packages\/django\/forms\/__init__.py\", line 17, in \n    from models import *\n  File \"\/Library\/Frameworks\/Python.framework\/Versions\/2.7\/lib\/python2.7\/site-packages\/django\/forms\/models.py\", line 6, in \n    from django.db import connections\n  File \"\/Library\/Frameworks\/Python.framework\/Versions\/2.7\/lib\/python2.7\/site-packages\/django\/db\/__init__.py\", line 77, in \n    connection = connections[DEFAULT_DB_ALIAS]\n  File \"\/Library\/Frameworks\/Python.framework\/Versions\/2.7\/lib\/python2.7\/site-packages\/django\/db\/utils.py\", line 92, in __getitem__\n    backend = load_backend(db['ENGINE'])\n  File \"\/Library\/Frameworks\/Python.framework\/Versions\/2.7\/lib\/python2.7\/site-packages\/django\/db\/utils.py\", line 33, in load_backend\n    return import_module('.base', backend_name)\n  File \"\/Library\/Frameworks\/Python.framework\/Versions\/2.7\/lib\/python2.7\/site-packages\/django\/utils\/importlib.py\", line 35, in import_module\n    __import__(name)\n  File \"\/Library\/Frameworks\/Python.framework\/Versions\/2.7\/lib\/python2.7\/site-packages\/django\/db\/backends\/mysql\/base.py\", line 14, in \n    raise ImproperlyConfigured(\"Error loading MySQLdb module: %s\" % e)\ndjango.core.exceptions.ImproperlyConfigured: Error loading MySQLdb module: dlopen(\/Users\/andyarmstrong\/.python-eggs\/MySQL_python-1.2.3-py2.7-macosx-10.6-x86_64.egg-tmp\/_mysql.so, 2): Library not loaded: libmysqlclient.16.dylib\n  Referenced from: \/Users\/andyarmstrong\/.python-eggs\/MySQL_python-1.2.3-py2.7-macosx-10.6-x86_64.egg-tmp\/_mysql.so\n  Reason: image not found\n\nI have tried the following also:http:\/\/whereofwecannotspeak.wordpress.com\/2007\/11\/02\/mysqldb-python-module-quirk-in-os-x\/\nadding a link between the mysql lib directory and somewhere else...\nHelp!","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":1535,"Q_Id":5072066,"Users Score":0,"Answer":"you needed to add the MySQL client libraries to the LD_LIBRARY_PATH.","Q_Score":2,"Tags":"python,mysql,django,macos","A_Id":5305496,"CreationDate":"2011-02-21T22:35:00.000","Title":"Python mysqldb on Mac OSX 10.6 not working","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I'm building my first app with GAE to allow users to run elections, and I create an Election entity for each election.  \nTo avoid storing too much data, I'd like to automatically delete an Election entity after a certain period of time -- say three months after the end of the election.  Is it possible to do this automatically in GAE?  Or do I need to do this manually?\nIf it matters, I'm using the Python interface.","AnswerCount":3,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":2483,"Q_Id":5079885,"Users Score":5,"Answer":"Assuming you have a DateProperty on the entities indicating when the election ended, you can have a cron job search for any older than 3 months every night and delete them.","Q_Score":3,"Tags":"python,google-app-engine,google-cloud-datastore","A_Id":5079939,"CreationDate":"2011-02-22T15:09:00.000","Title":"Automatic deletion or expiration of GAE datastore entities","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I know that if I figure this one out or if somebody shows me, it'll be a forehead slapper. Before posting any questions, I try for at least three hours and quite a bit of searching. There are several hints that are close, but nothing I have adopted\/tried seems to work.\nI am taking a byte[] from Java and passing that via JSON (with Gson) to a python JSON using Flask. This byte[] is stored in a python object as an integer list when received, but now I need to send it to MySQLdb and store it as a blob. The data contents is binary file data.\nHow do I convert a python integer list [1,2,-3,-143....] to something that I can store in MySQL? I have tried bytearray() and array.array(), but those choke when I access the list directly from the object and try and convert to a string to store thorugh MySQLdb.\nAny links or hints are greatly appreciated.","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":7408,"Q_Id":5088671,"Users Score":0,"Answer":"I found ''.join(map(lambda x: chr(x % 256), data)) to be painfully slow (~4 minutes) for my data on python 2.7.9, where a small change to str(bytearray(map(lambda x: chr(x % 256), data))) only took about 10 seconds.","Q_Score":1,"Tags":"java,python,mysql,binary,byte","A_Id":31187500,"CreationDate":"2011-02-23T08:47:00.000","Title":"Convert Java byte array to Python byte array","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have installed MySqldb through .exe(precompiled). Its is stored in site-packages. But now i don't know how to test, that it is accessable or not. And major problem how to import in my application like import MySqldb. Help me i am very new techie in python i just want to work with my existing Mysql. Thanks in advance...","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":165,"Q_Id":5090870,"Users Score":3,"Answer":"Just open your CMD\/Console, type python, press Enter, type import MySQLdb and then press Enter again.\nIf no error is shown, you're ok!","Q_Score":0,"Tags":"python,mysql","A_Id":5090944,"CreationDate":"2011-02-23T12:23:00.000","Title":"how to import mysqldb","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I want to retain the flexibility of switching between MySQL and PostgreSQL without the awkwardness of using an ORM - SQL is a fantastic language and i would like to retain it's power without the additional overhead of an ORM.\nSo...is there a best practice for abstraction the database layer of a Python application to provide the stated flexibility.\nThanks community!","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":965,"Q_Id":5090901,"Users Score":1,"Answer":"Have a look at SQLAlchemy. You can use it to execute literal SQL on several RDBMS, including MySQL and PostgreSQL. It wraps the DB-API adapters with a common interface, so they will behave as similarly as possible.\nSQLAlchemy also offers programmatic generation of SQL, with or without the included ORM, which you may find very useful.","Q_Score":1,"Tags":"python,mysql,database,postgresql,abstraction","A_Id":5090938,"CreationDate":"2011-02-23T12:25:00.000","Title":"Starting new project: database abstraction in Python, best practice for retaining option of MySQL or PostgreSQL without ORM","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm looking for a library that lets me run SQL-like queries on python \"object databases\".  With object database I mean a fairly complex structure of python objects and lists in memory. Basically this would be a \"reverse ORM\" - instead of providing an object oriented interface to a relational database, it would provide a SQL-ish interface to an object database.\nC#'s LINQ is very close. Python's list comprehensions are very nice, but the syntax gets hairy when doing complex things (sorting, joining, etc.). Also, I can't (easily) create queries dynamically with list comprehensions.\nThe actual syntax could either be string based, or use a object-oriented DSL (a la from(mylist).select(...)). Bonus points if the library would provide some kind of indices to speed up search.\nDoes this exist or do I have to invent it?","AnswerCount":7,"Available Count":1,"Score":0.057080742,"is_accepted":false,"ViewCount":9831,"Q_Id":5126776,"Users Score":2,"Answer":"One major difference between what SQL does and what you can do in idiomatic python, in SQL, you tell the evaluator what information you are looking for, and it works out the most efficient way of retrieving that based on the structure of the data it holds.  In python, you can only tell the interpreter how you want the data, there's no equivalent to a query planner.\nThat said, there are a few extra tools above and beyond list comprehensions that help alot.  \nFirst, use a structure that closely resembles the declarative nature of SQL.  Many of them are builtins.  map, filter, reduce, zip, all, any, sorted, as well as the contents of the operator, functools and itertools packages, all offer a fairly concise way of expressing data queries.","Q_Score":17,"Tags":"python,object-oriented-database","A_Id":5127794,"CreationDate":"2011-02-26T12:03:00.000","Title":"Query language for python objects","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have three tables, 1-Users, 2-Softwares, 3-UserSoftwares.\nif suppose, Users table having 6 user records(say U1,U2,...,U6) and Softwares table having 4 different softwares(say S1,S2,S3,S4) and UserSoftwares stores the references if a user requested for given software only.\nFor example: UserSoftwares(5 records) have only two columns(userid, softwareid) which references others. and the data is:\nU1   S1\nU2   S2\nU2   S3\nU3   S3\nU4   S1\nNow I m expecting following results:(if current login user is U2):\n\nS1  Disable\nS2  Enable\nS3  Enable\nS4  Disable\nHere, 1st column is softwareid or name and 2nd column is status which having only two values(Enable\/Disable) based on UserSoftwares table(model). Note status is not a field of any model(table).\n\"My Logic is: \n1. loop through each software in softwares model\n2. find softwareid with current login userid (U2) in UserSoftwares model: \n    if it found then set status='Enable'\n    if not found then set status='Disable'\n3. add this status property to software object.\n4. repeat this procedure for all softwares. \n\"\nWhat should be the query in python google app engine to achieve above result?","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":873,"Q_Id":5142192,"Users Score":0,"Answer":"If your are looking for join - there is no joins in GAE. BTW, there is pretty easy to make 2 simple queries (Softwares and UserSoftware), and calculate all additional data manually","Q_Score":1,"Tags":"python,google-app-engine,model","A_Id":5143851,"CreationDate":"2011-02-28T12:48:00.000","Title":"Querying on multiple tables using google apps engine (Python)","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I had a postgresql query where I need to take column defined as character from table and then pass this value to the function where it only accepts integer.So in this case, how can i solve the problem??Can anyone help??","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":126,"Q_Id":5148790,"Users Score":0,"Answer":"ord(val) will give you the integer value of a character. int(val) will cast a value into an integer.","Q_Score":0,"Tags":"python,casting","A_Id":5148795,"CreationDate":"2011-02-28T23:23:00.000","Title":"how to convert value of column defined as character into integer in python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"As part of artifacts delivery, our developers give the data and structure scripts in .sql files. I usually \"double click\" on these files to open in \"Microsoft SQL Server Management Studio\". Management studio will prompt me for entering database server and user\/pwd. I enter them manually and click on Execute button to execute these scripts.\nThese scripts contain structure and data sql commands. Each script may contain more than one data command (like select, insert, update, etc). Structure and data scripts are provided in separate .sql files.\nThese scripts also contain stored procedures and functions, etc. They also contain comments \/ description.\nI want to automate execution of these scripts through python. I looked at pyodbc and pymssql but they dont look like solve my issue.\nThrough pyodbc, i need to read each .sql file and read the sql commands and execute them one by one. As the files may have comments \/ description \/ SPs \/ etc, reading the files will be little difficult.\nCan anyone give suggestion on how to automate this?\nThanks in advance.","AnswerCount":2,"Available Count":1,"Score":0.3799489623,"is_accepted":false,"ViewCount":3938,"Q_Id":5174269,"Users Score":4,"Answer":"You could just run them using sqlcmd. Sqlcmd is a command line utility that will let you run .sql scripts from the command line, which I'm sure you can kick off through python.","Q_Score":1,"Tags":"python,sql,sql-server","A_Id":5174307,"CreationDate":"2011-03-02T22:22:00.000","Title":"Execute .sql files that are used to run in SQL Management Studio in python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm using SQLAlchemy 0.6.6 against a Postgres 8.3 DB on Windows 7 an PY 2.6.  I am leaving the defaults for configuring pooling when I create my engine, which is pool_size=5, max_overflow=10.\nFor some reason, the connections keep piling up and I intermittently get \"Too many clients\" from PG.  I am positive that connections are being closed in a finally block as this application is only accessed via WSGI (CherryPy) and uses a connection\/request pattern. I am also logging when connections are being closed just to make sure.\nI've tried to see what's going on by adding echo_pool=true during my engine creation, but nothing is being logged.  I can see SQL statement rolling through the console when I set echo=True, but nothing for pooling.\nAnyway, this is driving me crazy because my co-worker who is on a Mac doesn't have any of these issues (I know, get a Mac), so I'm trying to see if this is the result of a bug or something.  Google has yielded nothing so I'm hoping to get some help here.\nThanks,\ncc","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1198,"Q_Id":5185438,"Users Score":0,"Answer":"Turns out there was ScopedSession being used outside the normal application usage and the close wasn't in a finally.","Q_Score":1,"Tags":"python,postgresql,sqlalchemy,connection-pooling,cherrypy","A_Id":5195465,"CreationDate":"2011-03-03T19:21:00.000","Title":"SQLAlchemy Connection Pooling Problems - Postgres on Windows","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have about 30 MB of textual data that is core to the algorithms I use in my web application.\nOn the one hand, the data is part of the algorithm and changes to the data can cause an entire algorithm to fail. This is why I keep the data in text files in my source control, and all changes are auto-tested (pre-commit). I currently have a good level of control. Distributing the data along with the source as we spawn more web instances is a non-issue because it tags along with the source. I currently have these problems:\n\nI often develop special tools to manipulate the files, replicating database access tool functionality\nI would like to give non-developers controlled web-access to this data.\n\nOn the other hand, it is data, and it \"belongs\" in a database. I wish I could place it in a database, but then I would have these problems:\n\nHow do I sync this database to the source? A release contains both code and data.\nHow do I ship it with the data as I spawn a new instance of the web server?\nHow do I manage pre-commit testing of the data? \n\nThings I have considered thus-far:\n\nSqlite (does not solve the non-developer access)\nBuilding an elaborate pre-production database, which data-users will edit to create \"patches\" to the \"real\" database, which developers will accept, test and commit. Sounds very complex.\nI have not fully designed this yet and I sure hope I'm reinventing the wheel here and some SO user will show me the error of my ways...\n\nBTW: I have a \"regular\" database as well, with things that are not algorithmic-data.\nBTW2: I added the Python tag because I currently use Python, Django, Apache and Nginx, Linux (and some lame developers use Windows).  \nThanks in advance!\nUPDATE\nSome examples of the data (the algorithms are natural language processing stuff):\n\nWorld Cities and their alternate names\nNames of currencies\nCoordinates of hotels\n\nThe list goes on and on, but Imagine trying to parse the sentence Romantic hotel for 2 in Rome arriving in Italy next monday if someone changes the coordinates that teach me that Rome is in Italy, or if someone adds `romantic' as an alternate name for Las Vegas (yes, the example is lame, but I hope you get the drift).","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":127,"Q_Id":5210318,"Users Score":1,"Answer":"Okay, here's an idea:\n\nShip all the data as is done now.\nHave the installation script install it in the appropriate databases.\nLet users modify this database and give them a button \"restore to original\" that simply reinstalls from the text file.\n\nAlternatively, this route may be easier, esp. when upgrading an installation:\n\nShip all the data as is done now.\nLet users modify the data and store the modified versions in the appropriate database.\nLet the code look in the database, falling back to the text files if the appropriate data is not found. Don't let the code modify the text files in any way.\n\nIn either case, you can keep your current testing code; you just need to add tests that make sure the database properly overrides text files.","Q_Score":4,"Tags":"python","A_Id":5210383,"CreationDate":"2011-03-06T11:56:00.000","Title":"What's the best way to handle source-like data files in a web application?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm not sure if this is an issue specific to sqlite databases but after adding some properties I executed syncdb successfully but still the the columns were not added to the database and when I try the access the model in admin I get no such column error.\nWhy is this happening and how do I overcome this issue?\nDetails: Django 1.3, Python 2.6, OSX 10.6, PyCharm.","AnswerCount":3,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":5639,"Q_Id":5211340,"Users Score":3,"Answer":"As always, syncdb does not migrate the existing schema.","Q_Score":4,"Tags":"python,django,sqlite","A_Id":5211417,"CreationDate":"2011-03-06T15:26:00.000","Title":"Django manage.py syncdb doing nothing when used with sqlite3","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am trying to modify the guestbook example webapp to reduce the amount of database writes.\nWhat I am trying to achieve is to load all the guestbook entries into memcache which I have done. \nHowever I want to be able to directly update the memcache with new guestbook entries and then write all changes to the database as a batch put.() every 30 seconds.\nHas anyone got an example of how I could achieve the above? it would really help me!\nThanks :)","AnswerCount":3,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1124,"Q_Id":5221977,"Users Score":6,"Answer":"This is a recipe for lost data. I have a hard time believing that a guest book is causing enough write activity to be an issue. Also, the bookkeeping involved in this would be tricky, since memcache isn't searchable.","Q_Score":2,"Tags":"python,google-app-engine,caching,memcached,google-cloud-datastore","A_Id":5222081,"CreationDate":"2011-03-07T16:12:00.000","Title":"Limit amount of writes to database using memcache","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I'm using sqlalchemy with reflection, a couple of partial indices in my DB make it dump warnings like this:\nSAWarning: Predicate of partial index i_some_index ignored during reflection\ninto my logs and keep cluttering. It does not hinder my application behavior. I would like to keep these warnings while developing, but not at production level. Does anyone know how to turn this off?","AnswerCount":2,"Available Count":1,"Score":1.0,"is_accepted":false,"ViewCount":14820,"Q_Id":5225780,"Users Score":12,"Answer":"the warning means you did a table or metadata reflection, and it's reading in postgresql indexes that have some complex condition which the SQLAlchemy reflection code doesn't know what to do with.   This is a harmless warning, as whether or not indexes are reflected doesn't affect the operation of the application, unless you wanted to re-emit CREATE statements for those tables\/indexes on another database.","Q_Score":35,"Tags":"python,postgresql,sqlalchemy","A_Id":5331129,"CreationDate":"2011-03-07T22:00:00.000","Title":"Turn off a warning in sqlalchemy","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm working on a client machine running suse linux and python 2.4.2. I'm not allowed to dowload anything from the net including any external libraries. So, is there any way I can connect to a database (oracle) using only the default libraries?","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":360,"Q_Id":5228728,"Users Score":1,"Answer":"No. There is nothing in the standard library for connecting to database servers.","Q_Score":0,"Tags":"python,database,oracle","A_Id":5228737,"CreationDate":"2011-03-08T05:32:00.000","Title":"Python: Connecting to db without any external libraries","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"So I have a Django web application and I need to add a payment module to it.\nBasically a user will prepay for a certain amount of service and this will slowly reduce over as the user uses the service. I'm wondering what is the best practice to facilitate this? I can process payments using Satchmo, but then just storing the USD value in a database and having my code interacting with that value directly seems kind of risky. Sure I can do that but I am wondering if there is a well tested solution to this problem out there already?","AnswerCount":2,"Available Count":2,"Score":0.0996679946,"is_accepted":false,"ViewCount":453,"Q_Id":5236855,"Users Score":1,"Answer":"My language agnostic recommendation would be to make sure that the database that communicates with the web app is read only; at least for the table(s) that deal with these account balances. So, you process payments, and manage the reduction of account balances in a database that is not accessible to anyone other than you (i.e. not connected to the internet, or this web app). You can periodically take snapshots of that database and update the one that interacts with the webapp, so your users have a read copy of their balance. This way, even if a user is able to modify the data to increase their balance by a million bucks, you know that you have their true balance in a separate location. Basically, you'd never have to trust the data on the webapp side - it would be purely informational for your users.","Q_Score":3,"Tags":"python,database,django,web-applications","A_Id":5236907,"CreationDate":"2011-03-08T18:45:00.000","Title":"Securely storing account balances in a database?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"So I have a Django web application and I need to add a payment module to it.\nBasically a user will prepay for a certain amount of service and this will slowly reduce over as the user uses the service. I'm wondering what is the best practice to facilitate this? I can process payments using Satchmo, but then just storing the USD value in a database and having my code interacting with that value directly seems kind of risky. Sure I can do that but I am wondering if there is a well tested solution to this problem out there already?","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":453,"Q_Id":5236855,"Users Score":6,"Answer":"I don't know about a \"well-tested solution\" as you put it, but I would strongly caution against just storing a dollar value in the database and increasing or decreasing that dollar value.  Instead, I would advise storing transactions that can be audited if anything goes wrong.  Calculate the amount available from the credit and debit transactions in the user account rather than storing it directly.\nFor extra safety, you would want to ensure that your application cannot delete any transaction records.  If you cannot deny write permissions on the relevant tables for some reason, try replicating the transactions to a second database (that the application does not touch) as they are created.","Q_Score":3,"Tags":"python,database,django,web-applications","A_Id":5236901,"CreationDate":"2011-03-08T18:45:00.000","Title":"Securely storing account balances in a database?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Is there a way in cx_Oracle to capture the stdout output from an oracle stored procedure? These show up when using Oracle's SQL Developer or SQL Plus, but there does not seem to be a way to fetch it using the database drivers.","AnswerCount":4,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":2934,"Q_Id":5244517,"Users Score":4,"Answer":"You can retrieve dbms_output with DBMS_OUTPUT.GET_LINE(buffer, status). Status is 0 on success and 1 when there's no more data.\nYou can also use get_lines(lines, numlines). numlines is input-output. You set it to the max number of lines and it is set to the actual number on output. You can call this in a loop and exit when the returned numlines is less than your input. lines is an output array.","Q_Score":3,"Tags":"python,oracle10g,cx-oracle","A_Id":5247755,"CreationDate":"2011-03-09T10:36:00.000","Title":"Capturing stdout output from stored procedures with cx_Oracle","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I \u00b4m trying to serialize an array in python to insert it on a database of MySQL... I try with pickle.dump() method but it returns byte... what can I use?? thanks!!\n(I \u00b4m working in python 3)","AnswerCount":4,"Available Count":1,"Score":0.049958375,"is_accepted":false,"ViewCount":1312,"Q_Id":5259329,"Users Score":1,"Answer":"Pickle is a binary serialization, that's why you get a byte string.\nPros:\n\nmore compact\ncan express most of Python's objects.\n\nCon's:\n\nbytes can be harder to handle\nPython only.\n\nJSON is more universal, so you're not tied to reading data with Python.  It's also mostly ASCII, so it's easier to handle.  the con is that it's limited to numbers, strings, arrays and dicts.  usually enough, but even datetimes have to be converted to string representation before encoding.","Q_Score":3,"Tags":"python,mysql","A_Id":5259400,"CreationDate":"2011-03-10T12:01:00.000","Title":"Serizalize an array in Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I need to use a Python ORM with a MS-Access database (in Windows).\nMy first searches are not really succesfull : \n\nSQLAlchemy : no MS Access support in the two last versions.\nDAL from Web2Py : no Access (??)\nStorm : no MS Access\nsqlobject: no MS Access\ndejavu : seems OK for MS Access but\nis the project alive ?\n\nAny ideas or informations are welcome ...","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1062,"Q_Id":5262387,"Users Score":1,"Answer":"Web2py recently updated their DAL making it much easier to add support for new db engines.  I don't believe there is currently native Jet (MS Access) support, but the existing SQL Server support could probably be modified without much effort to provide MS Access support.  The latest version of the web2py DAL is a single stand-alone .py file, so it's not a \"heavy\" package.\nFor what it's worth, I've successfully used the web2py DAL as a stand-alone module with SQL Server after initially trying and giving up on SQLAlchemy.  In fairness to SQLAlchemy, I had used the web2py DAL as part of the framework and was already comfortable with it.","Q_Score":1,"Tags":"python,ms-access,orm","A_Id":5262564,"CreationDate":"2011-03-10T16:08:00.000","Title":"Python ORM for MS-Access","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Is opening\/closing db cursor costly operation? What is the best practice, to use a different cursor or to reuse the same cursor between different sql executions? Does it matter if a transaction consists of executions performed on same or different cursors belonging to same connection? \nThanks.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":659,"Q_Id":5275236,"Users Score":1,"Answer":"This will depend a lot on your database as well as your chose python implementation - have you tried profiling a few short test operations?","Q_Score":2,"Tags":"python,database,transactions,cursor","A_Id":5275401,"CreationDate":"2011-03-11T15:58:00.000","Title":"db cursor - transaction in python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a very large dataset - millions of records - that I want to store in Python.  I might be running on 32-bit machines so I want to keep the dataset down in the hundreds-of-MB range and not ballooning much larger than that.\nThese records - represent a M:M relationship - two IDs (foo and bar) and some simple metadata like timestamps (baz).\nSome foo have too nearly all bar in them, and some bar have nearly all foo.  But there are many bar that have almost no foos and many foos that have almost no bar.\nIf this were a relational database, a M:M relationship would be modelled as a table with a compound key.  You can of course search on either component key individually comfortably.\nIf you store the rows in a hashtable, however, you need to maintain three hashtables as the compound key is hashed and you can't search on the component keys with it.\nIf you have some kind of sorted index, you can abuse lexical sorting to iterate the first key in the compound key, and need a second index for the other key; but its less obvious to me what actual data-structure in the standard Python collections this equates to.\nI am considering a dict of foo where each value is automatically moved from tuple (a single row) to list (of row tuples) to dict depending on some thresholds, and another dict of bar where each is a single foo, or a list of foo.\nAre there more efficient - speedwise and spacewise - ways of doing this?  Any kind of numpy for indices or something?\n\n(I want to store them in Python because I am having performance problems with databases - both SQL and NoSQL varieties.  You end up being IPC memcpy and serialisation-bound.  That is another story; however the key point is that I want to move the data into the application rather than get recommendations to move it out of the application ;) )","AnswerCount":4,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":240,"Q_Id":5302816,"Users Score":2,"Answer":"What you describe sounds like a sparse matrix, where the foos are along one axis and the bars along the other one.  Each non-empty cell represents a relationship between one foo and one bar, and contains the \"simple metadata\" you describe.\nThere are efficient sparse matrix packages for Python (scipy.sparse, PySparse) you should look at.  I found these two just by Googling \"python sparse matrix\".\nAs to using a database, you claim that you've had performance problems.  I'd like to suggest that you may not have chosen an optimal representation, but without more details on what your access patterns look like, and what database schema you used, it's awfully hard for anybody to contribute useful help.  You might consider editing your post to provide more information.","Q_Score":1,"Tags":"python,data-structures","A_Id":5303400,"CreationDate":"2011-03-14T18:34:00.000","Title":"Efficient large dicts of dicts to represent M:M relationships in Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"When I put my database file (which is a .sdb) into a directory and try to access it from that directory, I receive an error. The error reads \"unable to open database file\". For example, let's say my .sdb file is in the \"data\" directory and I use the command \"con = lite.connect('data\\noktalar.sdb')\", this error occurs. Why is that so?\nThanks.","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":324,"Q_Id":5321699,"Users Score":1,"Answer":"Where is your python process running from? Try to point to the absolute path of the file. And when pointing to path use raw string r'c:\\\\mypath\\data\\notktalar.sub'","Q_Score":3,"Tags":"python,sqlite","A_Id":5321757,"CreationDate":"2011-03-16T06:14:00.000","Title":"Python Database Error","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm using the Python version of Google App Engine and Datastore.  What is a good way to load a table that will contain lookup data?\nBy look up data I mean that after the initial load no rows will need to be inserted, deleted, or updated\nBlowing away all rows and reloading the table is not acceptable if it destroys referential integrity with other rows referring to it.\nHere is an example of a couple kinds that I am using that I want to load lookup data into\nclass Badge(db.Model):\n    name = db.StringProperty()\n    level = db.IntegerProperty()\n\nclass Achievement(db.Model):\n    name = db.StringProperty()\n    level = db.IntegerProperty()\n    badge = db.ReferenceProperty(reference_class=Badge)\n\nHere is an example of a kind not holding look up data but referring to it\nclass CamperAchievement(db.Model):\n    camper = db.ReferenceProperty(reference_class=Camper)\n    achievement = db.ReferenceProperty(reference_class=Achievement)\n    session = db.ReferenceProperty(reference_class=Session)\n    passed = db.BooleanProperty(default=True)\nI'm looking to find out two things:\nWhat should the code to load the data look like?\nWhat should trigger the loading code to execute?","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":319,"Q_Id":5328112,"Users Score":2,"Answer":"If it's really created once and never changes within the lifetime of a deployment, and it's relatively small (a few megs or less), store it with your app as data files. Have the app load the data into memory initially, and cache it there.","Q_Score":2,"Tags":"python,google-app-engine,google-cloud-datastore","A_Id":5331814,"CreationDate":"2011-03-16T16:05:00.000","Title":"Need Pattern for lookup tables in Google App Engine","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm designing a python application which works with a database. I'm planning to use sqlite.\nThere are 15000 objects, and each object has a few attributes. every day I need to add some data for each object.(Maybe create a column with the date as its name).\nHowever, I would like to easily delete the data which is too old but it is very hard to delete columns using sqlite(and it might be slow because I need to copy the required columns and then delete the old table)\nIs there a better way to organize this data other than creating a column for every date? Or should I use something other than sqlite?","AnswerCount":3,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":113,"Q_Id":5335330,"Users Score":0,"Answer":"If your database is pretty much a collection of almost-homogenic data, you could as well go for a simpler key-value database. If the main action you perform on the data is scanning through everything, it would perform significantly better.\nPython library has bindings for popular ones as \"anydbm\". There is also a dict-imitating proxy over anydbm in shelve. You could pickle your objects with the attributes using any serializer you want (simplejson, yaml, pickle)","Q_Score":0,"Tags":"python,sqlite,data-modeling","A_Id":5339473,"CreationDate":"2011-03-17T05:42:00.000","Title":"Please help me design a database schema for this:","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm designing a python application which works with a database. I'm planning to use sqlite.\nThere are 15000 objects, and each object has a few attributes. every day I need to add some data for each object.(Maybe create a column with the date as its name).\nHowever, I would like to easily delete the data which is too old but it is very hard to delete columns using sqlite(and it might be slow because I need to copy the required columns and then delete the old table)\nIs there a better way to organize this data other than creating a column for every date? Or should I use something other than sqlite?","AnswerCount":3,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":113,"Q_Id":5335330,"Users Score":0,"Answer":"For that size of a db, I would use something else. I've used sqlite once for a media library with about 10k objects and it was slow, like 5 minutes to query it all and display, searches were :\/, switching to postgres made life so much easier.  This is just on the performance issue only.\nIt also might be better to create an index that contains the date and the data\/column you want to add and a pk reference to the object it belongs and use that for your deletions instead of altering the table all the time. This can be done in sqlite if you give the pk an int type and save the pk of the object to it, instead of using a Foreign Key like you would with mysql\/postgres.","Q_Score":0,"Tags":"python,sqlite,data-modeling","A_Id":5335386,"CreationDate":"2011-03-17T05:42:00.000","Title":"Please help me design a database schema for this:","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"is it possible to Insert a python tuple  in a postgresql database","AnswerCount":4,"Available Count":2,"Score":0.049958375,"is_accepted":false,"ViewCount":4015,"Q_Id":5342359,"Users Score":1,"Answer":"Really we need more information. What data is inside the tuple? Is it just integers? Just strings? Is it megabytes of images?\nIf you had a Python tuple like (4,6,2,\"Hello\",7) you could insert the string '(4,6,2,\"Hello\",7)' into a Postgres database, but that's probably not the answer you're looking for.\nYou really need to figure out what data you're really trying to store before you can figure out how\/where to store it.\n\nEDIT: So the short answer is \"no\", you cannot store an arbitrary Python tuple in a postgres database, but there's probably some way to take whatever is inside the tuple and store it somewhere useful.","Q_Score":0,"Tags":"python,database,postgresql","A_Id":5342409,"CreationDate":"2011-03-17T16:47:00.000","Title":"is it possible to Insert a python tuple in a postgresql database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"is it possible to Insert a python tuple  in a postgresql database","AnswerCount":4,"Available Count":2,"Score":0.049958375,"is_accepted":false,"ViewCount":4015,"Q_Id":5342359,"Users Score":1,"Answer":"This question does not make any sense. You can insert using SQL whatever is supported by your database model. If you need a fancy mapper: look at an ORM like SQLAlchemy.","Q_Score":0,"Tags":"python,database,postgresql","A_Id":5342419,"CreationDate":"2011-03-17T16:47:00.000","Title":"is it possible to Insert a python tuple in a postgresql database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am attemping to install OpsCenter for Cassandra, and using the the standard REHL image.  I can't figure out how to get this to work.  Another version of EPEL perhaps?\nyum install opscenter....\nError: Package: python26-rrdtool-1.2.27-1.i386 (opscenter)\n           Requires: librrd.so.2","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":410,"Q_Id":5344641,"Users Score":0,"Answer":"Try installing rrdtool via yum, that should contain librrd.so.2 and correct your issue.","Q_Score":2,"Tags":"python,linux,centos,cassandra,yum","A_Id":5344716,"CreationDate":"2011-03-17T20:10:00.000","Title":"Amazon Linux AMI EC2 - librrd.so.2 dependency issue","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":0},{"Question":"I have a Webserver running in Python. He is getting some Data from some Apps and need to store these in MongoDB. My MongoDB is sharded. \nNow i want that my Webserver know how much Shards MongoDB has. At the moment he reads this from a cfg file. There is an Statement in MongoDb named printshardingstatus where u can see all shards. So i tried to call this statement from my Pythonserver. But it seems that it is not possible.I dont find such a function in the Pymongo API. \nSo my question is, is there an chance to run an MongoDB Statement in Python, so that it is directly passed and executed in MongoDB ?","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1576,"Q_Id":5350599,"Users Score":0,"Answer":"You can simply get config databasr and\n  execute find() on shards collection\n  just like normal collection.","Q_Score":0,"Tags":"python,mongodb,pymongo","A_Id":5377084,"CreationDate":"2011-03-18T10:21:00.000","Title":"Execute MongoDb Statements in Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm creating a server with Apache2 + mod_python + Django for development and would like to know how to use Mercurial to manage application development.\nMy idea is to make the folder where the Mercurial stores the project be the same folder to deploy Django.\nThank you for your attention!","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":627,"Q_Id":5397528,"Users Score":0,"Answer":"I thought about this, good idea for development.\nUse mercurial in common way. And of course you need deploy mercurial server before.\nIf you update your django project, it will be compiled on the fly.\n\n\nMy workflow:\n\nSet up mercurial server or use bitbucket\nInit repo locally\nPush repo to central repo\nOn server pull repo in some target dir\nEdit smth locally and push to central repo\nPull repo on server and everything is fine","Q_Score":0,"Tags":"python,django,mercurial,apache2,mod-python","A_Id":5397870,"CreationDate":"2011-03-22T20:37:00.000","Title":"How to use Mercurial to deploy Django applications?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have my database in msacess 2000 .mdb format which I downloaded from the net and now I want to access that database from my program which is a python script.\nCan I call tables from my programs??\nit would be very grateful if anyone  of you please suggest me what to do","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":5861,"Q_Id":5402463,"Users Score":0,"Answer":"Create an ODBC DSN wit hthis MDB. Python can access ODBC data sources.","Q_Score":2,"Tags":"python,ms-access","A_Id":5402549,"CreationDate":"2011-03-23T08:16:00.000","Title":"How do I access a .mdb file from python?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am using the function open_workbook() to open an excel file. But I cannot find any function to close the file later in the xlrd module. Is there a way to close the xls file using xlrd?\nOr is not required at all?","AnswerCount":2,"Available Count":1,"Score":1.0,"is_accepted":false,"ViewCount":22147,"Q_Id":5403781,"Users Score":6,"Answer":"The open_workbook calls the release_resources ( which closes the mmaped file ) before returning.","Q_Score":23,"Tags":"python,xlrd","A_Id":5404018,"CreationDate":"2011-03-23T10:24:00.000","Title":"Is there a way to close a workbook using xlrd","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Scenario\n\nEntity1 (id,itmname)\nEntity2 (id,itmname,price)\nEntity3 (id,itmname,profit)\nprofit and price are both IntegerProperty\n\nI want to count all the item with price more then 500 and profit more then 10.\nI know its join operation and is not supported by google. I tried my best to find out the way other then executing queries separately and performing count but I didn't get anything. \nThe reason for not executing queries separately is query execution time. In each query I am getting more then 50000 records as result so it takes nearly 20 seconds in fetching records from first query.","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":372,"Q_Id":5415342,"Users Score":0,"Answer":"The standard solution to this problem is denormalization.  Try storing a copy of price and profit in Entity1 and then you can answer your question with a single, simple query on Entity1.","Q_Score":1,"Tags":"python,google-app-engine","A_Id":5415555,"CreationDate":"2011-03-24T05:58:00.000","Title":"Optimizing join query performance in google app engine","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I have to re-design an existing application which uses Pylons (Python) on the backend and GWT on the frontend.\nIn the course of this re-design I can also change the backend system.\nI tried to read up on the advantages and disadvantages of various backend systems (Java, Python, etc) but I would be thankful for some feedback from the community.\nExisting application:\nThe existing application was developed with GWT 1.5 (runs now on 2.1) and is a multi-host-page setup.\nThe Pylons MVC framework defines a set of controllers\/host pages in which GWT widgets are embedded (\"classical website\").  \nData is stored in a MySQL database and accessed by the backend with SQLAlchemy\/Elixir. Server\/client communication is done with RequestBuilder (JSON).\nThe application is not a typical business like application with complex CRUD functionality (transactions, locking, etc) or sophisticated permission system (tough a simple ACL is required).\nThe application is used for visualization (charts, tables) of scientific data. The client interface is primarily used to display data in read-only mode. There might be some CRUD functionality but it's not the main aspect of the app.\nOnly a subset of the scientific data is going to be transfered to the client interface but this subset is generated out of large datasets.\nThe existing backend uses numpy\/scipy to read data from db\/files, create matrices and filter them.\nThe numbers of users accessing or using the app is relatively small, but the burden on the backend for each user\/request is pretty high because it has to read and filter large datasets.  \nRequirements for the new system:\nI want to move away from the multi-host-page setup to the MVP architecture (one single host page).\nSo the backend only serves one host page and acts as data source for AJAX calls.\nData will be still stored in a relational database (PostgreSQL instead of MySQL).\nThere will be a simple ACL (defines who can see what kind of data) and maybe some CRUD functionality (but it's not a priority).\nThe size of the datasets is going to increase, so the burden on the backend is probably going to be higher. There won't be many concurrent requests but the few ones have to be handled by the backend quickly. Hardware (RAM and CPU) for the backend server is not an issue. \nPossible backend solutions:\nPython (SQLAlchemy, Pylons or Django):\nAdvantages: \n\nRapid prototyping.  \nRe-Use of parts of the existing application \nNumpy\/Scipy for handling large datasets.\n\nDisadvantages:\n\nWeakly typed language -> debugging can be painful\nServer\/Client communication (JSON parsing or using 3rd party libraries). \nPython GIL -> scaling with concurrent requests ?\nServer language (python) <> client language (java)\n\n\nJava (Hibernate\/JPA, Spring, etc)\nAdvantages: \n\nOne language for both client and server (Java)\n\"Easier\" to debug. \nServer\/Client communication (RequestFactory, RPC) easer to implement.\nPerformance, multi-threading, etc\nObject graph can be transfered (RequestFactory).\nCRUD \"easy\" to implement \nMultitear architecture (features)\n\nDisadvantages: \n\nMultitear architecture (complexity,requires a lot of configuration)\nHandling of arrays\/matrices (not sure if there is a pendant to numpy\/scipy in java).\nNot all features of the Java web application layers\/frameworks used (overkill?). \n\nI didn't mention any other backend systems (RoR, etc) because I think these two systems are the most viable ones for my use case. \nTo be honest I am not new to Java but relatively new to Java web application frameworks. I know my way around Pylons though in the new setup not much of the Pylons features (MVC, templates) will be used because it probably only serves as AJAX backend.\nIf I go with a Java backend I have to decide whether to do a RESTful service (and clearly separate client from server) or use RequestFactory (tighter coupling). There is no specific requirement for \"RESTfulness\". In case of a Python backend I would probably go with a RESTful backend (as I have to take care of client\/server communication anyways). \nAlthough mainly scientific data is going to be displayed (not part of any Domain Object Graph) also related metadata is going to be displayed on the client (this would favor RequestFactory).\nIn case of python I can re-use code which was used for loading and filtering of the scientific data.\nIn case of Java I would have to re-implement this part. \nBoth backend-systems have its advantages and disadvantages. \nI would be thankful for any further feedback.\nMaybe somebody has experience with both backend and\/or with that use case.\nthanks in advance","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1559,"Q_Id":5417372,"Users Score":1,"Answer":"We had the same dilemma in the past. \nI was involved in designing and building a system that had a GWT frontend and Java (Spring, Hibernate) backend. Some of our other (related) systems were built in Python and Ruby, so the expertise was there, and a question just like yours came up.\nWe decided on Java mainly so we could use a single language for the entire stack. Since the same people worked on both the client and server side, working in a single language reduced the need to context-switch when moving from client to server code (e.g. when debugging). In hindsight I feel that we were proven right and that that was a good decision.\nWe used RPC, which as you mentioned yourself definitely eased the implementation of c\/s communication. I can't say that I liked it much though. REST + JSON feels more right, and at the very least creates better decoupling between server and client. I guess you'll have to decide based on whether you expect you might need to re-implement either client or server independently in the future. If that's unlikely, I'd go with the KISS principle and thus with RPC which keeps it simple in this specific case.\nRegarding the disadvantages for Java that you mention, I tend to agree on the principle (I prefer RoR myself), but not on the details. The multitier and configuration architecture isn't really a problem IMO - Spring and Hibernate are simple enough nowadays. IMO the advantage of using Java across client and server in this project trumps the relative ease of using python, plus you'll be introducing complexities in the interface (i.e. by doing REST vs the native RPC).\nI can't comment on Numpy\/Scipy and any Java alternatives. I've no experience there.","Q_Score":4,"Tags":"java,python,gwt,architecture,web-frameworks","A_Id":5421810,"CreationDate":"2011-03-24T09:56:00.000","Title":"Feedback on different backends for GWT","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"Is there a way to reduce the I\/O's associated with either mysql or a python script?  I am thinking of using EC2 and the costs seem okay except I can't really predict my I\/O usage and I am worried it might blindside me with costs.  \nI basically develop a python script to parse data and upload it into mysql.  Once its in mysql, I do some fairly heavy analytic on it(creating new columns, tables..basically alot of math and financial based analysis on a large dataset). So is there any design best practices to avoid heavy I\/O's?  I think memcached stores a everything in memory and accesses it from there, is there a way to get mysql or other scripts to do the same?\nI am running the scripts fine right now on another host with 2 gigs of ram, but the ec2 instance I was looking at had about 8 gigs so I was wondering if I could use the extra memory to save me some money.","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":202,"Q_Id":5425289,"Users Score":0,"Answer":"You didn't really specify whether it was writes or reads. My guess is that you can do it all in a mysql instance in a ramdisc (tmpfs under Linux).\nOperations such as ALTER TABLE and copying big data around end up creating a lot of IO requests because they move a lot of data. This is not the same as if you've just got a lot of random (or more predictable queries).\nIf it's a batch operation, maybe you can do it entirely in a tmpfs instance. \nIt is possible to run more than one mysql instance on the machine, it's pretty easy to start up an instance on a tmpfs - just use mysql_install_db with datadir in a tmpfs, then run mysqld with appropriate params. Stick that in some shell scripts and you'll get it to start up. As it's in a ramfs, it won't need to use much memory for its buffers - just set them fairly small.","Q_Score":2,"Tags":"python,mysql,amazon-ec2,mysql-management","A_Id":5426527,"CreationDate":"2011-03-24T20:44:00.000","Title":"reducing I\/O on application and database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":0},{"Question":"I using MySQLdb for access to mysql database from python. I need to know if connection with database is still alive... are there any attribute or method in order to do this???\nthanks!!","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":146,"Q_Id":5430652,"Users Score":0,"Answer":"To be honest, I haven't used mysqldb in python in a very long time.\nThat being said, I would suggest using an execute(\"now()\") (or \"select 1\", any other \"dummy\" SQL command) and handle any errors.\nedit: That should also probably be part of a class you're using.  Don't fill your entire project with .execute(\"now()\") on every other line. ;)","Q_Score":0,"Tags":"python-3.x,mysql-python","A_Id":5430722,"CreationDate":"2011-03-25T09:31:00.000","Title":"Verify the connection with MySQL database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"save_or_update has been removed in 0.6. Are there alternatives to use them in 0.6 and above?\nI noticed the existence of the method _save_or_update_state for session objects, but there are no docs on this method.","AnswerCount":3,"Available Count":2,"Score":0.0665680765,"is_accepted":false,"ViewCount":4986,"Q_Id":5442825,"Users Score":1,"Answer":"Session.merge() works fine for both new and existing object. But you have to remember, that merge() returns object bound to the session as opposed to add() (and save_or_update() in old versions) which puts object passed as argument into the session. This behavior is required to insure there is a single object for each identity in the session.","Q_Score":2,"Tags":"python,sql,sqlalchemy","A_Id":5469880,"CreationDate":"2011-03-26T14:05:00.000","Title":"save_or_update using SQLalchemy 0.6","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"save_or_update has been removed in 0.6. Are there alternatives to use them in 0.6 and above?\nI noticed the existence of the method _save_or_update_state for session objects, but there are no docs on this method.","AnswerCount":3,"Available Count":2,"Score":-0.0665680765,"is_accepted":false,"ViewCount":4986,"Q_Id":5442825,"Users Score":-1,"Answer":"session.merge() will not work if you have your db setup as a master-slave, where you typically want to query from the slave, but write to the master. I have such a setup, and ended up re-querying from the master just before the writing, then using a session.add() if the data is indeed not there on the master.","Q_Score":2,"Tags":"python,sql,sqlalchemy","A_Id":11861997,"CreationDate":"2011-03-26T14:05:00.000","Title":"save_or_update using SQLalchemy 0.6","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm actually working in a search engine project. We are working with python + mongoDb.\nI have a pymongo cursor after excecuting a find() command to the mongo db. The pymongo cursor has around 20k results.\nI have noticed that the iteration over the pymongo cursor is really slow compared with a normal iteration over for example a list of the same size.\nI did a little benchmark:\n\niteration over a list of 20k strings: 0.001492 seconds\niteration over a pymongo cursor with 20k results: 1.445343 seconds\n\nThe difference is really a lot. Maybe not a problem with this amounts of results, but if I have millions of results the time would be unacceptable.\nHas anyone got an idea of why pymongo cursors are too slow to iterate?\nAny idea of how can I iterate the cursor in less time?\nSome extra info:\n\nPython v2.6\nPyMongo v1.9\nMongoDB v1.6 32 bits","AnswerCount":4,"Available Count":2,"Score":0.049958375,"is_accepted":false,"ViewCount":14362,"Q_Id":5480340,"Users Score":1,"Answer":"the default cursor size is 4MB, and the maximum it can go to is 16MB. you can try to increase your cursor size until that limit is reached and see if you get an improvement, but it also depends on what your network can handle.","Q_Score":10,"Tags":"python,mongodb,performance,iteration,database-cursor","A_Id":7828897,"CreationDate":"2011-03-29T23:52:00.000","Title":"Python + MongoDB - Cursor iteration too slow","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm actually working in a search engine project. We are working with python + mongoDb.\nI have a pymongo cursor after excecuting a find() command to the mongo db. The pymongo cursor has around 20k results.\nI have noticed that the iteration over the pymongo cursor is really slow compared with a normal iteration over for example a list of the same size.\nI did a little benchmark:\n\niteration over a list of 20k strings: 0.001492 seconds\niteration over a pymongo cursor with 20k results: 1.445343 seconds\n\nThe difference is really a lot. Maybe not a problem with this amounts of results, but if I have millions of results the time would be unacceptable.\nHas anyone got an idea of why pymongo cursors are too slow to iterate?\nAny idea of how can I iterate the cursor in less time?\nSome extra info:\n\nPython v2.6\nPyMongo v1.9\nMongoDB v1.6 32 bits","AnswerCount":4,"Available Count":2,"Score":-1.0,"is_accepted":false,"ViewCount":14362,"Q_Id":5480340,"Users Score":-4,"Answer":"You don't provide any information about the overall document sizes. Fetch such an amount of document requires both network traffic and IO on the database server.\nThe performance is sustained \"bad\" even in \"hot\" state with warm caches? You can use \"mongosniff\" in order to inspect the \"wire\" activity and system tools like \"iostat\" to monitor the disk activity on the server. In addition \"mongostat\" gives a bunch of valuable information\".","Q_Score":10,"Tags":"python,mongodb,performance,iteration,database-cursor","A_Id":5480531,"CreationDate":"2011-03-29T23:52:00.000","Title":"Python + MongoDB - Cursor iteration too slow","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm in the planning phase of an Android app which synchronizes to a web app.  The web side will be written in Python with probably Django or Pyramid while the Android app will be straightforward java.  My goal is to have the Android app work while there is no data connection, excluding the social\/web aspects of the application.\nThis will be a run-of-the-mill app so I want to stick to something that can be installed easily through one click in the market and not require a separate download like CloudDB for Android.\nI haven't found any databases that support this functionality so I will write it myself.  One caveat with writing the sync logic is there will be some shared data between users that multiple users will be able to write to.  This is a solo project so I thought I'd through this up here to see if I'm totally off-base.\n\nThe app will process local saves to the local sqlite database and then send messages to a service which will attempt to synchronize these changes to the remote database.  \nThe sync service will alternate between checking for messages for the local app, i.e. changes to shared data by other users, and writing the local changes to the remote server. \nAll data will have a timestamp for tracking changes\nWhen writing from the app to the server, if the server has newer information, the user will be warned about the conflict and prompted to overwrite what the server has or abandon the local changes.  If the server has not been updated since the app last read the data, process the update.\nWhen data comes from the server to the app, if the server has newer data overwrite the local data otherwise discard it as it will be handled in the next go around by the app updating the server.\n\nHere's some questions:\n1) Does this sound like overkill?  Is there an easier way to handle this?\n2) Where should this processing take place?  On the client or the server?  I'm thinking the advantage of the client is less processing on the server but if it's on the server, this makes it easier to implement other clients.\n3) How should I handle the updates from the server?  Incremental polling or comet\/websocket?  One thing to keep in mind is that I would prefer to go with a minimal installation on Webfaction to begin with as this is the startup.\nOnce these problems are tackled I do plan on contributing the solution to the geek community.","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":1618,"Q_Id":5544689,"Users Score":1,"Answer":"1) Looks like this is pretty good way to manage your local & remote changes + support offline work. I don't think this is overkill\n2) I think, you should cache user's changes locally with local timestamp until synchronizing is finished. Then server should manage all processing: track current version, commit and rollback update attempts. Less processing on client = better for you!  (Easier to support and implement)\n3) I'd choose polling if I want to support offline-mode, because in offline you can't keep your socket open and you will have to reopen it every time when Internet connection is restored. \nPS: Looks like this is VEEERYY OLD question... LOL","Q_Score":4,"Tags":"python,android","A_Id":11871778,"CreationDate":"2011-04-04T21:42:00.000","Title":"Android app database syncing with remote database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"when I launch my application with apache2+modwsgi\nI catch \n\nException Type:    ImportError\nException Value: DLL load failed: The specified module could not be found.\n\nin line\n\nfrom lxml import etree\n\nwith Django dev server all works fine\nVisual C++ Redistributable 2008 installed\nDependency walker told that msvcrt90.dll is missed\nbut there is same situation with cx_Oracle, but cx_Oracle's dll loads correct\nany ideas?\nwindows 2003 server 64bit and windows XP sp3 32bit\npython 2.7 32 bit\ncx_Oracle 5.0.4 32bit\nUPD:\ndownload libxml2-2.7.7 and  libxslt-1.1.26\ntried to build with setup.py build --compiler mingw32 \n\nBuilding lxml version 2.3.\nBuilding with Cython 0.14.1.\nERROR: 'xslt-config' is not recognized as an internal or external command,\noperable program or batch file.\n\n** make sure the development packages of libxml2 and libxslt are installed **\n\nUsing build configuration of libxslt\nrunning build\nrunning build_py\nrunning build_ext\nskipping 'src\/lxml\\lxml.etree.c' Cython extension (up-to-date)\nbuilding 'lxml.etree' extension\nC:\\MinGW\\bin\\gcc.exe -mno-cygwin -mdll -O -Wall -IC:\\Python27\\include -IC:\\Python27\\PC -c src\/lxml\\lxml.etree.c -o build\\temp.win32-2.7\\Release\\src\\lxml\\lxml.et\nree.o -w\nwriting build\\temp.win32-2.7\\Release\\src\\lxml\\etree.def\nC:\\MinGW\\bin\\gcc.exe -mno-cygwin -shared -s build\\temp.win32-2.7\\Release\\src\\lxml\\lxml.etree.o build\\temp.win32-2.7\\Release\\src\\lxml\\etree.def -LC:\\Python27\\lib\ns -LC:\\Python27\\PCbuild -llibxslt -llibexslt -llibxml2 -liconv -lzlib -lWS2_32 -lpython27 -lmsvcr90 -o build\\lib.win32-2.7\\lxml\\etree.pyd\nbuild\\temp.win32-2.7\\Release\\src\\lxml\\lxml.etree.o:lxml.etree.c:(.text+0xd11): undefined reference to `_imp__xmlFree'\nbuild\\temp.win32-2.7\\Release\\src\\lxml\\lxml.etree.o:lxml.etree.c:(.text+0xd24): undefined reference to `_imp__xmlFree'\nbuild\\temp.win32-2.7\\Release\\src\\lxml\\lxml.etree.o:lxml.etree.c:(.text+0x1ee92): undefined reference to `_imp__xmlFree'\nbuild\\temp.win32-2.7\\Release\\src\\lxml\\lxml.etree.o:lxml.etree.c:(.text+0x1eed6): undefined reference to `_imp__xmlFree'\nbuild\\temp.win32-2.7\\Release\\src\\lxml\\lxml.etree.o:lxml.etree.c:(.text+0x2159e): undefined reference to `_imp__xmlMalloc'\nbuild\\temp.win32-2.7\\Release\\src\\lxml\\lxml.etree.o:lxml.etree.c:(.text+0x2e741): undefined reference to `_imp__xmlFree'\nbuild\\temp.win32-2.7\\Release\\src\\lxml\\lxml.etree.o:lxml.etree.c:(.text+0x2e784): undefined reference to `_imp__xmlFree'\nbuild\\temp.win32-2.7\\Release\\src\\lxml\\lxml.etree.o:lxml.etree.c:(.text+0x3f157): undefined reference to `_imp__xmlFree'\nbuild\\temp.win32-2.7\\Release\\src\\lxml\\lxml.etree.o:lxml.etree.c:(.text+0x3f19a): undefined reference to `_imp__xmlFree'\nbuild\\temp.win32-2.7\\Release\\src\\lxml\\lxml.etree.o:lxml.etree.c:(.text+0x3f4ac): undefined reference to `_imp__xmlFree'\nbuild\\temp.win32-2.7\\Release\\src\\lxml\\lxml.etree.o:lxml.etree.c:(.text+0x3f4ef): more undefined references to `_imp__xmlFree' follow\nbuild\\temp.win32-2.7\\Release\\src\\lxml\\lxml.etree.o:lxml.etree.c:(.text+0xb1ad5): undefined reference to `xsltLibxsltVersion'\nbuild\\temp.win32-2.7\\Release\\src\\lxml\\lxml.etree.o:lxml.etree.c:(.text+0xb1b9a): undefined reference to `xsltDocDefaultLoader'\ncollect2: ld returned 1 exit status\nerror: command 'gcc' failed with exit status 1\n\nUPD2:\nI understand why import cx_Oracle works fine: cx_Oracle.pyd contains \"MSVCRT.dll\" dependence etree.pyd doesn't have it","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1054,"Q_Id":5552162,"Users Score":2,"Answer":"It is indeed because of 'msvcrt90.dll'. From somewhere in micro patch revisions of Python 2.6 they stopped building in automatic dependencies on the DLL for extension modules and relied on Python executable doing it. When embedded in other systems however you are then dependent on that executable linking to DLL and in the case of Apache it doesn't. The change in Python has therefore broken many systems which embed Python on Windows and the only solution is for every extension module to have their own dependencies on required DLLs which many don't. The psycopg2 extension was badly affected by this and they have change their builds to add the dependency back in themselves now. You might go searching about the problem as it occurred for psycopg2. One of the solutions was to rebuild extensions with MinGW compiler on Windows instead.","Q_Score":2,"Tags":"python,apache2,mingw,lxml,cx-oracle","A_Id":5559988,"CreationDate":"2011-04-05T12:55:00.000","Title":"problem with soaplib (lxml) with apache2 + mod_wsgi","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm currently working on a proof of concept application using Python 3.2 via SQLAlchemy with a MS SQL Server back end.  Thus far, I'm hitting a brick wall looking for ways to actually do the connection.  Most discussions point to using pyODBC, however it does not support Python 3.x yet.\nDoes anyone have any connection examples for MS SQL and SQLAlchemy, under Python 3.2?\nThis is under Windows 7 64bit also.\nThanks.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":867,"Q_Id":5559645,"Users Score":0,"Answer":"At this moment none of the known Python drivers to connect to Sql Server had a compatible python 3000 version.\n\nPyODBC\nmxODBC\npymssql\nzxjdbc \nAdoDBAPI","Q_Score":0,"Tags":"python,sql-server,sqlalchemy","A_Id":5559890,"CreationDate":"2011-04-05T23:10:00.000","Title":"SQLAlchemy 3.2 and MS SQL Connectivity","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm working on a python server which concurrently handles transactions on a number of databases, each storing performance data about a different application. Concurrency is accomplished via the Multiprocessing module, so each transaction thread starts in a new process, and shared-memory data protection schemes are not viable.\n  I am using sqlite as my DBMS, and have opted to set up each application's DB in its own file. Unfortunately, this introduces a race condition on DB creation; If two process attempt to create a DB for the same new application at the same time, both will create the file where the DB is to be stored. My research leads me to believe that one cannot lock a file before it is created; Is there some other mechanism I can use to ensure that the file is not created and then written to concurrently?\nThanks in advance,\nDavid","AnswerCount":5,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":327,"Q_Id":5559660,"Users Score":0,"Answer":"You could capture the error when trying to create the file in your code and in your exception handler, check if the file exists and use the existing file instead of creating it.","Q_Score":0,"Tags":"python,sqlite","A_Id":5559724,"CreationDate":"2011-04-05T23:13:00.000","Title":"Prevent a file from being created in python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm working on a python server which concurrently handles transactions on a number of databases, each storing performance data about a different application. Concurrency is accomplished via the Multiprocessing module, so each transaction thread starts in a new process, and shared-memory data protection schemes are not viable.\n  I am using sqlite as my DBMS, and have opted to set up each application's DB in its own file. Unfortunately, this introduces a race condition on DB creation; If two process attempt to create a DB for the same new application at the same time, both will create the file where the DB is to be stored. My research leads me to believe that one cannot lock a file before it is created; Is there some other mechanism I can use to ensure that the file is not created and then written to concurrently?\nThanks in advance,\nDavid","AnswerCount":5,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":327,"Q_Id":5559660,"Users Score":0,"Answer":"You didn't mention the platform, but on linux open(), or os.open() in python, takes a flags parameter which you can use. The O_CREAT flag creates a file if it does not exist, and the O_EXCL flag gives you an error if the file already exists. You'll also be needing O_RDONLY, O_WRONLY or O_RDWR for specifying the access mode. You can find these constants in the os module.\nFor example: fd = os.open(filename, os.O_RDWR | os.O_CREAT | os.O_EXCL)","Q_Score":0,"Tags":"python,sqlite","A_Id":5559768,"CreationDate":"2011-04-05T23:13:00.000","Title":"Prevent a file from being created in python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"Any idea on how I could run a bunch of .sql files that contains lots of functions from within sqlalchemy, after I create the schema ? I've tried using DDL(), engine.text(<text>).execute(), engine.execute(<text>). None of them work, they are either failing because improper escape or some other weird errors. I am using sqlalchemy 0.6.6","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":1729,"Q_Id":5563437,"Users Score":1,"Answer":"You can't do that. You must parse the file and split it into individual SQL commands, and then execute each one separately in a transaction.","Q_Score":2,"Tags":"python,sqlalchemy","A_Id":5564716,"CreationDate":"2011-04-06T08:25:00.000","Title":"run .sql files from within sqlalchemy","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have been trying to generate data in Excel.\nI generated .CSV file.\nSo up to that point it's easy.\nBut generating graph is quite hard in Excel...\nI am wondering, is python able to generate data AND graph in excel?\nIf there are examples or code snippets, feel free to post it :)\nOr a workaround can be use python to generate graph in graphical format like .jpg, etc or .pdf file is also ok..as long as workaround doesn't need dependency such as the need to install boost library.","AnswerCount":5,"Available Count":1,"Score":0.0798297691,"is_accepted":false,"ViewCount":48351,"Q_Id":5568319,"Users Score":2,"Answer":"I suggest you to try gnuplot while drawing graph from data files.","Q_Score":6,"Tags":"python,excel,charts,export-to-excel","A_Id":5568485,"CreationDate":"2011-04-06T14:47:00.000","Title":"use python to generate graph in excel","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a python program which makes use of MySQL database.\nI am getting following error.\nIt would be very grateful if some one help me out a solution.  \n\nTraceback (most recent call last):\nFile \"version2_1.py\", line 105, in \nrefine(wr,w)#function for replacement\nFile \"version2_1.py\", line 49, in refine\nwrds=db_connect.database(word)\nFile \"\/home\/anusha\/db_connect.py\", line 6, in database\ndb = MySQLdb.connect(\"localhost\",\"root\",\"localhost\",\"anusha\" )\nFile \"\/usr\/lib\/pymodules\/python2.6\/MySQLdb\/_init_.py\", line 81, in Connect\nreturn Connection(*args, **kwargs)\nFile \"\/usr\/lib\/pymodules\/python2.6\/MySQLdb\/connections.py\", line 170, in __init__\nsuper(Connection, self).__init__(*args, **kwargs2)\n_mysql_exceptions.OperationalError: (1045, \"Access denied for user 'root'@'localhost' (using password: YES)\")","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":3356,"Q_Id":5606665,"Users Score":0,"Answer":"Looks like you have an incorrect username\/password for MySQL. Try creating a user in MySQL and use that to connect.","Q_Score":1,"Tags":"python,mysql,mysql-error-1045","A_Id":5606690,"CreationDate":"2011-04-09T17:37:00.000","Title":"Error when trying to execute a Python program that uses MySQL","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"from the interpreter i can issue >>> from MySQLdb just fine. so, I'm assuming the module did actually load. My source looks as follows:  \n\nfrom Tkinter import *\n  from MySQLdb import *\n  \"\"\"\n  Inventory control for Affordable Towing  \nFunctions:\n  connection() - Controls database connection\n  delete() - Remove item from database\n  edit() - Edit item's attributes in database\n  lookup() - Lookup an item\n  new() - Add a new item to database\n  receive() - Increase quantity of item in database\n  remove() - Decrease quantity of item in database\n  report() - Display inventory activity\n  transfer() - Remove item from one location, receive item in another  \n\"\"\"\n  def control():\n  ....dbInfo = { 'username':'livetaor_atowtw', 'password':'spam', \\\n  ....'server':'eggs.com', 'base':'livetaor_towing', 'table':'inventory' }\n  ....def testConnection():\n  ........sql = MySQLdb.connect(user=dbInfo[username], passwd=dbInfo[password], \\\n  ........host=dbInfo[server], db=dbInfo[base])\n  ........MySQLdb.mysql_info(sql)  \n....testConnection()  \ncontrol()  \n\nthis gives me:  \n\nbrad@brads-debian:~\/python\/towing\/inventory$ python inventory.py\n  Traceback (most recent call last):\n  ..File \"inventory.py\", line 53, in \n  ....control()\n  ..File \"inventory.py\", line 26, in control\n  ....testConnection()\n  ..File \"inventory.py\", line 22, in testConnection\n  ....sql = MySQLdb.connect(user=dbInfo[username], passwd=dbInfo[password], \\\n  NameError: global name 'MySQLdb' is not defined  \n\n1) where am I going wrong?\n2) any other gotcha's that you folks see?\n3) any advice on how to check for a valid connection to the database, (not just the server)?","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":7873,"Q_Id":5609322,"Users Score":1,"Answer":"from MySQLdb import * and import MySQLdb do very different things.","Q_Score":0,"Tags":"python,mysql,programming-languages,network-programming","A_Id":5609341,"CreationDate":"2011-04-10T02:12:00.000","Title":"python2.6 with MySQLdb, NameError 'MySQLdb' not defined","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Is there some module to allow for easy DB provider configuration via connection string, similar to PHP's PDO where I can nicely say \"psql:\/\/\" or \"mysql:\/\/\" or, in this python project, am I just going to have to code some factory classes that use MySQLdb, psycopg2, etc?","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":413,"Q_Id":5617246,"Users Score":0,"Answer":"There's something not quite as nice in logilab.database, but which works quite well (http:\/\/www.logilab.org\/project\/logilab-database). Supports sqlite, mysql, postgresql and some versions of mssql, and some abstraction mechanisms on the SQL understood by the different backend engines.","Q_Score":0,"Tags":"python","A_Id":5617901,"CreationDate":"2011-04-11T05:49:00.000","Title":"python and DB connection abstraction?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Python hangs on \nlxml.etree.XMLSchema(tree)\nwhen I use it on apache server + mod_wsgi (Windows)\nWhen I use Django dev server - all works fine\nif you know about other nice XML validation solution against XSD, tell me pls\nUpdate:\nI'm using soaplib, which uses lxml\n\nlogger.debug(\"building schema...\")\nself.schema = etree.XMLSchema(etree.parse(f))\n\nlogger.debug(\"schema %r built, cleaning up...\" % self.schema)\n\nI see \"building schema...\" in apache logs, but I don't see \"schema %r built, cleaning up...\"\nUpdate 2:\nI built lxml 2.3 with MSVS 2010 visual C++; afterwards it crashes on this line self.schema = etree.XMLSchema(etree.parse(f)) with  Unhandled exception at 0x7c919af2 in httpd.exe: 0xC0000005: Access violation writing location 0x00000010.","AnswerCount":3,"Available Count":2,"Score":0.0665680765,"is_accepted":false,"ViewCount":1123,"Q_Id":5617599,"Users Score":1,"Answer":"I had a similar problem on a Linux system. Try installing a more recent version of libxml2 and reinstalling lxml,  at least that's what did it for me.","Q_Score":5,"Tags":"python,apache,mod-wsgi,lxml,xml-validation","A_Id":6176299,"CreationDate":"2011-04-11T06:34:00.000","Title":"Python hangs on lxml.etree.XMLSchema(tree) with apache + mod_wsgi","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Python hangs on \nlxml.etree.XMLSchema(tree)\nwhen I use it on apache server + mod_wsgi (Windows)\nWhen I use Django dev server - all works fine\nif you know about other nice XML validation solution against XSD, tell me pls\nUpdate:\nI'm using soaplib, which uses lxml\n\nlogger.debug(\"building schema...\")\nself.schema = etree.XMLSchema(etree.parse(f))\n\nlogger.debug(\"schema %r built, cleaning up...\" % self.schema)\n\nI see \"building schema...\" in apache logs, but I don't see \"schema %r built, cleaning up...\"\nUpdate 2:\nI built lxml 2.3 with MSVS 2010 visual C++; afterwards it crashes on this line self.schema = etree.XMLSchema(etree.parse(f)) with  Unhandled exception at 0x7c919af2 in httpd.exe: 0xC0000005: Access violation writing location 0x00000010.","AnswerCount":3,"Available Count":2,"Score":0.1325487884,"is_accepted":false,"ViewCount":1123,"Q_Id":5617599,"Users Score":2,"Answer":"I had the same problem (lxml 2.2.6, mod_wsgi 3.2). A work around for this is to pass a file or filename to the constructor: XMLSchema(file=).","Q_Score":5,"Tags":"python,apache,mod-wsgi,lxml,xml-validation","A_Id":6685198,"CreationDate":"2011-04-11T06:34:00.000","Title":"Python hangs on lxml.etree.XMLSchema(tree) with apache + mod_wsgi","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a sentence like the cat sat on the mat stored as a single sql field.  I want to periodically search for keywords which are not not in a stop list, in this case cat sat mat  What's the best way to store them in an SQL table for quick searching?\nAs far as I can see it I see the following options\n\nUp to [n] additional columns per row, one for each word.\nStore all of the interesting words in a single, comma separated field.\nA new table, linked to the first with either of the above options. \nDo nothing and search for a match each time I have a new word to search on. \n\nWhich is best practice and which is fastest for searching for word matches?  I'm using sqlite in python if that makes a difference.","AnswerCount":3,"Available Count":2,"Score":0.0665680765,"is_accepted":false,"ViewCount":290,"Q_Id":5627140,"Users Score":1,"Answer":"I do something similar with SQLite too. In my experience it's not as fast as other db's in this type of situation so it pays to make your schema as simple as possible.\n\nUp to [n] additional columns per row, one for each word.\nStore all of the interesting words in a single, comma separated field.\nA new table, linked to the first with either of the above options.\nDo nothing and search for a match each time I have a new word to search on.\n\nOf your 4 options, 2) and 4) may be too slow if you're looking to scale and matching using LIKE. Matching using full text is faster though, so that's worth looking into. 1) looks to be bad database design, what if there's more words than columns ? And if there's less, it's just wasted space. 3) is best IMO, if you make the words the primary key in their own table the searching speed should be acceptably fast.","Q_Score":1,"Tags":"python,sql,sqlite","A_Id":5627582,"CreationDate":"2011-04-11T20:26:00.000","Title":"Storing interesting words from a sentence","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a sentence like the cat sat on the mat stored as a single sql field.  I want to periodically search for keywords which are not not in a stop list, in this case cat sat mat  What's the best way to store them in an SQL table for quick searching?\nAs far as I can see it I see the following options\n\nUp to [n] additional columns per row, one for each word.\nStore all of the interesting words in a single, comma separated field.\nA new table, linked to the first with either of the above options. \nDo nothing and search for a match each time I have a new word to search on. \n\nWhich is best practice and which is fastest for searching for word matches?  I'm using sqlite in python if that makes a difference.","AnswerCount":3,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":290,"Q_Id":5627140,"Users Score":1,"Answer":"I would suggest giving your sentences a key, likely IDENTITY. I would then create a second table linking to your sentence table, with a row for each interesting word. \nIf you'd like to search for say, words starting with ca- if you stored these words in a comma delimited you'd have to wildcard the start and end, whereas if they are each in a separate row you can bypass the beginning wildcard.\nAlso, assuming you find a match, in a comma separated list you'd have to parse out which word is actually a hit. With the second table you simply return the word itself. Not to mention the fact that storing multiple values in one field a major no-no in a relational database.","Q_Score":1,"Tags":"python,sql,sqlite","A_Id":5627243,"CreationDate":"2011-04-11T20:26:00.000","Title":"Storing interesting words from a sentence","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Beginner question- what is the difference between sqlite and sqlalchemy?","AnswerCount":2,"Available Count":1,"Score":1.0,"is_accepted":false,"ViewCount":24446,"Q_Id":5632677,"Users Score":66,"Answer":"They're apples and oranges.\nSqlite is a database storage engine, which can be better compared with things such as MySQL, PostgreSQL, Oracle, MSSQL, etc. It is used to store and retrieve structured data from files.\nSQLAlchemy is a Python library that provides an object relational mapper (ORM). It does what it suggests: it maps your databases (tables, etc.) to Python objects, so that you can more easily and natively interact with them. SQLAlchemy can be used with sqlite, MySQL, PostgreSQL, etc.\nSo, an ORM provides a set of tools that let you interact with your database models consistently across database engines.","Q_Score":37,"Tags":"python,sqlite,sqlalchemy","A_Id":5632745,"CreationDate":"2011-04-12T08:54:00.000","Title":"What is the difference between sqlite3 and sqlalchemy?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a really large excel file and i need to delete about 20,000 rows, contingent on meeting a simple condition and excel won't let me delete such a complex range when using a filter. The condition is:\nIf the first column contains the value, X, then I need to be able to delete the entire row.\nI'm trying to automate this using python and xlwt, but am not quite sure where to start. Seeking some code snippits to get me started...\nGrateful for any help that's out there!","AnswerCount":6,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":51378,"Q_Id":5635054,"Users Score":12,"Answer":"Don't delete. Just copy what you need.\n\nread the original file\nopen a new file\niterate over rows of the original file (if the first column of the row does not contain the value X, add this row to the new file)\nclose both files\nrename the new file into the original file","Q_Score":5,"Tags":"python,excel,xlwt","A_Id":5635203,"CreationDate":"2011-04-12T12:19:00.000","Title":"Python to delete a row in excel spreadsheet","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"After much study and investigation, I've decided to do my Python development with pyQT4 using Eric5 as the editor.  However, I've run into a brick wall with trying to get MySQL to work.  It appears that there's an issue with the QMySQL driver.  From the discussions that I've seen so far, the only fix is to install the pyQT SDK and then recompile the MySQL driver.  A painful process that I really don't want to have to go through.  I would actually prefer to use MS SQL but I'm not finding any drivers for pyQT with MSSQL support.\nSo, my question is: What is the best approach for using pyQT with either mySQL or MSSQL, that actually works?\nWhile waiting for an answer, I might just tinker with SQLAlchemy and mySQL.Connector to see if it will co-exist with pyQT.","AnswerCount":3,"Available Count":1,"Score":0.1325487884,"is_accepted":false,"ViewCount":6327,"Q_Id":5642537,"Users Score":2,"Answer":"yes that will work, I do the same thing. I like a programming API, like what SQLAlchemy provides over the Raw SQL version of Qt's QtSql module.  It works fine and nice, just populate a subclassed QAbstractTableModel with data from your sqlalchemy queries, like you would with data from any other python object.  This though means you're handling caching and database queries, losing the niceness of QtSqlTableModel.  But shouldn't be too bad.","Q_Score":1,"Tags":"python,mysql,sql-server,pyqt","A_Id":5643057,"CreationDate":"2011-04-12T22:50:00.000","Title":"pyQT and MySQL or MSSQL Connectivity","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am very new to python and Django, was actually thrown in to finish off some coding for my company since our coder left for overseas.\nWhen I run python manage.py syncdb I receive the following error\npsycopg2.OperationalError: FATAL:  password authentication failed for user \"winepad\"\nI'm not sure why I am being prompted for user \"winepad\" as I've created no such user by that name, I am running the sync from a folder named winepad. In my pg_hba.conf file all I have is a postgres account which I altered with a new password.\nAny help would be greatly appreciated as the instructions I left are causing me some issues.\nThank you in advance","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":3164,"Q_Id":5643201,"Users Score":1,"Answer":"Check your settings.py file. The most likely reason for this issue is that the username for the database is set to \"winepad\". Change that to the appropriate value and rerun python manage.py syncdb That should fix the issue.","Q_Score":0,"Tags":"python,django,postgresql","A_Id":5643247,"CreationDate":"2011-04-13T00:37:00.000","Title":"python manage.py syncdb","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have just begun learning Python. Eventually I will learn Django, as my goal is to able to do web development (video sharing\/social networking). At which point should I begin learning MySQL? Do I need to know it before I even begin Django? If so, how much should I look to know before diving into Django? Thank you.","AnswerCount":4,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":1826,"Q_Id":5643400,"Users Score":0,"Answer":"Django uses its own ORM, so I guess it's not completely necessary to learn MySQL first, but I suspect it would help a fair bit to know what's going on behind the scenes, and it will help you think in the correct way to formulate your queries.\nI would start learning MySQL (or any other SQL), after you've got a pretty good grip on Python, but probably before you start learning Django, or perhaps alongside. You won't need a thorough understanding of SQL. At least, not to get started.\n\nErr... ORM\/Object Relational Mapper, it hides\/abstracts the complexities of SQL and lets you access your data through the simple objects\/models you define in Python. For example, you might have a \"Person\" model with Name, Age, etc. That Name and Age could be stored and retrieved from the database transparently just be accessing the object, without having to write any SQL. (Just a simple .save() and .get())","Q_Score":1,"Tags":"python,mysql,django,new-operator","A_Id":5643494,"CreationDate":"2011-04-13T01:16:00.000","Title":"Beginning MySQL\/Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have just begun learning Python. Eventually I will learn Django, as my goal is to able to do web development (video sharing\/social networking). At which point should I begin learning MySQL? Do I need to know it before I even begin Django? If so, how much should I look to know before diving into Django? Thank you.","AnswerCount":4,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":1826,"Q_Id":5643400,"Users Score":0,"Answer":"As Django documents somehow Recommends, It is better to learning PostgreSQL.\nPostgreSQL is working pretty with Django, I never had any problem with Django\/PostgreSQL.\nI all know is sometimes i have weird error when working with MySQL.","Q_Score":1,"Tags":"python,mysql,django,new-operator","A_Id":5654701,"CreationDate":"2011-04-13T01:16:00.000","Title":"Beginning MySQL\/Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am new to Python and having some rudimentary problems getting MySQLdb up and running.  I'm hoping somebody out there can help me.\nWhen I first tried to install the module using setup.py, the setup terminated because it was unable to find mysql_config.  This is because I didn't realize the module expected MySQL to be installed on the local machine.  I am only trying to connect to a remote MySQL server.\nMy question is twofold:\n1) How should I use MySQLdb on a machine that doesn't have MySQL installed, only to connect to a remote server?\n2) How can I roll back what appears to be a corrupt installation of MySQLdb?  Whenever I try to import MySQLdb from a script, I get the error \"no module named _mysql\", which according to the documentation, indicates a faulty install.\nBTW: I am on a Mac running Snow Leopard\/Python 2.6.1\nThank you!","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":125,"Q_Id":5644374,"Users Score":0,"Answer":"Install the MySQL client libraries.\nInstall the MySQL client library development files, and build again.","Q_Score":0,"Tags":"python,mysql,python-module,mysql-python,setup.py","A_Id":5644390,"CreationDate":"2011-04-13T04:23:00.000","Title":"Help with MySQLdb module: corrupted installation and connecting to remote servers","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am facing a problem where I am trying to add data from a python script to mysql database with InnonDB engine, it works fine with myisam engine of the mysql database. But the problem with the myisam engine is that it doesn't support foreign keys so I'll have to add extra code each place where I want to insert\/delete records in database.  \nDoes anyone know why InnonDB doesn't work with python scripts and possible solutions for this problem ??","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1182,"Q_Id":5654107,"Users Score":6,"Answer":"InnoDB is transactional.  You need to call connection.commit() after inserts\/deletes\/updates.\nEdit:  you can call connection.autocommit(True) to turn on autocommit.","Q_Score":3,"Tags":"python,mysql,innodb,myisam","A_Id":5654733,"CreationDate":"2011-04-13T18:55:00.000","Title":"Problem in insertion from python script in mysql database with innondb engine","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a query set of approximately 1500 records from a Django ORM query.  I have used the select_related() and only() methods to make sure the query is tight.  I have also used connection.queries to make sure there is only this one query.  That is, I have made sure no extra queries are getting called on each iteration.  \nWhen I run the query cut and paste from connection.queries it runs in 0.02 seconds.  However, it takes seven seconds to iterate over those records and do nothing with them (pass).\nWhat can I do to speed this up?  What causes this slowness?","AnswerCount":4,"Available Count":2,"Score":0.1488850336,"is_accepted":false,"ViewCount":4372,"Q_Id":5656238,"Users Score":3,"Answer":"1500 records is far from being a large dataset, and seven seconds is really too much. There is probably some problem in your models, you can easily check it by getting (as Brandon says) the values() query, and then create explicitly the 1500 object by iterating the dictionary. Just convert the ValuesQuerySet into a list before the construction to factor out the db connection.","Q_Score":7,"Tags":"python,django","A_Id":5656734,"CreationDate":"2011-04-13T22:03:00.000","Title":"How do I speed up iteration of large datasets in Django","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a query set of approximately 1500 records from a Django ORM query.  I have used the select_related() and only() methods to make sure the query is tight.  I have also used connection.queries to make sure there is only this one query.  That is, I have made sure no extra queries are getting called on each iteration.  \nWhen I run the query cut and paste from connection.queries it runs in 0.02 seconds.  However, it takes seven seconds to iterate over those records and do nothing with them (pass).\nWhat can I do to speed this up?  What causes this slowness?","AnswerCount":4,"Available Count":2,"Score":0.049958375,"is_accepted":false,"ViewCount":4372,"Q_Id":5656238,"Users Score":1,"Answer":"Does your model's Meta declaration tell it to \"order by\" a field that is stored off in some other related table? If so, your attempt to iterate might be triggering 1,500 queries as Django runs off and grabs that field for each item, and then sorts them. Showing us your code would help us unravel the problem!","Q_Score":7,"Tags":"python,django","A_Id":5657066,"CreationDate":"2011-04-13T22:03:00.000","Title":"How do I speed up iteration of large datasets in Django","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a group of related companies that share items they own with one-another. Each item has a company that owns it and a company that has possession of it. Obviously, the company that owns the item can also have possession of it. Also, companies sometimes permanently transfer ownership of items instead of just lending it, so I have to allow for that as well.\nI'm trying to decide how to model ownership and possession of the items. I have a Company table and an Item table.\nHere are the options as I see them:\n\nInventory table with entries for each Item - Company relationship. Has a company field pointing to a Company and has Boolean fields is_owner and has_possession.\nInventory table with entries for each Item. Has an owner_company field and a possessing_company field that each point to a Company.\nTwo separate tables: ItemOwner and ItemHolder**.\n\nSo far I'm leaning towards option three, but the tables are so similar it feels like duplication. Option two would have only one row per item (cleaner than option one in this regard), but having two fields on one table that both reference the Company table doesn't smell right (and it's messy to draw in an ER diagram!).\nDatabase design is not my specialty (I've mostly used non-relational databases), so I don't know what the best practice would be in this situation. Additionally, I'm brand new to Python and Django, so there might be an obvious idiom or pattern I'm missing out on.\nWhat is the best way to model this without Company and Item being polluted by knowledge of ownership and possession? Or am I missing the point by wanting to keep my models so segregated? What is the Pythonic way?\nUpdate\nI've realized I'm focusing too much on database design. Would it be wise to just write good OO code and let Django's ORM do it's thing?","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":198,"Q_Id":5656345,"Users Score":0,"Answer":"Option #1 is probably the cleanest choice. An Item has only one owner company and is possessed by only one possessing company. \nPut two FK to Company in Item, and remember to explicitly define the related_name of the two inverses to be different each other. \nAs you want to avoid touching the Item model, either add the FKs from outside, like in field.contribute_to_class(), or put a new model with a one-to-one rel to Item, plus the foreign keys. \nThe second method is easier to implement but the first will be more natural to use once implemented.","Q_Score":2,"Tags":"django,design-patterns,database-design,django-models,python","A_Id":5656695,"CreationDate":"2011-04-13T22:17:00.000","Title":"How to model lending items between a group of companies","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am working on a realtime data website that has a data-mining backend side to it. I am highly experienced in both Python and C++\/C#, and wondering which one would be preferable for the backend development.\nI am strongly leaning towards Python for its available libraries and ease of use. But am I wrong? If so, why?\nAs I side question, would you recommend using SQLAlchemy? Are there any drawback to it (performance is crucial) compared to _mysql or MySQLdb?   \nThanks!","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":1302,"Q_Id":5658529,"Users Score":1,"Answer":"We do backend development based on Zope, Python and other Python-related stuff since almost 15 years. Python gives you great flexibility and all-batteries included (likely true for C#, not sure about C++).\nIf you do RDBMS development with Python: SQLAlchemy is the way to go. It provides a huge functionality and saved my a** over the last years a couple of times...Sqlalchemy can be complex and complicated but the advantages is that you can hide a complex database schema behind an OO facade..very handy like any ORM in general. \n_mysql vs MySQLdb...I only know of the python-mysql package.","Q_Score":1,"Tags":"c#,c++,python,backend","A_Id":5658631,"CreationDate":"2011-04-14T04:27:00.000","Title":"Designing a Website Backend - Python or C++\/C#?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am trying to insert a query that contains \u00e9 - or \\xe9 (INSERT INTO tbl1 (text) VALUES (\"fianc\u00e9\")) into a MySQL table in Python using the _mysql module.\nMy query is in unicode, and when I call _mysql.connect(...).query(query) I get a UnicodeEncodeError: 'ascii' codec can't encode character u'\\xe9' in position X\n: ordinal not in range(128).\nObviously the call to query causes a conversion of the unicode string to ASCII somehow, but the question is why? My DB is in utf8 and the connection is opened with the flags use_unicode=True and charset='utf8'. Is unicode simply not supported with _mysql or MySQLdb? Am I missing something else?  \nThanks!","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":522,"Q_Id":5658737,"Users Score":0,"Answer":"I know this doesn't directly answer your question, but why aren't you using prepared statements? That will do two things: probably fix your problem, and almost certainly fix the SQLi bug you've almost certainly got.\nIf you won't do that, are you absolutely certain your string itself is unicode? If you're just naively using strings in python 2.7, it probably is being forced into an ASCII string.","Q_Score":0,"Tags":"python,mysql,unicode","A_Id":5658972,"CreationDate":"2011-04-14T04:55:00.000","Title":"Python MySQL Unicode Error","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm building a WSGI web app and I have a MySQL database. I'm using MySQLdb, which provides cursors for executing statements and getting results. What is the standard practice for getting and closing cursors? In particular, how long should my cursors last? Should I get a new cursor for each transaction?\nI believe you need to close the cursor before committing the connection. Is there any significant advantage to finding sets of transactions that don't require intermediate commits so that you don't have to get new cursors for each transaction? Is there a lot of overhead for getting new cursors, or is it just not a big deal?","AnswerCount":5,"Available Count":1,"Score":-1.0,"is_accepted":false,"ViewCount":99138,"Q_Id":5669878,"Users Score":-6,"Answer":"I suggest to do it like php and mysql. Start i at the beginning of your code before printing of the first data. So if you get a connect error you can display a 50x(Don't remember what internal error is) error message. And keep it open for the whole session and close it when you know you wont need it anymore.","Q_Score":95,"Tags":"python,mysql,mysql-python","A_Id":5670056,"CreationDate":"2011-04-14T21:23:00.000","Title":"When to close cursors using MySQLdb","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am now working on a big backend system for a real-time and history tracking web service.\nI am highly experienced in Python and intend to use it with sqlalchemy (MySQL) to develop the backend.\nI don't have any major experience developing robust and sustainable backend systems and I was wondering if you guys could point me out to some documentation \/ books about backend design patterns? I basically need to feed data to a database by querying different services (over HTML \/ SOAP \/ JSON) at realtime, and to keep history of that data.  \nThanks!","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":4070,"Q_Id":5670639,"Users Score":0,"Answer":"Use Apache, Django and Piston.\nUse REST as the protocol.\nWrite as little code as possible.  \nDjango models, forms, and admin interface.\nPiston wrapppers for your resources.","Q_Score":0,"Tags":"python,backend","A_Id":5671966,"CreationDate":"2011-04-14T22:55:00.000","Title":"Python Backend Design Patterns","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I want to generate compound charts (e.g: Bar+line) from my database using python.\nHow can i do this ?\nThanks in Advance","AnswerCount":4,"Available Count":1,"Score":0.049958375,"is_accepted":false,"ViewCount":277,"Q_Id":5693151,"Users Score":1,"Answer":"Pretty easy to do with pygooglechart - \nYou can basically follow the bar chart examples that ship with the software and then use the add_data_line method to make the lines on top of the bar chart","Q_Score":0,"Tags":"python,charts","A_Id":6272840,"CreationDate":"2011-04-17T11:09:00.000","Title":"Compoud charts with python","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm running django site with MySQL as DB back-end.\nFinally i've got 3 millions rows in django_session table. Most of them are expired, thus i want to remove them.\nBut if i manually run  delete from django_session where expire_date < \"2011-04-18\" whole site seems to be hanged - it cannot be accessed via browser.\nWhy such kind of blocking is possible? How to avoid it?","AnswerCount":4,"Available Count":2,"Score":0.049958375,"is_accepted":false,"ViewCount":513,"Q_Id":5703308,"Users Score":1,"Answer":"I am not MySQL expert, but I guess MySQL locks the table for the deleting and this might be MySQL transaction\/backend related. When deleting is in progress MySQL blocks the access to the table from other connections. MyISAM and InnoDB backend behavior might differ. I suggest you study MySQL manual related to this: the problem is not limited to Django domain, but generally how to delete MySQL rows without blocking access to the table. \nFor the future reference I suggest you set-up a session cleaner task which will clear the sessions, let's say once in a day, from cron so that you don't end up with such huge table.","Q_Score":1,"Tags":"python,mysql,django","A_Id":5703375,"CreationDate":"2011-04-18T13:03:00.000","Title":"MySQL&django hangs on huge session delete","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm running django site with MySQL as DB back-end.\nFinally i've got 3 millions rows in django_session table. Most of them are expired, thus i want to remove them.\nBut if i manually run  delete from django_session where expire_date < \"2011-04-18\" whole site seems to be hanged - it cannot be accessed via browser.\nWhy such kind of blocking is possible? How to avoid it?","AnswerCount":4,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":513,"Q_Id":5703308,"Users Score":5,"Answer":"If your table is MyISAM, DELETE operations lock the table and it is not accessible by the concurrent queries.\nIf there are many records to delete, the table is locked for too long.\nSplit your DELETE statement into several shorter batches.","Q_Score":1,"Tags":"python,mysql,django","A_Id":5703378,"CreationDate":"2011-04-18T13:03:00.000","Title":"MySQL&django hangs on huge session delete","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have had a virtualenv for Trunk up and running for a while, but now I am trying to branch, and get things setup on another virtualenv for my 'refactor' branch.\nEverything looks to be setup correctly, but when I try to run any manage.py commands, I get this error:\n_mysql_exceptions.OperationalError: (1045, \"Access denied for user 'brian'@'localhost' (using password: NO)\")\nI just don't understand why it's not attempting to use the password I have set in my django settings file.  Is there some addition mysql setup I could have overlooked?  Does this issue ring any bells for anyone?\nThanks in advance.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1450,"Q_Id":5726440,"Users Score":1,"Answer":"I found the problem I was having. \nDjango was importing a different settings.py file.\nI had another django project inside my django product like myproject\/myproject\/. \nInstead of importing myproject\/settings.py, it was importing myproject\/myproject\/settings.py\nI assume that Aptana Studio created that project there. If you use eclipse you are also likely to have this problem.","Q_Score":1,"Tags":"python,mysql,django,mysql-error-1045","A_Id":8742834,"CreationDate":"2011-04-20T06:39:00.000","Title":"Can't access MySQL database in Django VirtualEnv on localhost","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"In Python, is there a way to get notified that a specific table in a MySQL database has changed?","AnswerCount":5,"Available Count":2,"Score":0.0399786803,"is_accepted":false,"ViewCount":30571,"Q_Id":5771925,"Users Score":1,"Answer":"Not possible with standard SQL functionality.","Q_Score":10,"Tags":"python,mysql","A_Id":5771943,"CreationDate":"2011-04-24T17:03:00.000","Title":"python: how to get notifications for mysql database changes?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"In Python, is there a way to get notified that a specific table in a MySQL database has changed?","AnswerCount":5,"Available Count":2,"Score":1.0,"is_accepted":false,"ViewCount":30571,"Q_Id":5771925,"Users Score":10,"Answer":"It's theoretically possible but I wouldn't recommend it:\nEssentially you have a trigger on the the table the calls a UDF which communicates with your Python app in some way.\nPitfalls include what happens if there's an error?  \nWhat if it blocks?  Anything that happens inside a trigger should ideally be near-instant.\nWhat if it's inside a transaction that gets rolled back?\nI'm sure there are many other problems that I haven't thought of as well.\nA better way if possible is to have your data access layer notify the rest of your app.  If you're looking for when a program outside your control modifies the database, then you may be out of luck.\nAnother way that's less ideal but imo better than calling an another program from within a trigger is to set some kind of \"LastModified\" table that gets updated by triggers with triggers.  Then in your app just check whether that datetime is greater than when you last checked.","Q_Score":10,"Tags":"python,mysql","A_Id":5771988,"CreationDate":"2011-04-24T17:03:00.000","Title":"python: how to get notifications for mysql database changes?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am developing a database based django application and I have installed apache, python and django using macport on a snow leopard machine. I ran into issues installing MySQL with macport. But I was able to successfully install a standalone MySQL server (from MySQL.com). Is it possible to remove the MysQL package installed along with py26-MySQL?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":182,"Q_Id":5782875,"Users Score":2,"Answer":"To use py26-mysql you don't need the entire server distribution for MySQL. You do need the client libs, at the very least. If you remove the server, you need to make sure you re-install the base libraries needed by the Python module to function.","Q_Score":0,"Tags":"python,mysql,macports","A_Id":5782960,"CreationDate":"2011-04-25T20:26:00.000","Title":"Is it possible to install py26-mysql without installing mysql5 package?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have some database structure; as most of it is irrelevant for us, i'll describe just some relevant pieces. Let's lake Item object as example:\nitems_table = Table(\"invtypes\", gdata_meta,\n                    Column(\"typeID\", Integer, primary_key = True),\n                    Column(\"typeName\", String, index=True),\n                    Column(\"marketGroupID\", Integer, ForeignKey(\"invmarketgroups.marketGroupID\")),\n                    Column(\"groupID\", Integer, ForeignKey(\"invgroups.groupID\"), index=True))\n\nmapper(Item, items_table,\n       properties = {\"group\" : relation(Group, backref = \"items\"),\n                     \"_Item__attributes\" : relation(Attribute, collection_class = attribute_mapped_collection('name')),\n                     \"effects\" : relation(Effect, collection_class = attribute_mapped_collection('name')),\n                     \"metaGroup\" : relation(MetaType,\n                                            primaryjoin = metatypes_table.c.typeID == items_table.c.typeID,\n                                            uselist = False),\n                     \"ID\" : synonym(\"typeID\"),\n                     \"name\" : synonym(\"typeName\")})\nI want to achieve some performance improvements in the sqlalchemy\/database layer, and have couple of ideas:\n1) Requesting the same item twice:\nitem = session.query(Item).get(11184)\nitem = None (reference to item is lost, object is garbage collected)\nitem = session.query(Item).get(11184)\nEach request generates and issues SQL query. To avoid it, i use 2 custom maps for an item object:\nitemMapId = {}\nitemMapName = {}\n\n@cachedQuery(1, \"lookfor\")\ndef getItem(lookfor, eager=None):\n    if isinstance(lookfor, (int, float)):\n        id = int(lookfor)\n        if eager is None and id in itemMapId:\n            item = itemMapId[id]\n        else:\n            item = session.query(Item).options(*processEager(eager)).get(id)\n            itemMapId[item.ID] = item\n            itemMapName[item.name] = item\n    elif isinstance(lookfor, basestring):\n        if eager is None and lookfor in itemMapName:\n            item = itemMapName[lookfor]\n        else:\n            # Items have unique names, so we can fetch just first result w\/o ensuring its uniqueness\n            item = session.query(Item).options(*processEager(eager)).filter(Item.name == lookfor).first()\n            itemMapId[item.ID] = item\n            itemMapName[item.name] = item\n    return item\nI believe sqlalchemy does similar object tracking, at least by primary key (item.ID). If it does, i can wipe both maps (although wiping name map will require minor modifications to application which uses these queries) to not duplicate functionality and use stock methods. Actual question is: if there's such functionality in sqlalchemy, how to access it?\n2) Eager loading of relationships often helps to save alot of requests to database. Say, i'll definitely need following set of item=Item() properties:\nitem.group (Group object, according to groupID of our item)\nitem.group.items (fetch all items from items list of our group)\nitem.group.items.metaGroup (metaGroup object\/relation for every item in the list)\nIf i have some item ID and no item is loaded yet, i can request it from the database, eagerly loading everything i need: sqlalchemy will join group, its items and corresponding metaGroups within single query. If i'd access them with default lazy loading, sqlalchemy would need to issue 1 query to grab an item + 1 to get group + 1*#items for all items in the list + 1*#items to get metaGroup of each item, which is wasteful.\n2.1) But what if i already have Item object fetched, and some of the properties which i want to load are already loaded? As far as i understand, when i re-fetch some object from the database - its already loaded relations do not become unloaded, am i correct?\n2.2) If i have Item object fetched, and want to access its group, i can just getGroup using item.groupID, applying any eager statements i'll need (\"items\" and \"items.metaGroup\"). It should properly load group and its requested relations w\/o touching item stuff. Will sqlalchemy properly map this fetched group to item.group, so that when i access item.group it won't fetch anything from the underlying database?\n2.3) If i have following things fetched from the database: original item, item.group and some portion of the items from the item.group.items list some of which may have metaGroup loaded, what would be best strategy for completing data structure to the same as eager list above: re-fetch group with (\"items\", \"items.metaGroup\") eager load, or check each item from items list individually, and if item or its metaGroup is not loaded - load them? It seems to depend on the situation, because if everything has already been loaded some time ago - issuing such heavy query is pointless. Does sqlalchemy provide a way to track if some object relation is loaded, with the ability to look deeper than just one level?\nAs an illustration to 2.3 - i can fetch group with ID 83, eagerly fetching \"items\" and \"items.metaGroup\". Is there a way to determine from an item (which has groupID of an 83), does it have \"group\", \"group.items\" and \"group.items.metaGroup\" loaded or not, using sqlalchemy tools (in this case all of them should be loaded)?","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":3854,"Q_Id":5795492,"Users Score":7,"Answer":"To force loading lazy attributes just access them. This the simplest way and it works fine for relations, but is not as efficient for Columns (you will get separate SQL query for each column in the same table). You can get a list of all unloaded properties (both relations and columns) from sqlalchemy.orm.attributes.instance_state(obj).unloaded.\nYou don't use deferred columns in your example, but I'll describe them here for completeness. The typical scenario for handling deferred columns is the following:\n\nDecorate selected columns with deferred(). Combine them into one or several groups by using group parameter to deferred().\nUse undefer() and undefer_group() options in query when desired.\nAccessing deferred column put in group will load all columns in this group.\n\nUnfortunately this doesn't work reverse: you can combine columns into groups without deferring loading of them by default with column_property(Column(\u2026), group=\u2026), but defer() option won't affect them (it works for Columns only, not column properties, at least in 0.6.7).\nTo force loading deferred column properties session.refresh(obj, attribute_names=\u2026) suggested by Nathan Villaescusa is probably the best solution. The only disadvantage I see is that it expires attributes first so you have to insure there is not loaded attributes among passed as attribute_names argument (e.g. by using intersection with state.unloaded).\nUpdate\n1) SQLAlchemy does track loaded objects. That's how ORM works: there must be the only object in the session for each identity. Its internal cache is weak by default (use weak_identity_map=False to change this), so the object is expunged from the cache as soon as there in no reference to it in your code. SQLAlchemy won't do SQL request for query.get(pk) when object is already in the session. But this works for get() method only, so query.filter_by(id=pk).first() will do SQL request and refresh object in the session with loaded data.\n2) Eager loading of relations will lead to fewer requests, but it's not always faster. You have to check this for your database and data.\n2.1) Refetching data from database won't unload objects bound via relations.\n2.2) item.group is loaded using query.get() method, so there won't lead to SQL request if object is already in the session.\n2.3) Yes, it depends on situation. For most cases it's the best is to hope SQLAlchemy will use the right strategy :). For already loaded relation you can check if related objects' relations are loaded via state.unloaded and so recursively to any depth. But when relation is not loaded yet you can't get know whether related objects and their relations are already loaded: even when relation is not yet loaded the related object[s] might be already in the session (just imagine you request first item, load its group and then request other item that has the same group). For your particular example I see no problem to just check state.unloaded recursively.","Q_Score":7,"Tags":"python,sqlalchemy,eager-loading","A_Id":5819858,"CreationDate":"2011-04-26T19:35:00.000","Title":"Completing object with its relations and avoiding unnecessary queries in sqlalchemy","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"We're currently in the process of implementing a CRM-like solution internally for a professional firm. Due to the nature of the information stored, and the varying values and keys for the information we decided to use a document storage database, as it suited the purposes perfectly (In this case we chose MongoDB).\nAs part of this CRM solution we wish to store relationships and associations between entities, examples include storing conflicts of interest information, shareholders, trustees etc. Linking all these entities together in the most effective way we determined a central model of \"relationship\" was necessary. All relationships should have history information attached to them ( commencement and termination dates), as well as varying meta data; for example a shareholder relationship would also contain number of shares held.\nAs traditional RDBMS solutions didn't suit our former needs, using them in our current situation is not viable. What I'm trying to determine is whether using a graph database is more pertinent in our case, or if in fact just using mongo's built-in relational information is appropriate.\nThe relationship information is going to be used quite heavily throughout the system. An example of some of the informational queries we wish to perform are:\n\nGet all 'key contact' people of companies who are 'clients' of 'xyz limited'\nGet all other 'shareholders' of companies where 'john' is a shareholder\nGet all 'Key contact' people of entities who are 'clients' of 'abc limited' and are clients of 'trust us bank limited'\n\nGiven this \"tree\" structure of relationships, is using a graph database (such as Neo4j) more appropriate?","AnswerCount":4,"Available Count":2,"Score":0.049958375,"is_accepted":false,"ViewCount":2546,"Q_Id":5817182,"Users Score":1,"Answer":"stay with mongodb. Two reasons - 1. its better to stay in the same domain if you can to reduce complexity and 2. mongodb is excellent for querying and requires less work than redis, for example.","Q_Score":16,"Tags":"python,django,mongodb,redis,neo4j","A_Id":5821550,"CreationDate":"2011-04-28T10:28:00.000","Title":"Using MongoDB as our master database, should I use a separate graph database to implement relationships between entities?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"We're currently in the process of implementing a CRM-like solution internally for a professional firm. Due to the nature of the information stored, and the varying values and keys for the information we decided to use a document storage database, as it suited the purposes perfectly (In this case we chose MongoDB).\nAs part of this CRM solution we wish to store relationships and associations between entities, examples include storing conflicts of interest information, shareholders, trustees etc. Linking all these entities together in the most effective way we determined a central model of \"relationship\" was necessary. All relationships should have history information attached to them ( commencement and termination dates), as well as varying meta data; for example a shareholder relationship would also contain number of shares held.\nAs traditional RDBMS solutions didn't suit our former needs, using them in our current situation is not viable. What I'm trying to determine is whether using a graph database is more pertinent in our case, or if in fact just using mongo's built-in relational information is appropriate.\nThe relationship information is going to be used quite heavily throughout the system. An example of some of the informational queries we wish to perform are:\n\nGet all 'key contact' people of companies who are 'clients' of 'xyz limited'\nGet all other 'shareholders' of companies where 'john' is a shareholder\nGet all 'Key contact' people of entities who are 'clients' of 'abc limited' and are clients of 'trust us bank limited'\n\nGiven this \"tree\" structure of relationships, is using a graph database (such as Neo4j) more appropriate?","AnswerCount":4,"Available Count":2,"Score":1.0,"is_accepted":false,"ViewCount":2546,"Q_Id":5817182,"Users Score":6,"Answer":"The documents in MongoDB very much resemble nodes in Neo4j, minus the relationships. They both hold key-value properties. If you've already made the choice to go with MongoDB, then you can use Neo4j to store the relationships and then bridge the stores in your application. If you're choosing new technology, you can go with Neo4j for everything, as the nodes can hold property data just as well as documents can. \nAs for the relationship part, Neo4j is a great fit. You have a graph, not unrelated documents. Using a graph database makes perfect sense here, and the sample queries have graph written all over them. \nHonestly though, the best way to find out what works for you is to do a PoC - low cost, high value.\nDisclaimer: I work for Neo Technology.","Q_Score":16,"Tags":"python,django,mongodb,redis,neo4j","A_Id":5836158,"CreationDate":"2011-04-28T10:28:00.000","Title":"Using MongoDB as our master database, should I use a separate graph database to implement relationships between entities?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I built a previous program that took client info and stored it in a folder of txt files (impractical much) but now I want to upgrade the program to be more efficient and put the info into a database of some sort...\nHow can I take the info from the text files and add them to the new database without having to manually do each one. I know this is vague but I need more so the method\/logic instead of the exact code, Also if I don't use SQL what is another method for making a db (Not using another commercial Db)\nbtw the txt files are in simple format (name,city,age) all on separate lines for easy iteration","AnswerCount":5,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":5085,"Q_Id":5823236,"Users Score":0,"Answer":"The main reason for DB to have a SQL is to make it separate and generic from the application that you are developing.\nTo have your own DB built you need to have a storage mechanism could be files on the hard disk, with search options so that you can access data immediately with keywords that you are interested in. on top of this you have to have a layer that initiates queues, reads them and translates to the lower file read and write functions. you need to have this queue layer because lets say you have 100 applications and all are trying to read and write from the same file at the same time and you can imagine what can happen to the file . there will be access denied , somebody using it, data corrupted etc etc.. so you need to put all these in queue and let this queue layer translate things for you.\nto start with start from different ways of reading\/writing\/sorting of data into the file, and a queue layer. From there you can build applications. \nThe queue layer here is similar to the client that is trying to push the data into the communication port in most of the available databases.","Q_Score":2,"Tags":"python,database","A_Id":15442076,"CreationDate":"2011-04-28T18:21:00.000","Title":"If I want to build a custom database, how could I?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Is it possible to save my in-memory sqlite database to hard disk?\nIf it is possible, some python code would be awesome.\nThanks in advance.\nEDIT:\nI succeeded this task by using apsw . It works like a charm. Thanks for your contribution.","AnswerCount":7,"Available Count":3,"Score":1.0,"is_accepted":false,"ViewCount":13227,"Q_Id":5831548,"Users Score":6,"Answer":"Yes. When you create the connection to the database, replace :memory: with the path where you want to save the DB.\nsqlite uses caches for file based DBs, so this shouldn't be (much) slower.","Q_Score":19,"Tags":"python,sqlite","A_Id":5832180,"CreationDate":"2011-04-29T11:43:00.000","Title":"python save in memory sqlite","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Is it possible to save my in-memory sqlite database to hard disk?\nIf it is possible, some python code would be awesome.\nThanks in advance.\nEDIT:\nI succeeded this task by using apsw . It works like a charm. Thanks for your contribution.","AnswerCount":7,"Available Count":3,"Score":1.0,"is_accepted":false,"ViewCount":13227,"Q_Id":5831548,"Users Score":13,"Answer":"(Disclosure:  I am the APSW author)\nThe only safe way to make a binary copy of a database is to use the backup API that is part of SQLite and is exposed by APSW.  This does the right thing with ordering, locking and concurrency.\nTo make a SQL (text) copy of the a database then use the APSW shell which includes a .dump implementation that is very complete.  You can use cursor.execute() to turn the SQL back into a database.\nOn recent platforms you are unlikely to see much of a difference between a memory database and a disk one (assuming you turned journaling off for the disk) as the operating system maintains a file system cache.  Older operating systems like Windows XP did have a default configuration of only using 10MB of memory for file cache no matter how much RAM you have.","Q_Score":19,"Tags":"python,sqlite","A_Id":5925061,"CreationDate":"2011-04-29T11:43:00.000","Title":"python save in memory sqlite","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Is it possible to save my in-memory sqlite database to hard disk?\nIf it is possible, some python code would be awesome.\nThanks in advance.\nEDIT:\nI succeeded this task by using apsw . It works like a charm. Thanks for your contribution.","AnswerCount":7,"Available Count":3,"Score":0.0285636566,"is_accepted":false,"ViewCount":13227,"Q_Id":5831548,"Users Score":1,"Answer":"Open a disk based database and just copy everything from one to the other.","Q_Score":19,"Tags":"python,sqlite","A_Id":5831644,"CreationDate":"2011-04-29T11:43:00.000","Title":"python save in memory sqlite","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"In MySQL, I have two different databases -- let's call them A and B.\nDatabase A resides on server server1, while database B resides on server server2.\nBoth servers {A, B} are physically close to each other, but are on different machines and have different connection parameters (different username, different password etc).\nIn such a case, is it possible to perform a join between a table that is in database A, to a table that is in database B?\nIf so, how do I go about it, programatically, in python? (I am using python's MySQLDB to separately interact with each one of the databases).","AnswerCount":3,"Available Count":2,"Score":0.2605204458,"is_accepted":false,"ViewCount":32061,"Q_Id":5832787,"Users Score":4,"Answer":"It is very simple - select data from one server, select data from another server and aggregate using Python. If you would like to have SQL query with JOIN - put result from both servers into separate tables in local SQLite database and write SELECT with JOIN.","Q_Score":29,"Tags":"python,mysql","A_Id":5832825,"CreationDate":"2011-04-29T13:36:00.000","Title":"MySQL -- Joins Between Databases On Different Servers Using Python?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"In MySQL, I have two different databases -- let's call them A and B.\nDatabase A resides on server server1, while database B resides on server server2.\nBoth servers {A, B} are physically close to each other, but are on different machines and have different connection parameters (different username, different password etc).\nIn such a case, is it possible to perform a join between a table that is in database A, to a table that is in database B?\nIf so, how do I go about it, programatically, in python? (I am using python's MySQLDB to separately interact with each one of the databases).","AnswerCount":3,"Available Count":2,"Score":0.1973753202,"is_accepted":false,"ViewCount":32061,"Q_Id":5832787,"Users Score":3,"Answer":"No. It is not possible to do the join as you would like. But you may be able to sort something out by replicating one of the servers to the other for the individual database. \nOne data set is under the control of one copy of MySQL and the other dataset is under the control of the other copy of MySQL. The query can only be processed by one of the (MySQL) servers.\nIf you create a copy of the second database on the first server or vice versa (the one that gets the fewest updates is best) you can set up replication to keep the copy up to date. You will then be able to run the query as you want.","Q_Score":29,"Tags":"python,mysql","A_Id":5832954,"CreationDate":"2011-04-29T13:36:00.000","Title":"MySQL -- Joins Between Databases On Different Servers Using Python?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Here's what I want to do.\nDevelop a Django project on a development server with a development database.  Run the south migrations as necessary when I change the model.\nSave the SQL from each migration, and apply those to the production server when I'm ready to deploy.\nIs such a thing possible with South?  (I'd also be curious what others do to get your development database changes on production when working with Django)","AnswerCount":5,"Available Count":2,"Score":1.0,"is_accepted":false,"ViewCount":10745,"Q_Id":5833418,"Users Score":50,"Answer":"You can at least inspect the sql generated by doing manage.py migrate --db-dry-run --verbosity=2. This will not do anything to the database and will show all the sql. I would still make a backup though, better safe than sorry.","Q_Score":28,"Tags":"python,database,migration,django-south","A_Id":5897509,"CreationDate":"2011-04-29T14:32:00.000","Title":"Django - South - Is There a way to view the SQL it runs?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Here's what I want to do.\nDevelop a Django project on a development server with a development database.  Run the south migrations as necessary when I change the model.\nSave the SQL from each migration, and apply those to the production server when I'm ready to deploy.\nIs such a thing possible with South?  (I'd also be curious what others do to get your development database changes on production when working with Django)","AnswerCount":5,"Available Count":2,"Score":0.0798297691,"is_accepted":false,"ViewCount":10745,"Q_Id":5833418,"Users Score":2,"Answer":"I'd either do what Lutger suggested (and maybe write a log parser to strip out just the SQL), or I'd run my migration against a test database with logging enabled on the test DB.\nOf course, if you can run it against the test database, you're just a few steps away from validating the migration.  If it passes, run it again against production.","Q_Score":28,"Tags":"python,database,migration,django-south","A_Id":5932967,"CreationDate":"2011-04-29T14:32:00.000","Title":"Django - South - Is There a way to view the SQL it runs?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"In my server process, it looks like this:\nMain backend processes:\n\nProcesses Huge list of files and , record them inside MySQL.\nOn every 500 files done, it writes \"Progress Report\" to a separate file \/var\/run\/progress.log like this \"200\/5000 files done\"\nIt is multi-processed with 4 children, each made sure to run on a separate file.\n\nWeb server process:\n\nRead the output of \/var\/run\/progress.log every 10 seconds via Ajax and report to progress bar.\n\nWhen processing a very large list of files (e.g. over 3 GB archive), the processes lock up after about 2 hours of processing.\nI can't find what is going on. Does that mean that \/var\/run\/progress.log caused an I\/O deadlock?","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":773,"Q_Id":5848184,"Users Score":0,"Answer":"Quick advice, make sure (like, super sure) that you do close your file.\nSo ALWAYS use a try-except-final block for this\nRemember that the contens of a final block will ALWAYS be executed, that will prevent you a lot of head pain :)","Q_Score":1,"Tags":"python,linux,performance,io,deadlock","A_Id":12211059,"CreationDate":"2011-05-01T11:55:00.000","Title":"If I open and read the file which is periodically written, can I\/O deadlock occur?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I'm working with Tornado and MongoDB and I would like to send a confirmation email to the user when he creates an account in my application.\nFor the moment, I use a simple XHTML page with a form and I send information to my MongoDB database using Tornado. I would like to have an intermediate step which sends an email to the user before inserting the data into the database.\nI would like to know how could I send this email and insert the user account only after the user receives the email and confirms his registration.","AnswerCount":2,"Available Count":1,"Score":1.0,"is_accepted":false,"ViewCount":3734,"Q_Id":5862238,"Users Score":6,"Answer":"I wonder why you would handle registration like that. The usual way to handle registration is:\n\nWrite the user info to the database, but with an 'inactive' label attached to the user.\nSend an email to the user.\nIf the user confirms the registration, then switch the user to 'active'.\n\nIf you don't want to write to the database, you can write to a cache (like memcache, redis), then when the user confirms the registration, you can get the user info from the cache and write it to the database.","Q_Score":5,"Tags":"python,email,tornado","A_Id":7483440,"CreationDate":"2011-05-02T20:41:00.000","Title":"How can I send a user registration confirmation email using Tornado and MongoDB?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"The identity map and unit of work patterns are part of the reasons sqlalchemy is much more attractive than django.db. However, I am not sure how the identity map would work, or if it works when an application is configured as wsgi and the orm is accessed directly through api calls, instead of a shared service. I would imagine that apache would create a new thread with its own python instance for each request. Each instance would therefore have their own instance of the sqlalchemy classes and not be able to make use of the identity map. Is this correct?","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":2298,"Q_Id":5869514,"Users Score":0,"Answer":"So this all depends on how you setup your sqlalchemy connection. Normally what you do is to manage each wsgi request to have it's own threadlocal session. This session will know about all of the goings-on of it, items added\/changed\/etc. However, each thread is not aware of the others. In this way the loading\/preconfiguring of the models and mappings is shared during startup time, however each request can operate independent of the others.","Q_Score":6,"Tags":"python,sqlalchemy,identity-map","A_Id":5869588,"CreationDate":"2011-05-03T12:35:00.000","Title":"sqlalchemy identity map question","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a data model called Game.\nIn the Game model, I have two properties called player1 and player2 which are their names.\nI want to find a player in gamebut I don't know how to buil the query because gql does not support OR clause and then I can't use select * from Game where player1 = 'tom' or player2 = 'tom' statement.\nSo, how can I solve this question?\nDo I have to modify my data model?","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":631,"Q_Id":5875881,"Users Score":0,"Answer":"Note that there is no gain of performance in using Drew's schema, because queries in list properties must check for equality against all the elements of the list.","Q_Score":3,"Tags":"python,google-app-engine","A_Id":10265451,"CreationDate":"2011-05-03T21:24:00.000","Title":"Google app engine gql query two properties with same string","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Can i use Berkeley DB  python classes in mobile phone directly , i mean Do DB python classes and methods are ready to be used in any common mobile phone like Nokia,Samsong (windows mobile)..etc.\nIf a phone system supports python language, does that mean that it is easy and straightforward to use Berkeley DB on it...","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":159,"Q_Id":5888854,"Users Score":1,"Answer":"Berkeley DB is a library that needs to be available. What you may have is Python bindings to Berkeley DB. If the library is not present, having Python will not help.\nLook for SQLite, which may be present (it is for iPhone) as it has SQL support and its library size is smaller than Berkeley DB, which makes it better suited for mobile OSes.","Q_Score":0,"Tags":"python,database,mobile,windows-mobile,berkeley-db","A_Id":5888966,"CreationDate":"2011-05-04T19:30:00.000","Title":"Can use Berkeley DB in mobile phone","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"A primary goal of a project I plan to bid on involves creating a Microsoft Access database using python. The main DB backend will be postgres, but the plan is to export an Access image.\nThis will be a web app that'll take input from the user and go through a black box and output the results as an access db. The web app will be built on a linux server.\nI have a few related questions:\n\nIs there a reliable library or module that can be used?\nWhat has your experience been using Access and python?\nAny tips, tricks, or must avoids I need to know about?\n\nThanks :)","AnswerCount":8,"Available Count":4,"Score":0.049958375,"is_accepted":false,"ViewCount":3427,"Q_Id":5891359,"Users Score":2,"Answer":"The various answers to the duplicate question suggest that your \"primary goal\" of creating an MS Access database on a linux server is not attainable.\nOf course, such a goal is of itself not worthwhile at all. If you tell us what the users\/consumers of the Access db are expected to do with it, maybe we can help you. Possibilities: (1) create a script and a (set of) file(s) which the user downloads and runs to create an Access DB (2) if it's just for casual user examination\/manipulation, an Excel file may do.","Q_Score":7,"Tags":"python,linux,ms-access","A_Id":5925032,"CreationDate":"2011-05-05T00:26:00.000","Title":"Building an MS Access database using python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"A primary goal of a project I plan to bid on involves creating a Microsoft Access database using python. The main DB backend will be postgres, but the plan is to export an Access image.\nThis will be a web app that'll take input from the user and go through a black box and output the results as an access db. The web app will be built on a linux server.\nI have a few related questions:\n\nIs there a reliable library or module that can be used?\nWhat has your experience been using Access and python?\nAny tips, tricks, or must avoids I need to know about?\n\nThanks :)","AnswerCount":8,"Available Count":4,"Score":0.0,"is_accepted":false,"ViewCount":3427,"Q_Id":5891359,"Users Score":0,"Answer":"Could you create a self-extracting file to send to the Windows user who has Microsoft Access installed?\n\nInclude a blank .mdb file.\ndynamically build xml documents with tables, schema\nand data\nInclude an import executable that will take\nall of the xml docs and import into\nthe Access .mdb file.\n\nIt's an extra step for the user, but you get to rely on their existing drivers, software and desktop.","Q_Score":7,"Tags":"python,linux,ms-access","A_Id":5954299,"CreationDate":"2011-05-05T00:26:00.000","Title":"Building an MS Access database using python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"A primary goal of a project I plan to bid on involves creating a Microsoft Access database using python. The main DB backend will be postgres, but the plan is to export an Access image.\nThis will be a web app that'll take input from the user and go through a black box and output the results as an access db. The web app will be built on a linux server.\nI have a few related questions:\n\nIs there a reliable library or module that can be used?\nWhat has your experience been using Access and python?\nAny tips, tricks, or must avoids I need to know about?\n\nThanks :)","AnswerCount":8,"Available Count":4,"Score":0.049958375,"is_accepted":false,"ViewCount":3427,"Q_Id":5891359,"Users Score":2,"Answer":"If you know this well enough:\n\nPython, it's database modules, and ODBC configuration\n\nthen you should know how to do this:\n\nopen a database, read some data, insert it in to a different database\n\nIf so, then you are very close to your required solution. The trick is, you can open an MDB file as an ODBC datasource.  Now: I'm not sure if you can \"CREATE TABLES\" with ODBC in an MDB file, so let me propose this recipe:\n\nCreate an MDB file with name \"TARGET.MDB\" -- with the necessary tables, forms, reports, etc.  (Put some dummy data in and test that it is what the customer would want.)\nSet up an ODBC datasource to the file \"TARGET.MDB\".  Test to make sure you can read\/write.\nRemove all the dummy data -- but leave the table defs intact.  Rename the file \"TEMPLATE.MDB\".\nWhen you need to generate a new MDB file: with Python copy TEMPLATE.MDB to TARGET.MDB.\nOpen the datasource to write to TARGET.MDB.  Create\/copy required records.\nClose the datasource, rename TARGET.MDB to TODAYS_REPORT.MDB... or whatever makes sense for this particular data export.\n\nWould that work for you?\nIt would almost certainly be easier to do that all on Windows as the support for ODBC will be most widely available.  However, I think in principle you could do this on Linux, provided you find the right ODBC components to access MDB via ODBC.","Q_Score":7,"Tags":"python,linux,ms-access","A_Id":5964496,"CreationDate":"2011-05-05T00:26:00.000","Title":"Building an MS Access database using python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"A primary goal of a project I plan to bid on involves creating a Microsoft Access database using python. The main DB backend will be postgres, but the plan is to export an Access image.\nThis will be a web app that'll take input from the user and go through a black box and output the results as an access db. The web app will be built on a linux server.\nI have a few related questions:\n\nIs there a reliable library or module that can be used?\nWhat has your experience been using Access and python?\nAny tips, tricks, or must avoids I need to know about?\n\nThanks :)","AnswerCount":8,"Available Count":4,"Score":0.0,"is_accepted":false,"ViewCount":3427,"Q_Id":5891359,"Users Score":0,"Answer":"Well, looks to me like you need a copy of vmware server on the linux box running windows, a web service in the vm to write to access, and communications to it from the main linux box. You aren't going to find a means of creating an access db on Linux. Calling it a requirement isn't going to make it technically possible.","Q_Score":7,"Tags":"python,linux,ms-access","A_Id":5972450,"CreationDate":"2011-05-05T00:26:00.000","Title":"Building an MS Access database using python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm working with the BeautifulSoup python library.\nI used the urllib2 library to download the HTML code from a page, and then I have parsed it with BeautifulSoup.\nI want to save some of the HTML content into a MySql table, but I'm having some problems with the encoding. The MySql table is encoded with 'utf-8' charset.\nSome examples:\nWhen I download the HTML code and parse it with BeautifulSoup I have something like:\n\"Ver las \\xc3\\xbaltimas noticias. Ent\\xc3\\xa9rate de las noticias de \\xc3\\xbaltima hora con la mejor cobertura con fotos y videos\"\nThe correct text would be:\n\"Ver las \u00faltimas noticias. Ent\u00e9rate de las noticias de \u00faltima hora con la mejor cobertura con fotos y videos\"\nI have tried to encode and decode that text with multiple charsets, but when I insert it into MySql I have somethig like:\n\"Ver las \u00c3\u00baltimas noticias y todos los titulares de hoy en Yahoo! Noticias Argentina. Ent\u00c3\u00a9rate de las noticias de \u00c3\u00baltima hora con la mejor cobertura con fotos y videos\"\nI'm having problems with the encoding, but I don't know how to solve them.\nAny suggestion?","AnswerCount":2,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":693,"Q_Id":5902914,"Users Score":2,"Answer":"BeautifulSoup returns all data as unicode strings. First triple check that the unicode strings are ccorrect. If not then there is some issue with the encoding of the input data.","Q_Score":2,"Tags":"python,mysql,encoding,urllib2,beautifulsoup","A_Id":5903100,"CreationDate":"2011-05-05T19:12:00.000","Title":"Wrong encoding with Python BeautifulSoup + MySql","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm using PyCrypto to store some files inside a SQLITE database.\nI'm using 4 fields :\nthe name of the file,\nthe length of the file (in bytes)\nthe SHA512 hash of the file\nthe encrypted file (with AES and then base64 to ASCII).\nI need all the fields to show some info about the file without decrypting it.\nThe question is : is it secure to store the data like this ?\nFor example, the first characters of a ZIP file, or executable file are always the same, and if you already know the hash and the length of the file ... is it possible to decrypt the file, maybe partially ?\nIf it's not secure, how can I store some information about the file to index the files without decrypting them ? (information like length, hash, name, tags, etc)\n(I use python, but you can give examples in any language)","AnswerCount":4,"Available Count":3,"Score":0.1488850336,"is_accepted":false,"ViewCount":484,"Q_Id":5919819,"Users Score":3,"Answer":"Data encrypted with AES has the same length as the plain data (give or take some block padding), so giving original length away doesn't harm security. SHA512 is a strong cryptographic hash designed to provide minimal information about the original content, so I don't see a problem here either.\nTherefore, I think your scheme is quite safe. Any information \"exposed\" by it is negligible. Key management will probably be a much bigger concern anyway.","Q_Score":3,"Tags":"python,database,security,encryption","A_Id":5919875,"CreationDate":"2011-05-07T07:56:00.000","Title":"Storing encrypted files inside a database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm using PyCrypto to store some files inside a SQLITE database.\nI'm using 4 fields :\nthe name of the file,\nthe length of the file (in bytes)\nthe SHA512 hash of the file\nthe encrypted file (with AES and then base64 to ASCII).\nI need all the fields to show some info about the file without decrypting it.\nThe question is : is it secure to store the data like this ?\nFor example, the first characters of a ZIP file, or executable file are always the same, and if you already know the hash and the length of the file ... is it possible to decrypt the file, maybe partially ?\nIf it's not secure, how can I store some information about the file to index the files without decrypting them ? (information like length, hash, name, tags, etc)\n(I use python, but you can give examples in any language)","AnswerCount":4,"Available Count":3,"Score":1.2,"is_accepted":true,"ViewCount":484,"Q_Id":5919819,"Users Score":1,"Answer":"To avoid any problems concerning the first few bytes being the same, you should use AES in Block Cipher mode with a random IV. This ensures that even if the first block (length depends on the key size) of two encrypted files is exactly the same, the cipher text will be different.\nIf you do that, I see no problem with your approach.","Q_Score":3,"Tags":"python,database,security,encryption","A_Id":5920346,"CreationDate":"2011-05-07T07:56:00.000","Title":"Storing encrypted files inside a database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm using PyCrypto to store some files inside a SQLITE database.\nI'm using 4 fields :\nthe name of the file,\nthe length of the file (in bytes)\nthe SHA512 hash of the file\nthe encrypted file (with AES and then base64 to ASCII).\nI need all the fields to show some info about the file without decrypting it.\nThe question is : is it secure to store the data like this ?\nFor example, the first characters of a ZIP file, or executable file are always the same, and if you already know the hash and the length of the file ... is it possible to decrypt the file, maybe partially ?\nIf it's not secure, how can I store some information about the file to index the files without decrypting them ? (information like length, hash, name, tags, etc)\n(I use python, but you can give examples in any language)","AnswerCount":4,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":484,"Q_Id":5919819,"Users Score":0,"Answer":"You really need to think about what attacks you want to protect against, and the resources of the possible attackers.\nIn general, storing some data encrypted is only useful if it satisfies your exact requirements. In particular, if there is a way an attacker could compromise the key at the same time as the data, then the encryption is effectively useless.","Q_Score":3,"Tags":"python,database,security,encryption","A_Id":5933351,"CreationDate":"2011-05-07T07:56:00.000","Title":"Storing encrypted files inside a database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have large text files upon which all kinds of operations need to be performed, mostly involving row by row validations.  The data are generally of a sales \/ transaction nature, and thus tend to contain a huge amount of redundant information across rows, such as customer names.  Iterating and manipulating this data has become such a common task that I'm writing a library in C that I hope to make available as a Python module.  \nIn one test, I found that out of 1.3 million column values, only ~300,000 were unique.  Memory overhead is a concern, as our Python based web application could be handling simultaneous requests for large data sets.  \nMy first attempt was to read in the file and insert each column value into a binary search tree.  If the value has never been seen before, memory is allocated to store the string, otherwise a pointer to the existing storage for that value is returned.  This works well for data sets of ~100,000 rows.  Much larger and everything grinds to a halt, and memory consumption skyrockets.  I assume the overhead of all those node pointers in the tree isn't helping, and using strcmp for the binary search becomes very painful.\nThis unsatisfactory performance leads me to believe I should invest in using a hash table instead.  This, however, raises another point -- I have no idea ahead of time how many records there are.  It could be 10, or ten million.  How do I strike the right balance of time \/ space to prevent resizing my hash table again and again?\nWhat are the best data structure candidates in a situation like this?\nThank you for your time.","AnswerCount":3,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":501,"Q_Id":5931151,"Users Score":1,"Answer":"Hash table resizing isn't a concern unless you have a requirement that each insert into the table should take the same amount of time. As long as you always expand the hash table size by a constant factor (e.g. always increasing the size by 50%), the computational cost of adding an extra element is amortized O(1). This means that n insertion operations (when n is large) will take an amount of time that is proportionate to n - however, the actual time per insertion may vary wildly (in practice, one of the insertions will be very slow while the others will be very fast, but the average of all operations is small). The reason for this is that when you insert an extra element that forces the table to expand from e.g. 1000000 to 1500000 elements, that insert will take a lot of time, but now you've bought yourself 500000 extremely fast future inserts before you need to resize again. In short, I'd definitely go for a hash table.","Q_Score":3,"Tags":"python,c,data-structures,file-io","A_Id":5931175,"CreationDate":"2011-05-08T23:41:00.000","Title":"BST or Hash Table?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"when I try to install python-mysql today, I got a number of compilation error or complaining \/Developer\/SDKs\/MacOSX10.4u.sdk not found, like the following:\n\nrunning build\nrunning build_py\ncopying MySQLdb\/release.py -> build\/lib.macosx-10.3-i386-2.6\/MySQLdb\n  running build_ext\nbuilding '_mysql' extension\nCompiling with an SDK that doesn't seem to exist: \/Developer\/SDKs\/MacOSX10.4u.sdk\nPlease check your Xcode installation\n\nHowever, I already installed latest xcode 4.0, which does include latest GCC and SDK.\nI tried to find out where the 10.4u.sdk is specified, but could not find it in the system environment, program source and setuptools source.\nI tried to export \n\nexport SDK=\/Developer\/SDKs\/MacOSX10.5.sdk\nexport SDKROOT=\/Developer\/SDKs\/MacOSX10.5.sdk\n\nbut still has no luck.\nso anyone has any idea where this is specified in Mac Snow Leopard pls?\nthx","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":358,"Q_Id":5935910,"Users Score":0,"Answer":"Check your environment for CFLAGS or LDFLAGS.  Both of these can include the -isysroot argument that influences the SDK selection.  The other place to start at is to look at the output of python2.6-config --cflags --ldflags since (I believe) that this influences the Makefile generation.  Make sure to run easy_install with --verbose and see if it yields any additional insight.","Q_Score":0,"Tags":"python,mysql,macos,osx-snow-leopard,compilation","A_Id":5936425,"CreationDate":"2011-05-09T10:58:00.000","Title":"mac snow leopard setuptools stick to MacOSX10.4u.sdk when trying to install python-mysql","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":0},{"Question":"The Facts:\n\nI am working on a NoteBook with Intel Core 2 Duo 2,26 GHz and 4 Gigabyte of Ram.\nIt has a Apache Server and a MySQL Server running.\nMy Server (I did lshw | less) shows a 64 Bit CPU with 2,65 GHz and 4 Gigabyte Ram, too. It has the XAMPP-Package running on it.\nThe Database structures (tables, indices, ...) are identical and so is the Python script I am running.\n\nThe Problem:\nWhile the script runs in approximately 30 seconds on my macbook it took the script 11 minutes on the server!\nWhat are the points you would check first for a bottleneck?\nThe Solution:\nThere were two indices missing on one of the machines. I added them and voil\u00e1: Everything was super! The `EXPLAIN' keyword of MySQL was worth a mint. =)","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":101,"Q_Id":5944433,"Users Score":2,"Answer":"What kind of server? If you're renting a  VPS or similar you're contending with other users for CPU time.\nWhat platform is running on both? Tell us more about your situation!","Q_Score":2,"Tags":"python,mysql,runtime","A_Id":5944478,"CreationDate":"2011-05-10T02:07:00.000","Title":"How do I find why a python scripts runs in significantly different running times on different machines?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"The Facts:\n\nI am working on a NoteBook with Intel Core 2 Duo 2,26 GHz and 4 Gigabyte of Ram.\nIt has a Apache Server and a MySQL Server running.\nMy Server (I did lshw | less) shows a 64 Bit CPU with 2,65 GHz and 4 Gigabyte Ram, too. It has the XAMPP-Package running on it.\nThe Database structures (tables, indices, ...) are identical and so is the Python script I am running.\n\nThe Problem:\nWhile the script runs in approximately 30 seconds on my macbook it took the script 11 minutes on the server!\nWhat are the points you would check first for a bottleneck?\nThe Solution:\nThere were two indices missing on one of the machines. I added them and voil\u00e1: Everything was super! The `EXPLAIN' keyword of MySQL was worth a mint. =)","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":101,"Q_Id":5944433,"Users Score":0,"Answer":"I would check that the databases in question are of similar scope. You say they're the same structure, but are they sized similarly? If your test case only has 100 entries when production has 100000000, that's one huge potential area for performance problems.","Q_Score":2,"Tags":"python,mysql,runtime","A_Id":5956131,"CreationDate":"2011-05-10T02:07:00.000","Title":"How do I find why a python scripts runs in significantly different running times on different machines?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"sorry for my English in advance. \nI am a beginner with Cassandra and his data model. I am trying to insert one million rows in a cassandra database in local on one node. Each row has 10 columns and I insert those only in one column family.\nWith one thread, that operation took around 3 min. But I would like do the same operation with 2 millions rows, and keeping a good time. Then I tried with 2 threads to insert 2 millions rows, expecting a similar result around 3-4min. bUT i gor a result like 7min...twice the first result. As I check on differents forums, multithreading is recommended to improve performance.\nThat is why I am asking that question : is it useful to use multithreading to insert data in local node (client and server are in the same computer), in only one column family?\nSome informations :\n - I use pycassa\n - I have separated commitlog repertory and data repertory on differents disks\n - I use batch insert for each thread\n - Consistency Level : ONE\n - Replicator factor : 1","AnswerCount":4,"Available Count":4,"Score":0.0,"is_accepted":false,"ViewCount":1686,"Q_Id":5950427,"Users Score":0,"Answer":"It's possible you're hitting the python GIL but more likely you're doing something wrong.\nFor instance, putting 2M rows in a single batch would be Doing It Wrong.","Q_Score":0,"Tags":"python,multithreading,insert,cassandra","A_Id":5950881,"CreationDate":"2011-05-10T13:02:00.000","Title":"Insert performance with Cassandra","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"sorry for my English in advance. \nI am a beginner with Cassandra and his data model. I am trying to insert one million rows in a cassandra database in local on one node. Each row has 10 columns and I insert those only in one column family.\nWith one thread, that operation took around 3 min. But I would like do the same operation with 2 millions rows, and keeping a good time. Then I tried with 2 threads to insert 2 millions rows, expecting a similar result around 3-4min. bUT i gor a result like 7min...twice the first result. As I check on differents forums, multithreading is recommended to improve performance.\nThat is why I am asking that question : is it useful to use multithreading to insert data in local node (client and server are in the same computer), in only one column family?\nSome informations :\n - I use pycassa\n - I have separated commitlog repertory and data repertory on differents disks\n - I use batch insert for each thread\n - Consistency Level : ONE\n - Replicator factor : 1","AnswerCount":4,"Available Count":4,"Score":0.0,"is_accepted":false,"ViewCount":1686,"Q_Id":5950427,"Users Score":0,"Answer":"Try running multiple clients in multiple processes, NOT threads.\nThen experiment with different insert sizes. \n1M inserts in 3 mins is about 5500 inserts\/sec, which is pretty good for a single local client. On a multi-core machine you should be able to get several times this amount provided that you use multiple clients, probably inserting small batches of rows, or individual rows.","Q_Score":0,"Tags":"python,multithreading,insert,cassandra","A_Id":5956519,"CreationDate":"2011-05-10T13:02:00.000","Title":"Insert performance with Cassandra","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"sorry for my English in advance. \nI am a beginner with Cassandra and his data model. I am trying to insert one million rows in a cassandra database in local on one node. Each row has 10 columns and I insert those only in one column family.\nWith one thread, that operation took around 3 min. But I would like do the same operation with 2 millions rows, and keeping a good time. Then I tried with 2 threads to insert 2 millions rows, expecting a similar result around 3-4min. bUT i gor a result like 7min...twice the first result. As I check on differents forums, multithreading is recommended to improve performance.\nThat is why I am asking that question : is it useful to use multithreading to insert data in local node (client and server are in the same computer), in only one column family?\nSome informations :\n - I use pycassa\n - I have separated commitlog repertory and data repertory on differents disks\n - I use batch insert for each thread\n - Consistency Level : ONE\n - Replicator factor : 1","AnswerCount":4,"Available Count":4,"Score":0.0,"is_accepted":false,"ViewCount":1686,"Q_Id":5950427,"Users Score":0,"Answer":"You might consider Redis.  Its single-node throughput is supposed to be faster.  It's different from Cassandra though, so whether or not it's an appropriate option would depend on your use case.","Q_Score":0,"Tags":"python,multithreading,insert,cassandra","A_Id":6078703,"CreationDate":"2011-05-10T13:02:00.000","Title":"Insert performance with Cassandra","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"sorry for my English in advance. \nI am a beginner with Cassandra and his data model. I am trying to insert one million rows in a cassandra database in local on one node. Each row has 10 columns and I insert those only in one column family.\nWith one thread, that operation took around 3 min. But I would like do the same operation with 2 millions rows, and keeping a good time. Then I tried with 2 threads to insert 2 millions rows, expecting a similar result around 3-4min. bUT i gor a result like 7min...twice the first result. As I check on differents forums, multithreading is recommended to improve performance.\nThat is why I am asking that question : is it useful to use multithreading to insert data in local node (client and server are in the same computer), in only one column family?\nSome informations :\n - I use pycassa\n - I have separated commitlog repertory and data repertory on differents disks\n - I use batch insert for each thread\n - Consistency Level : ONE\n - Replicator factor : 1","AnswerCount":4,"Available Count":4,"Score":0.0,"is_accepted":false,"ViewCount":1686,"Q_Id":5950427,"Users Score":0,"Answer":"The time taken doubled because you inserted twice as much data. Is it possible that you are I\/O bound?","Q_Score":0,"Tags":"python,multithreading,insert,cassandra","A_Id":8491215,"CreationDate":"2011-05-10T13:02:00.000","Title":"Insert performance with Cassandra","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm using this javascript library (http:\/\/valums.com\/ajax-upload\/) to upload file to a tornado web server, but I don't know how to get the file content. The javascript library is uploading using XHR, so I assume I have to read the raw post data to get the file content. But I don't know how to do it with Tornado. Their documentation doesn't help with this, as usual :(\nIn php they have something like this:\n$input = fopen(\"php:\/\/input\", \"r\");\nso what's the equivalence in tornado?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1836,"Q_Id":5983032,"Users Score":2,"Answer":"I got the answer.\nI need to use self.request.body to get the raw post data.\nI also need to pass in the correct _xsrf token, otherwise tornado will fire a 403 exception.\nSo that's about it.","Q_Score":3,"Tags":"python,file-upload,tornado,ajax-upload","A_Id":5989216,"CreationDate":"2011-05-12T19:00:00.000","Title":"asynchronous file upload with ajaxupload to a tornado web server","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"Is there a function in Python that checks if the returned value is None and if it is, allows you to set it to another value like the IFNULL function in MySQL?","AnswerCount":8,"Available Count":2,"Score":-0.049958375,"is_accepted":false,"ViewCount":35088,"Q_Id":5987371,"Users Score":-2,"Answer":"Since this question is now over 2 years old I guess this is more for future references :)\nWhat I like to do is max('', mightBeNoneVar) or max(0, mightBeNoneVar) (depending on the context).\nMore elaborate example:\nprint max('', col1).ljust(width1) + '   ==>   '+ max('', col2).ljust(width2)","Q_Score":15,"Tags":"python","A_Id":16633853,"CreationDate":"2011-05-13T04:54:00.000","Title":"Python equivalent for MySQL's IFNULL","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"Is there a function in Python that checks if the returned value is None and if it is, allows you to set it to another value like the IFNULL function in MySQL?","AnswerCount":8,"Available Count":2,"Score":0.024994793,"is_accepted":false,"ViewCount":35088,"Q_Id":5987371,"Users Score":1,"Answer":"nvl(v1,v2) will return v1 if not null otherwise it returns v2.\nnvl = lambda a,b: a or b","Q_Score":15,"Tags":"python","A_Id":50119942,"CreationDate":"2011-05-13T04:54:00.000","Title":"Python equivalent for MySQL's IFNULL","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have been running Davical on a CentOS 5 box for a while now with no problems.\nYesterday however, I installed Trac bug-tracker which eventually forced me to run a full update via Yum which updated a whole heap of packages.\nI cant seem to work out exactly what the issue is and time spent googling didn't seem to bring about much in the way of ideas.\nHas anyone had the same problem or could anyone indicate a way to better identify whats going on?\nMany Thanks!\nFull Error readout :\n\n[Wed May 11 17:52:53 2011] [error] davical: LOG: always: Query: QF: SQL error \"58P01\" - ERROR: could not load library \"\/usr\/lib\/pgsql\/plpgsql.so\": \/usr\/lib\/pgsql\/plpgsql.so: undefined symbol: PinPortal\"\n\nChecking to see if file exists\n[@shogun ~]# tree -a \/usr\/lib\/pgsql\/ | grep \"plpgsql\"\n|-- plpgsql.so\nVersion of pg installed\n[@shogun ~]# pg_config | grep \"VERSION\"\nVERSION = PostgreSQL 8.1.23\n[@shogun postgresql-8.3.8]# yum list installed | grep 'post'\npostgresql.i386                        8.1.23-1.el5_6.1                installed\npostgresql-devel.i386                  8.1.23-1.el5_6.1                installed\npostgresql-libs.i386                   8.1.23-1.el5_6.1                installed\npostgresql-python.i386                 8.1.23-1.el5_6.1                installed\npostgresql-server.i386                 8.1.23-1.el5_6.1                installed","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":5259,"Q_Id":5994297,"Users Score":8,"Answer":"I have had this problem before, although with 8.4 instead of 8.1, but the issue is the same, I believe.\nA recent minor upgrade of all supported maintenance branches of PostgreSQL introduced the function PinPortal in the server, and made PL\/pgSQL use it.  So if you use a plpgsql.so from the newer version with a server from the older version, you will get this error.  In your case, the change happened between 8.1.21 and 8.1.22.  And even if all your installed packages show the newer version, you need to restart the server to make sure you actually use the newer version.\nThe problem is, as soon as you install the newer PL\/pgSQL, it will get used by the next session that is started, but the newer server binary won't get used until you restart the server.  So if your upgrade process doesn't restart the server immediately, you will invariably get these errors as soon as something tries to use PL\/pgSQL.  If this actually turns out to be the problem, you might want to review why your server wasn't restarted.","Q_Score":6,"Tags":"python,postgresql,centos,trac","A_Id":5998204,"CreationDate":"2011-05-13T15:38:00.000","Title":"Could not load library \"\/usr\/lib\/pgsql\/plpgsql.so\" & undefined symbol: PinPortal","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"What is the recommonded way to interact between python and MySQL? Currently I am using MySQLdb and I heared from Oursql. But I asked myself, if there is a more appropriate way to manage this.","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":234,"Q_Id":6002147,"Users Score":0,"Answer":"I personally use pymysql, but have heard a lot of people use MySQLdb. Both are very similar in the way they behave, and could easily be interchangeable. Personally, (working as a python\/MySQL QA) I've yet to hear of \/ let alone work with OurSQL. \nWith that said, it honestly depends what you want to accomplish. Python has a lot of connectors, and a tons of bells and whistles to complete almost anything; (and) As such, it is important to note that it is important to always look at how popular the component is, as well as how frequently it gets updated.","Q_Score":3,"Tags":"python,mysql,interaction","A_Id":40519201,"CreationDate":"2011-05-14T13:32:00.000","Title":"Is there a recommended way for interaction between python and MySQL?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have setup an Apache server with mod_wsgi, python_sql, mysql and django.\nEverything works fine, except the fact that if I make some code changes, they do not reflect immidiately, though I thing that everything is compiled on the fly when it comes to python\/mod_wsgi.\nI have to shut down the server and come back again to see the changes.\nCan someone point me to how hot-deployment can be achieved with the above setup??\nThanks,\nNeeraj","AnswerCount":2,"Available Count":1,"Score":0.2913126125,"is_accepted":false,"ViewCount":768,"Q_Id":6006666,"Users Score":3,"Answer":"Just touching the wsgi file allways worked for me.","Q_Score":4,"Tags":"python,django,apache2,mod-wsgi,hotdeploy","A_Id":6007285,"CreationDate":"2011-05-15T05:26:00.000","Title":"Hot deployment using mod_wsgi,python and django on Apache","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I need to insert rows into PG one of the fields is date and time with time stamp, this is the time of incident, so I can not use --> current_timestamp function of Postgres at the time of insertion, so how can I then insert the time and date which I collected before into pg row in the same format as it would have been created by current_timestamp at that point in time.","AnswerCount":7,"Available Count":1,"Score":-1.0,"is_accepted":false,"ViewCount":190399,"Q_Id":6018214,"Users Score":-4,"Answer":"Just use \n\nnow()\n\nor \n\nCURRENT_TIMESTAMP\n\nI prefer the latter as I like not having additional parenthesis but thats just personal preference.","Q_Score":64,"Tags":"python,postgresql,datetime","A_Id":18624640,"CreationDate":"2011-05-16T13:34:00.000","Title":"How to insert current_timestamp into Postgres via python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm trying to run a python script using python 2.6.4. The hosting company has 2.4 installed so I compiled my own 2.6.4 on a similar server and then moved the files over into ~\/opt\/python. that part seems to be working fine.\nanyhow, when I run the script below, I am getting ImportError: No module named _sqlite3 and I'm not sure what to do to fix this.\nMost online threads mention that sqlite \/ sqlite3 is included in python 2.6 - so I'm not sure why this isn't working.\n\n-jailshell-3.2$ .\/pyDropboxValues.py \n\nTraceback (most recent call last):\n  File \".\/pyDropboxValues.py\", line 21, in \n    import sqlite3\n  File \"\/home\/myAccount\/opt\/lib\/python2.6\/sqlite3\/__init__.py\", line 24, in \n    from dbapi2 import *\n  File \"\/home\/myAccount\/opt\/lib\/python2.6\/sqlite3\/dbapi2.py\", line 27, in \n    from _sqlite3 import *\nImportError: No module named _sqlite3\n\nI think I have everything set up right as far as the directory structure.\n\n-jailshell-3.2$ find `pwd` -type d\n\n\/home\/myAccount\/opt\n\/home\/myAccount\/opt\/bin\n\/home\/myAccount\/opt\/include\n\/home\/myAccount\/opt\/include\/python2.6\n\/home\/myAccount\/opt\/lib\n\/home\/myAccount\/opt\/lib\/python2.6\n\/home\/myAccount\/opt\/lib\/python2.6\/distutils\n\/home\/myAccount\/opt\/lib\/python2.6\/distutils\/command\n\/home\/myAccount\/opt\/lib\/python2.6\/distutils\/tests\n\/home\/myAccount\/opt\/lib\/python2.6\/compiler\n\/home\/myAccount\/opt\/lib\/python2.6\/test\n\/home\/myAccount\/opt\/lib\/python2.6\/test\/decimaltestdata\n\/home\/myAccount\/opt\/lib\/python2.6\/config\n\/home\/myAccount\/opt\/lib\/python2.6\/json\n\/home\/myAccount\/opt\/lib\/python2.6\/json\/tests\n\/home\/myAccount\/opt\/lib\/python2.6\/email\n\/home\/myAccount\/opt\/lib\/python2.6\/email\/test\n\/home\/myAccount\/opt\/lib\/python2.6\/email\/test\/data\n\/home\/myAccount\/opt\/lib\/python2.6\/email\/mime\n\/home\/myAccount\/opt\/lib\/python2.6\/lib2to3\n\/home\/myAccount\/opt\/lib\/python2.6\/lib2to3\/pgen2\n\/home\/myAccount\/opt\/lib\/python2.6\/lib2to3\/fixes\n\/home\/myAccount\/opt\/lib\/python2.6\/lib2to3\/tests\n\/home\/myAccount\/opt\/lib\/python2.6\/xml\n\/home\/myAccount\/opt\/lib\/python2.6\/xml\/parsers\n\/home\/myAccount\/opt\/lib\/python2.6\/xml\/sax\n\/home\/myAccount\/opt\/lib\/python2.6\/xml\/etree\n\/home\/myAccount\/opt\/lib\/python2.6\/xml\/dom\n\/home\/myAccount\/opt\/lib\/python2.6\/site-packages\n\/home\/myAccount\/opt\/lib\/python2.6\/logging\n\/home\/myAccount\/opt\/lib\/python2.6\/lib-dynload\n\/home\/myAccount\/opt\/lib\/python2.6\/sqlite3\n\/home\/myAccount\/opt\/lib\/python2.6\/sqlite3\/test\n\/home\/myAccount\/opt\/lib\/python2.6\/encodings\n\/home\/myAccount\/opt\/lib\/python2.6\/wsgiref\n\/home\/myAccount\/opt\/lib\/python2.6\/multiprocessing\n\/home\/myAccount\/opt\/lib\/python2.6\/multiprocessing\/dummy\n\/home\/myAccount\/opt\/lib\/python2.6\/curses\n\/home\/myAccount\/opt\/lib\/python2.6\/bsddb\n\/home\/myAccount\/opt\/lib\/python2.6\/bsddb\/test\n\/home\/myAccount\/opt\/lib\/python2.6\/idlelib\n\/home\/myAccount\/opt\/lib\/python2.6\/idlelib\/Icons\n\/home\/myAccount\/opt\/lib\/python2.6\/tmp\n\/home\/myAccount\/opt\/lib\/python2.6\/lib-old\n\/home\/myAccount\/opt\/lib\/python2.6\/lib-tk\n\/home\/myAccount\/opt\/lib\/python2.6\/hotshot\n\/home\/myAccount\/opt\/lib\/python2.6\/plat-linux2\n\/home\/myAccount\/opt\/lib\/python2.6\/ctypes\n\/home\/myAccount\/opt\/lib\/python2.6\/ctypes\/test\n\/home\/myAccount\/opt\/lib\/python2.6\/ctypes\/macholib\n\/home\/myAccount\/opt\/share\n\/home\/myAccount\/opt\/share\/man\n\/home\/myAccount\/opt\/share\/man\/man1\n\n\nAnd finally the contents of the sqlite3 directory:\n\n-jailshell-3.2$ find `pwd`\n\n\/home\/myAccount\/opt\/lib\/python2.6\/sqlite3\n\/home\/myAccount\/opt\/lib\/python2.6\/sqlite3\/__init__.pyo\n\/home\/myAccount\/opt\/lib\/python2.6\/sqlite3\/dump.pyc\n\/home\/myAccount\/opt\/lib\/python2.6\/sqlite3\/__init__.pyc\n\/home\/myAccount\/opt\/lib\/python2.6\/sqlite3\/dbapi2.pyo\n\/home\/myAccount\/opt\/lib\/python2.6\/sqlite3\/dbapi2.pyc\n\/home\/myAccount\/opt\/lib\/python2.6\/sqlite3\/dbapi2.py\n\/home\/myAccount\/opt\/lib\/python2.6\/sqlite3\/dump.pyo\n\/home\/myAccount\/opt\/lib\/python2.6\/sqlite3\/__init__.py\n\/home\/myAccount\/opt\/lib\/python2.6\/sqlite3\/dump.py\n\n\nI feel like I need to add something into the sqlite3 directory - maybe sqlite3.so? But I don't know where to get that.\nWhat am I doing wrong here? Please remember that I'm using a shared host so that means installing \/ compiling on another server and then copying the files over. Thanks! :)\nUpdate\nJust wanted to confirm that the answer from @samplebias did work out very well. I needed to have the dev package installed on the machine I was compiling from to get it to add in sqlite3.so and related files. Also found the link in the answer very helpful. Thanks @samplebias !","AnswerCount":4,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1962,"Q_Id":6026485,"Users Score":0,"Answer":"In general, the first thing to do is to ask your host. I seems a bit odd that SQLite is not installed (or installed properly). So they'll likely fix it quite fast if you ask them.","Q_Score":2,"Tags":"python,linux,unix,sqlite","A_Id":6026507,"CreationDate":"2011-05-17T05:10:00.000","Title":"How can I get sqlite working on a shared hosting server?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I need to have some references in my table and a bunch of \"deferrable initially deferred\" modifiers, but I can't find a way to make this work in the default generated Django code.\nIs it safe to create the table manually and still use Django models?","AnswerCount":3,"Available Count":1,"Score":0.1325487884,"is_accepted":false,"ViewCount":112,"Q_Id":6053426,"Users Score":2,"Answer":"Yes. \nI don't see why not, but that would be most unconventional and breaking convention usually leads to complications down the track.\nDescribe the problem you think it will solve and perhaps someone can offer a more conventional solution.","Q_Score":2,"Tags":"python,sql,django,postgresql","A_Id":6053509,"CreationDate":"2011-05-19T03:30:00.000","Title":"Is it safe to write your own table creation SQL for use with Django, when the generated tables are not enough?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am creating a software with user + password. After autentification, the user can access some semi public services, but also encrypt some files that only the user can access.\nThe user must be stored as is, without modification, if possible. After auth, the user and the password are kept in memory as long as the software is running (i don't know if that's okay either).\nThe question is how should i store this user + password combination in a potentially unsecure database?\nI don't really understand what should i expose.\nLet's say I create an enhanced key like this:\n\nsalt = random 32 characters string (is it okay?)\nkey = hash(usr password + salt)\nfor 1 to 65000 do\n  key = hash(key + usr password + salt)\n\nShould I store the [plaintext user], [the enhanced key] and [the salt] in the database ?\nAlso, what should I use to encrypt (with AES or Blowfish) some files using a new password everytime ?\nShould I generate a new salt and create a new enhanced key using (the password stored in memory of the program + the salt) ?\nAnd in this case, if i store the encrypted file in the database, i should probably only store the salt.\nThe database is the same as where i store the user + password combination.\nThe file can only be decrypted if someone can generate the key, but he doesn't know the password. Right ?\nI use Python with PyCrypto, but it's not really important, a general example is just fine.\nI have read a few similar questions, but they are not very explicit.\nThank you very very much!","AnswerCount":2,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":3307,"Q_Id":6058019,"Users Score":2,"Answer":"If you use a different salt for each user, you must store it somewhere (ideally in a different place). If you use the same salt for every user, you can hardcode it in your app, but it can be considered less secure. \nIf you don't keep the salt, you will not be able to match a given password against the one in your database.\nThe aim of the salt is to make bruteforce or dictionnary attacks a lot harder. That is why it is more secure if store separately, to avoid someone having both hash passwords and corresponding salts.","Q_Score":10,"Tags":"python,security,passwords","A_Id":6058858,"CreationDate":"2011-05-19T11:37:00.000","Title":"Storing user and password in a database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"The sqlite docs says that using the pragma default_cache_size is deprecated. I looked, but I couldn't see any explanation for why. Is there a reason for this? I'm working on an embedded python program, and we open and close connections a lot. Is the only alternative to use the pragma cache_size on every database connection?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":890,"Q_Id":6062999,"Users Score":2,"Answer":"As Firefox is massively using SQLite I wouldn't be surprised if this request came from their camp to prevent any kind of 3rd party interference (e.g. \"trashing\" with large\/small\/invalid\/obscure values) by this kind of pragma propagating through all database connections\nHence, my strong belief is that there is no alternative and that you really need to set cache_size for each database connection","Q_Score":5,"Tags":"python,sqlite","A_Id":6175144,"CreationDate":"2011-05-19T18:10:00.000","Title":"Alternative to deprecated sqlite pragma \"default_cache_size\"","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a website where people post comments, pictures, and other content. I want to add a feature that users can like\/unlike these items.\nI use a database to store all the content.\nThere are a few approaches I am looking at:\nMethod 1:\n\nAdd a 'like_count' column to the table, and increment it whenever someone likes an item\nAdd a 'user_likes' table to keep a track that everything the user has liked.\n\nPros: Simple to implement, minimal queries required.\nCons: The item needs to be refreshed with each change in like count. I have a whole list of items cached, which will break.\nMethod 2:\n\nCreate a new table 'like_summary' and store the total likes of each item in that table\nAdd a 'user_likes' table to keep a track that everything the user has liked.\nCache the like_summary data in memcache, and only flush it if the value changes\n\nPros: Less load on the main items table, it can be cached without worrying.\nCons: Too many hits on memcache (a page shows 20 items, which needs to be loaded from memcache), might be slow\nAny suggestions?","AnswerCount":3,"Available Count":2,"Score":0.0665680765,"is_accepted":false,"ViewCount":104,"Q_Id":6067919,"Users Score":1,"Answer":"You will actually only need the user_likes table. The like_count is calculated from that table. You will only need to store that if you need to gain performance, but since you're using memcached, It may be a good idea to not store the aggregated value in the database, but store it only in memcached.","Q_Score":0,"Tags":"python,architecture","A_Id":6067968,"CreationDate":"2011-05-20T05:46:00.000","Title":"What would be a good strategy to implement functionality similar to facebook 'likes'?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a website where people post comments, pictures, and other content. I want to add a feature that users can like\/unlike these items.\nI use a database to store all the content.\nThere are a few approaches I am looking at:\nMethod 1:\n\nAdd a 'like_count' column to the table, and increment it whenever someone likes an item\nAdd a 'user_likes' table to keep a track that everything the user has liked.\n\nPros: Simple to implement, minimal queries required.\nCons: The item needs to be refreshed with each change in like count. I have a whole list of items cached, which will break.\nMethod 2:\n\nCreate a new table 'like_summary' and store the total likes of each item in that table\nAdd a 'user_likes' table to keep a track that everything the user has liked.\nCache the like_summary data in memcache, and only flush it if the value changes\n\nPros: Less load on the main items table, it can be cached without worrying.\nCons: Too many hits on memcache (a page shows 20 items, which needs to be loaded from memcache), might be slow\nAny suggestions?","AnswerCount":3,"Available Count":2,"Score":0.0665680765,"is_accepted":false,"ViewCount":104,"Q_Id":6067919,"Users Score":1,"Answer":"One relation table that does a many-to-many mapping between user and item should do the trick.","Q_Score":0,"Tags":"python,architecture","A_Id":6067953,"CreationDate":"2011-05-20T05:46:00.000","Title":"What would be a good strategy to implement functionality similar to facebook 'likes'?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm very new to Python and I have Python 3.2 installed on a Win 7-32 workstation. Trying to connect to MSSQLServer 2005 Server using adodbapi-2.4.2.2, the latest update to that package.\nThe code\/connection string looks like this:\nconn = adodbapi.connect('Provider=SQLNCLI.1;Integrated Security=SSPI;Persist Security Info=False;Initial Catalog=XXX;Data Source=123.456.789');\nFrom adodbapi I continually get the error (this is entire error message from Wing IDE shell):\nTraceback (most recent call last):\n  File \"D:\\Program Files\\Wing IDE 4.0\\src\\debug\\tserver_sandbox.py\", line 2, in \n    if name == 'main':\n  File \"D:\\Python32\\Lib\\site-packages\\adodbapi\\adodbapi.py\", line 298, in connect\n    raise InterfaceError #Probably COM Error\nadodbapi.adodbapi.InterfaceError:\nI can trace through the code and see the exception as it happens.\nI also tried using conn strings with OLEDB provider and integrated Windows security, with same results. \nAll of these connection strings work fine from a UDL file on my workstation, and from SSMS, but fail with the same error in adodbapi.\nHow do I fix this?","AnswerCount":3,"Available Count":1,"Score":0.1325487884,"is_accepted":false,"ViewCount":8199,"Q_Id":6086341,"Users Score":2,"Answer":"I had the same problem, and I tracked it down to a failure to load win32com.pyd, because of some system DLLs that was not in the \"dll load path\", such as msvcp100.dll\nI solved the problem by copying a lot of these dll's (probably too many) into C:\\WinPython-64bit-3.3.3.2\\python-3.3.3.amd64\\Lib\\site-packages\\win32","Q_Score":6,"Tags":"python,database,sql-server-2005,adodbapi","A_Id":21480454,"CreationDate":"2011-05-22T06:03:00.000","Title":"Connecting to SQLServer 2005 with adodbapi","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"My company has decided to implement a datamart using [Greenplum] and I have the task of figuring out how to go on about it. A ballpark figure of the amount of data to be transferred from the existing [DB2] DB to the Greenplum DB is about 2 TB.\nI would like to know :\n1) Is the Greenplum DB the same as vanilla [PostgresSQL]? (I've worked on Postgres AS 8.3)\n2) Are there any (free) tools available for this task (extract and import)\n3) I have some knowledge of Python. Is it feasible, even easy to do this in a resonable amount of time?\nI have no idea how to do this. Any advice, tips and suggestions will be hugely welcome.","AnswerCount":4,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":2294,"Q_Id":6110384,"Users Score":0,"Answer":"Many of Greenplum's utilities are written in python and the current DBMS distribution comes with python 2.6.2 installed, including the pygresql module which you can use to work inside the GPDB.\nFor data transfer into greenplum, I've written python scripts that connect to the source (Oracle) DB using cx_Oracle and then dumping that output either to flat files or named pipes.  gpfdist can read from either sort of source and load the data into the system.","Q_Score":0,"Tags":"python,postgresql,db2,datamart,greenplum","A_Id":7550497,"CreationDate":"2011-05-24T12:28:00.000","Title":"Transferring data from a DB2 DB to a greenplum DB","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"My company has decided to implement a datamart using [Greenplum] and I have the task of figuring out how to go on about it. A ballpark figure of the amount of data to be transferred from the existing [DB2] DB to the Greenplum DB is about 2 TB.\nI would like to know :\n1) Is the Greenplum DB the same as vanilla [PostgresSQL]? (I've worked on Postgres AS 8.3)\n2) Are there any (free) tools available for this task (extract and import)\n3) I have some knowledge of Python. Is it feasible, even easy to do this in a resonable amount of time?\nI have no idea how to do this. Any advice, tips and suggestions will be hugely welcome.","AnswerCount":4,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":2294,"Q_Id":6110384,"Users Score":0,"Answer":"Generally, it is really slow if you use SQL insert or merge to import big bulk data.\nThe recommended way is to use the external tables you define to use file-based, web-based or gpfdist protocol hosted files.\nAnd also greenplum has a utility named gpload, which can be used to define your transferring jobs, like source, output, mode(inert, update or merge).","Q_Score":0,"Tags":"python,postgresql,db2,datamart,greenplum","A_Id":23668974,"CreationDate":"2011-05-24T12:28:00.000","Title":"Transferring data from a DB2 DB to a greenplum DB","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a lot of objects which form a network by keeping references to other objects. All objects (nodes) have a dict which is their properties.\nNow I'm looking for a fast way to store these objects (in a file?) and reload all of them into memory later (I don't need random access). The data is about 300MB in memory which takes 40s to load from my SQL format, but I now want to cache it to have faster access.\nWhich method would you suggest?\n(my pickle attempt failed due to recursion errors despite trying to mess around with getstate :( maybe there is something fast anyway? :))","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":252,"Q_Id":6128458,"Users Score":0,"Answer":"Perhaps you could set up some layer of indirection where the objects are actually held within, say, another dictionary, and an object referencing another object will store the key of the object being referenced and then access the object through the dictionary. If the object for the stored key is not in the dictionary, it will be loaded into the dictionary from your SQL database, and when it doesn't seem to be needed anymore, the object can be removed from the dictionary\/memory (possibly with an update to its state in the database before the version in memory is removed).\nThis way you don't have to load all the data from your database at once, and can keep a number of the objects cached in memory for quicker access to those. The downside would be the additional overhead required for each access to the main dict.","Q_Score":2,"Tags":"python,persistent-storage","A_Id":6130718,"CreationDate":"2011-05-25T17:31:00.000","Title":"Store and load a large number linked objects in Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a written a very small web-based survey using cgi with python(This is my first web app. ).The questions are extracted from a MySQL database table and the results are supposed to be saved in the same database. I have created the database along with its table locally. My app works fine on my local computer(localhost). To create db,table and other transaction with the MySQL i had to do import MySQLdb in  my code.\nNow I want to upload everything on my personal hosting. As far as I know my hosting supports Python,CGI and has MySQL database. And I know that I have to change some parameters in the connection string in my code, so I can connect to the database, but I have two problems:\n\nI remember that I installed MySQLdb as an extra to my Python, and in my code i am using it, how would I know that my hosting's python interpretor has this installed, or do I even need it, do I have to use another library?\nHow do I upload my database onto my hosting?\nThanks","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":513,"Q_Id":6139777,"Users Score":0,"Answer":"You can write a simple script like\nimport MySQLdb and catch any errors\nto see if the required package is\ninstalled. If this fails you can ask\nthe hosting provider to install your\npackage, typically via a ticket\nThe hosting providers typically also provide URL's to connect to the MySQL tables they provision for you, and some tools like phpmyadmin to load database dumps into the hosted MySQL instance","Q_Score":0,"Tags":"python,mysql,database-connection,cpanel","A_Id":6139936,"CreationDate":"2011-05-26T13:59:00.000","Title":"Uploading a mysql database to a webserver supporting python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm building a real-time service so my real-time database need to storage in memcached before fetch to DB (Avoid to read\/write mysql db too much). I want to fetch data to mysql DB when some events occur , etc : before data expire or have least-recently-used (LRU) data. What is solution for my problem ? My system used memcached , mysql ,django and python-memcache \nThank","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":329,"Q_Id":6143748,"Users Score":1,"Answer":"Memcached is not a persistent store, so if you need your data to be durable at all then you will need to store them in a persistent store immediately.\nSo you need to put them somewhere - possibly a MySQL table - as soon as the data arrive, and make sure they are fsync'd to disc. Storing them in memcached as well only speeds up access, so it is a nice to have.\nMemcached can discard any objects at any time for any reason, not just when they expire.","Q_Score":1,"Tags":"python,mysql,django,memcached","A_Id":6146042,"CreationDate":"2011-05-26T19:06:00.000","Title":"Can auto transfer data from memcached to mysql DB?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Can someone please point me in the right direction of how I can connect to MS SQL Server with Python? What I want to do is read a text file, extract some values and then insert the values from the text file into a table in my Sql Server database. I am using Python 3.1.3, and it seems some of the modules I have come across in research online are not included in the library. Am I missing something? Is there a good 3rd party module I should know about. Any help would be greatly appreciated.I am using Windows. thanks","AnswerCount":3,"Available Count":1,"Score":0.0665680765,"is_accepted":false,"ViewCount":8530,"Q_Id":6154069,"Users Score":1,"Answer":"I found a module called CEODBC that I was able to use with Python 3 after doing some research. It looks like they will also be releasing a Python3 compatible version of PYODBC soon. Thanks for all your help.","Q_Score":3,"Tags":"python,sql,python-3.x,database-connection,python-module","A_Id":6193973,"CreationDate":"2011-05-27T14:59:00.000","Title":"Connecting to Sql Server with Python 3 in Windows","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have to write up a python program that communicates with a My SQL database to write in data... I have done the code however it does not enter all the data as it says there are duplicates... is there a way to just inclue them?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":38,"Q_Id":6162827,"Users Score":0,"Answer":"You should provide more information like you SQL and database schema. It sounds like you are trying to insert items with the same primary key. If you remove the primary key you should be able to insert the data, or change the insert statement to not insert the field which is the primary key.","Q_Score":0,"Tags":"python,sql","A_Id":6162872,"CreationDate":"2011-05-28T16:14:00.000","Title":"Is there a way to write into python code a command to include duplicate entries into a My SQL database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am planning to develop a web-based application which could crawl wikipedia for finding relations and store it in a database. By relations, I mean searching for a name say,'Bill Gates' and find his page, download it and pull out the various information from the page and store it in a database. Information may include his date of birth, his company and a few other things. But I need to know if there is any way to find these unique data from the page, so that I could store them in a database. Any specific books or algorithms would be greatly appreciated. Also mentioning of good opensource libraries would be helpful. \nThank You","AnswerCount":3,"Available Count":1,"Score":0.1325487884,"is_accepted":false,"ViewCount":3092,"Q_Id":6171764,"Users Score":2,"Answer":"You mention Python and Open Source, so I would investigate the NLTK (Natural Language Toolkit). Text mining and natural language processing is one of those things that you can do a lot with a dumb algorithm (eg. Pattern matching), but if you want to go a step further and do something more sophisticated - ie. Trying to extract information that is stored in a flexible manner or trying to find information that might be interesting but is not known a priori, then natural language processing should be investigated.\nNLTK is intended for teaching, so it is a toolkit. This approach suits Python very well. There are a couple of books for it as well. The O'Reilly book is also published online with an open license. See NLTK.org","Q_Score":2,"Tags":"python,pattern-matching,data-mining,wikipedia,text-mining","A_Id":6171789,"CreationDate":"2011-05-30T02:24:00.000","Title":"Mining Wikipedia for mapping relations for text mining","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"The csv file was created correctly but the name and address fields contain every piece of punctuation there is available. So when you try to import into mysql you get parsing errors. For example the name field could look like this, \"john \"\",\" doe\". I have no control over the data I receive so I'm unable to stop people from inputting garbage data. From the example above you can see that if you consider the outside quotes to be the enclosing quotes then it is right but of course mysql, excel, libreoffice, and etc see a whole new field. Is there a way to fix this problem? Some fields I found even have a backslash before the last enclosing quote. I'm at a loss as I have 17 million records to import.\nI have windows os and linux so whatever solution you can think of please let me know.","AnswerCount":6,"Available Count":5,"Score":1.0,"is_accepted":false,"ViewCount":3332,"Q_Id":6172123,"Users Score":7,"Answer":"This may not be a usable answer but someone needs to say it. You shouldn't have to do this. CSV is a file format with an expected data encoding. If someone is supplying you a CSV file then it should be delimited and escaped properly, otherwise its a corrupted file and you should reject it. Make the supplier re-export the file properly from whatever data store it was exported from.\nIf you asked someone to send you JPG and they send what was a proper JPG file with every 5th byte omitted or junk bytes inserted you wouldnt accept that and say \"oh, ill reconstruct it for you\".","Q_Score":2,"Tags":"php,python,mysql,csv","A_Id":6172230,"CreationDate":"2011-05-30T03:54:00.000","Title":"What is an easy way to clean an unparsable csv file","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"The csv file was created correctly but the name and address fields contain every piece of punctuation there is available. So when you try to import into mysql you get parsing errors. For example the name field could look like this, \"john \"\",\" doe\". I have no control over the data I receive so I'm unable to stop people from inputting garbage data. From the example above you can see that if you consider the outside quotes to be the enclosing quotes then it is right but of course mysql, excel, libreoffice, and etc see a whole new field. Is there a way to fix this problem? Some fields I found even have a backslash before the last enclosing quote. I'm at a loss as I have 17 million records to import.\nI have windows os and linux so whatever solution you can think of please let me know.","AnswerCount":6,"Available Count":5,"Score":0.0,"is_accepted":false,"ViewCount":3332,"Q_Id":6172123,"Users Score":0,"Answer":"First of all - find all kinds of mistake. And then just replace them with empty strings. Just do it! If you need this corrupted data - only you can recover it.","Q_Score":2,"Tags":"php,python,mysql,csv","A_Id":6172324,"CreationDate":"2011-05-30T03:54:00.000","Title":"What is an easy way to clean an unparsable csv file","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"The csv file was created correctly but the name and address fields contain every piece of punctuation there is available. So when you try to import into mysql you get parsing errors. For example the name field could look like this, \"john \"\",\" doe\". I have no control over the data I receive so I'm unable to stop people from inputting garbage data. From the example above you can see that if you consider the outside quotes to be the enclosing quotes then it is right but of course mysql, excel, libreoffice, and etc see a whole new field. Is there a way to fix this problem? Some fields I found even have a backslash before the last enclosing quote. I'm at a loss as I have 17 million records to import.\nI have windows os and linux so whatever solution you can think of please let me know.","AnswerCount":6,"Available Count":5,"Score":0.0,"is_accepted":false,"ViewCount":3332,"Q_Id":6172123,"Users Score":0,"Answer":"MySQL import has many parameters including escape characters. Given the example, I think the quotes are escaped by putting a quote in the front. So an import with esaped by '\"' would work.","Q_Score":2,"Tags":"php,python,mysql,csv","A_Id":6172154,"CreationDate":"2011-05-30T03:54:00.000","Title":"What is an easy way to clean an unparsable csv file","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"The csv file was created correctly but the name and address fields contain every piece of punctuation there is available. So when you try to import into mysql you get parsing errors. For example the name field could look like this, \"john \"\",\" doe\". I have no control over the data I receive so I'm unable to stop people from inputting garbage data. From the example above you can see that if you consider the outside quotes to be the enclosing quotes then it is right but of course mysql, excel, libreoffice, and etc see a whole new field. Is there a way to fix this problem? Some fields I found even have a backslash before the last enclosing quote. I'm at a loss as I have 17 million records to import.\nI have windows os and linux so whatever solution you can think of please let me know.","AnswerCount":6,"Available Count":5,"Score":0.0,"is_accepted":false,"ViewCount":3332,"Q_Id":6172123,"Users Score":0,"Answer":"That's a really tough issue.  I don't know of any real way to solve it, but maybe you could try splitting on \",\", cleaning up the items in the resulting array (unicorns :) ) and then re-joining the row?","Q_Score":2,"Tags":"php,python,mysql,csv","A_Id":6172145,"CreationDate":"2011-05-30T03:54:00.000","Title":"What is an easy way to clean an unparsable csv file","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"The csv file was created correctly but the name and address fields contain every piece of punctuation there is available. So when you try to import into mysql you get parsing errors. For example the name field could look like this, \"john \"\",\" doe\". I have no control over the data I receive so I'm unable to stop people from inputting garbage data. From the example above you can see that if you consider the outside quotes to be the enclosing quotes then it is right but of course mysql, excel, libreoffice, and etc see a whole new field. Is there a way to fix this problem? Some fields I found even have a backslash before the last enclosing quote. I'm at a loss as I have 17 million records to import.\nI have windows os and linux so whatever solution you can think of please let me know.","AnswerCount":6,"Available Count":5,"Score":0.0333209931,"is_accepted":false,"ViewCount":3332,"Q_Id":6172123,"Users Score":1,"Answer":"You don't say if you have control over the creation of the CSV file. I am assuming you do, as if not, the CVS file is corrupt and cannot be recovered without human intervention, or some very clever algorithms to \"guess\" the correct delimiters vs the user entered ones.\nConvert user entered tabs (assuming there are some) to spaces and then export the data using TABS separator.\nIf the above is not possible, you need to implement an ESC sequence to ensure that user entered data is not treated as a delimiter.","Q_Score":2,"Tags":"php,python,mysql,csv","A_Id":6172224,"CreationDate":"2011-05-30T03:54:00.000","Title":"What is an easy way to clean an unparsable csv file","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm writing the server for a Javascript app that has a syncing feature. Files and directories being created and modified by the client need to be synced to the server (the same changes made on the client need to be made on the server, including deletes).\nSince every file is on the server, I'm debating the need for a MySQL database entry corresponding to each file. The following information needs to be kept on each file\/directory for every user:\n\nWhether it was deleted or not (since deletes need to be synced to other clients)\nThe timestamp of when every file was last modified (so I know whether the file needs updating by the client or not)\n\nI could keep both of those pieces of information in files (e.g. .deleted file and .modified file in every user's directory containing file paths + timestamps in the latter) or in the database.\nHowever, I also have to fit under an 80mb memory constraint. Between file storage and \ndatabase storage, which would be more memory-efficient for this purpose?\nEdit: Files have to be stored on the filesystem (not in a database), and users have a quota for the storage space they can use.","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":216,"Q_Id":6180732,"Users Score":0,"Answer":"In my opinion, the only real way to be sure is to build a test system and compare the space requirements. It shouldn't take that long to generate some random data programatically. One might think the file system would be more efficient, but databases can and might compress the data or deduplicate it, or whatever. Don't forget that a database would also make it easier to implement new features, perhaps access control.","Q_Score":1,"Tags":"python,django,memory","A_Id":6181167,"CreationDate":"2011-05-30T21:04:00.000","Title":"Memory usage of file versus database for simple data storage","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I need a job scheduler (a library) that queries a db every 5 minutes and, based on time, triggers events which have expired and rerun on failure.\nIt should be in Python or PHP.\nI researched and came up with Advanced Python Scheduler but it is not appropriate because it only schedules the jobs in its job store. Instead, I want that it takes jobs from a database.\nI also found Taskforest, which exactly fits my needs except it is a text-file based scheduler meaning the jobs have to be added to the text-file either through the scheduler or manually, which I don't want to do.  \nCould anyone suggest me something useful?","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":710,"Q_Id":6184491,"Users Score":1,"Answer":"Here's a possible solution\n- a script, either in php or python performing your database tasks\n- a scheduler : Cron for linux, or the windows task scheduler ; where you set the frequency of your jobs.\nI'm using this solution for multiple projects.\nVery easy to set up.","Q_Score":0,"Tags":"php,python,database","A_Id":6184556,"CreationDate":"2011-05-31T07:50:00.000","Title":"Database Based Job scheduler","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"When accessing a MySQL database on low level using python, I use the MySQLdb module.\nI create a connection instance, then a cursor instance then I pass it to every function, that needs the cursor.\nSometimes I have many nested function calls, all desiring the mysql_cursor. Would it hurt to initialise the connection as global variable, so I can save me a parameter for each function, that needs the cursor?\nI can deliver an example, if my explanation was insufficient...","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":301,"Q_Id":6190982,"Users Score":1,"Answer":"I think that database cursors are scarce resources, so passing them around can limit your scalability and cause management issues (e.g. which method is responsible for closing the connection)?\nI'd recommend pooling connections and keeping them open for the shortest time possible.  Check out the connection, perform the database operation, map any results to objects or data structures, and close the connection.  Pass the object or data structure with results around rather than passing the cursor itself.  The cursor scope should be narrow.","Q_Score":2,"Tags":"python,connection,global-variables","A_Id":6191102,"CreationDate":"2011-05-31T17:03:00.000","Title":"What is the best way to handle connections (e.g. to mysql server using MySQLdb) in python, needed by multiple nested functions?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am trying to push user account data from an Active Directory to our MySQL-Server. This works flawlessly but somehow the strings end up showing an encoded version of umlauts and other special characters.\nThe Active Directory returns a string using this sample format: M\\xc3\\xbcller\nThis actually is the UTF-8 encoding for M\u00fcller, but I want to write M\u00fcller to my database not M\\xc3\\xbcller.\nI tried converting the string with this line, but it results in the same string in the database:\ntempEntry[1] = tempEntry[1].decode(\"utf-8\")\nIf I run print \"M\\xc3\\xbcller\".decode(\"utf-8\") in the python console the output is correct.\nIs there any way to insert this string the right way? I need this specific format for a web developer who wants to have this exact format, I don't know why he is not able to convert the string using PHP directly.\nAdditional info: I am using MySQLdb; The table and column encoding is utf8_general_ci","AnswerCount":8,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":77413,"Q_Id":6202726,"Users Score":0,"Answer":"and db.set_character_set('utf8'), imply that \nuse_unicode=True ?","Q_Score":37,"Tags":"python,unicode,utf-8","A_Id":7720395,"CreationDate":"2011-06-01T14:23:00.000","Title":"Writing UTF-8 String to MySQL with Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'd like to be able to include python code snippets in Excel (ideally, in a nice format -- all colors\/formats should be kept the same).\nWhat would be the best way to go about it?\nEDIT: I just want to store python code in an Excel spreadsheet for an easy overview -- I am not going to run it -- just want it to be nicely visible\/formatted as part of an Excel worksheet.","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":486,"Q_Id":6216278,"Users Score":1,"Answer":"While Excel itself doesnot support other scripting Langauges than VBA, the open source OpenOffice and LibreOffice packages - which include a spreadsheet - can be scriptable with Python. Still, they won't allow Python code to be pasted on teh cells out of the box - but it is possible to write Python code which can act on the spredsheet contents (and do all the other things Python can do).","Q_Score":2,"Tags":"python,excel","A_Id":6220700,"CreationDate":"2011-06-02T14:58:00.000","Title":"Include Python Code In Excel?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"What would be the best way of storing a python list of numbers (such as [4, 7, 10, 39, 91]) to a database? I am using the Pyramid framework with SQLAlchemy to communicate to a database.\nThanks!","AnswerCount":4,"Available Count":3,"Score":1.2,"is_accepted":true,"ViewCount":15473,"Q_Id":6222381,"Users Score":8,"Answer":"Well conceptually you can store a list as a bunch of rows in a table using a one-to-many relation, or you can focus on how to store a list in a particular database backend. For example postgres can store an array in a particular cell using the sqlalchemy.dialects.postgres.ARRAY data type which can serialize a python array into a postgres array column.","Q_Score":6,"Tags":"python,database,sqlalchemy,pyramid","A_Id":6224703,"CreationDate":"2011-06-03T02:22:00.000","Title":"The best way to store a python list to a database?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"What would be the best way of storing a python list of numbers (such as [4, 7, 10, 39, 91]) to a database? I am using the Pyramid framework with SQLAlchemy to communicate to a database.\nThanks!","AnswerCount":4,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":15473,"Q_Id":6222381,"Users Score":0,"Answer":"sqlalchemy.types.PickleType can store list","Q_Score":6,"Tags":"python,database,sqlalchemy,pyramid","A_Id":40277177,"CreationDate":"2011-06-03T02:22:00.000","Title":"The best way to store a python list to a database?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"What would be the best way of storing a python list of numbers (such as [4, 7, 10, 39, 91]) to a database? I am using the Pyramid framework with SQLAlchemy to communicate to a database.\nThanks!","AnswerCount":4,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":15473,"Q_Id":6222381,"Users Score":0,"Answer":"Use string(Varchar).\nFrom Zen of Python: \"Simple is better than complex.\"","Q_Score":6,"Tags":"python,database,sqlalchemy,pyramid","A_Id":6224600,"CreationDate":"2011-06-03T02:22:00.000","Title":"The best way to store a python list to a database?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm writing a small Python CGI script that captures the User-Agent, parses the OS, browser name and version, maps it to a database, and returns a device grade (integer).  Since this is only one table, it's a pretty simple operation, but I will likely have substantial traffic (10,000+ hits a day, potentially scaling much higher in the near and far future).\nWhich noSQL database would you recommend for this sort of application?  I would also like to build an admin interface which allows for manual input and is searchable.  I'm fairly new to Python and completely new to noSQL, and I'm having trouble finding any good info or libraries. Any suggestions?","AnswerCount":3,"Available Count":1,"Score":0.1325487884,"is_accepted":false,"ViewCount":776,"Q_Id":6230793,"Users Score":2,"Answer":"It depends on your use-case. Are you planning on caching the records temporarily or do you want the records to persist? If the former, Redis would be the best choice because of its speed. If the latter, it would be better to choose either CouchDB or MongoDB because they can handle large datasets.","Q_Score":2,"Tags":"python,nosql","A_Id":6231573,"CreationDate":"2011-06-03T17:53:00.000","Title":"Recommendations for a noSQL database for use with Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"MongoDB performs really well compared to our hacking of MySQL in de-normalized way. After database migration, I realized that we might need some server-side procedures to invoke after\/before database manipulation. Some sorta 3-tier architecture. I am just wondering the possible and easy way to prototype it. Are there any light server-side hooks for mongodb, just like server-side hooks for svn, git? \nex, post-commit, pre-commit, ...","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":1855,"Q_Id":6273573,"Users Score":0,"Answer":"FWIW, one of the messages in the web UI seems to imply that some hooks do exist (\"adding sharding hook to enable versioning and authentication to remote servers\"), but they might be only avilable within the compiled binaries, not to clients.","Q_Score":2,"Tags":"python,mongodb,hook,server-side,3-tier","A_Id":19877756,"CreationDate":"2011-06-08T02:26:00.000","Title":"What is suggested way to have server-side hooks over mongodb?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"MongoDB performs really well compared to our hacking of MySQL in de-normalized way. After database migration, I realized that we might need some server-side procedures to invoke after\/before database manipulation. Some sorta 3-tier architecture. I am just wondering the possible and easy way to prototype it. Are there any light server-side hooks for mongodb, just like server-side hooks for svn, git? \nex, post-commit, pre-commit, ...","AnswerCount":2,"Available Count":2,"Score":0.1973753202,"is_accepted":false,"ViewCount":1855,"Q_Id":6273573,"Users Score":2,"Answer":"No, there are no features currently available in MongoDB equivalent to hooks or triggers.  It'd be best to handle this sort of thing from within your application logic.","Q_Score":2,"Tags":"python,mongodb,hook,server-side,3-tier","A_Id":6277024,"CreationDate":"2011-06-08T02:26:00.000","Title":"What is suggested way to have server-side hooks over mongodb?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a script with several functions that all need to make database calls. I'm trying to get better at writing clean code rather than just throwing together scripts with horrible style. What is generally considered the best way to establish a global database connection that can be accessed anywhere in the script but is not susceptible to errors such as accidentally redefining the variable holding a connection. I'd imagine I should be putting everything in a module? Any links to actual code would be very useful as well. Thanks.","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":317,"Q_Id":6281732,"Users Score":0,"Answer":"Use a model system\/ORM system.","Q_Score":3,"Tags":"python,database,coding-style,mysql-python","A_Id":6282794,"CreationDate":"2011-06-08T15:58:00.000","Title":"Proper way to establish database connection in python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm developing a python code that uses Sqlite in a multi-threaded program. A remote host calls some xmlrpc functions and new threads are created. Each function which is running in a new thread, uses sqlite for either inserting data into or reading data from the database. \nMy problem is that when call the server more than 5 time at the same time, the server breaks with \"segmentation fault\". And the output doesn't provide any other information. Any idea what can cause the problem?","AnswerCount":2,"Available Count":2,"Score":0.1973753202,"is_accepted":false,"ViewCount":1212,"Q_Id":6289821,"Users Score":2,"Answer":"If you read the sqlite documentation (http:\/\/www.sqlite.org\/threadsafe.html), you'll see that it says:\n\nSQLite support three different\n  threading modes:\nSingle-thread. In this mode, all\n  mutexes are disabled and SQLite is\n  unsafe to use in more than a single\n  thread at once.\nMulti-thread. In this mode, SQLite can\n  be safely used by multiple threads\n  provided that no single database\n  connection is used simultaneously in\n  two or more threads.\nSerialized. In serialized mode, SQLite\n  can be safely used by multiple threads\n  with no restriction.\n\nSo it would be that you're either in single-thread mode, or in multi-thread mode and reusing connections. Reusing the connection is only safe in sequential mode (which is slow)\nNow, the Python documentation states that it should not allow you to share connections. Are you using the python-sqlite3 module, or are you natively interfacing with the database?","Q_Score":0,"Tags":"python,multithreading,sqlite","A_Id":6289986,"CreationDate":"2011-06-09T08:04:00.000","Title":"Segmentation Fault in Python multi-threaded Sqlite use!","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm developing a python code that uses Sqlite in a multi-threaded program. A remote host calls some xmlrpc functions and new threads are created. Each function which is running in a new thread, uses sqlite for either inserting data into or reading data from the database. \nMy problem is that when call the server more than 5 time at the same time, the server breaks with \"segmentation fault\". And the output doesn't provide any other information. Any idea what can cause the problem?","AnswerCount":2,"Available Count":2,"Score":0.0996679946,"is_accepted":false,"ViewCount":1212,"Q_Id":6289821,"Users Score":1,"Answer":"My APSW module is threadsafe and you can use that.  The standard Python SQLite cannot be safely used concurrently across multiple threads.","Q_Score":0,"Tags":"python,multithreading,sqlite","A_Id":6313973,"CreationDate":"2011-06-09T08:04:00.000","Title":"Segmentation Fault in Python multi-threaded Sqlite use!","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"Suppose that I have a huge SQLite file (say, 500[MB]) stored in Amazon S3. \nCan a python script that is run on a small EC2 instance directly access and modify that SQLite file? or must I first copy the file to the EC2 instance, change it there and then copy over to S3? \nWill the I\/O be efficient?\nHere's what I am trying to do. As I wrote, I have a 500[MB] SQLite file in S3. I'd like to start say 10 different Amazon EC2 instances that will each read a subset of the file and do some processing (every instance will handle a different subset of the 500[MB] SQLite file). Then, once processing is done, every instance will update only the subset of the data it dealt with (as explained, there will be no overlap of data among processes).\nFor example, suppose that the SQLite file has say 1M rows:\ninstance 1 will deal with (and update) rows 0 - 100000\ninstance 2 will will deal with (and update) rows 100001 - 200000\n.........................\ninstance 10 will deal with (and update) rows 900001 - 1000000\n\nIs it at all possible? Does it sound OK? any suggestions \/ ideas are welcome.","AnswerCount":5,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":7758,"Q_Id":6301795,"Users Score":0,"Answer":"Amazon EFS can be shared among ec2 instances. It's a managed NFS share. SQLITE will still lock the whole DB on write.\nThe SQLITE Website does not recommend NFS shares, though. But depending on the application you can share the DB read-only among several ec2  instances and store the results of your processing somewhere else, then concatenate the results in the next step.","Q_Score":4,"Tags":"python,sqlite,amazon-s3,amazon-ec2","A_Id":38705012,"CreationDate":"2011-06-10T03:54:00.000","Title":"Amazon EC2 & S3 When using Python \/ SQLite?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Suppose that I have a huge SQLite file (say, 500[MB]) stored in Amazon S3. \nCan a python script that is run on a small EC2 instance directly access and modify that SQLite file? or must I first copy the file to the EC2 instance, change it there and then copy over to S3? \nWill the I\/O be efficient?\nHere's what I am trying to do. As I wrote, I have a 500[MB] SQLite file in S3. I'd like to start say 10 different Amazon EC2 instances that will each read a subset of the file and do some processing (every instance will handle a different subset of the 500[MB] SQLite file). Then, once processing is done, every instance will update only the subset of the data it dealt with (as explained, there will be no overlap of data among processes).\nFor example, suppose that the SQLite file has say 1M rows:\ninstance 1 will deal with (and update) rows 0 - 100000\ninstance 2 will will deal with (and update) rows 100001 - 200000\n.........................\ninstance 10 will deal with (and update) rows 900001 - 1000000\n\nIs it at all possible? Does it sound OK? any suggestions \/ ideas are welcome.","AnswerCount":5,"Available Count":2,"Score":0.0798297691,"is_accepted":false,"ViewCount":7758,"Q_Id":6301795,"Users Score":2,"Answer":"Since S3 cannot be directly mounted, your best bet is to create an EBS volume containing the SQLite file and work directly with the EBS volume from another (controller) instance.  You can then create snapshots of the volume, and archive it into S3.  Using a tool like boto (Python API), you can automate the creation of snapshots and the process of moving the backups into S3.","Q_Score":4,"Tags":"python,sqlite,amazon-s3,amazon-ec2","A_Id":6301870,"CreationDate":"2011-06-10T03:54:00.000","Title":"Amazon EC2 & S3 When using Python \/ SQLite?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Suppose that I have a huge SQLite file (say, 500[MB]). Can 10 different python instances access this file at the same time and update different records of it?. Note, the emphasis here is on different records.\nFor example, suppose that the SQLite file has say 1M rows:\ninstance 1 will deal with (and update) rows 0 - 100000\ninstance 2 will will deal with (and update) rows 100001 - 200000\n.........................\ninstance 10 will deal with (and update) rows 900001 - 1000000\n\nMeaning, each python instance will only be updating a unique subset of the file. Will this work, or will I have serious integrity issues?","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1234,"Q_Id":6301816,"Users Score":4,"Answer":"Updated, thanks to Andr\u00e9 Caron. \nYou can do that, but only read operations supports concurrency in SQLite, since entire database is locked on any write operation. SQLite engine will return SQLITE_BUSY status in this situation (if it exceeds default timeout for access). Also consider that this heavily depends on how good file locking is implemented for given OS and file system. In general I wouldn't recommend to use proposed solution, especially considering that DB file is quite large, but you can try.\nIt will be better to use server process based database (MySQL, PostgreSQL, etc.) to implement desired app behaviour.","Q_Score":2,"Tags":"python,sqlite,concurrency","A_Id":6301903,"CreationDate":"2011-06-10T03:58:00.000","Title":"SQLite Concurrency with Python?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I've Collective Intelligence book, but I'm not sure how it can be apply in practical.\nLet say I have a PHP website with mySQL database. User can insert articles with title and content in the database. For the sake of simplicity, we just compare the title.\n\nHow to Make Coffee?\n15 Things About Coffee.\nThe Big Question.\nHow to Sharpen A Pencil?\nGuy Getting Hit in Balls\n\nWe open 'How to Make Coffee?' article and because there are similarity in words with the second and fourth title, they will be displayed in Related Article section.\nHow can I implement this using PHP and mySQL? It's ok if I have to use Python. Thanks in advance.","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":21630,"Q_Id":6302184,"Users Score":0,"Answer":"This can be simply achieved by using wildcards in SQL queries. If you have larger texts and the wildcard seems to be unable to capture the middle part of text then check if the substring of one matches the other. I hope this helps.\nBTW, your question title asks about implementing recommendation system and the question description just asks about matching a field among database records. Recommendation system is a broad topic and comes with many interesting algorithms (e.g, Collaborative filtering, content-based method, matrix factorization, neural networks, etc.). Please feel free to explore these advanced topics if your project is to that scale.","Q_Score":7,"Tags":"php,python,mysql,recommendation-engine","A_Id":47667603,"CreationDate":"2011-06-10T05:05:00.000","Title":"How to Implement A Recommendation System?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm using MySQLdb in Python.\nI have an update that may succeed or fail:\n\n  UPDATE table\n     SET reserved_by = PID\n         state = \"unavailable\"\n   WHERE state = \"available\"\n     AND id = REQUESTED_ROW_ID\n   LIMIT 1;\n\nAs you may be able to infer, multiple processes are using the database, and I need processes to be able to securely grab rows for themselves, without race conditions causing problems.\nMy theory (perhaps incorrect) is that only one process will be able to succeed with this query (.rowcount=1) -- the others will fail (.rowcount=0) or get a different row (.rowcount=1).\nThe problem is, it appears that everything that happens through MySQLdb happens in a virtual world -- .rowcount reads =1, but you can't really know whether anything really happened, until you perform a .commit().\nMy questions:\n\nIn MySQL, is a single UPDATE atomic within itself?  That is, if the same UPDATE above (with different PID values, but the same REQUESTED_ROW_ID) were sent to the same MySQL server at \"once,\" am I guaranteed that one will succeed and the other will fail?\nIs there a way to know, after calling \"conn.commit()\", whether there was a meaningful change or not?\n** Can I get a reliable .rowcount for the actual commit operation?\nDoes the .commit operation send the actual query (SET's and WHERE conditions intact,) or does it just perform the SETs on affected rows, independent the WHERE clauses that inspired them?\nIs my problem solved neatly by .autocommit?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":576,"Q_Id":6337798,"Users Score":0,"Answer":"Turn autocommit on. \nThe commit operation just \"confirms\" updates already done. The alternative is rollback, which \"undoes\" any updates already made.","Q_Score":0,"Tags":"python,mysql,connect,mysql-python,rowcount","A_Id":6339210,"CreationDate":"2011-06-14T00:11:00.000","Title":"How do I get the actual cursor.rowcount upon .commit?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I want to do the following:\n\nHave a software running written in Python 2.7\nThis software connects to a database (Currently a MySQL database)\nThis software listen for connections on a port X on TCP\nWhen a connection is established, a client x request or command something, then the software use the database to store, remove or fetch information (Based on the request or command).\n\nWhat I currently have in head is the classic approach of connecting to the database, store the connection to the database in an object (as a variable) that is passed in the threads that are spawned by the connection listener, then these threads use the variable in the object to do what they need to do with the database connection. (I know that multi-processing is better then multi-threading in Python, but it's not related to my question at this time)\nNow my question, how should I use SQLAlchemy in this context? I am quite confused even although I have been reading quite a lot of documentation about it and there doesn't seem to be \"good\" examples on how to handle this kind of situation specifically even although I have been searching quite a lot.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":183,"Q_Id":6337812,"Users Score":1,"Answer":"What is the problem here? SQLAlchemy maintains a thread-local connection pool..what else do you need?","Q_Score":0,"Tags":"python,sqlalchemy","A_Id":6338431,"CreationDate":"2011-06-14T00:14:00.000","Title":"How to use SQLAlchemy in this context","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I've trying to make large changes to a number of excel workbooks(over 20). Each workbook contains about 16 separate sheets, and I want to write a script that will loop through each workbook and the sheets contains inside and write\/modify the cells that I need. I need to keep all string validation, macros, and formatting. All the workbooks are in 2007 format.\nI've already looked at python excel libaries and PHPexcel, but macros, buttons, formulas, string validation, and formatting and not kept when the new workbook is written. Is there an easy way to do this, or will I have to open up each workbook individually and commit the changes. I'm trying to avoid creating a macro in VBscript and having to open up each workbook separately to commit the changes I need.","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":3284,"Q_Id":6348011,"Users Score":0,"Answer":"You can also use the PyWin32 libraries to script this with Python using typical COM techniques. This lets you use Python to do your processing, and still save all of the extra parts of each workbook that other Python Excel libraries may not handle.","Q_Score":4,"Tags":"python,vba,scripting,excel","A_Id":6361909,"CreationDate":"2011-06-14T18:09:00.000","Title":"Scripting changes to multiple excel workbooks","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm looking to implement an audit trail for a reasonably complicated relational database, whose schema is prone to change. One avenue I'm thinking of is using a DVCS to track changes.\n(The benefits I can imagine are: schemaless history, snapshots of entire system's state, standard tools for analysis, playback and migration, efficient storage, separate system, keeping DB clean. The database is not write-heavy and history is not not a core feature, it's more for the sake of having an audit trail. Oh and I like trying crazy new approaches to problems.)\nI'm not an expert with these systems (I only have basic git familiarity), so I'm not sure how difficult it would be to implement. I'm thinking of taking mercurial's approach, but possibly storing the file contents\/manifests\/changesets in a key-value data store, not using actual files.\nData rows would be serialised to json, each \"file\" could be an row. Alternatively an entire table could be stored in a \"file\", with each row residing on the line number equal to its primary key (assuming the tables aren't too big, I'm expecting all to have less than 4000 or so rows. This might mean that the changesets could be automatically generated, without consulting the rest of the table \"file\".\n(But I doubt it, because I think we need a SHA-1 hash of the whole file. The files could perhaps be split up by a predictable number of lines, eg 0 < primary key < 1000 in file 1, 1000 < primary key < 2000 in file 2 etc, keeping them smallish)\nIs there anyone familiar with the internals of DVCS' or data structures in general who might be able to comment on an approach like this? How could it be made to work, and should it even be done at all?\nI guess there are two aspects to a system like this: 1) mapping SQL data to a DVCS system and 2) storing the DVCS data in a key\/value data store (not files) for efficiency.\n(NB the json serialisation bit is covered by my ORM)","AnswerCount":3,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":386,"Q_Id":6380623,"Users Score":0,"Answer":"If the database is not write-heavy (as you say), why not just implement the actual database tables in a way that achieves your goal?  For example, add a \"version\" column.  Then never update or delete rows, except for this special column, which you can set to NULL to mean \"current,\" 1 to mean \"the oldest known\", and go up from there.  When you want to update a row, set its version to the next higher one, and insert a new one with no version.  Then when you query, just select rows with the empty version.","Q_Score":2,"Tags":"python,git,mercurial,rdbms,audit-trail","A_Id":6380661,"CreationDate":"2011-06-17T01:55:00.000","Title":"Using DVCS for an RDBMS audit trail","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm looking to implement an audit trail for a reasonably complicated relational database, whose schema is prone to change. One avenue I'm thinking of is using a DVCS to track changes.\n(The benefits I can imagine are: schemaless history, snapshots of entire system's state, standard tools for analysis, playback and migration, efficient storage, separate system, keeping DB clean. The database is not write-heavy and history is not not a core feature, it's more for the sake of having an audit trail. Oh and I like trying crazy new approaches to problems.)\nI'm not an expert with these systems (I only have basic git familiarity), so I'm not sure how difficult it would be to implement. I'm thinking of taking mercurial's approach, but possibly storing the file contents\/manifests\/changesets in a key-value data store, not using actual files.\nData rows would be serialised to json, each \"file\" could be an row. Alternatively an entire table could be stored in a \"file\", with each row residing on the line number equal to its primary key (assuming the tables aren't too big, I'm expecting all to have less than 4000 or so rows. This might mean that the changesets could be automatically generated, without consulting the rest of the table \"file\".\n(But I doubt it, because I think we need a SHA-1 hash of the whole file. The files could perhaps be split up by a predictable number of lines, eg 0 < primary key < 1000 in file 1, 1000 < primary key < 2000 in file 2 etc, keeping them smallish)\nIs there anyone familiar with the internals of DVCS' or data structures in general who might be able to comment on an approach like this? How could it be made to work, and should it even be done at all?\nI guess there are two aspects to a system like this: 1) mapping SQL data to a DVCS system and 2) storing the DVCS data in a key\/value data store (not files) for efficiency.\n(NB the json serialisation bit is covered by my ORM)","AnswerCount":3,"Available Count":2,"Score":0.1325487884,"is_accepted":false,"ViewCount":386,"Q_Id":6380623,"Users Score":2,"Answer":"I've looked into this a little on my own, and here are some comments to share.\nAlthough I had thought using mercurial from python would make things easier, there's a lot of functionality that the DVCS's have that aren't necessary (esp branching, merging). I think it would be easier to simply steal some design decisions and implement a basic system for my needs. So, here's what I came up with.\nBlobs\nThe system makes a json representation of the record to be archived, and generates a SHA-1 hash of this (a \"node ID\" if you will). This hash represents the state of that record at a given point in time and is the same as git's \"blob\".\nChangesets\nChanges are grouped into changesets. A changeset takes note of some metadata (timestamp, committer, etc) and links to any parent changesets and the current \"tree\".\nTrees\nInstead of using Mercurial's \"Manifest\" approach, I've gone for git's \"tree\" structure. A tree is simply a list of blobs (model instances) or other trees. At the top level, each database table gets its own tree. The next level can then be all the records. If there are lots of records (there often are), they can be split up into subtrees.\nDoing this means that if you only change one record, you can leave the untouched trees alone. It also allows each record to have its own blob, which makes things much easier to manage.\nStorage\nI like Mercurial's revlog idea, because it allows you to minimise the data storage (storing only changesets) and at the same time keep retrieval quick (all changesets are in the same data structure). This is done on a per record basis.\nI think a system like MongoDB would be best for storing the data (It has to be key-value, and I think Redis is too focused on keeping everything in memory, which is not important for an archive). It would store changesets, trees and revlogs. A few extra keys for the current HEAD etc and the system is complete.\nBecause we're using trees, we probably don't need to explicitly link foreign keys to the exact \"blob\" it's referring to. Justing using the primary key should be enough. I hope!\nUse case: 1. Archiving a change\nAs soon as a change is made, the current state of the record is serialised to json and a hash is generated for its state. This is done for all other related changes and packaged into a changeset. When complete, the relevant revlogs are updated, new trees and subtrees are generated with the new object (\"blob\") hashes and the changeset is \"committed\" with meta information.\nUse case 2. Retrieving an old state\nAfter finding the relevant changeset (MongoDB search?), the tree is then traversed until we find the blob ID we're looking for. We go to the revlog and retrieve the record's state or generate it using the available snapshots and changesets. The user will then have to decide if the foreign keys need to be retrieved too, but doing that will be easy (using the same changeset we started with).\nSummary\nNone of these operations should be too expensive, and we have a space efficient description of all changes to a database. The archive is kept separately to the production database allowing it to do its thing and allowing changes to the database schema to take place over time.","Q_Score":2,"Tags":"python,git,mercurial,rdbms,audit-trail","A_Id":6396514,"CreationDate":"2011-06-17T01:55:00.000","Title":"Using DVCS for an RDBMS audit trail","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm trying to figure out how to use python's mysqldb. I can do my job with my current knownledge, but I want to use the best practices.\nShould I close properly my cursor? Exiting the program isn't close it autmatically? (Shouldn't I expect the object destructor to do it anyway?)\nShould I create new cursors for every query, or one cursor is enough for multiple different queries in the same DB?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":742,"Q_Id":6453067,"Users Score":2,"Answer":"Should I close properly my cursor?\n\nYes, you should.  Explicit is better than implicit.\n\nShould I create new cursors for every\n  query, or one cursor is enough for\n  multiple different queries in the same\n  DB?\n\nThis depends on how you use this cursor.  For simple tasks it is enough to use one cursor.  For some complex application it is better to create separate cursor for each batch of SQL-queries.","Q_Score":2,"Tags":"python,cursor,mysql-python","A_Id":6453159,"CreationDate":"2011-06-23T11:08:00.000","Title":"How to properly use mysqldb in python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"How can Flask \/ SQLAlchemy be configured to create a new database connection if one is not present?\nI have an infrequently visited Python \/ Flask server which uses SQLAlchemy. It gets visited every couple of days, and on the first visit it often throws a \"MySQL server has gone away\" error. Subsequent page views are fine, but it looks unprofessional to have this initial error.\nI'd like to know the correct way to handle this - advice like \"make a really long time out\", which would be about 4 days long in this case, doesn't seem correct. How can I test for the lack of a database connection and create one if needed?","AnswerCount":7,"Available Count":2,"Score":1.0,"is_accepted":false,"ViewCount":33654,"Q_Id":6471549,"Users Score":6,"Answer":"The pessimistic approach as described by @wim \n\npool_pre_ping=True\n\ncan now be done for Flask-SQLAlchemy using a config var -->\n\nSQLALCHEMY_POOL_PRE_PING = True","Q_Score":64,"Tags":"python,mysql,sqlalchemy,flask,database-connection","A_Id":58821330,"CreationDate":"2011-06-24T17:34:00.000","Title":"Avoiding \"MySQL server has gone away\" on infrequently used Python \/ Flask server with SQLAlchemy","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"How can Flask \/ SQLAlchemy be configured to create a new database connection if one is not present?\nI have an infrequently visited Python \/ Flask server which uses SQLAlchemy. It gets visited every couple of days, and on the first visit it often throws a \"MySQL server has gone away\" error. Subsequent page views are fine, but it looks unprofessional to have this initial error.\nI'd like to know the correct way to handle this - advice like \"make a really long time out\", which would be about 4 days long in this case, doesn't seem correct. How can I test for the lack of a database connection and create one if needed?","AnswerCount":7,"Available Count":2,"Score":0.057080742,"is_accepted":false,"ViewCount":33654,"Q_Id":6471549,"Users Score":2,"Answer":"When I encountered this error I was storing a LONGBLOB \/ LargeBinary image ~1MB in size.  I had to adjust the max_allowed_packet config setting in MySQL.  \nI used mysqld --max-allowed-packet=16M","Q_Score":64,"Tags":"python,mysql,sqlalchemy,flask,database-connection","A_Id":51015137,"CreationDate":"2011-06-24T17:34:00.000","Title":"Avoiding \"MySQL server has gone away\" on infrequently used Python \/ Flask server with SQLAlchemy","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have to read incoming data from a barcode scanner using pyserial. Then I have to store the contents into a MySQL database. I have the database part but not the serial part. can someone show me examples of how to do this. I'm using a windows machine.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":916,"Q_Id":6471569,"Users Score":1,"Answer":"You will find it easier to use a USB scanner. These will decode the scan, and send it as if it were typed on the keyboard, and entered with a trailing return. \nThe barcode is typically written with leading and trailing * characters, but these are not sent with the scan. \nThus you print  \"*AB123*\" using a 3 of 9 font, and when it is scanned sys.stdin.readline().stript() will return \"AB123\".\nThere are more than a few options that can be set in the scanner, so you need to read the manual. I have shown the factory default above for a cheap nameless scanner I bought from Amazon.","Q_Score":1,"Tags":"python,pyserial","A_Id":6474062,"CreationDate":"2011-06-24T17:35:00.000","Title":"Reading incoming data from barcode","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I couldn't find any information about this in the documentation, but how can I get a list of tables created in SQLAlchemy?\nI used the class method to create the tables.","AnswerCount":14,"Available Count":1,"Score":1.0,"is_accepted":false,"ViewCount":133023,"Q_Id":6473925,"Users Score":99,"Answer":"There is a method in engine object to fetch the list of tables name. engine.table_names()","Q_Score":133,"Tags":"python,mysql,sqlalchemy,pyramid","A_Id":30554677,"CreationDate":"2011-06-24T21:25:00.000","Title":"SQLAlchemy - Getting a list of tables","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm dealing with some big (tens of millions of records, around 10gb) database files using SQLite.  I'm doint this python's standard interface.\nWhen I try to insert millions of records into the database, or create indices on some of the columns, my computer slowly runs out of memory.  If I look at the normal system monitor, it looks like the majority of the system memory is free.  However, when I use top, it looks like I have almost no system memory free.  If I sort the processes by their memory consuption, then non of them uses more than a couple percent of my memory (including the python process that is running sqlite).\nWhere is all the memory going?  Why do top and Ubuntu's system monitor disagree about how much system memory I have?  Why does top tell me that I have very little memory free, and at the same time not show which process(es) is (are) using all the memory?\nI'm running Ubuntu 11.04, sqlite3, python 2.7.","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1060,"Q_Id":6491856,"Users Score":0,"Answer":"The memory may be not assigned to a process, but it can be e.g. a file on tmpfs filesystem (\/dev\/shm, \/tmp sometimes). You should show us the output of top or free (please note those tools do not show a single 'memory usage' value) to let us tell something more about the memory usage.\nIn case of inserting records to a database it may be a temporary image created for the current transaction, before it is committed to the real database. Splitting the insertion into many separate transactions (if applicable) may help.\nI am just guessing, not enough data.\nP.S. It seems I mis-read the original question (I assumed the computer slows down) and there is no problem. sehe's answer is probably better.","Q_Score":2,"Tags":"python,sqlite,memory,ubuntu,memory-leaks","A_Id":6491966,"CreationDate":"2011-06-27T11:03:00.000","Title":"Why does running SQLite (through python) cause memory to \"unofficially\" fill up?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm doing a project that is serial based and has to update a database when a barcode is being read. Which programming language has better tools for working with a MySQl database and Serial communication. I debating right now between python and realbasic.","AnswerCount":2,"Available Count":2,"Score":0.2913126125,"is_accepted":false,"ViewCount":1691,"Q_Id":6498272,"Users Score":3,"Answer":"It's hard to imagine that Realbasic is a better choice than Python for any project.","Q_Score":0,"Tags":"python,mysql,serial-port,realbasic","A_Id":6498450,"CreationDate":"2011-06-27T20:02:00.000","Title":"What language is better for serial programming and working with MySQL database? Python? Realbasic?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm doing a project that is serial based and has to update a database when a barcode is being read. Which programming language has better tools for working with a MySQl database and Serial communication. I debating right now between python and realbasic.","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":1691,"Q_Id":6498272,"Users Score":3,"Answer":"Python is a general purpose language with tremendous community support and a \"batteries-included\" philosophy that leads to simple-designs that focus on the business problem at hand. It is a good choice for a wide variety of projects.\nThe only reasons not to choose Python would be:\n\nYou (or your team) have greater experience in another general purpose language with good library and community support.\nYou have a particular problem that is handled best by a specialty language that was written with that sort of problem in mind.\n\nThe only thing I know about RealBASIC is that I hadn't heard of it until now, so it's a lock that it doesn't have quite the community of Python. (Exhibit A: 60,000 Python questions on SO, only 49 RealBASIC questions.) And if it is a derivative of BASIC, it would be not be a specialty language.\nPython seems a clear choice here, unless it means learning a new language, and you are proficient with RealBASIC.","Q_Score":0,"Tags":"python,mysql,serial-port,realbasic","A_Id":6498607,"CreationDate":"2011-06-27T20:02:00.000","Title":"What language is better for serial programming and working with MySQL database? Python? Realbasic?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"When building a website, one have to decide how to store the session info, when a user is logged in.\nWhat is a pros and cons of storing each session in its own file versus storing it in a database?","AnswerCount":3,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":2180,"Q_Id":6510075,"Users Score":3,"Answer":"I generally wouldnt ever store this information in a file - you run the risk of potentially swapping this file in and out of memory (yes it could be cached at times) but I would rather use an in memory mechanism designed as such and you are then using something that is fairly nonstandard.\nIn ASP.Net \n\nyou can use in in memory collection that is good for use on a single server. if you need multiple load balanced web servers (web farm) and a user could go to any other server as they come in for each request, this option is not good. If the web process restarts, the sessions are lost. They can also timeout. \nYou can use a state server in asp.net for multiple server access - this runs outside of your webserver's process. If the web process restarts - you are OK and multiple servers access this. This traffic going to the state server is not encrypted and you would ideally use IPSEC policies to secure the traffic in a more secure environment.\nYou can use sql server to manage state (automatically) by setting up the web.config to use sql server as your session database. This gives the advantage of a high performance database and multi server access.\nYou can use your own sessions in a database if you need them to persist to a long time outside of the normal mechanism and want tighter control on the database fields (maybe you want to query specific fields)\n\nAlso just out of curiosity - maybe you are referring to sessions as user preferences? In that case research asp.net profiles","Q_Score":7,"Tags":"php,asp.net,python,ruby-on-rails,ruby","A_Id":6510307,"CreationDate":"2011-06-28T16:45:00.000","Title":"What is the pros\/cons of storing session data in file vs database?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"When building a website, one have to decide how to store the session info, when a user is logged in.\nWhat is a pros and cons of storing each session in its own file versus storing it in a database?","AnswerCount":3,"Available Count":2,"Score":0.0665680765,"is_accepted":false,"ViewCount":2180,"Q_Id":6510075,"Users Score":1,"Answer":"I'm guessing, based on your previous questions, that this is being asked in the context of using perl's CGI::Application module, with CGI::Application::Plugin::Session. If you use that module with the default settings, it will write the session data into files stored in the \/tmp directory - which is very similar to what PHP does. If your app is running in a shared hosting environment, you probably do NOT want to do this, for security reasons, since other users may be able to view\/modify data in \/tmp. You can fix this by writing the files into a directory that only you have permission to read\/write (i.e., not \/tmp). While developing, I much prefer to use YAML for serialization, rather than the default (storable), since it is human-readable. If you have your own web server, and you're able to run your database (mysql) server on the same machine, then storing the session data in a database instead of a file will usually yield higher performance - especially if you're able to maintain a persistent database connection (i.e. using mod_perl or fastcgi). BUT - if your database is on a remote host, and you have to open a new connection each time you need to update session data, then performance may actually be worse, and writing to a file may be better. Note that you can also use sqlite, which looks like a database to your app, but is really just a file on your local file system. Regardless of performance, the database option may be undesirable in shared-host environments because of bandwidth limitations, and other resource restrictions. The performance difference is also probably negligible for a low-traffic site (i.e., a few thousand hits per day).","Q_Score":7,"Tags":"php,asp.net,python,ruby-on-rails,ruby","A_Id":6527272,"CreationDate":"2011-06-28T16:45:00.000","Title":"What is the pros\/cons of storing session data in file vs database?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a pyramid project that uses mongodb for storage. Now I'm trying to write a test but how do I specify connection to the mongodb?\nMore specifically, which database should I connect to (test?) and how do I use fixtures? In Django it creates a temporary database but how does it work in pyramid?","AnswerCount":1,"Available Count":1,"Score":0.3799489623,"is_accepted":false,"ViewCount":594,"Q_Id":6515160,"Users Score":2,"Answer":"Just create a database in your TestCase.setUp and delete in TestCase.tearDown\nYou need mongodb running because there is no mongolite3 like sqlite3 for sql\nI doubt that django is able to create a temporary file to store a mongodb database. It probably just use sqlite:\/\/\/ which create a database with a memory storage.","Q_Score":2,"Tags":"python,mongodb,pyramid","A_Id":6934811,"CreationDate":"2011-06-29T02:30:00.000","Title":"How do i create unittest in pyramid with mongodb?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I've used a raw SQL Query to access them, and it seems to have worked.  However, I can't figure out a way to actually print the results to an array.  The only thing that I can find is  the cursor.fetchone() command, which gives me a single row.\nIs there any way that I can return an entire column in a django query set?","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":223,"Q_Id":6539687,"Users Score":0,"Answer":"You can use cursor.fetchall() instead of cursor.fetchone() to retrieve all rows.\nAnd then extract nessesary field:\n\nraw_items = cursor.fetchall()\nitems = [ item.field for item in raw_items ]","Q_Score":0,"Tags":"python,django","A_Id":6539716,"CreationDate":"2011-06-30T18:54:00.000","Title":"How do I use django db API to save all the elements of a given column in a dictionary?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I've used a raw SQL Query to access them, and it seems to have worked.  However, I can't figure out a way to actually print the results to an array.  The only thing that I can find is  the cursor.fetchone() command, which gives me a single row.\nIs there any way that I can return an entire column in a django query set?","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":223,"Q_Id":6539687,"Users Score":1,"Answer":"dict(MyModel.objects.values_list('id', 'my_column')) will return a dictionary with all elements of my_column with the row's id as the key. But probably you're just looking for a list of all the values, which you should receive via MyModel.objects.values_list('my_column', flat=True)!","Q_Score":0,"Tags":"python,django","A_Id":6539798,"CreationDate":"2011-06-30T18:54:00.000","Title":"How do I use django db API to save all the elements of a given column in a dictionary?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a photo gallery with an album model (just title and date and stuff) and a photo model with a foriegn key to the album and three imageFields in it (regular, mid and thumb).\nWhen a user delete an album i need to delete all the photos reletaed to the album (from server) then all the DB records that point to the album and then the album itself...\nCouldn't find anything about this and actualy found so many answers what one say the oposite from the other.\nCan any one please clarify this point, how does this is beeing done in the real world?\nThank you very much,\nErez","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":80,"Q_Id":6550003,"Users Score":0,"Answer":"Here is a possible answer for the question i figured out:\n\nGetting the list of albums in a string, in my case separated by commas \nYou need to import shutil, then:\n@login_required\ndef remove_albums(request):\n    if request.is_ajax():\n        if request.method == 'POST':\n            #if the ajax call for delete what ok we get the list of albums to delete\n            albums_list = request.REQUEST['albums_list'].rsplit(',')\n            for album in albums_list:\n                obj_album = Album.objects.get(id=int(album))\n                #getting the directory for the images than need to be deleted\n                dir_path = MEDIA_ROOT + '\/images\/galleries\/%d' % obj_album.id\n                #deleting the DB record\n                obj_album.delete()\n                #testing if there is a folder (there might be a record with no folder if no file was uploaded - deleting the album before uploading images)\n                try:\n                    #deleting the folder and all the files in it\n                    shutil.rmtree(dir_path)\n                except OSError:\n                    pass\n    return HttpResponse('')\n\nSorry for how the code look like, don't know why, I can't make it show correct...\nHave fun and good luck :-)","Q_Score":1,"Tags":"python,django,django-models,django-views","A_Id":6553381,"CreationDate":"2011-07-01T15:30:00.000","Title":"How to delete an object and all related objects with all imageFields insite them (photo gallery)","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"(1) What's the fastest way to check if an item I'm about to \"insert\" into a MongoDB collection is unique (and if so not insert it)\n(2) For an existing database, what's the fastest way to look at all the entries and remove duplicates but keep one copy i.e. like a \"set\" function: {a,b,c,a,a,b} -> {a,b,c}\n\nI am aware that technically speaking each entry is unique, since they get a unique ObjectID\nYou may assume the entries are completely flat key:value lists\nSolutions with indexing are fine\nI prefer Python code (i.e. mongo python API) if possible\n\nThanks!","AnswerCount":1,"Available Count":1,"Score":0.3799489623,"is_accepted":false,"ViewCount":824,"Q_Id":6567511,"Users Score":2,"Answer":"(1) Create a unique index on the related columns and catch the error upon insertion time","Q_Score":0,"Tags":"python,mongodb","A_Id":6567552,"CreationDate":"2011-07-04T05:11:00.000","Title":"Fastest Way to (1) not insert duplicate entry (2) consolidate duplicates in Mongo DB?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"Our site has two separate projects connected to the same database. This is implemented by importing the models from project1 into project2 and using it to access and manipulate data.\nThis works fine on our test server, but we are planning deployment and we decided we would rather have the projects on two separate machines, with the database on a third one.\nI have been looking around for ideas on how to import the model from a project on another machine but that doesn't seem to be possible. \nAn obvious solution would be to put the models in a separate app and have it on both boxes, but that means code is duplicated and changes have to be applied twice.\nI'm looking for suggestions on how to deal with this and am wondering if other people have encountered similar issues. We'll be deploying on AWS if that helps. Thanks.","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":253,"Q_Id":6572203,"Users Score":1,"Answer":"This isn't really a Django question. It is more a Python Question.\nHowever to answer your question Django is going to have to be able to import these files one way or another. If they are on seperate machines you really should refactor the code out into it's own app and then install this app on each of the machines.\nThe only other way I can think of to do this is to make your own import hook that can import a file from across a network but that is a really bad idea for a multitude of reasons.","Q_Score":2,"Tags":"python,django,deployment,architecture,amazon-web-services","A_Id":6574660,"CreationDate":"2011-07-04T13:31:00.000","Title":"separate django projects on different machines using a common database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm writing my first web site, and am dealing with user registration.\nOne common problem to me like to everyone else is to detect user already exist.\nI am writing the app with python, and postgres as database.\nI have currently come up with 2 ideas:\n1) \nlock(mutex)\nu = select from db where name = input_name\nif u == null insert into db (name) values (input_name)\nelse return 'user already exist'\nunlock(mutex)\n2)\ntry: insert into db (name) values(input)\nexcept: return 'user already exist'\nThe first way is to use mutex lock for clear logic, while the second way using exception to indicate user existence. \nCan anyone discuss what are the pros and cons of both of the methods?","AnswerCount":2,"Available Count":2,"Score":0.1973753202,"is_accepted":false,"ViewCount":235,"Q_Id":6580723,"Users Score":2,"Answer":"I think both will work, and both are equally bad ideas. :) My point is that implementing user authentication in python\/pg has been done so many times in the past that there's hardly justification for writing it yourself. Have you had a look at Django, for example? It will take care of this for you, and much more, and let you focus your efforts on your particular application.","Q_Score":0,"Tags":"python,sql,database","A_Id":6580794,"CreationDate":"2011-07-05T09:47:00.000","Title":"Detect users already exist in database on user registration","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm writing my first web site, and am dealing with user registration.\nOne common problem to me like to everyone else is to detect user already exist.\nI am writing the app with python, and postgres as database.\nI have currently come up with 2 ideas:\n1) \nlock(mutex)\nu = select from db where name = input_name\nif u == null insert into db (name) values (input_name)\nelse return 'user already exist'\nunlock(mutex)\n2)\ntry: insert into db (name) values(input)\nexcept: return 'user already exist'\nThe first way is to use mutex lock for clear logic, while the second way using exception to indicate user existence. \nCan anyone discuss what are the pros and cons of both of the methods?","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":235,"Q_Id":6580723,"Users Score":0,"Answer":"Slightly different, I usually do a select query via AJAX to determine if a username already exists, that way I can display a message on the UI explaining that the name is already taken and suggest another before the submit the registration form.","Q_Score":0,"Tags":"python,sql,database","A_Id":6580784,"CreationDate":"2011-07-05T09:47:00.000","Title":"Detect users already exist in database on user registration","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Im trying to use Spyder with pyodbc to connect mysql using a PyQT4 gui framework. \nI have pyodbc in Spyder figure out.\nHow do I use PyQt4 to get info into gui's?  I'm looking to use gui on Fedora and winx64.\nEdit: I figured out the fedora driver. Can anyone help me with QMYSQL driver.","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":842,"Q_Id":6582404,"Users Score":0,"Answer":"Have you considered using PyQt's built-in MySQL support? This could make it a bit easier to display DB info, depending on what you want the interface to look like.","Q_Score":0,"Tags":"python,pyqt4,spyder","A_Id":6644662,"CreationDate":"2011-07-05T12:07:00.000","Title":"How connect Spyder to mysql on Winx64 and Fedora?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm trying to have a purely in-memory SQLite database in Django, and I think I have it working, except for an annoying problem:\nI need to run syncdb before using the database, which isn't too much of a problem. The problem is that it needs to create a superuser (in the auth_user table, I think) which requires interactive input.\nFor my purposes, I don't want this -- I just want to create it in memory, and I really don't care about the password because I'm the only user. :) I just want to hard-code a password somewhere, but I have no idea how to do this programmatically.\nAny ideas?","AnswerCount":3,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1200,"Q_Id":6599716,"Users Score":3,"Answer":"Disconnect django.contrib.auth.management.create_superuser from the post_syncdb signal, and instead connect your own function that creates and saves a new superuser User with the desired password.","Q_Score":1,"Tags":"python,database,django,sqlite,in-memory-database","A_Id":6600219,"CreationDate":"2011-07-06T16:20:00.000","Title":"Django In-Memory SQLite3 Database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Is there an elegant way to do an INSERT ... ON DUPLICATE KEY UPDATE in SQLAlchemy? I mean something with a syntax similar to inserter.insert().execute(list_of_dictionaries) ?","AnswerCount":9,"Available Count":1,"Score":-0.022218565,"is_accepted":false,"ViewCount":60718,"Q_Id":6611563,"Users Score":-1,"Answer":"As none of these solutions seem all the elegant. A brute force way is to query to see if the row exists. If it does delete the row and then insert otherwise just insert. Obviously some overhead involved but it does not rely on modifying the raw sql and it works on non orm stuff.","Q_Score":44,"Tags":"python,mysql,sqlalchemy","A_Id":17374720,"CreationDate":"2011-07-07T13:43:00.000","Title":"SQLAlchemy ON DUPLICATE KEY UPDATE","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a python loader using Andy McCurdy's python library that opens multiple Redis DB connections and sets millions of keys looping through files of lines each containing an integer that is the redis-db number for that record. Alltogether, only 20 databases are open at the present time, but eventually there may be as many as 100 or more.\nI notice that the redis log (set to verbose) always tells me there are \"4 clients connected (0 slaves),... though I know that my 20 are open and are being used.\nSo I'm guessing this is about the connection pooling support built into the python library. Am I correct in that guess? If so the real question is is there a way to increase the pool size -- I have plenty of machine resources, a lot dedicated to Redis? Would increasing the pool size help performance as the number of virtual connections I'm making goes up?\nAt this point, I am actually hitting only ONE connection at a time though I have many open as I shuffle input records among them. But eventually there will be many scripts (2 dozen?) hitting Redis in parallel, mostly reading and I am wondering what effect increasing the pool size would have.\nThanks\nmatthew","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":1371,"Q_Id":6628953,"Users Score":1,"Answer":"So I'm guessing this is about the connection pooling support built into the python library. Am I correct in that guess?\n\nYes.\n\nIf so the real question is is there a way to increase the pool size\n\nNot needed, it will increase connections up to 2**31 per default (andys lib). So your connections are idle anyways.\nIf you want to increase performance, you will need to change the application using redis.\n\nand I am wondering what effect increasing the pool size would have.\n\nNone, at least not in this case.\nIF redis becomes the bottleneck at some point, and you have a multi-core server. You must run multiple redis instances to increase performance, as it only runs on a single core. When you run multiple instances, and doing mostly reads, the slave feature can increase performance as the slaves can be used for all the reads.","Q_Score":1,"Tags":"python,configuration,redis,connection-pooling","A_Id":6703919,"CreationDate":"2011-07-08T18:43:00.000","Title":"configuring connection-pool size with Andy McCurdy's python-for-redis library","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"If I make a live countdown clock like ebay, how do I do this with django and sql?  I'm assuming running a function in django or in sql over and over every second to check the time would be horribly inefficient.  \nIs this even a plausible strategy?\nOr is this the way they do it:\nWhen a page loads, it takes the end datetime from the server and runs a javascript countdown clock against it on the user machine?\nIf so, how do you do the countdown clock with javascript? And how would I be able to delete\/move data once the time limit is over without a user page load? Or is it absolutely necessary for the user to load the page to check the time limit to create an efficient countdown clock?","AnswerCount":2,"Available Count":2,"Score":0.1973753202,"is_accepted":false,"ViewCount":2127,"Q_Id":6639247,"Users Score":2,"Answer":"I don't think this question has anything to do with SQL, really--except that you might retrieve an expiration time from SQL.  What you really care about is just how to display the timeout real-time in the browser, right?\nObviously the easiest way is just to send a \"seconds remaining\" counter to the page, either on the initial load, or as part of an AJAX request, then use Javascript to display the timer, and update it every second with the current value.  I would opt for using a \"seconds remaining\" counter rather than an \"end datetime\", because you can't trust a browser's clock to be set correctly--but you probably can trust it to count down seconds correctly.\nIf you don't trust Javascript, or the client's clock, to be accurate, you could periodically re-send the current \"seconds remaining\" value to the browser via AJAX. I wouldn't do this every second, maybe every 15 or 60 seconds at most.\nAs for deleting\/moving data when the clock expires, you'll need to do all of that in Javascript.\nI'm not 100% sure I answered all of your questions, but your questions seem a bit scattered anyway. If you need more clarification on the theory of operation, please ask.","Q_Score":0,"Tags":"javascript,python,django,time,countdown","A_Id":6639561,"CreationDate":"2011-07-10T04:52:00.000","Title":"Live countdown clock with django and sql?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"If I make a live countdown clock like ebay, how do I do this with django and sql?  I'm assuming running a function in django or in sql over and over every second to check the time would be horribly inefficient.  \nIs this even a plausible strategy?\nOr is this the way they do it:\nWhen a page loads, it takes the end datetime from the server and runs a javascript countdown clock against it on the user machine?\nIf so, how do you do the countdown clock with javascript? And how would I be able to delete\/move data once the time limit is over without a user page load? Or is it absolutely necessary for the user to load the page to check the time limit to create an efficient countdown clock?","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":2127,"Q_Id":6639247,"Users Score":0,"Answer":"I have also encountered the same problem a while ago.\nFirst of all your problem is not related neither django nor sql. It is a general concept and it is not very easy to implement because of overhead in server.\nOne solution come into my mind is keeping start time of the process in the database.\nWhen someone request you to see remaingn time, read it from database, subtract the current time and server that time and in your browser initialize your javascript function with that value and countdown like 15 sec. After that do the same operation with AJAX without waiting user's request.\nHowever, there would be other implementations depending your application. If you explain your application in detail there could be other solutions.\nFor example, if you implement a questionnaire with limited time, then for every answer submit, you should pass the calculated javascript value for that second.","Q_Score":0,"Tags":"javascript,python,django,time,countdown","A_Id":6639878,"CreationDate":"2011-07-10T04:52:00.000","Title":"Live countdown clock with django and sql?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a Django project which has a mysql database backend. How can I export contents from my db to an Excel (xls, xlsx) format?","AnswerCount":4,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1028,"Q_Id":6649990,"Users Score":0,"Answer":"phpMyAdmin has an Export tab, and you can export in CSV.  This can be imported into Excel.","Q_Score":0,"Tags":"python,mysql,django,excel","A_Id":6650011,"CreationDate":"2011-07-11T12:20:00.000","Title":"MySQLdb to Excel","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I try to connect to database in a domain from my virtual machine. \nIt works on XP, but somehow does not work on Win7 and quitting with:\n\"OperationalError: (1042, \"Can't get hostname for your address\")\"\nNow I tried disable Firewall and stuff, but that doesn't matter anyway.\nI don't need the DNS resolving, which will only slow everything down.\nSo I want to use the option \"skip-name-resolve\", but there is no my.ini\nor my.cnf when using MySQLdb for Python, so how can I still use this option?\nThanks for your help\n-Alex","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":60490,"Q_Id":6668073,"Users Score":1,"Answer":"This is an option which needs to be set in the MySQL configuration file on the server. It can't be set by client APIs such as MySQLdb. This is because of the potential security implications.\nThat is, I may want to deny access from a particular hostname. With skip-name-resolve enabled, this won't work. (Admittedly, access control via hostname is probably not the best idea anyway.)","Q_Score":12,"Tags":"python,mysql,mysql-python,resolve","A_Id":6668116,"CreationDate":"2011-07-12T17:00:00.000","Title":"How to use the option skip-name-resolve when using MySQLdb for Python?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm using an object database (ZODB) in order to store complex relationships between many objects but am running into performance issues. As a result I started to construct indexes in order to speed up object retrieval and insertion.  Here is my story and I hope that you can help.\nInitially when I would add an object to the database I would insert it in a branch dedicated to that object type. In order to prevent multiple objects representing the same entity I added a method that would iterate over existing objects in the branch in order to find duplicates. This worked at first but as the database grew in size the time it took to load each object into memory and check attributes grew exponentially and unacceptably.\nTo solve that issue I started to create indexes based on the attributes in the object so that when an object would be added it would be saved in the type branch as well as within an attribute value index branch. For example, say I was saving an person object with attributes firstName = 'John' and lastName = 'Smith', the object would be appended to the person object type branch and would also be appended to lists within the attribute index branch with keys 'John' and 'Smith'.\nThis saved a lot of time with duplicate checking since the new object could be analysed and only the set of objects which intersect within the attribute indexes would need to be checked.\nHowever, I quickly ran into another issue with regards to dealing when updating objects. The indexes would need to updated to reflect the fact that they may not be accurate any more.  This requires either remembering old values so that they could be directly accessed and the object removed or iterating over all values of an attribute type in order to find then remove the object. Either way performance is quickly beginning to degrade again and I can't figure out a way to solve it.\nHas you had this kind of issue before? What did you do solve it, or is this just something that I have to deal with when using OODBMS's?\nThank in advance for the help.","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":601,"Q_Id":6668234,"Users Score":8,"Answer":"Yes, repoze.catalog is nice, and well documented.\nIn short : don't make indexing part of your site structure!\n\nLook at using a container\/item hierarchy to store and traverse content item objects; plan to be able to traverse content by either (a) path (graph edges look like a filesystem) or (b) by identifying singleton containers at some distinct location.  \nIdentify your content using either RFC 4122 UUIDs (uuid.UUID type) or 64-bit integers.\nUse a central catalog to index (e.g. repoze.catalog); the catalog should be at a known location relative to the root application object of your ZODB.  And your catalog will likely index attributes of objects and return record-ids (usually integers) on query.  Your job is to map those integer ids to (perhaps indrecting via UUIDs) to some physical traversal path in the database where you are storing content.  It helps if you use zope.location and zope.container for common interfaces for traversal of your object graph from root\/application downward.\nUse zope.lifecycleevent handlers to index content and keep things fresh.\n\nThe problem -- generalized\nZODB is too flexible: it is just a persistent object graph with transactions, but this leaves room for you to sink or swim in your own data-structures and interfaces.  \nThe solution -- generalized\nUsually, just picking pre-existing idioms from the community around the ZODB will work: zope.lifecycleevent handlers, \"containerish\" traversal using zope.container and zope.location, and something like repoze.catalog.\nMore particular\nOnly when you exhaust the generalized idioms and know why they won't work, try to build your own indexes using the various flavors of BTrees in ZODB.  I actually do this more than I care to admit, but usually have good cause.\nIn all cases, keep your indexes (search, discovery) and site (traversal and storage) structure distinct.\nThe idioms for the problem domain\n\nMaster ZODB BTrees: you likely want:\n\nTo store content objects as subclasses of Persistent in containers that are subclasses of OOBTree providing container interfaces (see below).\nTo store BTrees for your catalog or global indexes or use packages like repoze.catalog and zope.index to abstract that detail away (hint: catalog solutions typically store indexes as OIBTrees that will yield integer record ids for search results; you then typically have some sort of document mapper utility that translates those record ids into something resolvable in your application like a uuid (provided you can traverse the graph to the UUID) or a path (the way the Zope2 catalog does).\n\nIMHO, don't bother working with intids and key-references and such (these are less idiomatic and more difficult if you don't need them).  Just use a Catalog and DocumentMap from repoze.catalog to get results in integer to uuid or path form, and then figure out how to get your object.  Note, you likely want some utility\/singleton that has the job of retrieving your object given an id or uuid returned from a search.\nUse zope.lifecycleevent or similar package that provides synchronous event callback (handler) registrations.  These handlers are what you should call whenever an atomic edit is made on your object (likely once per transaction, but not in transaction machinery).\nLearn the Zope Component Architecture; not an absolute requirement, but surely helpful, even if just to understand zope.interface interfaces of upstream packages like zope.container \nUnderstanding of how Zope2 (ZCatalog) does this: a catalog fronts for multiple indexes or various sorts, which each search for a query, each have specialized data structures, and each return integer record id sequences.  These are merged across indexes by the catalog doing set intersections and returned as a lazy-mapping of \"brain\" objects containing metadata stubs (each brain has a getObject() method to get the actual content object).  Getting actual objects from a catalog search relies upon the Zope2 idiom of using paths from the root application object to identify the location of the item cataloged.","Q_Score":5,"Tags":"python,indexing,zodb,object-oriented-database","A_Id":6674416,"CreationDate":"2011-07-12T17:14:00.000","Title":"Method for indexing an object database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm using an object database (ZODB) in order to store complex relationships between many objects but am running into performance issues. As a result I started to construct indexes in order to speed up object retrieval and insertion.  Here is my story and I hope that you can help.\nInitially when I would add an object to the database I would insert it in a branch dedicated to that object type. In order to prevent multiple objects representing the same entity I added a method that would iterate over existing objects in the branch in order to find duplicates. This worked at first but as the database grew in size the time it took to load each object into memory and check attributes grew exponentially and unacceptably.\nTo solve that issue I started to create indexes based on the attributes in the object so that when an object would be added it would be saved in the type branch as well as within an attribute value index branch. For example, say I was saving an person object with attributes firstName = 'John' and lastName = 'Smith', the object would be appended to the person object type branch and would also be appended to lists within the attribute index branch with keys 'John' and 'Smith'.\nThis saved a lot of time with duplicate checking since the new object could be analysed and only the set of objects which intersect within the attribute indexes would need to be checked.\nHowever, I quickly ran into another issue with regards to dealing when updating objects. The indexes would need to updated to reflect the fact that they may not be accurate any more.  This requires either remembering old values so that they could be directly accessed and the object removed or iterating over all values of an attribute type in order to find then remove the object. Either way performance is quickly beginning to degrade again and I can't figure out a way to solve it.\nHas you had this kind of issue before? What did you do solve it, or is this just something that I have to deal with when using OODBMS's?\nThank in advance for the help.","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":601,"Q_Id":6668234,"Users Score":0,"Answer":"Think about using an attribute hash (something like Java's hashCode()), then use the 32-bit hash value as the key. Python has a hash function, but I am not real familiar with it.","Q_Score":5,"Tags":"python,indexing,zodb,object-oriented-database","A_Id":6668904,"CreationDate":"2011-07-12T17:14:00.000","Title":"Method for indexing an object database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am looking at the Flask tutorial, and it suggests to create a new database connection for each web request. Is it the right way to do things ? I always thought that the database connection should only once be created once for each thread. Can that be done, while maintaining the application as thread-safe, with flask, or other python web servers.","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":11438,"Q_Id":6688413,"Users Score":0,"Answer":"In my experience, it's often a good idea to close connections frequently.  In particular, MySQL likes to close connections that have been idle for a while, and sometimes that can leave the persistent connection in a stale state that can make the application unresponsive.\nWhat you really want to do is optimize the \"dead connection time\", the fraction of the time a connection is up but isn't doing any work.  In the case of creating a new connection with every request, that dead time is really just the setup and teardown time.  If only make a connection once (per thread), and it never goes bad, then the dead time is the idle time.  \nWhen your application is serving only a few requests, the number of connections that occur will also be small, and so there's not much advantage of keeping a connection open, but idle.  On the other extreme, when the application is very busy, connections are almost never idle, and closing a connection that will just be reopened immediately is also wasted.  In the middle, when new requests sometimes follow in flight requests, but sometimes not, you'll have to do some performance tuning on things like pool size, request timeout, and so on.\nA very busy app, which uses a connection pool to keep connections open will only ever see one kind of dead time; waiting for requests that will never return because the connection has gone bad.  A simple solution to this problem is to execute a known, good query (which in MySQL is spelled SELECT 1) before providing a connection from the pool to a request and recycle the connection if it doesn't return quickly.","Q_Score":21,"Tags":"python,mysql,flask","A_Id":6698054,"CreationDate":"2011-07-14T04:13:00.000","Title":"How to preserve database connection in a python web server","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"The datetime module does date validation and math which is fine when you care about reality.\nI need an object that holds dates generated even if they were invalid. Date time is way too strict as sometimes I know year only or year and month only and sometimes I have a date like 2011-02-30.\nIs there a module out there that is like datetime but that can handle invalid dates?\nIf not, what's the best way to handle this while duplicating as little functionality as possible and still allowing date math when it is possible to perform?\nUPDATE\nMotivation for this is integration with multiple systems that use dates and don't care about invalid dates (mysql and perl) in addition to wanting the ability to tell basic general ranges of time. For fuzzy date math start from the beginning of the known unit of time (if I know year and month but not day, use the first, if i know year but no month or day, use january first). This last bit is not necessary but would be nice and I get why it is not common as people who need special case date math will probably build it themselves.\nOne of the major issues I have is loading dates from mysql into python using sqlalchemy and mysqldb -- if you load a value from a date column im mysql that looks like '2011-01-00' in mysql, you get None in python. This is not cool by any stretch.","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":2334,"Q_Id":6697770,"Users Score":0,"Answer":"I haven't heard of such module out there and don't think there is one.\nI would probably end up storing two dates for every instance: 1. the original input as a string, which could contain anything, even \"N\/A\", just for showing back the original value, and 2. parsed and \"normalized\" datetime object which is the closest representation of the input. Depending on the purpose I would allow Null\/None objects where it really couldn't be estimated (like the mentioned \"N\/A\" case) or not. This solution will allow you to revert\/change the \"estimation\" as you do not lose any information.\nIf you don't care about it so much, SQLAlchemy allows declaring your own column and data types for transparently converting such values back and forth into a string column in the DB.","Q_Score":6,"Tags":"python,datetime","A_Id":12212950,"CreationDate":"2011-07-14T17:56:00.000","Title":"allowing invalid dates in python datetime","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"Does anyone know of a way of accessing MS Excel from Python? Specifically I am looking to create new sheets and fill them with data, including formulae. \nPreferably I would like to do this on Linux if possible, but can do it from in a VM if there is no other way.","AnswerCount":6,"Available Count":2,"Score":0.1651404129,"is_accepted":false,"ViewCount":37522,"Q_Id":6698229,"Users Score":5,"Answer":"Long time after the original question, but last answer pushed it top of feed again.   Others might benefit from my experience using python and excel.\nI am using excel and python quite bit.   Instead of using the xlrd, xlwt modules directly, I normally use pandas.   I think pandas uses these modules as imports, but i find it much easier using the pandas provided framework to create and read the spreadsheets.   Pandas's Dataframe structure is very \"spreadsheet-like\" and makes life a lot easier in my opinion.\nThe other option that I use (not in direct answer to your problem)  is DataNitro.   It allows you to use python directly within excel.   Different use case, but you would use it where you would normally have to write VBA code in Excel.","Q_Score":22,"Tags":"python,excel","A_Id":21573501,"CreationDate":"2011-07-14T18:34:00.000","Title":"Excel Python API","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Does anyone know of a way of accessing MS Excel from Python? Specifically I am looking to create new sheets and fill them with data, including formulae. \nPreferably I would like to do this on Linux if possible, but can do it from in a VM if there is no other way.","AnswerCount":6,"Available Count":2,"Score":0.0996679946,"is_accepted":false,"ViewCount":37522,"Q_Id":6698229,"Users Score":3,"Answer":"It's surely possible through the Excel object model via COM: just use win32com modules for Python. Can't remember more but I once controlled the Media Player through COM from Python. It was piece of cake.","Q_Score":22,"Tags":"python,excel","A_Id":6698343,"CreationDate":"2011-07-14T18:34:00.000","Title":"Excel Python API","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Recently I've begun working on exploring ways to convert about 16k Corel Paradox 4.0 database tables (my client has been using a legacy platform over 20 years mainly due to massive logistical matters) to more modern formats (i.e.CSV, SQL, etc.) en mass and so far I've been looking at PHP since it has a library devoted to Paradox data processing however while I'm fairly confident in how to write the conversion code (i.e. simply calling a few file open, close, and write functions) I'm concerned about error detection and ensuring that when running the script, I don't spend hours waiting for it to run only to see 16k corrupt files exported.\nAlso, I'm not fully sure about the logic loop for calling the files. I'm thinking of having the program generate a list of all the files with the appropriate extension and then looping through the list, however I'm not sure if that's ideal for a directory of this size.\nThis is being run on a local Windows 7 x64 system with XAMPP setup (the database is all internal use) so I'm not sure if pure PHP is the best idea -- so I've been wondering if Python or some other lightweight scripting language might be better for handling this.\nThanks very much in advance for any insights and assistance,","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":734,"Q_Id":6709833,"Users Score":0,"Answer":"If you intend to just convert the data which I guess is a process you do only once you will run the script locally as a command script. For that you don't need a web site and thus XAMPP. What language you take is secondary except you say that PHP has a library. Does python or others have one?\nAbout your concern of error detection why not test your script with only one file first. If that conversion is successful you can build your loop and test this on maybe five files, i.e. have a counter that ends the process after that number. It that is still okay you can go on with the rest. You can also write log data and dump a result for every 100 files processed. This way you can see if your script is doing something or idling.","Q_Score":1,"Tags":"php,python,mysql,xampp,php-gtk","A_Id":6711276,"CreationDate":"2011-07-15T15:56:00.000","Title":"Batch converting Corel Paradox 4.0 Tables to CSV\/SQL -- via PHP or other scripts","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Recently I've begun working on exploring ways to convert about 16k Corel Paradox 4.0 database tables (my client has been using a legacy platform over 20 years mainly due to massive logistical matters) to more modern formats (i.e.CSV, SQL, etc.) en mass and so far I've been looking at PHP since it has a library devoted to Paradox data processing however while I'm fairly confident in how to write the conversion code (i.e. simply calling a few file open, close, and write functions) I'm concerned about error detection and ensuring that when running the script, I don't spend hours waiting for it to run only to see 16k corrupt files exported.\nAlso, I'm not fully sure about the logic loop for calling the files. I'm thinking of having the program generate a list of all the files with the appropriate extension and then looping through the list, however I'm not sure if that's ideal for a directory of this size.\nThis is being run on a local Windows 7 x64 system with XAMPP setup (the database is all internal use) so I'm not sure if pure PHP is the best idea -- so I've been wondering if Python or some other lightweight scripting language might be better for handling this.\nThanks very much in advance for any insights and assistance,","AnswerCount":2,"Available Count":2,"Score":0.0996679946,"is_accepted":false,"ViewCount":734,"Q_Id":6709833,"Users Score":1,"Answer":"This is doubtless far too late to help you, but for posterity...\nIf one has a Corel Paradox working environment, one can just use it to ease the transition.\nWe moved the Corel Paradox 9 tables we had into an Oracle schema we built by connecting to the schema (using an alias such as SCHEMA001) then writing this Procedure in a script from inside Paradox:\nProc writeTable(targetTable String)\n   errorTrapOnWarnings(Yes)\n   try\n    tc.open(targetTable)\n    tc.copy(\":SCHEMA001:\" + targetTable) \n    tc.close()\n   onFail\n    errorShow()\n   endTry\nendProc\nOne could highly refine this with more Paradox programming, but you get the idea.  One thing we discovered, though, is that Paradox uses double quotes for the column names when it creates the Oracle version, which means you can get lower-case letters in column names in Oracle, which is a pain.  We corrected that by writing a quick Oracle query to upper() all the resulting column names.\nWe called the procedure like so:\nVar\n   targetTable  String\n   tc           TCursor\nendVar\nmethod run(var eventInfo Event)\n    targetTable = \"SomeTableName\" \n    writeTable(targetTable)\n    msgInfo(\"TransferData.ssl--script finished\",\n            \"That's all, folks!\" )\n    return\nendMethod","Q_Score":1,"Tags":"php,python,mysql,xampp,php-gtk","A_Id":39728385,"CreationDate":"2011-07-15T15:56:00.000","Title":"Batch converting Corel Paradox 4.0 Tables to CSV\/SQL -- via PHP or other scripts","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm storing filenames and filepaths in MySQL.  Retrieving them from the database using LIKE expressions requires that I escape all allowed filename chars that collide with MySQL special chars.  I'm happy to simply use Python's string.replace() method, but was wondering if there was a more standard or built-in method of sanitizing filepaths with SQLAlchemy or dealing with filepaths in MySQL in general.\nI need the solution to be OS-agnostic and established.  It does not need to be implemented in SA.  I'll accept any procedure for encoding that works; failing that, I need a list of all chars that need to be escaped and a smart choice of an escape char.","AnswerCount":4,"Available Count":4,"Score":0.0,"is_accepted":false,"ViewCount":14347,"Q_Id":6713715,"Users Score":0,"Answer":"SQLAlchemy do sanitize for you if you will use regular queries. Maybe the problem that you use like clause. Like require addition escape for such symbols: _%. Thus you will need replace methods if you want to quote like expression.","Q_Score":9,"Tags":"python,mysql,sqlalchemy,escaping,filepath","A_Id":7404552,"CreationDate":"2011-07-15T22:12:00.000","Title":"Escaping special characters in filepaths using SQLAlchemy","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm storing filenames and filepaths in MySQL.  Retrieving them from the database using LIKE expressions requires that I escape all allowed filename chars that collide with MySQL special chars.  I'm happy to simply use Python's string.replace() method, but was wondering if there was a more standard or built-in method of sanitizing filepaths with SQLAlchemy or dealing with filepaths in MySQL in general.\nI need the solution to be OS-agnostic and established.  It does not need to be implemented in SA.  I'll accept any procedure for encoding that works; failing that, I need a list of all chars that need to be escaped and a smart choice of an escape char.","AnswerCount":4,"Available Count":4,"Score":-0.1488850336,"is_accepted":false,"ViewCount":14347,"Q_Id":6713715,"Users Score":-3,"Answer":"Why do you need to escape the file paths? As far as you are not manually writing select \/ insert queries, SQLAlchemy will take care of the escaping when it generates the query internally.\nThe file paths can be inserted as they are into the database.","Q_Score":9,"Tags":"python,mysql,sqlalchemy,escaping,filepath","A_Id":6720094,"CreationDate":"2011-07-15T22:12:00.000","Title":"Escaping special characters in filepaths using SQLAlchemy","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm storing filenames and filepaths in MySQL.  Retrieving them from the database using LIKE expressions requires that I escape all allowed filename chars that collide with MySQL special chars.  I'm happy to simply use Python's string.replace() method, but was wondering if there was a more standard or built-in method of sanitizing filepaths with SQLAlchemy or dealing with filepaths in MySQL in general.\nI need the solution to be OS-agnostic and established.  It does not need to be implemented in SA.  I'll accept any procedure for encoding that works; failing that, I need a list of all chars that need to be escaped and a smart choice of an escape char.","AnswerCount":4,"Available Count":4,"Score":-1.0,"is_accepted":false,"ViewCount":14347,"Q_Id":6713715,"Users Score":-4,"Answer":"You don't need do anything SQLAlchemy will do it for you.","Q_Score":9,"Tags":"python,mysql,sqlalchemy,escaping,filepath","A_Id":7435697,"CreationDate":"2011-07-15T22:12:00.000","Title":"Escaping special characters in filepaths using SQLAlchemy","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm storing filenames and filepaths in MySQL.  Retrieving them from the database using LIKE expressions requires that I escape all allowed filename chars that collide with MySQL special chars.  I'm happy to simply use Python's string.replace() method, but was wondering if there was a more standard or built-in method of sanitizing filepaths with SQLAlchemy or dealing with filepaths in MySQL in general.\nI need the solution to be OS-agnostic and established.  It does not need to be implemented in SA.  I'll accept any procedure for encoding that works; failing that, I need a list of all chars that need to be escaped and a smart choice of an escape char.","AnswerCount":4,"Available Count":4,"Score":-0.1488850336,"is_accepted":false,"ViewCount":14347,"Q_Id":6713715,"Users Score":-3,"Answer":"As I know there isn\u2019t what you are looking for in SQLAlchemy. Just go basestring.replace() method by yourself.","Q_Score":9,"Tags":"python,mysql,sqlalchemy,escaping,filepath","A_Id":7479678,"CreationDate":"2011-07-15T22:12:00.000","Title":"Escaping special characters in filepaths using SQLAlchemy","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am working in python and using xlwt. \nI have got a sample excel sheet and have to generate same excel sheet from python. Now the problem is heading columns are highlighted using some color from excel color palette and I am not able to find the name of color. I need to generate exact copy of sample given to me.\nIs there any function in xlwt which let me read color of cell of one sheet and then put that color in my sheet?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1582,"Q_Id":6723242,"Users Score":0,"Answer":"Best you read the colours from the sample given to you with xlrd. \nIf there are only a few different colours and they stay the same over time, you can also open the file in Excel and use a colour picker tool to get the RGB values of the relevant cells.","Q_Score":3,"Tags":"python,excel,colors,cell,xlwt","A_Id":15435059,"CreationDate":"2011-07-17T10:29:00.000","Title":"Reading background color of a cell of an excel sheet from python?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"So I installed Bitnami Django stack, hoping as proclaimed 'ready-to-run' versions of python and mysql. However, I can't get python to syncdb: \"Error loading MySQLdb module: No module named MySQLdb\"\nI thought the Bitnami package would already install everything necessary in Windows to make mysql and Python work together? Is this not true? \nI don't want to have to deal with installing mysql-python components as that can be frustrating to get working alone as I have tried before.","AnswerCount":3,"Available Count":3,"Score":1.2,"is_accepted":true,"ViewCount":1094,"Q_Id":6738310,"Users Score":2,"Answer":"You'll need to install MySQL for python as Django needs this to do the connecting, once you have the package installed you shouldn't need to configure it though as Django just needs to import from it. \nEdit: from your comments there is a setuptools bundled but it has been replaced by the package distribute, install this python package and you should have access to easy_install which makes it really easy to get new packages. Assuming you've added PYTHONPATH\/scripts to your environment variables, you can call easy_install mysql_python","Q_Score":0,"Tags":"python,mysql,django,mysql-python,bitnami","A_Id":6738365,"CreationDate":"2011-07-18T19:29:00.000","Title":"Mysql-python not installed with bitnami django stack? \"Error loading MySQLdb module: No module named MySQLdb\"","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"So I installed Bitnami Django stack, hoping as proclaimed 'ready-to-run' versions of python and mysql. However, I can't get python to syncdb: \"Error loading MySQLdb module: No module named MySQLdb\"\nI thought the Bitnami package would already install everything necessary in Windows to make mysql and Python work together? Is this not true? \nI don't want to have to deal with installing mysql-python components as that can be frustrating to get working alone as I have tried before.","AnswerCount":3,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":1094,"Q_Id":6738310,"Users Score":0,"Answer":"BitNami DjangoStack already includes the mysql-python components  components. I guess you selected MySQL as the database when installing the BitNami Stack, right? (it also includes PostgreSQL and SQLite). Do you receive the error at installation time? Or later working with your Django project? \nIn which platform are you using the BitNami DjangoStack?","Q_Score":0,"Tags":"python,mysql,django,mysql-python,bitnami","A_Id":6981742,"CreationDate":"2011-07-18T19:29:00.000","Title":"Mysql-python not installed with bitnami django stack? \"Error loading MySQLdb module: No module named MySQLdb\"","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"So I installed Bitnami Django stack, hoping as proclaimed 'ready-to-run' versions of python and mysql. However, I can't get python to syncdb: \"Error loading MySQLdb module: No module named MySQLdb\"\nI thought the Bitnami package would already install everything necessary in Windows to make mysql and Python work together? Is this not true? \nI don't want to have to deal with installing mysql-python components as that can be frustrating to get working alone as I have tried before.","AnswerCount":3,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":1094,"Q_Id":6738310,"Users Score":0,"Answer":"So I got this error after installing Bitnami Django stack on Windows Vista.  Turns out that I had all components installed, but easy_install mysql_python didn't unwrap the entire package...  ?\nI inst... uninst... inst... uninst multiple times, but no combination (using mysql for the startup Project) made any difference.\nIn the end, I simply renamed the egg file (in this case MySQL_python-1.2.3-py2.7-win32.egg) file to .zip and extracted the missing parts into a directory on my PYTHONPATH and everything worked like a charm.","Q_Score":0,"Tags":"python,mysql,django,mysql-python,bitnami","A_Id":12083825,"CreationDate":"2011-07-18T19:29:00.000","Title":"Mysql-python not installed with bitnami django stack? \"Error loading MySQLdb module: No module named MySQLdb\"","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am developing a Django app being a Web frontend to some Oracle database with another local DB keeping app's data such as Guardian permissions. The problem is that it can be modified from different places that I don't have control of.\nLet's say we have 3 models: User, Thesis and UserThesis.\nUserThesis - a table specifying relationship between Thesis and User (User being co-author of Thesis)\nScenario:\n\nUser is removed as an author of Thesis by removing entry in UserThesis table by some other app.\nUser tries to modify Thesis using our Django app. And he succeeds, because Guardian and Django do not know about change in UserThesis.\n\nI thought about some solutions:\n\nHaving some cron job look for changes in UserThesis by checking the modification date of entry. Easy to check for additions, removals would require looking on all relationships again.\nModifying Oracle DB schema to add Guardian DB tables and creating triggers on UserThesis table. I wouldn't like to do this, because of Oracle DB being shared among number of different apps.\nManually checking for relationship in views and templates (heavier load on Oracle).\n\nWhich one is the best? Any other ideas?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":159,"Q_Id":6775359,"Users Score":0,"Answer":"I decided to go with manually checking the permissions, caching it whenever I can. I ended up with get_perms_from_cache(self, user) model method which helps me a lot.","Q_Score":1,"Tags":"python,django,database-permissions,django-permissions","A_Id":7011483,"CreationDate":"2011-07-21T11:34:00.000","Title":"Django-guardian on DB with shared (non-exclusive) access","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm building a centralised django application that will be interacting with a dynamic number of databases with basically identical schema.  These dbs are also used by a couple legacy applications, some of which are in PHP.  Our solution to avoid multiple silos of db credentials is to store this info in generic setting files outside of the respective applications.  Setting files could be created, altered or deleted without the django application being restarted.\nFor every request to the django application, there will be a http header or a url parameter which can be used to deduce which setting file to look at to determine which database credentials to use.\nMy first thought is to use a custom django middleware that would parse the settings files (possibly with caching) and create a new connection object on each request, patching it into django.db before any ORM activity.\nIs there a more graceful method to handle this situation?  Are there any thread safety issues I should consider with the middleware approach?","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":1027,"Q_Id":6780827,"Users Score":2,"Answer":"rereading the file is a heavy penalty to pay when it's unlikely that the file has changed.\nMy usual approach is to use INotify to watch for configuration file changes, rather than trying to read a file on every request.  Additionally, I tend to keep a \"current\" configuration, parsed from the file, and only replace it with a new value once i've finished parsing the config file and i'm certain it's valid.  You could resolve some of your concerns about thread safety by setting the current configuration on each incoming request, so that the configuration can't change mid-way through a request.","Q_Score":1,"Tags":"python,django","A_Id":6782234,"CreationDate":"2011-07-21T18:26:00.000","Title":"Dynamic per-request database connections in Django","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm building a centralised django application that will be interacting with a dynamic number of databases with basically identical schema.  These dbs are also used by a couple legacy applications, some of which are in PHP.  Our solution to avoid multiple silos of db credentials is to store this info in generic setting files outside of the respective applications.  Setting files could be created, altered or deleted without the django application being restarted.\nFor every request to the django application, there will be a http header or a url parameter which can be used to deduce which setting file to look at to determine which database credentials to use.\nMy first thought is to use a custom django middleware that would parse the settings files (possibly with caching) and create a new connection object on each request, patching it into django.db before any ORM activity.\nIs there a more graceful method to handle this situation?  Are there any thread safety issues I should consider with the middleware approach?","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":1027,"Q_Id":6780827,"Users Score":0,"Answer":"You could start different instances with different settings.py files (by setting different DJANGO_SETTINGS_MODULE) on different ports, and redirect the requests to the specific apps. Just my 2 cents.","Q_Score":1,"Tags":"python,django","A_Id":6780942,"CreationDate":"2011-07-21T18:26:00.000","Title":"Dynamic per-request database connections in Django","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I use Windows 7 64 bit and Oracle 10g. I have installed python-2.7.2.amd64 and cx_Oracle-5.1-10g.win-amd64-py2.7.\nWhen I importing cx_Oracle module I get this error:\nTraceback (most recent call last):\n  File \"C:\\Osebno\\test.py\", line 1, in \n    import cx_oracle\nImportError: No module named cx_oracle\nCan someone please tell me what is wrong?","AnswerCount":5,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":17773,"Q_Id":6788937,"Users Score":0,"Answer":"It's not finding the module.\nThings to investigate: Do you have several python installations? Did it go to the right one? Do a global search for cx_oracle and see if it's in the correct place. Check your PYTHONPATH variable. Check Python's registry values HKLM\\Software\\Python\\Pyhoncore. Are they correct?","Q_Score":3,"Tags":"python,windows-7,oracle10g","A_Id":6788993,"CreationDate":"2011-07-22T10:51:00.000","Title":"Error when importing cx_Oracle module [Python]","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I use Windows 7 64 bit and Oracle 10g. I have installed python-2.7.2.amd64 and cx_Oracle-5.1-10g.win-amd64-py2.7.\nWhen I importing cx_Oracle module I get this error:\nTraceback (most recent call last):\n  File \"C:\\Osebno\\test.py\", line 1, in \n    import cx_oracle\nImportError: No module named cx_oracle\nCan someone please tell me what is wrong?","AnswerCount":5,"Available Count":3,"Score":0.1586485043,"is_accepted":false,"ViewCount":17773,"Q_Id":6788937,"Users Score":4,"Answer":"Have you tried import cx_Oracle (upper-case O) instead of import cx_oracle?","Q_Score":3,"Tags":"python,windows-7,oracle10g","A_Id":6789312,"CreationDate":"2011-07-22T10:51:00.000","Title":"Error when importing cx_Oracle module [Python]","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I use Windows 7 64 bit and Oracle 10g. I have installed python-2.7.2.amd64 and cx_Oracle-5.1-10g.win-amd64-py2.7.\nWhen I importing cx_Oracle module I get this error:\nTraceback (most recent call last):\n  File \"C:\\Osebno\\test.py\", line 1, in \n    import cx_oracle\nImportError: No module named cx_oracle\nCan someone please tell me what is wrong?","AnswerCount":5,"Available Count":3,"Score":0.0399786803,"is_accepted":false,"ViewCount":17773,"Q_Id":6788937,"Users Score":1,"Answer":"after installing the cx_Oracle download the instant client form oracle owth all DLLs , then copy then in the same directory of cx_Oracle.pyd , it will work directly\ntried and worked for me.","Q_Score":3,"Tags":"python,windows-7,oracle10g","A_Id":16885226,"CreationDate":"2011-07-22T10:51:00.000","Title":"Error when importing cx_Oracle module [Python]","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"The type of a field in a collection in my mongodb database is unicode string. This field currently does not have any data associated with it in any of the documents in the collection.\nI dont want the type to be string because,i want to add subfields to it from my python code using pymongo.\nThe collection already has many records in it.So, is it possible to change the type of the field to something like a dictionary in python for all the documents in the collection ?\nPlease Help\nThank You","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":1765,"Q_Id":6789562,"Users Score":1,"Answer":"Sure, simply create a script that iterates over your current collection, reads the existing value and overwrite it with the new value (an embedded document in your case). You change the typ of the field by simply setting a new value for that field. E.g. setting a string field to an integer field :\ndb.test.update({field:\"string\"}, {$set:{field:23}})","Q_Score":2,"Tags":"python,mongodb,pymongo","A_Id":6789704,"CreationDate":"2011-07-22T11:50:00.000","Title":"Changing the type of a field in a collection in a mongodb database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a rather complex Excel 2010 file that I automate using python and win32com.  For this I run windows in virtual box on an ubuntu machine.\nHowever, that same excel file solves\/runs fine on Ubuntu Maverick directly using wine 1.3.  Any hope of automating Excel on wine so I can drop the VM?\nOr is that just crazy talk (which I suspect).","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":2617,"Q_Id":6847684,"Users Score":3,"Answer":"You'd need a Windows version of Python, not a Linux version -- I'm saying you'd have to run Python under wine as well.\nHave you tried with just a normal Windows install of Python on wine? I don't see any reason why this wouldn't work.\nThere is are numerous pages in a Google search that show Windows Python (32-bit) working fine.","Q_Score":2,"Tags":"python,linux,excel,win32com,wine","A_Id":6847960,"CreationDate":"2011-07-27T16:10:00.000","Title":"automating excel with win32com on linux with wine","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":0},{"Question":"I have lots of data to operate on (write, sort, read). This data can potentially be larger than the main memory and doesn't need to be stored permanently.\nIs there any kind of library\/database that can store these data for me in memory and that does have and automagically fallback to disk if system runs in a OOM situation? The API and storage type is unimportant as long as it can store basic Python types (str, int, list, date and ideally dict).","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":105,"Q_Id":6942105,"Users Score":0,"Answer":"I will go for the in memory solution and let the OS swap. I can still replace the storage component if this will be really a problem. Thanks agf.","Q_Score":0,"Tags":"python","A_Id":7056331,"CreationDate":"2011-08-04T13:16:00.000","Title":"In memory database with fallback to disk on OOM","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a database and csv file that gets updated once a day. I managed to updated my table1 from this file by creating a separate log file with the record of the last insert.\nNo, I have to create a new table table2 where I keep calculations from the table1. \nMy issue is that those calculations are based on 10, 20 and 90 previous rows from table1. \nThe question is - how can I efficiently update table2 from the data of the table1 on a daily basis? I don't want to re-do the calculations everyday from the beginning of the table since it will be very time consuming for me.\nThanks for your help!","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":778,"Q_Id":6945953,"Users Score":0,"Answer":"The answer is \"as well as one could possibly expect.\"\nWithout seeing your tables, data, and queries, and the stats of your machine it is hard to be too specific.  However in general updates basically doing three steps.  This is a bit of an oversimplification but it allows you to estimate performance.\nFirst it selects the data necessary.  Then it marks the rows that were updated as deleted, then it inserts new rows with the new data into the table.  In general, your limit is usually the data selection.  As long as you can efficiently run the SELECT query to get the data you want, update should perform relatively well.","Q_Score":0,"Tags":"python,postgresql","A_Id":15492291,"CreationDate":"2011-08-04T17:33:00.000","Title":"Table updates using daily data from other tables Postgres\/Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I noticed that sqlite3 isn\u00b4t really capable nor reliable when i use it inside a multiprocessing enviroment. Each process tries to write some data into the same database, so that a connection is used by multiple threads. I tried it with the check_same_thread=False option, but the number of insertions is pretty random: Sometimes it includes everything, sometimes not. Should I parallel-process only parts of the function (fetching data from the web), stack their outputs into a list and put them into the table all together or is there a reliable way to handle multi-connections with sqlite?","AnswerCount":4,"Available Count":1,"Score":1.0,"is_accepted":false,"ViewCount":20258,"Q_Id":6969820,"Users Score":8,"Answer":"I've actually just been working on something very similar: \n\nmultiple processes (for me a processing pool of 4 to 32 workers)\neach process worker does some stuff that includes getting information\nfrom the web (a call to the Alchemy API for mine)\neach process opens its own sqlite3 connection, all to a single file, and each\nprocess adds one entry before getting the next task off the stack\n\nAt first I thought I was seeing the same issue as you, then I traced it to overlapping and conflicting issues with retrieving the information from the web. Since I was right there I did some torture testing on sqlite and multiprocessing and found I could run MANY process workers, all connecting and adding to the same sqlite file without coordination and it was rock solid when I was just putting in test data.\nSo now I'm looking at your phrase \"(fetching data from the web)\" - perhaps you could try replacing that data fetching with some dummy data to ensure that it is really the sqlite3 connection causing you problems. At least in my tested case (running right now in another window) I found that multiple processes were able to all add through their own connection without issues but your description exactly matches the problem I'm having when two processes step on each other while going for the web API (very odd error actually) and sometimes don't get the expected data, which of course leaves an empty slot in the database. My eventual solution was to detect this failure within each worker and retry the web API call when it happened (could have been more elegant, but this was for a personal hack).\nMy apologies if this doesn't apply to your case, without code it's hard to know what you're facing, but the description makes me wonder if you might widen your considerations.","Q_Score":8,"Tags":"python,sqlite,multiprocessing","A_Id":12809817,"CreationDate":"2011-08-07T00:05:00.000","Title":"SQLite3 and Multiprocessing","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm in the process of setting up a webserver from scratch, mainly for writing webapps with Python. On looking at alternatives to Apache+mod_wsgi, it appears that pypy plays very nicely indeed with pretty much everything I intend to use for my own apps. Not really having had a chance to play with PyPy properly, I feel this is a great opportunity to get to use it, since I don't need the server to be bulletproof. \nHowever, there are some PHP apps that I would like to run on the webserver for administrative purposes (PHPPgAdmin, for example). Is there an elegant solution that allows me to use PyPy within a PHP-compatible webserver like Apache? Or am I going to have to run CherryPy\/Paste or one of the other WSGI servers, with Apache and mod_wsgi on a separate port to provide administrative services?","AnswerCount":2,"Available Count":1,"Score":-0.0996679946,"is_accepted":false,"ViewCount":815,"Q_Id":6976578,"Users Score":-1,"Answer":"I know that mod_wsgi doesn't work with mod_php\nI heavily advise you, running PHP and Python applications on CGI level. \nPHP 5.x runs on CGI, for python there exists flup, that makes it possible to run WSGI Applications on CGI. \nTamer","Q_Score":5,"Tags":"php,python,apache,wsgi,pypy","A_Id":8920308,"CreationDate":"2011-08-07T23:41:00.000","Title":"PyPy + PHP on a single webserver","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm writing a Python script which uses a MySQL database, which is locally hosted. The program will be delivered as source code. As a result, the MySQL password will be visible to bare eyes. Is there a good way to protect this? \nThe idea is to prevent some naughty people from looking at the source code, gaining direct access to MySQL, and doing something ... well, naughty.","AnswerCount":4,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":14190,"Q_Id":6981064,"Users Score":16,"Answer":"Short answer\nYou can't.\nIf the password is stored in the artifact that's shipped to the end-user you must consider it compromised! Even if the artifact is a compiled binary, there are always (more or less complicated) ways to get at the password.\nThe only way to protect your resources is by exposing only a limited API to the end-user. Either build a programmatic API (REST, WS+SOAP, RMI, JavaEE+Servlets, ...) or only expose certain functionalities in your DB via SPROCs (see below).\nSome things first...\nThe question here should not be how to hide the password, but how to secure the database. Remember that passwords only are often a very weak protection and should not be considered the sole mechanism of protecting the DB. Are you using SSL? No? Well, then even if you manage to hide the password in the application code, it's still easy to sniff it on the network!\nYou have multiple options. All with varying degrees of security:\n\"Application Role\"\nCreate one database-user for the application. Apply authorization for this role. A very common setup is to only allow CRUD ops.\nPros\n\nvery easy to set-up\nPrevents DROP queries (f.ex. in SQL injections?)\n\nCons\n\nEverybody seeing the password has access to all the data in the database. Even if that data is normally hidden in the application.\nIf the password is compromised, the user can run UPDATE and DELETE queries without criteria (i.e.: delete\/update a whole table at once).\n\nAtomic auth&auth\nCreate one database user per application-\/end-user. This allows you to define atomic access rights even on a per-column basis. For example: User X can only select columns far and baz from table foo. And nothing else. But user Y can SELECT everything, but no updates, while user Z has full CRUD (select, insert, update, delete) access.\nSome databases allow you to reuse the OS-level credentials. This makes authentication to the user transparent (only needs to log-in to the workstation, that identity is then forwarded to the DB). This works easiest in a full MS-stack (OS=Windows, Auth=ActiveDirectory, DB=MSSQL) but is - as far as I am aware - also possible to achieve in other DBs.\nPros\n\nFairly easy to set up.\nVery atomic authorization scheme\n\nCons\n\nCan be tedious to set up all the access rights in the DB.\nUsers with UPDATE and DELETE rights can still accidentally (or intentionally?) delete\/update without criteria. You risk losing all the data in a table.\n\nStored Procedures with atomic auth&auth\nWrite no SQL queries in your application. Run everything through SPROCs. Then create db-accounts for each user and assign privileges to the SPROCs only.\nPros\n\nMost effective protection mechanism.\nSPROCs can force users to pass criteria to every query (including DELETE and UPDATE)\n\nCons\n\nnot sure if this works with MySQL (my knowledge in that area is flaky).\ncomplex development cycle: Everything you want to do, must first be defined in a SPROC.\n\nFinal thoughts\nYou should never allow database administrative tasks to the application. Most of the time, the only operations an application needs are SELECT, INSERT, DELETE and UPDATE. If you follow this guideline, there is hardly a risk involved by users discovering the password. Except the points mentioned above.\nIn any case, keep backups. I assume you want to project you database against accidental deletes or updates. But accidents happen... keep that in mind ;)","Q_Score":17,"Tags":"python,mysql","A_Id":6981725,"CreationDate":"2011-08-08T10:52:00.000","Title":"Safeguarding MySQL password when developing in Python?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm writing a Python script which uses a MySQL database, which is locally hosted. The program will be delivered as source code. As a result, the MySQL password will be visible to bare eyes. Is there a good way to protect this? \nThe idea is to prevent some naughty people from looking at the source code, gaining direct access to MySQL, and doing something ... well, naughty.","AnswerCount":4,"Available Count":2,"Score":-1.0,"is_accepted":false,"ViewCount":14190,"Q_Id":6981064,"Users Score":-5,"Answer":"Either use simple passwor like root.Else Don't use password.","Q_Score":17,"Tags":"python,mysql","A_Id":6981128,"CreationDate":"2011-08-08T10:52:00.000","Title":"Safeguarding MySQL password when developing in Python?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am trying to find a solution for a problem I am working on.  I have a python program which is is using a custom built sqlite3 install (which allows > 10 simultaneous connections) and in addition requires the use of Tix (which does not come as a stand install with the python package for the group I am distributing to.)  \nI want to know if there is a way to specify to distutils to use this certain sqlite3 build and include this third party install of Tix, such that I can distribute the file as an rpm and not require the end user to install Tix or modify their sqlite3 install... \nAny help is greatly appreciated!","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":115,"Q_Id":6986925,"Users Score":3,"Answer":"One possible solution: Create a custom package for that program containing the custom sqlite3\/etc. stuff and use relative imports to refer to those custom subpackages from a main module in your package, which you'd hook into with a simple importing script that would execute a your_package.run() function or something. You'd then use distutils to install your package in site-packages or whatever.","Q_Score":2,"Tags":"python,distutils","A_Id":6988101,"CreationDate":"2011-08-08T18:40:00.000","Title":"Packaging a Python Program with custom built libraries","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm looking for a way to debug queries as they are executed and I was wondering if there is a way to have MySQLdb print out the actual query that it runs, after it has finished inserting the parameters and all that?  From the documentation, it seems as if there is supposed to be a Cursor.info() call that will give information about the last query run, but this does not exist on my version (1.2.2).\nThis seems like an obvious question, but for all my searching I haven't been able to find the answer.  Thanks in advance.","AnswerCount":10,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":67798,"Q_Id":7071166,"Users Score":126,"Answer":"We found an attribute on the cursor object called\u00a0cursor._last_executed that holds the last query string to run even when an exception occurs.  This was easier and better for us in production than using profiling all the time or MySQL query logging as both of those have a performance impact and involve more code or more correlating separate log files, etc.\nHate to answer my own question but this is working better for us.","Q_Score":82,"Tags":"python,mysql,mysql-python","A_Id":7190914,"CreationDate":"2011-08-15T21:43:00.000","Title":"Print the actual query MySQLdb runs?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Is this possible? Generation of Excel combobox in a cell using xlwt or similar module?\nWhen I load the xls using xlrd, then copy and save it using xlwt, the combobox from original xls is lost.","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":597,"Q_Id":7094771,"Users Score":1,"Answer":"No, it's not possible. xlrd doesn't pick up the combo box and suchlike.","Q_Score":2,"Tags":"python,excel,combobox,xlwt,xlrd","A_Id":7266184,"CreationDate":"2011-08-17T14:45:00.000","Title":"Excel Combobox in Python xlwt module","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm implementing a voting system for a relatively large website and I'm wondering where should I store the vote count. The main problem is that storing them in the main database would put a lot of strain on it, as MySQL isn't very good at handing lots and lots of simple queries. \nMy best option so far is to use memcached as it seems perfect for this task (very fast and key\/value oriented). The only problem with this solution is that memcached is non-persistent and there is no easy way of saving these values.\nIs there something that is specifically designed for this task, preferably with a Python back end?","AnswerCount":6,"Available Count":4,"Score":1.2,"is_accepted":true,"ViewCount":145,"Q_Id":7112347,"Users Score":2,"Answer":"Can you accept some degree of vote loss? If so, you can do a hybrid solution. Every modulo 100 (10, something), update the SQL database with the current memcache value. You can also have a periodic script scan and update if required.","Q_Score":3,"Tags":"python,memcached,voting","A_Id":7112410,"CreationDate":"2011-08-18T18:33:00.000","Title":"Best way of storing incremental numbers?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm implementing a voting system for a relatively large website and I'm wondering where should I store the vote count. The main problem is that storing them in the main database would put a lot of strain on it, as MySQL isn't very good at handing lots and lots of simple queries. \nMy best option so far is to use memcached as it seems perfect for this task (very fast and key\/value oriented). The only problem with this solution is that memcached is non-persistent and there is no easy way of saving these values.\nIs there something that is specifically designed for this task, preferably with a Python back end?","AnswerCount":6,"Available Count":4,"Score":0.0,"is_accepted":false,"ViewCount":145,"Q_Id":7112347,"Users Score":0,"Answer":"Mongodb can work well.Since it can be faster or Google App Engine was designed to scale.","Q_Score":3,"Tags":"python,memcached,voting","A_Id":7112511,"CreationDate":"2011-08-18T18:33:00.000","Title":"Best way of storing incremental numbers?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm implementing a voting system for a relatively large website and I'm wondering where should I store the vote count. The main problem is that storing them in the main database would put a lot of strain on it, as MySQL isn't very good at handing lots and lots of simple queries. \nMy best option so far is to use memcached as it seems perfect for this task (very fast and key\/value oriented). The only problem with this solution is that memcached is non-persistent and there is no easy way of saving these values.\nIs there something that is specifically designed for this task, preferably with a Python back end?","AnswerCount":6,"Available Count":4,"Score":0.0665680765,"is_accepted":false,"ViewCount":145,"Q_Id":7112347,"Users Score":2,"Answer":"MySQL isn't very good at handing lots and lots of simple queries\n\nYou may have something drastically misconfigured in your MySQL server. MySQL should easily be able to handle 4000 queries per minute. There are benchmarks of MySQL handling over 25k INSERTs per second.","Q_Score":3,"Tags":"python,memcached,voting","A_Id":7112669,"CreationDate":"2011-08-18T18:33:00.000","Title":"Best way of storing incremental numbers?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm implementing a voting system for a relatively large website and I'm wondering where should I store the vote count. The main problem is that storing them in the main database would put a lot of strain on it, as MySQL isn't very good at handing lots and lots of simple queries. \nMy best option so far is to use memcached as it seems perfect for this task (very fast and key\/value oriented). The only problem with this solution is that memcached is non-persistent and there is no easy way of saving these values.\nIs there something that is specifically designed for this task, preferably with a Python back end?","AnswerCount":6,"Available Count":4,"Score":0.0,"is_accepted":false,"ViewCount":145,"Q_Id":7112347,"Users Score":0,"Answer":"If you like memcached but don't like the fact that it doesn't persist data then you should consider using Membase. Membase is basically memcached with sqlite as the persistence layer. It is very easy to set up and supports the memcached protocol so if you already have memcached set up you can use Membase as a drop in replacement.","Q_Score":3,"Tags":"python,memcached,voting","A_Id":7116659,"CreationDate":"2011-08-18T18:33:00.000","Title":"Best way of storing incremental numbers?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I looked through several SO-Questions for how to pickle a python object and store it into a database. The information I collected is:\n\nimport pickle or import cpickle. Import the latter, if performance is an issue.\nAssume dict is a python dictionary (or what so ever python object): pickled = pickle.dumps(dict).\nstore pickled into a MySQL BLOB Column using what so ever module to communicate with Database.\nGet it out again. And use pickle.loads(pickled) to restore the python dictionary.\n\nI just want to make sure I understood this right. Did I miss something critical? Are there sideeffects? Is it really that easy?\nBackground-Info: The only thing I want to do, is store Googlegeocoder-Responses, which are nested python dictionarys in my case. I am only using a little part of the response object and I don't know if I will ever need more of it later on. That's why I thought of storing the response to save me repetition of some million querys.","AnswerCount":3,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":5063,"Q_Id":7117525,"Users Score":2,"Answer":"It's really that easy... so long as you don't need your DB to know anything about the dictionary.  If you need any sort of structured data access to the contents of the dictionary, then you're going to have to get more involved.\nAnother gotcha might be what you intend to put in the dict.  Python's pickle serialization is quite intelligent and can handle most cases without any need for adding custom support.  However, when it doesn't work, it can be very difficult to understand what's gone wrong.  So if you can, restrict the contents of the dict to Python's built-in types.  If you start adding instances of custom classes, keep them to simple custom classes that don't do any funny stuff with attribute storage or access.  And beware of adding instances of classes or types from add-ons.  In general, if you start running into hard-to-understand problems with the pickling or unpickling, look at the non-built-in types in the dict.","Q_Score":7,"Tags":"python,mysql,pickle","A_Id":7117674,"CreationDate":"2011-08-19T05:59:00.000","Title":"How to Pickle a python dictionary into MySQL?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm trying to get a django site deployed from a repository. I was almost there, and then changed something (I'm not sure what!!) and was back to square one.\nNow I'm trying to run .\/manage.py syncdb and get the following error:\n\ndjango.core.exceptions.ImproperlyConfigured: Error loading MySQLdb module: this is MySQLdb version (1, 2, 3, 'final', 0), but _mysql is version (1, 2, 2, 'final', 0)\n\nI've searched forums for hours and none of the solutions presented helped. I tried uninstalling and re-installing MySQL-python and upgrading it. I get the same error when trying to import it from the python command line interpreter.\nDoes anyone have any suggestions?","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":4064,"Q_Id":7137214,"Users Score":1,"Answer":"For those who come upon this question: \nIt turns out that ubuntu _mysql version was different from the one in my venv. Uninstalling that and re-installing in my venv did the trick.","Q_Score":6,"Tags":"mysql,django,deployment,ubuntu,mysql-python","A_Id":7352188,"CreationDate":"2011-08-21T08:27:00.000","Title":"Django MySQLdb version doesn't match _mysql version Ubuntu","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"i'm trying to build a web server using apache as the http server, mod_wsgi + python as the logic handler, the server was supposed to handler long request without returning, meaning i want to keep writing stuff into this request.\nthe problem is, when the link is broken, the socket is in a CLOSE_WAIT status, apache will NOT notify my python program, which means, i have to write something to get an exception, says the link is broken, but those messages were lost and can't be restored.\ni tried to get the socket status before writing through \/proc\/net\/tcp, but it could not prevent a quick connect\/break connection.\nanybody has any ideas, please help, very much thanks in advance!","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":393,"Q_Id":7144011,"Users Score":1,"Answer":"You cant. It is a limitation of the API defined by the WSGI specification. So, nothing to do with Apache or mod_wsgi really as you will have the same issue with any WSGI server if you follow the WSGI specification.\nIf you search through the mod_wsgi mailing list on Google Groups you will find a number of discussions about this sort of problem in the past.","Q_Score":0,"Tags":"python,apache,webserver,mod-wsgi","A_Id":7145199,"CreationDate":"2011-08-22T06:52:00.000","Title":"apache server with mod_wsgi + python as backend, how can i be able to notified my connection status?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am currently working on two projects in python. One need python 2.5 and other 2.7.\nNow the problem is when I installed mysql python for 2.5 it required 32 bit version of mysql and it  was not working with 64 bit version. So I installed 32 bit version. This project is done by using virtualenv.\nNow I need to run it on 2.7 and it wants 64 bit version of mysql.\nI cannot reinstall mysql as old project is still on.\nIs it possible to  install both bit versions of mysql in my Snow Leopard 10.6? If possible then how?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":235,"Q_Id":7158929,"Users Score":0,"Answer":"It is possible but you'll need to to compile them by hand, start by creating separate folders for them to live in, then get the source and dependencies that they'll need and keep them separate, you'll need to alter the .\/configure commands to point them to the correct places and they should build fine.","Q_Score":0,"Tags":"mysql,osx-snow-leopard,32bit-64bit,mysql-python,python-2.5","A_Id":7159017,"CreationDate":"2011-08-23T09:34:00.000","Title":"Install both 32 bit and 64 bit versions of mysql on a same mac machine","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"Okay, so I'm connected to an oracle database in python 2.7 and cx_Oracle 5.1 compiled against the instant client 11.2. I've got a cursor to the database and running SQL is not an issue, except this:\n\n\n    cursor.execute('ALTER TRIGGER :schema_trigger_name DISABLE',\n                     schema_trigger_name='test.test_trigger')\n\n\nor\n\n\n    cursor.prepare('ALTER TRIGGER :schema_trigger_name DISABLE')\n    cursor.execute(None,{'schema_trigger_name': 'test.test_trigger'})\n\n\nboth result in an error from oracle:\n\n\n    Traceback (most recent call last):\n      File \"connect.py\", line 257, in \n        cursor.execute('ALTER TRIGGER :schema_trigger_name DISABLE',\n                    schema_trigger_name='test.test_trigger')\n    cx_Oracle.DatabaseError: ORA-01036: illegal variable name\/number\n\n\nWhile running:\n\n\n    cursor.execute('ALTER TRIGGER test.test_trigger DISABLE')\n\n\nworks perfectly. What's the issue with binding that variable?","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1300,"Q_Id":7174741,"Users Score":0,"Answer":"You normally can't bind an object name in Oracle. For variables it'll work but not for trigger_names, table_names etc.","Q_Score":1,"Tags":"python,oracle,cx-oracle","A_Id":7174814,"CreationDate":"2011-08-24T11:32:00.000","Title":"Exception binding variables with cx_Oracle in python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"As a personal project, I have been developing my own database software in C#. Many current database systems can use SQL commands for queries. Is there anyone here that could point me in the right direction of implementing such a system in a database software written completely from scratch? For example a user familiar with SQL could enter a statement as a string into an application, that statement will be analyzed by my application and the proper query will be run. Does anyone have any experience with something like that here? This is probably a very unusual questions haha. Basically what I am asking, are there any tools available out there that can dissect SQL statements or will I have to write my own from scratch for that?\nThanks in advance for any help!\n(I may transfer some of my stuff to Python and Java, so any potential answers need not be limited to C#)\nALSO: I am not using any current SQL database or anything like that, my system is completely from scratch, I hope my question makes sense. Basically I want my application to be able to interface with programs that send SQL commands.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":2117,"Q_Id":7211204,"Users Score":3,"Answer":"A full-on database engine is a pretty serious undertaking.  You're not going to sit down and have a complete engine next week, so I'd have thought you would want to write the SQL parser piecemeal: adding features to the parser as the features are supported in the engine.\nI'm guessing this is just something fun to do, rather than something you want working ASAP.  Given that, I'd have thought writing an SQL parser is one of the best bits of the project!  I've done lots of work with flat file database engines, because the response times required for queries don't allow a RDBMS.  One of the most enjoyable bits has been adding support for SQL fragments in e.g. the UI, where response time isn't quite as vital.\nThe implementation I work on is plain old C, but in fact from what I've seen, most relational databases are still written primarily in C.  And there is something satisfying about writing these things in a really low level language :)","Q_Score":1,"Tags":"c#,java,python,sql,database","A_Id":7211297,"CreationDate":"2011-08-26T22:36:00.000","Title":"C# custom database engine, how to implement SQL","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Im trying to pull only one column from a datastore table\nI have a Books model with\nid, key, title, author, isbn and price\neverything = db.GqlQuery('SELECT * FROM Books') gives me everything, but say i only want the title\nbooks = db.GqlQuery('SELECT title FROM Books')\nIve tried everything people have suggested but nothing seems to work\nAny help is much appreciated \nThanks","AnswerCount":2,"Available Count":1,"Score":0.2913126125,"is_accepted":false,"ViewCount":1553,"Q_Id":7213991,"Users Score":3,"Answer":"You can't. GQL is not SQL, and the datastore is not a relational database. An entity is stored as a single serialized protocol buffer, and it's impossible to fetch part of an entity; the whole thing needs to be deserialized.","Q_Score":2,"Tags":"python,google-app-engine,gql,gqlquery","A_Id":7214401,"CreationDate":"2011-08-27T10:36:00.000","Title":"Google App Engine python, GQL, select only one column from datastore","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am relatively new to SQLalchemy and have done basic database creation, insert, update and delete. I have found it quite simple to use so far. My question is:\nI want to move records from one database to another backup database. What is the simplest way to do this in SQLalchemy?","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1472,"Q_Id":7216100,"Users Score":0,"Answer":"You would just go direct to the database utiltites and back it up there. Nothing to do with SQLAlchemy","Q_Score":2,"Tags":"python,sqlalchemy","A_Id":7216293,"CreationDate":"2011-08-27T17:17:00.000","Title":"What is the easiest way to move data from one database to another backup database using SQLalchemy?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am dealing with an application with huge SQL queries. They are so complex that when I finish understanding one I have already forgotten how it all started.\nI was wondering if it will be a good practice to pull more data from database and make the final query in my code, let's say, with Python. Am I nuts? Would it be that bad for performance?\nNote, results are huge too, I am talking about an ERP in production developed by other people.","AnswerCount":5,"Available Count":3,"Score":1.0,"is_accepted":false,"ViewCount":3111,"Q_Id":7279761,"Users Score":7,"Answer":"Let the DB figure out how best to retrieve the information that you want, else you'll have to duplicate the functionality of the RDBMS in your code, and that will be way more complex than your SQL queries. \nPlus, you'll waste time transferring all that unneeded information from the DB to your app, so that you can filter and process it in code.\nAll this is true because you say you're dealing with large data.","Q_Score":9,"Tags":"python,sql,performance","A_Id":7279821,"CreationDate":"2011-09-02T06:05:00.000","Title":"Should I use complex SQL queries or process results in the application?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am dealing with an application with huge SQL queries. They are so complex that when I finish understanding one I have already forgotten how it all started.\nI was wondering if it will be a good practice to pull more data from database and make the final query in my code, let's say, with Python. Am I nuts? Would it be that bad for performance?\nNote, results are huge too, I am talking about an ERP in production developed by other people.","AnswerCount":5,"Available Count":3,"Score":1.2,"is_accepted":true,"ViewCount":3111,"Q_Id":7279761,"Users Score":3,"Answer":"I would have the business logic in the application, as much as possible. Complex business logic in queries are difficult to maintain. (when I finish understanding one I have already forgotten how it all started)Complex logic in stored procedures are ok. But with a typical python application, you would want your business logic to be in python.\nNow, the database is way better in handling data than your application code. So if your logic involves huge amount of data, you may get better performance with the logic in the database. But this will be for complex reports, bookkeeping operations and such, that operate on a large volume of data. You may want to use stored procedures, or systems that specialize in such operations (a data warehouse for reports) for these types of operations.\nNormal OLTP operations do not involve much of data. The database may be huge, but the data required for a typical transaction will be (typically) a very small part of it. Querying this in a large database may cause performance issues, but you can optimize this in several ways (indexes, full text searches, redundancy, summary tables... depends on your actual problem).\nEvery rule has exceptions, but as a general guideline, try to have your business logic in your application code. Stored procedures for complex logic. A separate data warehouse or a set of procedures for reporting.","Q_Score":9,"Tags":"python,sql,performance","A_Id":7280826,"CreationDate":"2011-09-02T06:05:00.000","Title":"Should I use complex SQL queries or process results in the application?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am dealing with an application with huge SQL queries. They are so complex that when I finish understanding one I have already forgotten how it all started.\nI was wondering if it will be a good practice to pull more data from database and make the final query in my code, let's say, with Python. Am I nuts? Would it be that bad for performance?\nNote, results are huge too, I am talking about an ERP in production developed by other people.","AnswerCount":5,"Available Count":3,"Score":0.0399786803,"is_accepted":false,"ViewCount":3111,"Q_Id":7279761,"Users Score":1,"Answer":"@Nivas is generally correct.\nThese are pretty common patterns\n\nDivision of labour - the DBAs have to return all the data the business need, but they only have a database to work with.  The developers could work with the DBAs to do it better but departmental responsbilities make it nearly impossible.  So SQL to do morethan retrieve data is used.\nlack of smaller functions.  Could the massive query be broken down into smaller stages, using working tables?  Yes, but I have known environments where a new table needs reams of approavals - a heavy Query is just written\n\nSo, in general, getting data out of the database - thats down to the database.  But if a SQL query is too long its going to be hard for the RDBMS to optimise, and it probably means the query is spanning data, business logic and even presentation in one go.\nI would suggest a saner approach is usually to seperate out the \"get me the data\" portions into stored procedures or other controllable queries that populate staging tables.  Then the business logic can be written into a scripting language sitting above and controlling the stored procedures.  And presentation is left elsewhere.  In essence solutions like cognos try to do this anyway.\nBut if you are looking at an ERP in production, the constraints and the solutions above probably already exist - are you talking to the right people?","Q_Score":9,"Tags":"python,sql,performance","A_Id":7282367,"CreationDate":"2011-09-02T06:05:00.000","Title":"Should I use complex SQL queries or process results in the application?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"My python application is dying, this oracle trace file is being generated. I am using cx_Oracle, how do I go about using this trace file to resolve this crash?\nora_18225_139690296567552.trc\nkpedbg_dmp_stack()+360<-kpeDbgCrash()+192<-kpureq2()+3194<-OCIStmtPrepare2()+157<-Cursor_InternalPrepare()+298<-0000000000EA3010<-0000000000EA3010<-0000000000EA3010<-0000000000EA3010<-0000000000EA3010<-0000000000EA3010<-0000000000EA3010<-0000000000EA3010<-0000000000EA3010<-0000000000EA3010<-0000000000EA3010<-0000000000EA3010<-0000000000EA3010<-0000000000EA3010<-0000000000EA3010<-0000000000EA3010","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":653,"Q_Id":7285135,"Users Score":0,"Answer":"Do you have an Oracle support contract?  If I would file an SR and upload the trace to Oracle and have them tell you what it is complaining about.  Those code calls are deep in their codebase from the looks of it.","Q_Score":1,"Tags":"python,cx-oracle","A_Id":7530424,"CreationDate":"2011-09-02T14:43:00.000","Title":"I have an Oracle Stack trace file Python cx_Oracle","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"In a regular application (like on Windows), when objects\/variables are created on a global level it is available to the entire program during the entire duration the program is running.\nIn a web application written in PHP for instance, all variables\/objects are destroyed at the end of the script so everything has to be written to the database.\na) So what about python running under apache\/modwsgi? How does that work in regards to the memory? \nb) How do you create objects that persist between web page requests and how do you ensure there isn't threading issues in apache\/modwsgi?","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":193,"Q_Id":7293290,"Users Score":0,"Answer":"All Python globals are created when the module is imported. When module is re-imported the same globals are used.\nPython web servers do not do threading, but pre-forked processes. Thus there is no threading issues with Apache.\nThe lifecycle of Python processes under Apache depends. Apache has settings how many child processes are spawned, keep in reserve and killed. This means that you can use globals in Python processes for caching (in-process cache), but the process may terminate after any request so you cannot put any persistent data in the globals. But the process does not necessarily need to terminate and in this regard Python is much more efficient than PHP (the source code is not parsed for every request - but you need to have the server in reload mode to read source code changes during the development).\nSince globals are per-process and there can be N processes, the processes share \"web server global\" state using mechanisms like memcached.\nUsually Python globals only contain\n\nSetting variables set during the process initialization\nCached data (session\/user neutral)","Q_Score":4,"Tags":"python,apache,memory-management,mod-wsgi","A_Id":7293404,"CreationDate":"2011-09-03T13:09:00.000","Title":"Memory model for apache\/modwsgi application in python?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a single table in an Sqlite DB, with many rows. I need to get the number of rows (total count of items in the table).\nI tried select count(*) from table, but that seems to access each row and is super slow.\nI also tried select max(rowid) from table. That's fast, but not really safe -- ids can be re-used, table can be empty etc. It's more of a hack.\nAny ideas on how to find the table size quickly and cleanly?\n\nUsing Python 2.5's sqlite3 version 2.3.2, which uses Sqlite engine 3.4.0.","AnswerCount":3,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":3251,"Q_Id":7346079,"Users Score":0,"Answer":"To follow up on Thilo's answer, as a data point, I have a sqlite table with 2.3 million rows. Using select count(*) from table, it took over 3 seconds to count the rows. I also tried using SELECT rowid FROM table, (thinking that rowid is a default primary indexed key) but that was no faster. Then I made an index on one of the fields in the database (just an arbitrary field, but I chose an integer field because I knew from past experience that indexes on short fields can be very fast, I think because the index is stored a copy of the value in the index itself). SELECT my_short_field FROM table brought the time down to less than a second.","Q_Score":2,"Tags":"python,sqlite","A_Id":34628302,"CreationDate":"2011-09-08T09:44:00.000","Title":"Fast number of rows in Sqlite","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a single table in an Sqlite DB, with many rows. I need to get the number of rows (total count of items in the table).\nI tried select count(*) from table, but that seems to access each row and is super slow.\nI also tried select max(rowid) from table. That's fast, but not really safe -- ids can be re-used, table can be empty etc. It's more of a hack.\nAny ideas on how to find the table size quickly and cleanly?\n\nUsing Python 2.5's sqlite3 version 2.3.2, which uses Sqlite engine 3.4.0.","AnswerCount":3,"Available Count":3,"Score":0.0665680765,"is_accepted":false,"ViewCount":3251,"Q_Id":7346079,"Users Score":1,"Answer":"Do you have any kind of index on a not-null column (for example a primary key)? If yes, the index can be scanned (which hopefully does not take that long). If not, a full table scan is the only way to count all rows.","Q_Score":2,"Tags":"python,sqlite","A_Id":7346136,"CreationDate":"2011-09-08T09:44:00.000","Title":"Fast number of rows in Sqlite","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a single table in an Sqlite DB, with many rows. I need to get the number of rows (total count of items in the table).\nI tried select count(*) from table, but that seems to access each row and is super slow.\nI also tried select max(rowid) from table. That's fast, but not really safe -- ids can be re-used, table can be empty etc. It's more of a hack.\nAny ideas on how to find the table size quickly and cleanly?\n\nUsing Python 2.5's sqlite3 version 2.3.2, which uses Sqlite engine 3.4.0.","AnswerCount":3,"Available Count":3,"Score":0.0665680765,"is_accepted":false,"ViewCount":3251,"Q_Id":7346079,"Users Score":1,"Answer":"Other way to get the rows number of a table is by using a trigger that stores the actual number of rows in other table (each insert operation will increment a counter). \nIn this way inserting a new record will be a little slower, but you can immediately get the number of rows.","Q_Score":2,"Tags":"python,sqlite","A_Id":7346821,"CreationDate":"2011-09-08T09:44:00.000","Title":"Fast number of rows in Sqlite","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm migrating a GAE\/Java app to Python (non-GAE) due new pricing, so I'm getting a little server and I would like to find a database that fits the following requirements:\n\nLow memory usage (or to be tuneable or predictible)\nFastest querying capability for simple document\/tree-like data identified by key (I don't care about performance on writing and I assume it will have indexes)\nBindings with Pypy 1.6 compatibility (or Python 2.7 at least)\n\nMy data goes something like this:\n\nId: short key string\nTitle\nCreators: an array of another data structure which has an id - used as key -, a name, a site address, etc.\nTags: array of tags. Each of them can has multiple parent tags, a name, an id too, etc.\nLicense: a data structure which describes its license (CC, GPL, ... you say it) with name, associated URL, etc.\nAddition time: when it was add in our site.\nTranslations: pointers to other entries that are translations of one creation.\n\nMy queries are very simple. Usual cases are:\n\nFilter by tag ordered by addition time.\nSelect a few (pagination) ordered by addition time.\n(Maybe, not done already) filter by creator.\n(Not done but planned) some autocomplete features in forms, so I'm going to need search if some fields contains a substring ('LIKE' queries).\n\nThe data volume is not big. Right now I have about 50MB of data but I'm planning to have a huge dataset around 10GB.\nAlso, I want to rebuild this from scratch, so I'm open to any option. What database do you think can meet my requirements?\nEdit: I want to do some benchmarks around different options and share the results. I have selected, so far, MongoDB, PostgreSQL, MySQL, Drizzle, Riak and Kyoto Cabinet.","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":830,"Q_Id":7375415,"Users Score":1,"Answer":"I would recommend Postresql, only because it does what you want, can scale, is fast, rather easy to work with and stable.\nIt is exceptionally fast at the example queries given, and could be even faster with document querying.","Q_Score":3,"Tags":"python,database,nosql,rdbms","A_Id":7377444,"CreationDate":"2011-09-10T23:49:00.000","Title":"Low memory and fastest querying database for a Python project","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am using Psycopg2 with PostgreSQL 8.4. While reading from a huge table, I suddenly get this cryptic error at the following line of code, after this same line of code has successfully fetched a few hundred thousand rows.\nsomerows = cursorToFetchData.fetchmany(30000)\npsycopg2.DataError: invalid value \"L\u00c3\" for \"DD\"\nDETAIL:  Value must be an integer.\nMy problem is that I have no column named \"DD\", and about 300 columns in that table (I know 300 columns is a design flaw). I would appreciate a hint about the meaning of this error message, or how to figure out where the problem lies. I do not understand how Psycop2 can have any requirements about the datatype while fetching rows.","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":176,"Q_Id":7375572,"Users Score":2,"Answer":"Can you paste in the data from the row that's causing the problem? At a guess I'd say it's a badly formatted date entry, but hard to say.\n(Can't comment, so has to be in a answer...)","Q_Score":0,"Tags":"python,postgresql,psycopg2","A_Id":7378101,"CreationDate":"2011-09-11T00:33:00.000","Title":"Cryptic Psycopg2 error message","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am using Psycopg2 with PostgreSQL 8.4. While reading from a huge table, I suddenly get this cryptic error at the following line of code, after this same line of code has successfully fetched a few hundred thousand rows.\nsomerows = cursorToFetchData.fetchmany(30000)\npsycopg2.DataError: invalid value \"L\u00c3\" for \"DD\"\nDETAIL:  Value must be an integer.\nMy problem is that I have no column named \"DD\", and about 300 columns in that table (I know 300 columns is a design flaw). I would appreciate a hint about the meaning of this error message, or how to figure out where the problem lies. I do not understand how Psycop2 can have any requirements about the datatype while fetching rows.","AnswerCount":2,"Available Count":2,"Score":0.0996679946,"is_accepted":false,"ViewCount":176,"Q_Id":7375572,"Users Score":1,"Answer":"This is not a psycopg error, it is a postgres error.\nAfter the error is raised, take a look at cur.query to see the query generated. Copy and paste it into psql and you'll see the same error. Then debug it from there.","Q_Score":0,"Tags":"python,postgresql,psycopg2","A_Id":40247155,"CreationDate":"2011-09-11T00:33:00.000","Title":"Cryptic Psycopg2 error message","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a large amount of data that I am pulling from an xml file that all needs to be validated against each other (in excess of 500,000 records). It is location data, so it has information such as: county, street prefix, street suffix, street name, starting house number, ending number. There are duplicates, house number overlaps, etc. and I need to report on all this data (such as where there are issues). Also, there is no ordering of the data within the xml file, so each record needs to be matched up against all others. \nRight now I'm creating a dictionary of the location based on the street name info, and then storing a list of the house number starting and ending locations. After all this is done, I'm iterating through the massive data structure that was created to find duplicates and overlaps within each list. I am running into problems with the size of the data structure and how many errors are coming up.\nOne solution that was suggested to me was to create a temporary SQLite DB to hold all data as it is read from the file, then run through the DB to find all issues with the data, report them out, and then destroy the DB. Is there a better\/more efficient way to do this? And any suggestions on a better way to approach this problem?\nAs an fyi, the xml file I'm reading in is over 500MB (stores other data than just this street information, although that is the bulk of it), but the processing of the file is not where I'm running into problems, it's only when processing the data obtained from the file.\nEDIT: I could go into more detail, but the poster who mentioned that there was plenty of room in memory for the data was actually correct, although in one case I did have to run this against 3.5 million records, in that instance I did need to create a temporary database.","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1110,"Q_Id":7391148,"Users Score":0,"Answer":"Unless this data has already been sanitised against the PAF (UK Post office Address file - every address in UK basically) then you will have addresses in there that are the same actual house, but spelt differently, wrong postcode, postcode in wrong field etc.  This will completely change your approach.\nCheck out if this is sanitised before you start.  The person giving it to you will either say \"yes of course it has and I did it\" or they will look blankly - in which case no.\nIf it is sanitised, great, probably an external agency is supplying your data and they probably can do this for you, but I expect oyu are being asked because its cheaper.  Get on.\nIf not, you have a range of problems and need to talk with your boss about what they want, how confidnet they want to be of matches etc.\nIn general the idea is to come up with a number of match algorithms per field, that output a confidence value that the two address under compare are the same.  Then a certain number of these values are weighted, and a total confidnece value has to be passed to consider the two addresses a match\nBut I am not clear this is your problem, but I do suggest you check what your boss exactly wants - this is not a clearly understood area between marketing and technical depats.","Q_Score":0,"Tags":"python,xml,sanitization","A_Id":7392402,"CreationDate":"2011-09-12T16:40:00.000","Title":"Large temporary database to sanitize data in Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Well, I might be doing some work in Python that would end up with hundreds of thousands, maybe millions of rows of data, each with entries in maybe 50 or more columns.  I want a way to keep track of this data and work with it.  Since I also want to learn Microsoft Access, I suggest putting the data in there.  Is there any easy way to do this?  I also want to learn SAS, so that would be fine too.  Or, is there some other program\/method I should know for such a situation?\nThanks for any help!","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":323,"Q_Id":7410458,"Users Score":1,"Answer":"Yes, you can talk to any ODBC database from Python, and that should include Access.   You'll want the \"windows\" version of Python (which includes stuff like ODBC) from ActiveState.\nI'd be more worried about the \"millions of rows\" in Access, it can get a bit slow on retrieval if you're actually using it for relational tasks (that is, JOINing different tables together).\nI'd also take a look at your 50 column tables \u2014 sometimes you need 50 columns but more often it means you haven't decomposed your data sufficiently to get it in normal form.\nFinally, if you use Python to read and write an Access database I don't know if I'd count that as \"learning Access\".  Really learning Access would be using the front end to create and maintain the database, creating forms and reports in Access (which would not be available from Python) and programming in Visual Basic for Applications (VBA).\nI really like SQLite as an embedded database solution, especially from Python, and its SQL dialect is probably \"purer\" than Access's.","Q_Score":1,"Tags":"python,database,ms-access","A_Id":7410499,"CreationDate":"2011-09-14T01:56:00.000","Title":"Is it possible to store data from Python in Access file?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm working on an application where a user can search for items near his location.\nWhen a user registers for my service, their long\/lat coordinates are taken (this is actually grabbed from a zip\/postcode and then gets looked up via Google for the long\/lats). This also happens when a user adds an item, they are asked for the zip\/postcode of the item, and that is converted to the long\/lat.\nMy question is how would i run a query using MySQL that would search within, say 20 miles, from the user's location and get all the items within that 20 mile radius?","AnswerCount":6,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":4012,"Q_Id":7413619,"Users Score":0,"Answer":"To be performant, you don't want to do a complete scan through the database and compute distances for each row, you want conditions that can be indexed. The simplest way to do this is to compute a box with a minimum\/maximum latitude and minimum\/maximum longitude, and use BETWEEN to exclude everything outside of those ranges. Since you're only dealing with US locations (zip code based), you won't have to worry about the transition between +180 and -180 degrees.\nThe only remaining problem is to compute the bounds of the box in lat\/long when your conditions are in miles. You need to convert miles to degrees. For latitude this is easy, just divide 360 degrees by the circumference of the earth and multiply by 20; 0.289625 degrees. Longitude is tougher because it varies by latitude, the circumference is roughly cosine(latitude)*24901.461; 20 miles is 20*360\/(cos(latitude)*24901.461).","Q_Score":3,"Tags":"python,mysql,geolocation,latitude-longitude","A_Id":7420726,"CreationDate":"2011-09-14T08:49:00.000","Title":"Find long\/lat's within 20 miles of user's long\/lat","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have an application that needs to interface with another app's database. I have read access but not write.\nCurrently I'm using sql statements via pyodbc to grab the rows and using python manipulate the data. Since I don't cache anything this can be quite costly.\nI'm thinking of using an ORM to solve my problem. The question is if I use an ORM like \"sql alchemy\" would it be smart enough to pick up changes in the other database?\nE.g. sql alchemy accesses a table and retrieves a row. If that row got modified outside of sql alchemy would it be smart enough to pick it up?\n~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\nEdit: To be more clear\nI have one application that is simply a reporting tool lets call App A.\nI have another application that handles various financial transactions called App B.\nA has access to B's database to retrieve the transactions and generates various reports. There's hundreds of thousands of transactions. We're currently caching this info manually in python, if we need an updated report we refresh the cache. If we get rid of the cache, the sql queries combined with the calculations becomes unscalable.","AnswerCount":1,"Available Count":1,"Score":0.3799489623,"is_accepted":false,"ViewCount":122,"Q_Id":7426564,"Users Score":2,"Answer":"I don't think an ORM is the solution to your problem of performance. By default ORMs tend to be less efficient than row SQL because they might fetch data that you're not going to use (eg. doing a SELECT * when you need only one field), although SQLAlchemy allows fine-grained control over the SQL generated.\nNow to implement a caching mechanism, depending on your application, you could use a simple dictionary in memory or a specialized system such as memcached or Redis.\nTo keep your cached data relatively fresh, you can poll the source at regular intervals, which might be OK if your application can tolerate a little delay. Otherwise you'll need the application that has write access to the db to notify your application or your cache system when an update occurs.\nEdit: since you seem to have control over app B, and you've already got a cache system in app A, the simplest way to solve your problem is probably to create a callback in app A that app B can call to expire cached items. Both apps need to agree on a convention to identify cached items.","Q_Score":1,"Tags":"python,sql,orm,sqlalchemy","A_Id":7429664,"CreationDate":"2011-09-15T06:12:00.000","Title":"How to interface with another database effectively using python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"My Python High Replication Datastore application requires a large lookup table of between 100,000 and 1,000,000 entries. I need to be able to supply a code to some method that will return the value associated with that code (or None if there is no association). For example, if my table held acceptable English words then I would want the function to return True if the word was found and False (or None) otherwise.\nMy current implementation is to create one parentless entity for each table entry, and for that entity to contain any associated data. I set the datastore key for that entity to be the same as my lookup code. (I put all the entities into their own namespace to prevent any key conflicts, but that's not essential for this question.) Then I simply call get_by_key_name() on the code and I get the associated data.\nThe problem is that I can't access these entities during a transaction because I'd be trying to span entity groups. So going back to my example, let's say I wanted to spell-check all the words used in a chat session. I could access all the messages in the chat because I'd give them a common ancestor, but I couldn't access my word table because the entries there are parentless. It is imperative that I be able to reference the table during transactions.\nNote that my lookup table is fixed, or changes very rarely. Again this matches the spell-check example.\nOne solution might be to load all the words in a chat session during one transaction, then spell-check them (saving the results), then start a second transaction that would spell-check against the saved results. But not only would this be inefficient, the chat session might have been added to between the transactions. This seems like a clumsy solution.\nIdeally I'd like to tell GAE that the lookup table is immutable, and that because of this I should be able to query against it without its complaining about spanning entity groups in a transaction. I don't see any way to do this, however.\nStoring the table entries in the memcache is tempting, but that too has problems. It's a large amount of data, but more troublesome is that if GAE boots out a memcache entry I wouldn't be able to reload it during the transaction.\nDoes anyone know of a suitable implementation for large global lookup tables?\nPlease understand that I'm not looking for a spell-check web service or anything like that. I'm using word lookup as an example only to make this question clear, and I'm hoping for a general solution for any sort of large lookup tables.","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":143,"Q_Id":7451163,"Users Score":1,"Answer":"If you can, try and fit the data into instance memory. If it won't fit in instance memory, you have a few options available to you.\nYou can store the data in a resource file that you upload with the app, if it only changes infrequently, and access it off disk. This assumes you can build a data structure that permits easy disk lookups - effectively, you're implementing your own read-only disk based table.\nLikewise, if it's too big to fit as a static resource, you could take the same approach as above, but store the data in blobstore.\nIf your data absolutely must be in the datastore, you may need to emulate your own read-modify-write transactions. Add a 'revision' property to your records. To modify it, fetch the record (outside a transaction), perform the required changes, then inside a transaction, fetch it again to check the revision value. If it hasn't changed, increment the revision on your own record and store it to the datastore.\nNote that the underlying RPC layer does theoretically support multiple independent transactions (and non-transactional operations), but the APIs don't currently expose any way to access this from within a transaction, short of horrible (and I mean really horrible) hacks, unfortunately.\nOne final option: You could run a backend provisioned with more memory, exposing a 'SpellCheckService', and make URLFetch calls to it from your frontends. Remember, in-memory is always going to be much, much faster than any disk-based option.","Q_Score":0,"Tags":"python,google-app-engine,transactions,google-cloud-datastore,entity-groups","A_Id":7466485,"CreationDate":"2011-09-16T22:55:00.000","Title":"GAE Lookup Table Incompatible with Transactions?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"My Python High Replication Datastore application requires a large lookup table of between 100,000 and 1,000,000 entries. I need to be able to supply a code to some method that will return the value associated with that code (or None if there is no association). For example, if my table held acceptable English words then I would want the function to return True if the word was found and False (or None) otherwise.\nMy current implementation is to create one parentless entity for each table entry, and for that entity to contain any associated data. I set the datastore key for that entity to be the same as my lookup code. (I put all the entities into their own namespace to prevent any key conflicts, but that's not essential for this question.) Then I simply call get_by_key_name() on the code and I get the associated data.\nThe problem is that I can't access these entities during a transaction because I'd be trying to span entity groups. So going back to my example, let's say I wanted to spell-check all the words used in a chat session. I could access all the messages in the chat because I'd give them a common ancestor, but I couldn't access my word table because the entries there are parentless. It is imperative that I be able to reference the table during transactions.\nNote that my lookup table is fixed, or changes very rarely. Again this matches the spell-check example.\nOne solution might be to load all the words in a chat session during one transaction, then spell-check them (saving the results), then start a second transaction that would spell-check against the saved results. But not only would this be inefficient, the chat session might have been added to between the transactions. This seems like a clumsy solution.\nIdeally I'd like to tell GAE that the lookup table is immutable, and that because of this I should be able to query against it without its complaining about spanning entity groups in a transaction. I don't see any way to do this, however.\nStoring the table entries in the memcache is tempting, but that too has problems. It's a large amount of data, but more troublesome is that if GAE boots out a memcache entry I wouldn't be able to reload it during the transaction.\nDoes anyone know of a suitable implementation for large global lookup tables?\nPlease understand that I'm not looking for a spell-check web service or anything like that. I'm using word lookup as an example only to make this question clear, and I'm hoping for a general solution for any sort of large lookup tables.","AnswerCount":2,"Available Count":2,"Score":0.0996679946,"is_accepted":false,"ViewCount":143,"Q_Id":7451163,"Users Score":1,"Answer":"First, if you're under the belief that a namespace is going to help avoid key collisions, it's time to take a step back. A key consists of an entity kind, a namespace, a name or id, and any parents that the entity might have. It's perfectly valid for two different entity kinds to have the same name or id. So if you have, say, a LookupThingy that you're matching against, and have created each member by specifying a unique name, the key isn't going to collide with anything else.\nAs for the challenge of doing the equivalent of a spell-check against an unparented lookup table within a transaction, is it possible to keep the lookup table in code?\nOr can you think of an analogy that's closer to what you need? One that motivates the need to do the lookup within a transaction?","Q_Score":0,"Tags":"python,google-app-engine,transactions,google-cloud-datastore,entity-groups","A_Id":7452303,"CreationDate":"2011-09-16T22:55:00.000","Title":"GAE Lookup Table Incompatible with Transactions?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I have a function where I save a large number of models, (thousands at a time), this takes several minutes so I have written a progress bar to display progress to the user. The progress bar works by polling a URL (from Javascript) and looking a request.session value to see the state of the first call (the one that is saving).\nThe problem is that the first call is within a @transaction.commit_on_success decorator and because I am using Database Backed sessions when I try to force request.session.save() instead of it immediately committing it is appended to the ongoing transaction. This results in the progress bar only being updated once all the saves are complete, thus rendering it useless.\nMy question is, (and I'm 99.99% sure I already know the answer), can you commit statements within a transaction without doing the whole lot. i.e. I need to just commit the request.session.save() whilst leaving all of the others..\nMany thanks, Alex","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":839,"Q_Id":7472348,"Users Score":1,"Answer":"No, both your main saves and the status bar updates will be conducted using the same database connection so they will be part of the same transaction.\nI can see two options to avoid this.\n\nYou can either create your own, separate database connection and save the status bar updates using that. \nDon't save the status bar updates to the database at all and instead use a cache to store them. As long as you don't use the database cache backend (ideally you'd use memcached) this will work fine.\n\nMy preferred option would be the second one. You'll need to delve into the Django internals to get your own database connection so that could is likely to end up fragile and messy.","Q_Score":3,"Tags":"python,sql,django","A_Id":7473401,"CreationDate":"2011-09-19T14:15:00.000","Title":"Force commit of nested save() within a transaction","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"i use pymongo to test the performance of the mongodb.\ni use 100 threads, every thread excecute 5000 insert, and everything work ok.\nbut when i excecute 10000 insert in every thead,  i meet some error:\n\"AutoReconnect: Connection reset by peer\"","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":1676,"Q_Id":7479907,"Users Score":1,"Answer":"Driver can't remove dropped socket from connection from pool until your code try use it.","Q_Score":3,"Tags":"python,mongodb,pymongo","A_Id":18267147,"CreationDate":"2011-09-20T03:48:00.000","Title":"Mongodb : AutoReconnect, Connection reset by peer","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am currently writing a Python script to interact with an SQLite database but it kept returning that the database was \"Encrypted or Corrupted\".\nThe database is definitely not encrypted and so I tried to open it using the sqlite3 library at the command line (returned the same error) and with SQLite Manager add-on for Firefox...\nI had a copy of the same database structure but populated by a different instance of this program on a windows box, I tried to open it using SQLite Manager and it was fine, so as a quick test I loaded the \"Encrypted or Corrupted\" database onto a USB stick and plugged it into the windows machine, using the manager it opened first time without issues.\nDoes anyone have any idea what may be causing this?\nEDIT:\nOn the Linux machine I tried accessing it as root with no luck, I also tried chmoding it to 777 just as a test (on a copied version of the DB), again with no luck","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1207,"Q_Id":7511965,"Users Score":0,"Answer":"You should check the user privileges, the user on linux may not have enough privileges.","Q_Score":0,"Tags":"python,sql,database,sqlite","A_Id":7512015,"CreationDate":"2011-09-22T08:40:00.000","Title":"SQLite3 Database file - Corrupted\/Encrypted only on Linux","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm developing an web based application written in PHP5, which basically is an UI on top of a database. To give users a more flexible tool I want to embed a scripting language, so they can do more complex things like fire SQL queries, do loops and store data in variables and so on. In my business domain Python is widely used for scripting, but I'm also thinking of making a simple Domain Specific Language. The script has to wrap my existing PHP classes.\nI'm seeking advise on how to approach this development task? \nUpdate: I'll try scripting in the database using PLPGSQL in PostgreSQL. This will do for now, but I can't use my PHP classes this way. Lua approach is appealing and seems what is what I want (besides its not Python).","AnswerCount":6,"Available Count":2,"Score":0.0996679946,"is_accepted":false,"ViewCount":570,"Q_Id":7528360,"Users Score":3,"Answer":"How about doing the scripting on the client. That will ensure maximum security and also save server resources.\nIn other words Javascript would be your scripting platform. What you do is expose the functionality of your backend as javascript functions. Depending on how your app is currently written that might require backend work or not.\nOh and by the way you are not limited to javascript for the actual language. Google \"compile to javascript\" and first hit should be a list of languages you can use.","Q_Score":11,"Tags":"php,python,dsl,plpgsql","A_Id":7660613,"CreationDate":"2011-09-23T11:36:00.000","Title":"Embed python\/dsl for scripting in an PHP web application","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm developing an web based application written in PHP5, which basically is an UI on top of a database. To give users a more flexible tool I want to embed a scripting language, so they can do more complex things like fire SQL queries, do loops and store data in variables and so on. In my business domain Python is widely used for scripting, but I'm also thinking of making a simple Domain Specific Language. The script has to wrap my existing PHP classes.\nI'm seeking advise on how to approach this development task? \nUpdate: I'll try scripting in the database using PLPGSQL in PostgreSQL. This will do for now, but I can't use my PHP classes this way. Lua approach is appealing and seems what is what I want (besides its not Python).","AnswerCount":6,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":570,"Q_Id":7528360,"Users Score":0,"Answer":"You could do it without Python, by ie. parsing the user input for pre-defined \"tags\" and returning the result.","Q_Score":11,"Tags":"php,python,dsl,plpgsql","A_Id":7605372,"CreationDate":"2011-09-23T11:36:00.000","Title":"Embed python\/dsl for scripting in an PHP web application","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I would like to store windows path in MySQL without escaping the backslashes. How can I do this in Python? I am using MySQLdb to insert records into the database. When I use MySQLdb.escape_string(), I notice that the backslashes are removed.","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1040,"Q_Id":7553200,"Users Score":0,"Answer":"Have a look at   os.path.normpath(thePath)\nI can't remember if it's that one, but there IS a standard os.path formating function that gives double backslashes, that can be stored in a db \"as is\" and reused later \"as is\". I have no more windows machine and cannot test it anymore.","Q_Score":0,"Tags":"python,mysql","A_Id":7553317,"CreationDate":"2011-09-26T09:36:00.000","Title":"Storing windows path in MySQL without escaping backslashes","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm trying to write a pop3 and imap clients in python using available libs, which will download email headers (and subsequently entire email bodies) from various servers and save them in a mongodb database. The problem I'm facing is that this client downloads emails in addition to a user's regular email client. So with the assumption that a user might or might not leave emails on the server when downloading using his mail client, I'd like to fetch the headers but only collect them from a certain date, to avoid grabbing entire mailboxes every time I fetch the headers. \nAs far as I can see the POP3 list call will get me all messages on the server, even those I probably already  downloaded. IMAP doesn't have this problem.\nHow do email clients handle this situation when dealing with POP3 servers?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1501,"Q_Id":7553606,"Users Score":3,"Answer":"Outlook logs in to a POP3 server and issues the STAT, LIST and UIDL commands; then if it decides the user has no new messages it logs out.  I have observed Outlook doing this when tracing network traffic between a client and my DBMail POP3 server.  I have seen Outlook fail to detect new messages on a POP3 server using this method.  Thunderbird behaves similarly but I have never seen it fail to detect new messages.\nIssue the LIST and UIDL commands to the server after logging in.  LIST gives you an index number (the message's linear position in the mailbox) and the size of each message.  UIDL gives you the same index number and a computed hash value for each message.\nFor each user you can store the size and hash value given by LIST and UIDL.  If you see the same size and hash value, assume it is the same message.  When a given message no longer appears in this list, assume it has been deleted and clear it from your local memory.\nFor complete purity, remember the relative positions of the size\/hash pairs in the message list, so that you can support the possibility that they may repeat.  (My guess on Outlook's new message detection failure is that sometimes these values do repeat, at least for DBMail, but Outlook remembers them even after they are deleted, and forever considers them not new.  If it were me, I would try to avoid this behavior.)\nFootnote: Remember that the headers are part of the message.  Do not trust anything in the header for this reason: dates, senders, even server hand-off information can be easily faked and cannot be assumed unique.","Q_Score":3,"Tags":"python,email,pop3","A_Id":7556750,"CreationDate":"2011-09-26T10:14:00.000","Title":"Download POP3 headers from a certain date (Python)","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have been doing lots of searching and reading to solve this.\nThe main goal is let a Django-based web management system connecting to a device which runs a http server as well. Django will handle user request and ask device for the real data, then feedback to user.\nNow I have a \"kinda-work-in-concept\" solution:\n\nBrowser -> Apache Server: Browser have jQuery and HTML\/CSS to collect user request.\nApache Server-> Device HTTP Server:\n\nApache + mod_python(or somesay Apache + mod_wsgi?) , so I might control the Apache to do stuff like build up a session and cookies to record login.\nBut, this is the issue actually bugs me. \nHow to make it work? Using what to build up socket connection between this two servers?","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":320,"Q_Id":7565812,"Users Score":0,"Answer":"If you have control over what runs on the device side, consider using XML-RPC to talk from client to server.","Q_Score":0,"Tags":"python,django,apache,mod-wsgi,mod-python","A_Id":7567682,"CreationDate":"2011-09-27T07:52:00.000","Title":"How to control Apache via Django to connect to mongoose(another HTTP server)?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I know about the XLWT library, which I've used before on a Django project. XLWT is very neat but as far as I know, it doesn't support .xlsx which is the biggest obstacle in my case. I'm probably going to be dealing with more than 2**16 rows of information. Is there any other mature similar library? Or even better, is there a fork for the XLWT with this added functionality? I know there are libraries in C#, but if a python implementation already exists, it would be a lot better.\nThanks a bunch!","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1504,"Q_Id":7576309,"Users Score":0,"Answer":"Export a CSV don't use .xlsx..","Q_Score":3,"Tags":"python,xls,xlsx,xlwt,openpyxl","A_Id":7576355,"CreationDate":"2011-09-27T22:14:00.000","Title":"Exporting to Excel .xlsx from a Python Pyramid project","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am researching a project that would require hundreds of database writes per a minute. I have never dealt with this level of data writes before and I am looking for good scalable techniques and technologies.\nI am a comfortable python developer with experience in django and sql alchemy. I am thinking I will build the data interface on django, but I don't think that it is a good idea to go through the orm to do the amount of data writes I will require. I am definitely open to learning new technologies.\nThe solution will live on Amazon web services, so I have access to all their tools. Ultimately I am looking for advice on database selection, data writing techniques, and any other needs I may have that I do not realize. \nAny advice on where to start?\nThanks,\nCG","AnswerCount":3,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":324,"Q_Id":7586999,"Users Score":0,"Answer":"You should actually be okay with low hundreds of writes per minute through SQLAlchemy (thats only a couple a second); if you're talking more like a thousand a minute, yeah that might be problematic.\nWhat kind of data do you have?  If it's fairly flat (few tables, few relations), you might want to investigate a non-relational database such as CouchDB or Mongo.  If you want to use SQL, I strongly reccommend PostgreSQL, it seems to deal with large databases and frequent writes a lot better than MySQL.\nIt also depends how complex the data is that you're inserting.\nI think unfortunately, you're going to just have to try a couple things and run benchmarks, as each situation is different and query optimizers are basically magic.","Q_Score":0,"Tags":"python,django,database-design,amazon-web-services","A_Id":7587624,"CreationDate":"2011-09-28T17:14:00.000","Title":"Setup for high volume of database writing","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am researching a project that would require hundreds of database writes per a minute. I have never dealt with this level of data writes before and I am looking for good scalable techniques and technologies.\nI am a comfortable python developer with experience in django and sql alchemy. I am thinking I will build the data interface on django, but I don't think that it is a good idea to go through the orm to do the amount of data writes I will require. I am definitely open to learning new technologies.\nThe solution will live on Amazon web services, so I have access to all their tools. Ultimately I am looking for advice on database selection, data writing techniques, and any other needs I may have that I do not realize. \nAny advice on where to start?\nThanks,\nCG","AnswerCount":3,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":324,"Q_Id":7586999,"Users Score":0,"Answer":"If it's just a few hundred writes you still can do with a relational DB. I'd pick PostgreSQL (8.0+),\nwhich has a separate background writer process. It also has tuneable serialization levels so you\ncan enable some tradeoffs between speed and strict ACID compliance, some even at transaction level.\nPostgres is well documented, but it assumes some deeper understanding of SQL and relational DB theory to fully understand and make the most of it.\nThe alternative would be new fangled \"NO-SQL\" system, which can probably scale even better, but at the cost of buying into a very different technology system.\nAny way, if you are using python and it is not 100% critical to lose writes on shutdown or power loss, and you need a low latency, use a threadsafe Queue.Queue and worker threads to decouple the writes from your main application thread(s).","Q_Score":0,"Tags":"python,django,database-design,amazon-web-services","A_Id":7587774,"CreationDate":"2011-09-28T17:14:00.000","Title":"Setup for high volume of database writing","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Problem\nI am writing a program that reads a set of documents from a corpus (each line is a document). Each document is processed using a function processdocument, assigned a unique ID, and then written to a database. Ideally, we want to do this using several processes. The logic is as follows:\n\nThe main routine creates a new database and sets up some tables.\nThe main routine sets up a group of processes\/threads that will run a worker function.\nThe main routine starts all the processes.\nThe main routine reads the corpus, adding documents to a queue.\nEach process's worker function loops, reading a document from a queue, extracting the information from it using processdocument, and writes the information to a new entry in a table in the database. \nThe worker loops breaks once the queue is empty and an appropriate flag has been set by the main routine (once there are no more documents to add to the queue).\n\nQuestion\nI'm relatively new to sqlalchemy (and databases in general). I think the code used for setting up the database in the main routine works fine, from what I can tell. Where I'm stuck is I'm not sure exactly what to put into the worker functions for each process to write to the database without clashing with the others. \nThere's nothing particularly complicated going on: each process gets a unique value to assign to an entry from a multiprocessing.Value object, protected by a Lock. I'm just not sure whether what I should be passing to the worker function (aside from the queue), if anything. Do I pass the sqlalchemy.Engine instance I created in the main routine? The Metadata instance? Do I create a new engine for each process? Is there some other canonical way of doing this? Is there something special I need to keep in mind?\nAdditional Comments\nI'm well aware I could just not bother with the multiprocessing but and do this in a single process, but I will have to write code that has several processes reading for the database later on, so I might as well figure out how to do this now.\nThanks in advance for your help!","AnswerCount":1,"Available Count":1,"Score":0.761594156,"is_accepted":false,"ViewCount":1473,"Q_Id":7603790,"Users Score":5,"Answer":"The MetaData and its collection of Table objects should be considered a fixed, immutable structure of your application, not unlike your function and class definitions.  As you know with forking a child process, all of the module-level structures of your application remain present across process boundaries, and table defs are usually in this category.\nThe Engine however refers to a pool of DBAPI connections which are usually TCP\/IP connections and sometimes filehandles.  The DBAPI connections themselves are generally not portable over a subprocess boundary, so you would want to either create a new Engine for each subprocess, or use a non-pooled Engine, which means you're using NullPool.\nYou also should not be doing any kind of association of MetaData with Engine, that is \"bound\" metadata.  This practice, while prominent on various outdated tutorials and blog posts, is really not a general purpose thing and I try to de-emphasize this way of working as much as possible.\nIf you're using the ORM, a similar dichotomy of \"program structures\/active work\" exists, where your mapped classes of course are shared between all subprocesses, but you definitely want Session objects to be local to a particular subprocess - these correspond to an actual DBAPI connection as well as plenty of other mutable state which is best kept local to an operation.","Q_Score":1,"Tags":"python,database,multithreading,sqlalchemy,multiprocessing","A_Id":7603832,"CreationDate":"2011-09-29T21:50:00.000","Title":"How to use simple sqlalchemy calls while using thread\/multiprocessing","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"So I am pretty sure that I have managed to dork up my MySQLdb installation. I have all of the following installed correctly on a fresh install of OS X Lion:\n\nphpMyAdmin\nMySQL 5.5.16\nDjango 1.3.1\n\nAnd yet when I try to run \"from django.db import connection\" in a django console, I get the following:\n\n\n\n\nfrom django.db import connection Traceback (most recent call\n        last):   File \"\", line 1, in    File\n        \"\/Library\/Python\/2.7\/site-packages\/Django-1.3.1-py2.7.egg\/django\/db\/init.py\",\n        line 78, in \n            connection = connections[DEFAULT_DB_ALIAS]   File\n        \"\/Library\/Python\/2.7\/site-packages\/Django-1.3.1-py2.7.egg\/django\/db\/utils.py\",\n        line 93, in getitem\n            backend = load_backend(db['ENGINE'])   File\n        \"\/Library\/Python\/2.7\/site-packages\/Django-1.3.1-py2.7.egg\/django\/db\/utils.py\",\n        line 33, in load_backend\n            return import_module('.base', backend_name)   File\n        \"\/Library\/Python\/2.7\/site-packages\/Django-1.3.1-py2.7.egg\/django\/utils\/importlib.py\",\n        line 35, in import_module\n            import(name)   File\n        \"\/Library\/Python\/2.7\/site-packages\/Django-1.3.1-py2.7.egg\/django\/db\/backends\/mysql\/base.py\",\n        line 14, in \n            raise ImproperlyConfigured(\"Error loading MySQLdb module: %s\" % e)\n        ImproperlyConfigured: Error loading MySQLdb module: dlopen(\/Users\/[my\n        username]\/.python-eggs\/MySQL_python-1.2.3-py2.7-macosx-10.7-intel.egg-tmp\/_mysql.so,\n        2): Library not loaded: libmysqlclient.18.dylib   Referenced from:\n        \/Users\/[my\n        username]\/.python-eggs\/MySQL_python-1.2.3-py2.7-macosx-10.7-intel.egg-tmp\/_mysql.so\n        Reason: image not found\n\n\n\n\nI have no idea why this is happening, could somebody help walk me through this?","AnswerCount":3,"Available Count":2,"Score":0.0665680765,"is_accepted":false,"ViewCount":3834,"Q_Id":7605212,"Users Score":1,"Answer":"Install pip if you haven't already, and run \npip install MySQL-Python","Q_Score":2,"Tags":"python,mysql,django,macos,mysql-python","A_Id":7605229,"CreationDate":"2011-09-30T01:53:00.000","Title":"Having an issue with setting up MySQLdb on Mac OS X Lion in order to support Django","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"So I am pretty sure that I have managed to dork up my MySQLdb installation. I have all of the following installed correctly on a fresh install of OS X Lion:\n\nphpMyAdmin\nMySQL 5.5.16\nDjango 1.3.1\n\nAnd yet when I try to run \"from django.db import connection\" in a django console, I get the following:\n\n\n\n\nfrom django.db import connection Traceback (most recent call\n        last):   File \"\", line 1, in    File\n        \"\/Library\/Python\/2.7\/site-packages\/Django-1.3.1-py2.7.egg\/django\/db\/init.py\",\n        line 78, in \n            connection = connections[DEFAULT_DB_ALIAS]   File\n        \"\/Library\/Python\/2.7\/site-packages\/Django-1.3.1-py2.7.egg\/django\/db\/utils.py\",\n        line 93, in getitem\n            backend = load_backend(db['ENGINE'])   File\n        \"\/Library\/Python\/2.7\/site-packages\/Django-1.3.1-py2.7.egg\/django\/db\/utils.py\",\n        line 33, in load_backend\n            return import_module('.base', backend_name)   File\n        \"\/Library\/Python\/2.7\/site-packages\/Django-1.3.1-py2.7.egg\/django\/utils\/importlib.py\",\n        line 35, in import_module\n            import(name)   File\n        \"\/Library\/Python\/2.7\/site-packages\/Django-1.3.1-py2.7.egg\/django\/db\/backends\/mysql\/base.py\",\n        line 14, in \n            raise ImproperlyConfigured(\"Error loading MySQLdb module: %s\" % e)\n        ImproperlyConfigured: Error loading MySQLdb module: dlopen(\/Users\/[my\n        username]\/.python-eggs\/MySQL_python-1.2.3-py2.7-macosx-10.7-intel.egg-tmp\/_mysql.so,\n        2): Library not loaded: libmysqlclient.18.dylib   Referenced from:\n        \/Users\/[my\n        username]\/.python-eggs\/MySQL_python-1.2.3-py2.7-macosx-10.7-intel.egg-tmp\/_mysql.so\n        Reason: image not found\n\n\n\n\nI have no idea why this is happening, could somebody help walk me through this?","AnswerCount":3,"Available Count":2,"Score":0.3215127375,"is_accepted":false,"ViewCount":3834,"Q_Id":7605212,"Users Score":5,"Answer":"I found the following solution for this issue. It worked for me. I have encountered this problem when I was running python console from PyCharm.\nsudo ln -s \/usr\/local\/mysql\/lib\/libmysqlclient.18.dylib \/usr\/lib\/libmysqlclient.18.dylib","Q_Score":2,"Tags":"python,mysql,django,macos,mysql-python","A_Id":12027574,"CreationDate":"2011-09-30T01:53:00.000","Title":"Having an issue with setting up MySQLdb on Mac OS X Lion in order to support Django","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I've been spending the better part of the weekend trying to figure out the best way to transfer data from an MS Access table into an Excel sheet using Python. I've found a few modules that may help (execsql, python-excel), but with my limited knowledge and the modules I have to use to create certain data (I'm a GIS professional, so I'm creating spatial data using the ArcGIS arcpy module into an access table) \nI'm not sure what the best approach should be. All I need to do is copy 4 columns of data from access to excel and then format the excel. I have the formatting part solved.\nShould I:\nIterate through the rows using a cursor and somehow load the rows into excel?\nCopy the columns from access to excel?\nExport the whole access table into a sheet in excel?\nThanks for any suggestions.","AnswerCount":5,"Available Count":2,"Score":0.0399786803,"is_accepted":false,"ViewCount":4767,"Q_Id":7630142,"Users Score":1,"Answer":"Another idea - how important is the formatting part? If you can ditch the formatting, you can output your data as CSV. Excel can open CSV files, and the CSV format is much simpler then the Excel format - it's so simple you can write it directly from Python like a text file, and that way you won't need to mess with Office COM objects.","Q_Score":2,"Tags":"python,excel,ms-access","A_Id":7636416,"CreationDate":"2011-10-03T00:23:00.000","Title":"Copy data from MS Access to MS Excel using Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I've been spending the better part of the weekend trying to figure out the best way to transfer data from an MS Access table into an Excel sheet using Python. I've found a few modules that may help (execsql, python-excel), but with my limited knowledge and the modules I have to use to create certain data (I'm a GIS professional, so I'm creating spatial data using the ArcGIS arcpy module into an access table) \nI'm not sure what the best approach should be. All I need to do is copy 4 columns of data from access to excel and then format the excel. I have the formatting part solved.\nShould I:\nIterate through the rows using a cursor and somehow load the rows into excel?\nCopy the columns from access to excel?\nExport the whole access table into a sheet in excel?\nThanks for any suggestions.","AnswerCount":5,"Available Count":2,"Score":0.0399786803,"is_accepted":false,"ViewCount":4767,"Q_Id":7630142,"Users Score":1,"Answer":"The best approach might be to not use Python for this task.\nYou could use the macro recorder in Excel to record the import of the External data into Excel. \nAfter starting the macro recorder click Data -> Get External Data -> New Database Query and enter your criteria. Once the data import is complete you can look at the code that was generated and replace the hard coded search criteria with variables.","Q_Score":2,"Tags":"python,excel,ms-access","A_Id":7630189,"CreationDate":"2011-10-03T00:23:00.000","Title":"Copy data from MS Access to MS Excel using Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am importing text files into excel using xlwt module. But it allows only 256 columns to be stored. Are there any ways to solve this problem?","AnswerCount":6,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":18626,"Q_Id":7658513,"Users Score":0,"Answer":"If you trying to write to the columns in the for loop and getting this error, then re-initalize the column to 0 while iterating.","Q_Score":14,"Tags":"python","A_Id":70290332,"CreationDate":"2011-10-05T08:21:00.000","Title":"Python - Xlwt more than 256 columns","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am importing text files into excel using xlwt module. But it allows only 256 columns to be stored. Are there any ways to solve this problem?","AnswerCount":6,"Available Count":2,"Score":0.0333209931,"is_accepted":false,"ViewCount":18626,"Q_Id":7658513,"Users Score":1,"Answer":"Is that a statement of fact or should xlwt support more than 256 columns? What error do you get? What does your code look like?\nIf it truly does have a 256 column limit, just write your data in a csv-file using the appropriate python module and import the file into Excel.","Q_Score":14,"Tags":"python","A_Id":7658627,"CreationDate":"2011-10-05T08:21:00.000","Title":"Python - Xlwt more than 256 columns","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm using Python with Celery and RabbitMQ to make a web spider to count the number of links on a page.\nCan a database, such as MySQL, be written into asynchronously?  Is it OK to commit the changes after every row added, or is it required to batch them (multi-add) and then commit after a certain number of rows\/duration?\nI'd prefer to use SQLAlchemy and MySQL, unless there is a more recommended combination for Celery\/RabbitMQ.  I also see NoSQL (CouchDB?) recommended.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":728,"Q_Id":7659246,"Users Score":1,"Answer":"For write intensive operation like Counters and Logs NoSQL solution are always the best choice. Personally I use a mongoDB for this kind of tasks.","Q_Score":0,"Tags":"python,database,asynchronous,rabbitmq,celery","A_Id":7780116,"CreationDate":"2011-10-05T09:31:00.000","Title":"Python Celery Save Results in Database Asynchronously","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am trying to edit several excel files (.xls) without changing the rest of the sheet. The only thing close so far that I've found is the xlrd, xlwt, and xlutils modules. The problem with these is it seems that xlrd evaluates formulae when reading, then puts the answer as the value of the cell. Does anybody know of a way to preserve the formulae so I can then use xlwt to write to the file without losing them? I have most of my experience in Python and CLISP, but could pick up another language pretty quick if they have better support. Thanks for any help you can give!","AnswerCount":4,"Available Count":1,"Score":0.049958375,"is_accepted":false,"ViewCount":8902,"Q_Id":7665486,"Users Score":1,"Answer":"As of now, xlrd doesn't read formulas.  It's not that it evaluates them, it simply doesn't read them.\nFor now, your best bet is to programmatically control a running instance of Excel, either via pywin32 or Visual Basic or VBScript (or some other Microsoft-friendly language which has a COM interface).  If you can't run Excel, then you may be able to do something analogous with OpenOffice.org instead.","Q_Score":0,"Tags":"python,excel,formula,xlwt,xlrd","A_Id":7667880,"CreationDate":"2011-10-05T17:52:00.000","Title":"Is there any way to edit an existing Excel file using Python preserving formulae?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm using postgresql and python and I need to store data group by week of the year. So, there's plenty alternatives:\n\nweek and year in two separated fields\na date pointing to the start of the week (or a random day of the week)\nAnd, the one I like: an interval type.\n\nI never use it, but reading the docs, seems to fit. But then, reading psycopg docs I found interval mapped to python timedelta object... seems weird to me, a timedelta is just a difference.\nSo, there are two question here, really:\n\nCan I handle this choice using psycopg2? \nIs the better alternative?\n\nThanks","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":661,"Q_Id":7668822,"Users Score":4,"Answer":"The PostgreSQL interval type isn't really what you're looking for -- it's specifically intended for storing an arbitrary length of time, ranging anywhere from a microsecond to a few million years. An interval has no starting or ending point; it's just a measure of \"how long\".\nIf you're specifically after storing which week an event is associated with, you're probably better off with either of your first two options.","Q_Score":0,"Tags":"python,postgresql,psycopg2","A_Id":7668912,"CreationDate":"2011-10-05T23:11:00.000","Title":"psycopg2: interval type for storing weeks","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm writing a script to access data in an established database and unfortunately, I'm breaking the DB.  I'm able to recreate the issue from the command line:\n\n    [user@box tmp]# python\n    Python 2.7.2 (default, Sep 19 2011, 15:02:41) \n    [GCC 4.1.2 20080704 (Red Hat 4.1.2-48)] on linux2\n    Type \"help\", \"copyright\", \"credits\" or \"license\" for more information.\n    >>> import pgdb\n    >>> db = pgdb.connect('localhost:my_db:postgres')\n    >>> cur = db.cursor()\n    >>> cur.execute(\"SELECT * FROM mytable LIMIT 10\")\n    >>> cur.close()\n    >>> \n\nAt this point any activity to mytable is greatly degraded and \"select * from pg_stat_activity\" shows my connection as \"IDLE in transaction\".  If I call db.close() everything is fine, but my script loops infinitely and I didn't think I'd need to open and close the db connection with each loop.  I don't think it has anything to do with the fact that I'm not using the data above as in my real script I am calling fetchone() (in a loop) to process the data.  I'm not much of a DB guy so I'm not sure what other info would be useful.  My postgres version is 9.1.0 and python is 2.7.2 as shown above.","AnswerCount":2,"Available Count":2,"Score":0.1973753202,"is_accepted":false,"ViewCount":1471,"Q_Id":7669434,"Users Score":2,"Answer":"I suggest using psycopg2 instead of pgdb.  pgdb uses the following semantics:\nconnect() -> open database connection, begin transaction\ncommit() -> commit, begin transaction\nrollback() -> rollback, begin transaction\nexecute() -> execute statement  \npsycopg2, on the other hand, uses the following semantics:\nconnect() -> open database connection\ncommit() -> commit\nrollback() -> rollback\nexecute() -> begin transaction unless already in transaction, execute statement  \nso, as Amber mentioned, you can do a rollback or commit after your select statement and terminate the transaction.  Unfortunately, with pgdb, you will immediately start a new transaction after you rollback or commit (even if you haven't performed any work).\nFor many database systems, pgdb's behavior is fine, but because of the way PostgreSQL handles transactions, it can cause trouble for you if you've got lots of connections accessing the same tables (trouble specifically with vacuum).\nWhy does pgdb start a transaction right away?  The Python DB-API (2.0) spec calls for it to do so.  Seems kind of silly to me, but that's the way the spec is written.","Q_Score":2,"Tags":"python,postgresql,pgdb","A_Id":7670330,"CreationDate":"2011-10-06T01:15:00.000","Title":"python pgdb hanging database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm writing a script to access data in an established database and unfortunately, I'm breaking the DB.  I'm able to recreate the issue from the command line:\n\n    [user@box tmp]# python\n    Python 2.7.2 (default, Sep 19 2011, 15:02:41) \n    [GCC 4.1.2 20080704 (Red Hat 4.1.2-48)] on linux2\n    Type \"help\", \"copyright\", \"credits\" or \"license\" for more information.\n    >>> import pgdb\n    >>> db = pgdb.connect('localhost:my_db:postgres')\n    >>> cur = db.cursor()\n    >>> cur.execute(\"SELECT * FROM mytable LIMIT 10\")\n    >>> cur.close()\n    >>> \n\nAt this point any activity to mytable is greatly degraded and \"select * from pg_stat_activity\" shows my connection as \"IDLE in transaction\".  If I call db.close() everything is fine, but my script loops infinitely and I didn't think I'd need to open and close the db connection with each loop.  I don't think it has anything to do with the fact that I'm not using the data above as in my real script I am calling fetchone() (in a loop) to process the data.  I'm not much of a DB guy so I'm not sure what other info would be useful.  My postgres version is 9.1.0 and python is 2.7.2 as shown above.","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":1471,"Q_Id":7669434,"Users Score":2,"Answer":"Try calling db.rollback() before you close the cursor (or if you're doing a write operation, db.commit()).","Q_Score":2,"Tags":"python,postgresql,pgdb","A_Id":7669476,"CreationDate":"2011-10-06T01:15:00.000","Title":"python pgdb hanging database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Pretty recent (but not newborn) to both Python, SQLAlchemy and Postgresql, and trying to understand inheritance very hard.\nAs I am taking over another programmer's code, I need to understand what is necessary, and where, for the inheritance concept to work.\nMy questions are:\n\nIs it possible to rely only on SQLAlchemy for inheritance? In other words, can SQLAlchemy apply inheritance on Postgresql database tables that were created without specifying INHERITS=?\nIs the declarative_base technology (SQLAlchemy) necessary to use inheritance the proper way. If so, we'll have to rewrite everything, so please don't discourage me.\nAssuming we can use Table instance, empty Entity classes and mapper(), could you give me a (very simple) example of how to go through the process properly (or a link to an easily understandable tutorial - I did not find any easy enough yet).\n\nThe real world we are working on is real estate objects. So we basically have\n- one table immobject(id, createtime)\n- one table objectattribute(id, immoobject_id, oatype)\n- several attribute tables: oa_attributename(oa_id, attributevalue)\nThanks for your help in advance.\nVincent","AnswerCount":2,"Available Count":1,"Score":0.3799489623,"is_accepted":false,"ViewCount":1451,"Q_Id":7672569,"Users Score":4,"Answer":"Welcome to Stack Overflow:  in the future, if you have more than one question; you should provide a separate post for each.  Feel free to link them together if it might help provide context.\nTable inheritance in postgres is a very different thing and solves a different set of problems from class inheritance in python, and sqlalchemy makes no attempt to combine them.\nWhen you use table inheritance in postgres, you're doing some trickery at the schema level so that more elaborate constraints can be enforced than might be easy to express in other ways;  Once you have designed your schema; applications aren't normally aware of the inheritance;  If they insert a row; it just magically appears in the parent table (much like a view).  This is useful, for instance, for making some kinds of bulk operations more efficient (you can just drop the table for the month of january).\nThis is a fundamentally different idea from inheritance as seen in OOP (in python or otherwise, with relational persistence or otherwise).  In that case, the application is aware that two types are related, and that the subtype is a permissible substitute for the supertype.  \"A holding is an address, a contact has an address therefore a contact can have a holding.\"  \nWhich of these, (mostly orthogonal) tools you need depends on the application.  You might need neither, you might need both.  \n\n\nSqlalchemy's mechanisms for working with object inheritance is flexible and robust, you should use it in favor of a home built solution if it is compatible with your particular needs (this should be true for almost all applications).\nThe declarative extension is a convenience; It allows you to describe the mapped table, the python class and the mapping between the two in one 'thing' instead of three.  It makes your code more \"DRY\";  It is however only a convenience layered on top of \"classic sqlalchemy\" and it isn't necessary by any measure.\nIf you find that you need table inheritance that's visible from sqlalchemy; your mapped classes won't be any different from not using those features; tables with inheritance are still normal relations (like tables or views) and can be mapped without knowledge of the inheritance in the python code.","Q_Score":1,"Tags":"python,postgresql,inheritance,sqlalchemy","A_Id":7675115,"CreationDate":"2011-10-06T09:40:00.000","Title":"Python, SQLAlchemy and Postgresql: understanding inheritance","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"At work we want our next generation product to be based on a graph database. I'm looking for suggestions as to what database engine might be appropriate for our new project:\nOut product is intended to keep track of a large number of prices for goods. Here's a simplistic example of what it does - supposing you wanted to estimate the price of gasoline in the UK - you know that Gasoline is refined from crude-oil. If you new the price of crude oil in the UK you could estimate the price of anything simply by adding the cost of refining, transporting (etc). Actually things are more complex because there are a number of sources of crude-oil and hundreds of refined oil products. The prices of oil products can be affected by the availability of other energy sources (e.g. nuclear, wind, natural gas) and the demand. It's kind of complex!\nThe idea is that we want to model the various inter-related goods and their costs of refining, transportation (etc) as an asyclic directed graph. The idea being, when an event causes a price to change then we want to be quickly able to determine what kinds of things are affected and re-calculate those prices ASAP. \nEssentially we need a database which can represent the individual commodities as nodes in the graph. Each node will store a number of curves and surfaces of information pertaining to the product. \nWe want to represent the various costs & transformations (e.g. refining, transportation) as labels on the edges. As with the nodes, the information we want to store could be quite complex - not just single values but curves and surfaces.  \nThe calculations we do are all linear with respect to the size of the objects, however since the graph could be very big we need to be able to traverse the graph very quickly. \nWe are Java and Python centric - ideally we are after a product that runs on the JVM but has really good APIs for both Python and Java. We don't care so much about other languages... but .Net would be nice to have (even though it might be years before we get round to doing something with it).\nWe'd definitely like something which was high-performance - but more importantly the system needs to have a degree of hardware fault tolerance. For example, we'd like to distribute the database across a number of physical servers. In the event that any of the servers go down we'd like to be able to continue without an interruption. \nOh, and we are really lazy. We dont want to spend much time writing infrastructure - so if the database came with tools that allow us to do as much as possible of this kind of thing with very little work that's fine by us. It would also be a real bonus if there was a grid technology associated with the graph DB, that way we could push a sequence of re-calculate jobs onto a compute grid and have much of our calculation done in paralell. \nSo, that's a description of the kind of thing we want to build. What I want to know is whether there are any mature technologies which will help us achieve this. As I mentioned before, we have a preference for Python & JVM, however if the technology is really good and comes with great bindings for Python + Java we'd consider almost anything.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":303,"Q_Id":7674895,"Users Score":3,"Answer":"Neo4J is the most mature graphDB I know of - and is java, with bindings for python too, or REST","Q_Score":2,"Tags":"java,python,database,graph","A_Id":7675078,"CreationDate":"2011-10-06T13:27:00.000","Title":"I'm looking for a graph-database for a Java\/Python centric organization","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"We have a bunch of utility scripts in Visual FoxPro, which we use to interactively cleanse\/format data.  We'd like to start migrating this code to make use of other database platforms, like MySQL or SQLite.  \nFor instance we have a script that we run which converts the name and\/or address lines to proper upper\/lower case.  This code goes through an entire table and analyzes\/fixes each row.  There are others, that do things like parse and standardize the address and even duplicate detection...\nWe're thinking of migrating the code to Python and possibly using something like SQLAlchemy as a \"middleman\".  \nIn Visual FoxPro the database\/tables are integrated so we can just open the table and run commands.  MySQL is different in that we need to extract data from it, then work on that extracted data, then update the table.  \nWhat would be the best approach? \nI see several possibilities:\n1) Extract the the entire data set to be worked on, say all the address fields, if that's what we're going to be working with, then updating it all and writing it all back...\n2) Extract the data set in chunks, so as to not potentially consume vast amounts of system memory... then update and write back\n3) Generate SQL code, perhaps with the help of a tool like SQLAlchemy, that gets sent to and executed by the server...\n4) ??? Anything else I didn't think of?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":789,"Q_Id":7681017,"Users Score":0,"Answer":"It seems like you're trying to do several things all at once. Could you take a step-by-step approach? Perhaps cleansing the data as they are right now using your normal, usual scripts. Then migrate the database to MySQL.\nIt is easy to migrate the database if VisualFoxPro offers a way to export the database to, say, CSV. You can then import that CSV into MySQL directly, with very little trouble. That gives you two databases that should be functionally identical. Of course, you have to prove that they are indeed identical, which isn't too hard but is time-consuming. You might be able to use SQLAlchemy to help.\nWhen the MySQL database is right, that's the time to port your cleansing scripts to Python or something and get those working. \nThat's how I would approach this problem: break it into pieces and not try to do too much in any single step.\nHTH","Q_Score":1,"Tags":"python,mysql,sqlalchemy,foxpro,data-cleaning","A_Id":7681237,"CreationDate":"2011-10-06T22:03:00.000","Title":"What's the best language\/technique to perform advanced data cleansing and formatting on a SQL\/MySQL\/PostgreSQL table?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a Pylons application using SQLAlchemy with SQLite as backend. I would like to know if every read operation going to SQLite will always lead to a hard disk read (which is very slow compared to RAM) or some caching mechanisms are already involved. \n\ndoes SQLite maintain a subset of the database in RAM for faster access ? \nCan the OS (Linux) do that automatically ? \nHow much speedup could I expect by using a production database (MySQL or PostgreSQL) instead of SQLite?","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":339,"Q_Id":7710895,"Users Score":3,"Answer":"Yes, SQLite has its own memory cache. Check PRAGMA cache_size for instance. Also, if you're looking for speedups, check PRAGMA temp_store. There is also API for implementing your own cache.\nThe SQLite database is just a file to the OS. Nothing is 'automatically' done for it. To ensure caching does happen, there are sqlite.h defines and runtime pragma settings.\nIt depends, there are a lot of cases when you'll get a slowdown instead.","Q_Score":5,"Tags":"python,sqlite,sqlalchemy","A_Id":7712124,"CreationDate":"2011-10-10T09:35:00.000","Title":"Are SQLite reads always hitting disk?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Best practice question about setting Mongo indexes.  Mongoengine, the Python ORM wrapper, allows you to set indexes in the Document meta class. \nWhen is this meta class introspected and the index added?  Can I build a collection via a mongoengine Document class and then add an index after the fact?\nIf I remove the index from the meta class, is the index automatically removed from the corresponding collection?\nThanks,","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":2747,"Q_Id":7758898,"Users Score":6,"Answer":"You can add an index at any time and ensureIndex will be called behind the scenes so it will be added if it doesn't exist.\nIf you remove an index from the meta - you will have to use pymongo or the shell to remove the index.","Q_Score":7,"Tags":"python,mongodb,indexing,mongoengine","A_Id":9082609,"CreationDate":"2011-10-13T18:43:00.000","Title":"How does MongoEngine handle Indexes (creation, update, removal)?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"which is better for production with web2py? please more insights.\nI'm very new 2 web2py and i am working on a small pharmacy mgt system. \npls which is better for production postgres or mysql? if postgres, step by step installation guide pls so to smoothly work with web2py. thanks","AnswerCount":4,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1454,"Q_Id":7761339,"Users Score":0,"Answer":"I say. Whatever you can work with from console. Some events may require fixing db from fingertip, you may also want to have some other ongoing actions in db and it might need to be done outside web2py.\nPosgreSQL is my choice as there are much less irregular behaviours thus its easier to grasp...","Q_Score":2,"Tags":"python,web2py","A_Id":9021132,"CreationDate":"2011-10-13T22:50:00.000","Title":"which is better for production with web2py?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am using memcached on a web site, and I am currently needing to open connections to a database and socket each time a function is called. In the case of the db connection, I am having to decide at runtime, which database to connect to.\nBecause of the (default) stateless nature of web apps, I am having to tear down (i.e. close) the connection after each function call. I am wondering if it is possible to store (i.e. cache) the socket connection and the database connections in memcache - do that I have a pool of db connections and a socket connection already open that I can use whenever the function is called.\nIs this safe ? \n[[Additional Info]]\nI will be interfacing to memcached primarily, with PHP and Python\nBTW - memcached is running on the same machine (so physical address issues should not arise).","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":150,"Q_Id":7783860,"Users Score":0,"Answer":"Both languages support database connections which live beyond the lifetime of a single request. Don't use memcache for that!","Q_Score":0,"Tags":"php,python,memcached","A_Id":7785856,"CreationDate":"2011-10-16T11:03:00.000","Title":"Is it safe to store a connection (effectively a pointer) in memcache?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am using memcached on a web site, and I am currently needing to open connections to a database and socket each time a function is called. In the case of the db connection, I am having to decide at runtime, which database to connect to.\nBecause of the (default) stateless nature of web apps, I am having to tear down (i.e. close) the connection after each function call. I am wondering if it is possible to store (i.e. cache) the socket connection and the database connections in memcache - do that I have a pool of db connections and a socket connection already open that I can use whenever the function is called.\nIs this safe ? \n[[Additional Info]]\nI will be interfacing to memcached primarily, with PHP and Python\nBTW - memcached is running on the same machine (so physical address issues should not arise).","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":150,"Q_Id":7783860,"Users Score":0,"Answer":"I am wondering if it is possible to store (i.e. cache) the socket connection and the database connections in memcache \n\nNo.","Q_Score":0,"Tags":"php,python,memcached","A_Id":7785929,"CreationDate":"2011-10-16T11:03:00.000","Title":"Is it safe to store a connection (effectively a pointer) in memcache?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am building a web application that allows a user to upload an image. When the image is uploaded, it needs to be resized to one or more sizes, each of which needs to be sent to Amazon s3 for storage. Metadata and urls for each size of the image are stored in a single database record on the web server. I'm using a message queue to perform the resizing and uploading asynchronously (as there is potential for large images and multiple resizes per request). When the resize\/upload task completes, the database record needs to be updated with the url. \nMy problem is that the worker executing the task will not have access to the database. I was thinking of firing off a http callback from the worker back to the web application after the task is complete with the appropriate information for updating the database record. Are there any other alternatives or reasons I should do this another way?\nI'm using python\/pylons for the web backend, mysql for the database and celery\/amqp for messaging.\nThanks!","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":639,"Q_Id":7802504,"Users Score":2,"Answer":"It seems that your goal is not to decouple the database from the MQ, but rather from the workers. As such, you can create another queue that receives completion notifications, and have another single worker that picks up the notifications and updates the database appropriately.","Q_Score":0,"Tags":"python,database,pylons,message-queue,celery","A_Id":7802664,"CreationDate":"2011-10-18T04:41:00.000","Title":"Best practice for decoupling a database from a message queue","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I use Berkeley DB(BDB) in nginx.  When a request arrives, nginx passes the URI as a key to BDB and checks if that key has a value in BDB file.\nI actually did in an example. I add some data in BDB, and run nginx, it's OK. I can access it.\nBut when I add some data in running BDB with nginx (using Python), I can't get the new data.  Even I use the another python interpreter access the BDB file, it was actually has the new data. \nSteps of the request in nginx:\n\nstart up nginx, and it will init my plugin (BDB env and init)\na request comes in\ncontrol in plugin, check if key(uri) has a value.  If true, return it, or pass\n...rest of process","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":237,"Q_Id":7817567,"Users Score":1,"Answer":"it supports\n\nA Single Process With One Thread\nA Single Process With Multiple Threads\nGroups of Cooperating Processes\nGroups of Unrelated Processes","Q_Score":1,"Tags":"python,nginx,berkeley-db","A_Id":8835081,"CreationDate":"2011-10-19T06:52:00.000","Title":"Does Berkeley DB only support one processor operation","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":0},{"Question":"Is there way to execute DDL script from Python with kinterbasdb library for Firebird database?\nBasically I'd like to replicate 'isql -i myscript.sql' command.","AnswerCount":1,"Available Count":1,"Score":0.3799489623,"is_accepted":false,"ViewCount":412,"Q_Id":7825066,"Users Score":2,"Answer":"It has been a while since I used kinterbasdb, but as far as I know you should be able to do this with any query command which can also be used for INSERT, UPDATE and DELETE (ie nothing that produces a resultset). So Connection.execute_immediate and Cursor.execute should work.\nDid you actually try this.\nBTW: With Firebird it is advisable not to mix DDL and DML in one transaction.\nEDIT:\nI just realised that you might have meant a full DDL script with multiple statements, if that is what you mean, then: no you cannot, you need to execute each statement individually.\nYou might be able to use an EXECUTE BLOCK statement, but you may need to modify your script so much that it would be easier to simply try to split the actual script into individual statements.","Q_Score":1,"Tags":"python,firebird,ddl,kinterbasdb","A_Id":7832347,"CreationDate":"2011-10-19T16:58:00.000","Title":"How to run DDL script with kinterbasdb","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm very new to Python and I'm trying to write a sort of recipe organizer to get acquainted with the language.  Basically, I am unsure how how I should be storing the recipes.\nFor now, the information I want to store is: \n\nRecipe name\nIngredient names\nIngredient quantities\nPreparation\n\nI've been thinking about how to do this with the built-in sqlite3, but I know nothing about database architecture, and haven't been able to find a good reference.\nI suppose one table would contain recipe names and primary keys.  Preparation could be in a different table with the primary key as well.  Would each ingredient\/quantity pair need its own table.  \nIn other words, there would be a table for ingredientNumberOne, and each recipe's first ingredient, with the quantity, would go in there.  Then each time recipe comes along with more ingredients than there are tables, a new table would be created. \nAm I even correct in assuming that sqlite3 is sufficient for this task?","AnswerCount":4,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":2639,"Q_Id":7827859,"Users Score":2,"Answer":"Just a general data modeling concept:  you never want to name anything \"...NumberOne\", \"...NumberTwo\".  Data models designed in this way are very difficult to query.  You'll ultimately need to visit each of N tables for 1 to N ingredients.  Also, each table in the model would ultimately have the same fields making maintenance a nightmare.  \nRather, just have one ingredient table that references the \"recipe\" table.  \nUltimately, I just realized this doesn't exactly answer the question, but you could implement this solution in Sqlite.  I just get worried when good developers start introducing bad patterns into the data model.  This comes from a guy who's been on both sides of the coin.","Q_Score":0,"Tags":"python,database,database-design","A_Id":7827955,"CreationDate":"2011-10-19T20:42:00.000","Title":"How to store recipe information with Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I created a simple bookmarking app using django which uses sqlite3 as the database backend.\nCan I upload it to appengine and use it? What is \"Django-nonrel\"?","AnswerCount":1,"Available Count":1,"Score":0.761594156,"is_accepted":false,"ViewCount":582,"Q_Id":7838667,"Users Score":5,"Answer":"Unfortunately, no you can't. Google App Engine does not allow you to write files, and that is needed by SQLite.\nUntil recently, it had no support of SQL at all, preferring a home-grown solution (see the \"CAP theorem\" as for why). This motivated the creation of projects like \"Django-nonrel\" which is a version of Django that does not require a relational database.\nRecently, they opened a beta service that proposes a MySQL database. But beware that it is fundamentally less reliable, and that it is probably going to be expensive.\nEDIT: As Nick Johnson observed, this new service (Google Cloud SQL) is fundamentally less scalable, but not fundamentally less reliable.","Q_Score":3,"Tags":"python,django,google-app-engine,web-applications,sqlite","A_Id":7838935,"CreationDate":"2011-10-20T15:52:00.000","Title":"Can I deploy a django app which uses sqlite3 as backend on google app engine?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I am using GeoDjango with PostGIS. Then I am into trouble on how to get the nearest record from the given coordinates from my postgres db table.","AnswerCount":6,"Available Count":1,"Score":0.0665680765,"is_accepted":false,"ViewCount":5401,"Q_Id":7846355,"Users Score":2,"Answer":"I have no experience with GeoDjango, but on PostgreSQL\/PostGIS you have the st_distance(..) function. So, you can order your results by st_distance(geom_column, your_coordinates) asc and see what are the nearest rows.\nIf you have plain coordinates (no postgis geometry), you can convert your coordinates to a point with the geometryFromText function.\nIs that what you were looking for? If not, try to be more explicit.","Q_Score":13,"Tags":"python,postgresql,postgis,geodjango","A_Id":7904142,"CreationDate":"2011-10-21T07:36:00.000","Title":"How can I query the nearest record in a given coordinates(latitude and longitude of string type)?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"What's the best combination of tools to import daily data feed (in .CSV format) to a MSSQL server table?\nEnvironment and acceptable tools:\n - Windows 2000\/XP\n - ruby or python\nMS SQL Server is on a remote server, the importing process has to be done on a Windows client machine.","AnswerCount":4,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":3142,"Q_Id":7847818,"Users Score":0,"Answer":"And what about DTS services? It's integral part of MS SQL server starting with early versions and it allows you to import text-based data to server tables","Q_Score":0,"Tags":"python,sql-server,ruby,windows,csv","A_Id":7847885,"CreationDate":"2011-10-21T10:00:00.000","Title":"Import CSV to MS SQL Server programmatically","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'd like to open the chromium site data (in ~\/.config\/chromium\/Default) with python-sqlite3 but it gets locked whenever chromium is running, which is understandable since transactions may be made. Is there a way to open it in read-only mode, ensuring that I can't corrupt the integrity of the db while chromium is using it?","AnswerCount":3,"Available Count":1,"Score":1.0,"is_accepted":false,"ViewCount":7130,"Q_Id":7857755,"Users Score":6,"Answer":"Chromium is holding a database lock for long periods of time? Yuck! That's really not a very good idea at all. Still, not your fault\u2026\nYou could try just copying the database file (e.g., with the system utility cp) and using that snapshot for reading purposes; SQLite keeps all its committed state in a single file per database. Yes, there's a chance of seeing a partial transaction, but you will definitely not have lock problems on Unix as SQLite definitely doesn't use mandatory locks. (This might well not work on Windows due to the different locking scheme there.)","Q_Score":15,"Tags":"python,database,sqlite","A_Id":7857866,"CreationDate":"2011-10-22T06:05:00.000","Title":"Is it possible to open a locked sqlite database in read only mode?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"This is what I have :-\n\nUbuntu 11.10.\nDjango 1.3 \nPython 2.7\n\nWhat I want to do is build an app that is similar to top-coder and I have the skeletal version of the app sketched out. The basic requirements would be:-\n1. Saving the code. \n2. Saving the user name and ranks.(User-profile)\n3. Should allow a teacher to create multiple choice questions too.( Similar to Google docs). \nI have basic knowledge of Django and have built couple of (basic) apps before. Rather than building an online tool, is it possible to build something very similar to conf2py that sits on top of web2py, in Django. \nLets call this small project examPy( I know, very original), is it possible to build an app that acts more a plug-in to Django or is my concept of Django absolutely wrong? \nThe primary question being:\nAs I want to learn a new DB and have worked on postgres in Django, should I chose CouchDB or MongoDB for Django? \nAnswers can be explanations or links to certain documentations or blogs that can tell me the pros and cons.","AnswerCount":3,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":2560,"Q_Id":7859775,"Users Score":3,"Answer":"I've used mongo-engine with Django but you need to create a file specifically for Mongo documents eg. Mongo_models.py. In that file you define your Mongo documents. You then create forms to match each Mongo document. Each form has a save method which inserts or updates whats stored in Mongo. Django forms are designed to plug into any data back end ( with a bit of craft ). \nIf you go this route you can dodge Django non-rel which is still not part of Django 1.4. In addition I believe django-nonrel is on hiatus right now.\nI've used both CouchDB and Mongo extensively.  CouchDB has a lovely interface.  My colleague is working on something similar for Mongo.  Mongo's map and reduce are far faster than CouchDB.  Mongo is more responsive loading and retrieving data.  The python libraries for Mongo are easier to get working with ( both pymongo and mongo-engine are excellent )\nBe sure you read the Mongo production recommendations!  Do not run one instance on the same node as Django or prepare to be savagely burned when traffic peaks.  Mondo works great with Memcache\/Redis where one can store reduced data for rapid lookups.\nBEWARE: If you have very well defined and structured data that can be described in documents or models then don't use Mongo. Its not designed for that and something like PostGreSQL will work much better.\n\nI use PostGreSQL for relational or well structured data because its good for that. Small memory footprint and good response.\nI use Redis to cache or operate in memory queues\/lists because its very good for that. great performance providing you have the memory to cope with it.\nI use Mongo to store large JSON documents and to perform Map and reduce on them ( if needed ) because its very good for that. Be sure to use indexing on certain columns if you can to speed up lookups.\n\nDon't use a circle to fill a square hole. It won't fill it.","Q_Score":3,"Tags":"python,django,mongodb,couchdb","A_Id":10204764,"CreationDate":"2011-10-22T13:09:00.000","Title":"Mongo DB or Couch DB with django for building an app that is similar to top coder?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"There seems to be many choices for Python to interface with SQLite (sqlite3, atpy) and HDF5 (h5py, pyTables) -- I wonder if anyone has experience using these together with numpy arrays or data tables (structured\/record arrays), and which of these most seamlessly integrate with \"scientific\" modules (numpy, scipy) for each data format (SQLite and HDF5).","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":3647,"Q_Id":7883646,"Users Score":23,"Answer":"Most of it depends on your use case. \nI have a lot more experience dealing with the various HDF5-based methods than traditional relational databases, so I can't comment too much on SQLite libraries for python...\nAt least as far as h5py vs pyTables, they both offer very seamless access via numpy arrays, but they're oriented towards very different use cases.\nIf you have n-dimensional data that you want to quickly access an arbitrary index-based slice of, then it's much more simple to use h5py.  If you have data that's more table-like, and you want to query it, then pyTables is a much better option.\nh5py is a relatively \"vanilla\" wrapper around the HDF5 libraries compared to pyTables.  This is a very good thing if you're going to be regularly accessing your HDF file from another language (pyTables adds some extra metadata).  h5py can do a lot, but for some use cases (e.g. what pyTables does) you're going to need to spend more time tweaking things.  \npyTables has some really nice features.  However, if your data doesn't look much like a table, then it's probably not the best option.\nTo give a more concrete example, I work a lot with fairly large (tens of GB) 3 and 4 dimensional arrays of data.  They're homogenous arrays of floats, ints, uint8s, etc.  I usually want to access a small subset of the entire dataset.  h5py makes this very simple, and does a fairly good job of auto-guessing a reasonable chunk size.  Grabbing an arbitrary chunk or slice from disk is much, much faster than for a simple memmapped file. (Emphasis on arbitrary... Obviously, if you want to grab an entire \"X\" slice, then a C-ordered memmapped array is impossible to beat, as all the data in an \"X\" slice are adjacent on disk.)  \nAs a counter example, my wife collects data from a wide array of sensors that sample at minute to second intervals over several years. She needs to store and run arbitrary querys (and relatively simple calculations) on her data.  pyTables makes this use case very easy and fast, and still has some advantages over traditional relational databases. (Particularly in terms of disk usage and speed at which a large (index-based) chunk of data can be read into memory)","Q_Score":12,"Tags":"python,sqlite,numpy,scipy,hdf5","A_Id":7891137,"CreationDate":"2011-10-25T01:06:00.000","Title":"exporting from\/importing to numpy, scipy in SQLite and HDF5 formats","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have two List. first list element Name Age Sex and second list element test 10 female. I want to insert this data into database. In first list having MySQL Column and in second  MySQL Column Values.I'm trying to make this query. INSERT INTO (LIST1) VALUES (List2) =>INSERT INTO table (name,age,sex) values (test,10,female) Is it possible? thanks","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":77,"Q_Id":7886024,"Users Score":0,"Answer":"Try getting this to work using the MySQL gui. Once that works properly, then you can try to get it to work with Python using the SQL statements that worked in MySQL.","Q_Score":0,"Tags":"python","A_Id":7886073,"CreationDate":"2011-10-25T07:32:00.000","Title":"related to List (want to insert into database)","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"The most common SQLite interface I've seen in Python is sqlite3, but is there anything that works well with NumPy arrays or recarrays? By that I mean one that recognizes data types and  does not require inserting row by row, and extracts into a NumPy (rec)array...? Kind of like R's SQL functions in the RDB or sqldf libraries, if anyone is familiar with those (they import\/export\/append whole tables or subsets of tables to or from R data tables).","AnswerCount":4,"Available Count":1,"Score":0.049958375,"is_accepted":false,"ViewCount":7905,"Q_Id":7901853,"Users Score":1,"Answer":"This looks a bit older but is there any reason you cannot just do a fetchall() instead of iterating and then just initializing numpy on declaration?","Q_Score":6,"Tags":"python,arrays,sqlite,numpy,scipy","A_Id":12100118,"CreationDate":"2011-10-26T11:15:00.000","Title":"NumPy arrays with SQLite","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am running Ubuntu, Flask 0.8, mod_wsgi 3 and apache2.  When an error occurs, I am unable to get Flask's custom 500 error page to trigger (and not the debug mode output either).  It works fine when I run it without WSGI via app.run(debug=True).\nI've tried setting WSGIErrorOverride to both On and Off in apache settings but same result.\nAnyone has gotten this issue?  Thanks!","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":873,"Q_Id":7940745,"Users Score":1,"Answer":"Are you sure the error is actually coming from Flask if you are getting a generic Apache 500 error page? You should look in the Apache error log to see what error messages are in there first. The problem could be configuration or your WSGI script file being wrong or failing due to wrong sys.path etc.","Q_Score":2,"Tags":"python,apache,wsgi,flask","A_Id":7942317,"CreationDate":"2011-10-29T18:13:00.000","Title":"Using Python Flask, mod_wsgi, apache2 - unable to get custom 500 error page","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm create a blog using django.\nI'm getting an 'operational error: FATAL: role \"[database user]\" does not exist.\nBut i have not created any database yet, all i have done is filled in the database details in setting.py.\nDo i have to create a database using psycopg2? If so, how do i do it? \nIs it:\npython\n\n\n\nimport psycopg2\n      psycopg2.connect(\"dbname=[name] user=[user]\")\n\n\n\nThanks in advance.","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":1391,"Q_Id":7941623,"Users Score":0,"Answer":"Generally, you would create the database externally before trying to hook it up with Django.\nIs this your private server?  If so, there are command-line tools you can use to set up a PostgreSQL user and create a database.\nIf it is a shared hosting situation, you would use CPanel or whatever utility your host provides to do this.  For example, when I had shared hosting, I was issued a database user and password by the hosting administrator.  Perhaps you were too.\nOnce you have this set up, there are places in your settings.py file to put your username and password credentials, and the name of the database.","Q_Score":0,"Tags":"python,database,django,psycopg2","A_Id":7942855,"CreationDate":"2011-10-29T20:52:00.000","Title":"how do i create a database in psycopg2 and do i need to?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm create a blog using django.\nI'm getting an 'operational error: FATAL: role \"[database user]\" does not exist.\nBut i have not created any database yet, all i have done is filled in the database details in setting.py.\nDo i have to create a database using psycopg2? If so, how do i do it? \nIs it:\npython\n\n\n\nimport psycopg2\n      psycopg2.connect(\"dbname=[name] user=[user]\")\n\n\n\nThanks in advance.","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":1391,"Q_Id":7941623,"Users Score":0,"Answer":"before connecting to database, you need to create database, add user,  setup access for user you selected. \nReffer to installation\/configuration guides for Postgres.","Q_Score":0,"Tags":"python,database,django,psycopg2","A_Id":7941712,"CreationDate":"2011-10-29T20:52:00.000","Title":"how do i create a database in psycopg2 and do i need to?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Does a canonical user id exist for a federated user created using STS?  When using boto I need a canonical user id to grant permissions to a bucket.  \nHere's a quick tour through my code:\n\nI've successfully created temporary credentials using boto's STS module (using a \"master\" account), and this gives me back:\n\nfederated_user_arn\nfederated_user_id\npacked_policy_size\naccess_key\nsecret_key\nsession_token\nexpiration\n\nThen I create the bucket using boto:\nbucket = self.s3_connection.create_bucket('%s_store' % (app_id))\nNow I want to grant permissions I'm left with two choices in boto:\nadd_email_grant(permission, email_address, recursive=False, headers=None)\nadd_user_grant(permission, user_id, recursive=False, headers=None, display_name=None)\n\nThe first method isn't an option since there isn't an email attached to the federated user, so I look at the second.  Here the second parameter (\"userid\") is to be \"The canonical user id associated with the AWS account your are granting the permission to.\" But I can't seem to find a way to come with this for the federated user.\nDo canonical user ids even exist for federated users?  Am I overlooking an easier way to grant permissions to federated users?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":718,"Q_Id":8032576,"Users Score":1,"Answer":"Contacted the author of boto and learned of:\nget_canonical_user_id() for the S3Connection class.\nThis will give you the canonical user ID for the credentials associated with the connection.  The connection will have to have been used for some operation (e.g.: listing buckets).\nVery awkward, but possible.","Q_Score":2,"Tags":"python,amazon-s3,amazon-web-services,boto,amazon-iam","A_Id":8074814,"CreationDate":"2011-11-07T03:57:00.000","Title":"Do AWS Canonical UserIDs exist for AWS Federated Users (temporary security credentials)?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I store several properties of objects in hashsets. Among other things, something like \"creation date\". There are several hashsets in the db.\nSo, my question is, how can I find all objects older than a week for example? Can you suggest an algorithm what faster than O(n) (naive implementation)?\nThanks,\nOles","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":462,"Q_Id":8039566,"Users Score":2,"Answer":"My initial thought would be to store the data elsewhere, like relational database, or possibly using a zset.\nIf you had continuous data (meaning it was consistently set at N interval time periods), then you could store the hash key as the member and the date (as a int timestamp) as the value.  Then you could do a zrank for a particular date, and use zrevrange to query from the first rank to the value you get from zrank.","Q_Score":1,"Tags":"python,redis","A_Id":8039797,"CreationDate":"2011-11-07T16:37:00.000","Title":"Redis: find all objects older than","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am running several thousand python processes on multiple servers which go off, lookup a website, do some analysis and then write the results to a central MySQL database.\nIt all works fine for about 8 hours and then my scripts start to wait for a MySQL connection.\nOn checking top it's clear that the MySQL daemon is overloaded as it is using up to 90% of most of the CPUs.\nWhen I stop all my scripts, MySQL continues to use resources for some time afterwards.\nI assume it is still updating the indexes? - If so, is there anyway of determining which indexes it is working on, or if not what it is actually doing?\nMany thanks in advance.","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":197,"Q_Id":8048742,"Users Score":0,"Answer":"There are a lot of tweaks that can be done to improve the performance of MySQL. Given your workload, you would probably benefit a lot from mysql 5.5 and higher, which improved performance on multiprocessor machines. Is the machine in question hitting VM? if it is paging out, then the performance of mysql will be horrible. \nMy suggestions:\n\ncheck version of mysql. If possible, get the latest 5.5 version.\nLook at the config files for mysql called my.cnf. Make sure that it makes sense on your machine. There are example config files for small, medium, large, etc machines to run MySQL. I think the default setup is for a machine with < 1 Gig of ram. \nAs the other answer suggests, turn on slow query logging.","Q_Score":1,"Tags":"python,mysql,linux,indexing","A_Id":9198763,"CreationDate":"2011-11-08T10:06:00.000","Title":"Python processes and MySQL","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"sorry, but does this make sense? the ORM means: Object Relational Mapper, and here, there is Relational, and NoSql is not RDBMS! so why the use of an ORM in a NoSql solution? because i see updates of ORMs for Python!","AnswerCount":3,"Available Count":3,"Score":0.1973753202,"is_accepted":false,"ViewCount":4264,"Q_Id":8051614,"Users Score":3,"Answer":"Interesting question. Although NoSQL databases do not have a mechanism to identify relationships, it does not mean that there are no logical relationships between the data that you are storing. Most of the time, you are handling & enforcing those relationships in code manually if you're using a NoSQL database.\nHence, I feel that ORMs can still help you here. If you do have data that is related, but need to use a NoSQL database, an ORM can still help you in maintaining clean data.\nFor Example, I use Amazon SimpleDB for the lower cost, but my data still has relationships, which need to be maintained. Currently, I'm doing that manually. Maybe an ORM would help me as well.","Q_Score":8,"Tags":"python,orm,mongodb","A_Id":8051721,"CreationDate":"2011-11-08T14:03:00.000","Title":"why the use of an ORM with NoSql (like MongoDB)","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"sorry, but does this make sense? the ORM means: Object Relational Mapper, and here, there is Relational, and NoSql is not RDBMS! so why the use of an ORM in a NoSql solution? because i see updates of ORMs for Python!","AnswerCount":3,"Available Count":3,"Score":0.1325487884,"is_accepted":false,"ViewCount":4264,"Q_Id":8051614,"Users Score":2,"Answer":"ORM is an abstraction layer. Switching to a different engine is much easier when the queries are abstracted away, and hidden behind a common interface (it doesn't always work that well in practice, but it's still easier than without).","Q_Score":8,"Tags":"python,orm,mongodb","A_Id":8051652,"CreationDate":"2011-11-08T14:03:00.000","Title":"why the use of an ORM with NoSql (like MongoDB)","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"sorry, but does this make sense? the ORM means: Object Relational Mapper, and here, there is Relational, and NoSql is not RDBMS! so why the use of an ORM in a NoSql solution? because i see updates of ORMs for Python!","AnswerCount":3,"Available Count":3,"Score":1.2,"is_accepted":true,"ViewCount":4264,"Q_Id":8051614,"Users Score":13,"Answer":"Firstly, they are not ORM (since they don't have any relations among them), they are ODM (Object Document Mapper)\nMain usage of these ODM frameworks here same as the some common feature of ORM, thus \n\nproviding the abstraction over your data model. you can have your data modelled in your application irrespective of the target software. \nMost ODM's build to leverage the existing language features and use the familiar pattern to manipulate data instead to learn new language syntax's of the new software.\n\nWhen i use mongoid (Ruby ODM for mongo), i can query mongo the way i do it in active model (mostly).\nSince they don't have the relation among them, these ODM's provide the way to define the relations in your models and simulate the relationships. These are all abstracted from the developer so they can code the same way they do with the relational data.","Q_Score":8,"Tags":"python,orm,mongodb","A_Id":8051825,"CreationDate":"2011-11-08T14:03:00.000","Title":"why the use of an ORM with NoSql (like MongoDB)","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm thinking in create a webapplication with cakephp but consuming python's appengine webservice. But, to install cakephp etc, I need to configure the database. Appengine uses another kind of datastorage, with is different from mysql, etc.\nI was thinking in store the data in appengine, and using the python webservices, and with the cakephp application comunicating with the webservice, for insert and retrieve data.\nIs there any good resource for this, or is it unpossible.\nObs: also opened for a possibility for developing the webapplicaiton completely in python running in appengine. If anyone has a good resource.\nThanks.","AnswerCount":5,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":378,"Q_Id":8069649,"Users Score":0,"Answer":"You can not run PHP on GAE. If you run PHP somewhere, it is a bad architecture to go over the internet for your data. It will be slooooow and a nightmare to develop in.\nYou should store your data where you run your php, unless you must have a distributed, globally scaling architecture, which afaiu not the case.","Q_Score":0,"Tags":"php,python,google-app-engine,cakephp","A_Id":8070747,"CreationDate":"2011-11-09T18:21:00.000","Title":"Connect appengine with cakephp","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I am currently working on a pyramid system that uses sqlalchemy.\nThis system will include a model (let's call it Base) that is stored in a\ndatabase table. This model should be extensible by the user on runtime. Basically, the user\nshould be able to subclass the Base and create a new model (let's call this one 'Child').\nChilds should be stored in another database table.\nAll examples available seem to handle database reflection on a predefined model.\nWhat would be the best way to generate complete model classes via database reflection?","AnswerCount":4,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":1319,"Q_Id":8122078,"Users Score":4,"Answer":"This doesn't seem to have much to do with \"database reflection\", but rather dynamic table creation. This is a pretty dangerous operation and generally frowned upon.\nYou should try to think about how to model the possible structure your users would want to add to the Base and design your schema around that. Sometimes these flexible structures can benefit a lot from vertical tables when you don't know what the columns may be.\nDon't forget that there's an entire class of data storage systems out there that provide more flexible support for \"schemaless\" models. Something like Mongo or ZODB might make more sense here.","Q_Score":3,"Tags":"python,reflection,sqlalchemy,pyramid","A_Id":8125931,"CreationDate":"2011-11-14T13:09:00.000","Title":"Model Creation by SQLAlchemy database reflection","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"How can we remove the database name and username that appears on top left hand side corner in openERP window after openERP logo.In which file do we need to make changes to remove that.\nThanks,\nSameer","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":133,"Q_Id":8151033,"Users Score":0,"Answer":"It's in the openerp-web module. The location depends on your particular configuration. The relevant code can be found in the file addons\/web\/static\/src\/xml\/base.xml. Search for header_title and edit the contents of the h1 tag of that class.","Q_Score":0,"Tags":"python,openerp","A_Id":12295904,"CreationDate":"2011-11-16T11:37:00.000","Title":"Removing Database name and username from top Left hand side corner.","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I want to convert xlsx file to xls format using python. The reason is that im using xlrd library to parse xls files, but xlrd is not able to parse xlsx files.\nSwitching to a different library is not feasible for me at this stage, as the entire project is using xlrd, so a lot of changes will be required.\nSo, is there any way i can programatically convert an xlsx file to xls using python ?\nPlease Help\nThank You","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1806,"Q_Id":8151243,"Users Score":0,"Answer":"xlrd-0.9.2.tar.gz (md5) can extract data from Excel spreadsheets (.xls and .xlsx, versions 2.0 on-wards) on any platform.","Q_Score":0,"Tags":"python,excel,xls,xlsx,xlrd","A_Id":21996139,"CreationDate":"2011-11-16T11:54:00.000","Title":"xlrd library not working with xlsx files.any way to covert xlsx to xls using python?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"if I use cx_Oracle 5.0.4, I can connect from python console, and works under apache+django+mod_wsgi\nbut when I update cx_Oracle 5.1.1, I can connect from python console, BUT same code doesn't work under apache+django+mod_wsgi\nFile \"C:\\Python27\\lib\\site-packages\\django\\db\\backends\\oracle\\base.py\", line 24, in \n     raise ImproperlyConfigured(\"Error loading cx_Oracle module: %s\" % e)\n TemplateSyntaxError: Caught ImproperlyConfigured while rendering: Error loading cx_Oracle module: DLL load failed: The specified module could not be found. \nPS: python 2.7 \nPSS: I have instaled MSVC 2008 Redistributable x86","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":1227,"Q_Id":8151815,"Users Score":1,"Answer":"Need a solution as well.  \nI have the same setup on WinXP (Apache 2.2.21\/ mod_wsgi 3.3\/ python 2.7.2\/ cx_Oracle 5.x.x).  I found that cx_Oracle 5.1 also fails with the same error.  Only 5.0.4 works.  \nHere is the list of changes that were made from 5.0.4 to 5.1:\n\nRemove support for UNICODE mode and permit Unicode to be passed through in\neverywhere a string may be passed in. This means that strings will be\npassed through to Oracle using the value of the NLS_LANG environment\nvariable in Python 3.x as well. Doing this eliminated a bunch of problems\nthat were discovered by using UNICODE mode and also removed an unnecessary\nrestriction in Python 2.x that Unicode could not be used in connect strings\nor SQL statements, for example.\nAdded support for creating an empty object variable via a named type, the\nfirst step to adding full object support.\nAdded support for Python 3.2.\nAccount for lib64 used on x86_64 systems. Thanks to Alex Wood for supplying\nthe patch.\nClear up potential problems when calling cursor.close() ahead of the\ncursor being freed by going out of scope.\nAvoid compilation difficulties on AIX5 as OCIPing does not appear to be\navailable on that platform under Oracle 10g Release 2. Thanks to\nPierre-Yves Fontaniere for the patch.\nFree temporary LOBs prior to each fetch in order to avoid leaking them.\nThanks to Uwe Hoffmann for the initial patch.","Q_Score":1,"Tags":"python,apache,cx-oracle","A_Id":8158089,"CreationDate":"2011-11-16T12:36:00.000","Title":"cx_Oracle 5.1.1 under apache+mod_wsgi","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm working with SQLAlchemy for the first time and was wondering...generally speaking is it enough to rely on python's default equality semantics when working with SQLAlchemy vs id (primary key) equality?\nIn other projects I've worked on in the past using ORM technologies like Java's Hibernate, we'd always override .equals() to check for equality of an object's primary key\/id, but when I look back I'm not sure this was always necessary.\nIn most if not all cases I can think of, you only ever had one reference to a given object with a given id.  And that object was always the attached object so technically you'd be able to get away with reference equality.\nShort question: Should I be overriding eq() and hash() for my business entities when using SQLAlchemy?","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":4581,"Q_Id":8179068,"Users Score":1,"Answer":"I had a few situations where my sqlalchemy application would load multiple instances of the same object (multithreading\/ different sqlalchemy sessions  ...). It was absolutely necessary to override eq() for those objects or I would get various problems. This could be a problem in my application design, but it probably doesn't hurt to override eq() just to be sure.","Q_Score":11,"Tags":"python,sqlalchemy","A_Id":8179370,"CreationDate":"2011-11-18T07:24:00.000","Title":"sqlalchemy id equality vs reference equality","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Essentially I have a large database of transactions and I am writing a script that will take some personal information and match a person to all of their past transactions. \nSo I feed the script a name and it returns all of the transactions that it has decided belong to that customer.\nThe issue is that I have to do this for almost 30k people and the database has over 6 million transaction records.\nRunning this on one computer would obviously take a long time, I am willing to admit that the code could be optimized but I do not have time for that and I instead want to split the work over several computers.  Enter Celery:\nMy understanding of celery is that I will have a boss computer sending names to a worker computer which runs the script and puts the customer id in a column for each transaction it matches.\nWould there be a problem with multiple worker computers searching and writing to the same database?\nAlso, have I missed anything and\/or is this totally the wrong approach?\nThanks for the help.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":107,"Q_Id":8230617,"Users Score":2,"Answer":"No, there wouldn't be any problem multiple worker computers searching and writing to the same database since MySQL is designed to be able to handle this. Your approach is good.","Q_Score":2,"Tags":"python,mysql,celery","A_Id":8230713,"CreationDate":"2011-11-22T16:56:00.000","Title":"relatively new programmer interested in using Celery, is this the right approach","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":0},{"Question":"I'm currently trying to build and install the mySQLdb module for Python, but the command \npython setup.py build\ngives me the following error \nrunning build\nrunning build_py\ncopying MySQLdb\/release.py -> build\/lib.macosx-10.3-intel-2.7\/MySQLdb\nerror: could not delete 'build\/lib.macosx-10.3-intel-2.7\/MySQLdb\/release.py': Permission denied\nI verified that I'm a root user and when trying to execute the script using sudo, I then get a gcc-4.0 error: \nrunning build\nrunning build_py\ncopying MySQLdb\/release.py -> build\/lib.macosx-10.3-fat-2.7\/MySQLdb\nrunning build_ext\nbuilding '_mysql' extension\ngcc-4.0 -fno-strict-aliasing -fno-common -dynamic -g -O2 -DNDEBUG -g -O3 -Dversion_info=(1,2,3,'final',0) -D__version__=1.2.3 -I\/usr\/local\/mysql\/include -I\/Library\/Frameworks\/Python.framework\/Versions\/2.7\/include\/python2.7 -c _mysql.c -o build\/temp.macosx-10.3-fat-2.7\/_mysql.o -Os -g -fno-common -fno-strict-aliasing -arch x86_64\nunable to execute gcc-4.0: No such file or directory\nerror: command 'gcc-4.0' failed with exit status 1\nWhich is odd, because I'm using XCode 4 with Python 2.7. I've tried the easy_install and pip methods, both of which dont work and give me a permission denied error on release.py. I've chmodded that file to see if that was the problem but no luck. Thoughts?","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":912,"Q_Id":8236963,"Users Score":1,"Answer":"Make sure that gcc-4.0 is in your PATH. Also, you can create an alias from gcc to gcc-4.0.\nTake care about 32b and 64b versions. Mac OS X is a 64b operating system and you should right flags to make sure you're compiling for 64b architecture.","Q_Score":4,"Tags":"python,mysql,django,mysql-python","A_Id":8260644,"CreationDate":"2011-11-23T03:28:00.000","Title":"Errors When Installing MySQL-python module for Python 2.7","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":0},{"Question":"I have a SQL dump of a legacy DB, and a folder with images, and those are referenced by some rows of certain tables, and I need to migrate that data to the new Django models. The specific problem is how to \"perform\" the upload, but in a management command.\nWhen the table with the field referenced is migrated to it's corresponding model, I need to also set the image field of the model, and I also need to process the filename accordingly to the upload_to parameter for the ImageField.\nHow to programmatically populate the image field from a file path or a file descriptor?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":438,"Q_Id":8280859,"Users Score":0,"Answer":"One approach would be to create a utility django project specifying your legacy database in settings.py. Then use the inspectdb management command to create a django model representation of your legacy database. And finally use dumpdata to get you data in JSON format.\nYou could then finally make your own JSON script that inserts your old data in your new models.","Q_Score":1,"Tags":"python,django,data-migration,filefield","A_Id":8280938,"CreationDate":"2011-11-26T19:05:00.000","Title":"Migrate a legacy DB to Django, with image files","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Background: I am writing a matching script in python that will match records of a transaction in one database to names of customers in another database. The complexity is that names are not unique and can be represented multiple different ways from transaction to transaction.\nRather than doing multiple queries on the database (which is pretty slow) would it be faster to get all of the records where the last name (which in this case we will say never changes) is \"Smith\" and then have all of those records loaded into memory as you go though each looking for matches for a specific \"John Smith\" using various data points.\nWould this be faster, is it feasible in python, and if so does anyone have any recommendations for how to do it?","AnswerCount":3,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":98,"Q_Id":8299614,"Users Score":0,"Answer":"Your strategy is reasonable though I would first look at doing as much of the work as possible in the database query using LIKE and other SQL functions.  It should be possible to make a query that matches complex criteria.","Q_Score":0,"Tags":"python,mysql","A_Id":8299759,"CreationDate":"2011-11-28T17:14:00.000","Title":"Could someone give me their two cents on this optimization strategy","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Background: I am writing a matching script in python that will match records of a transaction in one database to names of customers in another database. The complexity is that names are not unique and can be represented multiple different ways from transaction to transaction.\nRather than doing multiple queries on the database (which is pretty slow) would it be faster to get all of the records where the last name (which in this case we will say never changes) is \"Smith\" and then have all of those records loaded into memory as you go though each looking for matches for a specific \"John Smith\" using various data points.\nWould this be faster, is it feasible in python, and if so does anyone have any recommendations for how to do it?","AnswerCount":3,"Available Count":2,"Score":0.1325487884,"is_accepted":false,"ViewCount":98,"Q_Id":8299614,"Users Score":2,"Answer":"Regarding: \"would this be faster:\"\nThe behind-the-scenes logistics of the SQL engine are really optimized for this sort of thing. You might need to create an SQL PROCEDURE or a fairly complex query, however.\nCaveat, if you're not particularly good at or fond of maintaining SQL, and this isn't a time-sensitive query, then you might be wasting programmer time over CPU\/IO time in getting it right.\nHowever, if this is something that runs often or is time-sensitive, you should almost certainly be building some kind of JOIN logic in SQL, passing in the appropriate values (possibly wildcards), and letting the database do the filtering in the relational data set, instead of collecting a larger number of \"wrong\" records and then filtering them out in procedural code.\nYou say the database is \"pretty slow.\" Is this because it's on a distant host, or because the tables aren't indexed for the types of searches you're doing? \u2026 If you're doing a complex query against columns that aren't indexed for it, that can be a pain; you can use various SQL tools including ANALYZE to see what might be slowing down a query. Most SQL GUI's will have some shortcuts for such things, as well.","Q_Score":0,"Tags":"python,mysql","A_Id":8299780,"CreationDate":"2011-11-28T17:14:00.000","Title":"Could someone give me their two cents on this optimization strategy","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am making an internal API in Python (pardon my terms) that provides a layer over MySQL and Solr (databases) with only simple computing. A Python program that spawns from scratch waits 80ms for Solr, while taking negligible time by itself. \nI am worried about the incomplete threading support of Python. So which of the modern Thrift servers allows high-performance request handling?\n\nIn Python, I could make a WSGI app under Apache workers that:\n\npooling resources such as DB connection objects\nhigh performance with minimum processes\ngraceful dropping of requests\n(relatively) graceful code reloading\na keep-alive mechanism (restart the application if it crashes)","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":1136,"Q_Id":8308610,"Users Score":1,"Answer":"Apparently TProcessPoolServer is a good server and forks different processes, avoiding threading issues.","Q_Score":1,"Tags":"python,thrift","A_Id":8842820,"CreationDate":"2011-11-29T09:42:00.000","Title":"Performance of TNonblockingServer, TThreadPoolServer for DB-bound server in Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"The idea is to make a script that would get stored procedure and udf contents (code) every hour (for example) and add it to SVN repo. As a result we have sql versioning control system.\nDoes anyone know how to backup stored procedure code using Python (sqlAlchemy, pyodbc or smth). \nI'v done this via C# before using SQL Management Objects.\nThanks in advance!","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":244,"Q_Id":8412636,"Users Score":1,"Answer":"There is no easy way to access SMO from Python (because there is no generic solution for accessing .NET from Python), so I would write a command-line tool in C# and call it from Python using the subprocess module. Perhaps you could do something with ctypes but I have no idea if that's feasible.\nBut, perhaps a more important question is why you want or need to do this. Does the structure of your database really change so often? If so, presumably you have no real control over it so what benefit does source control have in that scenario? How do you deploy database changes in the first place? Usually changes go from source control into production, not the other way around, so the 'master' source of DDL (including tables, indexes etc.) is SVN, not the database. But you haven't given much information about what you really need to achieve, so perhaps there is a good reason for needing to do this in your environment.","Q_Score":0,"Tags":"c#,python,sql-server,stored-procedures,smo","A_Id":8414549,"CreationDate":"2011-12-07T09:00:00.000","Title":"backup msSQL stored proc or UDF code via Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am parsing the USDA's food database and storing it in SQLite for query purposes.  Each food has associated with it the quantities of the same 162 nutrients.  It appears that the list of nutrients (name and units) has not changed in quite a while, and since this is a hobby project I don't expect to follow any sudden changes anyway.  But each food does have a unique quantity associated with each nutrient.\nSo, how does one go about storing this kind of information sanely.  My priorities are multi-programming language friendly (Python and C++ having preference), sanity for me as coder, and ease of retrieving nutrient sets to sum or plot over time.\nThe two things that I had thought of so far were 162 columns (which I'm not particularly fond of, but it does make the queries simpler), or a food table that has a link to a nutrient_list table that then links to a static table with the nutrient name and units.  The second seems more flexible i ncase my expectations are wrong, but I wouldn't even know where to begin on writing the queries for sums and time series.\nThanks","AnswerCount":2,"Available Count":1,"Score":0.3799489623,"is_accepted":false,"ViewCount":373,"Q_Id":8431451,"Users Score":4,"Answer":"Use the second (more normalized) approach.\nYou could even get away with fewer tables than you mentioned:\n\ntblNutrients\n-- NutrientID\n-- NutrientName\n-- NutrientUOM (unit of measure)\n-- Otherstuff  \ntblFood\n-- FoodId\n-- FoodName\n-- Otherstuff  \ntblFoodNutrients\n-- FoodID (FK)\n-- NutrientID (FK)\n-- UOMCount   \n\nIt will be a nightmare to maintain a 160+ field database.\nIf there is a time element involved too (can measurements change?) then you could add a date field to the nutrient and\/or the foodnutrient table depending on what could change.","Q_Score":2,"Tags":"c++,python,sql,sqlite","A_Id":8431705,"CreationDate":"2011-12-08T13:07:00.000","Title":"How to store data with large number (constant) of properties in SQL","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a question about making the decision whether to use MySQL database or Mongo database, the problem with my decision is that I am highly depending on these things:\n\nI want to select records between two dates (period)\n\nHowever is this possible?\nMy Application won't do any complex queries, just basic crud. It has Facebook integration so sometimes I got to JOIN the users table at the current setup.","AnswerCount":3,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":295,"Q_Id":8437213,"Users Score":1,"Answer":"MySQL(SQL) or MongoDB(NoSQL), both can work for your needs. but idea behind using RDBMS\/NoSQL is the requirement of your application  \n\nif your application care about speed and no relation between the data is necessary and your data schema changes very frequently, you can choose MongoDB, faster since no joins needed, every data is a stored as document  \nelse, go for MySQL","Q_Score":1,"Tags":"mysql,mongodb,mysql-python","A_Id":8437321,"CreationDate":"2011-12-08T20:25:00.000","Title":"MongoDB or MySQL database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a question about making the decision whether to use MySQL database or Mongo database, the problem with my decision is that I am highly depending on these things:\n\nI want to select records between two dates (period)\n\nHowever is this possible?\nMy Application won't do any complex queries, just basic crud. It has Facebook integration so sometimes I got to JOIN the users table at the current setup.","AnswerCount":3,"Available Count":2,"Score":0.1973753202,"is_accepted":false,"ViewCount":295,"Q_Id":8437213,"Users Score":3,"Answer":"Either DB will allow you to filter between dates and I wouldn't use that requirement to make the decision. Some questions you should answer: \n\nDo you need to store your data in a relational system, like MySQL? Relational databases are better at cross entity joining.\nWill your data be very complicated, but you will only make simple queries (e.g. by an ID), if so MongoDB may be a better fit as storing and retrieving complex data is a cinch.\nWho and where will you be querying the data from? MySql uses SQL for querying, which is a much more well known skill than mongo's JSON query syntax.\n\nThese are just three questions to ask. In order to make a recommendation, we'll need to know more about your application?","Q_Score":1,"Tags":"mysql,mongodb,mysql-python","A_Id":8437280,"CreationDate":"2011-12-08T20:25:00.000","Title":"MongoDB or MySQL database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm looking for a flat-file, portable key-value store in Python. I'll be using strings for keys and either strings or lists for values. I looked at ZODB but I'd like something which is more widely used and is more actively developed. Do any of the dmb modules in Python require system libraries or a database server (like mysql or the likes) or can I write to file with any of them?\nIf a dbm does not support a python lists, I imagine that I can just serialize it?","AnswerCount":4,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":4198,"Q_Id":8528001,"Users Score":2,"Answer":"You can look at the shelve module.  It uses pickle under the hood, and allows you to create a key-value look up that persists between launches.\nAdditionally, the json module with dump and load methods would probably work pretty well as well.","Q_Score":2,"Tags":"python","A_Id":8528030,"CreationDate":"2011-12-15T23:22:00.000","Title":"Flat file key-value store in python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm user of a Python application that has poorly indexed tables and was wondering if it's possible to improve performance by converting the SQLite database into an in-memory database upon application startup. My thinking is that it would minimize the issue of full table scans, especially since SQLite might be creating autoindexes, as the documentation says that is enabled by default. How can this be accomplished using the SQLAlchemy ORM (that is what the application uses)?","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":1450,"Q_Id":8549326,"Users Score":0,"Answer":"Whenever you set a variable in Python you are instantiating an object.  This means you are allocating memory for  it.\nWhen you query sqlite you are simply reading information off the disk into memory.\nsqlalchemy is simply an abstraction.  You read the data from disk into memory in the same way, by querying the database and setting the returned data to a variable.","Q_Score":2,"Tags":"python,sqlite,sqlalchemy","A_Id":8549565,"CreationDate":"2011-12-18T01:59:00.000","Title":"Is it possible to read a SQLite database into memory with SQLAlchemy?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm user of a Python application that has poorly indexed tables and was wondering if it's possible to improve performance by converting the SQLite database into an in-memory database upon application startup. My thinking is that it would minimize the issue of full table scans, especially since SQLite might be creating autoindexes, as the documentation says that is enabled by default. How can this be accomplished using the SQLAlchemy ORM (that is what the application uses)?","AnswerCount":2,"Available Count":2,"Score":0.0996679946,"is_accepted":false,"ViewCount":1450,"Q_Id":8549326,"Users Score":1,"Answer":"At the start of the program, move the database file to a ramdisk, point SQLAlchemy to it and do your processing, and then move the SQLite file back to non-volatile storage.\nIt's not a great solution, but it'll help you determine whether caching your database in memory is worthwhile.","Q_Score":2,"Tags":"python,sqlite,sqlalchemy","A_Id":10002601,"CreationDate":"2011-12-18T01:59:00.000","Title":"Is it possible to read a SQLite database into memory with SQLAlchemy?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I've been learning python by building a webapp on google app engine over the past five or six months. I also just finished taking a databases class this semester where I learned about views, and their benefits.\nIs there an equivalent with the GAE datastore using python?","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":106,"Q_Id":8570066,"Users Score":5,"Answer":"Read-only views (the most common type) are basically queries against one or more tables to present the illusion of new tables. If you took a college-level database course, you probably learned about relational databases, and I'm guessing you're looking for something like relational views.\nThe short answer is No.\nThe GAE datastore is non-relational. It doesn't have tables. It's essentially a very large distributed hash table that uses composite keys to present the (very useful) illusion of Entities, which are easy at first glance to mistake for rows in a relational database.\nThe longer answer depends on what you'd do if you had a view.","Q_Score":2,"Tags":"python,sql,google-app-engine","A_Id":8570245,"CreationDate":"2011-12-20T02:21:00.000","Title":"Is there an equivalent of a SQL View in Google App Engine Python?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I am writing a quick and dirty script which requires interaction with a database (PG).\nThe script is a pragmatic, tactical solution to an existing problem. however, I envisage that the script will evolve over time into a more \"refined\" system. Given the fact that it is currently being put together very quickly (i.e. I don't have the time to pour over huge reams of documentation), I am tempted to go the quick and dirty route, using psycopg.\nThe advantages for psycopg2 (as I currently understand it) is that:\n\nwritten in C, so faster than sqlAlchemy (written in Python)?\nNo abstraction layer over the DBAPI since works with one db and one db only (implication -> fast)\n(For now), I don't need an ORM, so I can directly execute my SQL statements without having to learn a new ORM syntax (i.e. lightweight)\n\nDisadvantages:\n\nI KNOW that I will want an ORM further down the line\npsycopg2 is (\"dated\"?) - don't know how long it will remain around for\n\nAre my perceptions of SqlAlchemy (slow\/interpreted, bloated, steep learning curve) true - IS there anyway I can use sqlAlchemy in the \"rough and ready\" way I want to use psycopg - namely:\n\nexecute SQL statements directly without having to mess about with the ORM layer, etc.\n\nAny examples of doing this available?","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":40683,"Q_Id":8588126,"Users Score":108,"Answer":"SQLAlchemy is a ORM, psycopg2 is a database driver. These are completely different things:  SQLAlchemy generates SQL statements and psycopg2 sends SQL statements to the database. SQLAlchemy depends on psycopg2 or other database drivers to communicate with the database!\nAs a rather complex software layer SQLAlchemy does add some overhead but it also is a huge boost to development speed, at least once you learned the library. SQLAlchemy is a excellent library and will teach you the whole ORM concept, but if you don't want to generate SQL statements to begin with then you don't want SQLAlchemy.","Q_Score":57,"Tags":"python,postgresql,sqlalchemy,psycopg2","A_Id":8588766,"CreationDate":"2011-12-21T10:08:00.000","Title":"SQLAlchemy or psycopg2?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am writing a quick and dirty script which requires interaction with a database (PG).\nThe script is a pragmatic, tactical solution to an existing problem. however, I envisage that the script will evolve over time into a more \"refined\" system. Given the fact that it is currently being put together very quickly (i.e. I don't have the time to pour over huge reams of documentation), I am tempted to go the quick and dirty route, using psycopg.\nThe advantages for psycopg2 (as I currently understand it) is that:\n\nwritten in C, so faster than sqlAlchemy (written in Python)?\nNo abstraction layer over the DBAPI since works with one db and one db only (implication -> fast)\n(For now), I don't need an ORM, so I can directly execute my SQL statements without having to learn a new ORM syntax (i.e. lightweight)\n\nDisadvantages:\n\nI KNOW that I will want an ORM further down the line\npsycopg2 is (\"dated\"?) - don't know how long it will remain around for\n\nAre my perceptions of SqlAlchemy (slow\/interpreted, bloated, steep learning curve) true - IS there anyway I can use sqlAlchemy in the \"rough and ready\" way I want to use psycopg - namely:\n\nexecute SQL statements directly without having to mess about with the ORM layer, etc.\n\nAny examples of doing this available?","AnswerCount":2,"Available Count":2,"Score":1.0,"is_accepted":false,"ViewCount":40683,"Q_Id":8588126,"Users Score":11,"Answer":"To talk with database any one need driver for that. If you are using client like SQL Plus for oracle, MysqlCLI for Mysql then it will direct run the query and that client come with DBServer pack. \nTo communicate from outside with any language like java, c, python, C#... We need driver to for that database. psycopg2 is driver to run query for PostgreSQL from python. \nSQLAlchemy is the ORM which is not same as database driver. It will give you flexibility so you can write your code without any database specific standard. ORM provide database independence for programmer. If you write object.save in ORM then it will check, which database is associated with that object and it will generate insert query according to the backend database.","Q_Score":57,"Tags":"python,postgresql,sqlalchemy,psycopg2","A_Id":8589254,"CreationDate":"2011-12-21T10:08:00.000","Title":"SQLAlchemy or psycopg2?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have to compare massive database dumps in xls format to parse for changes day-to-day (gross, right?). I'm currently doing this in the most backwards way possible, and using xlrd to turn the xls into csv files, and then I'm running diffs to compare them.\nSince it's a database, and I don't have a means of knowing if the data ever stays in the same order after something like an item deletion, I can't do a compare x line to x line between the files, so doing lists of tuples or something wouldn't make the most sense to me.\nI basically need to find every single change that could have happened on any row REGARDLESS of that row's position in the actual dump, and the only real \"lookup\" I could think of is SKU as a unique ID (it's a product table from an ancient DB system), but I need to know a lot more than just products being deleted or added, because they could modify pricing or anything else in that item.\nShould I be using sets? And once I've loaded 75+ thousand lines of this database file into a \"set\", is my ram usage going to be hysterical?\nI thought about loading in each row of the xls as a big concatenated string to add to a set. Is that an efficient idea? I could basically get a list of rows that differ between sets and then go back after those rows in the original db file to find my actual differences.\nI've never worked with data parsing on a scale like this. I'm mostly just looking for any advice to not make this process any more ridiculous than it has to be, and I came here after not really finding something that seemed specific enough to my case to feel like good advice. Thanks in advance.","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":19719,"Q_Id":8609737,"Users Score":0,"Answer":"You could load the data into a database, and compare the databases. If you think that is easier.\nThe key question you might need to think about is: can you sort the data somehow?\nSorted sets are so much easier to handle.\nP.S. 75000 lines is not very much. Anything that fits into main memory of a regular computer is not much. Add a couple of 0s.","Q_Score":2,"Tags":"python,database,diff,set,compare","A_Id":8609909,"CreationDate":"2011-12-22T21:08:00.000","Title":"Python comparing two massive sets of data in the MOST efficient method possible","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am using postgresql in ubuntu, and now i am working on python. I want to connect postgresql with an android application. Is there any way to connect postgresql with an android application?\n                  Any reply would be appreciated.","AnswerCount":1,"Available Count":1,"Score":0.3799489623,"is_accepted":false,"ViewCount":377,"Q_Id":8613246,"Users Score":2,"Answer":"Better way is to Use RestFUL API or WebService as front end for your Android device to connect to your PostgreSQL backend. I am not sure if it is possible to directly connect your android device to postgre SQL.","Q_Score":0,"Tags":"android,python,web-services,postgresql,ubuntu-10.04","A_Id":8613304,"CreationDate":"2011-12-23T07:11:00.000","Title":"what is the way to connect postgresql with android in ubuntu","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm writing a script where by a user registers his\/her username, but a function checks whether this username is already in the db or not. But I'm stuck on how to match my query with the input. Here is the code:\n\ndef checker(self, insane):                                                  \n        t = (insane,)                                                           \n    cmd = \"SELECT admin_user FROM admin_db where admin_user = \\\"%s\\\";\" %t\n    self.cursor.execute(cmd)\n    namer = self.cursor.fetchone()\n    print namer\n    if namer == insane:                                                     \n        print(\"Username is already chosen!\")\n        exit(1)\n    else:\n        pass\n\nSince namer returns as (u'maverick',) It doesn't match with the input. How should I go about implementing that?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1309,"Q_Id":8617837,"Users Score":1,"Answer":"The DB fetch models return a tuple for each row. Since you've only selected a single field, you can simply access namer[0] to get the actual value.","Q_Score":0,"Tags":"python,sql,sqlite","A_Id":8617856,"CreationDate":"2011-12-23T15:40:00.000","Title":"Matching user's input with query from sqlite3 db in python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I've looked in the documentation and haven't seen (from first sight) anything about cache in Pyramid. Maybe I missed something... Or maybe there are some third party packages to help with this.\nFor example, how to cache db query (SQLAlchemy), how to cache views? Could anyone give some link to examples or documentation?\nAppreciate any help!\nEDITED:\nHow to use memcache or database type cache or filebased cache?","AnswerCount":2,"Available Count":1,"Score":1.0,"is_accepted":false,"ViewCount":4486,"Q_Id":8651061,"Users Score":6,"Answer":"Your options are pyramid_beaker and dogpile.cache \npyramid_beaker was written to offer beaker caching for sessions.  it also lets you configure beaker cache regions, which can be used elsewhere.\ndogpile.cache is a replacement for beaker.  it hasn't been integrated to offer session support or environment.ini based setup yet.  however it addresses a lot of miscellaneous issues and shortcomings with beaker.\nyou can't\/shouldn't cache a SqlAlchemy query or results. weird and bad things will happen, because the SqlAlchemy objects are bound to a database session.  it's much better to convert the sqlalchemy results into another object\/dict and cache those.","Q_Score":3,"Tags":"python,sqlalchemy,pyramid","A_Id":14859955,"CreationDate":"2011-12-28T01:50:00.000","Title":"How to cache using Pyramid?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm engaged in developing a turn-based casual MMORPG game server.\nThe low level engine(NOT written by us) which handle networking,\nmulti-threading, timer, inter-server communication, main game loop etc, was\nwritten by C++. The high level game logic was written by Python.\nMy question is about the data model design in our game.\nAt first we simply try to load all data of a player into RAM and a shared data\ncache server when client login and schedule a timer periodically flush data into\ndata cache server and data cache server will persist data into database.\nBut we found this approach has some problems\n1) Some data needs to be saved or checked instantly, such as quest progress,\nlevel up, item & money gain etc.\n2) According to game logic, sometimes we need to query some offline player's\ndata.\n3) Some global game world data needs to be shared between different game\ninstances which may be running on a different host or a different process on the\nsame host. This is the main reason we need a data cache server sits between game\nlogic server and database.\n4) Player needs freely switch between game instances.\nBelow is the difficulty we encountered in the past:\n1) All data access operation should be asynchronized to avoid network I\/O\nblocking the main game logic thread. We have to send message to database or\ncache server and then handle data reply message in callback function and\ncontinue proceed game logic. It quickly become painful to write some moderate\ncomplex game logic that needs to talk several times with db and the game logic\nis scattered in many callback functions makes it hard to understand and\nmaintain.\n2) The ad-hoc data cache server makes things more complex, we hard to maintain\ndata consistence and effectively update\/load\/refresh data.\n3) In-game data query is inefficient and cumbersome, game logic need to query\nmany information such as inventory, item info, avatar state etc. Some\ntransaction machanism is also needed, for example, if one step failed the entire\noperation should be rollback. We try to design a good data model system in RAM,\nbuilding a lot of complex indexs to ease numerous information query, adding\ntransaction support etc. Quickly I realized what we are building is a in-memory\ndatabase system, we are reinventing the wheel...\nFinally I turn to the stackless python, we removed the cache server. All data\nare saved in database. Game logic server directly query database. With stackless\npython's micro tasklet and channel, we can write game logic in a synchronized\nway. It is far more easy to write and understand and productivity greatly\nimproved.\nIn fact, the underlying DB access is also asynchronized: One client tasklet\nissue request to another dedicate DB I\/O worker thread and the tasklet is\nblocked on a channel, but the entire main game logic is not blocked, other\nclient's tasklet will be scheduled and run freely. When DB data reply the\nblocked tasklet will be waken up and continue to run on the 'break\npoint'(continuation?).\nWith above design, I have some questions:\n1) The DB access will be more frequently than previous cached solution, does the\nDB can support high frequent query\/update operation? Does some mature cache\nsolution such as redis, memcached is needed in near future?\n2) Are there any serious pitfalls in my design? Can you guys give me some better\nsuggestions, especially on in-game data management pattern.\nAny suggestion would be appreciated, thanks.","AnswerCount":2,"Available Count":2,"Score":0.1973753202,"is_accepted":false,"ViewCount":3298,"Q_Id":8660622,"Users Score":2,"Answer":"It's difficult to comment on the entire design\/datamodel without greater understanding of the software, but it sounds like your application could benefit from an in-memory database.*  Backing up such databases to disk is (relatively speaking) a cheap operation. I've found that it is generally faster to: \nA) Create an in-memory database, create a table, insert a million** rows into the given table, and then back-up the entire database to disk \nthan \nB) Insert a million** rows into a table in a disk-bound database.\nObviously, single record insertions\/updates\/deletions also run faster in-memory. I've had success using JavaDB\/Apache Derby for in-memory databases.\n*Note that the database need not be embedded in your game server.\n**A million may not be an ideal size for this example.","Q_Score":8,"Tags":"python,database,python-stackless","A_Id":8660848,"CreationDate":"2011-12-28T19:57:00.000","Title":"Need suggestion about MMORPG data model design, database access and stackless python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm engaged in developing a turn-based casual MMORPG game server.\nThe low level engine(NOT written by us) which handle networking,\nmulti-threading, timer, inter-server communication, main game loop etc, was\nwritten by C++. The high level game logic was written by Python.\nMy question is about the data model design in our game.\nAt first we simply try to load all data of a player into RAM and a shared data\ncache server when client login and schedule a timer periodically flush data into\ndata cache server and data cache server will persist data into database.\nBut we found this approach has some problems\n1) Some data needs to be saved or checked instantly, such as quest progress,\nlevel up, item & money gain etc.\n2) According to game logic, sometimes we need to query some offline player's\ndata.\n3) Some global game world data needs to be shared between different game\ninstances which may be running on a different host or a different process on the\nsame host. This is the main reason we need a data cache server sits between game\nlogic server and database.\n4) Player needs freely switch between game instances.\nBelow is the difficulty we encountered in the past:\n1) All data access operation should be asynchronized to avoid network I\/O\nblocking the main game logic thread. We have to send message to database or\ncache server and then handle data reply message in callback function and\ncontinue proceed game logic. It quickly become painful to write some moderate\ncomplex game logic that needs to talk several times with db and the game logic\nis scattered in many callback functions makes it hard to understand and\nmaintain.\n2) The ad-hoc data cache server makes things more complex, we hard to maintain\ndata consistence and effectively update\/load\/refresh data.\n3) In-game data query is inefficient and cumbersome, game logic need to query\nmany information such as inventory, item info, avatar state etc. Some\ntransaction machanism is also needed, for example, if one step failed the entire\noperation should be rollback. We try to design a good data model system in RAM,\nbuilding a lot of complex indexs to ease numerous information query, adding\ntransaction support etc. Quickly I realized what we are building is a in-memory\ndatabase system, we are reinventing the wheel...\nFinally I turn to the stackless python, we removed the cache server. All data\nare saved in database. Game logic server directly query database. With stackless\npython's micro tasklet and channel, we can write game logic in a synchronized\nway. It is far more easy to write and understand and productivity greatly\nimproved.\nIn fact, the underlying DB access is also asynchronized: One client tasklet\nissue request to another dedicate DB I\/O worker thread and the tasklet is\nblocked on a channel, but the entire main game logic is not blocked, other\nclient's tasklet will be scheduled and run freely. When DB data reply the\nblocked tasklet will be waken up and continue to run on the 'break\npoint'(continuation?).\nWith above design, I have some questions:\n1) The DB access will be more frequently than previous cached solution, does the\nDB can support high frequent query\/update operation? Does some mature cache\nsolution such as redis, memcached is needed in near future?\n2) Are there any serious pitfalls in my design? Can you guys give me some better\nsuggestions, especially on in-game data management pattern.\nAny suggestion would be appreciated, thanks.","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":3298,"Q_Id":8660622,"Users Score":6,"Answer":"I've worked with one MMO engine that operated in a somewhat similar fashion. It was written in Java, however, not Python.\nWith regards to your first set of points:\n1) async db access We actually went the other route, and avoided having a \u201cmain game logic thread.\u201d All game logic tasks were spawned as new threads. The overhead of thread creation and destruction was completely lost in the noise floor compared to I\/O. This also preserved the semantics of having each \u201ctask\u201d as a reasonably straightforward method, instead of the maddening chain of callbacks that one otherwise ends up with (although there were still cases of this.) It also meant that all game code had to be concurrent, and we grew increasingly reliant upon immutable data objects with timestamps.\n2) ad-hoc cache We employed a lot of WeakReference objects (I believe Python has a similar concept?), and also made use of a split between the data objects, e.g. \u201cPlayer\u201d, and the \u201cloader\u201d (actually database access methods) e.g. \u201cPlayerSQLLoader;\u201d the instances kept a pointer to their Loader, and the Loaders were called by a global \u201cfactory\u201d class that would handle cache lookups versus network or SQL loads. Every \u201cSetter\u201d method in a data class would call the method changed, which was an inherited boilerplate for myLoader.changed (this);\nIn order to handle loading objects from other active servers, we employed \u201cproxy\u201d objects that used the same data class (again, say, \u201cPlayer,\u201d) but the Loader class we associated was a network proxy that would (synchronously, but over gigabit local network) update the \u201cmaster\u201d copy of that object on another server; in turn, the \u201cmaster\u201d copy would call changed itself.\nOur SQL UPDATE logic had a timer. If the backend database had received an UPDATE of the object within the last ($n) seconds (we typically kept this around 5), it would instead add the object to a \u201cdirty list.\u201d A background timer task would periodically wake and attempt to flush any objects still on the \u201cdirty list\u201d to the database backend asynchronously.\nSince the global factory maintained WeakReferences to all in-core objects, and would look for a single instantiated copy of a given game object on any live server, we would never attempt to instantiate a second copy of one game object backed by a single DB record, so the fact that the in-RAM state of the game might differ from the SQL image of it for up to 5 or 10 seconds at a time was inconsequential.\nOur entire SQL system ran in RAM (yes, a lot of RAM) as a mirror to another server who tried valiantly to write to disc. (That poor machine burned out RAID drives on average of once every 3-4 months due to \u201cold age.\u201d RAID is good.)\nNotably, the objects had to be flushed to database when being removed from cache, e.g. due to exceeding the cache RAM allowance.\n3) in-memory database \u2026 I hadn't run across this precise situation. We did have \u201ctransaction-like\u201d logic, but it all occurred on the level of Java getters\/setters.\nAnd, in regards to your latter points:\n1) Yes, PostgreSQL and MySQL in particular deal well with this, particularly when you use a RAMdisk mirror of the database to attempt to minimize actual HDD wear and tear. In my experience, MMO's do tend to hammer the database more than is strictly necessary, however. Our \u201c5 second rule\u201d* was built specifically to avoid having to solve the problem \u201ccorrectly.\u201d Each of our setters would call changed. In our usage pattern, we found that an object typically had either 1 field changed, and then no activity for some time, or else had a \u201cstorm\u201d of updates happen, where many fields changed in a row. Building proper transactions or so (e.g. informing the object that it was about to accept many writes, and should wait for a moment before saving itself to the DB) would have involved more planning, logic, and major rewrites of the system; so, instead, we bypassed the situation.\n2) Well, there's my design above :-)\nIn point of fact, the MMO engine I'm presently working on uses even more reliance upon in-RAM SQL databases, and (I hope) will be doing so a bit better. However, that system is being built using an Entity-Component-System model, rather than the OOP model that I described above.\nIf you already are based on an OOP model, shifting to ECS is a pretty paradigm shift and, if you can make OOP work for your purposes, it's probably better to stick with what your team already knows.\n*- \u201cthe 5 second rule\u201d is a colloquial US \u201cfolk belief\u201d that after dropping food on the floor, it's still OK to eat it if you pick it up within 5 seconds.","Q_Score":8,"Tags":"python,database,python-stackless","A_Id":8660935,"CreationDate":"2011-12-28T19:57:00.000","Title":"Need suggestion about MMORPG data model design, database access and stackless python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Apologies for the longish description.\nI want to run a transform on every doc in a large-ish Mongodb collection with 10 million records approx 10G. Specifically I want to apply a geoip transform to the ip field in every doc and either append the result record to that doc or just create a whole other record linked to this one by say id (the linking is not critical, I can just create a whole separate record).  Then I want to count and group by say city - (I do know how to do the last part).\nThe major reason I believe I cant use map-reduce is I can't call out to the geoip library in my map function (or at least that's the constraint I believe exists).\nSo I the central question is how do I run through each record in the collection apply the transform - using the most efficient way to do that.  \nBatching via Limit\/skip is out of question as it does a \"table scan\" and it is going to get progressively slower.\nAny suggestions?\nPython or Js preferred just bec I have these geoip libs but code examples in other languages welcome.","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":477,"Q_Id":8663432,"Users Score":1,"Answer":"Since you have to go over \"each record\", you'll do one full table scan anyway, then a simple cursor (find()) + maybe only fetching few fields (_id, ip) should do it. python driver will do the batching under the hood, so maybe you can give a hint on what's the optimal batch size (batch_size) if the default is not good enough.   \nIf you add a new field and it doesn't fit the previously allocated space, mongo will have to move it to another place, so you might be better off creating a new document.","Q_Score":3,"Tags":"python,mongodb,mapreduce","A_Id":8666791,"CreationDate":"2011-12-29T02:33:00.000","Title":"How do I transform every doc in a large Mongodb collection without map\/reduce?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Apologies for the longish description.\nI want to run a transform on every doc in a large-ish Mongodb collection with 10 million records approx 10G. Specifically I want to apply a geoip transform to the ip field in every doc and either append the result record to that doc or just create a whole other record linked to this one by say id (the linking is not critical, I can just create a whole separate record).  Then I want to count and group by say city - (I do know how to do the last part).\nThe major reason I believe I cant use map-reduce is I can't call out to the geoip library in my map function (or at least that's the constraint I believe exists).\nSo I the central question is how do I run through each record in the collection apply the transform - using the most efficient way to do that.  \nBatching via Limit\/skip is out of question as it does a \"table scan\" and it is going to get progressively slower.\nAny suggestions?\nPython or Js preferred just bec I have these geoip libs but code examples in other languages welcome.","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":477,"Q_Id":8663432,"Users Score":0,"Answer":"Actually I am also attempting another approach in parallel (as plan B) which is to use mongoexport.  I use it with --csv to dump a large csv file with just the (id, ip) fields.  Then the plan is to use a python script to do a geoip lookup and then post back to mongo as a new doc on which map-reduce can now be run for count  etc.  Not sure if this is faster or the cursor is.  We'll see.","Q_Score":3,"Tags":"python,mongodb,mapreduce","A_Id":8677503,"CreationDate":"2011-12-29T02:33:00.000","Title":"How do I transform every doc in a large Mongodb collection without map\/reduce?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a row of data in dict format. Is there an easy way to insert it into a mysql table. I know that I can write a custom function to convert dict into a custom sql query, but I am looking for a more direct alternative.","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":1650,"Q_Id":8674426,"Users Score":2,"Answer":"MySQLDB does not come with anything which allows a direct operation like that.  This is a common problem with a variety of answers, including a custom function for this purpose.\nIn my experience, it is best to buckle down and just write the paramaterized SQL most of the time.  If you have the same thing going on a lot, then I would consider factoring it into a utility function.\nHOWEVER, if you are hand-writing static SQL using parameters, then most of the security and bug related issues are taken care of.  When you start basing your SQL on a dictionary of data that came from where (?), you need to be much more careful.  \nIn summary, your code will likely be more readable and maintainable and secure if you simply write the queries, use parameters, and document well.\n(Note: some proponents of ORM, etc... may disagree... this is an opinion based on a lot of experience on what was simple, reliable, and worked for our team)","Q_Score":2,"Tags":"python,dictionary,insert,mysql-python","A_Id":8674504,"CreationDate":"2011-12-29T22:52:00.000","Title":"MySQLdb inserting a dict into a table","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a row of data in dict format. Is there an easy way to insert it into a mysql table. I know that I can write a custom function to convert dict into a custom sql query, but I am looking for a more direct alternative.","AnswerCount":2,"Available Count":2,"Score":0.4621171573,"is_accepted":false,"ViewCount":1650,"Q_Id":8674426,"Users Score":5,"Answer":"Well... According to the documentation for paramstyle:\n\nSet to 'format' = ANSI C printf format codes, e.g. '...WHERE name=%s'.\n  If a mapping object is used for conn.execute(), then the interface\n  actually uses 'pyformat' = Python extended format codes, e.g.\n  '...WHERE name=%(name)s'. However, the API does not presently allow\n  the specification of more than one style in paramstyle\n\nSo, it should be just a matter of:\ncurs.execute(\"INSERT INTO foo (col1, col2, ...) VALUES (%(key1)s, %(key2)s, ...)\", dictionary)\nwhere key1, key2, etc. would be keys from the dictionary.\nDisclaimer: I haven't tried this myself :)\nEdit: yeah, tried it. It works.","Q_Score":2,"Tags":"python,dictionary,insert,mysql-python","A_Id":8674547,"CreationDate":"2011-12-29T22:52:00.000","Title":"MySQLdb inserting a dict into a table","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Assuming I have a schema with the name \"my_schema\", how can I create tables with \"django syncdb\" for that particular schema? Or is there any other alternatives for quickly creating tables from my django models? I think, by default django creates tables for the \"public\" schema.","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":4285,"Q_Id":8680673,"Users Score":0,"Answer":"I have used following info and work for me \n'default': {\n        'ENGINE': 'django.db.backends.postgresql_psycopg2',\n        'NAME': 'dab_name',\n        'USER': 'username',\n        'PASSWORD': 'password',\n        'HOST': 'localhost',\n        'PORT': '5432',\n        'OPTIONS': {\n            'options': '-c search_path=tours' #schema name\n        }\n    }\nTested on postgresql 9 and django 1.10.2\nThanks @romke","Q_Score":7,"Tags":"python,database,django","A_Id":42578440,"CreationDate":"2011-12-30T14:52:00.000","Title":"How to specify schema name while running \"syncdb\" in django?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"For example in CQL, \nSELECT * from abc_dimension ORDER BY key ASC;\nseems to be not working.\nAny help?","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":3328,"Q_Id":8751293,"Users Score":0,"Answer":"Latest versions of Cassandra support aggregations within single partition only.","Q_Score":2,"Tags":"python,cassandra,cql","A_Id":43361173,"CreationDate":"2012-01-05T23:13:00.000","Title":"does cassandra cql support aggregation functions, like group by and order by","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"We are sketching out how a system would work. The problem is that have a set of items with a computed value for each item.  Say for example you like players in the nba and there are a certain set of players that you have shown preferences about.\nExamples might be:\n\nnumber of games played\nrebounding \nscoring\nassists\nminutes played per game \nplayers that your other friends like\nlikelihood of being traded - you often want players that are going to be traded\n\nThere's approx 500 players in the nba.  From a performance pov, querying is cost prohibitive - throwing in other people' s preferences etc.... We have been thinking of doing an alternative approaches. One approach is a NoSQL where each user gets written a document of each player. To be honest, this seems like too many unkowns as I have zero experience. Another approach is where each person in the system would get a table dedicated to them. Perhaps write out the table definition via cron on a nightly basis and when the user logs in, do a create table statement and then have a dedicated query against that. This sounds really ugly to me too (although feasible). We could also certainly have a single table where each user has a row for each player. I'd rather not premise the whole system off self-joins though. It seems to take querying off-line and we could feasibly measure 1000 players against these different parameters.\nAre there other ideas that I'm missing? I don't want anything too esoteric - preferably just MySQL and Python. Would be using InnoDB and not so concerned about splitting up the tables per database per host issue.\nAny other ideas or realword experience would be appreciated? I'm sure this has been solved many times before.\nthx","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":49,"Q_Id":8753559,"Users Score":0,"Answer":"I'm using mongodb right now for the first time and I find it to be really awesome in the way it lets you represent a document pretty much like an object oriented class structure. You can easily have a document per user that stores any number of embedded documents. Your players can be in a nested dictionary or a list, and you can index on player names. Then when you request a user, there are NO joins. You have all your data. Plus there is a flexible schema so you can always just add more fields whenever you want.\nAs for mysql table-per-user, I agree its really messy and can get out of control.\nAnother alternative is you could look into a key-value store like Redis for caching purposes since its in memory, it would be fast as well.","Q_Score":0,"Tags":"python,mysql,database-design","A_Id":8754480,"CreationDate":"2012-01-06T04:56:00.000","Title":"Caching computed results for each user - would having a table dedicated to each user make sense?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Are there any python3 modules for importing(reading) excel .xls files or is there any work in progress on porting one of the python2 modules? All I'm coming up with is xlrd for python2.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":530,"Q_Id":8788041,"Users Score":0,"Answer":"I believe the maintainer of xlrd is working on porting it, but it's not yet ready.","Q_Score":1,"Tags":"excel,python-3.x,xls","A_Id":8797959,"CreationDate":"2012-01-09T11:55:00.000","Title":"python3 module for importing xls files","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I use xlrd to read data from excel files.\nFor integers stored in the files, let's say 63, the xlrd interprets it as 63.0 of type number. \nWhy can't xlrd recognize 63 as an integer? \nAssume sheet.row(1)[0].value gives us 63.0. How can I convert it back to 63.","AnswerCount":6,"Available Count":1,"Score":0.1651404129,"is_accepted":false,"ViewCount":30994,"Q_Id":8825681,"Users Score":5,"Answer":"I'm reminded of this gem from the xlrd docs:\n\nDates in Excel spreadsheets\nIn reality, there are no such things. What you have are floating point\n  numbers and pious hope.\n\nThe same is true of integers.  Perhaps minus the pious hope.","Q_Score":20,"Tags":"python,xlrd","A_Id":8826320,"CreationDate":"2012-01-11T19:48:00.000","Title":"Integers from excel files become floats?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a regular desktop application which is written in Python\/GTK and SQLObject as ORM. My goal is to create a webinterface where a user can login and sync\/edit the database. My application is split up in different modules, so the database and gtk code are completly separate, so I would like to run the same database code on the webserver too.\nSo, I would like to know if there's a webframework which could handle these criteria:\n\nUser authentication\nUse my own database code\/SQLObject\nSome widgets to build a basic ui\n\nThis would be my first webproject, so I'm a bit confused by all searchresults. CherryPy, Turbogears, web2py, Pyramid? I would be happy if someone could give me some pointers what would be a good framework in my situation.","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":375,"Q_Id":8895942,"Users Score":0,"Answer":"Try the pyramid, it does not impose anything you like as opposed to Django. And has a wealth of features for building Web applications at any level.","Q_Score":0,"Tags":"python,sqlobject","A_Id":8896107,"CreationDate":"2012-01-17T14:05:00.000","Title":"Choosing Python\/SQLObject webframework","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Well i have a question that i feel i've been answered several times, from what i found here. However, as a newbie, i can't really understand how to perform a really basic operation.\nHere's the thing :\n\ni have an .xls and when i use xlrd to get a value i'm just using \nsh.cell(0,0) (assuming that sh is my sheet);\nif what is in the cell is a string i get something like text:u'MyName' and i only want to keep the string 'MyName';\nif what is in the cell is a number i get something like number:201.0 and i only want to keep the integer 201.\n\nIf anyone can indicate me what i should to only extract the value, formatted as i want, thank you.","AnswerCount":4,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":27320,"Q_Id":8909342,"Users Score":0,"Answer":"The correct answer to this is to simply use the Cell.value function. This will return a number or a Unicode string depending on what the cell contains.","Q_Score":9,"Tags":"python,xlrd","A_Id":43124531,"CreationDate":"2012-01-18T11:29:00.000","Title":"Python xlrd : how to convert an extracted value?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"We recently moved a Zeo instance over to a new server environment and one of the changes was the file system now has the database files stored on an NFS share.\nWhen trying to start zeo, we've been getting lock file errors which after researching seems to be because of a known issue of lock files being created on an NFS share.  \nMy question is, can we maintain the data (.fs) files on the share but have the lock files created on the server's filesystem?  We want to maintain the data being stored on the SAN so moving the data over to box is really not an option.\nAny help would be greatly appreciated!","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":260,"Q_Id":8914644,"Users Score":1,"Answer":"This is likely not a good setup.  Your best bet is to work-around NFS in spite of it: maybe a loopback ext3 filesystem mounted on a regular file on the NFS volume -- NFSv3 should have few practical limits to filesize that you won't have natively.  Only you will be able to measure if this performs well enough.  Otherwise, you should know that (generally) no networked database performs well or without side-effects over NFS.","Q_Score":0,"Tags":"python,zope,zodb","A_Id":8916946,"CreationDate":"2012-01-18T17:36:00.000","Title":"Zeo\/ZODB lock file location, possible to change?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I need to provide individuals with their financial statement, and I am using S3. So far what I am doing is making the file public-read and creating a unique Key, using uuid.uuid4(). \nWould this be acceptable, or how else could I make this more secure? Sending authentication keys for each individual is not an option.","AnswerCount":3,"Available Count":1,"Score":0.0665680765,"is_accepted":false,"ViewCount":260,"Q_Id":8935191,"Users Score":1,"Answer":"Even though version 4 UUIDs are supposed to incorporate random data, I wouldn't want to rely on the fact that the RNG used by Python's uuid.uuid4() being securely random. The Python docs make no mention about the quality of the randomness, so I'd be afraid that you might end up with guessable UUID's.\nI'm not a crypto expert, so I won't suggest a specific alternative, but I would suggest using something that is designed to produce crypto-quailty random data, and transform that into something that can be used as an S3 key (I'm not sure what the requirements on S3 key data might be, but I'd guess they're supposed to be something like a filename).\nTo be honest, having no security other than an unguessable name still leaves me with a bad feeling. It seems to easy to have an unintentional leak of the names, as Ian Clelland suggests in his comment.","Q_Score":1,"Tags":"python,security,amazon-s3","A_Id":8935272,"CreationDate":"2012-01-20T00:08:00.000","Title":"Sending 'secure' financial statements on S3","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"In python, I am firing Sparql queries to get data from dbpedia.\nAt a point approximately firing 7,000 queries, my script is hangs at    line   results = sparql.query().convert()\nwhich is already executed atleast 5000 times in the loop\nAny idea what could be the issue in it","AnswerCount":1,"Available Count":1,"Score":0.537049567,"is_accepted":false,"ViewCount":157,"Q_Id":8965123,"Users Score":3,"Answer":"try splitting up the .query() and .convert() into two separate lines. I would guess that .query() is where it's hanging, and I would further guess that you are being rate-limited by DBPedia, but I can't find any information on what their limits might be.","Q_Score":1,"Tags":"python,sparql,mysql-python,dbpedia","A_Id":8965215,"CreationDate":"2012-01-22T22:02:00.000","Title":"python script hangs at results = sparql.query().convert()","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":1,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"First of all, I am sorry if this question doesn't belong to SO since I don't know where else to post it, anyway...\nI am looking for a decent python based database development RAD framework with nice data aware widgets and grids. A desktop framework would be much preferable to a web framework (I've developed heavy DB-centric apps in django but the web dev experience is still painful compared to a desktop one), although a web framework will do as long as there are powerful data-centric widgets to go along with it.\nIdeally, it should be as useful as say Delphi or MSAccess \/ VBA (I used to develop using those a long time ago). For the record, I have very good development experience in django and wxPython and as I've said developing heavy data-centric web apps is tough and wxPython although very powerful lacks DB-related widgets.\nPlease note that the use of Python is mandatory because I've been using this language exclusively for all my projects in the last few years and I can't bear the idea of switching back to more mundane languages.\nThanks for any suggestion...","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":684,"Q_Id":9045723,"Users Score":1,"Answer":"I am also looking for something similar to Kexi. Unfortunately python scripting is not supported in Kexi for windows. I would like to find something better than MS Access, and it does not have to be based on python. So far I have looked at quite a few IDE's but have not found anything where a GUI and database application can be built us as quickly as in access.\n I think of all the best one I have seen is Alpha 5. There could be something based on Net Beans but I really do not know. Oracle APEX is another one I have heard about but it doesn't support desktop applications (as far as I know).","Q_Score":3,"Tags":"python,database,widget,rad","A_Id":15711432,"CreationDate":"2012-01-28T13:49:00.000","Title":"Python database widgets\/environment like MSAccess","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":1,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am building a web App with mongoDB as the backend.  Some of the documents need to store a collection of items in some sort of list, and then the system will need to frequently check if a specified item is present in that list.  Using Python's 'in' operator takes Big-O(N) time, n being the size of the list.  Since these list can get quite large, I want something faster than that.  Python's 'set' type does this operation in constant time (and enforces uniqueness, which is good in my case), but is considered an invalid data type to put in MongoDB.\nSo what's the best way to do this?  Is there some way to just use a regular list and exploit mongo's indexing features?  Again, I want to know, for a given document in a collection, does a list inside that document contain particular element?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":2402,"Q_Id":9115979,"Users Score":6,"Answer":"You can represent a set using a dictionary. Your elements become the keys, and all the values can be set to a constant such as 1. The in operator checks for the existence of a key.\nEDIT. MongoDB stores a dict as a BSON document, where the keys must be strings (with some additional restrictions), so the above advice is of limited use.","Q_Score":5,"Tags":"python,mongodb","A_Id":9116463,"CreationDate":"2012-02-02T16:29:00.000","Title":"Mongodb with Python's \"set()\" type","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"i have Ubuntu and installed python3 since my script is written in it. Since I use MYSQL with MySQLdb, I installed \napt-get install python-mysqldb\nhowever this installed MySQLdb to Python (which is 2.6 on Ubuntu) and not to Python3.\n\nHow can I install MySQLdb for Python3\nShould I use it at all or switch to PyMSQL\n\nSorry, I have just started working with Python today...","AnswerCount":7,"Available Count":1,"Score":0.0285636566,"is_accepted":false,"ViewCount":14751,"Q_Id":9146320,"Users Score":1,"Answer":"If you are planning to switch from MySQLDB then I recommend you to use MySQL connector Python\nWhy ?\n\nit work with both Python 2 and 3\nBecause it is official Oracle driver for MySQL for working with Python.\nIt is purely written in Python\nYou can also use  C extension to connect to MySQL.\nMySQL Connector\/Python is implementing the MySQL Client\/Server protocol completely in Python. This means you don't have to compile anything or MySQL doesn't even have to be installed on the machine.\nAlso, it has great support for connection pooling","Q_Score":9,"Tags":"python,mysql,ubuntu,installation","A_Id":51553512,"CreationDate":"2012-02-05T02:06:00.000","Title":"install python MySQLdb to python3 not python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a project in which i use JDBC with MySQL to store some user information, Java REST for the server and Python REST for the client.\nMy question is: by default(i haven't changed anything in the configurations), are the http requests from the client serialized on the server's side? I ask this because i'd like to know if i need to make the database insert\/delete querys thread-safe or something.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":253,"Q_Id":9158578,"Users Score":1,"Answer":"Of course they need to be thread safe.  You should be writing your Java server as if it were single threaded, because a Java EE app server will assign a thread per incoming request.\nYou also need to think about database isolation and table locking.  Will you allow \"dirty reads\" or should your transactions be serializable?   Should you SELECT FOR UPDATE?  That's a database setting, separate from threading considerations.","Q_Score":0,"Tags":"java,python,mysql,rest,jdbc","A_Id":9158709,"CreationDate":"2012-02-06T10:16:00.000","Title":"Serialization with JDBC with MySQL, JAVA REST and Python REST","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Why use py manage.py test ? \nWhat's the point? It creates the table anyway... if I wanted to test it, then I wouldn't want it to create the actual table!!!","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":126,"Q_Id":9160411,"Users Score":0,"Answer":"Test is meant to perform both the upgrade and the downgrade steps. You want to verify that the application is usable in both states. So the idea would be to upgrade, run tests, downgrade, run tests, and verify you don't break things.\nIf the test run fails, it gives you a chance to clean it up, reset, and try again. Usually, I'd say that the test run must completely cleanly before the migration is considered \"good\" and able to be committed to the code base.","Q_Score":0,"Tags":"python,mysql,database,sqlalchemy","A_Id":9161223,"CreationDate":"2012-02-06T12:53:00.000","Title":"In SQLAlchemy-migrate, what's the point of using \"test\"?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I wanted your advice for the best design approach at the following Python project.\nI am building a web service system that is split into 2 parts:  \n\nThis part grabs realtime data from a 3rd party API and puts the data in a DB.  \nThis part exposes a json API to access data from the DB mentioned in 1).  \n\nSome background info - 2) runs on django, and exposes the API via view methods. It uses SQLAlchemy instead of the django ORM.  \nMy questions are:\n- Should 1) and 2) run on the same machine, considering that they both access the same MySQL DB?\n- What should 1) run on? I was thinking about just running cron jobs with Python scripts that also use SQLAlchemy. This is because I don't see a need for an entire web framework here, especially because this needs to work super fast. Is this the best approach?\n- Data size - 1) fetches about 60,000 entries and puts them in the DB every 1 minute (an entry contains of about 12 Float values and a few Dates and Integers). What is the best way to deal with the ever growing amount of data here? Would you split the DB? If so, into what?  \nThanks!","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":319,"Q_Id":9182936,"Users Score":0,"Answer":"I would say, run the two on the same machien to start with, and see how the performance goes. Why spend money on a second machine if you don\u2019t have to?\nAs for \u201cdealing with the ever growing amount of data\u201d\u2014do you need to keep old data around? If not, your second task can simply delete old data when it\u2019s done with it. Provided all the records are properly time-stamped, you don\u2019t need to worry about race conditions between the two tasks.","Q_Score":2,"Tags":"python,real-time","A_Id":9189761,"CreationDate":"2012-02-07T19:56:00.000","Title":"Realtime data server architecture","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am working on a system where a bunch of modules connect to a MS SqlServer DB to read\/write data. Each of these modules are written in different languages (C#, Java, C++) as each language serves the purpose of the module best. \nMy question however is about the DB connectivity. As of now, all these modules use the language-specific Sql Connectivity API to connect to the DB. Is this a good way of doing it ? \nOr alternatively, is it better to have a Python (or some other scripting lang) script take over the responsibility of connecting to the DB? The modules would then send in input parameters and the name of a stored procedure to the Python Script and the script would run it on the database and send the output back to the respective module. \nAre there any advantages of the second method over the first ? \nThanks for helping out!","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":112,"Q_Id":9202562,"Users Score":0,"Answer":"If we assume that each language you use will have an optimized set of classes to interact with databases, then there shouldn't be a real need to pass all database calls through a centralized module.\nUsing a \"middle-ware\" for database manipulation does offer a very significant advantage. You can control, monitor and manipulate your database calls from a central and single location. So, for example, if one day you wake up and decide that you want to log certain elements of the database calls, you'll need to apply the logical\/code change only in a single piece of code (the middle-ware). You can also implement different caching techniques using middle-ware, so if the different systems share certain pieces of data, you'd be able to keep that data in the middle-ware and serve it as needed to the different modules.\nThe above is a very advanced edge-case and it's not commonly used in small applications, so please evaluate the need for the above in your specific application and decide if that's the best approach. \nDoing things the way you do them now is fine (if we follow the above assumption) :)","Q_Score":2,"Tags":"python,sql-server,architecture","A_Id":9456223,"CreationDate":"2012-02-08T22:32:00.000","Title":"DB Connectivity from multiple modules","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Is there any tutorials about how to set-up sqlalchemy for windows? I went to www.sqlalchemy.org and they don't have clear instructions about set-up for windows. When I opened the zipped package, I see distribute_setup, ez_setup and setup.py among other files but it doesn't see to install sqlalchemy.","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":9330,"Q_Id":9221888,"Users Score":1,"Answer":"The Command pip install sqlalchemy will download the necessary files and run setup.py install for you.","Q_Score":1,"Tags":"python,sql,database,orm,sqlalchemy","A_Id":29831712,"CreationDate":"2012-02-10T02:21:00.000","Title":"Configuring sqlalchemy for windows","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"There have been many questions along these lines but I'm struggling to apply them to my scenario. Any help would be be greatly appreciated!\nWe currently have a functioning mySQL database hosted on a website, data is entered from a website and via PHP it is put into the database.\nAt the same time we want to now create a python application that works offline. It should carry out all the same functions as the web version and run totally locally, this means it needs a copy of the entire database to run locally and when changes are made to such local database they are synced next time there is an internet connection available.\nFirst off I have no idea what the best method would be to run such a database offline. I was considering just setting up a localhost, however this needs to be distributable to many machines. Hence setting up a localhost via an installer of some sort may be impractical no?\nSecondly synchronization? Not a clue on how to go about this!\nAny help would be very very very appreciated.\nThank you!","AnswerCount":3,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":2804,"Q_Id":9237481,"Users Score":0,"Answer":"How high-performance does your local application need to be? Also, how reliable is the locally available internet connection? If you don't need extremely high performance, why not just leave the data in the remote MySQL server? \nIf you're sure you need access to local data I'd look at MySQL's built-in replication for synchronization. It's really simple to setup\/use and you could use it to maintain a local read-only copy of the remote database for quick data access. You'd simply build into your application the ability to perform write queries on the remote server and do read queries against the local DB. The lag time between the two servers is generally very low ... like on the order of milliseconds ... but you do still have to contend with network congestion preventing a local slave database from being perfectly in-sync with the master instantaneously.\nAs for the python side of things, google mysql-python because you'll need a python mysql binding to work with a MySQL database. Finally, I'd highly recommend SQLalchemy as an ORM with python because it'll make your life a heck of a lot easier.\nI would say an ideal solution, however, would be to set up a remote REST API web service and use that in place of directly accessing the database. Of course, you may not have the in-house capabilities, the time or the inclination to do that ... which is also okay :)","Q_Score":2,"Tags":"php,python,mysql,localhost,sync","A_Id":9237543,"CreationDate":"2012-02-11T03:04:00.000","Title":"Python sync with mySQL for local application?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"There have been many questions along these lines but I'm struggling to apply them to my scenario. Any help would be be greatly appreciated!\nWe currently have a functioning mySQL database hosted on a website, data is entered from a website and via PHP it is put into the database.\nAt the same time we want to now create a python application that works offline. It should carry out all the same functions as the web version and run totally locally, this means it needs a copy of the entire database to run locally and when changes are made to such local database they are synced next time there is an internet connection available.\nFirst off I have no idea what the best method would be to run such a database offline. I was considering just setting up a localhost, however this needs to be distributable to many machines. Hence setting up a localhost via an installer of some sort may be impractical no?\nSecondly synchronization? Not a clue on how to go about this!\nAny help would be very very very appreciated.\nThank you!","AnswerCount":3,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":2804,"Q_Id":9237481,"Users Score":0,"Answer":"Are you planning to run mysql on your local python offline apps ? I would suggest something like sqlite. As for keeping things in sync, it also depends on the type of data that needs to be synchronized. One question that needs to be answered:\nAre the data generated by these python apps something that is opague ? If yes (i.e. it doesn't have any relations to other entities), then you can queue the data locally and push it up to the centrally hosted website.","Q_Score":2,"Tags":"php,python,mysql,localhost,sync","A_Id":9237521,"CreationDate":"2012-02-11T03:04:00.000","Title":"Python sync with mySQL for local application?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm building a database front-end with python and glade. I need to present SQL query results in the form of database tables inside my app's window (schema followed by tuples\/records). Both the schema and the database entries are dynamic because the schema could be that of a join operation or in general altered and the number of tuples could be any valid number.One possible solution could be to format a given table with python, create a text object in my GUI and change its' value to that produced by python. Advices and suggestions are very welcome.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":2104,"Q_Id":9299934,"Users Score":3,"Answer":"Given that the number and name of the columns to display isn't known beforehand, you could just create a gtk.TreeView widget in glade and modify it as you need in the application code.\nThis widget could be updated to use a new model using gtk.TreeView.set_model and the columns could be adapted to match the information to be dsplayed with the gtk.TreeView.{append,remove,insert}_column columns.\nRegarding the model, you coud create a new gtk.ListStore with appropriate columns depending on the results from the database.\nI hope this helps.","Q_Score":3,"Tags":"python,user-interface,gtk,pygtk,glade","A_Id":9302750,"CreationDate":"2012-02-15T19:28:00.000","Title":"GUI for database tables with pygtk and glade","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":1,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm having a problem with the sessions in my python\/wsgi web app. There is a different, persistent mysqldb connection for each thread in each of 2 wsgi daemon processes. Sometimes, after deleting old sessions and creating a new one, some connections still fetch the old sessions in a select, which means they fail to validate the session and ask for login again.\nDetails: Sessions are stored in an InnoDB table in a local mysql database. After authentication (through CAS), I delete any previous sessions for that user, create a new session (insert a row), commit the transaction, and redirect to the originally requested page with the new session id in the cookie. For each request, a session id in the cookie is checked against the sessions in the database.\nSometimes, a newly created session is not found in the database after the redirect. Instead, the old session for that user is still there. (I checked this by selecting and logging all of the sessions at the beginning of each request). Somehow, I'm getting cached results. I tried selecting the sessions with SQL_NO_CACHE, but it made no difference.\nWhy am I getting cached results? Where else could the caching occur, and how can stop it or refresh the cache? Basically, why do the other connections fail to see the newly inserted data?","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":5316,"Q_Id":9318347,"Users Score":16,"Answer":"MySQL defaults to the isolation level \"REPEATABLE READ\" which means you will not see any changes in your transaction that were done after the transaction started - even if those (other) changes were committed. \nIf you issue a COMMIT or ROLLBACK in those sessions, you should see the changed data (because that will end the transaction that is \"in progress\").\nThe other option is to change the isolation level for those sessions to \"READ COMMITTED\". Maybe there is an option to change the default level as well, but you would need to check the manual for that.","Q_Score":9,"Tags":"python,mysql,session,caching,wsgi","A_Id":9318495,"CreationDate":"2012-02-16T20:09:00.000","Title":"Why are some mysql connections selecting old data the mysql database after a delete + insert?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am looking to store information in a database table that will be constantly receiving and sending data back and forth to an iPhone App\/Python Socket. The problem is, if I were to have my own servers, what is the maximum queries I can sustain?\nThe reason I'm asking is because if I were to have thousands of people using the clients and multiple queries are going a second, I'm afraid something will go wrong.\nIs there a different way of storing user information without MySQL? Or is MySQL OK for what I am doing?\nThank you!","AnswerCount":2,"Available Count":1,"Score":0.2913126125,"is_accepted":false,"ViewCount":1960,"Q_Id":9322523,"Users Score":3,"Answer":"The maximum load is going to vary based on the design of your application and the power of the hardware that you put it on.  A well designed application on reasonable hardware will far outperform what you need to get the project off the ground.  \nIf you are unexpectedly successful, you will have money to put into real designers, real programmers and a real business plan.  Until then, just have fun hacking away and see if you can bring your idea to reality.","Q_Score":4,"Tags":"iphone,python,mysql,objective-c,database","A_Id":9322806,"CreationDate":"2012-02-17T03:37:00.000","Title":"How many SQL queries can be run at a time?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I will start a project ( not commercial, just for learning ) but I would like to choose to work with the right tools as I would if I were doing it for a company.\nFirst of all small description of what I will need.\nIt would be a server-client(s) application.\nFor the server:\n- GUI for Windows\n- ORM \n- Database without installation (sqlite ???)\n- GUI builder (RAD Tool)\n- Ability to create easily REST Services\nClients would be android devices\n- GUI for android mobile\nClients would connect to the server and get some initial settings and then start to \nsend  information to the server.\nServer should be able to display properly the information collected from the clients and \nedit them if needed.\nOpen source technologies are mandatatory.\nFirst I am thinking to use sqlite ( I should not make any installation except the programm). Any alternatives here?\nFor the server maybe python with a gui library and sql alchemy. What about Camelot?\nAnd for the clients (android) java. I think there are no other options here.\nCan you make some comments on the above choices?\nMaybe you can suggest something different which will make the development faster...","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":657,"Q_Id":9354695,"Users Score":0,"Answer":"As you have asserted: client is java only.\nOn server:\n\nGUI for Windows : WPF  \nORM - Database without installation : SQLCE 4.0 - Maybe use codefirst \nGUI builder (RAD Tool) : Visual Studio lets you do that for WPF apps \nAbility to create easily REST Services : Use WCF\n\nhope that helps","Q_Score":0,"Tags":"android,python,client-server","A_Id":9354732,"CreationDate":"2012-02-20T00:15:00.000","Title":"Right tools for GUI windows program","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":1,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm new to Python (relatively new to programing in general) and I have created a small python script that scrape some data off of a site once a week and stores it to a local database (I'm trying to do some statistical analysis on downloaded music). I've tested it on my Mac and would like to put it up onto my server (VPS with WiredTree running CentOS 5), but I have no idea where to start.\nI tried Googling for it, but apparently I'm using the wrong terms as \"deploying\" means to create an executable file. The only thing that seems to make sense is to set it up inside Django, but I think that might be overkill. I don't know...\nEDIT: More clarity","AnswerCount":3,"Available Count":1,"Score":0.0665680765,"is_accepted":false,"ViewCount":865,"Q_Id":9356926,"Users Score":1,"Answer":"Copy script to server\ntest script manually on server\nset cron, \"crontab -e\" to a value that will test it soon\nonce you've debugged issues set cron to the appropriate time.","Q_Score":1,"Tags":"python,django,centos","A_Id":9357006,"CreationDate":"2012-02-20T06:14:00.000","Title":"Deploying a Python Script on a Server (CentOS): Where to start?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I have a column heading Fee. Using xlwt in python, I successfully generated the required excel.This column is always blank at the creation of Excel file.\nIs it possible to have the Fee column preformatted to 'Currency' and 'two decimal places', so that when I write manually in the Fee column of the Excel file after downloading, 23 should change into $23.00 ??","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":2721,"Q_Id":9375637,"Users Score":11,"Answer":"I got it working like this:\ncurrency_style = xlwt.XFStyle()\ncurrency_style.num_format_str = \"[$$-409]#,##0.00;-[$$-409]#,##0.00\"\nsheet.write(row+2, col, val, style=currency_style)","Q_Score":5,"Tags":"python,excel,xlwt","A_Id":9376306,"CreationDate":"2012-02-21T10:10:00.000","Title":"Preformat to currency and two decimal places in python using xlwt for excel","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a static folder that is managed by apache where images are stored.\nI wonder if it's possible by configuring apache to send all files from that folder as downloadable files, not opening them as images inside browser? I suppose I can do it by creating a special view in Flask, but I think it would be nicer if I could do it with some more simple solution.","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":219,"Q_Id":9378664,"Users Score":1,"Answer":"You can force the contents to be a downloadable attachment using http headers.\nIn PHP that would be:\n\n$fileName = 'dummy.jpg';\nheader(\"Content-Disposition: attachment; filename=$fileName\");\n\nThen, the script dumps the raw contents of the file.","Q_Score":4,"Tags":"python,browser,flask","A_Id":9378819,"CreationDate":"2012-02-21T13:46:00.000","Title":"Send image as an attachment in browser","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"In order to demonstrate the security feature of Oracle one has to call OCIServerVersion() or OCIServerRelease() when the user session has not yet been established.\nWhile having the database parameter sec_return_server_release_banner = false.\nI am using Python cx_Oracle module for this, but I am not sure how to get the server version before establishing the connection. Any ideas?","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1064,"Q_Id":9389381,"Users Score":0,"Answer":"With-out establishing a connection,. No you can never asking anything. It's like going to Google Page.(Internet Architecture - wether you call it sessionless or session based)\nAs for Authentical, if no permission are set - Oracle uses a username 'nobody' as a user and thus gives every user a session.\nI am a user of Oracle APEX, and I use Python, PLSQL regurlary.\nThat's one nice question. Thanks.","Q_Score":7,"Tags":"python,cx-oracle","A_Id":21155146,"CreationDate":"2012-02-22T05:08:00.000","Title":"python cx_oracle and server information","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'd like to add a feature to my behind the firewall webapp that exposes and ODBC interface so users can connect with a spreadsheet program to explore our data.\nWe don't use a RDBMS so I want to emulate the server side of the connection.\nI've searched extensively for a library or framework that helps to implement the server side component of an ODBC connection with no luck.  Everything I can find is for the other side of the equation - connecting one's client program to a database using an ODBC driver.\nIt would be great to use Python but at this point language preference is secondary, although it does have to run on *nix.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":59,"Q_Id":9432332,"Users Score":0,"Answer":"The server side of ODBC is already done, it is your RDBMS.\nODBC is a client side thing, most implementations are just a bridge between ODBC interface and the native client interface for you-name-your-RDBMS-here.\nThat is why you will not find anything about the server side of ODBC... :-)\nImplementing a RDBMS (even with a subset of SQL) is no easy quest. My advice is to expose your underlying database storage, the best solution depends on what database are you using.\nIf its a read-only interface, expose a database mirror using some sort of asynchronous replication.\nIf you want it read\/write, trust me, you better don't. If your customer is savvy, expose an API, it he isn't you don't want him fiddling with your database. :-)\n[updated]\nIf your data is not stored on a RDBMS, IMHO there is no point in exposing it through a relational interface like ODBC. The advice to use some sort of asynchronous replication with a relational database is still valid and probably the easiest approach. \nOtherwise you will have to reinvent the wheel implementing an SQL parser, network connection, authentication and related logic. If you think it's worth, go for it!","Q_Score":1,"Tags":"python,odbc","A_Id":9432486,"CreationDate":"2012-02-24T14:26:00.000","Title":"Are there any libraries (or frameworks) that aid in implementing the server side of ODBC?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am using plone to build my site.\nIn one page template, I have the <input type=\"file\" name=\"file\">  and this form: <form method=\"post\" action=\"addintoDb\" enctype=\"multipart\/form-data\"\nThe addintoDb is a python script that save my information into db:context.addParam(name=request.name, path=request['file']). \nin my db i have name and in the path: <ZPublisher.HTTPRequest.FileUpload instance at 0x081F98C8> but i want to have the put where the file was uploaded (like c:...)\nI hope somebody can help me.","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":890,"Q_Id":9446769,"Users Score":1,"Answer":"You are not saving the file on the filesystem, but in the Zope object database. You'd have to use python code (not a python script) to open a filepath with the open built-in function to save the data to.","Q_Score":2,"Tags":"python,plone,zope","A_Id":9456924,"CreationDate":"2012-02-25T18:27:00.000","Title":"upload file with python script in plone","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a handful of servers all connected over WAN links (moderate bandwidth, higher latency) that all need to be able to share info about connected clients.  Each client can connect to any of the servers in the 'mesh'.  Im looking for some kind of distributed database each server can host and update.  It would be important that each server is able to get updated with the current state if its been offline for any length of time.\nIf I can't find anything, the alternative will be to pick a server to host a MySQL DB all the servers can insert to; but I'd really like to remove this as a single-point-of-failure if possible. (and the downtime associated with promoting a slave to master)\nIs there any no-single-master distributed data store you have used before and would recommend?\nIt would most useful if any solution has Python interfaces.","AnswerCount":5,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":981,"Q_Id":9456954,"Users Score":0,"Answer":"What you describe reminds me of an Apache Cassandra cluster configured so that each machine hosts a copy of the whole dataset and reads and writes succeed when they reach a single node (I never did that, but I think it's possible). Nodes should be able to remain functional when WAN links are down and receive pending updates as soon as they get back on-line. Still, there is no magic - if conflicting updates are issued on different servers or outdated replicas are used to generate new data, consistency problems will arise on any architecture you select.\nA second issue is that for every local write, you'll get n-1 remote writes and your servers may spend a lot of time and bandwidth debating who has the latest record.\nI strongly suggest you fire up a couple EC2 instances and play with their connectivity to check if everything works the way you expect. This seems to be in the \"creative misuse\" area and your mileage may vary wildly, if you get any at all.","Q_Score":1,"Tags":"python,database,linux,datastore,distributed-system","A_Id":9466181,"CreationDate":"2012-02-26T20:41:00.000","Title":"Distributed state","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":0},{"Question":"I am playing around with python and thought I would make a simple language learning program... ie: lanuageA | languageB | type of word | synonym | antonym |\nbasically flash cards...\nI have made a crude version using python and json, and have just started playing with sqlite3... Is a database a better way to organize the information, and for pulling things out and referencing against each other. and against user input. Or would it be easier to use nested dictionaries?","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":371,"Q_Id":9484814,"Users Score":0,"Answer":"If your data fits in memory and you only require to access elements by key, a dictionary is probably just enough for your needs.","Q_Score":2,"Tags":"python,json,sqlite","A_Id":9484859,"CreationDate":"2012-02-28T15:32:00.000","Title":"json or sqlite3 for a dictionary","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am playing around with python and thought I would make a simple language learning program... ie: lanuageA | languageB | type of word | synonym | antonym |\nbasically flash cards...\nI have made a crude version using python and json, and have just started playing with sqlite3... Is a database a better way to organize the information, and for pulling things out and referencing against each other. and against user input. Or would it be easier to use nested dictionaries?","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":371,"Q_Id":9484814,"Users Score":1,"Answer":"Who is going to modify your data?\n\nIf you plan to only modify the word set yourself (as a developer, not a user of an application), you can use JSON to keep the data on the disk\nIf you want to allow users of your application to add\/edit\/remove flashcards, you should use a database (sqlite3 is OK), because otherwise you would have to save the whole data file after each small change made by the user. You could, of course, split the data into separate JSON files, add thread locks, etc., but that's what database engines are for.","Q_Score":2,"Tags":"python,json,sqlite","A_Id":9485889,"CreationDate":"2012-02-28T15:32:00.000","Title":"json or sqlite3 for a dictionary","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am fetching records from gae model using cursor() and with_cursor() logic as used in paging. but i am not sure how to check that there is no any other record in db that is pointed by cursor. i am fetching these records in chunks within some iterations.when i got my required results in the first iteration then in next iteration I want to check there is no any record in model but I not get any empty\/None value of cursor at this stage.please let me know how to perform this check with cursors in google app engine with python.","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":550,"Q_Id":9521289,"Users Score":0,"Answer":"i am not 100% sure about that but what i used to do is compare the last cursor with the actual cursor and i think i noticed that they were the same so i came to the conclusion that it was the last cursor.","Q_Score":0,"Tags":"python,google-app-engine","A_Id":9521520,"CreationDate":"2012-03-01T17:47:00.000","Title":"cursor and with_cursor() in GAE","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I'm new to Django and have only been using sqlite3 as a database engine in Django. Now one of the applications I'm working on is getting pretty big, both in terms of models' complexity and requests\/second.\nHow do database engines supported by Django compare in terms of performance? Any pitfalls in using any of them? And the last but not least, how easy is it to switch to another engine once you've used one for a while?","AnswerCount":4,"Available Count":1,"Score":1.0,"is_accepted":false,"ViewCount":41120,"Q_Id":9540154,"Users Score":6,"Answer":"MySQL and PostgreSQL work best with Django. I would highly suggest that when you choose one that you change your development settings to use it while development (opposed to using sqlite3 in dev mode and a \"real\" database in prod) as there are subtle behavioral differences that can caused lots of headaches in the future.","Q_Score":48,"Tags":"python,database,django,sqlite","A_Id":9540685,"CreationDate":"2012-03-02T20:49:00.000","Title":"Which database engine to choose for Django app?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am trying to think through a script that I need to create. I am most likely going to be using php unless there would be a better language to do this with e.g. python or ror. I only know a little bit of php so this will definitely be a learning experience for me and starting fresh with a different language wouldn't be a problem if it would help in the long run. \nWhat I am wanting to do is create a website where people can sign up for WordPress hosting. Right now I have the site set up with WHMCS. If I just leave it how it is I will have manually go in and install WordPress every time a customer signs up. I would like an automated solution that creates a database and installs WordPress as soon as the customer signs up. With WHMCS I can run a script as soon as a customer signs up and so far I understand how to create a database, download WordPress, and install WordPress. The only thing is I can't figure out how to make it work with more than one customer because with each customer there will be a new database. What I need the script to do is when customer A signs up,  the script will create a database name \"customer_A\" (that name is just an example) and when, lets say my second customer signs up, the script will create a database named \"customer_B\". \nIs there a possible solution to this?\nThanks for the help","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":90,"Q_Id":9543171,"Users Score":0,"Answer":"I did this yesterday.\nmy process was to add a row to a master accounts table, get the auto inc id, use that along with the company name to create the db name. so in my case the db's are \nRoot_1companyname1\nRoot_2companyname2\n..\nRoot_ is optional of course.\nAsk if you have any questions.","Q_Score":0,"Tags":"php,python,wordpress","A_Id":9543194,"CreationDate":"2012-03-03T03:30:00.000","Title":"Automate database creation with incremental name?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a Python Flask app I'm writing, and I'm about to start on the backend. The main part of it involves users POSTing data to the backend, usually a small piece of data every second or so, to later be retrieved by other users. The data will always be retrieved within under an hour, and could be retrieved in as low as a minute. I need a database or storage solution that can constantly take in and store the data, purge all data that was retrieved, and also perform a purge on data that's been in storage for longer than an hour.\nI do not need any relational system; JSON\/key-value should be able to handle both incoming and outgoing data. And also, there will be very constant reading, writing, and deleting.\nShould I go with something like MongoDB? Should I use a database system at all, and instead write to a directory full of .json files constantly, or something? (Using only files is probably a bad idea, but it's kind of the extent of what I need.)","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":168,"Q_Id":9544618,"Users Score":1,"Answer":"You might look at mongoengine we use it in production with flask(there's an extension) and it has suited our needs well, there's also mongoalchemy which I haven't tried but seems to be decently popular. \nThe downside to using mongo is that there is no expire automatically, having said that you might take a look at using redis which has the ability to auto expire items. There are a few ORMs out there that might suit your needs.","Q_Score":3,"Tags":"python,database,flask","A_Id":9545480,"CreationDate":"2012-03-03T08:17:00.000","Title":"In need of a light, changing database\/storage solution","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"there's something I'm struggling to understand with SQLAlchamy from it's documentation and tutorials. \nI see how to autoload classes from a DB table, and I see how to design a class and create from it (declaratively or using the mapper()) a table that is added to the DB. \nMy question is how does one write code that both creates the table (e.g. on first run) and then reuses it?\nI don't want to have to create the database with one tool or one piece of code and have separate code to use the database.\nThanks in advance,\nPeter","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":77,"Q_Id":9554204,"Users Score":0,"Answer":"I think you're perhaps over-thinking the situation. If you want to create the database afresh, you normally just call Base.metadata.create_all() or equivalent, and if you don't want to do that, you don't call it.\nYou could try calling it every time and handling the exception if it goes wrong, assuming that the database is already set up.\nOr you could try querying for a certain table and if that fails, call create_all() to put everything in place.\nEvery other part of your app should work in the same way whether you perform the db creation or not.","Q_Score":0,"Tags":"python,database,sqlalchemy","A_Id":9554925,"CreationDate":"2012-03-04T10:41:00.000","Title":"SQLAlchamy Database Construction & Reuse","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm developing a multi-player game in Python with a Flask frontend, and I'm using it as an opportunity to learn more about the NoSQL way of doing things.\nRedis seems to be a good fit for some of the things I need for this app, including storage of server-side sessions and other transient data, e.g. what games are in progress, who's online, etc. There are also several good Flask\/Redis recipes that have made things very easy so far.\nHowever, there are still some things in the data model that I would prefer lived inside a traditional RDBMS, including user accounts, logs of completed games, etc.  It's not that Redis can't do these things, but I just think the RDBMS is more suited to them, and since Redis wants everything in memory, it seems to make sense to \"warehouse\" some of this data on disk.\nThe one thing I don't quite have a good strategy for is how to make these two data stores live happily together.  Using ORMs like SQLAlchemy and\/or redisco seems right out, because the ORMs are going to want to own all the data that's part of their data model, and there are inevitably times I'm going to need to have classes from one ORM know about classes from the other one (e.g. \"users are in the RDBMS, but games are in Redis, and games have users participating in them.)\nDoes anyone have any experience deploying python  web apps using a NoSQL store like Redis for some things and an RDBMS for others?  If so, do you have any strategies for making them work together?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":532,"Q_Id":9557552,"Users Score":3,"Answer":"You should have no problem using an ORM because, in the end, it just stores strings, numbers and other values. So you could have a game in progress, and keep its state in Redis, including the players' IDs from the SQL player table, because the ID is just a unique integer.","Q_Score":4,"Tags":"python,nosql,redis,rdbms,flask","A_Id":9557895,"CreationDate":"2012-03-04T18:17:00.000","Title":"Redis and RDBMS coexistence (hopefully cooperation) in Flask applications","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a game where each player has a score. I would like to have a global scoreboard where players can compare their scores, see how well they are placed and browse the scoreboard. \nUnfortunately I cannot find an efficient way to program this: storing the current player position in the scoreboard means I have to update a large part of the scoreboard when a player improves his score, and not storing the position means I have to recompute it each time I need it (which would also require a lot of computations).\nIs there a better solution to this problem? Or is one of the above solutions \"good enough\" to be used practically with a lot of users and a lot of updates?","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":857,"Q_Id":9576578,"Users Score":0,"Answer":"The ORDER BY clause was made for that and doesn't look so slow.","Q_Score":0,"Tags":"python,sql","A_Id":9576946,"CreationDate":"2012-03-06T01:20:00.000","Title":"Scoreboard using Python and SQL","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a table address. This table is constantly getting new row inserts, appox 1 row per second. Lets called it process1.\nIn parallel, I need to iterate over SELECT * from address results inserted till now via process1. This is Process2. It should wait for Process1 to insert new rows if it reaches the end, ie, there are no more rows to process (iterate) in address.\nBoth Process1 and 2 are very long. Several hours or maybe days. \nHow should process2 look like in python?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":112,"Q_Id":9607711,"Users Score":0,"Answer":"Add a TIMESTAMP column and select rows with a newer timestamp than the latest processed.","Q_Score":0,"Tags":"python,mysql","A_Id":9607771,"CreationDate":"2012-03-07T19:21:00.000","Title":"python dynamically select rows from mysql","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am trying rewrite a simple Rails application I made a while ago with cherrypy and Python3.  So far I have been unable to find a Python replacement for ActiveRecord (the persistence part of the application).  Most of the recommendations I've found on StackOverflow have been for SQL Alchemy.  I looked into this and it seems much too complicated to get up and running.  After reading its online docs and a book from Amazon, It's still not clear how to even proceed; not a good sign. \nSo my question is, what are developers using to persist data in their python3 web applications? \nAlso, I looked into Django but python3 is a requirement so that's out.  \nThanks","AnswerCount":3,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":456,"Q_Id":9678989,"Users Score":0,"Answer":"I have developed a transparent persistent storage system for python this is currently in an alpha-stage.  Once you create a persistent object, you can access and modify its attributes using standard python syntax (obj.x=3;) and the persistence is done behind the scenes (by overloading the setattr methods, etc.).  Contact me if you are interested in learning more. -Stefan","Q_Score":2,"Tags":"python,web-applications,persistence,cherrypy","A_Id":9832722,"CreationDate":"2012-03-13T05:49:00.000","Title":"Persistence for a python (cherrypy) web application?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am trying rewrite a simple Rails application I made a while ago with cherrypy and Python3.  So far I have been unable to find a Python replacement for ActiveRecord (the persistence part of the application).  Most of the recommendations I've found on StackOverflow have been for SQL Alchemy.  I looked into this and it seems much too complicated to get up and running.  After reading its online docs and a book from Amazon, It's still not clear how to even proceed; not a good sign. \nSo my question is, what are developers using to persist data in their python3 web applications? \nAlso, I looked into Django but python3 is a requirement so that's out.  \nThanks","AnswerCount":3,"Available Count":2,"Score":0.0665680765,"is_accepted":false,"ViewCount":456,"Q_Id":9678989,"Users Score":1,"Answer":"SQL Alchemy is a industrial standard is no choice. But it's not as difficult as it seems at first sight","Q_Score":2,"Tags":"python,web-applications,persistence,cherrypy","A_Id":9679132,"CreationDate":"2012-03-13T05:49:00.000","Title":"Persistence for a python (cherrypy) web application?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I seem to remember reading somewhere that google app engine automatically caches the results of very frequent queries into memory so that they are retrieved faster.  \nIs this correct?\nIf so, is there still a charge for datastore reads on these queries?","AnswerCount":3,"Available Count":2,"Score":0.0665680765,"is_accepted":false,"ViewCount":1313,"Q_Id":9689588,"Users Score":1,"Answer":"I think that app engine does not cache anything for you.  While it could be that, internally, it caches some things for a split second, I don't think you should rely on that.\nI think you will be charged the normal number of read operations for every entity you read from every query.","Q_Score":3,"Tags":"python,google-app-engine,memcached,bigtable","A_Id":9689883,"CreationDate":"2012-03-13T18:06:00.000","Title":"Does app engine automatically cache frequent queries?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I seem to remember reading somewhere that google app engine automatically caches the results of very frequent queries into memory so that they are retrieved faster.  \nIs this correct?\nIf so, is there still a charge for datastore reads on these queries?","AnswerCount":3,"Available Count":2,"Score":0.0665680765,"is_accepted":false,"ViewCount":1313,"Q_Id":9689588,"Users Score":1,"Answer":"No, it doesn't. However depending on what framework you use for access to the datastore, memcache will be used. Are you developing in java or python? On the java side, Objectify will cache GETs automatically but not Queries. Keep in mind that there is a big difference in terms of performance and cachability between gets and queries in both python and java.\nYou are not charged for datastore reads for memcache hits.","Q_Score":3,"Tags":"python,google-app-engine,memcached,bigtable","A_Id":9690080,"CreationDate":"2012-03-13T18:06:00.000","Title":"Does app engine automatically cache frequent queries?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I have a spreadsheet with about 1.7m lines, totalling 1 GB, and need to perform various queries on it. Being most comfortable with Python, my first approach was to hack together a bunch of dictionaries keyed in a way that would facilitate the queries I was trying to make. E.g. if I needed to be able to access everyone with a particular area code and age, I would make an areacode_age 2-dimensional dict. I ended up needing quite a few of these, which multiplied my memory footprint (to the order of ~10GB), and even though I had enough RAM to support this, the process was still quite slow.\nAt this point, it seemed like I was playing a sucker's game. \"Well this is what relational databases were made for, right?\", I thought. I imported sqlite3 and imported my data into an in-memory database. I figure databases are built for speed and this will solve my problems.\nIt turns out though, that doing a query like \"SELECT (a, b, c) FROM foo WHERE date1<=d AND date2>e AND name=f\" takes 0.05 seconds. Doing this for my 1.7m rows would take 24 hours of compute time. My hacky approach with dictionaries was about 3 orders of magnitude faster for this particular task (and, in this example, I couldn't key on date1 and date2 obviously, so I was getting every row that matched name and then filtering by date).\nSo, my question is, why is this so slow, and how can I make it fast? And what is the Pythonic approach? Possibilities I've been considering:\n\nsqlite3 is too slow, and I need something more heavyweight\nI need to somehow change my schema or my queries to be more... optimized?\nthe approaches I've tried so far are entirely wrong and I need a whole new tool of some kind\nI read somewhere that, in sqlite 3, doing repeated calls to cursor.execute is much slower than using cursor.executemany. It turns out that executemany isn't even compatible with select statements though, so I think this was a red herring.\n\nThanks.","AnswerCount":3,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":572,"Q_Id":9694967,"Users Score":4,"Answer":"sqlite3 is too slow, and I need something more heavyweight\n\nFirst, sqlite3 is fast, sometime faster than MySQL\nSecond, you have to use index, put a compound index in (date1, date2, name) will speed thing up significantly","Q_Score":2,"Tags":"python,database,sqlite,indexing,bigdata","A_Id":9695095,"CreationDate":"2012-03-14T02:05:00.000","Title":"Querying (pretty) big relational data in Python in a reasonable amount of time?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"i am new in python and i want to read office 2010 excel file without changing its style. Currently its working fine but changing date format. i want it as they are in excel file.","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":719,"Q_Id":9757361,"Users Score":1,"Answer":"i want it as they are in excel file.\n\nA date is recorded in an Excel file (both 2007+ XLSX files and earlier XLS files) as a floating point number of days (and fraction thereof) since some date in 1899\/1900 or 1904. Only the \"number format\" that is recorded against the cell can be used to distinguish whether a date or a number was intended.\nYou will need to be able to retrieve the actual float value and the \"number format\" and apply the format to the float value. If the \"number format\" being used is one of the standard ones, this should be easy enough to do. Customised number formats are another matter. Locale-dependant formats likewise.\nTo get detailed help, you will need to give examples of what raw data you have got and what you want to \"see\" and how it is now being presented (\"changing date format\").","Q_Score":0,"Tags":"python,openpyxl","A_Id":9757506,"CreationDate":"2012-03-18T09:49:00.000","Title":"How to read office 2010 excelfile using openpyxl without changing style","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm creating python app using relatively big SQL database (250k rows). Application needs GUI where most important part of it would be to present results of SQL queries.\nSo I'm looking for a best way to quickly present data in tables in GUI.\nMost preferably I'd be using wx - as it has seamless connection to main application I'm working with. And what I need is least effort between SQL query a and populating GUI table. \nI used once wx.grid, but it seemed to be limited functionality. Also I know of wx.grid.pygridtablebase - what is the difference?\nWhat would be easiest way to do this?","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":420,"Q_Id":9762841,"Users Score":1,"Answer":"You could use wx.grid or one of the ListCtrls. There's an example of a grid with 100 million cells in the wxPython demo that you could use for guidance on projects with lots of information. For ListCtrls, you would want to use a Virtual ListCtrl using the wx.LC_VIRTUAL flag. There's an example of that in the demo as well.","Q_Score":1,"Tags":"python,sqlite,user-interface,wxpython,wxwidgets","A_Id":9771997,"CreationDate":"2012-03-18T22:22:00.000","Title":"Most seamless way to present data in gui","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":1,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":">>> _cursor.execute(\"select * from bitter.test where id > 34\")\n    1L\n    >>> _cursor.fetchall()\n    ({'priority': 1L, 'default': 0, 'id': 35L, 'name': 'chinanet'},)\n    >>> _cursor.execute(\"select * from bitter.test where id > 34\")\n    1L\n    >>> _cursor.fetchall()\n    ({'priority': 1L, 'default': 0, 'id': 35L, 'name': 'chinanet'},)\n    >>> \n\n\nthe first time, i run cursor.execute and cursor.fetchall, i got the right result.\nbefore the second time i run execute and fetchall\ni insert data into mysql which id id 36, i also run commit command in mysql\nbut cursor.execute\/fetchall counld only get the data before without new data","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":677,"Q_Id":9764963,"Users Score":2,"Answer":"I guess you're using InnoDB. This is default for an InnoDB transaction.\n\nREPEATABLE READ\nThis is the default isolation level for InnoDB. For consistent reads,\n  there is an important difference from the READ COMMITTED isolation\n  level: All consistent reads within the same transaction read the\n  snapshot established by the first read. This convention means that if\n  you issue several plain (nonlocking) SELECT statements within the same\n  transaction, these SELECT statements are consistent also with respect\n  to each other. See Section 13.2.8.2, \u201cConsistent Nonlocking Reads\u201d.\n\nI haven't tested yet but forcing MySQLdb to start a new transaction by issuing a commit() on the current connection or create a new connection might solve the issue.","Q_Score":2,"Tags":"python,mysql-python","A_Id":9765239,"CreationDate":"2012-03-19T04:13:00.000","Title":"cursor fetch wrong records from mysql","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Is there a new way to connect to MySQL from Python with Mac OS X Lion (10.7.x)?\nAll the material I can find only seems to support Snow Leopard (10.6) and older.\nI've tried installing pyodbc, but can't get the odbc drivers to register with the operating system (maybe a 10.6 -> 10.7 compatibility issue?)","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":391,"Q_Id":9791587,"Users Score":0,"Answer":"Turns out the newest MySql_python worked great.  just had to run sudo python setup.py install","Q_Score":1,"Tags":"python,mysql,macos","A_Id":9792010,"CreationDate":"2012-03-20T17:09:00.000","Title":"Python MySQL On Mac OS X Lion","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Are there any alternative to xlrd, xlwt and xlutils for handling MS Excel in python? As far as I know, their licensing does not allow it to be used for commercial purpose and I was wondering if there are any alternative to that other than using COM.","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":3189,"Q_Id":9805426,"Users Score":1,"Answer":"openpyxl is definitely worth a test drive, but keep in mind that it support only XLSX files,\nwhile xlrd\/xlwr support only XLS files.","Q_Score":2,"Tags":"python","A_Id":10435892,"CreationDate":"2012-03-21T13:17:00.000","Title":"Alternative to xlrd, xlwt and xlutils in python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am writing a music catalogue application with PyQt using to display GUI. I have a problem about choosing database engine. There are simply too many options.\nI can use:\n-PyQt build-in QSql\n-sqlite3\n-SQLAlchemy (Elixir)\n-SQLObject\n-Python DB-API\nProbably there are far more options, this list is what I got from google (I'm open for any other propositions). If I decide to use some ORM which database system should I use? MySql, PostgreSQL or other? I know some MySql, but I  heard a lot of good thing about PostgreSQL, on the other hand sqlite3 seems be most popular in desktop applications. I would be grateful for any advice.\nEDIT:\nAn application is meant to work on Linux and Windows. I think database size should be around 100-10k entries.","AnswerCount":2,"Available Count":2,"Score":0.0996679946,"is_accepted":false,"ViewCount":475,"Q_Id":9859343,"Users Score":1,"Answer":"You would be better off using an ORM (Object Relational Library) Library that would allow you to design in an OOP way, and let it take care of the database for you. There are many advantages; but one of the greatest is that you won't be tied to a database engine. You can use sqlite for development, and keep your project compatible with Postgresql, Mysql and even Oracle D, depending on a single change in a configuration parameter.\nGiven that, my ORM of choice is SQLAlchemy, due to its maturity for being well known and used (but others could be fine as well).","Q_Score":2,"Tags":"python,database,sqlite,sqlalchemy","A_Id":9860250,"CreationDate":"2012-03-25T10:09:00.000","Title":"Databases and python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am writing a music catalogue application with PyQt using to display GUI. I have a problem about choosing database engine. There are simply too many options.\nI can use:\n-PyQt build-in QSql\n-sqlite3\n-SQLAlchemy (Elixir)\n-SQLObject\n-Python DB-API\nProbably there are far more options, this list is what I got from google (I'm open for any other propositions). If I decide to use some ORM which database system should I use? MySql, PostgreSQL or other? I know some MySql, but I  heard a lot of good thing about PostgreSQL, on the other hand sqlite3 seems be most popular in desktop applications. I would be grateful for any advice.\nEDIT:\nAn application is meant to work on Linux and Windows. I think database size should be around 100-10k entries.","AnswerCount":2,"Available Count":2,"Score":0.3799489623,"is_accepted":false,"ViewCount":475,"Q_Id":9859343,"Users Score":4,"Answer":"SQLite3 has the advantage of shipping with Python, so it doesn't require any installation.  It has a number of nice features (easy-of-use, portability, ACID, storage in a single file, and it is reasonably fast).  \nSQLite makes a good starting-off point.  Python's DB API assures a consistent interface to all the popular DBs, so it shouldn't be difficult to switch to another DB later if you change you mind.  \nThe decision about whether to use an ORM is harder and it is more difficult to change your mind later.  If you can isolate the DB access in just a few functions, then you may not need an ORM at all.","Q_Score":2,"Tags":"python,database,sqlite,sqlalchemy","A_Id":9859423,"CreationDate":"2012-03-25T10:09:00.000","Title":"Databases and python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a small issue(for lack of a better word) with MySQL db. I am using Python.\nSo I have this table in which rows are inserted regularly. As regularly as 1 row \/sec.\nI run two Python scripts together. One that simulates the insertion at 1 row\/sec. I have also turned autocommit off and explicitly commit after some number of rows, say 10. \nThe other script is a simple \"SELECT count(*) ...\" query on the table. This query doesn't show me the number of rows the table currently has. It is stubbornly stuck at whatever number of rows the table had initially when the script started running. I have even tried \"SELECT SQL_NO_CACHE count(*) ...\" to no effect.\nAny help would be appreciated.","AnswerCount":3,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":392,"Q_Id":9866319,"Users Score":1,"Answer":"If autocommit is turned off in the reader as well, then it will be doing the reads inside a transaction and thus not seeing the writes the other script is doing.","Q_Score":2,"Tags":"python,mysql","A_Id":9868793,"CreationDate":"2012-03-26T03:37:00.000","Title":"Python MySQL- Queries are being unexpectedly cached","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a small issue(for lack of a better word) with MySQL db. I am using Python.\nSo I have this table in which rows are inserted regularly. As regularly as 1 row \/sec.\nI run two Python scripts together. One that simulates the insertion at 1 row\/sec. I have also turned autocommit off and explicitly commit after some number of rows, say 10. \nThe other script is a simple \"SELECT count(*) ...\" query on the table. This query doesn't show me the number of rows the table currently has. It is stubbornly stuck at whatever number of rows the table had initially when the script started running. I have even tried \"SELECT SQL_NO_CACHE count(*) ...\" to no effect.\nAny help would be appreciated.","AnswerCount":3,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":392,"Q_Id":9866319,"Users Score":0,"Answer":"My guess is that either the reader or writer (most likely the writer) is operating inside a transaction which hasn't been committed. Try ensuring that the writer is committing after each write, and try a ROLLBACK from the reader to make sure that it isn't inside a transaction either.","Q_Score":2,"Tags":"python,mysql","A_Id":9867231,"CreationDate":"2012-03-26T03:37:00.000","Title":"Python MySQL- Queries are being unexpectedly cached","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have several Shelve i.e. .db files that I wish to merge together into one single database.\nThe only method I could think of was to iterate through each database rewriting each iteration to the new database, but this takes too long.\nIs there a better way to do this?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":320,"Q_Id":9915062,"Users Score":0,"Answer":"Shelves are mappings, and mappings have an update() method.","Q_Score":0,"Tags":"python,database,shelve","A_Id":9915108,"CreationDate":"2012-03-28T20:20:00.000","Title":"How can I merge Shelve files\/databases?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have some *.xls (excel 2003) files\uff0c and I want to convert those files into xlsx (excel 2007).\nI use the uno python package, when I save the documents,\nI can set the Filter name: MS Excel 97\nBut there is no Filter name like 'MS Excel 2007',\nHow can set the the filter name to convert xls to xlsx ?","AnswerCount":17,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":99140,"Q_Id":9918646,"Users Score":0,"Answer":"This is a solution for MacOS with old xls files (e.g. Excel 97 2004).\nThe best way I found to deal with this format, if excel is not an option, is to open the file in openoffice and save it to another format as csv files.","Q_Score":43,"Tags":"python,uno","A_Id":67111357,"CreationDate":"2012-03-29T03:20:00.000","Title":"how to convert xls to xlsx","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have to create Excel spreadsheet with nice format from Python. I thought of doing it by: \n\nI start in Excel as it is very easy to format: I write in Excel the\nmodel I want, with the good format\nI read this from Python\nI create from Python an Excel spreadsheet with the same format\n\nIn the end, the purpose is to create from Python Excel spreadsheets, but formatting with xlwt takes a lot of time, so I thought of formatting first in Excel to help. \nI have researched for easy ways to doing this but haven't found any. I can stick to my current working solution, using xlwt in Python to create formatted Excel, but it is quite awkward to use. \nThanks for any reply","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":4524,"Q_Id":9920935,"Users Score":0,"Answer":"You said:\n\nformatting with xlwt takes a lot of time\n\nand  \n\nit is quite awkward to use\n\nPerhaps you are not using easyxf? If so, check out the tutorial that you can access via www.python-excel.org, and have a look at examples\/xlwt_easyxf_simple_demo.py in your xlwt installation.","Q_Score":3,"Tags":"python,excel,format,xlwt","A_Id":10001613,"CreationDate":"2012-03-29T07:32:00.000","Title":"Easily write formatted Excel from Python: Start with Excel formatted, use it in Python, and regenerate Excel from Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I want to ask you what programming language I should use to develop a horizontally scalable database. I don't care too much about performance.\nCurrently, I only know PHP and Python, but I wonder if Python is good for scalability.\nOr is this even possible in Python?\nThe reasons I don't use an existing system is, I need deep insight into the system, and there is no database out there that can store indexes the way I want. (It's a mix of non relational, sparse free multidimensional, and graph design)\nEDIT:\nI already have most of the core code written in Python and investigated ways to improve adding data for that type of database design, what limits the use of other databases even more.\nEDIT 2:\nForgot to note, the database tables are several hundred gigabytes.","AnswerCount":4,"Available Count":3,"Score":1.2,"is_accepted":true,"ViewCount":284,"Q_Id":9927372,"Users Score":1,"Answer":"The deveopment of a scalable database is language independent, i cannot say much about PHP, but i can tell you good things about Python, it's easy to read, easy to learn, etc. In my opinion it makes the code much cleaner than other languges.","Q_Score":0,"Tags":"python,programming-languages,database-programming","A_Id":9927520,"CreationDate":"2012-03-29T14:25:00.000","Title":"Programming a scalable database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I want to ask you what programming language I should use to develop a horizontally scalable database. I don't care too much about performance.\nCurrently, I only know PHP and Python, but I wonder if Python is good for scalability.\nOr is this even possible in Python?\nThe reasons I don't use an existing system is, I need deep insight into the system, and there is no database out there that can store indexes the way I want. (It's a mix of non relational, sparse free multidimensional, and graph design)\nEDIT:\nI already have most of the core code written in Python and investigated ways to improve adding data for that type of database design, what limits the use of other databases even more.\nEDIT 2:\nForgot to note, the database tables are several hundred gigabytes.","AnswerCount":4,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":284,"Q_Id":9927372,"Users Score":0,"Answer":"Since this is clearly a request for \"opinion\", I thought I'd offer my $.02\nWe looked at MongoDB 12-months ago, and started to really like it...but for one issue. MongoDB limits the largest database to amount of physical RAM installed on the MongoDB server. For our tests, this meant we were limited to 4 GB databases. This didn't fit our needs, so we walked away (too bad really, because Mongo looked great).\nWe moved back to home turf, and went with PostgreSQL for our project. It is an exceptional system, with lots to like.\nBut we've kept an eye on the NoSQL crowd ever since, and it looks like Riak is doing some really interesting work.  \n(fyi -- it's also possible the MongoDB project has resolved the DB size issue -- we haven't kept up with that project).","Q_Score":0,"Tags":"python,programming-languages,database-programming","A_Id":9927811,"CreationDate":"2012-03-29T14:25:00.000","Title":"Programming a scalable database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I want to ask you what programming language I should use to develop a horizontally scalable database. I don't care too much about performance.\nCurrently, I only know PHP and Python, but I wonder if Python is good for scalability.\nOr is this even possible in Python?\nThe reasons I don't use an existing system is, I need deep insight into the system, and there is no database out there that can store indexes the way I want. (It's a mix of non relational, sparse free multidimensional, and graph design)\nEDIT:\nI already have most of the core code written in Python and investigated ways to improve adding data for that type of database design, what limits the use of other databases even more.\nEDIT 2:\nForgot to note, the database tables are several hundred gigabytes.","AnswerCount":4,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":284,"Q_Id":9927372,"Users Score":0,"Answer":"Betweent PHP & Python, definitely Python. Where I work, the entire system is written in Python and it scales quite well.\np.s.: Do take a look at Mongo Db though.","Q_Score":0,"Tags":"python,programming-languages,database-programming","A_Id":9927445,"CreationDate":"2012-03-29T14:25:00.000","Title":"Programming a scalable database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a web application build in Django + Python that interact with web services (written in JAVA).\nNow all the database management part is done by web-services i.e. all CRUD operations to actual database is done by web-services.\n\nNow i have to track all User Activities done on my website in some log table.\nLike If User posted a new article, then a new row is created into Articles table by web-services and side by side, i need to add a new row into log table , something like \"User : Raman has posted a new article (with ID, title etc)\"\nI have to do this for all Objects in my database like \"Article\", \"Media\", \"Comments\" etc\n\nNote : I am using PostgreSQL\n\nSo what is the best way to achieve this..?? (Should I do it in PostgreSQL OR JAVA ..??..And How..??)","AnswerCount":5,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":2693,"Q_Id":9942206,"Users Score":0,"Answer":"In your log table you can have various columns, including:\n\nuser_id (the user that did the action)\nactivity_type (the type of activity, such as view or commented_on)\nobject_id (the actual object that it concerns, such as the Article or Media)\nobject_type (the type of object; this can be used later, in combination with object_id to lookup the object in the database)\n\nThis way, you can keep track of all actions the users do. You'd need to update this table whenever something happens that you wish to track.","Q_Score":0,"Tags":"java,python,django,postgresql,user-activity","A_Id":9942327,"CreationDate":"2012-03-30T11:39:00.000","Title":"How to store all user activites in a website..?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a web application build in Django + Python that interact with web services (written in JAVA).\nNow all the database management part is done by web-services i.e. all CRUD operations to actual database is done by web-services.\n\nNow i have to track all User Activities done on my website in some log table.\nLike If User posted a new article, then a new row is created into Articles table by web-services and side by side, i need to add a new row into log table , something like \"User : Raman has posted a new article (with ID, title etc)\"\nI have to do this for all Objects in my database like \"Article\", \"Media\", \"Comments\" etc\n\nNote : I am using PostgreSQL\n\nSo what is the best way to achieve this..?? (Should I do it in PostgreSQL OR JAVA ..??..And How..??)","AnswerCount":5,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":2693,"Q_Id":9942206,"Users Score":1,"Answer":"So, you have UI <-> Web Services <-> DB\nSince the web services talk to the DB, and the web services contain the business logic (i.e. I guess you validate stuff there, create your queries and execute them), then the best place to 'log' activities is in the services themselves.\nIMO, logging PostgreSQL transactions is a different thing. It's not the same as logging 'user activities' anymore.\nEDIT: This still means you create DB schema for 'logs' and write them to DB.\nSecond EDIT: Catching log worthy events in the UI and then logging them from there might not be the best idea either. You will have to rewrite logging if you ever decide to replace the UI, or for example, write an alternate UI for, say mobile devices, or something else.","Q_Score":0,"Tags":"java,python,django,postgresql,user-activity","A_Id":9942819,"CreationDate":"2012-03-30T11:39:00.000","Title":"How to store all user activites in a website..?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm trying to implement an script that reads the content(files and folders) of a certain directory and writes it in a database. My goal is create an software that allows me to organize those files and folders relating description and tags to them, without affecting the correspondig physical files in the disk.\nBut for now I'm facing a logical problem: How do I make a direct connection between that physical file and the database register? I want that, even if the physical file, for some reason, is edited or moved to another folder inside the root directory, the software is still able to relate that file with its original register in the database.\nMy first idea was to use a checksum hash to identify every file but, I'm guessing that if the file is edited, so does the hash, doesn't it? Besides that, I also think that a folder itself can't be checked that way.\nAnother solution that came up to my mind was applying a unique key in the beginning of every file and folder name in the directory. That may work, but it seems to me like an improvised solution and, therefore, I'mhoping that there may be another way to do it that I haven't considered yet.\nDoes anyone have an advice on that?","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":114,"Q_Id":9977888,"Users Score":0,"Answer":"You can't.\nIt looks that there is no way to identify the file: neither by content nor by pathname.\nOne workaround might be: use path as id (and use them as reference in the DB) and do not use system tools (like mv) to move files but your own script which updates the file system and the database.","Q_Score":0,"Tags":"php,python,database,windows,linux","A_Id":9978197,"CreationDate":"2012-04-02T14:00:00.000","Title":"How to link a file to a database?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am requesting a web page and want to cache the page data as a raw html string. (First I escaped the data string) I use sqlite3 to save my data on. When I tried give the byte_string in dictionary, or tuple, using placeholders in request, it raise \"Programming Error\" saying to convert the application to use unicode strings. I save it as SQLITE3 TEXT datatype.\nI tried data.encode(\"utf-8\") and encode(\"utf-8\") both raises the same error\nUnicodeDecodeError: 'utf8' codec can't decode byte 0xf6 in position 11777: invalid start byte\nI know it contains a strange character, this character is '\u00f6'. How can i solve this problem.\nDo i need use BLOB datatype of sqlite3","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":241,"Q_Id":9991854,"Users Score":0,"Answer":"You should .decode with the correct encoding. In this case Latin 1 or CP1252. \u00bb\u00f6\u00ab is obviously not 0xf6 in UTF-8 so why should it work?","Q_Score":0,"Tags":"python,unicode,utf-8,sqlite","A_Id":9991929,"CreationDate":"2012-04-03T10:57:00.000","Title":"How to convert a stringbyte(raw html string) to sqlite3 TEXT supporting unicode in Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Ok so I have a script that connects to a mssql db and i need to run as a service which I have already accomplished but when I run it as a service it overrides my credentials that I have put in when i connect to the db with the ad computer account.\nIt runs perfect when i run it on its own and not as a service.\nMy Connection String is:\n\n'DRIVER={SQL Server};SERVER=MyServer;DATABASE=MyDB;UID=DOMAIN\\myusername;PWD=A;Trusted_Connection=True'\n\nThe Error is:\n\nError: ('28000', \"[28000] [Microsoft][ODBC SQL Server Driver][SQL Server]Login failed for user 'DOMAIN\\COMPUTERNAME')\n\nAny Advice?","AnswerCount":2,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":7735,"Q_Id":10000256,"Users Score":2,"Answer":"In the last project I worked on, I found that DRIVER={SQL Server};SERVER=SERVERNAME;DATABASE=DBName is sufficient to initiate a db connection in trusted mode.\nIf it still does not work, it is probably either\n1) the account DEEPTHOUGHT  on mssql server is not set up properly. \n2) the runAs in the service is not set up properly (why error message mentions 'ComputerName' instead of 'DEEPTHOUGHT'?)","Q_Score":4,"Tags":"python,sql-server,py2exe,pyodbc","A_Id":10001004,"CreationDate":"2012-04-03T19:46:00.000","Title":"Failed to Login as 'Domain\\ComputerName' pyodbc with py2exe","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I need a unique datastore key for users authenticated via openid with the python 2.7 runtime for the google apps engine.  \nShould I use User.federated_identity() or User.federated_provider() + User.federated_identity()?  \nIn other words is User.federated_identity() unique for ALL providers or just one specific provider?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":194,"Q_Id":10002209,"Users Score":2,"Answer":"User.federated_identity() \"Returns the user's OpenID identifier.\", which is unique by definition (it's a URL that uniquely identifies the user).","Q_Score":2,"Tags":"python,google-app-engine,authentication","A_Id":10023490,"CreationDate":"2012-04-03T22:13:00.000","Title":"Generating a unique data store key from a federated identity","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I'm writing a Oracle of Bacon type website that involves a breadth first search on a very large directed graph (>5 million nodes with an average of perhaps 30 outbound edges each). This is also essentially all the site will do, aside from display a few mostly text pages (how it works, contact info, etc.). I currently have a test implementation running in Python, but even using Python arrays to efficiently represent the data, it takes >1.5gb of RAM to hold the whole thing. Clearly Python is the wrong language for a low-level algorithmic problem like this, so I plan to rewrite most of it in C using the Python\/C bindings. I estimate that this'll take about 300 mb of RAM.\nBased on my current configuration, this will run through mod_wsgi in apache 2.2.14, which is set to use mpm_worker_module. Each child apache server will then load up the whole python setup (which loads the C extension) thus using 300 mb, and I only have 4gb of RAM. This'll take time to load and it seems like it'd potentially keep the number of server instances lower than it could otherwise be. If I understand correctly, data-heavy (and not client-interaction-heavy) tasks like this would typically get divorced from the server by setting up an SQL database or something of the sort that all the server processes could then query. But I don't know of a database framework that'd fit my needs.\nSo, how to proceed? Is it worth trying to set up a database divorced from the webserver, or in some other way move the application a step farther out than mod_wsgi, in order to maybe get a few more server instances running? If so, how could this be done?    \nMy first impression is that the database, and not the server, is always going to be the limiting factor. It looks like the typical Apache mpm_worker_module configuration has ServerLimit 16 anyways, so I'd probably only get a few more servers. And if I did divorce the database from the server I'd have to have some way to run multiple instances of the database as well (I already know that just one probably won't cut it for the traffic levels I want to support) and make them play nice with the server. So I've perhaps mostly answered my own question, but this is a kind of odd situation so I figured it'd be worth seeing if anyone's got a firmer handle on it. Anything I'm missing? Does this implementation make sense? Thanks in advance!\nTechnical details: it's a Django website that I'm going to serve using Apache 2.2.14 on Ubuntu 10.4.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":214,"Q_Id":10017645,"Users Score":1,"Answer":"First up, look at daemon mode of mod_wsgi and don't use embedded mode as then you can control separate to Apache child processes the number of Python WSGI application processes. Secondly, you would be better off putting the memory hungry bits in a separate backend process. You might use XML-RPC or other message queueing system to communicate with the backend processes, or even perhaps see if you can use Celery in some way.","Q_Score":2,"Tags":"python,database,django,apache,mod-wsgi","A_Id":10020054,"CreationDate":"2012-04-04T19:06:00.000","Title":"Maximizing apache server instances with large mod_wsgi application","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I've been doing some HA testing of our database and in my simulation of server death I've found an issue.\nMy test uses Django and does this:\n\nConnect to the database\nDo a query\nPull out the network cord of the server\nDo another query\n\nAt this point everything hangs indefinitely within the mysql_ping function. As far as my app is concerned it is connected to the database (because of the previous query), it's just that the server is taking a long time to respond...\nDoes anyone know of any ways to handle this kind of situation? connect_timeout doesn't work as I'm already connected. read_timeout seems like a somewhat too blunt instrument (and I can't even get that working with Django anyway).\nSetting the default socket timeout also doesn't work (and would be vastly too blunt as this would affect all socket operations and not just MySQL).\nI'm seriously considering doing my queries within threads and using Thread.join(timeout) to perform the timeout.\nIn theory, if I can do this timeout then reconnect logic should kick in and our automatic failover of the database should work perfectly (kill -9 on affected processes currently does the trick but is a bit manual!).","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":181,"Q_Id":10018055,"Users Score":0,"Answer":"I would think this would be more inline with setting a read_timeout on your front-facing webserver.  Any number of reasons could exist to hold up your django app indefinitely.  While you have found one specific case there could be many more (code errors, cache difficulties, etc).","Q_Score":2,"Tags":"python,django,mysql-python","A_Id":10192810,"CreationDate":"2012-04-04T19:35:00.000","Title":"How can I detect total MySQL server death from Python?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am having a problem and not sure if this is possible at all, so if someone could point me in the right direction.\nI need to open a file from a webpage, open it in excel and save the file.\nThe problem I am running into the file name on the website has a file name ( not an active link ) and then it will have a \"download \" button that is not specific to the file I need to download. So instead of the download button being \"file1todaysdate\",  they are nothing that I could use from day to day.\nIs there a way I could locate file name then grab the file from the download icon? then save in excel? If not sorry for wasting time.","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1137,"Q_Id":10023418,"Users Score":0,"Answer":"Examine the Content-Disposition header of the response to discover what the server wants you to call the file.","Q_Score":2,"Tags":"python","A_Id":10023435,"CreationDate":"2012-04-05T06:05:00.000","Title":"Python File Download","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am trying to do a parser, that reads several excel files. I need values usually at the bottom of a row where you find a sum of all upper elements. So the cell value is actually \"=sum()\" or \"A5*0.5\" lets say... To a user that opens this file with excel it appears like  a number, which is fine. But if I try to read this value with ws.cell(x, y).value I do not get anything.\nSo my question is how to read this kind of fields with xlrd, if it is possible to read it like ws.cell(x, y).value or something similar?\nthanks","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":2953,"Q_Id":10029641,"Users Score":0,"Answer":"As per the link for your question,I have posted above, the author of xlrd says, 'The work is 'in-progress' but is not likely to be available soon as the focus of xlrd lies elsewhere\". By this, I assume that there is nothing much you can do about it. Note: this is based on author's comment on Jan, 2011.","Q_Score":2,"Tags":"python,excel,xlrd","A_Id":10029868,"CreationDate":"2012-04-05T13:36:00.000","Title":"how to read formulas with xlrd","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Let's say I have Python process 1 on machine 1 and Python process 2 on machine 2. Both processes are the same and process data sent by a load balancer.\nBoth processes need to interact with a database - in my case Postgres so each process needs to know what database it should talk to, it needs to have the right models on each machine etc. It's just too tightly coupled.  \nThe ideal would be to have a separate process dealing with the database stuff like connections, keeping up with db model changes, requests to the databases etc. What my process 1 and process 2 should do is just say I have some JSON data that needs to be saved or updated on this table or I need this data in json format. \nMaybe I'm asking the impossible but is there any Python solution that would at least make life a little easier when it comes to having distributed processes interacting with relational databases in the most decoupled way possible?","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":157,"Q_Id":10044862,"Users Score":1,"Answer":"If it's db connection information you're interested in, I recently wrote a service for this. Each process has token(s) set in configuration and uses those to query the service for db connection info. The data layer uses that info to create connections, no DSN's are stored. On the server side, you just maintain a dictionary of token->DSN mappings.\nYou could do connection pooling with bpgergo's suggestion, but you should still include an authentication or identification method. That way, if there's a network intrusion, malicious clients may not be able to impersonate one of the clients.\nThe service implementation is broken into a few parts:\n\nA RESTful service that supports calls of the form http:\/\/192.168.1.100\/getConnection?token=mytokenstring\nA key-value storage system that stores a mapping like {'mytokenstring': {'dbname': 'db', 'ip': '192.168.1.101', 'user': 'dbuser', 'password': 'password', ..}\n\nThis system shouldn't be on the front end network, but if your web tier is compromised, this approach doesn't buy you any protection for the db.\n\nA db object that on instantiation, retrieves a dsn using an appropriate token and creates a new db connection.\n\nYou should re-use this connection object for the rest of the page response if you can. The response time from the service will be fast, but there's a lot more overhead required for db connections.\n\n\nOnce implemented, some care is required for handing schema incompatibilities when switching the dsn info behind a token. You may be able to resolve this by pinning a token to a user session, etc.","Q_Score":1,"Tags":"python,database,distributed-computing","A_Id":10045103,"CreationDate":"2012-04-06T14:25:00.000","Title":"Any Python solution for having distributed processes interact with relational databases in the most decoupled way possible?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"The documentation for Pandas has numerous examples of best practices for working with data stored in various formats.\nHowever, I am unable to find any good examples for working with databases like MySQL for example.\nCan anyone point me to links or give some code snippets of how to convert query results using mysql-python to data frames in Pandas efficiently ?","AnswerCount":13,"Available Count":1,"Score":0.0614608973,"is_accepted":false,"ViewCount":123656,"Q_Id":10065051,"Users Score":4,"Answer":"pandas.io.sql.frame_query is deprecated. Use pandas.read_sql instead.","Q_Score":97,"Tags":"python,pandas","A_Id":27531471,"CreationDate":"2012-04-08T18:01:00.000","Title":"python-pandas and databases like mysql","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am developing an application designed for a secretary to use. She has a stack of hundreds of ballot forms which have a number of questions on them, and wishes to input this data into a program to show the total votes for each answer. Each question has a number of answers.\nFor example:\nQ: \"Re-elect current president of the board\"\nA: Choice between \"Yes\" or \"No\" or \"Neutral\"\nYear on year the questions can change, as well as the answers, but the current application used in the company is hard coded with the questions and answers of last year.\nMy aim is to create an app (in Django\/Python) which allows the secretary to add\/delete questions and answers as she wishes. I am relatively new to Django... I have created an app in University and know how to create basic models and implement the Twitter bootstrap for the GUI.\nBut I'm a little confused about how to enable the secretary to add custom fields in (which are obviously defined in SQL). Does anyone have any small tips on how to get started? By the way, I recognize that this could be achievable using the admin part of website and would welcome any suggestions about that.\nThank you.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":72,"Q_Id":10066573,"Users Score":5,"Answer":"You really don't want to implement each question\/answer as a separate DB field.\nInstead, make a table of questions and a table of answers, and have a field in the answers table (in general, a ForeignKey) to indicate which question a given answer is associated with.","Q_Score":0,"Tags":"python,sql,django","A_Id":10066588,"CreationDate":"2012-04-08T21:14:00.000","Title":"Adding field to SQL table from Django Application","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have to build a web application which uses Python, php and MongoDB.\n\nPython - For offline database populating on my local home machine and then exporting db to VPS. Later I am planning to schedule this job using cron.\nPHP - For web scripting.\n\nThe VPS I wish to buy supports Python and LAMP Stack but not mongoDB (myhosting.com LAMP stack VPS) by default. Now since mongoDB isn't supported by default, I would have to install mongoDB manually on VPS. So what I want to know is that, had it been my VPS would have supported mongoDB would I have benefitted in terms of performance and scalability.\nAlso can someone please suggest a VPS suitable in my case.","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":810,"Q_Id":10073934,"Users Score":1,"Answer":"If the vps you are looking at restricts the packages you can install, and you need something that they prohibit, I would look for another vps.  Both rackspace and amazon a range of instances, and numerous supported os.  With either of them you choose your operating system and are free to install whatever you want.","Q_Score":1,"Tags":"php,python,mongodb,vps","A_Id":10074035,"CreationDate":"2012-04-09T13:28:00.000","Title":"Performance of MongoDB on VPS or cloud service not having mongoDB installed","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a desktop python application whose data backend is a MySQL database, but whose previous database was a network-accessed xml file(s). When it was xml-powered, I had a thread spawned at the launch of the application that would simply check the xml file for changes and whenever the date modified changed (due to any user updating it), the app would refresh itself so multiple users could use and see the changes of the app as they went about their business.\nNow that the program has matured and is venturing toward an online presence so it can be used anywhere. Xml is out the window and I'm using MySQL with SQLAlchemy as the database access method. The plot thickens, however, because the information is no longer stored in one xml file but rather it is split into multiple tables in the SQL database. This complicates the idea of some sort of 'last modified' table value or structure. Thus the question, how do you inform the users that the data has changed and the app needs to refresh? Here are some of my thoughts:\n\nEach table needs a last-modified column (this seems like the worst option ever)\nA separate table that holds some last modified column?\nSome sort of push notification through a server?\nIt should be mentioned that I have the capability of running perhaps a very small python script on the same server hosting the SQL db that perhaps the app could connect to and (through sockets?) it could pass information to and from all connected clients?\n\nSome extra information:\n\nThe information passed back and forth would be pretty low-bandwidth. Mostly text with the potential of some images (rarely over 50k).\nNumber of clients at present is very small, in the tens. But the project could be picked up by some bigger companies with client numbers possibly getting into the hundreds. Even still the bandwidth shouldn't be a problem for the foreseeable future.\n\nAnyway, somewhat new territory for me, so what would you do? Thanks in advance!","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":450,"Q_Id":10091108,"Users Score":0,"Answer":"As I understand this is not a client-server application, but rather an application that has a common remote storage.\nOne idea would be to change to web services (this would solve most of your problems on the long run).\nAnother idea (if you don't want to switch to web) is to refresh periodically the data in your interface by using a timer.\nAnother way (and more complicated) would be to have a server that receives all the updates, stores them in the database and then pushes the changes to the other connected clients.\nThe first 2 ideas you mentioned will have maintenance, scalability and design uglyness issues.\nThe last 2 are a lot better in my opinion, but I still stick to web services as being the best.","Q_Score":0,"Tags":"python,mysql,notifications","A_Id":10091535,"CreationDate":"2012-04-10T14:55:00.000","Title":"Best way to inform user of an SQL Table Update?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Looking for any advice I can get.  \nI have 16 virtual CPUs all writing to a single remote MongoDB server.  The machine that's being written to is a 64-bit machine with 32GB RAM, running Windows Server 2008 R2.  After a certain amount of time, all the CPUs stop cold (no gradual performance reduction), and any attempt to get a Remote Desktop Connection hangs.  \nI'm writing from Python via pymongo, and the insert statement is \"[collection].insert([document], safe=True)\"\nI decided to more actively monitor my server as the distributed write job progressed, remoting in from time to time and checking the Task Manager.  What I see is a steady memory creep, from 0.0GB all the way up to 29.9GB, in a fairly linear fashion.  My leading theory is therefore that my writes are filling up the memory and eventually overwhelming the machine.  \nAm I missing something really basic?  I'm new to MongoDB, but I remember that when writing to a MySQL database, inserts are typically followed by commits, where it's the commit statement that actually makes sure the record is written.  Here I'm not doing any commits...?\nThanks,\nDave","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":97,"Q_Id":10114431,"Users Score":0,"Answer":"Try it with journaling turned off and see if the problem remains.","Q_Score":0,"Tags":"mongodb,python-2.7,windows-server-2008-r2,pymongo,distributed-transactions","A_Id":10157192,"CreationDate":"2012-04-11T21:43:00.000","Title":"Distributed write job crashes remote machine with MongoDB server","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"We moved our SQL Server 2005 database to a new physical server, and since then it has been terminating any connection that persist for 30 seconds.\nWe are experiencing this in Oracle SQL developer and when connecting from python using pyodbc\nEverything worked perfectly before, and now python returns this error after 30 seconds:\n('08S01', '[08S01] [FreeTDS][SQL Server]Read from the server failed (20004) (SQLExecDirectW)')","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":549,"Q_Id":10145201,"Users Score":1,"Answer":"First of all what you need is profile the sql server to see if any activity is happening. Look for slow running queries, CPU and memory bottlenecks. \nAlso you can include the timeout in the querystring like this: \n\"Data Source=(local);Initial Catalog=AdventureWorks;Integrated Security=SSPI;Connection Timeout=30\"; \nand extend that number if you want.\nBut remember \"timeout\" doesn't means time connection, this is just the time to wait while trying to establish a connection before terminating.\nI think this problem is more about database performance or maybe a network issue.","Q_Score":0,"Tags":"python,sql,sql-server,sql-server-2005,oracle-sqldeveloper","A_Id":10145890,"CreationDate":"2012-04-13T17:06:00.000","Title":"SQL Server 2005 terminating connections after 30 sec","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I've extended sorl-thumbnail's KVStoreBase class, and made a key-value backend that uses a single MongoDB collection.\nThis was done in order to avoid installing a discrete key-value store (e.g. Redis).\nShould I clear the collection every once in a while?\nWhat are the downsides?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":298,"Q_Id":10146087,"Users Score":0,"Answer":"Only clear the collection if low disk usage is more important to you than fast access times.\nThe downsides are that your users will all hit un-cached thumbs simultaneously (And simultaneously begin recomputing them).\nJust run python manage.py thumbnail cleanup\n\nThis cleans up the Key Value Store from stale cache. It removes references to images that do not exist and thumbnail references and their actual files for images that do not exist. It removes thumbnails for unknown images.","Q_Score":2,"Tags":"django,mongodb,python-imaging-library,sorl-thumbnail","A_Id":11557675,"CreationDate":"2012-04-13T18:11:00.000","Title":"Using sorl-thumbnail with MongoDB storage","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am currently writing a script in Python which uploads data to a localhost MySql DB. I am now looking to relocate this MySql DB to a remote server with a static IP address. I have a web hosting facility but this only allows clients to connect to the MySql DB if I specify the domain \/ IP address from which clients will connect. My Python script will be ran on a number of computers that will connect via a mobile broadband dongle and therefore, the IP addresses will vary on a day-to-day basis as the IP address is allocated dynamically.\nAny suggestions on how to overcome this issue either with my web hosting facility (cPanel) or alternatively, any suggestions on MySql hosting services that allow remote access from any IP addresses (assuming they successfully authenticate with passwords etc...) Would SSH possibly address this and allow me to transmit data?","AnswerCount":3,"Available Count":1,"Score":0.1325487884,"is_accepted":false,"ViewCount":1360,"Q_Id":10157380,"Users Score":2,"Answer":"Go to Cpanel and add the wildcard % on remote Mysql Connection options (cPanel > Remote MySQL)","Q_Score":0,"Tags":"python,mysql,mysql-python","A_Id":10157409,"CreationDate":"2012-04-14T21:07:00.000","Title":"Remote Access to MySql DB (Hosting Options)","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am trying to read phonenumber field from xls using xlrd (python). But, I always get float no.\ne.g. I get phone number as 8889997777.0\nHow can I get rid of floating format and convert it to string to store it in my local mongodb within python as string as regular phone number e.g. 8889997777","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":2371,"Q_Id":10169949,"Users Score":0,"Answer":"Did you try using int(phoneNumberVar) or in your case int(8889997777.0)?","Q_Score":2,"Tags":"python,string,floating-point,xls,xlrd","A_Id":10169963,"CreationDate":"2012-04-16T07:06:00.000","Title":"python xlrd reading phone nunmber from xls becomes float","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am trying to read phonenumber field from xls using xlrd (python). But, I always get float no.\ne.g. I get phone number as 8889997777.0\nHow can I get rid of floating format and convert it to string to store it in my local mongodb within python as string as regular phone number e.g. 8889997777","AnswerCount":2,"Available Count":2,"Score":0.3799489623,"is_accepted":false,"ViewCount":2371,"Q_Id":10169949,"Users Score":4,"Answer":"You say:\n\npython xlrd reading phone nunmber from xls becomes float\n\nThis is incorrect. It is already a float inside your xls file. xlrd reports exactly what it finds.\nYou can use str(int(some_float_value)) to do what you want to do.","Q_Score":2,"Tags":"python,string,floating-point,xls,xlrd","A_Id":10170261,"CreationDate":"2012-04-16T07:06:00.000","Title":"python xlrd reading phone nunmber from xls becomes float","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I would like to know if somebody knows a way to customize the csv output in htsql, and especially the delimiter and the encoding ?\nI would like to avoid iterating over each result and find a way through configuration and\/or extensions.\nThank in advance.\nAnthony","AnswerCount":1,"Available Count":1,"Score":0.537049567,"is_accepted":false,"ViewCount":170,"Q_Id":10205990,"Users Score":3,"Answer":"If you want TAB as a delimiter, use tsv format (e.g. \/query\/:tsv instead of \/query\/:csv).\nThere is no way to specify the encoding other than UTF-8.  You can reencode the output manually on the client.","Q_Score":1,"Tags":"python,sql,htsql","A_Id":10210348,"CreationDate":"2012-04-18T08:52:00.000","Title":"Customizing csv output in htsql","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am new in OpenERP, I have installed OpenERP v6. I want to know how can I insert data in database? Which files I have to modify to do the job? (files for the SQL code)","AnswerCount":3,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":794,"Q_Id":10208147,"Users Score":0,"Answer":"OpenERP works with PostgreSQl as the Back-end Structure.\nPostgresql is managed by pgadmin3 (Postgres GUI),you can write sql queries there and can add\/delete records from there.\nIt is not advisable to insert\/remove data directly into Database!!!!","Q_Score":2,"Tags":"python,postgresql,openerp","A_Id":10208766,"CreationDate":"2012-04-18T11:10:00.000","Title":"OpenERP: insert Data code","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am new in OpenERP, I have installed OpenERP v6. I want to know how can I insert data in database? Which files I have to modify to do the job? (files for the SQL code)","AnswerCount":3,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":794,"Q_Id":10208147,"Users Score":0,"Answer":"The addition of columns in the .py files of the corresponding modules you want to chnage will insert coumns to the pgadmin3 also defenition of classes will create tables...when the fields are displayed in xml file and values are entered to the fields through the interface the values get stored to the table values to the database...","Q_Score":2,"Tags":"python,postgresql,openerp","A_Id":10225346,"CreationDate":"2012-04-18T11:10:00.000","Title":"OpenERP: insert Data code","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a web application that has been done using Cakephp with MySql as the DB. The webapp also exposes a set of web services that get and update data to the MySQL DB. I will like to extend the app to provide a fresh set of web services but will like to use a python based framework like web2py\/django etc. Since both will be working of the same DB will it cause any problems? The reason I want to do it is because the initial app\/web services was done by somebody else and now I want to extend it and am more comfortable using python\/web2py that php\/cakephp.","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":73,"Q_Id":10233187,"Users Score":0,"Answer":"This is one of the reasons to use RDBMS to provide access for different users and applications to the same data. There should absolutely no problem with this.","Q_Score":0,"Tags":"php,python,mysql,django,cakephp","A_Id":10233231,"CreationDate":"2012-04-19T17:08:00.000","Title":"Same MySql DB working with a php and a python framework","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm trying to drop a few tables with the \"DROP TABLE\" command but for a unknown reason, the program just \"sits\" and doesn't delete the table that I want it to in the database.\nI have 3 tables in the database:\nProduct, Bill and Bill_Products which is used for referencing products in bills.\nI managed to delete\/drop Product, but I can't do the same for bill and Bill_Products.\nI'm issuing the same \"DROP TABLE Bill CASCADE;\" command but the command line just stalls. I've also used the simple version without the CASCADE option.\nDo you have any idea why this is happening?\nUpdate:\nI've been thinking that it is possible for the databases to keep some references from products to bills and maybe that's why it won't delete the Bill table.\nSo, for that matter i issued a simple SELECT * from Bill_Products and after a few (10-15) seconds (strangely, because I don't think it's normal for it to last such a long time when there's an empty table) it printed out the table and it's contents, which are none. (so apparently there are no references left from Products to Bill).","AnswerCount":8,"Available Count":4,"Score":0.1243530018,"is_accepted":false,"ViewCount":55426,"Q_Id":10317114,"Users Score":5,"Answer":"Had the same problem.\nThere were not any locks on the table.\nReboot helped.","Q_Score":42,"Tags":"python,database,django,postgresql","A_Id":19072541,"CreationDate":"2012-04-25T13:50:00.000","Title":"Postgresql DROP TABLE doesn't work","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm trying to drop a few tables with the \"DROP TABLE\" command but for a unknown reason, the program just \"sits\" and doesn't delete the table that I want it to in the database.\nI have 3 tables in the database:\nProduct, Bill and Bill_Products which is used for referencing products in bills.\nI managed to delete\/drop Product, but I can't do the same for bill and Bill_Products.\nI'm issuing the same \"DROP TABLE Bill CASCADE;\" command but the command line just stalls. I've also used the simple version without the CASCADE option.\nDo you have any idea why this is happening?\nUpdate:\nI've been thinking that it is possible for the databases to keep some references from products to bills and maybe that's why it won't delete the Bill table.\nSo, for that matter i issued a simple SELECT * from Bill_Products and after a few (10-15) seconds (strangely, because I don't think it's normal for it to last such a long time when there's an empty table) it printed out the table and it's contents, which are none. (so apparently there are no references left from Products to Bill).","AnswerCount":8,"Available Count":4,"Score":0.049958375,"is_accepted":false,"ViewCount":55426,"Q_Id":10317114,"Users Score":2,"Answer":"Old question but ran into a similar issue. Could not reboot the database so tested a few things until this sequence worked :\n\ntruncate table foo;\ndrop index concurrently foo_something; times 4-5x\nalter table foo drop column whatever_foreign_key; times 3x\nalter table foo drop column id;\ndrop table foo;","Q_Score":42,"Tags":"python,database,django,postgresql","A_Id":40749694,"CreationDate":"2012-04-25T13:50:00.000","Title":"Postgresql DROP TABLE doesn't work","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm trying to drop a few tables with the \"DROP TABLE\" command but for a unknown reason, the program just \"sits\" and doesn't delete the table that I want it to in the database.\nI have 3 tables in the database:\nProduct, Bill and Bill_Products which is used for referencing products in bills.\nI managed to delete\/drop Product, but I can't do the same for bill and Bill_Products.\nI'm issuing the same \"DROP TABLE Bill CASCADE;\" command but the command line just stalls. I've also used the simple version without the CASCADE option.\nDo you have any idea why this is happening?\nUpdate:\nI've been thinking that it is possible for the databases to keep some references from products to bills and maybe that's why it won't delete the Bill table.\nSo, for that matter i issued a simple SELECT * from Bill_Products and after a few (10-15) seconds (strangely, because I don't think it's normal for it to last such a long time when there's an empty table) it printed out the table and it's contents, which are none. (so apparently there are no references left from Products to Bill).","AnswerCount":8,"Available Count":4,"Score":0.0,"is_accepted":false,"ViewCount":55426,"Q_Id":10317114,"Users Score":0,"Answer":"The same thing happened for me--except that it was because I forgot the semicolon. face palm","Q_Score":42,"Tags":"python,database,django,postgresql","A_Id":69412889,"CreationDate":"2012-04-25T13:50:00.000","Title":"Postgresql DROP TABLE doesn't work","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm trying to drop a few tables with the \"DROP TABLE\" command but for a unknown reason, the program just \"sits\" and doesn't delete the table that I want it to in the database.\nI have 3 tables in the database:\nProduct, Bill and Bill_Products which is used for referencing products in bills.\nI managed to delete\/drop Product, but I can't do the same for bill and Bill_Products.\nI'm issuing the same \"DROP TABLE Bill CASCADE;\" command but the command line just stalls. I've also used the simple version without the CASCADE option.\nDo you have any idea why this is happening?\nUpdate:\nI've been thinking that it is possible for the databases to keep some references from products to bills and maybe that's why it won't delete the Bill table.\nSo, for that matter i issued a simple SELECT * from Bill_Products and after a few (10-15) seconds (strangely, because I don't think it's normal for it to last such a long time when there's an empty table) it printed out the table and it's contents, which are none. (so apparently there are no references left from Products to Bill).","AnswerCount":8,"Available Count":4,"Score":0.0996679946,"is_accepted":false,"ViewCount":55426,"Q_Id":10317114,"Users Score":4,"Answer":"I ran into this today, I was issuing a:\nDROP TABLE TableNameHere\nand getting ERROR:  table \"tablenamehere\" does not exist. I realized that for case-sensitive tables (as was mine), you need to quote the table name:\nDROP TABLE \"TableNameHere\"","Q_Score":42,"Tags":"python,database,django,postgresql","A_Id":60367779,"CreationDate":"2012-04-25T13:50:00.000","Title":"Postgresql DROP TABLE doesn't work","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Ive been reading the Django Book and its great so far, unless something doesn't work properly. I have been trying for two days to install the psycogp2 plugin with no luck.\ni navigate to the unzipped directory and run setup.py install and it returns \"You must have postgresql dev for building a serverside extension or libpq-dev for client side.\"\nI don't know what any of this means, and google returns results tossing a lot of terms I don't really understand.\nIve been trying to learn django for abut a week now plus linux so any help would be great. Thanks\nBtw, I have installed postgresql and pgadminIII from installer pack. \nI also tried sudo apt-get post.... and some stuff happens...but Im lost.","AnswerCount":4,"Available Count":2,"Score":-0.049958375,"is_accepted":false,"ViewCount":4157,"Q_Id":10321568,"Users Score":-1,"Answer":"sudo apt-get install python-psycopg2 should work fine since it worked solution for me as well.","Q_Score":6,"Tags":"python,django","A_Id":20124244,"CreationDate":"2012-04-25T18:25:00.000","Title":"Django with psycopg2 plugin","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Ive been reading the Django Book and its great so far, unless something doesn't work properly. I have been trying for two days to install the psycogp2 plugin with no luck.\ni navigate to the unzipped directory and run setup.py install and it returns \"You must have postgresql dev for building a serverside extension or libpq-dev for client side.\"\nI don't know what any of this means, and google returns results tossing a lot of terms I don't really understand.\nIve been trying to learn django for abut a week now plus linux so any help would be great. Thanks\nBtw, I have installed postgresql and pgadminIII from installer pack. \nI also tried sudo apt-get post.... and some stuff happens...but Im lost.","AnswerCount":4,"Available Count":2,"Score":0.1488850336,"is_accepted":false,"ViewCount":4157,"Q_Id":10321568,"Users Score":3,"Answer":"I'm working on Xubuntu (12.04) and I have encountered the same error when I wanted to install django-toolbelt. I solved this error with the following operations :\n\nsudo apt-get install python-dev\nsudo apt-get install libpq-dev\nsudo apt-get install python-psycopg2\n\nI hope this informations may be helpful for someone else.","Q_Score":6,"Tags":"python,django","A_Id":22528687,"CreationDate":"2012-04-25T18:25:00.000","Title":"Django with psycopg2 plugin","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a daemon process witch spawns child processes using multiprocessing to do some work, each child process opens its own connection handle do DB (postgres in my case). Jobs to processes are passed via Queue and if queue is empty processes invoke sleep for some time, and recheck queue\nHow can I implement \"graceful shutdown\" on SIGTERM? Each subprocess should terminate as fast as possible, with respect of closing\/terminating current cursor\/transaction and db connection, and opened files.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":403,"Q_Id":10322422,"Users Score":5,"Answer":"Store all the open files\/connections\/etc. in a global structure, and close them all and exit in your SIGTERM handler.","Q_Score":3,"Tags":"python,database,multiprocessing,signals","A_Id":10322481,"CreationDate":"2012-04-25T19:27:00.000","Title":"Gracefull shutdown, close db connections, opened files, stop work on SIGTERM, in multiprocessing","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":0},{"Question":"I have done my homework in reading about protection against sql injection attacks: I know that I need to use parameter binding but:\n\nI already do this, thank you.\nI know that some of the db drivers my users use implement parameter binding in the most stupid possible way. i.e., they are prone to sql injection attacks. I could try to restrict which db driver they can use but, this strategy is doomed to fail.\nEven if I use a decent db driver, I do not trust myself to not forget to use parameter binding at least once\n\nSo, I would like to add an extra layer of protection by adding extra sanitization of http-facing user input. The trick is that I know that this is hard to do in general so I would rather use a well-audited well-designed third-party library that was written by security professionals to escape input strings into less dangerous content but I could not find any obvious candidate. I use python so, I would be interested in python-based solutions but other suggestions are fine if I can bind them to python.","AnswerCount":4,"Available Count":4,"Score":0.049958375,"is_accepted":false,"ViewCount":621,"Q_Id":10329486,"Users Score":1,"Answer":"I don't know if this is in any way applicable but I am just putting it up there for completeness and experts can downvote me at will... not to mention i have concerns about its performance in some cases.\nI was once tasked with protecting an aging web app written in classic asp against sql injection (they were getting hit pretty bad at the time)\nI dint have time to go through all code (not may choice) so I added a method to one of our standard include files that looked at everything being submitted by the user (iterated through request params) and checked it for blacklisted html tags (e.g. script tags) and sql injection signs (e.g. \";--\" and \"';shutdown\")..\nIf it found one it redirected the user told them they submission was suspicious and if they have an issue call or email.. blah blah.\nIt also recorded the injection attempt in a table (once it have been escaped) and details about the IP address time etc of the attack.. \nOverall it worked a treat.. at least the attacks stopped.\nevery web technology i have used has some way of fudging something like this in there and it only took me about a day to dev and test..\nhope it helps, I would not call it an industry standard or anything\ntl;dr?:\nCheck all request params against a blacklist of strings","Q_Score":0,"Tags":"python,sql,sql-injection","A_Id":10329694,"CreationDate":"2012-04-26T08:09:00.000","Title":"protecting against sql injection attacks beyond parameter binding","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have done my homework in reading about protection against sql injection attacks: I know that I need to use parameter binding but:\n\nI already do this, thank you.\nI know that some of the db drivers my users use implement parameter binding in the most stupid possible way. i.e., they are prone to sql injection attacks. I could try to restrict which db driver they can use but, this strategy is doomed to fail.\nEven if I use a decent db driver, I do not trust myself to not forget to use parameter binding at least once\n\nSo, I would like to add an extra layer of protection by adding extra sanitization of http-facing user input. The trick is that I know that this is hard to do in general so I would rather use a well-audited well-designed third-party library that was written by security professionals to escape input strings into less dangerous content but I could not find any obvious candidate. I use python so, I would be interested in python-based solutions but other suggestions are fine if I can bind them to python.","AnswerCount":4,"Available Count":4,"Score":1.2,"is_accepted":true,"ViewCount":621,"Q_Id":10329486,"Users Score":2,"Answer":"I already do this, thank you.\n\n\nGood;  with just this, you can be totally sure (yes, totally sure) that user inputs are being interpreted only as values.  You should direct your energies toward securing your site against other kinds of vulnerabilities (XSS and CSRF come to mind; make sure you're using SSL properly, et-cetera).\n\n\nI know that some of the db drivers my users use implement parameter binding in the most stupid possible way. i.e., they are prone to sql injection attacks. I could try to restrict which db driver they can use but, this strategy is doomed to fail.\n\n\nWell, there's no such thing as fool proof because fools are so ingenious.  If your your audience is determined to undermine all of your hard work for securing their data, you can't really do anything about it.  what you can do is determine which drivers you believe are secure, and generate a big scary warning when you detect that your users are using something else.\n\n\nEven if I use a decent db driver, I do not trust myself to not forget to use parameter binding at least once\n\n\n\nSo don't do that!\nDuring development, log every sql statement sent to your driver.  check, on a regular basis, that user data is never in this log (or logged as a separate event, for the parameters).\nSQL injection is basically string formatting.  You can usually follow each database transaction backwards to the original sql;  if user data is formatted into that somewhere along the way, you have a problem.  When scanning over projects, I find that I'm able to locate these at a rate of about one per minute, with effective use of grep and my editor of choice.  unless you have tens of thousands of different sql statements, going over each one shouldn't really be prohibitively difficult.\nTry to keep your database interactions well isolated from the rest of your application.  mixing sql in with the rest of your code makes it hard to mantain, or do the checks I've described above.  Ideally, you should go through some sort of database abstraction, (a full ORM or maybe something thinner), so that you can work on just your database related code when that's the task at hand.","Q_Score":0,"Tags":"python,sql,sql-injection","A_Id":10336420,"CreationDate":"2012-04-26T08:09:00.000","Title":"protecting against sql injection attacks beyond parameter binding","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have done my homework in reading about protection against sql injection attacks: I know that I need to use parameter binding but:\n\nI already do this, thank you.\nI know that some of the db drivers my users use implement parameter binding in the most stupid possible way. i.e., they are prone to sql injection attacks. I could try to restrict which db driver they can use but, this strategy is doomed to fail.\nEven if I use a decent db driver, I do not trust myself to not forget to use parameter binding at least once\n\nSo, I would like to add an extra layer of protection by adding extra sanitization of http-facing user input. The trick is that I know that this is hard to do in general so I would rather use a well-audited well-designed third-party library that was written by security professionals to escape input strings into less dangerous content but I could not find any obvious candidate. I use python so, I would be interested in python-based solutions but other suggestions are fine if I can bind them to python.","AnswerCount":4,"Available Count":4,"Score":0.0,"is_accepted":false,"ViewCount":621,"Q_Id":10329486,"Users Score":0,"Answer":"So, I would like to add an extra layer of protection by adding extra sanitization of http-facing user input. \n\nThis strategy is doomed to fail.","Q_Score":0,"Tags":"python,sql,sql-injection","A_Id":10336013,"CreationDate":"2012-04-26T08:09:00.000","Title":"protecting against sql injection attacks beyond parameter binding","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have done my homework in reading about protection against sql injection attacks: I know that I need to use parameter binding but:\n\nI already do this, thank you.\nI know that some of the db drivers my users use implement parameter binding in the most stupid possible way. i.e., they are prone to sql injection attacks. I could try to restrict which db driver they can use but, this strategy is doomed to fail.\nEven if I use a decent db driver, I do not trust myself to not forget to use parameter binding at least once\n\nSo, I would like to add an extra layer of protection by adding extra sanitization of http-facing user input. The trick is that I know that this is hard to do in general so I would rather use a well-audited well-designed third-party library that was written by security professionals to escape input strings into less dangerous content but I could not find any obvious candidate. I use python so, I would be interested in python-based solutions but other suggestions are fine if I can bind them to python.","AnswerCount":4,"Available Count":4,"Score":-0.049958375,"is_accepted":false,"ViewCount":621,"Q_Id":10329486,"Users Score":-1,"Answer":"Well in php, I use preg_replace to protect my website from being attacked by sql injection. preg_match can also be used. Try searching an equivalent function of this in python.","Q_Score":0,"Tags":"python,sql,sql-injection","A_Id":10329550,"CreationDate":"2012-04-26T08:09:00.000","Title":"protecting against sql injection attacks beyond parameter binding","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"We have developed an application using DJango 1.3.1, Python 2.7.2 using Database as SQL server 2008.  All these are hosted in Win 2008 R2 operating system on VM.  The clients has windows 7 as o\/s.\nWe developed application keeping in view with out VM, all of sudden client has come back saying they can only host the application on VM. Now the challnege is to access application from client to server which is on VM.\nIf anyone has done this kind of applications, request them share step to access the applicaiton on VM.  \nAs I am good at standalone systems, not having knowledge on VM accessbility.  \nWe have done all project and waiting to someone to respond ASAP.\nThanks in advance for your guidence.\nRegards,\nShiva.","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":422,"Q_Id":10331518,"Users Score":0,"Answer":"Maybe this could help you a bit, although my set-up is slightly different. I am running an ASP.NET web app developed on Windows7 via VMware fusion on OS X. I access the web app from outside the VM (browser of Mac or other computers\/phones within the network).\nHere are the needed settings:\n\nNetwork adapter set to (Bridged), so that the VM has its own IP address\nConfigure the VM to have a static IP\n\nAt this point, the VM is acting as its own machine, so you can access it as if it were another server sitting on the network.","Q_Score":0,"Tags":"django,wxpython,sql-server-2008-r2,vmware,python-2.7","A_Id":10331810,"CreationDate":"2012-04-26T10:21:00.000","Title":"Steps to access Django application hosted in VM from Windows 7 client","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"What's the best way to create an intentionally empty query in SQLAlchemy?\nFor example, I've got a few functions which build up the query (adding WHERE clauses, for example), and at some points I know that the the result will be empty.\nWhat's the best way to create a query that won't return any rows? Something like Django's QuerySet.none().","AnswerCount":4,"Available Count":1,"Score":1.0,"is_accepted":false,"ViewCount":9094,"Q_Id":10345327,"Users Score":34,"Answer":"If you need the proper return type, just return session.query(MyObject).filter(sqlalchemy.sql.false()).\nWhen evaluated, this will still hit the DB, but it should be fast.\nIf you don't have an ORM class to \"query\", you can use false() for that as well:\nsession.query(sqlalchemy.false()).filter(sqlalchemy.false())","Q_Score":36,"Tags":"python,sqlalchemy","A_Id":12837029,"CreationDate":"2012-04-27T05:41:00.000","Title":"SQLAlchemy: create an intentionally empty query?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm using django-1.4 , sqlite3 , django-facebookconnect\nFollowing instructions in Wiki to setup .\n\"python manage.py syncdb\" throws an error .\n\nCreating tables ...\nCreating table auth_permission\nCreating table auth_group_permissions\nCreating table auth_group\nCreating table auth_user_user_permissions\nCreating table auth_user_groups\nCreating table auth_user\nCreating table django_content_type\nCreating table django_session\nCreating table django_site\nCreating table blog_post\nCreating table blog_comment\nCreating table django_admin_log\nTraceback (most recent call last):\n  File \"manage.py\", line 10, in \n    execute_from_command_line(sys.argv)\n  File \"\/usr\/local\/lib\/python2.7\/dist-packages\/django\/core\/management\/init.py\", line 443, in execute_from_command_line\n    utility.execute()\n  File \"\/usr\/local\/lib\/python2.7\/dist-packages\/django\/core\/management\/init.py\", line 382, in execute\n    self.fetch_command(subcommand).run_from_argv(self.argv)\n  File \"\/usr\/local\/lib\/python2.7\/dist-packages\/django\/core\/management\/base.py\", line 196, in run_from_argv\n    self.execute(*args, **options.dict)\n  File \"\/usr\/local\/lib\/python2.7\/dist-packages\/django\/core\/management\/base.py\", line 232, in execute\n    output = self.handle(*args, **options)\n  File \"\/usr\/local\/lib\/python2.7\/dist-packages\/django\/core\/management\/base.py\", line 371, in handle\n    return self.handle_noargs(**options)\n  File \"\/usr\/local\/lib\/python2.7\/dist-packages\/django\/core\/management\/commands\/syncdb.py\", line 91, in handle_noargs\n    sql, references = connection.creation.sql_create_model(model, self.style, seen_models)\n  File \"\/usr\/local\/lib\/python2.7\/dist-packages\/django\/db\/backends\/creation.py\", line 44, in sql_create_model\n    col_type = f.db_type(connection=self.connection)\nTypeError: db_type() got an unexpected keyword argument 'connection'\n\nIs there any solution ??","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":282,"Q_Id":10356581,"Users Score":1,"Answer":"You should use django-facebook instead, it does that and more and it is actively supported :)","Q_Score":0,"Tags":"python,django,facebook,sqlite","A_Id":10486708,"CreationDate":"2012-04-27T19:17:00.000","Title":"Getting db_type() error while using django-facebook connect for DjangoApp","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a large dataset of events in a Postgres database that is too large to analyze in memory. Therefore I would like to quantize the datetimes to a regular interval and perform group by operations within the database prior to returning results. I thought I would use SqlSoup to iterate through the records in the appropriate table and make the necessary transformations. Unfortunately I can't figure out how to perform the iteration in such a way that I'm not loading references to every record into memory at once. Is there some way of getting one record reference at a time in order to access the data and update each record as needed?\nAny suggestions would be most appreciated!\nChris","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":333,"Q_Id":10359617,"Users Score":1,"Answer":"After talking with some folks, it's pretty clear the better answer is to use Pig to process and aggregate my data locally. At the scale, I'm operating it wasn't clear Hadoop was the appropriate tool to be reaching for. One person I talked to about this suggests Pig will be orders of magnitude faster than in-DB operations at the scale I'm operating at which is about 10^7 records.","Q_Score":0,"Tags":"python,postgresql,sqlsoup","A_Id":10360094,"CreationDate":"2012-04-28T00:57:00.000","Title":"Data Transformation in Postgres Using SqlSoup","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a python script that gets data from a USB weather station, now it puts the data into MySQL whenever the data is received from the station.\nI have a MySQL class with an insert function, what i want i that the function checks if it has been run the last 5 minutes if it has, quit.\nCould not find any code on the internet that does this.\nMaybe I need to have a sub-process, but I am not familiar with that at all.\nDoes anyone have an example that I can use?","AnswerCount":5,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":489,"Q_Id":10366424,"Users Score":0,"Answer":"Just derive to a new class and override the insert function. In the overwriting function, check last insert time and call father's insert method if it has been more than five minutes, and of course update the most recent insert time.","Q_Score":1,"Tags":"python,python-2.7","A_Id":10366467,"CreationDate":"2012-04-28T18:36:00.000","Title":"Python, function quit if it has been run the last 5 minutes","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a python script that gets data from a USB weather station, now it puts the data into MySQL whenever the data is received from the station.\nI have a MySQL class with an insert function, what i want i that the function checks if it has been run the last 5 minutes if it has, quit.\nCould not find any code on the internet that does this.\nMaybe I need to have a sub-process, but I am not familiar with that at all.\nDoes anyone have an example that I can use?","AnswerCount":5,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":489,"Q_Id":10366424,"Users Score":0,"Answer":"Each time the function is run save a file with the current time. When the function is run again check the time stored in the file and make sure it is old enough.","Q_Score":1,"Tags":"python,python-2.7","A_Id":10366452,"CreationDate":"2012-04-28T18:36:00.000","Title":"Python, function quit if it has been run the last 5 minutes","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm building a social app in django, the architecture of the site will be very similar to facebook\nThere will be posts, posts will have comments\nBoth posts and comments will have meta data like date, author, tags, votes\nI decided to go with nosql database because of the ease with which we can add new features.\nI finalized on mongodb as i can easily store a post and its comments in a single document. I'm having second thoughts now, would REDIS be better than mongo for this kind of app?\nUpdate:\nI have decided to go with mongodb, will use redis for user home page and home page if necessary.","AnswerCount":4,"Available Count":3,"Score":0.0996679946,"is_accepted":false,"ViewCount":1158,"Q_Id":10396315,"Users Score":2,"Answer":"There's a huge distinction to be made between Redis and MongoDB for your particular needs, in that Redis, unlike MongoDB, doesn't facilitate value queries.\nYou can use MongoDB to embed the comments within the post document, which means you get the post and the comments in a single query, yet you could also query for post documents based on tags, the author, etc.\nYou'll definitely want to go with MongoDB. Redis is great, but it's not a proper fit for what I'd believe you'll need from it.","Q_Score":0,"Tags":"python,django,database-design,mongodb,redis","A_Id":10396700,"CreationDate":"2012-05-01T10:16:00.000","Title":"mongo db or redis for a facebook like site?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm building a social app in django, the architecture of the site will be very similar to facebook\nThere will be posts, posts will have comments\nBoth posts and comments will have meta data like date, author, tags, votes\nI decided to go with nosql database because of the ease with which we can add new features.\nI finalized on mongodb as i can easily store a post and its comments in a single document. I'm having second thoughts now, would REDIS be better than mongo for this kind of app?\nUpdate:\nI have decided to go with mongodb, will use redis for user home page and home page if necessary.","AnswerCount":4,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":1158,"Q_Id":10396315,"Users Score":0,"Answer":"First, loosely couple your app and your persistence so that you can swap them out at a very granular level. For example, you want to be able to move one service from mongo to redis as your needs evolve. Be able to measure your services and appropriately respond to them individually.\nSecond, you are unlikely to find one persistence solution that fits every workflow in your application at scale. Don't be afraid to use more than one. Mongo is a good tool for a set of problems, as is Redis, just not necessarily the same problems.","Q_Score":0,"Tags":"python,django,database-design,mongodb,redis","A_Id":10403789,"CreationDate":"2012-05-01T10:16:00.000","Title":"mongo db or redis for a facebook like site?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm building a social app in django, the architecture of the site will be very similar to facebook\nThere will be posts, posts will have comments\nBoth posts and comments will have meta data like date, author, tags, votes\nI decided to go with nosql database because of the ease with which we can add new features.\nI finalized on mongodb as i can easily store a post and its comments in a single document. I'm having second thoughts now, would REDIS be better than mongo for this kind of app?\nUpdate:\nI have decided to go with mongodb, will use redis for user home page and home page if necessary.","AnswerCount":4,"Available Count":3,"Score":0.049958375,"is_accepted":false,"ViewCount":1158,"Q_Id":10396315,"Users Score":1,"Answer":"These things are subjective and can be looked at in different directions. But if you have already decided to go with a nosql solution and is trying to determine between mongodb and redis I think it is better to go with mongodb as I guess you should be able to save a big number of posts and also mongodb documents are better suited to represent posts. \nRedis can only save upto the max memory limit but is super fast. So if you need to index some kind of things you can save posts in mongodb and then keep the id's of posts in redis to access faster.","Q_Score":0,"Tags":"python,django,database-design,mongodb,redis","A_Id":10396466,"CreationDate":"2012-05-01T10:16:00.000","Title":"mongo db or redis for a facebook like site?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am facing an issue with setting a value of Excel Cell.\nI get data from a table cell in MS-Word Document(dcx) and print it on output console.\nProblem is that the data of the cell is just a word, \"Hour\", with no apparent other leading or trailing printable character like white-spaces. But when I print it using python's print() function, it shows some unexpected character, more like a small \"?\" in a rectangle.\nI don't know where does it come from.\nAnd when I write the same variable that holds the word, \"Hour\", to an Excel cell it shows a bold dot(.)  in the cell.\nWhat can be the problem?\nAny help is much appreciated.\nI Am Using Python 3.2 And PyWin32 3.2 On Win7.\nThanks.","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":3883,"Q_Id":10423593,"Users Score":3,"Answer":"Try using value.rstrip('\\r\\n') to remove any carriage returns (\\r) or newlines (\\n) at the end of your string value.","Q_Score":3,"Tags":"python,excel,ms-word,character","A_Id":10423918,"CreationDate":"2012-05-03T00:30:00.000","Title":"Unwanted character in Excel Cell In Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"Sometimes an application requires quite a few SQL queries before it can do anything useful. I was wondering if there is a way to send those as a batch to the database, to avoid the overhead of going back and forth between the client and the server?\nIf there is no standard way to do it, I'm using the python bindings of MySQL.\nPS: I know MySQL has an executemany() function, but that's only for the same query executed many times with different parameters, right?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":92,"Q_Id":10434523,"Users Score":0,"Answer":"This process works best on inserts\n\nMake all you SQL queries into Stored Procedures. These eventually will become child stored procedures\nCreate Master Store procedure to run all other Stored Procedures.\nModify master Stored procedure to accept values required by child Stored Procedures\nModify master Stored procedure to accept commands using \"if\" statements to know which\nchild stored procedures to run\n\nIf you need return data from Database use 1 stored procedure at the time.","Q_Score":0,"Tags":"mysql,sql,mysql-python","A_Id":10434644,"CreationDate":"2012-05-03T15:27:00.000","Title":"Grouping SQL queries","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Lets say I have 100 servers each running a daemon - lets call it server - that server is responsible for spawning a thread for each user of this particular service (lets say 1000 threads per server). Every N seconds each thread does something and gets information for that particular user (this request\/response model cannot be changed). The problem I a have is sometimes a thread hangs and stops doing something. I need some way to know that users data is stale, and needs to be refreshed.\nThe only idea I have is every 5N seconds have the thread update a MySQL record associated with that user (a last_scanned column in the users table), and another process that checks that table every 15N seconds, if the last_scanned column is not current, restart the thread.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":221,"Q_Id":10440277,"Users Score":1,"Answer":"The general way to handle this is to have the threads report their status back to the server daemon. If you haven't seen a status update within the last 5N seconds, then you kill the thread and start another.\nYou can keep track of the current active threads that you've spun up in a list, then just loop through them occasionally to determine state.\nYou of course should also fix the errors in your program that are causing threads to exit prematurely.\nPremature exits and killing a thread could also leave your program in an unexpected, non-atomic state. You should probably also have the server daemon run a cleanup process that makes sure any items in your queue, or whatever you're using to determine the workload, get reset after a certain period of inactivity.","Q_Score":1,"Tags":"python,distributed-computing","A_Id":10440880,"CreationDate":"2012-05-03T22:39:00.000","Title":"Distributed server model","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I have come across a requirement that needs to access a set of databases in a Mongodb server, using TurboGear framework. There I need to list down the Databases, and allow the user to select one and move on. As far as I looked, TurboGear does facilitate multiple databases to use, but those needs to be specify beforehand in the development.ini.\nIs there a way to just connect to the db server(or to a particular database first) and then get the list of databases and select one on the fly?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":305,"Q_Id":10495324,"Users Score":2,"Answer":"For SQLAlchemy you can achieve something like that using a smarter Session.\nJust subclass the sqlalchemy.orm.Session class and override the get_bind(self, mapper=None, clause=None) method.\nThat method is called each time the session has to decide which engine to use and is expected to return the engine itself. You can then store a list of engines wherever you prefer and return the correct one.\nWhen using Ming\/MongoDB the same can probably be achieved by subclassing the ming.Session in model\/session.py and overridding the ming.Session.db property to return the right database.","Q_Score":2,"Tags":"mongodb,python-3.x,turbogears2","A_Id":10650606,"CreationDate":"2012-05-08T08:42:00.000","Title":"How to change the database on the fly in python using TurboGear framework?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have one table with Time32 column and large number of rows. My problem is next. \nWhen my table reaches thousand million rows, I want start archiving every row older than specified value. For creating query I will use Time32 column which represents timestamp for collected data in row. So,using this query I want delete old rows in working table, and store in other table reserved for storing archive records. Is it possible? If yes, what is most efficient way? \nI know for whereAppend() method, but this method only copy records, not delete from actual table. Thaks for advice. Cheers!","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":1114,"Q_Id":10496821,"Users Score":1,"Answer":"The general way to archive records from one table of a given database to another one is to copy records into the target table, and then to delete the same records in the origin table.\nThat said, depending of your database engine and the capabilities of the language built on top of that, you can write atomic query commands that do an atomic 'copy then delete' for you, but it is dependent of your database engine capabilities.\nIn your case of old records archiving, a robust approach can be to copy the records you want to archive by chunks by copying blocks of n records (n sized to your amount of data you can temporary clone, it is a trade-off between temporary additional size and the overhead of a copy delete action), then deleting those n records, and so on until to archive all the records fulfilling your condition Time32 field older than a given timestamp threshold.","Q_Score":1,"Tags":"python,database,python-2.7,hdf5,pytables","A_Id":10497547,"CreationDate":"2012-05-08T10:26:00.000","Title":"Pytables - Delete rows from table by some criteria","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I looked at the sqlite.org docs, but I am new to this, so bear with me. (I have a tiny bit of experience with MySQL, and I think using it would be an overkill for what I am trying to do with my application.)\nFrom what I understand I can initially create an SQLite db file locally on my MAC and add entrees to it using a Firefox extension. I could then store any number of tables and images (as binary). Once my site that uses this db is live, I could upload the db file to any web hosting service to any directory. In my site I could have a form that collects data and sends a request to write that data to the db file. Then, I could have an iOS app that connects to the db and reads the data. Did I get this right?\nWould I be able to run a Python script that writes to SQLite? What questions should I ask a potential hosting service? (I want to leave MediaTemple, so I am looking around...)\nI don't want to be limited to a Windows server, I am assuming SQLite would run on Unix? Or, does it depend on a hosting service? Thanks!","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":143,"Q_Id":10517900,"Users Score":1,"Answer":"I could upload the db file to any web hosting service to any directory\n\nSupposing that the service has the libraries installed to handle sqlite, and that sqlite is installed.\n\nWould I be able to run a Python script that writes to SQLite\n\nYes, well, maybe. As of Python 2.5, Python includes sqlite support as part of it's standard library.\n\nWhat questions should I ask a potential hosting service\n\nUsually, in their technical specs they will list what databases\/libraries\/languages are supported. I have successfully ran Python sites w\/ sqlite databases on Dreamhost.\n\nSQLite would run on Unix\n\nMost *nix flavors have pre-packaged sqlite installation binaries. The hosting provider should be able to tell you this as well.","Q_Score":0,"Tags":"python,sqlite,web-hosting","A_Id":10518010,"CreationDate":"2012-05-09T14:13:00.000","Title":"Understanding SQLite conceptually","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm trying to install MYSQLdb on a windows client.  The goal is, from the Windows client, run a python script that connects to a MySQL server on a LINUX client.  Looking at the setup code (and based on the errors I am getting when I try to run setup.py for mysqldb, it appears that I have to have my own version of MySQL on the windows box.  Is there a way (perhaps another module) that will let me accomplish this?  I need to have people on multiple boxes run a script that will interact with a MySQL database on a central server.","AnswerCount":3,"Available Count":1,"Score":0.0665680765,"is_accepted":false,"ViewCount":1771,"Q_Id":10541085,"Users Score":1,"Answer":"You don't need the entire MySQL database server, only the MySQL client libraries.","Q_Score":0,"Tags":"python,mysql,windows","A_Id":10541253,"CreationDate":"2012-05-10T19:44:00.000","Title":"Install MYSQLdb python module without MYSQL local install","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I know that pyramid comes with a scaffold for sqlalchemy. But what if I'm using the pyramid_jqm scaffold. How would you integrate or use sqlalchemy then? When I create a model.py and import from sqlalchemy I get an error that he couldnt find the module.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":101,"Q_Id":10551042,"Users Score":2,"Answer":"You have to setup your project in the same way that the alchemy scaffold is constructed. Put \"sqlalchemy\" in your setup.py requires field and run \"python setup.py develop\" to install the dependency. This is all just python and unrelated to Pyramid.","Q_Score":0,"Tags":"python,sqlalchemy,pyramid","A_Id":10555714,"CreationDate":"2012-05-11T12:08:00.000","Title":"Using sqlalchemy in pyramid_jqm","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am absolute beginner using google app engine with python 2.7. I was successful with creating helloworld app, but then any changes I do to the original app doesn't show in localhost:8080. Is there a way to reset\/refresh the localhost. I tried to create new projects\/directories with different content but my localhost constantly shows the old \"Hello world!\" I get the following in the log window:\n\nWARNING  2012-05-13 20:54:25,536 rdbms_mysqldb.py:74] The rdbms API is not available because the MySQLdb library could not be loaded.\n  WARNING  2012-05-13 20:54:26,496 datastore_file_stub.py:518] Could not read datastore data from c:\\users\\tomek\\appdata\\local\\temp\\dev_appserver.datastore\n  WARNING  2012-05-13 20:54:26,555 dev_appserver.py:3401] Could not initialize images API; you are likely missing the Python \"PIL\" module. ImportError: No module named _imaging\n\nPlease help...","AnswerCount":3,"Available Count":3,"Score":0.1325487884,"is_accepted":false,"ViewCount":437,"Q_Id":10575184,"Users Score":2,"Answer":"Those warnings shouldn't prevent you from seeing new 'content,' they simply mean that you are missing some libraries necessary to run local versions of CloudSQL (MySQL) and the Images API.\nFirst to do is try to clear your browser cache. What changes did you make to your Hello World app?","Q_Score":0,"Tags":"python,google-app-engine","A_Id":10575238,"CreationDate":"2012-05-13T20:57:00.000","Title":"Localhost is not refreshing\/reseting","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I am absolute beginner using google app engine with python 2.7. I was successful with creating helloworld app, but then any changes I do to the original app doesn't show in localhost:8080. Is there a way to reset\/refresh the localhost. I tried to create new projects\/directories with different content but my localhost constantly shows the old \"Hello world!\" I get the following in the log window:\n\nWARNING  2012-05-13 20:54:25,536 rdbms_mysqldb.py:74] The rdbms API is not available because the MySQLdb library could not be loaded.\n  WARNING  2012-05-13 20:54:26,496 datastore_file_stub.py:518] Could not read datastore data from c:\\users\\tomek\\appdata\\local\\temp\\dev_appserver.datastore\n  WARNING  2012-05-13 20:54:26,555 dev_appserver.py:3401] Could not initialize images API; you are likely missing the Python \"PIL\" module. ImportError: No module named _imaging\n\nPlease help...","AnswerCount":3,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":437,"Q_Id":10575184,"Users Score":0,"Answer":"Press CTRL-F5 in your browser, while on the page. Forces a cache refresh.","Q_Score":0,"Tags":"python,google-app-engine","A_Id":10593822,"CreationDate":"2012-05-13T20:57:00.000","Title":"Localhost is not refreshing\/reseting","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I am absolute beginner using google app engine with python 2.7. I was successful with creating helloworld app, but then any changes I do to the original app doesn't show in localhost:8080. Is there a way to reset\/refresh the localhost. I tried to create new projects\/directories with different content but my localhost constantly shows the old \"Hello world!\" I get the following in the log window:\n\nWARNING  2012-05-13 20:54:25,536 rdbms_mysqldb.py:74] The rdbms API is not available because the MySQLdb library could not be loaded.\n  WARNING  2012-05-13 20:54:26,496 datastore_file_stub.py:518] Could not read datastore data from c:\\users\\tomek\\appdata\\local\\temp\\dev_appserver.datastore\n  WARNING  2012-05-13 20:54:26,555 dev_appserver.py:3401] Could not initialize images API; you are likely missing the Python \"PIL\" module. ImportError: No module named _imaging\n\nPlease help...","AnswerCount":3,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":437,"Q_Id":10575184,"Users Score":0,"Answer":"You can try opening up the DOM reader (Mac: alt+command+i, Windows: shift+control+i) the reload the page. It's weird, but it works for me.","Q_Score":0,"Tags":"python,google-app-engine","A_Id":41388817,"CreationDate":"2012-05-13T20:57:00.000","Title":"Localhost is not refreshing\/reseting","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I have found that ultramysql meets my requirement. But it has no document, and no windows binary package.\nI have a program heavy on internet downloads and mysql inserts. So I use gevent to solve the multi-download-tasks problem. After I downloaded the web pages, and parsed the web pages, I get to insert the data into mysql.\nIs monkey.patch_all() make mysql operations async?\nCan anyone show me a correct way to go.","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":1197,"Q_Id":10580835,"Users Score":1,"Answer":"Postgres may be better suited due to its asynchronous capabilities","Q_Score":4,"Tags":"python,mysql,gevent","A_Id":12335813,"CreationDate":"2012-05-14T09:41:00.000","Title":"How to use mysql in gevent based programs in python?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I have found that ultramysql meets my requirement. But it has no document, and no windows binary package.\nI have a program heavy on internet downloads and mysql inserts. So I use gevent to solve the multi-download-tasks problem. After I downloaded the web pages, and parsed the web pages, I get to insert the data into mysql.\nIs monkey.patch_all() make mysql operations async?\nCan anyone show me a correct way to go.","AnswerCount":2,"Available Count":2,"Score":0.0996679946,"is_accepted":false,"ViewCount":1197,"Q_Id":10580835,"Users Score":1,"Answer":"I think one solution is use pymysql. Since pymysql use python socket, after monkey patch, should be work with gevent.","Q_Score":4,"Tags":"python,mysql,gevent","A_Id":13006283,"CreationDate":"2012-05-14T09:41:00.000","Title":"How to use mysql in gevent based programs in python?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I'm currently developing an application which connects to a database using sqlalchemy. The idea consists of having several instances of the application running in different computers using the same database. I want to be able to see changes in the database in all instances of the application once they are commited. I'm currently using sqlalchemy event interface, however it's not working when I have several concurrent instances of the application. I change something in one of the instances, but there are no signals emitted in the other instances.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1036,"Q_Id":10601947,"Users Score":0,"Answer":"You said it, you are using SQLAlchemy's event interface, it is not the one of the RDBMS, and SQLAlchemy does not communicate with the other instances connected to that DB.\nSQLAlchemy's event system calls a function in your own process. It's up to you to make this function send a signal to the rest of them via the network (or however they are connected). As long as SQLAlchemy is concerned, it doesn't know about the other instances connected to your database.\nSo, you might want to start another server on the machine with the database running, and make all the other listening to it, and act accordingly.\nHope it helps.","Q_Score":2,"Tags":"python,concurrency,sqlalchemy","A_Id":10602194,"CreationDate":"2012-05-15T13:37:00.000","Title":"Concurrency in sqlalchemy","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a couchdb instance with database a and database b. They should contain identical sets of documents, except that the _rev property will be different, which, AIUI, means I can't use replication.\nHow do I verify that the two databases really do contain the same documents which are all otherwise 'equal'?\nI've tried using the python-based couchdb-dump tool with a lot of sed magic to get rid of the _rev and MD5 and ETag headers, but then it still seems that property order in the JSON structure is slightly random, which means I still can't compare the output easily with something like diff.\nIs there a better approach here? Have other people wanted to solve a similar problem?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":685,"Q_Id":10615980,"Users Score":1,"Answer":"If you want to make sure they're exactly the same, write a map job that emits the document path as the key, and the documents hash (generated any way you like) as the value. Do not include the _rev field in the hash generation.\nYou cannot reduce to a single hash because order is not guaranteed, but you can feed the resultant JSON document to a good diff program.","Q_Score":1,"Tags":"couchdb,replication,couchdb-python","A_Id":10616421,"CreationDate":"2012-05-16T09:45:00.000","Title":"Compare two couchdb databases","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have made a python ladon webservice and I run is on Ubuntu with Apache2 and mod_wsgi. (I use Python 2.6).\nThe webservice connect to a postgreSQL database with psycopg2 python module.\nMy problem is that the psycopg2.connection is closed (or destroyed) automatically after a little time (after about 1 or 2 minutes). \nThe other hand if I run the server with\nladon2.6ctl testserve\ncommand (http:\/\/ladonize.org\/index.php\/Python_Configuration)\nthan the server is working and the connection is not closed automatically.\nI can't understand why the connection is closed with apache+mod_wsgi and in this case the webserver is very slowly.\nCan anyone help me?","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":450,"Q_Id":10636409,"Users Score":1,"Answer":"If you are using mod_wsgi in embedded moe, especially with preform MPM for Apache, then likely that Apache is killing off the idle processes. Try using mod_wsgi daemon mode, which keeps process persistent and see if it makes a difference.","Q_Score":0,"Tags":"python,web-services,apache2,mod-wsgi,psycopg2","A_Id":10645670,"CreationDate":"2012-05-17T13:12:00.000","Title":"Python psycopg2 + mod_wsgi: connection is very slow and automatically close","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I wish to consume a .net webservice  containing the results of SQL Server query using a Python client. I have used the Python Suds library to interface to the same web service but not with a set of results. How should I structure the data so it is efficiently transmitted and consumed by a Python client. There should be a maximum of 40 rows of data, containing 60 bytes of data per row in 5 columns.","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":175,"Q_Id":10638071,"Users Score":1,"Answer":"Suds is a library to connect via SOAP, so you may already have blown \"efficiently transmitted\" out of the window, as this is a particularly verbose format over the wire. Your maximum data size is relatively small, and so should almost certainly be transmitted back in a single message so the SOAP overhead is incurred only once. So you should create a web service that returns a list or array of results, and call it once. This should be straightforwardly serialised to a single XML body that Suds then gives you access to.","Q_Score":0,"Tags":".net,python,sql-server,web-services,suds","A_Id":10653866,"CreationDate":"2012-05-17T14:49:00.000","Title":"SQL Query result via .net webservice to a non .net- Python client","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm seeing some unexpected behaviour with Flask-SQLAlchemy, and I don't understand what's going on:\nIf I make a change to a record using e.g. MySQL Workbench or Sequel Pro, the running app (whether running under WSGI on Apache, or from the command line) isn't picking up the change. If I reload the app by touching the WSGI file, or by reloading it (command line), I can see the changed record. I've verified this by running an all() query in the interactive shell, and it's the same \u2013 no change until I quit the shell, and start again. I get the feeling I'm missing something incredibly obvious here \u2013 it's a single table, no joins etc. \u2013 Running MySQL 5.5.19, and SQLA 0.7.7 on 2.7.3","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":326,"Q_Id":10645793,"Users Score":1,"Answer":"you app's SELECT is probably within its own transaction \/ session so changes submitted by another session (e.g. MySQL Workbench connection) are not yet visible for your SELECT. You can easily verify it by enabling mysql general log or by setting 'echo: false' in your create_engine(...) definition. Chances are you're starting your SQLAlchemy session in SET AUTOCOMMIT = 0 mode which requires explicit commit or rollback (when you restart \/ reload, Flask-SQLAlchemy does it for you automatically). Try either starting your session in autocommit=true mode or stick explicit commit\/rollback before calling your SELECT.","Q_Score":1,"Tags":"python,flask-sqlalchemy","A_Id":15194364,"CreationDate":"2012-05-18T01:57:00.000","Title":"Flask SQLAlchemy not picking up changed records","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Background:\nI'm trying to use a Google Map as an interface to mark out multiple polygons, that can be stored in a Postgres Database.\nThe Database will then be queried with a geocoded Longitude Latitude Point to determine which of the Drawn Polygons encompass the point.\nUsing Python and Django.\nQuestion\nHow do I configure the Google Map to allow a user to click around and specify multiple polygon areas?","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":667,"Q_Id":10647482,"Users Score":1,"Answer":"\"Using Python and Django\" only, you're not going to do this. Obviously you're going to need Javascript.\nSo you may as well dump Google Maps and use an open-source web mapping framework. OpenLayers has a well-defined Javascript API which will let you do exactly what you want. Examples in the OpenLayers docs show how.\nYou'll thank me later - specifically when Google come asking for a fee for their map tiles and you can't switch your Google Maps widget to OpenStreetMap or some other tile provider. This Actually Happens.","Q_Score":0,"Tags":"python,django,postgresql,google-maps,postgis","A_Id":10648479,"CreationDate":"2012-05-18T06:01:00.000","Title":"Mark Out Multiple Delivery Zones on Google Map and Store in Database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"There is a way to avoid duplicate files in mongo gridfs?\nOr I have to do that via application code (I am using pymongo)","AnswerCount":2,"Available Count":2,"Score":0.0996679946,"is_accepted":false,"ViewCount":2727,"Q_Id":10648729,"Users Score":1,"Answer":"You could use md5 hash and compare new hash with exists before saving file.","Q_Score":5,"Tags":"python,mongodb,gridfs","A_Id":10648760,"CreationDate":"2012-05-18T07:48:00.000","Title":"Mongo: avoid duplicate files in gridfs","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"There is a way to avoid duplicate files in mongo gridfs?\nOr I have to do that via application code (I am using pymongo)","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":2727,"Q_Id":10648729,"Users Score":5,"Answer":"The MD5 sum is already part of Mongo's gridfs meta-data, so you could simply set a unique index on that column and the server will refuse to store the file. No need to compare on the client side.","Q_Score":5,"Tags":"python,mongodb,gridfs","A_Id":10650262,"CreationDate":"2012-05-18T07:48:00.000","Title":"Mongo: avoid duplicate files in gridfs","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"Are there any good example projects which uses SQLAlchemy (with Python Classes) that I can look into? (which has at least some basic database operations - CRUD)\nI believe that, it is a good way to learn any programming language by looking into someone's code.\nThanks!","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":12180,"Q_Id":10656426,"Users Score":0,"Answer":"What kind of environment are you looking to work with on top of SQLAlchemy?\nMost likely, if you are using a popular web framework like django, Flask or Pylons, you can find many  examples and tutorials specific to that framework that include SQLAlchemy.\nThis will boost your knowledge both with SQLAlchemy and whatever else it is you are working with.\nChances are, you won't find any good project examples in 'just' SQLAlchemy as it essentially a tool.","Q_Score":18,"Tags":"python,sqlalchemy","A_Id":10778146,"CreationDate":"2012-05-18T16:32:00.000","Title":"SQLAlchemy Example Projects","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am confused about why python needs cursor object. I know jdbc and there the database connection is quite intuitive but in python I am confused with cursor object. Also I am doubtful about what is the difference between cursor.close() and connection.close() function in terms of resource release.","AnswerCount":3,"Available Count":1,"Score":0.3215127375,"is_accepted":false,"ViewCount":17423,"Q_Id":10660411,"Users Score":5,"Answer":"Connection object is your connection to the database, close that when you're done talking to the database all together.  Cursor object is an iterator over a result set from a query.  Close those when you're done with that result set.","Q_Score":41,"Tags":"python,python-db-api","A_Id":10660537,"CreationDate":"2012-05-18T22:16:00.000","Title":"difference between cursor and connection objects","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am thinking about creating an open source data management web application for various types of data. \nA privileged user must be able to \n\nadd new entity types (for example a 'user' or a 'family') \nadd new properties to entity types (for example 'gender' to 'user')\nremove\/modify entities and properties\n\nThese will be common tasks for the privileged user. He will do this through the web interface of the application. In the end, all data must be searchable and sortable by all types of users of the application. Two questions trouble me:\na) How should the data be stored in the database? Should I dynamically add\/remove database tables and\/or columns during runtime?\nI am no database expert. I am stuck with the imagination that in terms of relational databases, the application has to be able to dynamically add\/remove tables (entities) and\/or columns (properties) at runtime. And I don't like this idea. Likewise, I am thinking if such dynamic data should be handled in a NoSQL database.\nAnyway, I believe that this kind of problem has an intelligent canonical solution, which I just did not find and think of so far. What is the best approach for this kind of dynamic data management?\nb) How to implement this in Python using an ORM or NoSQL?\nIf you recommend using a relational database model, then I would like to use SQLAlchemy. However, I don't see how to dynamically create tables\/columns with an ORM at runtime. This is one of the reasons why I hope that there is a much better approach than creating tables and columns during runtime. Is the recommended database model efficiently implementable with SQLAlchemy?\nIf you recommend using a NoSQL database, which one? I like using Redis -- can you imagine an efficient implementation based on Redis?\nThanks for your suggestions!\nEdit in response to some comments:\nThe idea is that all instances (\"rows\") of a certain entity (\"table\") share the same set of properties\/attributes (\"columns\"). However, it will be perfectly valid if certain instances have an empty value for certain properties\/attributes.\nBasically, users will search the data through a simple form on a website. They query for e.g. all instances of an entity E with property P having a value V higher than T. The result can be sorted by the value of any property.\nThe datasets won't become too large. Hence, I think even the stupidest approach would still lead to a working system. However, I am an enthusiast and I'd like to apply modern and appropriate technology as well as I'd like to be aware of theoretical bottlenecks. I want to use this project in order to gather experience in designing a \"Pythonic\", state-of-the-art, scalable, and reliable web application.\nI see that the first comments tend to recommending a NoSQL approach. Although I really like Redis, it looks like it would be stupid not to take advantage of the Document\/Collection model of Mongo\/Couch. I've been looking into mongodb and mongoengine for Python. By doing so, do I take steps into the right direction?\nEdit 2 in response to some answers\/comments:\nFrom most of your answers, I conclude that the dynamic creation\/deletion of tables and columns in the relational picture is not the way to go. This already is valuable information. Also, one opinion is that the whole idea of the dynamic modification of entities and properties could be bad design.\nAs exactly this dynamic nature should be the main purpose\/feature of the application, I don't give up on this. From the theoretical point of view, I accept that performing operations on a dynamic data model must necessarily be slower than performing operations on a static data model. This is totally fine.\nExpressed in an abstract way, the application needs to manage\n\nthe data layout, i.e. a \"dynamic list\" of valid entity types and a \"dynamic list\" of properties for each valid entity type\nthe data itself\n\nI am looking for an intelligent and efficient way to implement this. From your answers, it looks like NoSQL is the way to go here, which is another important conclusion.","AnswerCount":4,"Available Count":2,"Score":1.0,"is_accepted":false,"ViewCount":4158,"Q_Id":10672939,"Users Score":6,"Answer":"What you're asking about is a common requirement in many systems -- how to extend a core data model to handle user-defined data.  That's a popular requirement for packaged software (where it is typically handled one way) and open-source software (where it is handled another way).\nThe earlier advice to learn more about RDBMS design generally can't hurt.  What I will add to that is, don't fall into the trap of re-implementing a relational database in your own application-specific data model!  I have seen this done many times, usually in packaged software.  Not wanting to expose the core data model (or permission to alter it) to end users, the developer creates a generic data structure and an app interface that allows the end user to define entities, fields etc. but not using the RDBMS facilities.  That's usually a mistake because it's hard to be nearly as thorough or bug-free as what a seasoned RDBMS can just do for you, and it can take a lot of time.  It's tempting but IMHO not a good idea.\nAssuming the data model changes are global (shared by all users once admin has made them), the way I would approach this problem would be to create an app interface to sit between the admin user and the RDBMS, and apply whatever rules you need to apply to the data model changes, but then pass the final changes to the RDBMS.  So for example, you may have rules that say entity names need to follow a certain format, new entities are allowed to have foreign keys to existing tables but must always use the DELETE CASCADE rule, fields can only be of certain data types, all fields must have default values etc.  You could have a very simple screen asking the user to provide entity name, field names & defaults etc. and then generate the SQL code (inclusive of all your rules) to make these changes to your database.\nSome common rules & how you would address them would be things like:\n-- if a field is not null and has a default value, and there are already existing records in the table before that field was added by the admin, update existing records to have the default value while creating the field (multiple steps -- add field allowing null; update all existing records; alter the table to enforce not null w\/ default) -- otherwise you wouldn't be able to use a field-level integrity rule)\n-- new tables must have a distinct naming pattern so you can continue to distinguish your core data model from the user-extended data model, i.e. core and user-defined have different RDBMS owners (dbo. vs. user.) or prefixes (none for core, __ for user-defined) or somesuch.\n-- it is OK to add fields to tables that are in the core data model (as long as they tolerate nulls or have a default), and it is OK for admin to delete fields that admin added to core data model tables, but admin cannot delete fields that were defined as part of the core data model.\nIn other words -- use the power of the RDBMS to define the tables and manage the data, but in order to ensure whatever conventions or rules you need will always be applied, do this by building an app-to-DB admin function, instead of giving the admin user direct DB access.\nIf you really wanted to do this via the DB layer only, you could probably achieve the same by creating a bunch of stored procedures and triggers that would implement the same logic (and who knows, maybe you would do that anyway for your app).  That's probably more of a question of how comfortable are your admin users working in the DB tier vs. via an intermediary app.\n\nSo to answer your questions directly:\n(1) Yes, add tables and columns at run time, but think about the rules you will need to have to ensure your app can work even once user-defined data is added, and choose a way to enforce those rules (via app or via DB \/ stored procs or whatever) when you process the table & field changes.\n(2) This issue isn't strongly affected by your choice of SQL vs. NoSQL engine.  In every case, you have a core data model and an extended data model.  If you can design your app to respond to a dynamic data model (e.g. add new fields to screens when fields are added to a DB table or whatever) then your app will respond nicely to changes in both the core and user-defined data model.  That's an interesting challenge but not much affected by choice of DB implementation style.\nGood luck!","Q_Score":20,"Tags":"python,database,dynamic,sqlalchemy,redis","A_Id":10792940,"CreationDate":"2012-05-20T11:16:00.000","Title":"Which database model should I use for dynamic modification of entities\/properties during runtime?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am thinking about creating an open source data management web application for various types of data. \nA privileged user must be able to \n\nadd new entity types (for example a 'user' or a 'family') \nadd new properties to entity types (for example 'gender' to 'user')\nremove\/modify entities and properties\n\nThese will be common tasks for the privileged user. He will do this through the web interface of the application. In the end, all data must be searchable and sortable by all types of users of the application. Two questions trouble me:\na) How should the data be stored in the database? Should I dynamically add\/remove database tables and\/or columns during runtime?\nI am no database expert. I am stuck with the imagination that in terms of relational databases, the application has to be able to dynamically add\/remove tables (entities) and\/or columns (properties) at runtime. And I don't like this idea. Likewise, I am thinking if such dynamic data should be handled in a NoSQL database.\nAnyway, I believe that this kind of problem has an intelligent canonical solution, which I just did not find and think of so far. What is the best approach for this kind of dynamic data management?\nb) How to implement this in Python using an ORM or NoSQL?\nIf you recommend using a relational database model, then I would like to use SQLAlchemy. However, I don't see how to dynamically create tables\/columns with an ORM at runtime. This is one of the reasons why I hope that there is a much better approach than creating tables and columns during runtime. Is the recommended database model efficiently implementable with SQLAlchemy?\nIf you recommend using a NoSQL database, which one? I like using Redis -- can you imagine an efficient implementation based on Redis?\nThanks for your suggestions!\nEdit in response to some comments:\nThe idea is that all instances (\"rows\") of a certain entity (\"table\") share the same set of properties\/attributes (\"columns\"). However, it will be perfectly valid if certain instances have an empty value for certain properties\/attributes.\nBasically, users will search the data through a simple form on a website. They query for e.g. all instances of an entity E with property P having a value V higher than T. The result can be sorted by the value of any property.\nThe datasets won't become too large. Hence, I think even the stupidest approach would still lead to a working system. However, I am an enthusiast and I'd like to apply modern and appropriate technology as well as I'd like to be aware of theoretical bottlenecks. I want to use this project in order to gather experience in designing a \"Pythonic\", state-of-the-art, scalable, and reliable web application.\nI see that the first comments tend to recommending a NoSQL approach. Although I really like Redis, it looks like it would be stupid not to take advantage of the Document\/Collection model of Mongo\/Couch. I've been looking into mongodb and mongoengine for Python. By doing so, do I take steps into the right direction?\nEdit 2 in response to some answers\/comments:\nFrom most of your answers, I conclude that the dynamic creation\/deletion of tables and columns in the relational picture is not the way to go. This already is valuable information. Also, one opinion is that the whole idea of the dynamic modification of entities and properties could be bad design.\nAs exactly this dynamic nature should be the main purpose\/feature of the application, I don't give up on this. From the theoretical point of view, I accept that performing operations on a dynamic data model must necessarily be slower than performing operations on a static data model. This is totally fine.\nExpressed in an abstract way, the application needs to manage\n\nthe data layout, i.e. a \"dynamic list\" of valid entity types and a \"dynamic list\" of properties for each valid entity type\nthe data itself\n\nI am looking for an intelligent and efficient way to implement this. From your answers, it looks like NoSQL is the way to go here, which is another important conclusion.","AnswerCount":4,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":4158,"Q_Id":10672939,"Users Score":3,"Answer":"So, if you conceptualize your entities as \"documents,\" then this whole problem maps onto a no-sql solution pretty well.  As commented, you'll need to have some kind of model layer that sits on top of your document store and performs tasks like validation, and perhaps enforces (or encourages) some kind of schema, because there's no implicit backend requirement that entities in the same collection (parallel to table) share schema.\nAllowing privileged users to change your schema concept (as opposed to just adding fields to individual documents - that's easy to support) will pose a little bit of a challenge - you'll have to handle migrating the existing data to match the new schema automatically.\nReading your edits, Mongo supports the kind of searching\/ordering you're looking for, and will give you the support for \"empty cells\" (documents lacking a particular key) that you need.\nIf I were you (and I happen to be working on a similar, but simpler, product at the moment), I'd stick with Mongo and look into a lightweight web framework like Flask to provide the front-end.  You'll be on your own to provide the model, but you won't be fighting against a framework's implicit modeling choices.","Q_Score":20,"Tags":"python,database,dynamic,sqlalchemy,redis","A_Id":10707420,"CreationDate":"2012-05-20T11:16:00.000","Title":"Which database model should I use for dynamic modification of entities\/properties during runtime?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a large SQLServer database on my current hosting site...\nand\nI would like to import it into Google BigData.\nIs there a method for this?","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":108,"Q_Id":10705572,"Users Score":1,"Answer":"I think that the answer is that there is no general recipe for doing this.  In fact, I don't even think it makes sense to have a general recipe ...\nWhat you need to do is to analyse the SQL schemas and work out an appropriate mapping to BigData schemas.  Then you figure out how to migrate the data.","Q_Score":0,"Tags":"python,sql-server,bigdata","A_Id":10713425,"CreationDate":"2012-05-22T15:52:00.000","Title":"Porting data from SQLServer to BigData","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I need to copy an existing neo4j database in Python. I even do not need it for backup, just to play around with while keeping the original database untouched. However, there is nothing about copy\/backup operations in neo4j.py documentation (I am using python embedded binding). \nCan I just copy the whole folder with the original neo4j database to a folder with a new name?\nOr is there any special method available in neo4j.py?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":310,"Q_Id":10724345,"Users Score":2,"Answer":"Yes,\nyou can copy the whole DB directory when you have cleanly shut down the DB for backup.","Q_Score":1,"Tags":"python,copy,backup,neo4j","A_Id":10736999,"CreationDate":"2012-05-23T16:44:00.000","Title":"Copy neo4j database from python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Let's say I get sales data every 15 minutes. The sales transactions are stored in a mysql database. I need to be able to graph this data, and allow the user to re-size the scale of time. The info would be graphed on a django website. \nHow would I go about doing this, and are there any open source tools that I could look into?","AnswerCount":3,"Available Count":1,"Score":0.0665680765,"is_accepted":false,"ViewCount":3292,"Q_Id":10779244,"Users Score":1,"Answer":"HighCharts have awesome features you can also build pivot charts using that one but they will charge you .You can look over Py Chart also","Q_Score":0,"Tags":"python,mysql,sql","A_Id":10779681,"CreationDate":"2012-05-28T04:10:00.000","Title":"How to graph mysql data in python?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"In google app engine, can I call \"get_or_insert\" from inside a transaction?\nThe reason I ask is because I'm not sure if there is some conflict with having this run its own transaction inside an already running transaction.\nThanks!","AnswerCount":2,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":308,"Q_Id":10790381,"Users Score":2,"Answer":"No. get_or_insert is syntactic sugar for a transactional function that fetches or inserts a record. You can implement it yourself trivially, but that will only work if the record you're operating on is in the same entity group as the rest of the entities in the current transaction, or if you have cross-group transactions enabled.","Q_Score":2,"Tags":"python,google-app-engine","A_Id":10791742,"CreationDate":"2012-05-28T21:01:00.000","Title":"In app engine, can I call \"get_or_insert\" from inside a transaction?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"In db.py,I can use a function(func insert) insert data into sqlite correctly.\nNow I want to insert data into sqlite through python-fastcgi, in\n    fastcgi (just named post.py ) I can get the request data correctly,but\n    when I call db.insert,it gives me internal server error. \n\nI already did chmod 777 slqite.db. Anyone know whats problem?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1289,"Q_Id":10793042,"Users Score":4,"Answer":"Ffinally I found the answer: \nthe sqlite3 library needs write permissions also on the directory that contains it, probably because it needs to create a lockfile.\nTherefor when I use sql to insert data there is no problem, but when I do it through web cgi,fastcgi etc\uff09to insert data there would be an error. \nJust add write permission to the directory.","Q_Score":2,"Tags":"python,sqlite,fastcgi","A_Id":10796243,"CreationDate":"2012-05-29T04:23:00.000","Title":"sqlite3 insert using python and python cgi","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have run a few trials and there seems to be some improvement in speed if I set autocommit to False.\nHowever, I am worried that doing one commit at the end of my code, the database rows will not be updated. So, for example, I do several updates to the database, none are committed, does querying the database then give me the old data? Or, does it know it should commit first?\nOr, am I completely mistaken as to what commit actually does?\nNote: I'm using pyodbc and MySQL. Also, the table I'm using are InnoDB, does that make a difference?","AnswerCount":3,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":1170,"Q_Id":10803012,"Users Score":0,"Answer":"As long as you use the same connection, the database should show you a consistent view on the data, e.g. with all changes made so far in this transaction.\nOnce you commit, the changes will be written to disk and be visible to other (new) transactions and connections.","Q_Score":2,"Tags":"python,mysql,odbc,pyodbc","A_Id":10803049,"CreationDate":"2012-05-29T16:22:00.000","Title":"Does setting autocommit to true take longer than batch committing?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have run a few trials and there seems to be some improvement in speed if I set autocommit to False.\nHowever, I am worried that doing one commit at the end of my code, the database rows will not be updated. So, for example, I do several updates to the database, none are committed, does querying the database then give me the old data? Or, does it know it should commit first?\nOr, am I completely mistaken as to what commit actually does?\nNote: I'm using pyodbc and MySQL. Also, the table I'm using are InnoDB, does that make a difference?","AnswerCount":3,"Available Count":2,"Score":0.0665680765,"is_accepted":false,"ViewCount":1170,"Q_Id":10803012,"Users Score":1,"Answer":"The default transaction mode for InnoDB is REPEATABLE READ, all the read will be consistent within a transaction. If you insert rows and query them in the same transaction, you will not see the newly inserted row, but they will be stored when you commit the transaction. If you want to see the newly inserted row before you commit the transaction, you can set the isolation level to READ COMMITTED.","Q_Score":2,"Tags":"python,mysql,odbc,pyodbc","A_Id":10803230,"CreationDate":"2012-05-29T16:22:00.000","Title":"Does setting autocommit to true take longer than batch committing?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"From someone who has a django application in a non-trivial production environment, how do you handle database migrations? I know there is south, but it seems like that would miss quite a lot if anything substantial is involved. \nThe other two options (that I can think of or have used) is doing the changes on a test database and then (going offline with the app) and importing that sql export. Or, perhaps a riskier option, doing the necessary changes on the production database in real-time, and if anything goes wrong reverting to the back-up.\nHow do you usually handle your database migrations and schema changes?","AnswerCount":6,"Available Count":2,"Score":0.0333209931,"is_accepted":false,"ViewCount":11397,"Q_Id":10826266,"Users Score":1,"Answer":"South isnt used everywhere. Like in my orgainzation we have 3 levels of code testing. One is local dev environment, one is staging dev enviroment, and third is that of a production . \nLocal Dev is on the developers hands where he can play according to his needs. Then comes staging dev which is kept identical to production, ofcourse, until a db change has to be done on the live site, where we do the db changes on staging first, and check if everything is working fine and then we manually change the production db making it identical to staging again.","Q_Score":22,"Tags":"python,mysql,django,migration,django-south","A_Id":10872504,"CreationDate":"2012-05-31T01:12:00.000","Title":"Database migrations on django production","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"From someone who has a django application in a non-trivial production environment, how do you handle database migrations? I know there is south, but it seems like that would miss quite a lot if anything substantial is involved. \nThe other two options (that I can think of or have used) is doing the changes on a test database and then (going offline with the app) and importing that sql export. Or, perhaps a riskier option, doing the necessary changes on the production database in real-time, and if anything goes wrong reverting to the back-up.\nHow do you usually handle your database migrations and schema changes?","AnswerCount":6,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":11397,"Q_Id":10826266,"Users Score":0,"Answer":"If its not trivial, you should have pre-prod database\/ app that mimic the production one. To avoid downtime on production.","Q_Score":22,"Tags":"python,mysql,django,migration,django-south","A_Id":70559647,"CreationDate":"2012-05-31T01:12:00.000","Title":"Database migrations on django production","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Using python(fastcgi),lighttpd,sqlite3 for server\nUpdate data of sqlite3 every weekend.\nThats means, every user get the same data from server before weekend,and server query database for every user's request.\nMy question is:\nIs there any way to cache data for users,server using cache data to response all users before updating data,not query database every time.\nLike using a global variable for a week,until update it.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":167,"Q_Id":10843191,"Users Score":1,"Answer":"You can use a cache such as memcached to store it once retrieved.","Q_Score":0,"Tags":"python,sqlite,fastcgi,lighttpd","A_Id":10843435,"CreationDate":"2012-06-01T01:04:00.000","Title":"cache data in python and sqlite3","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am trying to write a python program for appending live stock quotes from a csv file to an excel file (which is already open) using xlrd and xlwt.\nThe task is summarised below.\nFrom my stock-broker's application, a csv file is continually being updated on my hard disk.\nI wish to write a program which, when run, would append the new data from csv file to an excel file, which is kept open (I wonder whether it is possible to read & write an open file).\nI wish to keep the file open because I will be having stock-charts in it.\nIs it possible? If yes, how?","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":1299,"Q_Id":10851726,"Users Score":1,"Answer":"Not directly.  xlutils can use xlrd and xlwt to copy a spreadsheet, and appending to a \"to be written\" worksheet is straightforward.  I don't think reading the open spreadsheet is a problem -- but xlwt will not write to the open book\/sheet.\nYou might write an Excel VBA macro to draw the graphs.  In principle, I think a macro from a command workbook could close your stock workbook, invoke your python code to copy and update, open the new spreadsheet, and maybe run the macro to re-draw the graphs.\nAnother approach is to use matplotlib for the graphs.  I'd think a sleep loop could wake up every n seconds, grab the new csv data, append it to your \"big\" csv data, and re-draw the graph.  Taking this approach keeps you in python and should make things a lot easier, imho.  Disclosure: my Python is better than my VBA.","Q_Score":1,"Tags":"python,xlrd,xlwt","A_Id":10857757,"CreationDate":"2012-06-01T14:01:00.000","Title":"xlrd - append data to already opened workbook","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am trying to save an array of dates. I am providing a list of date objects, yet psycopg2 is throwing the above error.\nAny thoughts on how I can work around this?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1679,"Q_Id":10854532,"Users Score":1,"Answer":"This is a PostgreSQL error: you need an explicit cast. Add ::date[] after the value or the placeholder.","Q_Score":1,"Tags":"python,django,psycopg2","A_Id":10914900,"CreationDate":"2012-06-01T17:03:00.000","Title":"psycopg2 column is of type date[] but expression is of type text[]","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have an open source PHP website and I intend to modify\/translate (mostly constant strings) it so it can be used by Japanese users.\nThe original code is PHP+MySQL+Apache and written in English with charset=utf-8\nI want to change, for example, the word \"login\" into Japanese counterpart \"\u30ed\u30b0\u30a4\u30f3\" etc\nI am not sure whether I have to save the PHP code in utf-8 format (just like Python)?\nI only have experience with Python, so what other issues I should take care of?","AnswerCount":3,"Available Count":2,"Score":0.1325487884,"is_accepted":false,"ViewCount":148,"Q_Id":10868473,"Users Score":2,"Answer":"If it's in the file, then yes, you will need to save the file as UTF-8.\nIf it's is in the database, you do not need to save the PHP file as UTF-8.\nIn PHP, strings are basically just binary blobs.  You will need to save the file as UTF-8 so the correct bytes are read in.  In theory, if you saved the raw bytes in an ANSI file, it would still be output to the browser correctly, just your editor would not display it correctly, and you would run the risk of your editor manipulating it incorrectly.\nAlso, when handling non-ANSI strings, you'll need to be careful to use the multi-byte versions of string manipulation functions (str_replace will likely botch a utf-8 string for example).","Q_Score":2,"Tags":"php,python,mysql,apache,utf-8","A_Id":10868488,"CreationDate":"2012-06-03T06:52:00.000","Title":"PHP for Python Programmers: UTF-8 Issues","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have an open source PHP website and I intend to modify\/translate (mostly constant strings) it so it can be used by Japanese users.\nThe original code is PHP+MySQL+Apache and written in English with charset=utf-8\nI want to change, for example, the word \"login\" into Japanese counterpart \"\u30ed\u30b0\u30a4\u30f3\" etc\nI am not sure whether I have to save the PHP code in utf-8 format (just like Python)?\nI only have experience with Python, so what other issues I should take care of?","AnswerCount":3,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":148,"Q_Id":10868473,"Users Score":0,"Answer":"If the file contains UTF-8 characters then save it with UTF-8. Otherwise you can save it in any format. One thing you should be aware of is that the PHP interpreter does not support the UTF-8 byte order mark so make sure you save it without that.","Q_Score":2,"Tags":"php,python,mysql,apache,utf-8","A_Id":10868497,"CreationDate":"2012-06-03T06:52:00.000","Title":"PHP for Python Programmers: UTF-8 Issues","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"Using CGI scripts, I can run single Python files on my server and then use their output on my website. \nHowever, I have a more complicated program on my computer that I would like to run on the server. It involves several modules I have written myself, and the SQLITE3 module built in Python. The program involves reading from a .db file and then using that data. \nOnce I run my main Python executable from a browser, I get a \"500: Internal server error\" error.\nI just wanted to know whether I need to change something in the permission settings or something for Python files to be allowed to import other Python files, or to read from a .db file. \nI appreciate any guidance, and sorry if I'm unclear about anything I'm new to this site and coding in general.\nFOLLOW UP: So, as I understand, there isn't anything inherently wrong with importing Python files on a server?","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":88,"Q_Id":10900319,"Users Score":0,"Answer":"I suggest you look in the log of your server to find out what caused the 500 error.","Q_Score":0,"Tags":"python,sqlite,web","A_Id":10900387,"CreationDate":"2012-06-05T15:34:00.000","Title":"Importing Python files into each other on a web server","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"It looks like this is what e.g. MongoEngine does.  The goal is to have model files be able to access the db without having to explicitly pass around the context.","AnswerCount":1,"Available Count":1,"Score":0.3799489623,"is_accepted":false,"ViewCount":877,"Q_Id":10906477,"Users Score":2,"Answer":"Pyramid has nothing to do with it. The global needs to handle whatever mechanism the WSGI server is using to serve your application.\nFor instance, most servers use a separate thread per request, so your global variable needs to be threadsafe. gunicorn and gevent are served using greenlets, which is a different mechanic.\nA lot of engines\/orms support a threadlocal connection. This will allow you to access your connection as if it were a global variable, but it is a different variable in each thread. You just have to make sure to close the connection when the request is complete to avoid that connection spilling over into the next request in the same thread. This can be done easily using a Pyramid tween or several other patterns illustrated in the cookbook.","Q_Score":2,"Tags":"python,pyramid","A_Id":10907158,"CreationDate":"2012-06-05T23:41:00.000","Title":"In Pyramid, is it safe to have a python global variable that stores the db connection?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"is there a difference if i use \"\"\"..\"\"\" in the sql of cusror.execute. Even if there is any slight difference please tell","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":125,"Q_Id":10910246,"Users Score":0,"Answer":"No, other than the string can contain newlines.","Q_Score":1,"Tags":"python,sql,string,mysql-python","A_Id":10910268,"CreationDate":"2012-06-06T07:55:00.000","Title":"What is the use of \"\"\"...\"\"\" in python instead of \"...\" or '...', especially in MySQLdb cursor.execute","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Just started to use Mercurial. Wow, nice application. I moved my database file out of the code directory, but I was wondering about the .pyc files. I didn't include them on the initial commit. The documentation about the .hgignore file includes an example to exclude *.pyc, so I think I'm on the right track. \nI am wondering about what happens when I decide to roll back to an older fileset. Will I need to delete all the .pyc files then? I saw some questions on Stack Overflow about the issue, including one gentleman that found old .pyc files were being used. What is the standard way around this?","AnswerCount":4,"Available Count":2,"Score":0.2449186624,"is_accepted":false,"ViewCount":8119,"Q_Id":10920423,"Users Score":5,"Answer":"Usually you are safe, because *.pyc are regenerated if the corresponding *.py changes its content.\nIt is problematic if you delete a *.py file and you are still importing from it in another file. In this case you are importing from the *.pyc file if it is existing. But this will be a bug in your code and is not really related to your mercurial workflow. \nConclusion: Every famous Python library is ignoring their *.pyc files, just do it ;)","Q_Score":7,"Tags":"python,django,mercurial,pyc","A_Id":10920888,"CreationDate":"2012-06-06T18:58:00.000","Title":"What to do with pyc files when Django or python is used with Mercurial?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Just started to use Mercurial. Wow, nice application. I moved my database file out of the code directory, but I was wondering about the .pyc files. I didn't include them on the initial commit. The documentation about the .hgignore file includes an example to exclude *.pyc, so I think I'm on the right track. \nI am wondering about what happens when I decide to roll back to an older fileset. Will I need to delete all the .pyc files then? I saw some questions on Stack Overflow about the issue, including one gentleman that found old .pyc files were being used. What is the standard way around this?","AnswerCount":4,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":8119,"Q_Id":10920423,"Users Score":0,"Answer":"Sure if you have a .pyc file from an older version of the same module python will use that.  Many times I have wondered why my program wasn't reflecting the changes I made, and realized it was because I had old pyc files.\nIf this means that .pyc are not reflecting your current version then yes you will have to delete all .pyc files.\nIf you are on linux you can find . -name *.pyc -delete","Q_Score":7,"Tags":"python,django,mercurial,pyc","A_Id":10920511,"CreationDate":"2012-06-06T18:58:00.000","Title":"What to do with pyc files when Django or python is used with Mercurial?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a sqlite3 database that I created from Python (2.7) on a local machine, and am trying to copy it to a remote location. I ran \"sqlite3 posts.db .backup posts.db.bak\" to create a copy (I can use the original and this new copy just fine). But when I move the copied file to the remote location, suddenly every command gives me: sqlite3.OperationalError: database is locked. How do I safely move a sqlite3 database so that I can use it after the move?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":624,"Q_Id":10922394,"Users Score":0,"Answer":"You did a .backup on the source system, but you don't mention doing a .restore on the target system. Please clarify.\nYou don't mention what versions of the sqlite3 executable you have on the source and target systems.\nYou don't mention how you transferred the .bak file from the source to the target.\nWas the source db being accessed by another process when you did the .backup?\nHow big is the file? Have you considered zip\/copy\/unzip instead of backup\/copy\/restore?","Q_Score":0,"Tags":"python,sqlite,copy","A_Id":10922927,"CreationDate":"2012-06-06T21:13:00.000","Title":"How to safely move an SQLite3 database?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a desktop application that send POST requests to a server where a django app store the results. DB server and web server are not on the same machine and it happens that sometimes the connectivity is lost for a very short time but results in a connection error on some requests:\n\nOperationalError: (2003, \"Can't connect to MySQL server on 'xxx.xxx.xxx.xxx' (110)\")\n\nOn a \"normal\" website I guess you'd not worry too much: the browser display a 500 error page and the visitor tries again later. \nIn my case loosing info posted by a request is not an option and I am wondering how to handle this? I'd try to catch on this exception, wait for the connectivity to come back (lag is not a problem) and then continue the process. But as the exception can occur about anywhere in the code I'm a bit stuck on how to proceed.\nThanks for your advice.","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":2536,"Q_Id":10930459,"Users Score":1,"Answer":"You could use a middleware with a process_view method and a try \/ except wrapping your call. \nOr you could decorate your views and wrap the call there.\nOr you could use class based views with a base class that has a method decorator on its dispatch method, or an overriden.dispatch.\nReally, you have plenty of solutions.\nNow, as said above, you might want to modify your Desktop application too!","Q_Score":1,"Tags":"python,mysql,django","A_Id":10935789,"CreationDate":"2012-06-07T11:00:00.000","Title":"Django: how to properly handle a database connection error","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I cant find \"best\" solution for very simple problem(or not very)\nHave classical set of data: posts that attached to users, comments that attached to post and to user.\nNow i can't decide how to build scheme\/classes\nOn way is to store user_id inside comments and inside.\nBut what happens when i have 200 comments on page?\nOr when i have N posts on page?\nI mean it should be 200 additional requests to database to display user info(such as name,avatar)\nAnother solution is to embed user data into each comment and each post.\nBut first -> it is huge overhead, second -> model system is getting corrupted(using mongoalchemy), third-> user can change his info(like avatar). And what then? As i understand update operation on huge collections of comments or posts is not simple operation...\nWhat would you suggest? Is 200 requests per page to mongodb is OK(must aim for performance)?\nOr may be I am just missing something...","AnswerCount":4,"Available Count":1,"Score":0.049958375,"is_accepted":false,"ViewCount":919,"Q_Id":10931889,"Users Score":1,"Answer":"What I would do with mongodb would be to embed the user id into the comments (which are part of the structure of the \"post\" document).\nThree simple hints for better performances:\n1) Make sure to ensure an index on the user_id\n2) Use comment pagination method to avoid querying 200 times the database\n3) Caching is your friend","Q_Score":3,"Tags":"python,mongodb,mongoalchemy,nosql","A_Id":10932004,"CreationDate":"2012-06-07T12:34:00.000","Title":"MongoDB: Embedded users into comments","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am making a little add-on for a game, and it needs to store information on a player:\n\nusername\nip-address\nlocation in game\na list of alternate user names that have came from that ip or alternate ip addresses that come from that user name\n\nI read an article a while ago that said that unless I am storing a large amount of information that can not be held in ram, that I should not use a database.  So I tried using the shelve module in python, but I'm not sure if that is a good idea.\nWhen do you guys think it is a good idea to use a database, and when it better to store information in another way , also what are some other ways to store information besides databases and flat file databases.","AnswerCount":2,"Available Count":1,"Score":1.0,"is_accepted":false,"ViewCount":5782,"Q_Id":10957877,"Users Score":7,"Answer":"Assuming by 'database' you mean 'relational database' - even the embedded databases like SQLite come with some overhead compared to a plain text file. But, sometimes that overhead is worth it compared to rolling your own. \nThe biggest question you need to ask is whether you are storing relational data - whether things like normalisation and SQL queries make any sense at all. If you need to lookup data across multiple tables using joins, you should certainly use a relational database - that's what they're for. On the other hand, if all you need to do is lookup into one table based on its primary key, you probably want a CSV file. Pickle and shelve are useful if what you're persisting is the objects you use in your program - if you can just add the relevant magic methods to your existing classes and expect it all to make sense.\nCertainly \"you shouldn't use databases unless you have a lot of data\" isn't the best advice - the amount of data goes more to what database you might use if you are using one. SQLite, for example, wouldn't be suitable for something the size of Stackoverflow - but, MySQL or Postgres would almost certainly be overkill for something with five users.","Q_Score":14,"Tags":"python,database,flat-file","A_Id":10957953,"CreationDate":"2012-06-09T02:16:00.000","Title":"When is it appropriate to use a database , in Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am looking around in order to get an answer what is the max limit of results I can have from a GQL query on Ndb on Google AppEngine. I am using an implementation with cursors but it will be much faster if I retrieve them all at once.","AnswerCount":2,"Available Count":2,"Score":1.0,"is_accepted":false,"ViewCount":1106,"Q_Id":10968439,"Users Score":9,"Answer":"This depends on lots of things like the size of the entities and the number of values that need to look up in the index, so it's best to benchmark it for your specific application.  Also beware that if you find that on a sunny day it takes e.g. 10 seconds to load all your items, that probably means that some small fraction of your queries will run into a timeout due to natural variations in datastore performance, and occasionally your app will hit the timeout all the time when the datastore is having a bad day (it happens).","Q_Score":5,"Tags":"python,google-app-engine,gql,app-engine-ndb","A_Id":10974037,"CreationDate":"2012-06-10T11:51:00.000","Title":"What is the Google Appengine Ndb GQL query max limit?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I am looking around in order to get an answer what is the max limit of results I can have from a GQL query on Ndb on Google AppEngine. I am using an implementation with cursors but it will be much faster if I retrieve them all at once.","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":1106,"Q_Id":10968439,"Users Score":7,"Answer":"Basically you don't have the old limit of 1000 entities per query anymore, but consider using a reasonable limit, because you can hit the time out error and it's better to get them in batches so users won't wait during load time.","Q_Score":5,"Tags":"python,google-app-engine,gql,app-engine-ndb","A_Id":10969575,"CreationDate":"2012-06-10T11:51:00.000","Title":"What is the Google Appengine Ndb GQL query max limit?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"When I say 'equivalent', I mean an ORM that allows for the same work-style. That is;\n\nSetting up a database\nDispensing and editing 'beans' (table rows) as if the table was already ready, while the table is being created behind the scenes\nReviewing, indexing and polishing the table structure before production\n\nThanks for any leads","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":700,"Q_Id":10987162,"Users Score":0,"Answer":"Short answer, there is a proof-of-concept called PyBean as answered by Gabor de Mooij, but it barely offers any features and cannot be used. There are no other Python libraries that work like PyBean.","Q_Score":1,"Tags":"php,python,mysql,orm,redbean","A_Id":13714374,"CreationDate":"2012-06-11T20:35:00.000","Title":"Is there a RedBeanPHP equivalent for Python?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Here's the scenario:\nI have a url in a MySQL database that contains Unicode. The database uses the Latin-1 encoding. Now, when I read the record from MySQL using Python, it gets converted to Unicode because all strings follow the Unicode format in Python.\nI want to write the URL into a text file -- to do so, it needs to be converted to bytes (UTF-8). This was done successfully.\nNow, given the URLS that are in the text file, I want to query the db for these SAME urls in the database. I do so by calling the source command to execute a few select queries.\nResult: I get no matches.\nI suspect that the problem stems from my conversion to UTF-8, which somehow is messing up the symbols.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1752,"Q_Id":10990496,"Users Score":0,"Answer":"You most probably need to set your mysql shell client to use utf8.\nYou can set it either in mysql shell directly by running set character set utf8.\nOr by adding default-character-set=utf8 to your ~\/.my.cnf.","Q_Score":0,"Tags":"python,mysql,unicode,encoding,utf-8","A_Id":10992555,"CreationDate":"2012-06-12T04:22:00.000","Title":"Unicode to UTF-8 encoding issue when importing SQL text file into MySQL","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm looking for a way of editing and save a specified cell in Excel 2010 .xlsx file from Node.JS. I realize, that maybe there are no production-ready solutions for NodeJS at this time. However, NodeJS supports C++ libraries, so could you suggest me any suitable lib compatible with Node?\nAlso, I had an idea to process this task via Python (xlrd, xlwt) and call it with NodeJS. What do you think of this? Are there any more efficient methods to edit XLSX from NodeJS? Thanks.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":3505,"Q_Id":11007460,"Users Score":0,"Answer":"Basically you have 2 possibilities:\n\nnode.js does not support C++ libraries but it is possible to write bindings for node.js that interact with a C\/C++ library. So you need to get your feet wet on writing a C++ addon for the V8 (the JavaScript engine behind node.js)\nfind a command line program which does what you want to do. (It does not need to be Python.) You could call this from your JavaScript code by using a child-process.\n\nFirst option is more work, but would be result in faster executing time (when done right). Second possibility is easier to realise.\nP.S.: To many question for one question. I've no idea about the xls-whatever stuff, besides it's \"actually\" only XML.","Q_Score":0,"Tags":"c++,python,excel,node.js,read-write","A_Id":11008175,"CreationDate":"2012-06-13T02:27:00.000","Title":"Node.JS\/C++\/Python - edit Excel .xlsx file","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Okay., We have Rails webapp which stores data in a mysql data base. The table design was not read efficient. So we resorted to creating a separate set of read only tables in mysql and made all our internal API calls use that tables for read. We used callbacks to keep the data in sync between both the set of tables. Now we have a another Python app which is going to mess with the same database - now how do we proceed maintaining the data integrity? \nActive record callbacks can't be used anymore. We know we can do it with triggers. But is there a any other elegant way to do this? How to people achieve to maintain the integrity of such derived data.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":296,"Q_Id":11013976,"Users Score":1,"Answer":"Yes, refactor the code to put a data web service in front of the database and let the Ruby and Python apps talk to the service.  Let it maintain all integrity and business rules.  \n\"Don't Repeat Yourself\" - it's a good rule.","Q_Score":2,"Tags":"python,mysql,ruby-on-rails,database,triggers","A_Id":11014025,"CreationDate":"2012-06-13T11:31:00.000","Title":"Maintaining data integrity in mysql when different applications are accessing it","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have an excel spreadsheet (version 1997-2003) and another nonspecific database file (a .csy file, I am assuming it can be parsed as a text file as that is what it appears to be). I need to take information from both sheets, match them up, put them on one line, and print it to a text file. I was going to use python for this as usuing the python plugins for Visual Studio 2010 alongside the xlrd package seems to be the best way I could find for excel files, and I'd just use default packages in python for the other file. \nWould python be a good choice of language to both learn and program this script in? I am not familiar with scripting languages other then a little bit of VBS, so any language will be a learning experience for me. \nConverting the xls to csv is not an option, there are too many excel files, and the wonky formatting of them would make fishing through the csv more difficult then using xlrd.","AnswerCount":3,"Available Count":1,"Score":-0.0665680765,"is_accepted":false,"ViewCount":2962,"Q_Id":11020919,"Users Score":-1,"Answer":"Python is beginner-friendly and is good with string manipulation so it's a good choice.  I have no idea how easy awk is to learn without programming experience but I would consider that as it's more or less optimized for processing csv's.","Q_Score":1,"Tags":"python,excel,file-io,scripting","A_Id":11020968,"CreationDate":"2012-06-13T18:16:00.000","Title":"First time writing a script, not sure what language to use (parsing excel and other files)","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"We are writing an inventory system and I have some questions about sqlalchemy (postgresql) and transactions\/sessions. This is a web app using TG2, not sure this matters but to much info is never a bad. \n\nHow can make sure that when changing inventory qty's that i don't run into race conditions. If i understand it correctly if user on is going to decrement inventory on an item to say 0 and user two is also trying to decrement the inventory to 0 then if user 1s session hasn't been committed yet then user two starting inventory number is going to be the same as user one resulting in a race condition when both commit, one overwriting the other instead of having a compound effect.\nIf i wanted to use postgresql sequence for things like order\/invoice numbers how can I get\/set next values from sqlalchemy without running into race conditions?\n\nEDIT: I think i found the solution i need to use with_lockmode, using for update or for share. I am going to leave open for more answers or for others to correct me if I am mistaken.\nTIA","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":2935,"Q_Id":11033892,"Users Score":3,"Answer":"If two transactions try to set the same value at the same time one of them will fail.  The one that loses will need error handling. For your particular example you will want to query for the number of parts and update the number of parts in the same transaction.\nThere is no race condition on sequence numbers. Save a record that uses a sequence number the DB will automatically assign it.\nEdit:\nNote as Limscoder points out you need to set the isolation level to Repeatable Read.","Q_Score":2,"Tags":"python,postgresql,web-applications,sqlalchemy,turbogears2","A_Id":11034199,"CreationDate":"2012-06-14T13:15:00.000","Title":"SQLAlchemy(Postgresql) - Race Conditions","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am using mongoexport to export mongodb data which also has Image data in Binary format.\nExport is done in csv format.\nI tried to read image data from csv file into python and tried to store as in Image File in .jpg format on disk.\nBut it seems that, data is corrupt and image is not getting stored.\nHas anybody come across such situation or resolved similar thing ?\nThanks,","AnswerCount":2,"Available Count":2,"Score":-0.0996679946,"is_accepted":false,"ViewCount":930,"Q_Id":11055921,"Users Score":-1,"Answer":"Depending how you stored the data, it may be prefixed with 4 bytes of size.  Are the corrupt exports 4 bytes\/GridFS chunk longer than you'd expect?","Q_Score":1,"Tags":"python,image,mongodb,csv","A_Id":11058611,"CreationDate":"2012-06-15T18:01:00.000","Title":"Can mongoexport be used to export images stored in binary format in mongodb","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am using mongoexport to export mongodb data which also has Image data in Binary format.\nExport is done in csv format.\nI tried to read image data from csv file into python and tried to store as in Image File in .jpg format on disk.\nBut it seems that, data is corrupt and image is not getting stored.\nHas anybody come across such situation or resolved similar thing ?\nThanks,","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":930,"Q_Id":11055921,"Users Score":0,"Answer":"One thing to watch out for is an arbitrary 2MB BSON Object size limit in several of 10gen's implementations. You might have to denormalize your image data and store it across multiple objects.","Q_Score":1,"Tags":"python,image,mongodb,csv","A_Id":11056533,"CreationDate":"2012-06-15T18:01:00.000","Title":"Can mongoexport be used to export images stored in binary format in mongodb","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I need to manipulate a large amount of numerical\/textual data, say total of 10 billion entries which  can be theoretically organized as 1000 of 10000*1000 tables.\nMost calculations need to be performed on a small subset of data each time (specific rows or columns), such that I don't need all the data at once.\nTherefore, I am intersted to store the data in some kind of database so I can easily search the database, retrieve multiple rows\/columns matching defined criteria, make some calculations and update the database.The database should be accessible with both Python and Matlab, where I use Python mainly for creating raw data and putting it into database and Matlab for the data processing. \nThe whole project runs on Windows 7. What is the best and mainly the simplest database I can use for this purpose? I have no prior experience with databases at all.","AnswerCount":3,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":3289,"Q_Id":11058409,"Users Score":3,"Answer":"IMO simply use the file system with a file format that can you read\/write in both MATLAB and Python. Databases usually imply a relational model (excluding the No-SQL ones), which would only add complexity here.\nBeing more MATLAB-inclined, you can directly manipulate MAT-files in SciPy with scipy.io.loadmat\/scipy.io.savemat functions. This is the native MATLAB format for storing data, with save\/load functions.\nUnless of course you really need databases, then ignore my answer :)","Q_Score":4,"Tags":"python,database,matlab","A_Id":11058566,"CreationDate":"2012-06-15T21:27:00.000","Title":"What the simplest database to use with both Python and Matlab?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm looking for a search engine that I can point to a column in my database that supports advanced functions like spelling correction and \"close to\" results.   \nRight now I'm just using \nSELECT <column> from <table> where <colname> LIKE %<searchterm>% \nand I'm missing some results particularly when users misspell items.\nI've written some code to fix misspellings by running it through a spellchecker but thought there may be a better out-of-the box option to use.  Google turns up lots of options for indexing and searching the entire site where I really just need to index and search this one table column.","AnswerCount":3,"Available Count":2,"Score":0.1973753202,"is_accepted":false,"ViewCount":153,"Q_Id":11082229,"Users Score":3,"Answer":"Apache Solr is a great Search Engine that provides (1) N-Gram Indexing (search for not just complete strings but also for partial substrings, this helps greatly in getting similar results) (2) Provides an out of box Spell Corrector based on distance metric\/edit distance (which will help you in getting a \"did you mean chicago\" when the user types in chicaog) (3) It provides you with a Fuzzy Search option out of box (Fuzzy Searches helps you in getting close matches for your query, for an example if a user types in GA-123 he would obtain VMDEO-123 as a result) (4) Solr also provides you with \"More Like This\" component which would help you out like the above options.\nSolr (based on Lucene Search Library) is open source and is slowly rising to become the de-facto in the Search (Vertical) Industry and is excellent for database searches (As you spoke about indexing a database column, which is a cakewalk for Solr). Lucene and Solr are used by many Fortune 500 companies as well as Internet Giants.\nSphinx Search Engine is also great (I love it too as it has very low foot print for everything & is C++ based) but to put it simply Solr is much more popular.\nNow Python support and API's are available for both. However Sphinx is an exe and Solr is an HTTP. So for Solr you simply have to call the Solr URL from your python program which would return results that you can send to your front end for rendering, as simple as that)\nSo far so good. Coming to your question:\nFirst you should ask yourself that whether do you really require a Search Engine? Search Engines are good for all use cases mentioned above but are really made for searching across huge amounts of full text data or million's of rows of tabular data. The Algorithms like Did you Mean, Similar Records, Spell Correctors etc. can be written on top. Before zero-ing on Solr please also search Google for (1) Peter Norvig Spell Corrector & (2) N-Gram Indexing. Possibility is that just by writing few lines of code you may get really the stuff that you were looking out for.\nI leave it up to you to decide :)","Q_Score":3,"Tags":"python,mysql,database,search","A_Id":11088110,"CreationDate":"2012-06-18T11:52:00.000","Title":"Search Engine for a single DB column","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm looking for a search engine that I can point to a column in my database that supports advanced functions like spelling correction and \"close to\" results.   \nRight now I'm just using \nSELECT <column> from <table> where <colname> LIKE %<searchterm>% \nand I'm missing some results particularly when users misspell items.\nI've written some code to fix misspellings by running it through a spellchecker but thought there may be a better out-of-the box option to use.  Google turns up lots of options for indexing and searching the entire site where I really just need to index and search this one table column.","AnswerCount":3,"Available Count":2,"Score":0.0665680765,"is_accepted":false,"ViewCount":153,"Q_Id":11082229,"Users Score":1,"Answer":"I would suggest looking into open source technologies like Sphynx Search.","Q_Score":3,"Tags":"python,mysql,database,search","A_Id":11087295,"CreationDate":"2012-06-18T11:52:00.000","Title":"Search Engine for a single DB column","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a table in a django app where one of the fields is called Order (as in sort order) and is an integer. Every time a new record is entered the field auto increments itself to the next number. My issue is when a record is deleted I would like the other records to shift a number up and cant find anything that would recalculate all the records in the table and shift them a number up if a record is deleted. \nFor instance there are 5 records in the table where order numbers are 1, 2, 3, 4, and 5. Someone deleted record number 2 and now I would like numbers 3, 4, and 5 to move up to take the deleted number 2's place so the order numbers would now be 1, 2, 3, and 4. Is it possible with python, postgres and django?\nThanks in Advance!","AnswerCount":7,"Available Count":4,"Score":0.0,"is_accepted":false,"ViewCount":2701,"Q_Id":11100997,"Users Score":0,"Answer":"Instead of deleting orders - you should create a field which is a boolean (call it whatever you like - for example, deleted) and set this field to 1 for \"deleted\" orders.\nMessing with a serial field (which is what your auto-increment field is called in postgres) will lead to problems later; especially if you have foreign keys and relationships with tables.\nNot only will it impact your database server's performance; it also will impact on your business as eventually you will have two orders floating around that have the same order number; even though you have \"deleted\" one from the database, the order number may already be referenced somewhere else - like in a receipt your printed for your customer.","Q_Score":1,"Tags":"python,django,postgresql","A_Id":11101114,"CreationDate":"2012-06-19T12:32:00.000","Title":"Auto Increment Field in Django\/Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a table in a django app where one of the fields is called Order (as in sort order) and is an integer. Every time a new record is entered the field auto increments itself to the next number. My issue is when a record is deleted I would like the other records to shift a number up and cant find anything that would recalculate all the records in the table and shift them a number up if a record is deleted. \nFor instance there are 5 records in the table where order numbers are 1, 2, 3, 4, and 5. Someone deleted record number 2 and now I would like numbers 3, 4, and 5 to move up to take the deleted number 2's place so the order numbers would now be 1, 2, 3, and 4. Is it possible with python, postgres and django?\nThanks in Advance!","AnswerCount":7,"Available Count":4,"Score":0.1137907297,"is_accepted":false,"ViewCount":2701,"Q_Id":11100997,"Users Score":4,"Answer":"You are going to have to implement that feature yourself, I doubt very much that a relational db will do that for you, and for good reason: it means updating a potentially large number of rows when one row is deleted.\nAre you sure you need this?  It could become expensive.","Q_Score":1,"Tags":"python,django,postgresql","A_Id":11101064,"CreationDate":"2012-06-19T12:32:00.000","Title":"Auto Increment Field in Django\/Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a table in a django app where one of the fields is called Order (as in sort order) and is an integer. Every time a new record is entered the field auto increments itself to the next number. My issue is when a record is deleted I would like the other records to shift a number up and cant find anything that would recalculate all the records in the table and shift them a number up if a record is deleted. \nFor instance there are 5 records in the table where order numbers are 1, 2, 3, 4, and 5. Someone deleted record number 2 and now I would like numbers 3, 4, and 5 to move up to take the deleted number 2's place so the order numbers would now be 1, 2, 3, and 4. Is it possible with python, postgres and django?\nThanks in Advance!","AnswerCount":7,"Available Count":4,"Score":-0.0285636566,"is_accepted":false,"ViewCount":2701,"Q_Id":11100997,"Users Score":-1,"Answer":"Try to set the value with type sequence in postgres using pgadmin.","Q_Score":1,"Tags":"python,django,postgresql","A_Id":11101032,"CreationDate":"2012-06-19T12:32:00.000","Title":"Auto Increment Field in Django\/Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a table in a django app where one of the fields is called Order (as in sort order) and is an integer. Every time a new record is entered the field auto increments itself to the next number. My issue is when a record is deleted I would like the other records to shift a number up and cant find anything that would recalculate all the records in the table and shift them a number up if a record is deleted. \nFor instance there are 5 records in the table where order numbers are 1, 2, 3, 4, and 5. Someone deleted record number 2 and now I would like numbers 3, 4, and 5 to move up to take the deleted number 2's place so the order numbers would now be 1, 2, 3, and 4. Is it possible with python, postgres and django?\nThanks in Advance!","AnswerCount":7,"Available Count":4,"Score":0.0,"is_accepted":false,"ViewCount":2701,"Q_Id":11100997,"Users Score":0,"Answer":"I came across this looking for something else and wanted to point something out:\nBy storing the order in a field in the same table as your data, you lose data integrity, or if you index it things will get very complicated if you hit a conflict.  In other words, it's very easy to have a bug (or something else) give you two 3's, a missing 4, and other weird things can happen.  I inherited a project with a manual sort order that was critical to the application (there were other issues as well) and this was constantly an issue, with just 200-300 items.\nThe right way to handle a manual sort order is to have a separate table to manage it and sort with a join.  This way your Order table will have exactly 10 entries with just it's PK (the order number) and a foreign key relationship to the ID of the items you want to sort.  Deleted items just won't have a reference anymore.\nYou can continue to sort on delete similar to how you're doing it now, you'll just be updating the Order model's FK to list instead of iterating through and re-writing all your items.  Much more efficient.\nThis will scale up to millions of manually sorted items easily.  But rather than using auto-incremented ints, you would want to give each item a random order id in between the two items you want to place it between and keep plenty of space (few hundred thousand should do it) so you can arbitrarily re-sort them.\nI see you mentioned that you've only got 10 rows here, but designing your architecture to scale well the first time, as a practice, will save you headaches down the road, and once you're in the habit of it, it won't really take you any more time.","Q_Score":1,"Tags":"python,django,postgresql","A_Id":15074698,"CreationDate":"2012-06-19T12:32:00.000","Title":"Auto Increment Field in Django\/Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am new with SQL\/Python.\nI was wondering if there is a way for me to sort or categorize expense items into three primary categories.\nThat is I have a 56,000 row list with about 100+ different expense categories. They vary from things like Payroll, Credit Card Pmt, telephone, etc.\nI would like to put them into three categories, for the sake of analysis.\nI know I could do a GIANT IF statement in Excel, but that would be really time consuming, based on the fact that there are 100+ sub categories.\nIs there any way to expedite the process with Python or even in Excel?\nAlso, I don't know if this is material or not, but I am preparing this file to be uploaded to a SQL database.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":163,"Q_Id":11121395,"Users Score":0,"Answer":"You should create a table called something like ExpenseCategories, with the columns ExpenseCategory, PrimaryCategory.\nThis table would have one row for each expense category (which you can enforce with a constraint if you like).  You would then join this table with your existing data in SQL.\nBy the way, in Excel, you could do this with a vlookup() rather than an if().  The vlookup() is analogous to using a lookup table in SQL.  The equivalent of an if() would be a giant case statement, which is another possibility.","Q_Score":0,"Tags":"python,sql","A_Id":11121498,"CreationDate":"2012-06-20T14:05:00.000","Title":"Method for Sorting a list of expense categories into specific categories","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"As a relatively new programmer, I have several times encountered situations where it would be beneficial for me to read and assemble program data from an external source rather than have it written in the code. This is mostly the case when there are a large number of objects of the same type. In such scenarios, object definitions quickly take up a lot of space in the code and add unnecessary impediment to readability. \nAs an example, I've been working on text-based RPG, which has a large number of rooms and items of which to keep track. Even a few items and rooms leads to massive blocks of object creation code.\nI think it would be easier in this case to use some format of external data storage, reading from a file. In such a file, items and rooms would be stored by name and attributes, so that they could parsed into an object with relative ease. \nWhat formats would be best for this? I feel a full-blown database such as SQL would add unnecessary bloat to a fairly light script. On the other hand, an easy method of editing this data is important, either through an external application, or another python script. On the lighter end of things, the few I heard most often mentioned are XML, JSON, and YAML. \nFrom what I've seen, XML does not seem like the best option, as many seem to find it complex and difficult to work with effectively.   \nJSON and YAML seem like either might work, but I don't know how easy it would be to edit either externally.\nSpeed is not a primary concern in this case. While faster implementations are of course desirable, it is not a limiting factor to what I can use.\nI've looked around both here and via Google, and while I've seen quite a bit on the topic, I have not been able to find anything specifically helpful to me. Will formats like JSON or YAML be sufficient for this, or would I be better served with a full-blown database?","AnswerCount":8,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":4619,"Q_Id":11129844,"Users Score":0,"Answer":"I would be tempted to research a little into some GUI that could output graphviz (DOT format) with annotations, so you could create the rooms and links between them (a sort of graph). Then later, you might want another format to support heftier info.\nBut should make it easy to create maps, links between rooms (containing items or traps etc..), and you could use common libraries to produce graphics of the maps in png or something.\nJust a random idea off the top of my head - feel free to ignore!","Q_Score":5,"Tags":"python","A_Id":11130087,"CreationDate":"2012-06-20T23:59:00.000","Title":"Optimal format for simple data storage in python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"As a relatively new programmer, I have several times encountered situations where it would be beneficial for me to read and assemble program data from an external source rather than have it written in the code. This is mostly the case when there are a large number of objects of the same type. In such scenarios, object definitions quickly take up a lot of space in the code and add unnecessary impediment to readability. \nAs an example, I've been working on text-based RPG, which has a large number of rooms and items of which to keep track. Even a few items and rooms leads to massive blocks of object creation code.\nI think it would be easier in this case to use some format of external data storage, reading from a file. In such a file, items and rooms would be stored by name and attributes, so that they could parsed into an object with relative ease. \nWhat formats would be best for this? I feel a full-blown database such as SQL would add unnecessary bloat to a fairly light script. On the other hand, an easy method of editing this data is important, either through an external application, or another python script. On the lighter end of things, the few I heard most often mentioned are XML, JSON, and YAML. \nFrom what I've seen, XML does not seem like the best option, as many seem to find it complex and difficult to work with effectively.   \nJSON and YAML seem like either might work, but I don't know how easy it would be to edit either externally.\nSpeed is not a primary concern in this case. While faster implementations are of course desirable, it is not a limiting factor to what I can use.\nI've looked around both here and via Google, and while I've seen quite a bit on the topic, I have not been able to find anything specifically helpful to me. Will formats like JSON or YAML be sufficient for this, or would I be better served with a full-blown database?","AnswerCount":8,"Available Count":3,"Score":0.1243530018,"is_accepted":false,"ViewCount":4619,"Q_Id":11129844,"Users Score":5,"Answer":"Though there are good answers here already, I would simply recommend JSON for your purposes for the sole reason that since you're a new programmer it will be the most straightforward to read and translate as it has the most direct mapping to native Python data types (lists [] and dictionaries {}).  Readability goes a long way and is one of the tenets of Python programming.","Q_Score":5,"Tags":"python","A_Id":11129974,"CreationDate":"2012-06-20T23:59:00.000","Title":"Optimal format for simple data storage in python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"As a relatively new programmer, I have several times encountered situations where it would be beneficial for me to read and assemble program data from an external source rather than have it written in the code. This is mostly the case when there are a large number of objects of the same type. In such scenarios, object definitions quickly take up a lot of space in the code and add unnecessary impediment to readability. \nAs an example, I've been working on text-based RPG, which has a large number of rooms and items of which to keep track. Even a few items and rooms leads to massive blocks of object creation code.\nI think it would be easier in this case to use some format of external data storage, reading from a file. In such a file, items and rooms would be stored by name and attributes, so that they could parsed into an object with relative ease. \nWhat formats would be best for this? I feel a full-blown database such as SQL would add unnecessary bloat to a fairly light script. On the other hand, an easy method of editing this data is important, either through an external application, or another python script. On the lighter end of things, the few I heard most often mentioned are XML, JSON, and YAML. \nFrom what I've seen, XML does not seem like the best option, as many seem to find it complex and difficult to work with effectively.   \nJSON and YAML seem like either might work, but I don't know how easy it would be to edit either externally.\nSpeed is not a primary concern in this case. While faster implementations are of course desirable, it is not a limiting factor to what I can use.\nI've looked around both here and via Google, and while I've seen quite a bit on the topic, I have not been able to find anything specifically helpful to me. Will formats like JSON or YAML be sufficient for this, or would I be better served with a full-blown database?","AnswerCount":8,"Available Count":3,"Score":0.024994793,"is_accepted":false,"ViewCount":4619,"Q_Id":11129844,"Users Score":1,"Answer":"If you want editability, YAML is the best option of the ones you've named, because it doesn't have <> or {} required delimiters.","Q_Score":5,"Tags":"python","A_Id":11129853,"CreationDate":"2012-06-20T23:59:00.000","Title":"Optimal format for simple data storage in python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I would like to get some understanding on the question that I was pretty sure was clear for me. Is there any way to create table using psycopg2 or any other python Postgres database adapter with the name corresponding to the .csv file and (probably the most important) with columns that are specified in the .csv file.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":2067,"Q_Id":11130261,"Users Score":1,"Answer":"I'll leave you to look at the psycopg2 library properly - this is off the top of my head (not had to use it for a while, but IIRC the documentation is ample).\nThe steps are:\n\nRead column names from CSV file\nCreate \"CREATE TABLE whatever\" ( ... )\nMaybe INSERT data\nimport os.path\nmy_csv_file = '\/home\/somewhere\/file.csv'\ntable_name = os.path.splitext(os.path.split(my_csv_file)[1])[0]\ncols = next(csv.reader(open(my_csv_file)))\n\nYou can go from there...\nCreate a SQL query (possibly using a templating engine for the fields and then issue the insert if needs be)","Q_Score":3,"Tags":"python,postgresql,psycopg2","A_Id":11130568,"CreationDate":"2012-06-21T00:59:00.000","Title":"Dynamically creating table from csv file using psycopg2","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm trying to use PyODBC to connect to an Access database. It works fine on Windows, but running it under OS X I get\u2014\n\nTraceback (most recent call last):\n    File \"\", line 1, in \n    File \"access.py\", line 10, in init\n      self.connection = connect(driver='{Microsoft Access Driver (.mdb)}', dbq=path, pwd=password)\n  pyodbc.Error: ('00000', '[00000] [iODBC][Driver Manager]dlopen({Microsoft Access Driver (.mdb)}, 6): image not found (0) (SQLDriverConnect)')\n\nDo I have to install something else? Have I installed PyODBC wrong?\nThanks","AnswerCount":1,"Available Count":1,"Score":0.537049567,"is_accepted":false,"ViewCount":1896,"Q_Id":11154965,"Users Score":3,"Answer":"pyodbc allows connecting to ODBC data sources, but it does not actually implements drivers. \nI'm not familiar with OS X, but on Linux ODBC sources are typically described in odbcinst.ini file (location is determined by ODBCSYSINI variable). \nYou will need to install Microsoft Access ODBC driver for OS X.","Q_Score":1,"Tags":"python,ms-access,pyodbc","A_Id":11155551,"CreationDate":"2012-06-22T11:03:00.000","Title":"PyODBC \"Image not found (0) (SQLDriverConnect)\"","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Trying to set up Flask and SQLAlchemy on Windows but I've been running into issues.\nI've been using Flask-SQLAlchemy along with PostgreSQL 9.1.4 (32 bit) and the Psycopg2 package. Here are the relevant bits of code, I created a basic User model just to test that my DB is connecting, and committing.\nThe three bits of code would come from the __init__.py file of my application, the models.py file and my settings.py file.\nWhen I try opening up my interactive prompt and try the code in the following link out I get a ProgrammingError exception (details in link).\nWhat could be causing this? I followed the documentation and I'm simply confused as to what I'm doing wrong especially considering that I've also used Django with psycopg2 and PostgreSQL on Windows.","AnswerCount":3,"Available Count":1,"Score":0.2605204458,"is_accepted":false,"ViewCount":7080,"Q_Id":11167518,"Users Score":4,"Answer":"At the time you execute create_all, models.py has never been imported, so no class is declared. Thus, create_all does not create any table.\nTo solve this problem, import models before running create_all or, even better, don't separate the db object from the model declaration.","Q_Score":1,"Tags":"python,sqlalchemy,flask,flask-sqlalchemy","A_Id":11210290,"CreationDate":"2012-06-23T06:47:00.000","Title":"Setting up Flask-SQLAlchemy","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I need to load fixtures into the system when a new VM is up. I have dumped MongoDB and Postgres. But I can't just sit in front of the PC whenever a new machine is up. I want to be able to just \"issue\" a command or the script automatically does it.\nBut a command like pg_dump to dump PostgreSQL will require a password. The problem is, the script that I uses to deploy these fixtures should be under version control. The file that contains this password (if that's the only way to do automation) will not be committed. If it needs to be committed, the deploy repository is restricted for internal developers only.\nMy question is... what do you consider a good practice in this situation? I am thinking of using Python's Popen to issue these commands. \nThanks.\nI also can put it in the cache server... but not sure if it's the only \"better\" way...","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":70,"Q_Id":11174324,"Users Score":0,"Answer":"You have to give the user that loads the fixture the privileges to write on the database regardless which way you are going to load the data.\nWith Postgres you can give login permission without password to specific users and eliminate the problem of a shared password or you can store the password in the pgpass file within the home directory.\nPersonally I find fabric a very nice tool to do deploys, in this specific case I will use it to connect to the remote machine and issue a psql -f 'dump_data.sql' -1 command.","Q_Score":1,"Tags":"python,deployment,fixtures","A_Id":11174357,"CreationDate":"2012-06-24T01:20:00.000","Title":"Security concerns while loading fixtures","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a desktop app that has 65 modules, about half of which read from or write to an SQLite database.  I've found that there are 3 ways that the database can throw an SQliteDatabaseError: \n\nSQL logic error or missing database (happens unpredictably every now and then)\nDatabase is locked (if it's being edited by another program, like SQLite Database Browser)\nDisk I\/O error (also happens unpredictably)\n\nAlthough these errors don't happen often, when they do they lock up my application entirely, and so I can't just let them stand.  \nAnd so I've started re-writing every single access of the database to be a pointer to a common \"database-access function\" in its own module.  That function then can catch these three errors as exceptions and thereby not crash, and also alert the user accordingly.  For example, if it is a \"database is locked error\", it will announce this and ask the user to close any program that is also using the database and then try again.  (If it's the other errors, perhaps it will tell the user to try again later...not sure yet).  Updating all the database accesses to do this is mostly a matter of copy\/pasting the redirect to the common function--easy work.\nThe problem is: it is not sufficient to just provide this database-access function and its announcements, because at all of the points of database access in the 65 modules there is code that follows the access that assumes the database will successfully return data or complete a write--and when it doesn't, that code has to have a condition for that.  But writing those conditionals requires carefully going into each access point and seeing how best to handle it.  This is laborious and difficult for the couple of hundred database accesses I'll need to patch in this way.\nI'm willing to do that, but I thought I'd inquire if there were a more efficient\/clever way or at least heuristics that would help in finishing this fix efficiently and well.\n(I should state that there is no particular \"architecture\" of this application...it's mostly what could be called \"ravioli code\", where the GUI and database calls and logic are all together in units that \"go together\".  I am not willing to re-write the architecture of the whole project in MVC or something like this at this point, though I'd consider it for future projects.)","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":237,"Q_Id":11215535,"Users Score":1,"Answer":"Your gut feeling is right.  There is no way to add robustness to the application without reviewing each database access point separately.\nYou still have a lot of important choice at how the application should react on errors that depends on factors like,\n\nIs it attended, or sometimes completely unattended?\nIs delay OK, or is it important to report database errors promptly?\nWhat are relative frequencies of the three types of failure that you describe?\n\nNow that you have a single wrapper, you can use it to do some common configuration and error handling, especially:\n\nset reasonable connect timeouts\nset reasonable busy timeouts\nenforce command timeouts on client side\nretry automatically on errors, especially on SQLITE_BUSY (insert large delays between retries, fail after a few retries)\nuse exceptions to reduce the number of application level handlers.  You may be able to restart the whole application on database errors.  However, do that only if you have confidence as to in which state you are aborting the application; consistent use of transactions may ensure that the restart method does not leave inconsistent data behind.\nask a human for help when you detect a locking error\n\n...but there comes a moment where you need to bite the bullet and let the error out into the application, and see what all the particular callers are likely to do with it.","Q_Score":2,"Tags":"python,database,sqlite,error-handling","A_Id":11215911,"CreationDate":"2012-06-26T20:38:00.000","Title":"Efficient approach to catching database errors","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm just curious that there are modern systems out there that default to something other than UTF-8. I've had a person block for an entire day on the multiple locations that a mysql system can have different encoding. Very frustrating. \nIs there any good reason not to use utf-8 as a default (and storage space seems like not a good reason)? Not trying to be argumentitive, just curious.\nthx","AnswerCount":2,"Available Count":2,"Score":1.0,"is_accepted":false,"ViewCount":519,"Q_Id":11219060,"Users Score":6,"Answer":"Once upon a time there was no unicode or UTF-8, and disparate encoding schemes were in use throughout the world.  \nIt wasn't until back in 1988 that the initial unicode proposal was issued, with the goal of encoding all the worlds characters in a common encoding.  \nThe first release in 1991 covered many character representations, however, it wasn't until 2006 that Balinese, Cuneiform, N'Ko, Phags-pa, and Phoenician were added.  \nUntil then the Phoenicians, and the others, were unable to represent their language in UTF-8 pissing off many programmers who wondered why everything was not just defaulting to UTF-8.","Q_Score":8,"Tags":"python,mysql,ruby,utf-8","A_Id":11219610,"CreationDate":"2012-06-27T03:37:00.000","Title":"why doesn't EVERYTHING default to UTF-8?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm just curious that there are modern systems out there that default to something other than UTF-8. I've had a person block for an entire day on the multiple locations that a mysql system can have different encoding. Very frustrating. \nIs there any good reason not to use utf-8 as a default (and storage space seems like not a good reason)? Not trying to be argumentitive, just curious.\nthx","AnswerCount":2,"Available Count":2,"Score":-0.0996679946,"is_accepted":false,"ViewCount":519,"Q_Id":11219060,"Users Score":-1,"Answer":"Some encodings have different byte orders (little and big endian)","Q_Score":8,"Tags":"python,mysql,ruby,utf-8","A_Id":11219088,"CreationDate":"2012-06-27T03:37:00.000","Title":"why doesn't EVERYTHING default to UTF-8?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm trying to create a python script that constructs valid sqlite queries. I want to avoid SQL Injection, so I cannot use '%s'. I've found how to execute queries, cursor.execute('sql ?', (param)), but I want how to get the parsed sql param. It's not a problem if I have to execute the query first in order to obtain the last query executed.","AnswerCount":4,"Available Count":3,"Score":0.049958375,"is_accepted":false,"ViewCount":1125,"Q_Id":11223147,"Users Score":1,"Answer":"If you're not after just parameter substitution, but full construction of the SQL, you have to do that using string operations on your end. The ? replacement always just stands for a value. Internally, the SQL string is compiled to SQLite's own bytecode (you can find out what it generates with EXPLAIN thesql) and ? replacements are done by just storing the value at the correct place in the value stack; varying the query structurally would require different bytecode, so just replacing a value wouldn't be enough.\nYes, this does mean you have to be ultra-careful. If you don't want to allow updates, try opening the DB connection in read-only mode.","Q_Score":0,"Tags":"python,sqlite","A_Id":11224222,"CreationDate":"2012-06-27T09:27:00.000","Title":"Python + Sqlite 3. How to construct queries?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm trying to create a python script that constructs valid sqlite queries. I want to avoid SQL Injection, so I cannot use '%s'. I've found how to execute queries, cursor.execute('sql ?', (param)), but I want how to get the parsed sql param. It's not a problem if I have to execute the query first in order to obtain the last query executed.","AnswerCount":4,"Available Count":3,"Score":1.2,"is_accepted":true,"ViewCount":1125,"Q_Id":11223147,"Users Score":1,"Answer":"If you're trying to transmit changes to the database to another computer, why do they have to be expressed as SQL strings?  Why not pickle the query string and the parameters as a tuple, and have the other machine also use SQLite parameterization to query its database?","Q_Score":0,"Tags":"python,sqlite","A_Id":11224475,"CreationDate":"2012-06-27T09:27:00.000","Title":"Python + Sqlite 3. How to construct queries?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm trying to create a python script that constructs valid sqlite queries. I want to avoid SQL Injection, so I cannot use '%s'. I've found how to execute queries, cursor.execute('sql ?', (param)), but I want how to get the parsed sql param. It's not a problem if I have to execute the query first in order to obtain the last query executed.","AnswerCount":4,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":1125,"Q_Id":11223147,"Users Score":0,"Answer":"I want how to get the parsed 'sql param'.\n\nIt's all open source so you have full access to the code doing the parsing \/ sanitization. Why not just reading this code and find out how it works and if there's some (possibly undocumented) implementation that you can reuse ?","Q_Score":0,"Tags":"python,sqlite","A_Id":11224003,"CreationDate":"2012-06-27T09:27:00.000","Title":"Python + Sqlite 3. How to construct queries?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"There is a worksheet.title method but not workbook.title method. Looking in the documentation there is no explicit way to find it, I wasn't sure if anyone knew a workaround or trick to get it.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":10098,"Q_Id":11233140,"Users Score":2,"Answer":"A workbook doesn't really have a name - normally you'd just consider it to be the basename of the file it's saved as... slight update - yep, even in VB WorkBook.Name just returns \"file on disk.xls\"","Q_Score":3,"Tags":"python,excel,openpyxl","A_Id":11233362,"CreationDate":"2012-06-27T18:54:00.000","Title":"Is there a way to get the name of a workbook in openpyxl","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am running a webapp on google appengine with python and my app lets users post topics and respond to them and the website is basically a collection of these posts categorized onto different pages.\nNow I only have around 200 posts and 30 visitors a day right now but that is already taking up nearly 20% of my reads and 10% of my writes with the datastore.  I am wondering if it is more efficient to use the google app engine's built in get_by_id() function to retrieve posts by their IDs or if it is better to build my own.  For some of the queries I will simply have to use GQL or the built in query language because they are retrieved on more than just and ID but I wanted to see which was better.\nThanks!","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":82,"Q_Id":11270434,"Users Score":0,"Answer":"I'd suggest using pre-existing code and building around that in stead of re-inventing the wheel.","Q_Score":0,"Tags":"python,google-app-engine,indexing,google-cloud-datastore","A_Id":11270908,"CreationDate":"2012-06-30T00:18:00.000","Title":"use standard datastore index or build my own","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"We are using Python Pyramid with SQLAlchemy and MySQL to build a web application. We would like to have user-specific database connections, so every web application user has their own database credentials. This is primarily for security reasons, so each user only has privileges for their own database content. We would also like to maintain the performance advantage of connection pooling. Is there a way we can setup a new engine at login time based on the users credentials, and reuse that engine for requests made by the same user?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":343,"Q_Id":11299182,"Users Score":0,"Answer":"The best way to do this that I know is to use the same database with multiple schemas. Unfortunately I don't think this works with MySQL. The idea is that you connection pool engines to the same database and then when you know what user is associated with the request you can switch schemas for that connection.","Q_Score":0,"Tags":"python,sqlalchemy,pyramid","A_Id":11300227,"CreationDate":"2012-07-02T18:29:00.000","Title":"How to manage user-specific database connections in a Pyramid Web Application?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have successfully installed py27-mysql from MacPorts and MySQL-python-1.2.3c1 on a machine running Snow Leopard. Because I have MySQL 5.1.48 in an odd location (\/usr\/local\/mysql\/bin\/mysql\/), I had to edit the setup.cfg file when I installed mysql-python. However, now that it's installed, I'm still getting the error \"ImportError: No module named MySQLdb\" when I run \"import MySQLdb\" in python. What is left to install? Thanks.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":67,"Q_Id":11304019,"Users Score":0,"Answer":"MacPorts' py27-mysql, MySQL-python, and MySQLdb are all synonyms for the same thing. If you successfully installed py27-mysql, you should not need anything else, and it's possible you've messed up your python site-packages. Also, make sure you are invoking the right python binary, i.e. MacPorts' python27 and not the one that comes with Mac OS X.","Q_Score":0,"Tags":"mysql-python","A_Id":12535972,"CreationDate":"2012-07-03T03:19:00.000","Title":"setting up mysql-python on Snow Leopard","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Now on writing path as sys.path.insert(0,'\/home\/pooja\/Desktop\/mysite'), it ran fine asked me for the word tobe searched and gave this error: \n\nTraceback (most recent call last):\nFile \"call.py\", line 32, in \ns.save()\nFile\n  \"\/usr\/local\/lib\/python2.6\/dist-packages\/django\/db\/models\/base.py\",\n  line 463, in save\nself.save_base(using=using, force_insert=force_insert,\n  force_update=force_update)\nFile\n  \"\/usr\/local\/lib\/python2.6\/dist-packages\/django\/db\/models\/base.py\",\n  line 524, in \nsave_base\nmanager.using(using).filter(pk=pk_val).exists())):\nFile\n  \"\/usr\/local\/lib\/python2.6\/dist-packages\/django\/db\/models\/query.py\",\n  line 562, in exists\nreturn self.query.has_results(using=self.db)\nFile\n  \"\/usr\/local\/lib\/python2.6\/dist-packages\/django\/db\/models\/sql\/query.py\",\n  line 441, in has_results\nreturn bool(compiler.execute_sql(SINGLE))\nFile\n  \"\/usr\/local\/lib\/python2.6\/dist-packages\/django\/db\/models\/sql\/compiler.py\",\n  line 818, in execute_sql\ncursor.execute(sql, params)\nFile\n  \"\/usr\/local\/lib\/python2.6\/dist-packages\/django\/db\/backends\/util.py\",\n  line 40, in execute\nreturn self.cursor.execute(sql, params)    File\n  \"\/usr\/local\/lib\/python2.6\/dist-packages\/django\/db\/backends\/sqlite3\/base.py\",\n  line 337, in execute\n       return Database.Cursor.execute(self, query, params)\ndjango.db.utils.DatabaseError: no such table: search_keywords\n\nPlease help!!","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":768,"Q_Id":11307928,"Users Score":1,"Answer":"The exception says: no such table: search_keywords, which is quite self-explanatory and means that there is no database table with such name. So:\n\nYou may be using relative path to db file in settings.py, which resolves to a different db depending on place where you execute the script. Try to use absolute path and see if it helps.\nYou have not synced your models with the database. Run manage.py syncdb to generate the database tables.","Q_Score":1,"Tags":"python,django,linux,sqlite,ubuntu-10.04","A_Id":11308029,"CreationDate":"2012-07-03T09:18:00.000","Title":"error in accessing table created in django in the python code","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"im running a multi tenant GAE app where each tenant could have from a few 1000 to 100k documents.\nat this moment im trying to make a MVC javascript client app (the admin part of my app with spine.js) and i need CRUD endpoints and the ability to get a big amount of serialized objects at once. for this specific job appengine is way to slow. i tried to store serialized objects in the blobstore but between reading\/writing and updating stuff to the blobstore it takes too much time and the app gets really slow. \ni thought of using a nosql db on an external machine to do these operations over appengine. \na few options would be mongodb, couchdb or redis. but i am not sure about how good they perform with that much data and concurrent requests\/inserts from different tenants. \nlets say i have 20 tenants and each tenant has 50k docs. are these dbs capable to handle this load?\nis this even the right way to go?","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":239,"Q_Id":11319890,"Users Score":0,"Answer":"The overhead of making calls from appengine to these external machines is going to be worse than the performance you're seeing now (I would expect). why not just move everything to a non-appengine machine?\nI can't speak for couch, but mongo or redis are definitely capable of handling serious load as long as they are set up correctly and with enough horsepower for your needs.","Q_Score":1,"Tags":"javascript,python,google-app-engine,nosql,multi-tenant","A_Id":11319983,"CreationDate":"2012-07-03T22:08:00.000","Title":"key\/value store with good performance for multiple tenants","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"im running a multi tenant GAE app where each tenant could have from a few 1000 to 100k documents.\nat this moment im trying to make a MVC javascript client app (the admin part of my app with spine.js) and i need CRUD endpoints and the ability to get a big amount of serialized objects at once. for this specific job appengine is way to slow. i tried to store serialized objects in the blobstore but between reading\/writing and updating stuff to the blobstore it takes too much time and the app gets really slow. \ni thought of using a nosql db on an external machine to do these operations over appengine. \na few options would be mongodb, couchdb or redis. but i am not sure about how good they perform with that much data and concurrent requests\/inserts from different tenants. \nlets say i have 20 tenants and each tenant has 50k docs. are these dbs capable to handle this load?\nis this even the right way to go?","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":239,"Q_Id":11319890,"Users Score":2,"Answer":"Why not use the much faster regular appengine datastore instead of blobstore? Simply store your documents in regular entities as Blob property. Just make sure the entity size doesn't exceed 1 MB in which case you have to split up your data into more then one entity. I run an application whith millions of large Blobs that way.\nTo further speed up things use memcache or even in-memory cache. Consider fetching your entites with eventual consistency which is MUCH faster. Run as many database ops in parallel as possible using either bulk operations or the async API.","Q_Score":1,"Tags":"javascript,python,google-app-engine,nosql,multi-tenant","A_Id":11323377,"CreationDate":"2012-07-03T22:08:00.000","Title":"key\/value store with good performance for multiple tenants","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"Not sure if the title is a great way to word my actual problem and I apologize if this is too general of a question but I'm having some trouble wrapping my head around how to do something. \nWhat I'm trying to do:\nThe idea is to create a MySQL database of 'outages' for the thousands of servers I'm responsible for monitoring. This would give a historical record of downtime and an easy way to retroactively tell what happened. The database will be queried by a fairly simple PHP form where one could browse these outages by date or server hostname etc. \nWhat I have so far:\nI have a python script that runs as a cron periodically to call the Pingdom API to get a list of current down alerts reported by the pingdom service. For each down alert, a row is inserted into a database containing a hostname, time stamp, pingdom check id, etc. I then have a simple php form that works fine to query for down alerts. \nThe problem:\nWhat I have now is missing some important features and isn't quite what I'm looking for. Currently, querying this database would give me a simple list of down alerts like this:\nPindom alerts for Test_Check from 2012-05-01 to 2012-06-30:\ntest_check was reported DOWN at 2012-05-24 00:11:11\ntest_check was reported DOWN at 2012-05-24 00:17:28\ntest_check was reported DOWN at 2012-05-24 00:25:24\ntest_check was reported DOWN at 2012-05-24 00:25:48\nWhat I would like instead is something like this:\ntest_check was reported down for 15 minutes (2012-05-24 00:11:11 to 2012-05-24 00:25:48)(link to comment on this outage)(link to info on this outage). \nIn this ideal end result, there would be one row containing a outage ID, hostname of the server pingdom is reporting down, the timestamp for when that box was reported down originally and the timestamp for when it was reported up again along with a 'comment' field I (and other admins) would use to add notes about this particular event after the fact. I'm not sure if I should try to do this when pulling the alerts from pingdom or if I should re-process the alerts after they're collected to populate the new table and I'm not quite sure how I would work out either of those options.\nI'm a little lost as to how I will go about combining several down alerts that occur within a short period of time into a single 'outage' that would be inserted into a separate table in the existing MySQL database where individual down alerts are currently being stored. This would allow me to comment and add specific details for future reference and would generally make this thing a lot more usable. I'm not sure if I should try to do this when pulling the alerts from pingdom or if I should re-process the alerts after they're collected to populate the new table and I'm not quite sure how I would work out either of those options.\nI've been wracking my brain trying to figure out how to do this. It seems like a simple concept but I'm a somewhat inexperienced programmer (I'm a Linux admin by profession) and I'm stumped at this point. \nI'm looking for any thoughts, advice, examples or even just a more technical explanation of what I'm trying to do here to help point me in the right direction. I hope this makes sense. Thanks in advance for any advice :)","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":131,"Q_Id":11329588,"Users Score":0,"Answer":"The most basic solution with the setup you have now would be to:\n\nGet a list of all events, ordered by server ID and then by time of the event\nLoop through that list and record the start of a new event \/ end of an old event for your new database when:\n\nthe server ID changes\nthe time between the current event and the previous event from the same server is bigger than a certain threshold you set.\nStore the old event you were monitoring in your new database\n\n\nThe only complication I see, is that the next time you run the script, you need to make sure that you continue monitoring events that were still taking place at the time you last ran the script.","Q_Score":0,"Tags":"php,python,mysql,json,pingdom","A_Id":11329769,"CreationDate":"2012-07-04T12:56:00.000","Title":"How can I combine rows of data into a new table based on similar timestamps? (python\/MySQL\/PHP)","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm writing a bit of Python code that watches a certain directory for new files, and inserts new files into a database using the cx_Oracle module. This program will be running as a service. At a given time there could be many files arriving at once, but there may also be periods of up to an hour where no files are received. Regarding good practice: is it bad to keep a database connection open indefinitely? On one hand something tells me that it's not a good idea, but on the other hand there is a lot of overhead in creating a new database object for every file received and closing it afterwards, especially when many files are received at once. Any suggestions on how to approach this would be greatly appreciated.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1153,"Q_Id":11346224,"Users Score":2,"Answer":"If you only need one or two connections, I see no harm in keeping them open indefinitely.\nWith Oracle, creating a new connection is an expensive operation, unlike in some other databases, such as MySQL where it is very cheap to create a new connection.  Sometimes it can even take a few seconds to connect which can become a bit of a bottleneck for some applications if they close and open connections too frequently.\nAn idle connection on Oracle uses a small amount of memory, but aside from that, it doesn't consume any other resources while it sits there idle.\nTo keep your DBAs happy, you will want to make sure you don't have lots of idle connections left open, but I'd be happy with one or two.","Q_Score":3,"Tags":"python,oracle","A_Id":11347776,"CreationDate":"2012-07-05T14:17:00.000","Title":"Keeping database connection open - good practice?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am trying to query ODBC compliant databases using pyodbc in ubuntu. For that, i have installed the driver (say mysql-odbc-driver). After installation the odbcinst.ini file with the configurations gets created in the location \/usr\/share\/libmyodbc\/odbcinst.ini\nWhen i try to connect to the database using my pyodbc connection code, i get a driver not found error message.\nNow when I copy the contents of the file to \/etc\/odbcinst.ini, it works!\nThis means pyodbc searches for the driver information in file \/etc\/odbcinst.ini.\nHow can I change the location where it searches the odbcinst.ini file for the driver information\nThanks.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":7504,"Q_Id":11393269,"Users Score":6,"Answer":"Assuming you are using unixODBC here was some possibilities:\n\nrebuild unixODBC from scratch and set --sysconfdir\nexport ODBCSYSINI  env var pointing to a directory and unixODBC will look here for odbcinst.ini and odbc.ini system dsns\nexport ODBCINSTINI and point it at your odbcinst.ini file\n\nBTW, I doubt pyodbc looks anything up in the odbcinst.ini file but unixODBC will. There is a list of ODBC Driver manager APIs which can be used to examine ODBC ini files.","Q_Score":5,"Tags":"python,odbc,pyodbc","A_Id":11393468,"CreationDate":"2012-07-09T10:30:00.000","Title":"setting the location where pyodbc searches for odbcinst.ini file","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"There is a list of data that I want to deal with. However I need to process the data with multiple instances to increase efficiency. \nEach time each instance shall take out one item, delete it from the list and process it with some procedures.\nFirst I tried to store the list in a sqlite database, but sqlite allows multiple read-locks which means multiple instances might get the same item from the database.\nIs there any way that makes each instance will get an unique item to process?\nI could use other data structure (other database or just file) if needed.\nBy the way, is there a way to check whether a DELETE operation is successful or not, after executing cursor.execute(delete_query)?","AnswerCount":4,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":484,"Q_Id":11430276,"Users Score":0,"Answer":"Why not read in all the items from the database and put them in a queue? You can have a worker thread get at item, process it and move on to the next one.","Q_Score":0,"Tags":"python,database,sqlite,concurrency,locking","A_Id":20908479,"CreationDate":"2012-07-11T10:07:00.000","Title":"Concurrency on sqlite database using python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"There is a list of data that I want to deal with. However I need to process the data with multiple instances to increase efficiency. \nEach time each instance shall take out one item, delete it from the list and process it with some procedures.\nFirst I tried to store the list in a sqlite database, but sqlite allows multiple read-locks which means multiple instances might get the same item from the database.\nIs there any way that makes each instance will get an unique item to process?\nI could use other data structure (other database or just file) if needed.\nBy the way, is there a way to check whether a DELETE operation is successful or not, after executing cursor.execute(delete_query)?","AnswerCount":4,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":484,"Q_Id":11430276,"Users Score":0,"Answer":"How about another field in db as a flag (e.g. PROCESSING, UNPROCESSED, PROCESSED)?","Q_Score":0,"Tags":"python,database,sqlite,concurrency,locking","A_Id":11430479,"CreationDate":"2012-07-11T10:07:00.000","Title":"Concurrency on sqlite database using python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm writing a script to be run as a cron and I was wondering, is there any difference in speed between the Ruby MySQL or Python MySQL in terms of speed\/efficiency?  Would I be better of just using PHP for this task?\nThe script will get data from a mysql database with 20+ fields and store them in another table every X amount of minutes.  Not much processing of the data will be necessary.","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":254,"Q_Id":11431679,"Users Score":7,"Answer":"Just pick the language you feel most comfortable with. It shouldn't make a noticeable difference. \nAfter writing the application, you can search for bottlenecks and optimize that","Q_Score":0,"Tags":"python,mysql,ruby","A_Id":11431795,"CreationDate":"2012-07-11T11:28:00.000","Title":"Python MySQL vs Ruby MySQL","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"since it is not possible to access mysql remotely on GAE, without the google cloud sql, \ncould I put a sqlite3 file on google cloud storage and access it through the GAE with django.db.backends.sqlite3?\nThanks.","AnswerCount":3,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":2078,"Q_Id":11462291,"Users Score":0,"Answer":"No. SQLite requires native code libraries that aren't available on App Engine.","Q_Score":1,"Tags":"python,django,sqlite,google-app-engine,google-cloud-storage","A_Id":11498320,"CreationDate":"2012-07-12T23:44:00.000","Title":"Google App Engine + Google Cloud Storage + Sqlite3 + Django\/Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"since it is not possible to access mysql remotely on GAE, without the google cloud sql, \ncould I put a sqlite3 file on google cloud storage and access it through the GAE with django.db.backends.sqlite3?\nThanks.","AnswerCount":3,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":2078,"Q_Id":11462291,"Users Score":0,"Answer":"Google Cloud SQL is meant for this, why don't you want to use it?\nIf you have every frontend instance load the DB file, you'll have a really hard time synchronizing them.  It just doesn't make sense.  Why would you want to do this?","Q_Score":1,"Tags":"python,django,sqlite,google-app-engine,google-cloud-storage","A_Id":11463047,"CreationDate":"2012-07-12T23:44:00.000","Title":"Google App Engine + Google Cloud Storage + Sqlite3 + Django\/Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"Is it possible to determine fields available in a table (MySQL DB) pragmatically at runtime using SQLAlchemy or any other python library ? Any help on this would be great.\nThanks.","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":103,"Q_Id":11500239,"Users Score":0,"Answer":"You can run the SHOW TABLE TABLENAME and get the columns of the tables.","Q_Score":4,"Tags":"python,sqlalchemy","A_Id":11500397,"CreationDate":"2012-07-16T08:00:00.000","Title":"How to determine fields in a table using SQLAlchemy?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I wanted to know whether mysql query with browser is faster or python's MySQLdb is faster. I am using MysqlDb with PyQt4 for desktop ui and PHP for web ui.","AnswerCount":2,"Available Count":2,"Score":0.0996679946,"is_accepted":false,"ViewCount":161,"Q_Id":11508670,"Users Score":1,"Answer":"I believe you're asking about whether Python or PHP (what I think you mean by browser?) is more efficient at making a database call.\nThe answer? It depends on the specific code and calls, but it's going to be largely the same. Both Python and PHP are interpreted languages and interpret the code at run time. If either of the languages you were using were compiled (say, like, if you used C), I'd say you might see a speed advantage of one over the other, but with the current information you've given us, I can't really judge that.\nI would use the language you are most comfortable in or feel would best fit the task - they're both going to connect to a MySQL database and do the same exact commands and queries, so just write the code in the easiest way possible for you to do it.\nAlso, your question as posed doesn't make much sense. Browsers don't interact with a MySQL database, PHP, which is executed by a server when you request a page, does.","Q_Score":0,"Tags":"php,python,mysql,pyqt4,mysql-python","A_Id":11510083,"CreationDate":"2012-07-16T16:38:00.000","Title":"browser query vs python MySQLdb query","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I wanted to know whether mysql query with browser is faster or python's MySQLdb is faster. I am using MysqlDb with PyQt4 for desktop ui and PHP for web ui.","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":161,"Q_Id":11508670,"Users Score":0,"Answer":"Browsers don't perform database queries (unless you consider the embedded SQLite database), so not only is your question nonsensical, it is in fact completely irrelevant.","Q_Score":0,"Tags":"php,python,mysql,pyqt4,mysql-python","A_Id":11509874,"CreationDate":"2012-07-16T16:38:00.000","Title":"browser query vs python MySQLdb query","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Trying to do HelloWorld on GoogleAppEngine, but getting the following error.\nC:\\LearningGoogleAppEngine\\HelloWorld>dev_appserver.py helloworld\nWARNING  2012-07-17 10:21:37,250 rdbms_mysqldb.py:74] The rdbms API is not available because the MySQLdb library could not be loaded.\nTraceback (most recent call last):\nFile \"C:\\Program Files (x86)\\Google\\google_appengine\\dev_appserver.py\", line 133, in \nrun_file(file, globals())\nFile \"C:\\Program Files (x86)\\Google\\google_appengine\\dev_appserver.py\", line 129, in run_file\nexecfile(script_path, globals_)\nFile \"C:\\Program Files (x86)\\Google\\google_appengine\\google\\appengine\\tools\\dev_appserver_main.py\", line 694, in  sys.exit(main(sys.argv))\nFile \"C:\\Program Files (x86)\\Google\\google_appengine\\google\\appengine\\tools\\dev_appserver_main.py\", line 582, in main root_path, {}, default_partition=default_partition)\nFile \"C:\\Program Files (x86)\\Google\\google_appengine\\google\\appengine\\tools\\dev_appserver.py\", line 3217, in LoadAppConfig raise AppConfigNotFoundError\ngoogle.appengine.tools.dev_appserver.AppConfigNotFoundError\nI've found posts on GoogleCode, StackO regarding this issue. But no matter what I try, I still can't overcome this error.\nPython version installed on Windows 7 machine is: 2.7.3\nGAE Launcher splash screen displays the following:\nRelease 1.7.0\nApi versions: ['1']\nPython: 2.5.2\nwxPython : 2.8.8.1(msw-unicode) \nCan someone help?","AnswerCount":3,"Available Count":2,"Score":0.0665680765,"is_accepted":false,"ViewCount":1146,"Q_Id":11520573,"Users Score":1,"Answer":"it's been a while, but I believe I've previously fixed this by adding import rdbms to dev_appserver.py\nhmm.. or was that import MySQLdb? (more likely)","Q_Score":3,"Tags":"google-app-engine,python-2.7","A_Id":11533684,"CreationDate":"2012-07-17T10:25:00.000","Title":"GoogleAppEngine error: rdbms_mysqldb.py:74","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"Trying to do HelloWorld on GoogleAppEngine, but getting the following error.\nC:\\LearningGoogleAppEngine\\HelloWorld>dev_appserver.py helloworld\nWARNING  2012-07-17 10:21:37,250 rdbms_mysqldb.py:74] The rdbms API is not available because the MySQLdb library could not be loaded.\nTraceback (most recent call last):\nFile \"C:\\Program Files (x86)\\Google\\google_appengine\\dev_appserver.py\", line 133, in \nrun_file(file, globals())\nFile \"C:\\Program Files (x86)\\Google\\google_appengine\\dev_appserver.py\", line 129, in run_file\nexecfile(script_path, globals_)\nFile \"C:\\Program Files (x86)\\Google\\google_appengine\\google\\appengine\\tools\\dev_appserver_main.py\", line 694, in  sys.exit(main(sys.argv))\nFile \"C:\\Program Files (x86)\\Google\\google_appengine\\google\\appengine\\tools\\dev_appserver_main.py\", line 582, in main root_path, {}, default_partition=default_partition)\nFile \"C:\\Program Files (x86)\\Google\\google_appengine\\google\\appengine\\tools\\dev_appserver.py\", line 3217, in LoadAppConfig raise AppConfigNotFoundError\ngoogle.appengine.tools.dev_appserver.AppConfigNotFoundError\nI've found posts on GoogleCode, StackO regarding this issue. But no matter what I try, I still can't overcome this error.\nPython version installed on Windows 7 machine is: 2.7.3\nGAE Launcher splash screen displays the following:\nRelease 1.7.0\nApi versions: ['1']\nPython: 2.5.2\nwxPython : 2.8.8.1(msw-unicode) \nCan someone help?","AnswerCount":3,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":1146,"Q_Id":11520573,"Users Score":0,"Answer":"just had the exact same error messages: I found that restarting Windows fixed everything and I did not have to deviate from the YAML or py file given on the google helloworld python tutorial.","Q_Score":3,"Tags":"google-app-engine,python-2.7","A_Id":12513978,"CreationDate":"2012-07-17T10:25:00.000","Title":"GoogleAppEngine error: rdbms_mysqldb.py:74","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I would like to get the suggestion on using No-SQL datastore for my particular requirements.\nLet me explain:\n         I have to process the five csv files. Each csv contains 5 million rows and also The common id field is presented in each csv.So, I need to merge all csv by iterating 5 million rows.So, I go with python dictionary to merge all files based on the common id field.But here the bottleneck is you can't store the 5 million keys in memory(< 1gig) with python-dictionary.\nSo, I decided to use No-Sql.I think It might be helpful to process the 5 million key value storage.Still I didn't have clear thoughts on this.\nAnyway we can't reduce the iteration since we have the five csvs each has to be iterated for updating the values.\nIs it there an simple steps to go with that?\n  If this is the way Could you give me the No-Sql datastore to process the key-value pair?\nNote: We have the values as list type also.","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":347,"Q_Id":11522232,"Users Score":0,"Answer":"If this is just a one-time process, you might want to just setup an EC2 node with more than 1G of memory and run the python scripts there. 5 million items isn't that much, and a Python dictionary should be fairly capable of handling it. I don't think you need Hadoop in this case.\nYou could also try to optimize your scripts by reordering the items in several runs, than running over the 5 files synchronized using iterators so that you don't have to keep everything in memory at the same time.","Q_Score":1,"Tags":"python,nosql","A_Id":11522576,"CreationDate":"2012-07-17T12:15:00.000","Title":"Process 5 million key-value data in python.Will NoSql solve?","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am working on the XLWT XLRD XLUTIL packages. Whenever I write to a new sheet, all the formulas have been obliterated. \nI tried the following fixes, but they all failed:\n\nRe-write all the formulas in with a loop:\nFailure: XLWT Formula does not support advanced i.e. VLOOKUP Formulas\nDoing the calculations all in Python: this is ridiculous\n\nHow can I preserve the formulas using the above packages? Can I use some other packages to solve my problem? Or, do I need to code my own solution?","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":1819,"Q_Id":11527100,"Users Score":1,"Answer":"(a) xlrd does not currently support extracting formulas. \n(b) You say \"XLWT Formula does not support advanced i.e. VLOOKUP Formulas\". This is incorrect. If you are the same person that I seem to have convinced that xlwt supports VLOOKUP etc after a lengthy exchange of private emails over the last few days, please say so. Otherwise please supply a valid (i.e. Excel accepts it) formula that xlwt won't parse correctly.\n(c) Doing the calculations in Python is not ridiculous if the output is only for display.","Q_Score":1,"Tags":"python,excel,formula,xlrd,xlwt","A_Id":11596820,"CreationDate":"2012-07-17T16:44:00.000","Title":"Preserving Formula in Excel Python XLWT","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"How do I specify the column that I want in my query using a model (it selects all columns by default)? I know how to do this with the sqlalchmey session: session.query(self.col1), but how do I do it with with models?  I can't do SomeModel.query(). Is there a way?","AnswerCount":10,"Available Count":1,"Score":0.0399786803,"is_accepted":false,"ViewCount":191024,"Q_Id":11530196,"Users Score":2,"Answer":"result = ModalName.query.add_columns(ModelName.colname, ModelName.colname)","Q_Score":183,"Tags":"python,sqlalchemy,flask-sqlalchemy","A_Id":68064416,"CreationDate":"2012-07-17T20:16:00.000","Title":"Flask SQLAlchemy query, specify column names","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a data organization issue.  I'm working on a client\/server project where the server must maintain a copy of the client's filesystem structure inside of a database that resides on the server.  The idea is to display the filesystem contents on the server side in an AJAX-ified web interface.  Right now I'm simply uploading a list of files to the database where the files are dumped sequentially.  The problem is how to recapture the filesystem structure on the server end once they're in the database.  It doesn't seem feasible to reconstruct the parent->child structure on the server end by iterating through a huge list of files.  However, when the file objects have no references to each other, that seems to be the only option.\nI'm not entirely sure how to handle this.  As near as I can tell, I would need to duplicate some type of filesystem data structure on the server side (in a Btree perhaps?) with objects maintaining pointers to their parents and\/or children.  I'm wondering if anyone has had any similar past experiences they could share, or maybe some helpful resources to point me in the right direction.","AnswerCount":2,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":1195,"Q_Id":11554676,"Users Score":2,"Answer":"I suggest to follow the Unix way. Each file is considered a stream of bytes, nothing more, nothing less. Each file is technically represented by a single structure called i-node (index node) that keeps all information related to the physical stream of the data (including attributes, ownership,...). \nThe i-node does not contain anything about the readable name. Each i-node is given a unique number (forever) that acts for the file as its technical name. You can use similar number to give the stream of bytes in database its unique identification. The i-nodes are stored on the disk in a separate contiguous section -- think about the array of i-node structures (in the abstract sense), or about the separate table in the database.\nBack to the file. This way it is represented by unique number. For your database representation, the number will be the unique key. If you need the other i-node information (file attributes), you can add the other columns to the table. One column will be of the blob type, and it will represent the content of the file (the stream of bytes). For AJAX, I gues that the files will be rather small; so, you should not have a problem with the size limits of the blob.\nSo far, the files are stored in as a flat structure (as the physical disk is, and as the relational database is).\nThe structure of directory names and file names of the files are kept separately, in another files (kept in the same structure, together with the other files, represented also by their i-node). Basically, the directory file captures tuples (bare_name, i-node number). (This way the hard links are implemented in Unix -- two names are paired with the same i-none number.) The root directory file has to have a fixed technical identification -- i.e. the reserved i-node number.","Q_Score":4,"Tags":"python,database,data-structures,filesystems","A_Id":11554828,"CreationDate":"2012-07-19T05:50:00.000","Title":"Data structures in python: maintaining filesystem structure within a database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a huge database in sqlite3 of 41 million rows in a table. However, it takes around 14 seconds to execute a single query. I need to significantly improve the access time! Is this a hard disk hardware limit or a processor limit? If it is a processor limit then I think I can use the 8 processors I have to parallelise the query. However I never found a way to parallelize queries in SQLite for python. Is there any way to do this? Can I have a coding example? Or are other database programs more efficient in access? If so then which ones?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":204,"Q_Id":11556783,"Users Score":1,"Answer":"Firstly, make sure any relevant indexes are in place to assist in efficient queries -- which may or may not help...\nOther than that, SQLite is meant to be a (strangely) lite embedded SQL DB engine - 41 million rows is probably pushing it depending on number and size of columns etc...\nYou could take your DB and import it to PostgreSQL or MySQL, which are both open-source RDMS's with Python bindings and extensive feature sets. They'll be able to handle queries, indexing, caching, memory management etc... on large data effectively. (Or at least, since they're designed for that purpose, more effectively than SQLite which wasn't...)","Q_Score":0,"Tags":"python,sqlite,parallel-processing","A_Id":11557147,"CreationDate":"2012-07-19T08:25:00.000","Title":"reducing SQLITE3 access time in Python (Parallelization?)","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am parsing .xlsx files using openpyxl.While writing into the xlsx files i need to maintain the same font colour as well as cell colour as was present in the cells of my input .xlsx files.Any idea how to extract the colour coding from the cell and then implement the same in another excel file.Thanks in advance","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":116,"Q_Id":11562279,"Users Score":0,"Answer":"I believe you can access the font colour by:\n    colour = ws.cell(row=id,column=id).style.font.color\nI am not sure how to access the cell colour though.","Q_Score":0,"Tags":"python,python-3.x,excel-2007,openpyxl","A_Id":11783592,"CreationDate":"2012-07-19T13:47:00.000","Title":"How to detect colours and then apply colours while working with .xlsx(excel-2007) files on python 3.2(windows 7)","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a mysql table with coloumns of name, perf, date_time . How can i retrieve only the most recent MySQL row?","AnswerCount":6,"Available Count":2,"Score":-0.0333209931,"is_accepted":false,"ViewCount":1336,"Q_Id":11566537,"Users Score":-1,"Answer":"select top 1 * from tablename order by date_and_time DESC (for sql server)\nselect * from taablename order by date_and_time DESC limit 1(for mysql)","Q_Score":3,"Tags":"python,mysql","A_Id":11566922,"CreationDate":"2012-07-19T17:50:00.000","Title":"Retrieving only the most recent row in MySQL","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a mysql table with coloumns of name, perf, date_time . How can i retrieve only the most recent MySQL row?","AnswerCount":6,"Available Count":2,"Score":0.0996679946,"is_accepted":false,"ViewCount":1336,"Q_Id":11566537,"Users Score":3,"Answer":"SELECT * FROM table ORDER BY date, time LIMIT 1","Q_Score":3,"Tags":"python,mysql","A_Id":11566549,"CreationDate":"2012-07-19T17:50:00.000","Title":"Retrieving only the most recent row in MySQL","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am creating a GUI that is dependent on information from MySQL table, what i want to be able to do is to display a message every time the table is updated with new data.  I am not sure how to do this or even if it is possible. I have codes that retrieve the newest MySQL update but I don't know how to have a message every time new data comes into a table. Thanks!","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1004,"Q_Id":11567357,"Users Score":3,"Answer":"Quite simple and straightforward solution will be just to poll the latest autoincrement id from your table, and compare it with what you've seen at the previous poll. If it is greater -- you have new data. This is called 'active polling', it's simple to implement and will suffice if you do this not too often. So you have to store the last id value somewhere in your GUI. And note that this stored value will reset when you restart your GUI application -- be sure to think what to do at the start of the GUI. Probably you will need to track only insertions that occur while GUI is running -- then, at the GUI startup you need just to poll and store current id value, and then poll peroidically and react on its changes.","Q_Score":1,"Tags":"python,mysql","A_Id":11567806,"CreationDate":"2012-07-19T18:48:00.000","Title":"Scanning MySQL table for updates Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Database A resides on server server1, while database B resides on server server2.\nBoth servers {A, B} are physically close to each other, but are on different machines and have different connection parameters (different username, different password etc).\nIn such a case, is it possible to perform a join between a table that is in database A, to a table that is in database B?\nIf so, how do I go about it, programatically,","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":214,"Q_Id":11585494,"Users Score":0,"Answer":"Without doing something like replicating database A onto the same server as database B and then doing the JOIN, this would not be possible.","Q_Score":0,"Tags":"mysql,python-2.7","A_Id":11585571,"CreationDate":"2012-07-20T19:04:00.000","Title":"MySQL Joins Between Databases On Different Servers Using Python?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Database A resides on server server1, while database B resides on server server2.\nBoth servers {A, B} are physically close to each other, but are on different machines and have different connection parameters (different username, different password etc).\nIn such a case, is it possible to perform a join between a table that is in database A, to a table that is in database B?\nIf so, how do I go about it, programatically,","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":214,"Q_Id":11585494,"Users Score":0,"Answer":"I don't know python, so I'm going to assume that when you do a query it comes back to python as an array of rows.\nYou could query table A and after applying whatever filters you can, return that result to the application. Same to table B. Create a 3rd Array, loop through A, and if there is a joining row in B, add that joined row to the 3rd array. In the end the 3rd array would have the equivalent of a join of the two tables. It's not going to be very efficient, but might work okay for small recordsets.","Q_Score":0,"Tags":"mysql,python-2.7","A_Id":11585697,"CreationDate":"2012-07-20T19:04:00.000","Title":"MySQL Joins Between Databases On Different Servers Using Python?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm working on my Thesis where the Python application that connects to other linux servers over SSH is implemented. The question is about storing the passwords in the database (whatever kind, let's say MySQL for now). For sure keeping them not encrypted is a bad idea. But what can I do to feel comfortable with storing this kind of confidential data and use them later to connect to other servers? When I encrypt the password I'll not be able to use it to login the other machine.\nIs the public\/private keys set the only option in this case?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":454,"Q_Id":11587845,"Users Score":3,"Answer":"In my opinion using key authentication is the best and safest in my opinion for the SSH part and is easy to implement.\nNow to the meat of your question. You want to store these keys, or passwords, into a database and still be able to use them.  This requires you to have a master password that can decrypt them from said database.  This points a point of failure into a single password which is not ideal.  You could come up with any number of fancy schemes to encrypt and store these master passwords, but they are still on the machine that is used to log into the other servers and thus still a weak point.\nInstead of looking at this from the password storage point of view, look at it from a server security point of view. If someone has access to the server with the python daemon running on it then they can log into any other server thus this is more of a environment security issue than a password one.\nIf you can think of a way to get rid of this singular point of failure then encrypting and storing the passwords in a remote database will be fine as long as the key\/s used to encrypt them are secure and unavailable to anyone else which is outside the realm of the python\/database relationship.","Q_Score":1,"Tags":"python,mysql,ssh,password-protection","A_Id":11588240,"CreationDate":"2012-07-20T22:40:00.000","Title":"Storing encrypted passwords storage for remote linux servers","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am using python and sqlite3 to handle a website. I need all timezones to be in localtime, and I need daylight savings to be accounted for. The ideal method to do this would be to use sqlite to set a global datetime('now') to be +10 hours.\nIf I can work out how to change sqlite's 'now' with a command, then I was going to use a cronjob to adjust it (I would happily go with an easier method if anyone has one, but cronjob isn't too hard)","AnswerCount":2,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":3357,"Q_Id":11590082,"Users Score":2,"Answer":"you can try this code, I am in Taiwan , so I add 8 hours:\nDateTime('now','+8 hours')","Q_Score":1,"Tags":"python,sqlite,timezone,dst","A_Id":21014456,"CreationDate":"2012-07-21T06:48:00.000","Title":"sqlite timezone now","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am looking for a method of checking all the fields in a MySQL table. Let's say I have a MySQL table with the fields One Two Three Four Five and Big One. These are fields that contains numbers that people enter in, sort of like the Mega Millions. Users enter numbers and it inserts the numbers they picked from least to greatest.\nNumbers would be drawn and I need a way of checking if any of the numbers that each user picked matched the winning numbers drawn, same for the Big One. If any matched, I would have it do something specific, like if one number or all numbers matched.\nI hope you understand what I am saying. Thank you.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":82,"Q_Id":11597835,"Users Score":0,"Answer":"I would imagine MySQL has some sort of 'set' logic in it, but if it's lacking, I know Python has sets, so I'll use an example of those in my solution:\n\nCreate a set with the numbers of the winning ticket:\nwinners = set({11, 22, 33, 44, 55})\nFor each query, jam all it's numbers into a set too:\ncurrent_user = set({$query[0], $query[1], $query[2]...$query[4]})\nPrint out how many overlapping numbers there are:\nprint winners.intersection(current_user)\n\nAnd finally, for the 'big one', use an if statement.\nLet me know if this helps.","Q_Score":1,"Tags":"python,mysql","A_Id":11919262,"CreationDate":"2012-07-22T04:49:00.000","Title":"Python MySQL Number Matching","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm making a company back-end that should include a password-safe type feature. Obviously the passwords needs to be plain text so the users can read them, or at least \"reversible\" to plain text somehow, so I can't use hashes.\nIs there anything more secure I can do than just placing the passwords in plain-text into the database?\n\nNote: These are (mostly) auto-generated passwords that is never re-used for anything except the purpose they are saved for, which is mostly FTP server credentials.","AnswerCount":2,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":105,"Q_Id":11603136,"Users Score":2,"Answer":"You can use MySQL's ENCODE(), DES_ENCRYPT() or AES_ENCRYPT() functions, and store the keys used to encrypt in a secure location.","Q_Score":0,"Tags":"python,mysql,hash,passwords","A_Id":11603255,"CreationDate":"2012-07-22T18:59:00.000","Title":"What security measures can I take to secure passwords that can't be hashed in a database?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am wondering what the most reliable way to generate a timestamp is using Python. I want this value to be put into a MySQL database, and for other programming languages and programs to be able to parse this information and use it.\nI imagine it is either datetime, or the time module, but I can't figure out which I'd use in this circumstance, nor the method.","AnswerCount":3,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":390,"Q_Id":11642105,"Users Score":0,"Answer":"For a database, your best bet is to store it in the database-native format, assuming its precision matches your needs.  For a SQL database, the DATETIME type is appropriate.\nEDIT: Or TIMESTAMP.","Q_Score":0,"Tags":"python,time","A_Id":11642138,"CreationDate":"2012-07-25T03:04:00.000","Title":"Most reliable way to generate a timestamp with Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am wondering what the most reliable way to generate a timestamp is using Python. I want this value to be put into a MySQL database, and for other programming languages and programs to be able to parse this information and use it.\nI imagine it is either datetime, or the time module, but I can't figure out which I'd use in this circumstance, nor the method.","AnswerCount":3,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":390,"Q_Id":11642105,"Users Score":0,"Answer":"if it's just a simple timestamp that needs to be read by multiple programs, but which doesn't need to \"mean\" anything in sql, and you don't care about different timezones for different users or anything like that, then seconds from the unix epoch (start of 1970) is a simple, common standard, and is returned by time.time().\npython actually returns a float (at least on linux), but if you only need accuracy to the second store it as an integer.\nif you want something that is more meaningful in sql then use a sql type like datetime or timestamp.  that lets you do more \"meaningful\" queries (like query for a particular day) more easily (you can do them with seconds from epoch too, but it requires messing around with conversions), but it also gets more complicated with timezones and converting into different formats in different languages.","Q_Score":0,"Tags":"python,time","A_Id":11642253,"CreationDate":"2012-07-25T03:04:00.000","Title":"Most reliable way to generate a timestamp with Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am building a system where entries are added to a SQL database sporadically throughout the day. I am trying to create a system which imports these entries to SOLR each time. \nI cant seem to find any infomation about adding individual records to SOLR from SQL. Can anyone point me in the right direction or give me a bit more information to get me going?\nAny help would be much appreciated,\nJames","AnswerCount":4,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":606,"Q_Id":11647112,"Users Score":0,"Answer":"Besides DIH, you could setup a trigger in your db to fire Solr's REST service that would update changed docs for all inserted\/updated\/deleted documents.\nAlso, you could setup a Filter (javax.servlet spec) in your application to intercept server requests and push them to Solr before they even reach database (it can even be done in the same transaction, but there's rarely a real need for that, eventual consistency is usually fine for search engines).","Q_Score":1,"Tags":"python,search,solr","A_Id":11679439,"CreationDate":"2012-07-25T09:52:00.000","Title":"SOLR - Adding a single entry at a time","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"i am trying to connect to mysql in django. it asked me to install the module. the module prerequisites are \"MySQL 3.23.32 or higher\" etc. do i really need to install mysql, cant i just connect to remote one??","AnswerCount":1,"Available Count":1,"Score":0.6640367703,"is_accepted":false,"ViewCount":62,"Q_Id":11653040,"Users Score":4,"Answer":"You need to install the client libraries. The Python module is a wrapper around the client libraries. You don't need to install the server.","Q_Score":0,"Tags":"python,mysql,django","A_Id":11653215,"CreationDate":"2012-07-25T15:19:00.000","Title":"Not able to install python mysql module","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"when I try to install the pyodbc by using \"python setup.py build install\", it shows up with some errors like the following:\ngcc -pthread -fno-strict-aliasing -DNDEBUG -march=i586 -mtune=i686 -fmessage-length=0 -O2 -Wall -D_FORTIFY_SOURCE=2 -fstack-protector -funwind-tables -fasynchronous-unwind-tables -g -fwrapv -fPIC -DPYODBC_VERSION=3.0.3 -I\/usr\/include\/python2.6 -c \/root\/Desktop\/pyodbc-3.0.3\/src\/sqlwchar.cpp -o build\/temp.linux-i686-2.6\/root\/Desktop\/pyodbc-3.0.3\/src\/sqlwchar.o -Wno-write-strings\nIn file included from \/root\/Desktop\/pyodbc-3.0.3\/src\/sqlwchar.cpp:2:\n\/root\/Desktop\/pyodbc-3.0.3\/src\/pyodbc.h:41:20: error: Python.h: No such file or directory\n\/root\/Desktop\/pyodbc-3.0.3\/src\/pyodbc.h:42:25: error: floatobject.h: No such file or directory\n\/root\/Desktop\/pyodbc-3.0.3\/src\/pyodbc.h:43:24: error: longobject.h: No such file or directory\n\/root\/Desktop\/pyodbc-3.0.3\/src\/pyodbc.h:44:24: error: boolobject.h: No such file or directory\nand few more lines with similar feedback, in the end of the reply is like:\n\/root\/Desktop\/pyodbc-3.0.3\/src\/pyodbccompat.h:106: error: expected \u2018,\u2019 or \u2018;\u2019 before \u2018{\u2019 token\nerror: command 'gcc' failed with exit status 1\nand I have searched around for the solutions, everyone says to install python-devel and it will be fine, but I got this working on a 64bit opensuse without the python-devel,but it doesn't work on the 32bit one, and I couldn't found the right version for python2.6.0-8.12.2 anywhere on the internet... so I'm quite confused, please help! thanks in advance.","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":4644,"Q_Id":11691039,"Users Score":2,"Answer":"I don't see a way around having the Python header files (which are part of python-devel package). They are required to compile the package.\nMaybe there was a pre-compiled egg for the 64bit version somewhere, and this is how it got installed.\nWhy are you reluctant to install python-devel?","Q_Score":1,"Tags":"python,pyodbc,opensuse","A_Id":11691895,"CreationDate":"2012-07-27T15:32:00.000","Title":"Error when installing pyodbc on opensuse","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":0},{"Question":"I'm writing an application that makes heavy use of geodjango (on PostGis) and spatial lookups. Distance queries on database side work great, but now I have to calculate distance between two points on python side of application (these points come from models obtained using separate queries). \nI can think of many ways that would calculate this distance, but I want to know do it in manner that is consistent with what the database will output.\nIs there any magic python function that calculates distance between two points given in which SRID they are measured? If not what other approach could you propose.","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1898,"Q_Id":11703407,"Users Score":0,"Answer":"Use the appropriate data connection to execute the SQL function that you're already using, then retrieve that... Keeps everything consistent.","Q_Score":2,"Tags":"python,django,gis,postgis,geodjango","A_Id":11703980,"CreationDate":"2012-07-28T17:57:00.000","Title":"How to calculate distance between points on python side of my application in way that is consistent in what database does","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am reading a bunch of strings from mysql database using python, and after some processing, writing them to a CSV file. However I see some totally junk characters appearing in the csv file. For example when I open the csv using gvim, I see characters like <92>,<89>, <94> etc. \nAny thoughts? I tried doing string.encode('utf-8') before writing to csv but that gave an error that UnicodeDecodeError: 'ascii' codec can't decode byte 0x93 in position 905: ordinal not in range(128)","AnswerCount":4,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1903,"Q_Id":11705114,"Users Score":0,"Answer":"Are all these \"junk\" characters in the range <80> to <9F>? If so, it's highly likely that they're Microsoft \"Smart Quotes\" (Windows-125x encodings). Someone wrote up the text in Word or Outlook, and copy\/pasted it into a Web application. Both Latin-1 and UTF-8 regard these characters as control characters, and the usual effect is that the text display gets cut off (Latin-1) or you see a ?-in-black-diamond-invalid-character (UTF-8).\nNote that Word and Outlook, and some other MS products, provide a UTF-8 version of the text for clipboard use. Instead of <80> to <9F> codes, Smart Quotes characters will be proper multibyte UTF-8 sequences. If your Web page is in UTF-8, you should normally get a proper UTF-8 character instead of the Smart Quote in Windows-125x encoding. Also note that this is not guaranteed behavior, but \"seems to work pretty consistently\". It all depends on a UTF-8 version of the text being available, and properly handled (i.e., you didn't paste into, say, gvim on the PC, and then copy\/paste into a Web text form). This may well also work for various PC applications, so long as they are looking for UTF-8-encoded text.","Q_Score":1,"Tags":"python,mysql,vim,encoding,smart-quotes","A_Id":18619898,"CreationDate":"2012-07-28T22:20:00.000","Title":"Junk characters (smart quotes, etc.) in output file","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have an items table that is related to an item_tiers table. The second table consists of inventory receipts for an item in the items table. There can be 0 or more records in the item_tiers table related to a single record in the items table. How can I, using query, get only records that have 1 or more records in item tiers....\nresults = session.query(Item).filter(???).join(ItemTier)\nWhere the filter piece, in pseudo code, would be something like ...\nif the item_tiers table has one or more records related to item.","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":144,"Q_Id":11746610,"Users Score":1,"Answer":"If there is a foreign key defined between tables, SA will figure the join condition for you, no need for additional filters.\n\nThere is, and i was really over thinking this. Thanks for the fast response. \u2013 Ominus","Q_Score":1,"Tags":"python,sqlalchemy","A_Id":11747157,"CreationDate":"2012-07-31T18:24:00.000","Title":"SQLAlchemy - Query show results where records exist in both table","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I currently run my own server \"in the cloud\" with PHP using mod_fastcgi and mod_vhost_alias.  My mod_vhost_alias config uses a VirtualDocumentRoot of \/var\/www\/%0\/htdocs so that I can serve any domain that routes to my server's IP address out of a directory with that name.\nI'd like to begin writing and serving some Python projects from my server, but I'm unsure how to configure things so that each site has access to the appropriate script processor.\nFor example, for my blog, dead-parrot.com, I'm running a PHP blog platform (Habari, not WordPress).  But I'd like to run an app I've written in Flask on not-dead-yet.com.  \nI would like to enable Python execution with as little disruption to my mod_vhost_alias configuration as possible, so that I can continue to host new domains on this server simply by adding an appropriate directory.  I'm willing to alter the directory structure, if necessary, but would prefer not to add additional, specific vhost config files for every new Python-running domain, since apart from being less convenient than my current setup with just PHP, it seems kind of hacky to have to name these earlier alphabetically to get Apache to pick them up before the single mod_vhost_alias vhost config.\nDo you know of a way that I can set this up to run Python and PHP side-by-side as conveniently  as I do just PHP?  Thanks!","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":6266,"Q_Id":11796126,"Users Score":0,"Answer":"Even I faced the same situation, and initially I was wondering in google but later realised and fixed it, I'm using EC2 service in aws with ubuntu and I created alias to php and python individually and now I can access both.","Q_Score":3,"Tags":"php,python,apache,mod-vhost-alias","A_Id":36646397,"CreationDate":"2012-08-03T12:53:00.000","Title":"Can I run PHP and Python on the same Apache server using mod_vhost_alias and mod_wsgi?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have really big collection of files, and my task is to open a couple of random files from this collection treat their content as a sets of integers and make an intersection of it. \nThis process is quite slow due to long times of reading files from disk into memory so I'm wondering whether this process of reading from file can be speed up by rewriting my program in some \"quick\" language. Currently I'm using python which could be inefficient for this kind of job.  (I could implement tests myself if I knew some other languages beside python and javascript...)\nAlso will putting all the date into database help? Files wont fit the RAM anyway so it will be reading from disk again only with database related overhead. \nThe content of files is the list of long integers. 90% of the files are quite small, less than a 10-20MB, but 10% left are around 100-200mb. As input a have filenames and I need read each of the files and output integers present in every file given. \nI've tried to put this data in mongodb but that was as slow as plain files based approach because I tried to use mongo index capabilities and mongo does not store indexes in RAM. \nNow I just cut the 10% of the biggest files and store rest in the redis, sometimes accessing those big files. This is, obviously temporary solution because my data grows and amount of RAM available does not.","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":213,"Q_Id":11805309,"Users Score":3,"Answer":"One thing you could try is calculating intersections of the files on a chunk-by-chunk basis (i.e., read x-bytes into memory from each, calculate their intersections, and continue, finally calculating the intersection of all intersections).\nOr, you might consider using some \"heavy-duty\" libraries to help you. Consider looking into PyTables (with HDF storage)\/using numpy for calculating intersections. The benefit there is that the HDF layer should help deal with not keeping the entire array structure in memory all at once---though I haven't tried any of these tools before, it seems like they offer what you need.","Q_Score":4,"Tags":"python,file,file-io,io,filesystems","A_Id":11805422,"CreationDate":"2012-08-04T01:52:00.000","Title":"Is speed of file opening\/reading language dependent?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have some SQL Server tables that contain Image data types.\nI want to make it somehow usable in PostgreSQL. I'm a python programmer, so I have a lot of learn about this topic. Help?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":297,"Q_Id":11805709,"Users Score":0,"Answer":"What you need to understand first is that the interfaces at the db level are likely to be different.  Your best option is to write an abstraction layer for the blobs (and maybe publish it open source for the dbs you want to support).\nOn the PostgreSQL side you need to figure out whether you want to bo with bytea or lob.  These are very different and have different features and limitations.  If you are enterprising you might build in at least support in the spec for selecting them.  In general bytea is better for smaller files while lob has more management overhead but it can both support larger files and supports chunking, seeking etc.","Q_Score":0,"Tags":"python,sql-server,postgresql,blob","A_Id":15846639,"CreationDate":"2012-08-04T03:36:00.000","Title":"How can I select and insert BLOB between different databases using python?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"In the High-Replication Datastore (I'm using NDB), the consistency is eventual. In order to get a guaranteed complete set, ancestor queries can be used. Ancestor queries also provide a great way to get all the \"children\" of a particular ancestor with kindless queries. In short, being able to leverage the ancestor model is hugely useful in GAE.\nThe problem I seem to have is rather simplistic. Let's say I have a contact record and a message record. A given contact record is being treated as the ancestor for each message. However, it is possible that two contacts are created for the same person (user error, different data points, whatever). This situation produces two contact records, which have messages related to them.\nI need to be able to \"merge\" the two records, and bring put all the messages into one big pile. Ideally, I'd be able to modify ancestor for one of the record's children.\nThe only way I can think of doing this, is to create a mapping and make my app check to see if record has been merged. If it has, look at the mappings to find one or more related records, and perform queries against those. This seems hugely inefficient. Is there more of \"by the book\" way of handling this use case?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1422,"Q_Id":11854137,"Users Score":9,"Answer":"The only way to change the ancestor of an entity is to delete the old one and create a new one with a new key. This must be done for all child (and grand child, etc) entities in the ancestor path. If this isn't possible, then your listed solution works.\nThis is required because the ancestor path of an entity is part of its unique key. Parents of entities (i.e., entities in the ancestor path) need not exist, so changing a parent's key will leave the children in the datastore with no parent.","Q_Score":5,"Tags":"python,google-app-engine,google-cloud-datastore","A_Id":11855209,"CreationDate":"2012-08-07T21:04:00.000","Title":"How to change ancestor of an NDB record?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I am looking for a pure-python SQL library that would give access to both MySQL and PostgreSQL.\nThe only requirement is to run on Python 2.5+ and be pure-python, so it can be included with the script and still run on most platforms (no-install).\nIn fact I am looking for a simple solution that would allow me to write SQL and export the results as CSV files.","AnswerCount":3,"Available Count":1,"Score":0.0665680765,"is_accepted":false,"ViewCount":2182,"Q_Id":11868582,"Users Score":1,"Answer":"Use SQL-Alchemy. It will work with most database types, and certainly does work with postgres and MySQL.","Q_Score":3,"Tags":"python,mysql,postgresql","A_Id":11870176,"CreationDate":"2012-08-08T16:03:00.000","Title":"Pure python SQL solution that works with PostgreSQL and MySQL?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am relatively new to Django and one thing that has been on my mind is changing the database that will be used when running the project.\nBy default, the DATABASES 'default' is used to run my test project. But in the future, I want to be able to define a 'production' DATABASES configuration and have it use that instead.\nIn a production environment, I won't be able to \"manage.py runserver\" so I can't really set the settings.\nI read a little bit about \"routing\" the database to use another database, but is there an easier way so that I won't need to create a new router every time I have another database I want to use (e.g. I can have test database, production database, and development database)?","AnswerCount":3,"Available Count":1,"Score":0.0665680765,"is_accepted":false,"ViewCount":304,"Q_Id":11878454,"Users Score":1,"Answer":"You can just use a different settings.py in your production environment.\nOr - which is a bit cleaner - you might want to create a file settings_local.py next to settings.py where you define a couple of settings that are specific for the current machine (like DEBUG, DATABASES, MEDIA_ROOT etc.) and do a from settings_local import * at the beginning of your generic settings.py file. Of course settings.py must not overwrite these imported settings.","Q_Score":0,"Tags":"python,database,django,configuration","A_Id":11878547,"CreationDate":"2012-08-09T07:14:00.000","Title":"How do I make Django use a different database besides the 'default'?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm building a web app in Python (using Flask). I do not intend to use SQLAlchemy or similar ORM system, rather I'm going to use Psycopg2 directly.\nShould I open a new database connection (and subsequently close it) for each new request? Or should I use something to pool these connections?","AnswerCount":5,"Available Count":3,"Score":0.0399786803,"is_accepted":false,"ViewCount":9082,"Q_Id":11889104,"Users Score":1,"Answer":"I think connection pooling is the best thing to do if this application is to serve multiple clients and concurrently.","Q_Score":8,"Tags":"python,postgresql,web-applications,flask,psycopg2","A_Id":11889137,"CreationDate":"2012-08-09T17:48:00.000","Title":"Should PostgreSQL connections be pooled in a Python web app, or create a new connection per request?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm building a web app in Python (using Flask). I do not intend to use SQLAlchemy or similar ORM system, rather I'm going to use Psycopg2 directly.\nShould I open a new database connection (and subsequently close it) for each new request? Or should I use something to pool these connections?","AnswerCount":5,"Available Count":3,"Score":0.1194272985,"is_accepted":false,"ViewCount":9082,"Q_Id":11889104,"Users Score":3,"Answer":"The answer depends on how many such requests will happen and how many concurrently in your web app ? Connection pooling is usually a better idea if you expect your web app to be busy with 100s or even 1000s of user concurrently logged in. If you are only doing this as a side project and expect less than few hundred users, you can probably get away without pooling.","Q_Score":8,"Tags":"python,postgresql,web-applications,flask,psycopg2","A_Id":11889659,"CreationDate":"2012-08-09T17:48:00.000","Title":"Should PostgreSQL connections be pooled in a Python web app, or create a new connection per request?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm building a web app in Python (using Flask). I do not intend to use SQLAlchemy or similar ORM system, rather I'm going to use Psycopg2 directly.\nShould I open a new database connection (and subsequently close it) for each new request? Or should I use something to pool these connections?","AnswerCount":5,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":9082,"Q_Id":11889104,"Users Score":0,"Answer":"Pooling seems to be totally impossible in context of Flask, FastAPI and everything relying on wsgi\/asgi dedicated servers with multiple workers.\nReason for this behaviour is simple: you have no control about the pooling and master thread\/process.\nA pooling instance is only usable for a single thread serving a set of clients - so for just one worker. Any other worker will get it's own pool and therefore there cannot be any sharing of established connections.\nLogically it's also impossible, because you cannot share these object states across threads\/processes in multi core env with python (2.x - 3.8).","Q_Score":8,"Tags":"python,postgresql,web-applications,flask,psycopg2","A_Id":61078209,"CreationDate":"2012-08-09T17:48:00.000","Title":"Should PostgreSQL connections be pooled in a Python web app, or create a new connection per request?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I've searched and I can't seem to find anything.\nHere is the situation:\n\nt1 = table 1\nt2 = table 2\nv = view of table 1 and table 2 joined\n\n1.) User 1 is logged into database. Does SELECT * FROM v;\n2.) User 2 is logged into same database and does INSERT INTO t1 VALUES(1, 2, 3);\n3.) User 1 does another SELECT * FROM v; User 1 can't see the inserted row from User 2 until logging out and logging back in.\nSeems like views don't get sync'd across \"sessions\"? How can I make it so User 1 can see the INSERT?\nFYI I'm using python and mysqldb.","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":542,"Q_Id":11979276,"Users Score":1,"Answer":"Instead of logging out and logging back in, user 2 could simply commit their transaction. \nMySQL InnoDB tables use transactions, requiring a BEGIN before one or more SQL statements, and either COMMIT or ROLLBACK afterwards, resulting in all your updates\/inserts\/deletes either happening or not. But there's a \"feature\" that results in an automatic BEGIN if not explicitly issued, and an automatic COMMIT when the connection is closed. This is why you see the changes after the other user closes the connection. \nYou should really get into the habit of explicitly beginning and committing your transactions, but there's also another way: set connection.autocommit = True, which will result in every sql update\/insert\/delete being wrapped in its own implicit transaction, resulting in the behavior you originally expected.\nDon't take what I said above to be entirely factually correct, but it suffices to explain the fundamentals of what's going on and how to control it.","Q_Score":2,"Tags":"python,mysql,mysql-python","A_Id":11979334,"CreationDate":"2012-08-16T00:51:00.000","Title":"MySQL view doesn't update when underlaying table changes across different users","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am fairly new to databases and have just figured out how to use MongoDB in python2.7 on Ubuntu 12.04. An application I'm writing uses multiple python modules (imported into a main module) that connect to the database. Basically, each module starts by opening a connection to the DB, a connection which is then used for various operations.\nHowever, when the program exits, the main module is the only one that 'knows' about the exiting, and closes its connection to MongoDB. The other modules do not know this and have no chance of closing their connections. Since I have little experience with databases, I wonder if there are any problems leaving connections open when exiting.\nShould I:\n\nLeave it like this?\nInstead open the connection before and close it after each operation?\nChange my application structure completely?\nSolve this in a different way?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1207,"Q_Id":11989408,"Users Score":3,"Answer":"You can use one pymongo connection across different modules. You can open it in a separate module and import it to other modules on demand. After program finished working, you are able to close it. This will be the best option.\nAbout other questions:\n\nYou can leave like this (all connections will be closed when script finishes execution), but leaving something unclosed is a bad form.\nYou can open\/close connection for each operation (but establishing connection is a time-expensive operation.\nThat what I'd advice you (see this answer's first paragraph)\nI think this point can be merged with 3.","Q_Score":3,"Tags":"python,mongodb,pymongo","A_Id":11989459,"CreationDate":"2012-08-16T14:29:00.000","Title":"When to disconnect from mongodb","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Could any one shed some light on how to migrate my MongoDB to PostgreSQL? What tools do I need, what about handling primary keys and foreign key relationships, etc?\nI had MongoDB set up with Django, but would like to convert it back to PostgreSQL.","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":1475,"Q_Id":12034390,"Users Score":1,"Answer":"Whether the migration is easy or hard depends on a very large number of things  including how many different versions of data structures you have to accommodate.  In general you will find it a lot easier if you approach this in stages:\n\nEnsure that all the Mongo data is consistent in structure with your RDBMS model and that the data structure versions are all the same.\nMove your data.  Expect that problems will be found and you will have to go back to step 1.\n\nThe primary problems you can expect are data validation problems because you are moving from a less structured data platform to a more structured one.\nDepending on what you are doing regarding MapReduce you may have some work there as well.","Q_Score":2,"Tags":"python,django,mongodb,database-migration,django-postgresql","A_Id":15858338,"CreationDate":"2012-08-20T08:25:00.000","Title":"From MongoDB to PostgreSQL - Django","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have two programs: the first only write to sqlite db, and the second only read. May I be sure that there are never be some errors? Or how to avoid from it (in python)?","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":383,"Q_Id":12046760,"Users Score":1,"Answer":"generally, it is safe if there is only one program writing the sqlite db at one time.\n(If not, it will raise exception like \"database is locked.\" while two write operations want to write at the same time.)\nBy the way, it is no way to guarantee the program will never have errors. using Try ... catch to handle exception will make the program much safer.","Q_Score":3,"Tags":"python,concurrency,sqlite","A_Id":12047988,"CreationDate":"2012-08-20T23:51:00.000","Title":"sqlite3: safe multitask read & write - how to?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"So I'm using xlrd to pull data from an Excel sheet. I get it open and it pulls the data perfectly fine.\nMy problem is the sheet updates automatically with data from another program. It is updating stock information using an rtd pull.\nHas anyone ever figured out any way to pull data from a sheet like this that is up-to-date?","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":364,"Q_Id":12049067,"Users Score":1,"Answer":"Since all that xlrd can do is read a file, I'm assuming that the excel file is saved after each update.\nIf so, use os.stat() on the file before reading it with xlrd and save the results (or at least those of os.stat().st_mtime). Then periodically use os.stat() again, and check if the file modification time (os.stat().st_mtime) has changed, indicating that the file has been changed. If so, re-read the file with xlrd.","Q_Score":0,"Tags":"python,excel","A_Id":12049844,"CreationDate":"2012-08-21T05:48:00.000","Title":"Pulling from an auto-updating Excel sheet","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am currently sitting in front of a more specific problem which has to do with fail-over support \/ redundancy for a specific web site which will be hosted over @ WebFaction. Unfortunately replication at the DB level is not an option as I would have to install my own local PostgreSQL instances for every account and I am worried about performance amongst other things. So I am thinking about using Django's multi-db feature and routing all writes to all (shared) databases and the balance the reads to the nearest db.\nMy problem is now that all docs I read seem to indicate that this would most likely not be possible. To be more precise what I would need:\n\nroute all writes to a specific set of dbs (same type, version, ...)\nif one write fails, all the others will be rolled back (transactions)\nroute all reads to the nearest db (could be statically configured)\n\nIs this currently possible with Django's multi-db support?\nThanks a lot in advance for any help\/hints...","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":345,"Q_Id":12070031,"Users Score":1,"Answer":"I was looking for something similar. What I found is: \n1) Try something like Xeround cloud DB - it's built on MySQL and is compatible but doesn't support savepoints. You have to disable this in (a custom) DB engine. The good thing is that they replicate at the DB level and provide automatic scalability and failover. Your app works as if there's a single DB. They are having some connectivity issues at the moment though which are blocking my migration.\n2) django-synchro package - looks promissing for replications at the app layer but I have some concerns about it. It doesn't work on objects.update() which I use a lot in my code.","Q_Score":1,"Tags":"python,django,redundancy,webfaction,django-orm","A_Id":12934130,"CreationDate":"2012-08-22T09:24:00.000","Title":"Django multi-db: Route all writes to multiple databases","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I've been learning Python through Udacity, Code Academy and Google University. I'm now feeling confident enough to start learning Django. My question is should I learn Django on an SQL database - either SQLite or MySQL; or should I learn Django on a NoSQL database such as Mongo?\nI've read all about both but there's a lot I don't understand. Mongo sounds better\/easier but at the same time it sounds better\/easier for those that already know Relational Databases very well and are looking for something more agile.","AnswerCount":4,"Available Count":2,"Score":0.049958375,"is_accepted":false,"ViewCount":5188,"Q_Id":12078928,"Users Score":1,"Answer":"Postgres is a great database for Django in production. sqlite is amazing to develop with. You will be doing a lot of work to try to not use a RDBMS on your first Django site.\nOne of the greatest strengths of Django is the smooth full-stack integration, great docs, contrib apps, app ecosystem. Choosing Mongo, you lose a lot of this. GeoDjango also assumes SQL and really loves postgres\/postgis above others - and GeoDjango is really awesome.\nIf you want to use Mongo, I might recommend that you start with something like bottle, flask, tornado, cyclone, or other that are less about the full-stack integration and less assuming about you using a certain ORM. The Django tutorial, for instance, assumes that you are using the ORM with a SQL DB.","Q_Score":3,"Tags":"python,sql,django,nosql","A_Id":12078992,"CreationDate":"2012-08-22T18:07:00.000","Title":"First time Django database SQL or NoSQL?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I've been learning Python through Udacity, Code Academy and Google University. I'm now feeling confident enough to start learning Django. My question is should I learn Django on an SQL database - either SQLite or MySQL; or should I learn Django on a NoSQL database such as Mongo?\nI've read all about both but there's a lot I don't understand. Mongo sounds better\/easier but at the same time it sounds better\/easier for those that already know Relational Databases very well and are looking for something more agile.","AnswerCount":4,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":5188,"Q_Id":12078928,"Users Score":0,"Answer":"sqlite is the simplest to start with. If you already know SQL toss a coin to choose between MySQL and Postgres for your first project!","Q_Score":3,"Tags":"python,sql,django,nosql","A_Id":12079233,"CreationDate":"2012-08-22T18:07:00.000","Title":"First time Django database SQL or NoSQL?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I need python and php support. I am currently using mongodb and it is great for my data (test results), but I need to store results of a different type of test which are over 32 MB and exceed mongo limit of 16 MB.\nCurrently each test is a big python dictionary and I retrieve and represent them with php.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":128,"Q_Id":12090204,"Users Score":0,"Answer":"You can store up to 16MB of data per MongoDB BSON document (e.g. using the pymongo Binary datatype). For arbitrary large data you want to use GridFS which basically stored your data as  chunks + extra metadata. When you using MongoDB with its replication features (replica sets) you will have kind of a distributed binary store (don't mix this up with a distributed filesystem (no integration with local filesystem).","Q_Score":2,"Tags":"php,python,mongodb,size,limit","A_Id":12090898,"CreationDate":"2012-08-23T11:07:00.000","Title":"no-sql database for document sizes over 32 MB?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am using MySQLdb. I am developing a simple GUI application using Rpy2. What my program does?\n- User can input the static data and mathematical operations will be computed using those data.\n- Another thing where I am lost is, user will give the location of their database and the program will computer maths using the data from the remote database.\nI have accomplished the result using the localhost. \nHow can I do it from the remote database? Any idea? \nThanx in advance!","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":187,"Q_Id":12091413,"Users Score":0,"Answer":"When you establish the MySQL connection, use the remote machines IP address \/ hostname and corresponding credentials (username, password).","Q_Score":0,"Tags":"python,database","A_Id":12091455,"CreationDate":"2012-08-23T12:17:00.000","Title":"How to take extract data from the remote database in Python?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I use\n\npython 2.7 \npyodbc module\ngoogle app engine 1.7.1\n\nI can use pydobc with python but the Google App Engine can't load the module. I get a no module named pydobc error.\nHow can I fix this error or how can use MS-SQL database with my local Google App Engine.","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":2793,"Q_Id":12108816,"Users Score":0,"Answer":"You could, at least in theory, replicate your data from the MS-SQL to the Google Cloud SQL database. It is possible create triggers in the MS-SQL database so that every transaction is reflected on your App Engine application via a REST API you will have to build.","Q_Score":3,"Tags":"python,sql-server,google-app-engine","A_Id":12116542,"CreationDate":"2012-08-24T11:45:00.000","Title":"How can use Google App Engine with MS-SQL","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I am trying to copy and use the example 'User Authentication with PostgreSQL database' from the web.py cookbook. I can not figure out why I am getting the following errors.\n\n at \/login\n'ThreadedDict' object has no attribute 'login'\n at \/login\n'ThreadedDict' object has no attribute 'privilege'\n\nHere is the error output to the terminal for the second error. (the first is almost identical)\n\nTraceback (most recent call last):\n  File \"\/usr\/local\/lib\/python2.7\/dist-packages\/web.py-0.37-py2.7.egg\/web\/application.py\", line 239, in process\n    return self.handle()\n  File \"\/usr\/local\/lib\/python2.7\/dist-packages\/web.py-0.37-py2.7.egg\/web\/application.py\", line 230, in handle\n    return self._delegate(fn, self.fvars, args)\n  File \"\/usr\/local\/lib\/python2.7\/dist-packages\/web.py-0.37-py2.7.egg\/web\/application.py\", line 420, in _delegate\n    return handle_class(cls)\n  File \"\/usr\/local\/lib\/python2.7\/dist-packages\/web.py-0.37-py2.7.egg\/web\/application.py\", line 396, in handle_class\n    return tocall(*args)\n  File \"\/home\/erik\/Dropbox\/Python\/Web.py\/Code.py\", line 44, in GET\n    render = create_render(session.privilege)\n  File \"\/usr\/local\/lib\/python2.7\/dist-packages\/web.py-0.37-py2.7.egg\/web\/session.py\", line 71, in __getattr__\n    return getattr(self._data, name)\nAttributeError: 'ThreadedDict' object has no attribute 'privilege'\n\n127.0.0.1:36420 - - [25\/Aug\/2012 01:12:38] \"HTTP\/1.1 GET \/login\" - 500 Internal Server Error\n\n\nHere is my code.py file. Pretty much cut-n-paste from the cookbook. I tried putting all of the class and def on top of the main code. I have also tried launching python with sudo as mentioned in another post.\n\nimport web\n\nclass index:\n    def GET(self):\n        todos = db.select('todo')\n        return render.index(todos)\n\nclass add:\n    def POST(self):\n        i = web.input()\n        n = db.insert('todo', title=i.title)\n        raise web.seeother('\/')\n\ndef logged():\n    return False  #I added this to test error #1, Now I get error #2\n    #if session.login==1:\n    #    return True\n    #else:\n    #    return False\n\ndef create_render(privilege):\n    if logged():\n        if privilege == 0:\n            render = web.template.render('templates\/reader')\n        elif privilege == 1:\n            render = web.template.render('templates\/user')\n        elif privilege == 2:\n            render = web.template.render('templates\/admin')\n        else:\n            render = web.template.render('templates\/communs')\n    else:\n        render = web.template.render('templates\/communs')\n    return render\n\n\n\nclass Login:\n\n    def GET(self):\n        if logged():\n            render = create_render(session.privilege)\n            return '%s' % render.login_double()\n        else:\n            # This is where error #2 is\n            render = create_render(session.privilege)\n            return '%s' % render.login()\n\n    def POST(self):\n        name, passwd = web.input().name, web.input().passwd\n        ident = db.select('users', where='name=$name', vars=locals())[0]\n        try:\n            if hashlib.sha1(\"sAlT754-\"+passwd).hexdigest() == ident['pass']:\n                session.login = 1\n                session.privilege = ident['privilege']\n                render = create_render(session.privilege)\n                return render.login_ok()\n            else:\n                session.login = 0\n                session.privilege = 0\n                render = create_render(session.privilege)\n                return render.login_error()\n        except:\n            session.login = 0\n            session.privilege = 0\n            render = create_render(session.privilege)\n            return render.login_error()\n\n\nclass Reset:\n\n    def GET(self):\n        session.login = 0\n        session.kill()\n        render = create_render(session.privilege)\n        return render.logout()\n\n\n\n\n#web.config.debug = False\n\nrender = web.template.render('templates\/', base='layout')\nurls = (\n    '\/', 'index',\n    '\/add', 'add',\n    '\/login', 'Login',\n    '\/reset', 'Reset'\n    )\n\napp = web.application(urls, globals())\ndb = web.database(dbn='postgres', user='hdsfgsdfgsd', pw='dfgsdfgsdfg', db='postgres', host='fdfgdfgd.com')\n\nstore = web.session.DiskStore('sessions')\n\n# Too me, it seems this is being ignored, at least the 'initializer' part\nsession = web.session.Session(app, store, initializer={'login': 0, 'privilege': 0})\n\n\n\nif __name__ == \"__main__\": app.run()","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":2157,"Q_Id":12120539,"Users Score":0,"Answer":"Okay, I was able to figure out what I did wrong. Total newbie stuff and all part of the learning process. This code now works, well mostly. The part that I was stuck on is now working. See my comments in the code\nThanks\n\nimport web\n\nweb.config.debug = False\n\nrender = web.template.render('templates\/', base='layout')\nurls = (\n    '\/', 'index',\n    '\/add', 'add',\n    '\/login', 'Login',\n    '\/reset', 'Reset'\n    )\n\napp = web.application(urls, globals())\ndb = web.database(blah, blah, blah)\n\nstore = web.session.DiskStore('sessions')\nsession = web.session.Session(app, store, initializer={'login': 0, 'privilege': 0})\n\n\nclass index:\n    def GET(self):\n        todos = db.select('todo')\n        return render.index(todos)\n\nclass add:\n    def POST(self):\n        i = web.input()\n        n = db.insert('todo', title=i.title)\n        raise web.seeother('\/')\n\ndef logged():\n    if session.get('login', False):\n        return True\n    else:\n        return False\n\ndef create_render(privilege):\n    if logged():\n        if privilege == 0:\n            render = web.template.render('templates\/reader')\n        elif privilege == 1:\n            render = web.template.render('templates\/user')\n        elif privilege == 2:\n            render = web.template.render('templates\/admin')\n        else:\n            render = web.template.render('templates\/communs')\n    else:\n                ## This line is key, i do not have a communs folder, thus returning an unusable object\n        #render = web.template.render('templates\/communs')  #Original code from example\n\n        render = web.template.render('templates\/', base='layout')\n    return render\n\n\n\nclass Login:\n\n    def GET(self):\n        if logged():\n                        ## Using session.get('something') instead of session.something does not blow up when it does not exit \n            render = create_render(session.get('privilege'))\n            return '%s' % render.login_double()\n        else:\n            render = create_render(session.get('privilege'))\n            return '%s' % render.login()\n\n    def POST(self):\n        name, passwd = web.input().name, web.input().passwd\n        ident = db.select('users', where='name=$name', vars=locals())[0]\n        try:\n            if hashlib.sha1(\"sAlT754-\"+passwd).hexdigest() == ident['pass']:\n                session.login = 1\n                session.privilege = ident['privilege']\n                render = create_render(session.get('privilege'))\n                return render.login_ok()\n            else:\n                session.login = 0\n                session.privilege = 0\n                render = create_render(session.get('privilege'))\n                return render.login_error()\n        except:\n            session.login = 0\n            session.privilege = 0\n            render = create_render(session.get('privilege'))\n            return render.login_error()\n\n\nclass Reset:\n\n    def GET(self):\n        session.login = 0\n        session.kill()\n        render = create_render(session.get('privilege'))\n        return render.logout()\n\n\nif __name__ == \"__main__\": app.run()","Q_Score":0,"Tags":"python,session,login,web.py","A_Id":12137859,"CreationDate":"2012-08-25T08:47:00.000","Title":"web.py User Authentication with PostgreSQL database example","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am using PyMongo and gevent together, from a Django application. In production, it is hosted on Gunicorn.\nI am creating a single Connection object at startup of my application. I have some background task running continuously and performing a database operation every few seconds.\nThe application also serves HTTP requests as any Django app.\nThe problem I have is the following. It only happens in production, I have not been able to reproduce it on my dev environment. When I let the application idle for a little while (although the background task is still running), on the first HTTP request (actually the first few), the first \"find\" operation I perform never completes. The greenlet actually never resumes. This causes the first few HTTP requests to time-out.\nHow can I fix that? Is that a bug in gevent and\/or PyMongo?","AnswerCount":1,"Available Count":1,"Score":0.6640367703,"is_accepted":false,"ViewCount":862,"Q_Id":12157350,"Users Score":4,"Answer":"I found what the problem is. By default PyMongo has no network timeout defined on the connections, so what was happening is that the connections in the pool got disconnected (because they aren't used for a while). Then when I try to reuse a connection and perform a \"find\", it takes a very long time for the connection be detected as dead (something like 15 minutes). When the connection is detected as dead, the \"find\" call finally throws an AutoReconnectError, and a new connection is spawned up to replace to stale one.\nThe solution is to set a small network timeout (15 seconds), so that the call to \"find\" blocks the greenlet for 15 seconds, raises an AutoReconnectError, and when the \"find\" is retried, it gets a new connection, and the operation succeeds.","Q_Score":3,"Tags":"python,mongodb,pymongo,gevent,greenlets","A_Id":12163744,"CreationDate":"2012-08-28T10:26:00.000","Title":"Deadlock with PyMongo and gevent","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm trying to install mysql-python package on a machine with Centos 6.2 with Percona Server.\nHowever I'm running into EnvironmentError: mysql_config not found error. \nI've carefully searched information regarding this error but all I found is that one needs to add path to mysql_config binary to the PATH system variable.\nBut it looks like, with my percona installation, a don't have mysql_config file at all\nfind \/ -type f -name mysql_config returns nothing.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1025,"Q_Id":12202303,"Users Score":0,"Answer":"mysql_config is a part of mysql-devel package.","Q_Score":1,"Tags":"python,percona","A_Id":12202936,"CreationDate":"2012-08-30T17:27:00.000","Title":"mysql-python with Percona Server installation","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a collection that is potentially going to be very large. Now I know MongoDB doesn't really have a problem with this, but I don't really know how to go about designing a schema that  can handle a very large dataset comfortably. So I'm going to give an outline of the problem.\nWe are collecting large amounts of data for our customers. Basically, when we gather this data it is represented as a 3-tuple, lets say (a, b, c), where b and c are members of sets B and C respectively. In this particular case we know that the B and C sets will not grow very much over time. For our current customers we are talking about ~200,000 members. However, the A set is the one that keeps growing over time. Currently we are at about ~2,000,000 members per customer, but this is going to grow (possibly rapidly.) Also, there are 1->n relations between b->a and c->a.\nThe workload on this data set is basically split up into 3 use cases. The collections will be periodically updated, where A will get the most writes, and B and C will get some, but not many. The second use case is random access into B, then aggregating over some number of documents in C that pertain to b \\in B. And the last usecase is basically streaming a large subset from A and B to generate some new data.\nThe problem that we are facing is that the indexes are getting quite big. Currently we have a test setup with about 8 small customers, the total dataset is about 15GB in size at the moment, and indexes are running at about 3GB to 4GB. The problem here is that we don't really have any hot zones in our dataset. It's basically going to get an evenly distributed load amongst all documents.\nBasically we've come up with 2 options to do this. The one that I described above, where all data for all customers is piled into one collection. This means we'd have to create an index om some field that links the documents in that collection to a particular customer.\nThe other options is to throw all b's and c's together (these sets are relatively small) but divide up the C collection, one per customer. I can imangine this last solution being a bit harder to manage, but since we rarely access data for multiple customers at the same time, it would prevent memory problems. MongoDB would be able to load the customers index into memory and just run from there.\nWhat are your thoughts on this?\nP.S.: I hope this wasn't too vague, if anything is unclear I'll go into some more details.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":239,"Q_Id":12210307,"Users Score":1,"Answer":"It sounds like the larger set (A if I followed along correctly), could reasonably be put into its own database.  I say database rather than collection, because now that 2.2 is released you would want to minimize lock contention between the busier database and the others, and to do that a separate database would be best (2.2 introduced database level locking).  That is looking at this from a single replica set model, of course.\nAlso the index sizes sound a bit out of proportion to your data size - are you sure they are all necessary?  Pruning unneeded indexes, combining and using compound indexes may well significantly reduce the pain you are hitting in terms of index growth (it would potentially make updates and inserts more efficient too).  This really does need specifics and probably belongs in another question, or possibly a thread in the mongodb-user group so multiple eyes can take a look and make suggestions.\nIf we look at it with the possibility of sharding thrown in, then the truly important piece is to pick a shard key that allows you to make sure locality is preserved on the shards for the pieces you will frequently need to access together.  That would lend itself more toward a single sharded collection (preserving locality across multiple related sharded collections is going to be very tricky unless you manually split and balance the chunks in some way).  Sharding gives you the ability to scale out horizontally as your indexes hit the single instance limit etc. but it is going to make the shard key decision very important.\nAgain, specifics for picking that shard key are beyond the scope of this more general discussion, similar to the potential index review I mentioned above.","Q_Score":2,"Tags":"python,mongodb","A_Id":12216914,"CreationDate":"2012-08-31T06:56:00.000","Title":"Split large collection into smaller ones?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Are there any generally accepted practices to get around this? Specifically, for user-submitted images uploaded to a web service. My application is running in Python.\nSome hacked solutions that came to mind:\n\nDisplay the uploaded image from a local directory until the S3 image is ready, then \"hand it off\" and update the database to reflect the change.\nDisplay a \"waiting\" progress indicator as a background gif and the image will just appear when it's ready (w\/ JavaScript)","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":323,"Q_Id":12241945,"Users Score":1,"Answer":"I'd save time and not do anything.  The wait times are pretty fast.  \nIf you wanted to stall the end-user, you could just show a 'success' page without the image.  If the image isn't available, most regular users will just hit reload.\nIf you really felt like you had to... I'd probably go with a javascript solution like this:\n\nhave a 'timestamp uploaded' column in your data store\nif the upload time is under 1 minute, instead of rendering an img=src tag... render some javascript that polls the s3 bucket in 15s intervals\n\nAgain, chances are most users will never experience this - and if they do, they won't really care.  The UX expectations of user generated content are pretty low ( just look at Facebook ); if this is an admin backend for an 'enterprise' service that would make workflow better, you may want to invest time on the 'optimal' solution.  For a public facing website though, i'd just forget about it.","Q_Score":0,"Tags":"python,amazon-s3,amazon-web-services","A_Id":12242133,"CreationDate":"2012-09-03T04:22:00.000","Title":"What are some ways to work with Amazon S3 not offering read-after-write consistency in US Standard?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":1,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm creating a game mod for Counter-Strike in python, and it's basically all done. The only thing left is to code a REAL database, and I don't have any experience on sqlite, so I need quite a lot of help.\nI have a Player class with attribute self.steamid, which is unique for every Counter-Strike player (received from the game engine), and self.entity, which holds in an \"Entity\" for player, and Entity-class has lots and lots of more attributes, such as level, name and loads of methods. And Entity is a self-made Python class).\nWhat would be the best way to implement a database, first of all, how can I save instances of Player with an other instance of Entity as it's attribute into a database, powerfully?\nAlso, I will need to get that users data every time he connects to the game server, (I have player_connect event), so how would I receive the data back?\nAll the tutorials I found only taught about saving strings or integers, but nothing about whole instances. Will I have to save every attribute on all instances (Entity instance has few more instances as it's attributes, and all of them have huge amounts of attributes...), or is there a faster, easier way?\nAlso, it's going to be a locally saved database, so I can't really use any other languages than sql.","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":356,"Q_Id":12266016,"Users Score":0,"Answer":"You need an ORM. Either you roll your own (which I never suggest), or you use one that exists already. Probably the two most popular in Python are sqlalchemy, and the ORM bundled with Django.","Q_Score":1,"Tags":"python,database,sqlite,instance","A_Id":12268131,"CreationDate":"2012-09-04T14:47:00.000","Title":"Python sqlite3, saving instance of a class with an other instance as it's attribute?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a few a few model classes such as a user class which is passed a dictionary, and wraps it providing various methods, some of which communicate with the database when a value needs to be changed. The dictionary itself is made from an sqlalchemy RowProxy, so all its keys are actually attribute names taken directly from the sql user table. (attributes include user_id, username, email, passwd, etc)\nIf a user is logged in, should I simply save this dictionary to a redis key value store, and simply call a new user object when needed and pass it this dictionary from redis(which should be faster than only saving a user id in a session and loading the values again from the db based on that user_id)? \nOr should I somehow serialize the entire object and save it in redis? I'd appreciate any alternate methods of managing model and session objects that any of you feel would be better as well.\nIn case anyone is wondering I'm only using the sqlalchemy expression language, and not the orm. I'm using the model classes as interfaces, and coding against those.","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":241,"Q_Id":12292277,"Users Score":4,"Answer":"Unless you're being really careful, serializing the entire object into redis is going to cause problems. You're effectively treating it like a cache, so you have to be careful that those values are expired if the user changes something about themselves. You also have to make sure that all of the values are serializable (likely via pickle). You didn't specify whether this is a premature optimization so I'm going to say that it probably is and recommend that you just track the user id and reload his information when you need it from your database.","Q_Score":1,"Tags":"python,session,sqlalchemy,session-state,pyramid","A_Id":12320928,"CreationDate":"2012-09-06T02:42:00.000","Title":"How do I go about storing session objects?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Hi I intend to draw a chart with data in an xlsx file.\nIn order to keep the style, I HAVE TO draw it within excel.\nI found a package named win32com, which can give a support to manipulate excel file with python on win32 platform, but I don't know where is the doc.....\nAnother similar question is how to change the style of cells, such as font, back-color ?\nSo maybe all I wanna know is the doc, you know how to fish is more useful than fishes.... and an example is better.","AnswerCount":4,"Available Count":1,"Score":0.049958375,"is_accepted":false,"ViewCount":2868,"Q_Id":12296563,"Users Score":1,"Answer":"Documentation for win32com is next to non-existent as far I know. However, I use the following method to understand the commands.\n\nMS-Excel\nIn Excel, record a macro of whatever action you intend to, say plotting a chart. Then go to the Macro menu and use View Macro to get the underlying commands. More often than not, the commands used would guide you to the corresponding commands in python that you need to use.\n\nPythonwin\nYou can use pythonwin to browse the underlying win32com defined objects (in your case Microsoft Excel Objects). In pythonwin (which can be found at \\Lib\\site-packages\\pythonwin\\ in your python installation), go to Tools -> COM Makepy Utility, select your required Library (in this case, Microsoft Excel 14.0 Object Library) and press Ok. Then when the process is complete, go to Tools -> COM Browser and open the required library under Registered Libraries. Note the ID no. as this would correspond to the source file. You can browse the various components of the library in the COM Browser.\n\nSource\nGo to \\Lib\\site-packages\\win32com\\ in your python installation folder. Run makepy.py and choose the required library. After this, the source file of the library can be found at \\Lib\\site-packages\\win32com\\gen_py . It is one of those files with the wacky name. The name corresponds to that found in Pythonwin. Open the file, and search for the commands you saw in the Excel Macro. (#2 and #3 maybe redundant, I am not sure)","Q_Score":0,"Tags":"python,excel,win32com","A_Id":13086152,"CreationDate":"2012-09-06T09:03:00.000","Title":"How to draw a chart with excel using python?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I use Python with SQLAlchemy for some relational tables. For the storage of some larger data-structures I use Cassandra. I'd prefer to use just one technology (cassandra) instead of two (cassandra and PostgreSQL). Is it possible to store the relational data in cassandra as well?","AnswerCount":3,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":8349,"Q_Id":12297847,"Users Score":3,"Answer":"playOrm supports JOIN on noSQL so that you CAN put relational data into noSQL but it is currently in java.  We have been thinking of exposing a S-SQL language from a server for programs like yours.  Would that be  of interest to you?\nThe S-SQL would look like this(if you don't use partitions, you don't even need anything before the SELECT statement piece)...\nPARTITIONS t(:partId) SELECT t FROM TABLE as t INNER JOIN t.security as s WHERE s.securityType = :type and t.numShares = :shares\")\nThis allows relational data in a noSQL environment AND IF you partition your data, you can scale as well very nicely with fast queries and fast joins.\nIf you like, we can quickly code up a prototype server that exposes an interface where you send in S-SQL requests and we return some form of json back to you.  We would like it to be different than SQL result sets which was a very bad idea when left joins and inner joins are in the picture.\nie. we would return results on a join like so (so that you can set a max results that actually works)...\ntableA row A   -  tableB row45\n               -  tableB row65\n               -  tableB row 78\ntableA row C   -  tableB row46\n               -  tableB row93\nNOTICE that we do not return multiple row A's so that if you have max results 2 you get row A and row C where as in ODBC\/JDBC, you would get ONLY rowA two times with row45 and row 65 because that is what the table looks like when it is returned (which is kind of stupid when you are in an OO language of any kind).\njust let playOrm team know if you need anything on the playOrm github website.\nDean","Q_Score":6,"Tags":"python,sqlalchemy,cassandra","A_Id":12302894,"CreationDate":"2012-09-06T10:17:00.000","Title":"Can I use SQLAlchemy with Cassandra CQL?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm looking to expand my recommender system to include other features (dimensions). So far, I'm tracking how a user rates some document, and using that to do the recommendations. I'm interested in adding more features, such as user location, age, gender, and so on.\nSo far, a few mysql tables have been enough to handle this, but i fear it will quickly become messy as i add more features.\nMy question: how can i best represent and persist this kind of multi dimensional data?\nPython specific tips would be helpful.\nThank you","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":289,"Q_Id":12355416,"Users Score":0,"Answer":"An SQL database should work fine in your case. In fact, you can store all the training examples in just one database, each row representing a particular training set and each column representing a feature. You can add features by adding collumns as and when required. In a relational database, you might come across access errors when querying for your data for various inconsistency reasons. Try using a NoSQL database. I personally user MongoDB and Pymongo on python to store the training examples as dicts in JSON format. (Easier for web apps this way).","Q_Score":1,"Tags":"python,numpy,scipy,data-mining","A_Id":12369285,"CreationDate":"2012-09-10T16:05:00.000","Title":"Multi feature recommender system representation","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm looking to expand my recommender system to include other features (dimensions). So far, I'm tracking how a user rates some document, and using that to do the recommendations. I'm interested in adding more features, such as user location, age, gender, and so on.\nSo far, a few mysql tables have been enough to handle this, but i fear it will quickly become messy as i add more features.\nMy question: how can i best represent and persist this kind of multi dimensional data?\nPython specific tips would be helpful.\nThank you","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":289,"Q_Id":12355416,"Users Score":0,"Answer":"I recommend using tensors, which is multidimensional arrays. You can use any data table or simply text files to store a tensor. Each line or row is a record \/ transaction with different features all listed.","Q_Score":1,"Tags":"python,numpy,scipy,data-mining","A_Id":24491488,"CreationDate":"2012-09-10T16:05:00.000","Title":"Multi feature recommender system representation","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Trying to set up some basic data I\/O scripts in python that read and write from a local sqlite db. I'd like to use the command line to verify that my scripts work as expected, but they don't pick up on any of the databases or tables I'm creating.\nMy first script writes some data from a dict into the table, and the second script reads it and prints it.\nWrite:\n# first part of script creates a dict called 'totals'\n\nimport sqlite3 as lite\n\ncon = lite.connect('test.db')\n\nwith con:\n    cur = con.cursor()\n\n    cur.execute(\"DROP TABLE IF EXISTS testtbl\")    \n\n    cur.execute(\"CREATE TABLE testtbl(Date TEXT PRIMARY KEY, Count INT, AverageServerTime REAL, TotalServerTime REAL, AverageClientTime REAL, TotalClientTime REAL)\")\n    cur.execute('INSERT INTO testtbl VALUES(\"2012-09-08\", %s, %s, %s, %s, %s)' % (float(totals['count()']), float(totals['serverTime\/count()']), float(totals['serverTime']), float(totals['totalLoadTime\/count()']), float(totals['totalLoadTime'])))\n\nRead:\n\nimport sqlite3 as lite\n\ncon = lite.connect('test.db')\n\nwith con:    \n\n    cur = con.cursor()    \n    cur.execute(\"SELECT * FROM testtbl\")\n\n    rows = cur.fetchall()\n\n    for row in rows:\n        print row\n\nThese scripts are separate and both work fine. However, if I navigate to the directory in the command line and activate sqlite3, nothing further works. I've tried '.databases', '.tables', '.schema' commands and can't get it to respond to this particular db. I can create dbs within the command line and view them, but not the ones created by my script. How do I link these up?\nRunning stock Ubuntu 12.04, Python 2.7.3, SQLite 3.7.9. I also installed libsqlite3-dev but that hasn't helped.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1252,"Q_Id":12360279,"Users Score":2,"Answer":"Are you putting the DB file name in the command ? \n$ sqlite3 test.db","Q_Score":1,"Tags":"python,linux,sqlite,ubuntu","A_Id":12360397,"CreationDate":"2012-09-10T22:23:00.000","Title":"sqlite3 command line tools don't work in Ubuntu","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":0},{"Question":"Okay, \nI kinda asked this question already, but  noticed that i might have not been as clear as i could have been, and might have made some errors myself.\nI have also noticed many people having the same or similar problems with sqlite3 in python. So i thought i would ask this as clearly as i could, so it could possibly help others with the same issues aswell.\nWhat does python need to find when compiling, so the module is enabled and working?\n(In detail, i mean exact files, not just \"sqlite dev-files\")?\nAnd if it needs a library, it propably needs to be compiled with the right architecture?","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":3032,"Q_Id":12420338,"Users Score":0,"Answer":"As I understand you would like to install python form sources. To make sqlite module available you have to install sqlite package and its dev files (for example sqlite-devel for CentOS). That's it. YOu have to re-configure your sources after installing the required packages.\nBtw you will face up the same problem with some other modules.","Q_Score":0,"Tags":"python,sqlite","A_Id":12420541,"CreationDate":"2012-09-14T07:59:00.000","Title":"What does Python need to install sqlite3 module?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"For my database project, I am using SQL Alchemy. I have a unit test that adds the object to the table, finds it, updates it, and deletes it. After it goes through that, I assumed I would call the session.rollback method in order to revert the database changes. It does not work because my sequences are not reverted. My plan for the project is to have one database, I do not want to create a test database.\nI could not find in the documentation on SQL Alchemy on how to properly rollback the database changes. Does anyone know how to rollback the database transaction?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":3017,"Q_Id":12440044,"Users Score":-3,"Answer":"Postgres does not rollback advances in a sequence even if the sequence is used in a transaction which is rolled back.  (To see why, consider what should happen if, before one transaction is rolled back, another using the same sequence is committed.)\nBut in any case, an in-memory database (SQLite makes this easy) is the best choice for unit tests.","Q_Score":4,"Tags":"python,unit-testing,sqlalchemy,rollback","A_Id":12443800,"CreationDate":"2012-09-15T18:39:00.000","Title":"How to rollback the database in SQL Alchemy?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am provided with text files containing data that I need to load into a postgres database.\nThe files are structured in records (one per line) with fields separated by a tilde (~). Unfortunately it happens that every now and then a field content will include a tilde.\nAs the files are not tidy CSV, and the tilde's not escaped, this results in records containing too many fields, which cause the database to throw an exception and stop loading.\nI know what the record should look like (text, integer, float fields).\nDoes anyone have suggestions on how to fix the overlong records? I code in per but I am happy with suggestions in python, javascript, plain english.","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":111,"Q_Id":12553197,"Users Score":0,"Answer":"If you know what each field is supposed to be, perhaps you could write a regular expression which would match that field type only (ignoring tildes) and capture the match, then replace the original string in the file?","Q_Score":1,"Tags":"python,perl,language-agnostic","A_Id":12553211,"CreationDate":"2012-09-23T14:36:00.000","Title":"Messed up records - separator inside field content","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Is there any feasible way to upload a file which is generated dynamically to amazon s3 directly without first create a local file and then upload to the s3 server? I use python. Thanks","AnswerCount":12,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":52339,"Q_Id":12570465,"Users Score":0,"Answer":"Given that encryption at rest is a much desired data standard now, smart_open does not support this afaik","Q_Score":38,"Tags":"python,amazon-s3,amazon","A_Id":56126467,"CreationDate":"2012-09-24T18:09:00.000","Title":"How to upload a file to S3 without creating a temporary local file","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":1,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Is there any feasible way to upload a file which is generated dynamically to amazon s3 directly without first create a local file and then upload to the s3 server? I use python. Thanks","AnswerCount":12,"Available Count":2,"Score":0.0333209931,"is_accepted":false,"ViewCount":52339,"Q_Id":12570465,"Users Score":2,"Answer":"I assume you're using boto. boto's Bucket.set_contents_from_file() will accept a StringIO object, and any code you have written to write data to a file should be easily adaptable to write to a StringIO object. Or if you generate a string, you can use set_contents_from_string().","Q_Score":38,"Tags":"python,amazon-s3,amazon","A_Id":12570568,"CreationDate":"2012-09-24T18:09:00.000","Title":"How to upload a file to S3 without creating a temporary local file","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":1,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have the below setup\n\n2 node hadoop\/hbase cluster with thirft server running on hbase.\nHbase has a table with 10 million rows.\n\nI need to run aggregate queries like sum() on the hbase table\nto show it on the web(charting purpose).\nFor now I am using python(thrift client) to get the dataset and display.\nI am looking for database(hbase) level aggregation function to use in the web.\nAny thoughts?","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1019,"Q_Id":12585286,"Users Score":0,"Answer":"Phoenix is a good solution for low latency result from Hbase tables than Hive.\nIt is good for range scans than Hbase scanners because they use secondary indexes and SkipScan.\nAs in your case , you use Python and phoenix API have only JDBC connectors.\nElse Try Hbase Coprocessors. Which do SUM, MAX, COUNT,AVG functions.\nyou can enable coprocessors while creating table and can USE the Coprocessor functions\nYou can try Impala, which provide an ODBC connector, JDBC connector. Impala uses hive metatable for executing massively parallel batch execution.\nYou need to create a Hive metatable for your Hbase Table.","Q_Score":0,"Tags":"java,python,hadoop,hbase,thrift","A_Id":21502085,"CreationDate":"2012-09-25T14:35:00.000","Title":"Hadoop Hbase query","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am finding Neo4j slow to add nodes and relationships\/arcs\/edges when using the REST API via py2neo for Python. I understand that this is due to each REST API call executing as a single self-contained transaction.\nSpecifically, adding a few hundred pairs of nodes with relationships between them takes a number of seconds, running on localhost.\nWhat is the best approach to significantly improve performance whilst staying with Python?\nWould using bulbflow and Gremlin be a way of constructing a bulk insert transaction?\nThanks!","AnswerCount":5,"Available Count":1,"Score":0.0798297691,"is_accepted":false,"ViewCount":12651,"Q_Id":12643662,"Users Score":2,"Answer":"Well, I myself had need for massive performance from neo4j. I end up doing following things to improve graph performance.\n\nDitched py2neo, since there were lot of issues with it. Besides it is very convenient to use REST endpoint provided by neo4j, just make sure to use request sessions.\nUse raw cypher queries for bulk insert, instead of any OGM(Object-Graph Mapper). That is very crucial if you need an high-performant system.\nPerformance was not still enough for my needs, so I ended writing a custom system that merges 6-10 queries together using WITH * AND UNION clauses. That improved performance by a factor of 3 to 5 times.\nUse larger transaction size with atleast 1000 queries.","Q_Score":18,"Tags":"python,neo4j,py2neo","A_Id":31026259,"CreationDate":"2012-09-28T16:15:00.000","Title":"Fastest way to perform bulk add\/insert in Neo4j with Python?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":1,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I see plenty of examples of importing a CSV into a PostgreSQL db, but what I need is an efficient way to import 500,000 CSV's into a single PostgreSQL db. Each CSV is a bit over 500KB (so grand total of approx 272GB of data).\nThe CSV's are identically formatted and there are no duplicate records (the data was generated programatically from a raw data source).  I have been searching and will continue to search online for options, but I would appreciate any direction on getting this done in the most efficient manner possible. I do have some experience with Python, but will dig into any other solution that seems appropriate.\nThanks!","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":10104,"Q_Id":12646305,"Users Score":0,"Answer":"Nice chunk of data you have there. I'm not 100% sure about Postgre, but at least MySQL provides some SQL commands, to feed a csv directly into a table. This bypasses any insert checks and so on and is thatswhy more than a order of magnitude faster than any ordinary insert operations.\nSo the probably fastest way to go is create some simple python script, telling your postgre server, which csv files in which order to hungrily devour into it's endless tables.","Q_Score":9,"Tags":"python,csv,import,postgresql-9.1","A_Id":12646923,"CreationDate":"2012-09-28T19:38:00.000","Title":"Efficient way to import a lot of csv files into PostgreSQL db","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have downloaded mysql-connector-python-1.0.7-py2.7.msi from MySQL site \nand try to install but it gives error that\nPython v2.7 not found. We only support Microsoft Windows Installer(MSI) from python.org.\nI am using Official Python v 2.7.3 on windows XP SP3 with MySQL esssential5.1.66\nNeed Help ???","AnswerCount":8,"Available Count":2,"Score":1.0,"is_accepted":false,"ViewCount":19218,"Q_Id":12702146,"Users Score":10,"Answer":"I met the similar problem under Windows 7 when installing mysql-connector-python-1.0.7-py2.7.msi and mysql-connector-python-1.0.7-py3.2.msi.\nAfter changing from \"Install only for yourself\" to \"Install for all users\" when installing Python for windows, the \"python 3.2 not found\" problem disappear and mysql-connector-python-1.0.7-py3.2.msi was successfully installed.\nI guess the problem is that mysql connector installer only looks for HKEY_LOCAL_MACHINE entries, and the things it looks for might be under HKEY_CURRENT_USER etc. So the solution that change the reg table directly also works.","Q_Score":12,"Tags":"python,mysql,python-2.7,mysql-connector-python","A_Id":13899478,"CreationDate":"2012-10-03T04:57:00.000","Title":"mysql for python 2. 7 says Python v2.7 not found","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have downloaded mysql-connector-python-1.0.7-py2.7.msi from MySQL site \nand try to install but it gives error that\nPython v2.7 not found. We only support Microsoft Windows Installer(MSI) from python.org.\nI am using Official Python v 2.7.3 on windows XP SP3 with MySQL esssential5.1.66\nNeed Help ???","AnswerCount":8,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":19218,"Q_Id":12702146,"Users Score":0,"Answer":"I solved this problem by using 32bit python","Q_Score":12,"Tags":"python,mysql,python-2.7,mysql-connector-python","A_Id":19051115,"CreationDate":"2012-10-03T04:57:00.000","Title":"mysql for python 2. 7 says Python v2.7 not found","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a server which files get uploaded to, I want to be able to forward these on to s3 using boto, I have to do some processing on the data basically as it gets uploaded to s3.\nThe problem I have is the way they get uploaded I need to provide a writable stream that incoming data gets written to and to upload to boto I need a readable stream. So it's like I have two ends that don't connect. Is there a way to upload to s3 with a writable stream? If so it would be easy and I could pass upload stream to s3 and it the execution would chain along.\nIf there isn't I have two loose ends which I need something in between with a sort of buffer, that can read from the upload to keep that moving, and expose a read method that I can give to boto so that can read. But doing this I'm sure I'd need to thread the s3 upload part which I'd rather avoid as I'm using twisted.\nI have a feeling I'm way over complicating things but I can't come up with a simple solution. This has to be a common-ish problem, I'm just not sure how to put it into words very well to search it","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":636,"Q_Id":12714965,"Users Score":3,"Answer":"boto is a Python library with a blocking API.  This means you'll have to use threads to use it while maintaining the concurrence operation that Twisted provides you with (just as you would have to use threads to have any concurrency when using boto ''without'' Twisted; ie, Twisted does not help make boto non-blocking or concurrent).\nInstead, you could use txAWS, a Twisted-oriented library for interacting with AWS.  txaws.s3.client provides methods for interacting with S3.  If you're familiar with boto or AWS, some of these should already look familiar.  For example, create_bucket or put_object.\ntxAWS would be better if it provided a streaming API so you could upload to S3 as the file is being uploaded to you.  I think that this is currently in development (based on the new HTTP client in Twisted, twisted.web.client.Agent) but perhaps not yet available in a release.","Q_Score":4,"Tags":"python,stream,twisted,boto","A_Id":12716129,"CreationDate":"2012-10-03T18:54:00.000","Title":"Boto reverse the stream","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":1,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I want to select data from multiple tables, so i just want to know that can i used simple SQL queries for that, If yes then please give me an example(means where to use these queries and how).\nThanks.","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":77,"Q_Id":12740424,"Users Score":1,"Answer":"Try this.\nhttps:\/\/docs.djangoproject.com\/en\/dev\/topics\/db\/sql\/","Q_Score":0,"Tags":"python,sql,django,django-queryset","A_Id":12740533,"CreationDate":"2012-10-05T06:05:00.000","Title":"Can I used simple sql commands in django","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Background:\nI'm working on dataview, and many of the reports are generated by very long running queries. I've written a small query caching daemon in python that accepts a query, spawns a thread to run it, and stores the result when done as a pickled string. The results are generally various aggregations broken down by month, or other factors, and the result sets are consequently not large. So my caching daemon can check whether it has the result already, and return it immediately, otherwise it sends back a 'pending' message (or 'error' or 'failed' or various other messages). The point being, that the client, which is a django web server would get back 'pending' and query again in 5~10 seconds, in the meanwhile putting up a message for the user saying 'your report is being built, please be patient'. \nThe problem:\nI would like to add the ability for the user to cancel a long running query, assuming it hasn't been cached already. I know I can kill a query thread in MySQL using KILL, but is there a way to get the thread\/query\/process id of the query in a manner similar to getting the id of the last inserted row? I'm doing this through the python MySQLdb module, and I can't see any properties\/methods of the cursor object that would return this.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1016,"Q_Id":12743436,"Users Score":2,"Answer":"There is a property of the connection object called thread_id, which returns an id to be passed to KILL. MySQL has a thread for each connection, not for each cursor, so you are not killing queries, but are instead killing connection. To kill an individual query you must run each query in it's own connection, and then kill the connection using the result from thread_id","Q_Score":0,"Tags":"python,mysql","A_Id":12743439,"CreationDate":"2012-10-05T09:32:00.000","Title":"Get process id (of query\/thread) of most recently run query in mysql using python mysqldb","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm reading conflicting reports about using PostgreSQL on Amazon's Elastic Beanstalk for python (Django).  \nSome sources say it isn't possible: (http:\/\/www.forbes.com\/sites\/netapp\/2012\/08\/20\/amazon-cloud-elastic-beanstalk-paas-python\/).  I've been through a dummy app setup, and it does seem that MySQL is the only option (amongst other ones that aren't Postgres).\nHowever, I've found fragments around the place mentioning that it is possible - even if they're very light on detail.\nI need to know the following:\n\nIs it possible to run a PostgreSQL database with a Django app on Elastic Beanstalk?\nIf it's possible, is it worth the trouble?\nIf it's possible, how would you set it up?","AnswerCount":2,"Available Count":1,"Score":0.4621171573,"is_accepted":false,"ViewCount":2422,"Q_Id":12850550,"Users Score":5,"Answer":"Postgre is now selectable from the AWS RDS configurations.  Validated through Elastic Beanstalk application setup 2014-01-27.","Q_Score":5,"Tags":"python,django,postgresql,amazon-elastic-beanstalk","A_Id":21391684,"CreationDate":"2012-10-12T00:21:00.000","Title":"PostgreSQL for Django on Elastic Beanstalk","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have 10000 files in a s3 bucket.When I list all the files it takes 10 minutes.  I want to implement a search module using BOTO (Python interface to AWS) which searches files based on user input. Is there a way I can search specific files with less time?","AnswerCount":2,"Available Count":1,"Score":0.2913126125,"is_accepted":false,"ViewCount":5534,"Q_Id":12904326,"Users Score":3,"Answer":"There are two ways to implement the search...\nCase 1. As suggested by john - you can specify the prefix of the s3 key file in your list method. that will return you result of S3 key files which starts with the given prefix.\nCase 2. If you want to search the S3 key which are end with specific suffix or we can say extension then you can specify the suffix in delimiter. Remember it will give you correct result only in the case if you are giving suffix for the search item which is end with that string. \nElse delimiter is used for path separator.\nI will suggest you Case 1 but if you want to faster search with specific suffix then you can try case 2","Q_Score":2,"Tags":"python,amazon-s3,boto","A_Id":12907767,"CreationDate":"2012-10-15T21:29:00.000","Title":"Search files(key) in s3 bucket takes longer time","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":1,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"A user accesses his contacts on his mobile device. I want to send back to the server all the phone numbers (say 250), and then query for any User entities that have matching phone numbers. \nA user has a phone field which is indexed. So I do User.query(User.phone.IN(phone_list)), but I just looked at AppStats, and is this damn expensive. It cost me 250 reads for this one operation, and this is something I expect a user to do often. \nWhat are some alternatives? I suppose I can set the User entity's id value to be his phone number (i.e when creating a user I'd do user = User(id = phone_number)), and then get directly by keys via ndb.get_multi(phones), but I also want to perform this same query with emails too.\nAny ideas?","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":176,"Q_Id":12976652,"Users Score":0,"Answer":"I misunderstood part of your problem, I thought you were issuing a query that was giving you 250 entities.\nI see what the problem is now, you're issuing an IN query with a list of 250 phone numbers, behind the scenes, the datastore is actually doing 250 individual queries, which is why you're getting 250 read ops.\nI can't think of a way to avoid this.  I'd recommend avoiding searching on long lists of phone numbers.  This seems like something you'd need to do only once, the first time the user logs in using that phone.  Try to find some way to store the results and avoid the query again.","Q_Score":3,"Tags":"python,google-app-engine","A_Id":12980347,"CreationDate":"2012-10-19T14:43:00.000","Title":"Efficient way to do large IN query in Google App Engine?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"Php or python\nUse and connect to our existing postgres databases\nopen source \/ or very low license fees\nCommon features of cms, with admin tools to help manage \/ moderate community\nhave a large member base on very basic site where members provide us contact info and info about their professional characteristics.  About to expand to build new community site (to migrate our member base to) where the users will be able to msg each other, post to forums, blog, share private group discussions, and members will be sent inivitations to earn compensation for their expertise. Profile pages, job postings, and video chat would be plus.\nAlready have a team of admins savvy with web apps to help manage it but our developer resources are limited (3-4 programmers) and looking to save time in development as opposed to building our new site from scratch.","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":5703,"Q_Id":13000007,"Users Score":1,"Answer":"Have you tried Drupal.  Drupal supports PostgreSQL and is written in PHP and is open source.","Q_Score":5,"Tags":"postgresql,content-management-system,python-2.7","A_Id":13003890,"CreationDate":"2012-10-21T16:56:00.000","Title":"What is a good cms that is postgres compatible, open source and either php or python based?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I cannot get a connection to a MySQL database if my password contains punctuation characters in particular $ or @.  I have tried to escape the characters, by doubling the $$ etc. but no joy.\nI have tried the pymysql library and the _mssql library.\nthe code... \nself.dbConn = _mysql.connect(host=self.dbDetails['site'], port=self.dbDetails['port'], user=self.dbDetails['user'], passwd=self.dbDetails['passwd'], db=self.dbDetails['db'])\nwhere self.dbDetails['passwd'] = \"$abcdef\". \nI have tried '$$abcdef', and re.escape(self.dbDetails['passwd']), and '\\$abcdef' but nothing works until I change the users password to remove the \"$\". Then it connects just fine. The only error I am getting is a failure to connect. I guess I will have to figure out how to print the actual exception message.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":432,"Q_Id":13004789,"Users Score":0,"Answer":"Try to MySQLdb package, you can punctuation in password to connect database through this package.","Q_Score":2,"Tags":"python,mysql,passwords","A_Id":16186975,"CreationDate":"2012-10-22T03:56:00.000","Title":"How to connect with passwords that contains characters like \"$\" or \"@\"?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am using Django non-rel version with mongodb backends. I am interested in tracking the changes that occur on model instances e.g if someone creates\/edits or deletes a model instance. Backend db is mongo hence models have an associated \"_id\" fields with them in the respective collections\/dbs.\nNow i want to extract this \"_id\" field on which this modif operation took place. The idea is to write this \"_id\" field to another db so someone can pick it up from there and know what object was updated.\nI thought about overriding the save() method from Django \"models.Model\" since all my models are derived from that. However the mongo \"_id\" field is obviously not present there since the mongo-insert has not taken place yet. \nIs there any possibility of a pseudo post-save() method that can be called after the save operation has taken place into mongo? Can django\/django-toolbox\/pymongo provide such a combination?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":132,"Q_Id":13024361,"Users Score":0,"Answer":"After some deep digging into the Django Models i was able to solve the problem. The save() method inturn call the save_base() method. This method saves the returned results, ids in case of mongo, into self.id. This _id field can then be picked by by over riding the save() method for the model","Q_Score":0,"Tags":"python,django,mongodb,django-models,django-nonrel","A_Id":13031452,"CreationDate":"2012-10-23T06:01:00.000","Title":"Django-Nonrel(mongo-backend):Model instance modification tracking","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Which of these two languages interfaces better and delivers a better performance\/toolset for working with sqlite database?  I am familiar with both languages but need to choose one for a project I'm developing and so I thought I would ask here. I don't believe this to be opinionated as performance of a language is pretty objective.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":150,"Q_Id":13059142,"Users Score":5,"Answer":"There is no good reason to choose one over the other as far as sqlite performance or usability.\nBoth languages have perfectly usable (and pythonic\/rubyriffic) sqlite3 bindings.\nIn both languages, unless you do something stupid, the performance is bounded by the sqlite3 performance, not by the bindings.\nNeither language's bindings are missing any uncommon but sometimes performance-critical functions (like an \"exec many\", manual transaction management, etc.).\nThere may be language-specific frameworks that are better or worse in how well they integrate with sqlite3, but at that point you're choosing between frameworks, not languages.","Q_Score":0,"Tags":"python,ruby,sqlite","A_Id":13059204,"CreationDate":"2012-10-24T23:00:00.000","Title":"ruby or python for use with sqlite database?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have huge tables of data that I need to manipulate (sort, calculate new quantities, select specific rows according to some conditions and so on...). So far I have been using a spreadsheet software to do the job but this is really time consuming and I am trying to find a  more efficient way to do the job. \nI use python but I could not figure out how to use it for such things. I am wondering if anybody can suggest something to use. SQL?!","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":97,"Q_Id":13060427,"Users Score":1,"Answer":"This is a very general question, but there are multiple things that you can do to possibly make your life easier.\n1.CSV   These are very useful if you are storing data that is ordered in columns, and if you are looking for easy to read text files.\n2.Sqlite3   Sqlite3 is a database system that does not require a server to use (it uses a file instead), and is interacted with just like any other database system. However, for very large scale projects that are handling massive amounts of data, it is not recommended.\n3.MySql    MySql is a database system that requires a server to interact with, but can be tweaked for very large scale projects, as well as small scale projects.\nThere are many other different types of systems though, so I suggest you search around and find that perfect fit. However, if you want to mess around with Sqlite3 or CSV, both Sqlite3 and CSV modules are supplied in the standard library with python 2.7 and 3.x I believe.","Q_Score":0,"Tags":"python,sql,sorting,select","A_Id":13060535,"CreationDate":"2012-10-25T01:40:00.000","Title":"sorting and selecting data","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have come across a problem and am not sure which would be the best suitable technology to implement it. Would be obliged if you guys can suggest me some based on your experience.\nI want to load data from 10-15 CSV files each of them being fairly large 5-10 GBs. By load data I mean convert the CSV file to XML and then populate around 6-7 stagings tables in Oracle using this XML. \nThe data needs to be populated such that the elements of the XML and eventually the rows of the table come from multiple CSV files. So for e.g. an element A would have sub-elements coming data from CSV file 1, file 2 and file 3 etc.\nI have a framework built on Top of Apache Camel, Jboss on Linux. Oracle 10G is the database server.\nOptions I am considering,\n\nSmooks - However the problem is that Smooks serializes one CSV at a time and I cant afford to hold on to the half baked java beans til the other CSV files are read since I run the risk of running out of memory given the sheer number of beans I would need to create and hold on to before they are fully populated written to disk as XML.\nSQLLoader - I could skip the XML creation all together and load the CSV directly to the staging tables using SQLLoader. But I am not sure if I can a. load multiple CSV files in SQL Loader to the same tables updating the records after the first file. b. Apply some translation rules while loading the staging tables.\nPython script to convert the CSV to XML.\nSQLLoader to load a different set of staging tables corresponding to the CSV data and then writing stored procedure to load the actual staging tables from this new set of staging tables (a path which I want to avoid given the amount of changes to my existing framework it would need).\n\nThanks in advance. If someone can point me in the right direction or give me some insights from his\/her personal experience it will help me make an informed decision.\nregards,\n-v-\nPS: The CSV files are fairly simple with around 40 columns each. The depth of objects or relationship between the files would be around 2 to 3.","AnswerCount":3,"Available Count":2,"Score":0.0665680765,"is_accepted":false,"ViewCount":2011,"Q_Id":13061800,"Users Score":1,"Answer":"Create a process \/ script that will call a procedure to load csv files to external Oracle table and another script to load it to the destination table.\nYou can also add cron jobs to call these scripts that will keep track of incoming csv files into the directory, process it and move the csv file to an output\/processed folder.\nExceptions also can be handled accordingly by logging it or sending out an email. Good Luck.","Q_Score":3,"Tags":"python,csv,etl,sql-loader,smooks","A_Id":14449025,"CreationDate":"2012-10-25T04:54:00.000","Title":"Choice of technology for loading large CSV files to Oracle tables","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have come across a problem and am not sure which would be the best suitable technology to implement it. Would be obliged if you guys can suggest me some based on your experience.\nI want to load data from 10-15 CSV files each of them being fairly large 5-10 GBs. By load data I mean convert the CSV file to XML and then populate around 6-7 stagings tables in Oracle using this XML. \nThe data needs to be populated such that the elements of the XML and eventually the rows of the table come from multiple CSV files. So for e.g. an element A would have sub-elements coming data from CSV file 1, file 2 and file 3 etc.\nI have a framework built on Top of Apache Camel, Jboss on Linux. Oracle 10G is the database server.\nOptions I am considering,\n\nSmooks - However the problem is that Smooks serializes one CSV at a time and I cant afford to hold on to the half baked java beans til the other CSV files are read since I run the risk of running out of memory given the sheer number of beans I would need to create and hold on to before they are fully populated written to disk as XML.\nSQLLoader - I could skip the XML creation all together and load the CSV directly to the staging tables using SQLLoader. But I am not sure if I can a. load multiple CSV files in SQL Loader to the same tables updating the records after the first file. b. Apply some translation rules while loading the staging tables.\nPython script to convert the CSV to XML.\nSQLLoader to load a different set of staging tables corresponding to the CSV data and then writing stored procedure to load the actual staging tables from this new set of staging tables (a path which I want to avoid given the amount of changes to my existing framework it would need).\n\nThanks in advance. If someone can point me in the right direction or give me some insights from his\/her personal experience it will help me make an informed decision.\nregards,\n-v-\nPS: The CSV files are fairly simple with around 40 columns each. The depth of objects or relationship between the files would be around 2 to 3.","AnswerCount":3,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":2011,"Q_Id":13061800,"Users Score":2,"Answer":"Unless you can use some full-blown ETL tool (e.g. Informatica PowerCenter, Pentaho Data Integration), I suggest the 4th solution - it is straightforward and the performance should be good, since Oracle will handle the most complicated part of the task.","Q_Score":3,"Tags":"python,csv,etl,sql-loader,smooks","A_Id":13062737,"CreationDate":"2012-10-25T04:54:00.000","Title":"Choice of technology for loading large CSV files to Oracle tables","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm using python's MySQLdb to fetch rows from a MySQL 5.6.7 db, that supports microsecond precision datetime columns. When I read a row with MySQLdb I get \"None\" for the time field. Is there are way to read such time fields with python?","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":310,"Q_Id":13068227,"Users Score":1,"Answer":"MySQLdb-1.2.4 (to be released within the next week) and the current release candidate has support for MySQL-5.5 and newer and should solve your problem. Please try 1.2.4c1 from PyPi (pip install MySQL-python)","Q_Score":2,"Tags":"python,mysql,mysql-python","A_Id":13299592,"CreationDate":"2012-10-25T12:08:00.000","Title":"How to read microsecond-precision mysql datetime fields with python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I see that when you add a column and want to create a schemamigration, the field has to have either null=True or default=something.\nWhat I don't get is that many of the fields that I've written in my models initially (say, before initial schemamigration --init or from a converted_to_south app, I did both) were not run against this check, since I didn't have the null\/default error.\nIs it normal?\nWhy is it so? And why is South checking this null\/default thing anyway?","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":107,"Q_Id":13085658,"Users Score":1,"Answer":"If you add a column to a table, which already has some rows populated, then either:\n\nthe column is nullable, and the existing rows simply get a null value for the column\nthe column is not nullable but has a default value, and the existing rows are updated to have that default value for the column\n\nTo produce a non-nullable column without a default, you need to add the column in multiple steps. Either:\n\nadd the column as nullable, populate the defaults manually, and then mark the column as not-nullable\nadd the column with a default value, and then remove the default value\n\nThese are effectively the same, they both will go through updating each row.\nI don't know South, but from what you're describing, it is aiming to produce a single DDL statement to add the column, and doesn't have the capability to add it in multiple steps like this. Maybe you can override that behaviour, or maybe you can use two migrations?\nBy contrast, when you are creating a table, there clearly is no existing data, so you can create non-nullable columns without defaults freely.","Q_Score":0,"Tags":"python,django,postgresql,django-south","A_Id":13085822,"CreationDate":"2012-10-26T11:00:00.000","Title":"South initial migrations are not forced to have a default value?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I see that when you add a column and want to create a schemamigration, the field has to have either null=True or default=something.\nWhat I don't get is that many of the fields that I've written in my models initially (say, before initial schemamigration --init or from a converted_to_south app, I did both) were not run against this check, since I didn't have the null\/default error.\nIs it normal?\nWhy is it so? And why is South checking this null\/default thing anyway?","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":107,"Q_Id":13085658,"Users Score":0,"Answer":"When you have existing records in your database and you add a column to one of your tables, you will have to tell the database what to put in there, south can't read your mind :-)\nSo unless you mark the new field null=True or opt in a default value it will raise an error. If you had an empty database, there are no values to be set, but a model field would still require basic properties. If you look deeper at the field class you're using you will see django sets some default values, like max_length and null (depending on the field).","Q_Score":0,"Tags":"python,django,postgresql,django-south","A_Id":13085826,"CreationDate":"2012-10-26T11:00:00.000","Title":"South initial migrations are not forced to have a default value?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm using python and excel with office 2010 and have no problems there.\nI used python's makepy module in order to bind to the txcel com objects.\nHowever, on a different computer I've installed office 2013 and when I launched makepy no excel option was listed (as opposed to office 2010 where 'Microsoft Excel 14.0 Object Library' is listed by makepy).\nI've searched for 'Microsoft Excel 15.0 Object Library' in the registry and it is there.\nI tried to use : makepy -d 'Microsoft Excel 15.0 Object Library' \nbut that didn't work.\nHelp will be much appreciated.\nThanks.","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":2318,"Q_Id":13121529,"Users Score":0,"Answer":"wilywampa's answer corrects the problem. However, the combrowse.py at win32com\\client\\combrowse.py can also be used to get the IID (Interface Identifier) from the registered type libraries folder and subsequently integrate it with code as suggested by @cool_n_curious. But as stated before, wilywampa's answer does correct the problem and you can just use the makepy.py utility as usual.","Q_Score":4,"Tags":"python,excel,win32com,office-2013","A_Id":42290194,"CreationDate":"2012-10-29T12:20:00.000","Title":"Python Makepy with Office 2013 (office 15)","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a class that can interface with either Oracle or MySQL.  The class is initialized with a keyword of either \"Oracle\" or \"MySQL\" and a few other parameters that are standard for both database types (what to print, whether or not to stop on an exception, etc.).\nIt was easy enough to add if Oracle do A, elif MySQL do B as necessary when I began, but as I add more specialized code that only applies to one database type, this is becoming ugly.  I've split the class into two, one for Oracle and one for MySQL, with some shared functions to avoid duplicate code.\nWhat is the most Pythonic way to handle calling these new classes?  Do I create a wrapper function\/class that uses this same keyword and returns the correct class?  Do I change all of my code that calls the old generic class to call the correct DB-specific class?\nI'll gladly mock up some example code if needed, but I didn't think it was necessary.  Thanks in advance for any help!","AnswerCount":2,"Available Count":1,"Score":0.2913126125,"is_accepted":false,"ViewCount":126,"Q_Id":13125271,"Users Score":3,"Answer":"Create a factory class which returns an implementation based on the parameter. You can then have a common base class for both DB types, one implementation for each and let the factory create, configure and return the correct implementation to the user based on a parameter.\nThis works well when the two classes behave very similarly; but as soon as you want to use DB specific features, it gets ugly because you need methods like isFeatureXSupported() (good approach) or isOracle() (more simple but bad since it moves knowledge of which DB has which feature from the helper class into the app code).\nAlternatively, you can implement all features for both and throw an exception when one isn't supported. In your code, you can then look for the exception to check this. This makes the code more clean but now, you can really check whether a feature is available without actually using it. That can cause problems in the app code (when you want to disable menus, for example, or when the app could do it some other way).","Q_Score":5,"Tags":"python","A_Id":13125435,"CreationDate":"2012-10-29T16:03:00.000","Title":"Most Pythonic way to handle splitting a class into multiple classes","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am using the modules xlwd, xlwt and xlutil to do some Excel manipulations in Python. I am not able to figure out how to copy the value of cell (X,Y) to cell (A,B) in the same sheet of an Excel file in Python. Could someone let me know how to do that?","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":472,"Q_Id":13156730,"Users Score":0,"Answer":"Work on 2 cells among tens of thousands...quite meager.\nNormally,one should present an iteration over rows x columns.","Q_Score":1,"Tags":"python,excel,xlrd,xlwt","A_Id":13998563,"CreationDate":"2012-10-31T11:21:00.000","Title":"Copying value of cell (X,Y) to cell (A,B) in same sheet of an Excel file using Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have few things to ask for custom queries in Django\n\nDO i need to use the DB table name in the query or just the Model name\nif i need to join the various tables in raw sql. do i need to use db field name or model field name like\n\nPerson.objects.raw('SELECT id, first_name, last_name, birth_date FROM Person A\ninner join Address B on A.address  = B.id\n')\nor B.id = A.address_id","AnswerCount":1,"Available Count":1,"Score":0.537049567,"is_accepted":false,"ViewCount":408,"Q_Id":13172331,"Users Score":3,"Answer":"You need to use the database's table and field names in the raw query--the string you provide will be passed to the database, not interpreted by the Django ORM.","Q_Score":0,"Tags":"python,django","A_Id":13172382,"CreationDate":"2012-11-01T06:54:00.000","Title":"Using raw sql in django python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"What is the most efficient way to delete orphan blobs from a Blobstore?\nApp functionality & scope:\n\nA (logged-in) user wants to create a post containing some normal\ndatastore fields (e.g. name, surname, comments) and blobs (images).\nIn addition, the blobs are uploaded asynchronously before the resto\nof the data is sent via a POST\n\nThis leaves a good chance of having orphans as, for example, a user may upload images but not complete the form for one reason or another. This issue would be minimized by not using an asynchronous upload of the blobs before sending the rest of the data, however, this issue would still be there on a smaller scale.\n\n\nPossible, yet inefficient solutions:\n\nWhenever a post is completed (i.e. the rest of the data is sent), you add the blob keys to a table of \"used blobs\". Then, you can run a cron every so often and compare all of the blobs with the table of \"used blobs\". Those that have been uploaded over an hour ago yet are still \"not used\" are deleted.\n\nMy understanding is that running through a list of potentially hundreds of thousands of blob keys and comparing it with another table of hundreds of thousands of \"used blob keys\" is very inefficient.\n\n\nIs there any better way of doing this? I've searched for similar posts yet I couldn't find any mentioning efficient solutions.\nThanks in advance!","AnswerCount":4,"Available Count":3,"Score":0.049958375,"is_accepted":false,"ViewCount":1014,"Q_Id":13186494,"Users Score":1,"Answer":"You can create an entity that links blobs to users. When a user uploads a blob, you immediately create a new record with the blob id, user id (or post id), and time created. When a user submits a post, you add a flag to this entity, indicating that a blob is used. \nNow your cron job needs to fetch all entities of this kind where a flag is not equal to \"true\" and time created is more one hour ago. Moreover, you can fetch keys only, which is a more efficient operation that fetching full entities.","Q_Score":2,"Tags":"google-app-engine,python-2.7,google-cloud-datastore,blobstore","A_Id":13187373,"CreationDate":"2012-11-01T22:29:00.000","Title":"Deleting Blobstore orphans","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"What is the most efficient way to delete orphan blobs from a Blobstore?\nApp functionality & scope:\n\nA (logged-in) user wants to create a post containing some normal\ndatastore fields (e.g. name, surname, comments) and blobs (images).\nIn addition, the blobs are uploaded asynchronously before the resto\nof the data is sent via a POST\n\nThis leaves a good chance of having orphans as, for example, a user may upload images but not complete the form for one reason or another. This issue would be minimized by not using an asynchronous upload of the blobs before sending the rest of the data, however, this issue would still be there on a smaller scale.\n\n\nPossible, yet inefficient solutions:\n\nWhenever a post is completed (i.e. the rest of the data is sent), you add the blob keys to a table of \"used blobs\". Then, you can run a cron every so often and compare all of the blobs with the table of \"used blobs\". Those that have been uploaded over an hour ago yet are still \"not used\" are deleted.\n\nMy understanding is that running through a list of potentially hundreds of thousands of blob keys and comparing it with another table of hundreds of thousands of \"used blob keys\" is very inefficient.\n\n\nIs there any better way of doing this? I've searched for similar posts yet I couldn't find any mentioning efficient solutions.\nThanks in advance!","AnswerCount":4,"Available Count":3,"Score":1.2,"is_accepted":true,"ViewCount":1014,"Q_Id":13186494,"Users Score":3,"Answer":"Thank for the comments. However, I understood those solutions well, I find them too inefficient. Querying thousands of entries for those that are flagged as \"unused\" is not ideal.\nI believe I have come up with a better way and would like to hear your thoughts on it:\nWhen a blob is saved, immediately a deferred task is created to delete the same blob in an hour\u2019s time. If the post is created and saved, the deferred task is deleted, thus the blob will not be deleted in an hour\u2019s time.\nI believe this saves you from having to query thousands of entries every single hour.\nWhat are your thoughts on this solution?","Q_Score":2,"Tags":"google-app-engine,python-2.7,google-cloud-datastore,blobstore","A_Id":13247039,"CreationDate":"2012-11-01T22:29:00.000","Title":"Deleting Blobstore orphans","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"What is the most efficient way to delete orphan blobs from a Blobstore?\nApp functionality & scope:\n\nA (logged-in) user wants to create a post containing some normal\ndatastore fields (e.g. name, surname, comments) and blobs (images).\nIn addition, the blobs are uploaded asynchronously before the resto\nof the data is sent via a POST\n\nThis leaves a good chance of having orphans as, for example, a user may upload images but not complete the form for one reason or another. This issue would be minimized by not using an asynchronous upload of the blobs before sending the rest of the data, however, this issue would still be there on a smaller scale.\n\n\nPossible, yet inefficient solutions:\n\nWhenever a post is completed (i.e. the rest of the data is sent), you add the blob keys to a table of \"used blobs\". Then, you can run a cron every so often and compare all of the blobs with the table of \"used blobs\". Those that have been uploaded over an hour ago yet are still \"not used\" are deleted.\n\nMy understanding is that running through a list of potentially hundreds of thousands of blob keys and comparing it with another table of hundreds of thousands of \"used blob keys\" is very inefficient.\n\n\nIs there any better way of doing this? I've searched for similar posts yet I couldn't find any mentioning efficient solutions.\nThanks in advance!","AnswerCount":4,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":1014,"Q_Id":13186494,"Users Score":0,"Answer":"Use Drafts! Save as draft after each upload. Then dont do the cleaning! Let the user for himself chose to wipe out.\nIf you're planning on posts in a Facebook style use drafts either or make it private. Why bother deleting users' data?","Q_Score":2,"Tags":"google-app-engine,python-2.7,google-cloud-datastore,blobstore","A_Id":16378785,"CreationDate":"2012-11-01T22:29:00.000","Title":"Deleting Blobstore orphans","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"This issue has been occurring on and off for a few weeks now, and it's unlike any that has come up with my project. \nTwo of the models that are used have a timestamp field, which is by default set to timezone.now(). \nThis is the sequence that raises error flags:\n\n\nModel one is created at time 7:30 PM\nModel two is created at time 10:00 PM, but in the \n   MySQL database it's stored as 7:30 PM! \n\nEvery model that is created \n    has its time stamp saved under 7:30 PM, not the actual time, until a certain\n    duration passes. Then a new time is set and all the following models\n    have that new time... Bizzare\n\nSome extra details which may help in discovering the issue:\nI have a bunch of methods that I use to strip my timezones of their tzinfo's and replace them with UTC. \nThis is because I'm doing a timezone.now() - creationTime calculation to create a: \"model was posted this long ago\" feature\nin the project. However, this really should not be the cause of the problem.\nI don't think using datetime.datetime.now() will make any difference either.\nAnyway, thanks for the help!","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":23029,"Q_Id":13225890,"Users Score":66,"Answer":"Just ran into this last week for a field that had default=date.today(). If you remove the parentheses (in this case, try default=timezone.now) then you're passing a callable to the model and it will be called each time a new instance is saved. With the parentheses, it's only being called once when models.py loads.","Q_Score":28,"Tags":"python,django,django-timezone","A_Id":13226368,"CreationDate":"2012-11-05T04:23:00.000","Title":"Django default=timezone.now() saves records using \"old\" time","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm currently building a web service using python \/ flask and would like to build my data layer on top of neo4j, since my core data structure is inherently a graph.\nI'm a bit confused by the different technologies offered by neo4j for that case. Especially : \n\ni originally planned on using the REST Api through py2neo , but the lack of transaction is a bit of a problem.\nThe \"embedded database\" neo4j doesn't seem to suit my case very well. I guess it's useful when you're working with batch and one-time analytics, and don't need to store the database on a different server from the web server.\nI've stumbled upon the neo4django project, but i'm not sure this one offers transaction support (since there are no native client to neo4j for python), and if it would be a problem to use it outside django itself. In fact, after having looked at the project's documentation, i feel like it has exactly the same limitations, aka no transaction (but then, how can you build a real-world service when you can corrupt your model upon a single connection timeout ?). I don't even understand what is the use for that project.\n\nCould anyone could recommend anything ? I feel completely stuck.\nThanks","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1075,"Q_Id":13233107,"Users Score":5,"Answer":"None of the REST API clients will be able to explicitly support (proper) transactions since that functionality is not available through the Neo4j REST API interface. There are a few alternatives such as Cypher queries and batched execution which all operate within a single atomic transaction on the server side; however, my general approach for client applications is to try to build code which can gracefully handle partially complete data, removing the need for explicit transaction control.\nOften, this approach will make heavy use of unique indexing and this is one reason that I have provided a large number of \"get_or_create\" type methods within py2neo. Cypher itself is incredibly powerful and also provides uniqueness capabilities, in particular through the CREATE UNIQUE clause. Using these, you can make your writes idempotent and you can err on the side of \"doing it more than once\" safe in the knowledge that you won't end up with duplicate data.\nAgreed, this approach doesn't give you transactions per se but in most cases it can give you an equivalent end result. It's certainly worth challenging yourself as to where in your application transactions are truly necessary.\nHope this helps\nNigel","Q_Score":2,"Tags":"python,flask,neo4j,py2neo","A_Id":13234558,"CreationDate":"2012-11-05T13:27:00.000","Title":"using neo4J (server) from python with transaction","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Newbie here trying to use python to do some database analysis.  I keep getting the error:\n\"error: cannot locate an Oracle software installation\"  When installing CX_oracle (via easy_install).\nThe problem is I do not have oracle on my local machine, I'm trying to use python to connect to the main oracle server. I have have setup another program to do this(visualdb) and I had a .jar file I used as the driver but I'm not sure how to use it in this case.\nAny suggestions?","AnswerCount":6,"Available Count":3,"Score":0.0333209931,"is_accepted":false,"ViewCount":25818,"Q_Id":13234196,"Users Score":1,"Answer":"Tip for Ubuntu users\nAfter configuring .bashrc environment variables, like it was explained in other answers,  don't forget to reload your terminal window, typing $SHELL.","Q_Score":12,"Tags":"python,oracle,cx-oracle","A_Id":58120873,"CreationDate":"2012-11-05T14:32:00.000","Title":"\"error: cannot locate an Oracle software installation\" When trying to install cx_Oracle","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Newbie here trying to use python to do some database analysis.  I keep getting the error:\n\"error: cannot locate an Oracle software installation\"  When installing CX_oracle (via easy_install).\nThe problem is I do not have oracle on my local machine, I'm trying to use python to connect to the main oracle server. I have have setup another program to do this(visualdb) and I had a .jar file I used as the driver but I'm not sure how to use it in this case.\nAny suggestions?","AnswerCount":6,"Available Count":3,"Score":0.0665680765,"is_accepted":false,"ViewCount":25818,"Q_Id":13234196,"Users Score":2,"Answer":"I got this message when I was trying to install the 32 bit version while having the 64bit Oracle client installed.\nWhat worked for me: reinstalled python with 64 bit (had 32 for some reason), installed cx_Oracle (64bit version) with the Windows installer and it worked perfectly.","Q_Score":12,"Tags":"python,oracle,cx-oracle","A_Id":28741244,"CreationDate":"2012-11-05T14:32:00.000","Title":"\"error: cannot locate an Oracle software installation\" When trying to install cx_Oracle","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Newbie here trying to use python to do some database analysis.  I keep getting the error:\n\"error: cannot locate an Oracle software installation\"  When installing CX_oracle (via easy_install).\nThe problem is I do not have oracle on my local machine, I'm trying to use python to connect to the main oracle server. I have have setup another program to do this(visualdb) and I had a .jar file I used as the driver but I'm not sure how to use it in this case.\nAny suggestions?","AnswerCount":6,"Available Count":3,"Score":0.0665680765,"is_accepted":false,"ViewCount":25818,"Q_Id":13234196,"Users Score":2,"Answer":"I installed cx_Oracle, but I also had to install an Oracle client to use it (the cx_Oracle module is just a common and pythonic way to interface with the Oracle client in Python).\nSo you have to set the variable ORACLE_HOME to your Oracle client folder (on Unix: via a shell, for instance; on Windows: create a new variable if it does not exist in the Environment variables of the Configuration Panel). Your folder $ORACLE_HOME\/network\/admin (%ORACLE_HOME%\\network\\admin on Windows) is the place where you would place your tnsnames.ora file.","Q_Score":12,"Tags":"python,oracle,cx-oracle","A_Id":13234377,"CreationDate":"2012-11-05T14:32:00.000","Title":"\"error: cannot locate an Oracle software installation\" When trying to install cx_Oracle","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I've looked a a number of questions on this site and cannot find an answer to the question: How to create multiple NEW tables in a database (in my case I am using PostgreSQL) from multiple CSV source files, where the new database table columns accurately reflect the data within the CSV columns?\nI can write the CREATE TABLE syntax just fine, and I can read the rows\/values of a CSV file(s), but does a method already exist to inspect the CSV file(s) and accurately determine the column type?  Before I build my own, I wanted to check if this already existed.\nIf it doesn't exist already, my idea would be to use Python, CSV module, and psycopg2 module to build a python script that would:\n\nRead the CSV file(s).\nBased upon a subset of records (10-100 rows?), iteratively inspect each column of each row to automatically determine the right column type of the data in the CSV.  Therefore, if row 1, column A had a value of 12345 (int), but row 2 of column A had a value of ABC (varchar), the system would automatically determine it should be a format varchar(5) based upon the combination of the data it found in the first two passes.  This process could go on as many times as the user felt necessary to determine the likely type and size of the column.\nBuild the CREATE TABLE query as defined by the column inspection of the CSV.\nExecute the create table query.\nLoad the data into the new table.\n\nDoes a tool like this already exist within either SQL, PostgreSQL, Python, or is there another application I should be be using to accomplish this (similar to pgAdmin3)?","AnswerCount":3,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":7124,"Q_Id":13239004,"Users Score":0,"Answer":"Although this is quite an old question, it doesn't seem to have a satisfying answer and I was struggling with the exact samen issue. With the arrival of SQL Server Management Studio 2018 edition - and probably somewhat before that - a pretty good solution was offered by Microsoft.\n\nIn SSMS on a database node in the object explorer, right-click, select 'Tasks' and choose 'Import data';\nChoose 'Flat file' as source and, in the General section, browse to your .csv file. An important note here: make sure there's no table in your target SQL server matching the files name;\nIn the Advanced section, click on 'Suggest types' and in the next dialog, enter preferrably the total number of rows in your file or, if that's too much, a large enough number to cover all possible values (this takes a while);\nClick next, and in the subsquent step, connect to your SQL server. Now, every brand has their own flavour of data types, but you should get a nice set of relevant pointers for your taste later on. I've tested this using the SQL Server Native Client 11.0. Please leave your comments for other providers as a reply to this solution;\nHere it comes... click 'Edit Mappings'...;\nclick 'Edit SQL' et voila, a nice SQL statement with all the discovered data types;\nClick through to the end, selecting 'Run immediately' to see all of your .csv columns created with appopriate types in your SQL server.\n\nExtra:\nIf you run the above steps twice, exactly the same way with the same file, the first loop will use the 'CREATE TABLE...' statement, but the second go will skip table creation. If you save the second run as an SSIS (Integration Services) file, you can later re-run the entire setup without scanning the .csv file.","Q_Score":11,"Tags":"python,sql,postgresql,pgadmin","A_Id":52581750,"CreationDate":"2012-11-05T19:30:00.000","Title":"Create SQL table with correct column types from CSV","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I've looked a a number of questions on this site and cannot find an answer to the question: How to create multiple NEW tables in a database (in my case I am using PostgreSQL) from multiple CSV source files, where the new database table columns accurately reflect the data within the CSV columns?\nI can write the CREATE TABLE syntax just fine, and I can read the rows\/values of a CSV file(s), but does a method already exist to inspect the CSV file(s) and accurately determine the column type?  Before I build my own, I wanted to check if this already existed.\nIf it doesn't exist already, my idea would be to use Python, CSV module, and psycopg2 module to build a python script that would:\n\nRead the CSV file(s).\nBased upon a subset of records (10-100 rows?), iteratively inspect each column of each row to automatically determine the right column type of the data in the CSV.  Therefore, if row 1, column A had a value of 12345 (int), but row 2 of column A had a value of ABC (varchar), the system would automatically determine it should be a format varchar(5) based upon the combination of the data it found in the first two passes.  This process could go on as many times as the user felt necessary to determine the likely type and size of the column.\nBuild the CREATE TABLE query as defined by the column inspection of the CSV.\nExecute the create table query.\nLoad the data into the new table.\n\nDoes a tool like this already exist within either SQL, PostgreSQL, Python, or is there another application I should be be using to accomplish this (similar to pgAdmin3)?","AnswerCount":3,"Available Count":2,"Score":1.0,"is_accepted":false,"ViewCount":7124,"Q_Id":13239004,"Users Score":7,"Answer":"I have been dealing with something similar, and ended up writing my own module to sniff datatypes by inspecting the source file.  There is some wisdom among all the naysayers, but there can also be reasons this is worth doing, particularly when we don't have any control of the input data format (e.g. working with government open data), so here are some things I learned in the process:\n\nEven though it's very time consuming, it's worth running through the entire file rather than a small sample of rows.  More time is wasted by having a column flagged as numeric that turns out to have text every few thousand rows and therefore fails to import.\nIf in doubt, fail over to a text type, because it's easier to cast those to numeric or date\/times later than to try and infer the data that was lost in a bad import.\nCheck for leading zeroes in what appear otherwise to be integer columns, and import them as text if there are any - this is a common issue with ID \/ account numbers.\nGive yourself some way of manually overriding the automatically detected types for some columns, so that you can blend some semantic awareness with the benefits of automatically typing most of them.\nDate\/time fields are a nightmare, and in my experience generally require manual processing.\nIf you ever add data to this table later, don't attempt to repeat the type detection - get the types from the database to ensure consistency.\n\nIf you can avoid having to do automatic type detection it's worth avoiding it, but that's not always practical so I hope these tips are of some help.","Q_Score":11,"Tags":"python,sql,postgresql,pgadmin","A_Id":21917162,"CreationDate":"2012-11-05T19:30:00.000","Title":"Create SQL table with correct column types from CSV","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am trying to build an online Python Shell. I execute commands by creating an instance of InteractiveInterpreter and use the command runcode. For that I need to store the interpreter state in the database so that variables, functions, definitions and other values in the global and local namespaces can be used across commands. Is there a way to store the current state of the object InteractiveInterpreter that could be retrieved later and passed as an argument local to InteractiveInterpreter constructor or If I can't do this, what alternatives do I have to achieve the mentioned functionality?\nBelow is the pseudo code of what I am trying to achieve\n\n\ndef fun(code, sessionID):\n     session = Session()\n     # get the latest state of the interpreter object corresponding to SessionID\n     vars = session.getvars(sessionID)\n     it = InteractiveInterpreter(vars)\n     it.runcode(code)\n     #save back the new state of the interpreter object\n     session.setvars(it.getState(),sessionID)\n\n\nHere, session is an instance of table containing all the necessary information.","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":136,"Q_Id":13254044,"Users Score":0,"Answer":"I believe the pickle package should work for you. You can use pickle.dump or pickle.dumps to save the state of most objects. (then pickle.load or pickle.loads to get it back)","Q_Score":0,"Tags":"python,interactive-shell,python-interactive","A_Id":13254202,"CreationDate":"2012-11-06T15:19:00.000","Title":"How to store the current state of InteractiveInterpreter Object in a database?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have started a retrival job for an archive stored in one of my vaults on \nGlacier AWS.\nIt turns out that I do not need to resurrect and download that archive any more.\nIs there a way to stop and\/or delete my Glacier job?\nI am using boto and I cannot seem to find a suitable function.\nThanks","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1164,"Q_Id":13274197,"Users Score":9,"Answer":"The AWS Glacier service does not provide a way to delete a job.  You can:\n\nInitiate a job\nDescribe a job\nGet the output of a job\nList all of your jobs\n\nThe Glacier service manages the jobs associated with an vault.","Q_Score":7,"Tags":"python,amazon-web-services,boto,amazon-glacier","A_Id":13275014,"CreationDate":"2012-11-07T16:42:00.000","Title":"AWS glacier delete job","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm using the most recent versions of all software (Django, Python, virtualenv, MySQLdb) and I can't get this to work.  When I run \"import MySQLdb\" in the python prompt from outside of the virtualenv, it works, inside it says \"ImportError: No module named MySQLdb\".\nI'm trying to learn Python and Linux web development.  I know that it's easiest to use SQLLite, but I want to learn how to develop larger-scale applications comparable to what I can do in .NET.  I've read every blog post on Google and every post here on StackOverflow and they all suggest that I run \"sudo pip install mysql-python\" but it just says \"Requirement already satisfied: mysql-python in \/usr\/lib\/pymodules\/python2.7\"\nAny help would be appreciated!  I'm stuck over here and don't want to throw in the towel and just go back to doing this on Microsoft technologies because I can't even get a basic dev environment up and running.","AnswerCount":3,"Available Count":2,"Score":0.0665680765,"is_accepted":false,"ViewCount":6817,"Q_Id":13288013,"Users Score":1,"Answer":"source $ENV_PATH\/bin\/activate\npip uninstall MySQL-python\npip install MySQL-python\n\nthis worked for me.","Q_Score":9,"Tags":"python,virtualenv,mysql-python","A_Id":43866023,"CreationDate":"2012-11-08T11:17:00.000","Title":"Have MySQLdb installed, works outside of virtualenv but inside it doesn't exist. How to resolve?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm using the most recent versions of all software (Django, Python, virtualenv, MySQLdb) and I can't get this to work.  When I run \"import MySQLdb\" in the python prompt from outside of the virtualenv, it works, inside it says \"ImportError: No module named MySQLdb\".\nI'm trying to learn Python and Linux web development.  I know that it's easiest to use SQLLite, but I want to learn how to develop larger-scale applications comparable to what I can do in .NET.  I've read every blog post on Google and every post here on StackOverflow and they all suggest that I run \"sudo pip install mysql-python\" but it just says \"Requirement already satisfied: mysql-python in \/usr\/lib\/pymodules\/python2.7\"\nAny help would be appreciated!  I'm stuck over here and don't want to throw in the towel and just go back to doing this on Microsoft technologies because I can't even get a basic dev environment up and running.","AnswerCount":3,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":6817,"Q_Id":13288013,"Users Score":14,"Answer":"If you have created the virtualenv with the --no-site-packages switch (the default), then system-wide installed additions such as MySQLdb are not included in the virtual environment packages.\nYou need to install MySQLdb with the pip command installed with the virtualenv. Either activate the virtualenv with the bin\/activate script, or use bin\/pip from within the virtualenv to install the MySQLdb library locally as well.\nAlternatively, create a new virtualenv with system site-packages included by using the --system-site-package switch.","Q_Score":9,"Tags":"python,virtualenv,mysql-python","A_Id":13288095,"CreationDate":"2012-11-08T11:17:00.000","Title":"Have MySQLdb installed, works outside of virtualenv but inside it doesn't exist. How to resolve?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"We are developing application for which we going to use a NoSql database. We have evaluated couchdb and mongodb. Our application is in python and read-speed is most critical for our application. And application is reading a large number of documents.  \nI want ask:\n\nIs reading large number of documents is faster in bson than json?\nWhich is better when we want to read say 100 documents, parse them & print result: python+mongodb+pymongo or python+couchdb+couchdbkit (database going to be on ec2 & accessible over internet)?","AnswerCount":1,"Available Count":1,"Score":-0.1973753202,"is_accepted":false,"ViewCount":468,"Q_Id":13298480,"Users Score":-1,"Answer":"bson\nTry LogoDb from 1985 logo programming language for trs-80","Q_Score":0,"Tags":"python-2.7,pymongo,couchdbkit","A_Id":13641512,"CreationDate":"2012-11-08T21:54:00.000","Title":"CouchDB vs mongodb","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm filtering the twitter streaming API by tracking for several keywords. \nIf for example I only want to query and return from my database tweet information that was filtered by tracking for the keyword = 'BBC' how could this be done?\nDo the tweet information collected have a key:value relating to that keyword by which it was filtered?\nI'm using python, tweepy and MongoDB.\nWould an option be to search for the keyword in the returned json 'text' field? Thus generate a query where it searches for that keyword = 'BBC' in the text field of the returned json data?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":374,"Q_Id":13352796,"Users Score":0,"Answer":"Unfortunately, the Twitter API doesn't provide a way to do this. You can try searching through receive tweets for the keywords you specified, but it might not match exactly.","Q_Score":1,"Tags":"python,mongodb,twitter,tweepy","A_Id":22388827,"CreationDate":"2012-11-12T22:42:00.000","Title":"Querying twitter streaming api keywords from a database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"so I discovered Sets in Python a few days ago and am surprised that they never crossed my mind before even though they make a lot of things really simple. I give an example later.\nSome things are still unclear to me. The docs say that Sets can be created from iterables and that the operators always return new Sets but do they always copy all data from one set to another and from the iterable? I work with a lot of data and would love to have Sets and set operators that behave much like itertools. So Sets([iterable]) would be more like a wrapper and the operators union, intersection and so on would return \"iSets\" and would not copy any data. They all would evaluate once I iter my final Set. In the end I really much would like to have \"iSet\" operators.\nPurpose:\nI work with MongoDB using mongoengine. I have articles saved. Some are associated with a user, some are marked as read others were shown to the user and so on. Wrapping them in Sets that do not load all data would be a great way to combine, intersect etc. them. Obviously I could make special queries but not always since MongoDB does not support joins. So I end up doing joins in Python. I know I could use a relational database then, however, I don't need joins that often and the advantages of MongoDB outweigh them in my case.\nSo what do you think? Is there already a third party module? Would a few lines combining itertools and Sets do?\nEDIT:\nI accepted the answer by Martijn Pieters because it is obviously right. I ended up loading only IDs into sets to work with them. Also, the sets in Python have a pretty good running time.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":707,"Q_Id":13358955,"Users Score":4,"Answer":"Sets are just like dict and list; on creation they copy the references from the seeding iterable.\nIterators cannot be sets, because you cannot enforce the uniqueness requirement of a set. You cannot know if a future value yielded by an iterator has already been seen before.\nMoreover, in order for you to determine what the intersection is between two iterables, you have to load all data from at least one of these iterables to see if there are any matches. For each item in the second iterable, you need to test if that item has been seen in the first iterable. To do so efficiently, you need to have loaded all the items from the first iterable into a set. The alternative would be to loop through the first iterable from start to finish for each item from the second iterable, leading to exponential performance degradation.","Q_Score":2,"Tags":"python,memory-management,set,itertools","A_Id":13358975,"CreationDate":"2012-11-13T10:20:00.000","Title":"Python: Combining itertools and sets to save memory","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm scraping tweets and inserting them into a mongo database for analysis work in python. I want to check the size of my database so that I won't incur additional charges if I run this on amazon. How can I tell how big my current mongo database is on osx? And will a free tier cover me?","AnswerCount":5,"Available Count":2,"Score":0.0399786803,"is_accepted":false,"ViewCount":17118,"Q_Id":13369795,"Users Score":1,"Answer":"Databases are, by default, stored in \/data\/db (some environments override this and use \/var\/lib\/mongodb, however). You can see the total db size by looking at db.stats() (specifically fileSize) in the MongoDB shell.","Q_Score":7,"Tags":"python,macos,mongodb,amazon-ec2","A_Id":13369827,"CreationDate":"2012-11-13T22:13:00.000","Title":"where is mongo db database stored on local hard drive?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm scraping tweets and inserting them into a mongo database for analysis work in python. I want to check the size of my database so that I won't incur additional charges if I run this on amazon. How can I tell how big my current mongo database is on osx? And will a free tier cover me?","AnswerCount":5,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":17118,"Q_Id":13369795,"Users Score":4,"Answer":"I believe on OSX the default location would be \/data\/db.  But you can check your config file for the dbpath value to verify.","Q_Score":7,"Tags":"python,macos,mongodb,amazon-ec2","A_Id":13369857,"CreationDate":"2012-11-13T22:13:00.000","Title":"where is mongo db database stored on local hard drive?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am interested in learning more about node.js and utilizing it in a new project. The problem I am having is envisioning where I could enhance my web stack with it and what role it would play. All I have really done with it is followed a tutorial or two where you make something like a todo app in all JS. That is all fine and dandy but where do I leverage this is in a more complex web architecture.\nso here is an example of how I plan on setting up my application\nweb server for serving views:\n\nPython (flask\/werkzeug) \nJinja\nnginx\nhtml\/css\/js\n\nAPI sever:\n\nPython (flask\/werkzeug)\nSQLAlchemy (ORM)\nnginx\nsupervisor + gunicorn\n\nDB Server\n\nPostgres\n\nSo is there any part of this stack that could be replaced or enhanced by introducing nodeJS I would assume it would be best used on the API server but not exactly sure how.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":228,"Q_Id":13382262,"Users Score":0,"Answer":"It would replace Python (flask\/werkzeug) in both your view server and your API server.","Q_Score":0,"Tags":"python,node.js,web-applications","A_Id":13384050,"CreationDate":"2012-11-14T15:51:00.000","Title":"Where does node.js fit in a stack or enhance it","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm new to web development and I'm trying to get my mac set up for doing Django tutorials and helping some developers with a project that uses postgres. I will try to specify my questions as much as possible. However, it seems that there are lots of floating parts to this question and I'm not quite understanding some parts of the connection between an SQL Shell, virtual environments, paths, databases, terminals (which seem to be necessary to get running on this web development project). I will detail what I did and the error messages that appear. If you could help me with the error messages or simply post links to tutorials that help me better understand how these floating parts work together, I would very much appreciate it. \nI installed postgres and pgAdmin III and set it up on the default port. I created a test database. Now when I try to open it on the local server, I get an error message: 'ERROR: column \"datconfig\" does not exist   LINE1:...b.dattablespace AS spcoid, spcname, datallowconn, dataconfig,...\nHere is what I did before I closed pgAdmin and then reopened it:\nInstallation: The Setup told me that an existing data directory was found at \/Library\/PostgreSQL\/9.2\/data set to use port 5433.\nI loaded an .sql file that I wanted to test (I saved it on my desktop and loaded it into the database from there).\nI'm not sure whether this is related to the problem or not, but I also have virtual environments in a folder ~\/Sites\/django_test (i.e. when I tell the bash Terminal to \u201cactivate\u201d this folder, it puts me in a an (env)). \nI read in a forum that I need to do the Django tutorials by running \u201cpython manage.py runserver\" at the bash Terminal command line. When I do this, I get an error message saying \u201ccan't open file 'manage.py': [Errno 2] No such file or directory\u201d. \nEven when I run the command in the (env), I get the error message: \/Library\/Frameworks\/Python.framework\/Versions\/3.2\/Resources\/Python.app\/Contents\/MacOS\/Python: can't open file 'manage.py': [Errno 2] No such file or directory (Which I presume is telling me that the path is still set on an incorrect version of Python (3.2), even though I want to use version 2.7 and trashed the 3.2 version from my system. )\nI think that there are a few gaps in my understanding here:\n\nI don\u2019t understand the difference between typing in commands into my bash Terminal versus my SQL shell\nIs running \u201cpython manage.py runserver\u201d the same as running Python\nprograms with an IDE like IDLE?\nHow and where do I adjust your $PATH environment variable so that the\ncorrect python occurs first on the path?\nI think that I installed the correct Python version into the virtual\nenvironment using pip install. Why am I still receiving a \u201cNo such\nfile or directory\u201d error?\nWhy does Python version 3.2 still appear in the path indicated by my\nerror message is I trashed it?\n\nIf you could help me with these questions, or simply list links with any tutorials that explain this, that would be much appreciated. And again, sorry for not being more specific. But I thought that it would be more helpful to list the problems that I have with these different pieces rather than just one, since its their interrelatedness that seems to be causing the error messages. Thanks!","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":291,"Q_Id":13495135,"Users Score":1,"Answer":"Er, not sure how we can help you with that. One is for bash, one is for SQL. \nNo, that's for running the development webserver, as the tutorial explains.\nThere's no need to do that, that's what the virtualenv is for.\nThis has nothing to do with Python versions, you simply don't seem to be in the right directory. Note that, again as the tutorial explains, manage.py isn't created until you've run django-admin.py startproject myprojectname. Have you done that?\nYou presumably created the virtualenv using 3.2. Delete it and recreate it with 2.7.\n\nYou shouldn't be \"reading in a forum\" about how to do the Django tutorial. You should just be following the tutorial.","Q_Score":1,"Tags":"python,django,postgresql","A_Id":13495557,"CreationDate":"2012-11-21T14:12:00.000","Title":"postgres installation error on Mac 10.6.8","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Is there a library or open source utility available to search all the tables and columns of an Sqlite database? The only input would be the name of the sqlite DB file.\nI am trying to write a forensics tool and want to search sqlite files for a specific string.","AnswerCount":4,"Available Count":2,"Score":0.2449186624,"is_accepted":false,"ViewCount":15981,"Q_Id":13514509,"Users Score":5,"Answer":"Just dump the db and search it.\n% sqlite3 file_name .dump | grep 'my_search_string'\nYou could instead pipe through less, and then use \/ to search:\n% sqlite3 file_name .dump | less","Q_Score":13,"Tags":"python,sqlite,search","A_Id":65373519,"CreationDate":"2012-11-22T14:11:00.000","Title":"Search Sqlite Database - All Tables and Columns","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Is there a library or open source utility available to search all the tables and columns of an Sqlite database? The only input would be the name of the sqlite DB file.\nI am trying to write a forensics tool and want to search sqlite files for a specific string.","AnswerCount":4,"Available Count":2,"Score":0.1973753202,"is_accepted":false,"ViewCount":15981,"Q_Id":13514509,"Users Score":4,"Answer":"@MrWorf's answer didn't work for my sqlite file (an .exb file from Evernote) but this similar method worked:\n\nOpen the file with DB Browser for SQLite sqlitebrowser mynotes.exb\nFile \/ Export to SQL file (will create mynotes.exb.sql)\ngrep 'STRING I WANT\" mynotes.exb.sql","Q_Score":13,"Tags":"python,sqlite,search","A_Id":59407127,"CreationDate":"2012-11-22T14:11:00.000","Title":"Search Sqlite Database - All Tables and Columns","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have created an app using web2py and have declared certain new table in it using the syntax\ndb.define_table() but the tables created are not visible when I run the app in Google App Engine even on my local server. The tables that web2py creates by itself like auth_user and others in auth are available.\nWhat am I missing here?\nI have declared the new table in db.py in my application.\nThanks in advance","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":100,"Q_Id":13548590,"Users Score":0,"Answer":"App Engine datastore doesn't really have tables. That said, if web2py is able to make use of the datastore (I'm not familiar with it), then Kinds (a bit like tables) will only show up in the admin-console (\/_ah\/admin locally) once an entity has been created (i.e. tables only show up once one row has been inserted, you'll never see empty tables).","Q_Score":1,"Tags":"python,google-app-engine,web2py","A_Id":13551914,"CreationDate":"2012-11-25T05:29:00.000","Title":"New tables created in web2py not seen when running in Google app Engine","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I have a shared hosting environment on Bluehost. I am running a custom installation of python(+ django) with a few installed modules. All has been working, until yesterday a change was made on the server(I assume) which gave me this django error:\n\n... File \"\/****\/****\/.local\/lib\/python\/django\/utils\/importlib.py\", line 35, in import_module\n    __import__(name)\n\nFile \"\/****\/****\/.local\/lib\/python\/django\/db\/backends\/mysql\/base.py\", line 14, in \n    raise ImproperlyConfigured(\"Error loading MySQLdb module: %s\" % e)\n\nImproperlyConfigured: Error loading MySQLdb module: libmysqlclient_r.so.16: cannot open shared object file: No such file or directory\n\nOf course, Bluehost support is not too helpful. They advised that 1) I use the default python install, because that has MySQLdb installed already. Or that 2) I somehow import the MySQLdb package installed on the default python, from my python(dont know if this can even be done). I am concerned that if I use the default install I wont have permission to install my other packages.\nDoes anybody have any ideas how to get back to a working state, with as little infrastructure changes as possible?","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":2446,"Q_Id":13573359,"Users Score":2,"Answer":"I think you upgraded your OS installation which in turn upgraded libmysqlclient and broke native extension. What you can do is reinstall libmysqlclient16 again (how to do it depends your particular OS) and that should fix your issue.\nOther approach would be to uninstall MySQLdb module and reinstall it again, forcing python to compile it against a newer library.","Q_Score":2,"Tags":"python,linux,mysql-python,bluehost","A_Id":13573647,"CreationDate":"2012-11-26T21:20:00.000","Title":"Python module issue","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a shared hosting environment on Bluehost. I am running a custom installation of python(+ django) with a few installed modules. All has been working, until yesterday a change was made on the server(I assume) which gave me this django error:\n\n... File \"\/****\/****\/.local\/lib\/python\/django\/utils\/importlib.py\", line 35, in import_module\n    __import__(name)\n\nFile \"\/****\/****\/.local\/lib\/python\/django\/db\/backends\/mysql\/base.py\", line 14, in \n    raise ImproperlyConfigured(\"Error loading MySQLdb module: %s\" % e)\n\nImproperlyConfigured: Error loading MySQLdb module: libmysqlclient_r.so.16: cannot open shared object file: No such file or directory\n\nOf course, Bluehost support is not too helpful. They advised that 1) I use the default python install, because that has MySQLdb installed already. Or that 2) I somehow import the MySQLdb package installed on the default python, from my python(dont know if this can even be done). I am concerned that if I use the default install I wont have permission to install my other packages.\nDoes anybody have any ideas how to get back to a working state, with as little infrastructure changes as possible?","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":2446,"Q_Id":13573359,"Users Score":0,"Answer":"You were right. Bluehost upgraded MySQL. Here is what I did:\n1) remove the \"build\" directory in the \"MySQL-python-1.2.3\" directory\n2) remove the egg\n3) build the module again \"python setup.py build\"\n4) install the module again \"python setup.py install --prefix=$HOME\/.local\"\nMorale of the story for me is to remove the old stuff when reinstalling module","Q_Score":2,"Tags":"python,linux,mysql-python,bluehost","A_Id":13591200,"CreationDate":"2012-11-26T21:20:00.000","Title":"Python module issue","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm starting a Django project and need to shard multiple tables that are likely to all be of too many rows. I've looked through threads here and elsewhere, and followed the Django multi-db documentation, but am still not sure how that all stitches together. My models have relationships that would be broken by sharding, so it seems like the options are to either drop the foreign keys of forgo sharding the respective models.\nFor argument's sake, consider the classic Authot, Publisher and Book scenario, but throw in book copies and users that can own them. Say books and users had to be sharded. How would you approach that? A user may own a copy of a book that's not in the same database.\nIn general, what are the best practices you have used for routing and the sharding itself? Did you use Django database routers, manually selected a database inside commands based on your sharding logic, or overridden some parts of the ORM to achive that?\nI'm using PostgreSQL on Ubuntu, if it matters.\nMany thanks.","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":1300,"Q_Id":13620867,"Users Score":1,"Answer":"I agree with @DanielRoseman.  Also, how many is too many rows.  If you are careful with indexing, you can handle a lot of rows with no performance problems.  Keep your indexed values small (ints).  I've got tables in excess of 400 million rows that produce sub-second responses even when joining with other many million row tables.  \nIt might make more sense to break user up into multiple tables so that the user object has a core of commonly used things and then the \"profile\" info lives elsewhere (std Django setup).  Copies would be a small table referencing books which has the bulk of the data.  Considering how much ram you can put into a DB server these days, sharding before you have too seems wrong.","Q_Score":3,"Tags":"python,django,postgresql,sharding","A_Id":13639532,"CreationDate":"2012-11-29T07:32:00.000","Title":"Sharding a Django Project","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am connecting my python software to a remote msql server.\ni have had to add an access host on cPanel just for my computer but the problem is the access host, which is my IP, is dynamic.\nHow can i connect to the remote server without having to change the access host everytime?\nthanks guys, networking is my weakness.","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1475,"Q_Id":13657404,"Users Score":0,"Answer":"Your best option is probably to find a [dynamic DNS] provider. The idea is to have a client running on your machine which updates a DNS entry on a remote server. Then you can use the hostname provided instead of your IP address in cPanel.","Q_Score":0,"Tags":"python,networking,cpanel","A_Id":13657435,"CreationDate":"2012-12-01T07:31:00.000","Title":"Configuring Remote MYSQL with a Dynamic IP","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm familiar with LAMP systems and have been programming mostly in PHP for the past 4 years. I'm learning Python and playing around with Nginx a little bit.\nWe're working on a project website which will handle a lot of http handle requests, stream videos(mostly from a provider like youtube or vimeo). My colleague has experience with OpenBSD and has insisted that we use it as an alternative to linux.\n\nThe reason that we want to use OpenBSD is that it's well known for\nit's security.\nThe reason we chose Python is that it's fast.\nThe reason we want to use Nginx is that it's known to be able to\nhandle more http request when compared to Apache.\nThe reason we want to use NoSQL is that MySQL is known to have\nproblems in scalability when the databases grows.\n\nWe want the web pages to load as fast as possible (caching and cdn's will be used) using the minimum amount of hardware possible. That's why we want to use ONPN (OpenBSD,Nginx,Python,Nosql) instead of the traditional LAMP (Linux,Apache,Mysql,PHP).\nWe're not a very big company so we're using opensource technologies. Any suggestion is appreciated on how to use these software as a platform and giving hardware suggestions is also appreciated. Any criticism is also welcomed.","AnswerCount":2,"Available Count":2,"Score":0.3799489623,"is_accepted":false,"ViewCount":1447,"Q_Id":13675440,"Users Score":4,"Answer":"My advice - if you don't know how to use these technologies - don't do it. Few servers will cost you less than the time spent mastering technologies you don't know. If you want to try them out - do it. One by one, not everything at once. There is no magic solution on how to use them.","Q_Score":1,"Tags":"python,nginx,nosql,openbsd","A_Id":13675611,"CreationDate":"2012-12-03T00:05:00.000","Title":"How to utilize OpenBSD, Nginx, Python and NoSQL","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm familiar with LAMP systems and have been programming mostly in PHP for the past 4 years. I'm learning Python and playing around with Nginx a little bit.\nWe're working on a project website which will handle a lot of http handle requests, stream videos(mostly from a provider like youtube or vimeo). My colleague has experience with OpenBSD and has insisted that we use it as an alternative to linux.\n\nThe reason that we want to use OpenBSD is that it's well known for\nit's security.\nThe reason we chose Python is that it's fast.\nThe reason we want to use Nginx is that it's known to be able to\nhandle more http request when compared to Apache.\nThe reason we want to use NoSQL is that MySQL is known to have\nproblems in scalability when the databases grows.\n\nWe want the web pages to load as fast as possible (caching and cdn's will be used) using the minimum amount of hardware possible. That's why we want to use ONPN (OpenBSD,Nginx,Python,Nosql) instead of the traditional LAMP (Linux,Apache,Mysql,PHP).\nWe're not a very big company so we're using opensource technologies. Any suggestion is appreciated on how to use these software as a platform and giving hardware suggestions is also appreciated. Any criticism is also welcomed.","AnswerCount":2,"Available Count":2,"Score":0.0996679946,"is_accepted":false,"ViewCount":1447,"Q_Id":13675440,"Users Score":1,"Answer":"I agree with wdev, the time it takes to learn this is not worth the money you will save. First of all, MySQL databases are not hard to scale. WordPress utilizes MySQL databases, and some of the world's largest websites use MySQL (google for a list). I can also say the same of linux and PHP. \nIf you design your site using best practices (CSS sprites) Apache versus Nginx will not make a considerable difference in load times if you utilize a CDN and best practices (caching, gzip, etc).\nI strongly urge you to reconsider your decisions. They seem very ill-advised.","Q_Score":1,"Tags":"python,nginx,nosql,openbsd","A_Id":13676002,"CreationDate":"2012-12-03T00:05:00.000","Title":"How to utilize OpenBSD, Nginx, Python and NoSQL","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a list of times in h:m format in an Excel spreadsheet, and I'm trying to do some manipulation with DataNitro but it doesn't seem to like the way Excel formats times.\nFor example, in Excel the time 8:32 is actually just the decimal number .355556 formatted to appear as 8:32. When I access that time with DataNitro it sees it as the decimal, not the string 8:32. If I change the format in Excel from Time to General or Number, it converts it to the decimal (which I don't want). The only thing I've found that works is manually going through each cell and placing ' in front of each one, then going through and changing the format type to General.  \nIs there any way to convert these times in Excel into strings so I can extract the info with DataNitro (which is only viewing it as a decimal)?","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":488,"Q_Id":13725567,"Users Score":3,"Answer":"If .355556 (represented as 8:32) is in A1 then =HOUR(A1)&\":\"&MINUTE(A1) and Copy\/Paste Special Values should get you to a string.","Q_Score":1,"Tags":"python,excel,time,number-formatting,datanitro","A_Id":13725706,"CreationDate":"2012-12-05T14:35:00.000","Title":"Converting time with Python and DataNitro in Excel","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I've implemented a breadth first search with a PyMongo social network. It's breadth first to reduce the number of connections. Now I get queries like coll.find({\"_id\":{\"$in\":[\"id1\", \"id2\", ...]}} with a huge number of ids. PyMongo does not process some of these big queries due to their size.\nIs there a technical solution around it? Or do you suggest another approach to such kind of queries where I need to select all docs with one of a huge set of ids?","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":116,"Q_Id":13728955,"Users Score":0,"Answer":"If this is an inescapable problem, you could split the array of ids across multiple queries and then merge the results client-side.","Q_Score":0,"Tags":"python,mongodb","A_Id":13729295,"CreationDate":"2012-12-05T17:27:00.000","Title":"Large size query with PyMongo?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"So I am trying to create a realtime plot of data that is being recorded to a SQL server.  The format is as follows:\nDatabase: testDB\nTable: sensors\nFirst record contains 3 records.  The first column is an auto incremented ID starting at 1.  The second column is the time in epoch format.  The third column is my sensor data.  It is in the following format:\n23432.32 112343.3 53454.322 34563.32 76653.44 000.000 333.2123\nI am completely lost on how to complete this project.  I have read many pages showing examples dont really understand them.  They provide source code, but I am not sure where that code goes.  I installed httpd on my server and that is where I stand.  Does anyone know of a good how-to from beginning to end that I could follow?  Or could someone post a good step by step for me to follow?\nThanks for your help","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":428,"Q_Id":13772857,"Users Score":0,"Answer":"Install a httpd server\nInstall php\nWrite a php script to fetch the data from the database and render it\nas a webpage.\n\nThis is fairly elaborate request, with relatively little details given.  More information will allow us to give better answers.","Q_Score":0,"Tags":"python,mysql,flot","A_Id":13774224,"CreationDate":"2012-12-07T23:52:00.000","Title":"Plotting data using Flot and MySQL","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I need to obtain path from a FileField, in order to check it against a given file system path, to know if the file I am inserting into mongo database is already present.\nIs it possible?\nAll I get is a GridFSProxy, but I am unable to understand how to handle it.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":430,"Q_Id":13791542,"Users Score":1,"Answer":"You can't since it stores the data into database. If you need to store the original path then you can create an EmbeddedDocument which contains a FileField and a StringField with the path string. But remember that the stored file and the file you might find on that path are not the same","Q_Score":0,"Tags":"python,mongodb,path,mongoengine,filefield","A_Id":13962502,"CreationDate":"2012-12-09T20:34:00.000","Title":"How to get filesystem path from mongoengine FileField","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am using psycopg2 in python, but my question is DBMS agnostic (as long as the DBMS supports transactions):\nI am writing a python program that inserts records into a database table. The number of records to be inserted is more than a million. When I wrote my code so that it ran a commit on each insert statement, my program was too slow. Hence, I altered my code to run a commit every 5000 records and the difference in speed was tremendous.\nMy problem is that at some point an exception occurs when inserting records (some integrity check fails) and I wish to commit my changes up to that point, except of course for the last command that caused the exception to happen, and continue with the rest of my insert statements.\nI haven't found a way to achieve this; the only thing I've achieved was to capture the exception, rollback my transaction and keep on from that point, where I loose my pending insert statements. Moreover, I tried (deep)copying the cursor object and the connection object without any luck, either.\nIs there a way to achieve this functionality, either directly or indirectly, without having to rollback and recreate\/re-run my statements?\nThank you all in advance,\nGeorge.","AnswerCount":2,"Available Count":2,"Score":0.1973753202,"is_accepted":false,"ViewCount":1119,"Q_Id":13838231,"Users Score":2,"Answer":"If you are committing your transactions after every 5000 record interval, it seems like you could do a little bit of preprocessing of your input data and actually break it out into a list of 5000 record chunks, i.e. [[[row1_data],[row2_data]...[row4999_data]],[[row5000_data],[row5001_data],...],[[....[row1000000_data]]]\nThen run your inserts, and keep track of which chunk you are processing as well as which record you are currently inserting. When you get the error, you rerun the chunk, but skip the the offending record.","Q_Score":1,"Tags":"python,postgresql,transactions,commit,psycopg2","A_Id":13849917,"CreationDate":"2012-12-12T10:58:00.000","Title":"How can I commit all pending queries until an exception occurs in a python connection object","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am using psycopg2 in python, but my question is DBMS agnostic (as long as the DBMS supports transactions):\nI am writing a python program that inserts records into a database table. The number of records to be inserted is more than a million. When I wrote my code so that it ran a commit on each insert statement, my program was too slow. Hence, I altered my code to run a commit every 5000 records and the difference in speed was tremendous.\nMy problem is that at some point an exception occurs when inserting records (some integrity check fails) and I wish to commit my changes up to that point, except of course for the last command that caused the exception to happen, and continue with the rest of my insert statements.\nI haven't found a way to achieve this; the only thing I've achieved was to capture the exception, rollback my transaction and keep on from that point, where I loose my pending insert statements. Moreover, I tried (deep)copying the cursor object and the connection object without any luck, either.\nIs there a way to achieve this functionality, either directly or indirectly, without having to rollback and recreate\/re-run my statements?\nThank you all in advance,\nGeorge.","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":1119,"Q_Id":13838231,"Users Score":3,"Answer":"I doubt you'll find a fast cross-database way to do this. You just have to optimize the balance between the speed gains from batch size and the speed costs of repeating work when an entry causes a batch to fail.\nSome DBs can continue with a transaction after an error, but PostgreSQL can't. However, it does allow you to create subtransactions with the SAVEPOINT command. These are far from free, but they're lower cost than a full transaction. So what you can do is every (say) 100 rows, issue a SAVEPOINT and then release the prior savepoint. If you hit an error, ROLLBACK TO SAVEPOINT, commit, then pick up where you left off.","Q_Score":1,"Tags":"python,postgresql,transactions,commit,psycopg2","A_Id":13838751,"CreationDate":"2012-12-12T10:58:00.000","Title":"How can I commit all pending queries until an exception occurs in a python connection object","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm building a file hosting app that will store all client files within a folder on an S3 bucket. I then want to track the amount of usage on S3 recursively per top folder to charge back the cost of storage and bandwidth to each corresponding client. \nFront-end is django but the solution can be python for obvious reasons.\nIs it better to create a bucket per client programmatically?\nIf I do go with the approach of creating a bucket per client, is it then possible to get the cost of cloudfront exposure of the bucket if enabled?","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":818,"Q_Id":13873119,"Users Score":0,"Answer":"No its not possible to create a bucket for each user as Amazon allows only 100 buckets per account. So unless you are sure not to have more than 100 users, it will be a very bad idea.\nThe ideal solution will be to remember each user's storage in you Django app itself in database. I guess you would be using S3 boto library for storing the files, than it returns the byte size after each upload. You can use that to store that.\nThere is also another way out, you could create many folders inside a bucket with each folder specific to an user. But still the best way to remember the storage usage in your app","Q_Score":0,"Tags":"python,django,amazon-s3","A_Id":13892252,"CreationDate":"2012-12-14T05:20:00.000","Title":"How can I track s3 bucket folder usage with python?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":1,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"How would I extend the sqlite3 module so if I import Database I can do Database.connect() as an alias to sqlite3.connect(), but define extra non standard methods?","AnswerCount":2,"Available Count":1,"Score":0.3799489623,"is_accepted":false,"ViewCount":206,"Q_Id":13881533,"Users Score":4,"Answer":"You can create a class which wraps sqlite3. It takes its .connect() method and maybe others and exposes it to the outside, and then you add your own stuff.\nAnother option would be subclassing - if that works.","Q_Score":1,"Tags":"python,sqlite","A_Id":13881814,"CreationDate":"2012-12-14T15:24:00.000","Title":"How do I extend a python module to include extra functionality? (sqlite3)","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I`m trying to write loader to sqlite that will load as fast as possible simple rows in DB.\nInput data looks like rows retrieved from postgres DB. Approximated amount of rows that will go to sqlite: from 20mil to 100mil.\nI cannot use other DB except sqlite due to project restrictions.\nMy question is :\nwhat is a proper logic to write such loader?\nAt first try I`ve tried to write set of encapsulated generators, that will take one row from Postgres, slightly ammend it and put it into sqlite. I ended up with the fact that for each row, i create separate sqlite connection and cursor. And that looks awfull.\nAt second try , i moved sqlite connection and cursor out of the generator , to the body of the script  and it became clear that i do not commit data to sqlite untill i fetch and process all 20mils records. And this possibly could crash all my hardware.\nAt third try I strated to consider to keep Sqlite connection away from the loops , but create\/close cursor each time i process  and push one row to Sqlite. This is better but i think also have some overhead.\nI also considered to play with transactions : One connection, one cursor, one transaction and commit called  in generator each time row is being pushed to Sqlite. Is this i right way i`m going? \nIs there some widely-used pattern to write such a component in python? Because I feel as if I am inventing a bicycle.","AnswerCount":3,"Available Count":2,"Score":0.0665680765,"is_accepted":false,"ViewCount":293,"Q_Id":13919448,"Users Score":1,"Answer":"SQLite can handle huge transactions with ease, so why not commit at the end? Have you tried this at all?\nIf you do feel one transaction is a problem, why not commit ever n transactions? Process rows one by one, insert as needed, but every n executed insertions add a connection.commit() to spread the load.","Q_Score":0,"Tags":"python,sqlite,python-2.7","A_Id":13919496,"CreationDate":"2012-12-17T17:56:00.000","Title":"How to write proper big data loader to sqlite","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I`m trying to write loader to sqlite that will load as fast as possible simple rows in DB.\nInput data looks like rows retrieved from postgres DB. Approximated amount of rows that will go to sqlite: from 20mil to 100mil.\nI cannot use other DB except sqlite due to project restrictions.\nMy question is :\nwhat is a proper logic to write such loader?\nAt first try I`ve tried to write set of encapsulated generators, that will take one row from Postgres, slightly ammend it and put it into sqlite. I ended up with the fact that for each row, i create separate sqlite connection and cursor. And that looks awfull.\nAt second try , i moved sqlite connection and cursor out of the generator , to the body of the script  and it became clear that i do not commit data to sqlite untill i fetch and process all 20mils records. And this possibly could crash all my hardware.\nAt third try I strated to consider to keep Sqlite connection away from the loops , but create\/close cursor each time i process  and push one row to Sqlite. This is better but i think also have some overhead.\nI also considered to play with transactions : One connection, one cursor, one transaction and commit called  in generator each time row is being pushed to Sqlite. Is this i right way i`m going? \nIs there some widely-used pattern to write such a component in python? Because I feel as if I am inventing a bicycle.","AnswerCount":3,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":293,"Q_Id":13919448,"Users Score":0,"Answer":"Finally i managed to resolve my problem. Main issue was in exessive amount of insertions in sqlite. After i started to load all data from postgress to memory, aggregate it proper way to reduce amount of rows,  i was able to  decrease processing time from  60 hrs to 16 hrs.","Q_Score":0,"Tags":"python,sqlite,python-2.7","A_Id":13976529,"CreationDate":"2012-12-17T17:56:00.000","Title":"How to write proper big data loader to sqlite","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm attempting to install MySQL-python on a machine running CentOS 5.5 and python 2.7.  This machine isn't running a mysql server, the mysql instance this box will be using is hosted on a separate server.  I do have a working mysql client.  On attempting sudo pip install MySQL-python, I get an error of EnvironmentError: mysql_config not found, which as far as I can tell is a command that just references \/etc\/my.cnf, which also isn't present.  Before I go on some wild goose chase creating spurious my.cnf files, is there an easy way to get MySQL-python installed?","AnswerCount":3,"Available Count":1,"Score":1.0,"is_accepted":false,"ViewCount":27898,"Q_Id":13922955,"Users Score":21,"Answer":"So it transpires that mysql_config is part of mysql-devel.  mysql-devel is for compiling the mysql client, not the server.  Installing mysql-devel allows the installation of MySQL-python.","Q_Score":13,"Tags":"centos,mysql-python","A_Id":13932070,"CreationDate":"2012-12-17T22:01:00.000","Title":"Installing MySQL-python without mysql-server on CentOS","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":0},{"Question":"trying to figure out whether this is a bug or by design. when no query_string is specified for a query, the SearchResults object is NOT sorted by the requested column. for example, here is some logging to show the problem:\nResults are returned unsorted on return index.search(query):\nquery_string = ''\nsort_options string: search.SortOptions(expressions=[search.SortExpression(expression=u'firstname', direction='ASCENDING', default_value=u'')], limit=36)\nResults are returned sorted on return index.search(query):\nquery_string = 'test'\nsort_options string: search.SortOptions(expressions=[search.SortExpression(expression=u'firstname', direction='ASCENDING', default_value=u'')], limit=36)\nThis is how I'm constructing my query for both cases (options has limit, offset and sort_options parameters):\nquery = search.Query(query_string=query_string, options=options)","AnswerCount":2,"Available Count":1,"Score":-0.1973753202,"is_accepted":false,"ViewCount":103,"Q_Id":13953039,"Users Score":-2,"Answer":"Could be a bug in the way you build your query, since it's not shown.\nCould be that you don't have an index for the case that isn't working.","Q_Score":8,"Tags":"python,google-app-engine,gae-search","A_Id":13954922,"CreationDate":"2012-12-19T13:02:00.000","Title":"sort_options only applied when query_string is not empty?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Im getting this error when trying to run python \/ django after installing psycopg2:\nError: dlopen(\/Users\/macbook\/Envs\/medint\/lib\/python2.7\/site-packages\/psycopg2\/_psycopg.so, 2): Symbol not found: _PQbackendPID\n  Referenced from: \/Users\/macbook\/Envs\/medint\/lib\/python2.7\/site-packages\/psycopg2\/_psycopg.so\n  Expected in: dynamic lookup\nAnyone?","AnswerCount":2,"Available Count":1,"Score":1.0,"is_accepted":false,"ViewCount":3182,"Q_Id":14001116,"Users Score":6,"Answer":"on Mojave macOS, I solved it by running below steps:\n\npip uninstall psycopg2 \npip install psycopg2-binary","Q_Score":1,"Tags":"python,django,postgresql,heroku,psycopg2","A_Id":59063813,"CreationDate":"2012-12-22T08:02:00.000","Title":"Psycopg2 Symbol not found: _PQbackendPID Expected in: dynamic lookup","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm a python developer with pretty good RDBMS experience.  I need to process a fairly large amount of data (approx 500GB).  The data is sitting in approximately 1200 csv files in s3 buckets.  I have written a script in Python and can run it on a server.  However, it is way too slow.  Based on the current speed and the amount of data it will take approximately 50 days to get through all of the files (and of course, the deadline is WELL before that).\nNote: the processing is sort of your basic ETL type of stuff - nothing terrible fancy.  I could easily just pump it into a temp schema in PostgreSQL, and then run scripts onto of it.  But, again, from my initial testing, this would be way to slow.\nNote: A brand new PostgreSQL 9.1 database will be it's final destination.\nSo, I was thinking about trying to spin up a bunch of EC2 instances to try and run them in batches (in parallel).  But, I have never done something like this before so I've been looking around for ideas, etc. \nAgain, I'm a python developer, so it seems like Fabric + boto might be promising. I have used boto from time to time, but never any experience with Fabric.\nI know from reading\/research this is probably a great job for Hadoop, but I don't know it and can't afford to hire it done, and the time line doesn't allow for a learning curve or hiring someone.  I should also not, that it's kind of a one time deal.  So, I don't need to build a really elegant solution.  I just need for it to work and be able to get through all of the data by the end of the year.\nAlso, I know this is not a simple stackoverflow-kind of question (something like \"how can I reverse a list in python\").  But, what I'm hoping for is someone to read this and \"say, I do something similar and use XYZ...  it's great!\"\nI guess what I'm asking is does anybody know of any thing out there that I could use to accomplish this task (given that I'm a Python developer and I don't know Hadoop or Java - and have a tight timeline that prevents me learning a new technology like Hadoop or learning a new language) \nThanks for reading.  I look forward to any suggestions.","AnswerCount":5,"Available Count":4,"Score":1.2,"is_accepted":true,"ViewCount":1819,"Q_Id":14006363,"Users Score":2,"Answer":"I often use a combination of SQS\/S3\/EC2 for this type of batch work.  Queue up messages in SQS for all of the work that needs to be performed (chunked into some reasonably small chunks).  Spin up N EC2 instances that are configured to start reading messages from SQS, performing the work and putting results into S3, and then, and only then, delete the message from SQS.\nYou can scale this to crazy levels and it has always worked really well for me.  In your case, I don't know if you would store results in S3 or go right to PostgreSQL.","Q_Score":5,"Tags":"python,fabric,boto,data-processing","A_Id":14012685,"CreationDate":"2012-12-22T20:30:00.000","Title":"Processing a large amount of data in parallel","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm a python developer with pretty good RDBMS experience.  I need to process a fairly large amount of data (approx 500GB).  The data is sitting in approximately 1200 csv files in s3 buckets.  I have written a script in Python and can run it on a server.  However, it is way too slow.  Based on the current speed and the amount of data it will take approximately 50 days to get through all of the files (and of course, the deadline is WELL before that).\nNote: the processing is sort of your basic ETL type of stuff - nothing terrible fancy.  I could easily just pump it into a temp schema in PostgreSQL, and then run scripts onto of it.  But, again, from my initial testing, this would be way to slow.\nNote: A brand new PostgreSQL 9.1 database will be it's final destination.\nSo, I was thinking about trying to spin up a bunch of EC2 instances to try and run them in batches (in parallel).  But, I have never done something like this before so I've been looking around for ideas, etc. \nAgain, I'm a python developer, so it seems like Fabric + boto might be promising. I have used boto from time to time, but never any experience with Fabric.\nI know from reading\/research this is probably a great job for Hadoop, but I don't know it and can't afford to hire it done, and the time line doesn't allow for a learning curve or hiring someone.  I should also not, that it's kind of a one time deal.  So, I don't need to build a really elegant solution.  I just need for it to work and be able to get through all of the data by the end of the year.\nAlso, I know this is not a simple stackoverflow-kind of question (something like \"how can I reverse a list in python\").  But, what I'm hoping for is someone to read this and \"say, I do something similar and use XYZ...  it's great!\"\nI guess what I'm asking is does anybody know of any thing out there that I could use to accomplish this task (given that I'm a Python developer and I don't know Hadoop or Java - and have a tight timeline that prevents me learning a new technology like Hadoop or learning a new language) \nThanks for reading.  I look forward to any suggestions.","AnswerCount":5,"Available Count":4,"Score":0.0399786803,"is_accepted":false,"ViewCount":1819,"Q_Id":14006363,"Users Score":1,"Answer":"You might benefit from hadoop in form of Amazon Elastic Map Reduce. Without getting too deep it can be seen as a way to apply some logic to massive data volumes in parralel (Map stage).\nThere is also hadoop technology called hadoop streaming - which enables to use scripts \/ executables in any languages (like python). \nAnother hadoop technology you can find useful is sqoop - which moves data between HDFS and RDBMS.","Q_Score":5,"Tags":"python,fabric,boto,data-processing","A_Id":14009860,"CreationDate":"2012-12-22T20:30:00.000","Title":"Processing a large amount of data in parallel","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm a python developer with pretty good RDBMS experience.  I need to process a fairly large amount of data (approx 500GB).  The data is sitting in approximately 1200 csv files in s3 buckets.  I have written a script in Python and can run it on a server.  However, it is way too slow.  Based on the current speed and the amount of data it will take approximately 50 days to get through all of the files (and of course, the deadline is WELL before that).\nNote: the processing is sort of your basic ETL type of stuff - nothing terrible fancy.  I could easily just pump it into a temp schema in PostgreSQL, and then run scripts onto of it.  But, again, from my initial testing, this would be way to slow.\nNote: A brand new PostgreSQL 9.1 database will be it's final destination.\nSo, I was thinking about trying to spin up a bunch of EC2 instances to try and run them in batches (in parallel).  But, I have never done something like this before so I've been looking around for ideas, etc. \nAgain, I'm a python developer, so it seems like Fabric + boto might be promising. I have used boto from time to time, but never any experience with Fabric.\nI know from reading\/research this is probably a great job for Hadoop, but I don't know it and can't afford to hire it done, and the time line doesn't allow for a learning curve or hiring someone.  I should also not, that it's kind of a one time deal.  So, I don't need to build a really elegant solution.  I just need for it to work and be able to get through all of the data by the end of the year.\nAlso, I know this is not a simple stackoverflow-kind of question (something like \"how can I reverse a list in python\").  But, what I'm hoping for is someone to read this and \"say, I do something similar and use XYZ...  it's great!\"\nI guess what I'm asking is does anybody know of any thing out there that I could use to accomplish this task (given that I'm a Python developer and I don't know Hadoop or Java - and have a tight timeline that prevents me learning a new technology like Hadoop or learning a new language) \nThanks for reading.  I look forward to any suggestions.","AnswerCount":5,"Available Count":4,"Score":0.1194272985,"is_accepted":false,"ViewCount":1819,"Q_Id":14006363,"Users Score":3,"Answer":"Did you do some performance measurements: Where are the bottlenecks? Is it CPU bound, IO bound, DB bound?\nWhen it is CPU bound, you can try a python JIT like pypy.\nWhen it is IO bound, you need more HDs (and put some striping md on them).\nWhen it is DB bound, you can try to drop all the indexes and keys first.\nLast week I imported the Openstreetmap DB into a postgres instance on my server. The input data were about 450G.  The preprocessing (which was done in JAVA here) just created the raw data files which could be imported with postgres 'copy' command.  After importing the keys and indices were generated.\nImporting all the raw data took about one day - and then it took several days to build keys and indices.","Q_Score":5,"Tags":"python,fabric,boto,data-processing","A_Id":14006535,"CreationDate":"2012-12-22T20:30:00.000","Title":"Processing a large amount of data in parallel","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm a python developer with pretty good RDBMS experience.  I need to process a fairly large amount of data (approx 500GB).  The data is sitting in approximately 1200 csv files in s3 buckets.  I have written a script in Python and can run it on a server.  However, it is way too slow.  Based on the current speed and the amount of data it will take approximately 50 days to get through all of the files (and of course, the deadline is WELL before that).\nNote: the processing is sort of your basic ETL type of stuff - nothing terrible fancy.  I could easily just pump it into a temp schema in PostgreSQL, and then run scripts onto of it.  But, again, from my initial testing, this would be way to slow.\nNote: A brand new PostgreSQL 9.1 database will be it's final destination.\nSo, I was thinking about trying to spin up a bunch of EC2 instances to try and run them in batches (in parallel).  But, I have never done something like this before so I've been looking around for ideas, etc. \nAgain, I'm a python developer, so it seems like Fabric + boto might be promising. I have used boto from time to time, but never any experience with Fabric.\nI know from reading\/research this is probably a great job for Hadoop, but I don't know it and can't afford to hire it done, and the time line doesn't allow for a learning curve or hiring someone.  I should also not, that it's kind of a one time deal.  So, I don't need to build a really elegant solution.  I just need for it to work and be able to get through all of the data by the end of the year.\nAlso, I know this is not a simple stackoverflow-kind of question (something like \"how can I reverse a list in python\").  But, what I'm hoping for is someone to read this and \"say, I do something similar and use XYZ...  it's great!\"\nI guess what I'm asking is does anybody know of any thing out there that I could use to accomplish this task (given that I'm a Python developer and I don't know Hadoop or Java - and have a tight timeline that prevents me learning a new technology like Hadoop or learning a new language) \nThanks for reading.  I look forward to any suggestions.","AnswerCount":5,"Available Count":4,"Score":0.0798297691,"is_accepted":false,"ViewCount":1819,"Q_Id":14006363,"Users Score":2,"Answer":"I did something like this some time ago, and my setup was like\n\none multicore instance (x-large or more), that converts raw source files (xml\/csv) into an intermediate format. You can run (num-of-cores) copies of the convertor script on it in parallel.  Since my target was mongo, I used json as an intermediate format, in your case it will be sql.\nthis instance has N volumes attached to it. Once a volume becomes full, it gets detached and attached to the second instance (via boto).\nthe second instance runs a DBMS server and a script which imports prepared (sql) data into the db. I don't know anything about postgres, but I guess it does have a tool like mysql or mongoimport. If yes, use that to make bulk inserts instead of making queries via a python script.","Q_Score":5,"Tags":"python,fabric,boto,data-processing","A_Id":14006466,"CreationDate":"2012-12-22T20:30:00.000","Title":"Processing a large amount of data in parallel","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"So, a friend and I are currently writing a panel (in python\/django) for managing gameservers.\nEach client also gets a MySQL server with their game server. What we are stuck on at the moment is how clients will find out their MySQL password and how it will be 'stored'.\nThe passwords would be generated randomly and presented to the user in the panel, however, we obviously don't want them to be stored in plaintext or reversible encryption, so we are unsure what to do if a a client forgets their password.\nResetting the password is something we would try to avoid as some clients may reset the password while the gameserver is still trying to use it, which could cause corruption and crashes.\nWhat would be a secure (but without sacrificing ease of use for the clients) way to go about this?","AnswerCount":2,"Available Count":2,"Score":0.0996679946,"is_accepted":false,"ViewCount":408,"Q_Id":14008232,"Users Score":1,"Answer":"Your question embodies a contradiction in terms. Either you don't want reversibility or you do. You will have to choose.\nThe usual technique is to hash the passwords and to provide a way for the user to reset his own password on sufficient alternative proof of identity. You should never display a password to anybody, for legal non-repudiability reasons. If you don't know what that means, ask a lawyer.","Q_Score":2,"Tags":"python,mysql,django,security,encryption","A_Id":14008320,"CreationDate":"2012-12-23T02:46:00.000","Title":"Storing MySQL Passwords","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"So, a friend and I are currently writing a panel (in python\/django) for managing gameservers.\nEach client also gets a MySQL server with their game server. What we are stuck on at the moment is how clients will find out their MySQL password and how it will be 'stored'.\nThe passwords would be generated randomly and presented to the user in the panel, however, we obviously don't want them to be stored in plaintext or reversible encryption, so we are unsure what to do if a a client forgets their password.\nResetting the password is something we would try to avoid as some clients may reset the password while the gameserver is still trying to use it, which could cause corruption and crashes.\nWhat would be a secure (but without sacrificing ease of use for the clients) way to go about this?","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":408,"Q_Id":14008232,"Users Score":4,"Answer":"Though this is not the answer you were looking for, you only have three possibilities\n\nstore the passwords plaintext (ugh!)\nstore with a reversible encryption, e.g. RSA (http:\/\/stackoverflow.com\/questions\/4484246\/encrypt-and-decrypt-text-with-rsa-in-php)\ndo not store it; clients can only reset password, not view it\n\nThe second choice is a secure way, as RSA is also used for TLS encryption within the HTTPS protocol used by your bank of choice ;)","Q_Score":2,"Tags":"python,mysql,django,security,encryption","A_Id":14008264,"CreationDate":"2012-12-23T02:46:00.000","Title":"Storing MySQL Passwords","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am writing myself a blog in python, and am to put it up to GitHub.\nOne of the file in this project will be a script that create the required tables in DB at the very beginning. Since I've gonna put this file on a public repository, I expose all DB structure.\nIs it dangerous if I do so? \nIf yes, I am thinking of an alternative to put column names in a separate config file and not upload column names of my blog. What are others ways of avoiding exposing schemas?","AnswerCount":3,"Available Count":3,"Score":0.1973753202,"is_accepted":false,"ViewCount":599,"Q_Id":14039877,"Users Score":3,"Answer":"It's not dangerous if you secure access to database. You are exposing only your know-how. Once somebody gains access to database, it's easy to list database structure.","Q_Score":2,"Tags":"python,database,open-source,schema,database-schema","A_Id":14039904,"CreationDate":"2012-12-26T11:20:00.000","Title":"Is it dangerous if I expose my database schema in an open source project?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am writing myself a blog in python, and am to put it up to GitHub.\nOne of the file in this project will be a script that create the required tables in DB at the very beginning. Since I've gonna put this file on a public repository, I expose all DB structure.\nIs it dangerous if I do so? \nIf yes, I am thinking of an alternative to put column names in a separate config file and not upload column names of my blog. What are others ways of avoiding exposing schemas?","AnswerCount":3,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":599,"Q_Id":14039877,"Users Score":0,"Answer":"There is a difference between sharing database and database schema.\nYou can comment the values of database machine\/username\/password in your code and publish the code on github.\nAs a proof of concept, you can host your application on cloud(without disclosing its database credentials) and add its link to your github readme file.","Q_Score":2,"Tags":"python,database,open-source,schema,database-schema","A_Id":14039945,"CreationDate":"2012-12-26T11:20:00.000","Title":"Is it dangerous if I expose my database schema in an open source project?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am writing myself a blog in python, and am to put it up to GitHub.\nOne of the file in this project will be a script that create the required tables in DB at the very beginning. Since I've gonna put this file on a public repository, I expose all DB structure.\nIs it dangerous if I do so? \nIf yes, I am thinking of an alternative to put column names in a separate config file and not upload column names of my blog. What are others ways of avoiding exposing schemas?","AnswerCount":3,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":599,"Q_Id":14039877,"Users Score":0,"Answer":"I think it is dangerous, as if  a SQL injection vulnerability exists in your website, the scheme will help the attacker to retrieve all important data easier.","Q_Score":2,"Tags":"python,database,open-source,schema,database-schema","A_Id":21087156,"CreationDate":"2012-12-26T11:20:00.000","Title":"Is it dangerous if I expose my database schema in an open source project?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Need a way to improve performance on my website's SQL based Activity Feed.  We are using Django on Heroku.\nRight now we are using actstream, which is a Django App that implements an activity feed using Generic Foreign Keys in the Django ORM.  Basically, every action has generic foreign keys to its actor and to any objects that it might be acting on, like this:\nAction:\n  (Clay - actor) wrote a (comment - action object) on (Andrew's review of Starbucks - target)\nAs we've scaled, its become way too slow, which is understandable because it relies on big, expensive SQL joins.\nI see at least two options: \n\nPut a Redis layer on top of the SQL database and get activity feeds from there.  \nTry to circumvent the Django ORM and do all the queries in raw SQL, which I understand can improve performance.\n\nAny one have thoughts on either of these two, or other ideas, I'd love to hear them.","AnswerCount":3,"Available Count":2,"Score":0.0665680765,"is_accepted":false,"ViewCount":499,"Q_Id":14073030,"Users Score":1,"Answer":"You said redis? Everything is better with redis.\nCaching is one of the best ideas in software development, no mather if you use Materialized Views you should also consider trying to cache those, believe me your users will notice the difference.","Q_Score":4,"Tags":"python,sql,django,redis,feed","A_Id":14074169,"CreationDate":"2012-12-28T17:04:00.000","Title":"Good way to make a SQL based activity feed faster","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Need a way to improve performance on my website's SQL based Activity Feed.  We are using Django on Heroku.\nRight now we are using actstream, which is a Django App that implements an activity feed using Generic Foreign Keys in the Django ORM.  Basically, every action has generic foreign keys to its actor and to any objects that it might be acting on, like this:\nAction:\n  (Clay - actor) wrote a (comment - action object) on (Andrew's review of Starbucks - target)\nAs we've scaled, its become way too slow, which is understandable because it relies on big, expensive SQL joins.\nI see at least two options: \n\nPut a Redis layer on top of the SQL database and get activity feeds from there.  \nTry to circumvent the Django ORM and do all the queries in raw SQL, which I understand can improve performance.\n\nAny one have thoughts on either of these two, or other ideas, I'd love to hear them.","AnswerCount":3,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":499,"Q_Id":14073030,"Users Score":1,"Answer":"Went with an approach that sort of combined the two suggestions.\nWe created a master list of every action in the database, which included all the information we needed about the actions, and stuck it in Redis.  Given an action ID, we can now do a Redis look up on it and get a dictionary object that is ready to be returned to the front end.\nWe also created action id lists that correspond to all the different types of activity streams that are available to a user.  So given a user id, we have his friends' activity, his own activity, favorite places activity, etc, available for look up.  (These I guess correspond somewhat to materialized views, although they are in Redis, not in PSQL.)\nSo we get a user's feed as a list of action ids.  Then we get the details of those actions by look ups on the ids in the master action list.  Then we return the feed to the front end.\nThanks for the suggestions, guys.","Q_Score":4,"Tags":"python,sql,django,redis,feed","A_Id":14201647,"CreationDate":"2012-12-28T17:04:00.000","Title":"Good way to make a SQL based activity feed faster","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I would like to know as to where is the value stored for a one2many table initially in OpenERP6.1?\ni.e if we create a record for a one2many table,this record will be actually\nsaved to the database table only after saving the record of the main table\nassociated with this, even though we can create many records(rows) for one2many\ntable.\nWhere are these rows stored?\nAre they stored in any OpenERP memory variable? if so which is that variable\nor function with which we can access those..\nPlease help me out on this.\nThanks in Advance!!!","AnswerCount":3,"Available Count":2,"Score":0.1325487884,"is_accepted":false,"ViewCount":1493,"Q_Id":14119208,"Users Score":2,"Answer":"When saving a new record in openerp, a dictionary will be generated with all the fields having data as keys and its data as values. If the field is a one2many and have many lines, then a list of dictionaries will be the value for the one2many field. You can modify it by overriding the create and write functions in openerp.","Q_Score":2,"Tags":"python,openerp","A_Id":14119351,"CreationDate":"2013-01-02T08:57:00.000","Title":"Where is the value stored for a one2many table initially in OpenERP6.1","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I would like to know as to where is the value stored for a one2many table initially in OpenERP6.1?\ni.e if we create a record for a one2many table,this record will be actually\nsaved to the database table only after saving the record of the main table\nassociated with this, even though we can create many records(rows) for one2many\ntable.\nWhere are these rows stored?\nAre they stored in any OpenERP memory variable? if so which is that variable\nor function with which we can access those..\nPlease help me out on this.\nThanks in Advance!!!","AnswerCount":3,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":1493,"Q_Id":14119208,"Users Score":0,"Answer":"One2Many field is child parent relation in OpenERP. One2Many is just logical field there is no effect in database for that.\nIf you are creating Sale order then Sale order line is One2Many in Sale order model. But if you will not put Many2One in Sale order line then One2Many in Sale order will not work.\nMany2One field put foreign key for the related model in the current table.","Q_Score":2,"Tags":"python,openerp","A_Id":14120545,"CreationDate":"2013-01-02T08:57:00.000","Title":"Where is the value stored for a one2many table initially in OpenERP6.1","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I want to compare the value of a given column at each row against another value, and if the values are equal, I want to copy the whole row to another spreadsheet.\nHow can I do this using Python?\nTHANKS!","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":14135,"Q_Id":14188923,"Users Score":0,"Answer":"For \"xls\" files it's possible to use the xlutils package. It's currently not possible to copy objects between workbooks in openpyxl due to the structure of the Excel format: there are lots of dependencies all over the place that need to be managed. It is, therefore, the responsibility of client code to copy everything required manually. If time permits we might try and port some of the xlutils functionality to openpyxl.","Q_Score":3,"Tags":"python,excel,xlrd,xlwt,openpyxl","A_Id":30048138,"CreationDate":"2013-01-07T02:04:00.000","Title":"How to copy a row of Excel sheet to another sheet using Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I had GAE 1.4 installed in my local UBUNTU system and everything was working fine. Only warning I was getting at that time was something like \"You are using old GAE SDK 1.4.\" So, to get rid of that I have done following things:\n\nI removed old version of GAE and installed GAE 1.7. Along with that I have\nalso changed my djangoappengine folder with latest version.\nI have copied new version of GAE to \/usr\/local directory since my ~\/bashrc file PATH variable pointing to GAE to this directory.\n\nNow, I am getting error\ndjango.core.exceptions.ImproperlyConfigured: 'djangoappengine.db' isn't an available database backend.\n    Try using django.db.backends.XXX, where XXX is one of:\n    'dummy', 'mysql', 'oracle', 'postgresql', 'postgresql_psycopg2', 'sqlite3'\nError was: No module named utils\nI don't think there is any problem of directory structure since earlier it was running fine.\nDoes anyone has any idea ? \nYour help will be highly appreciated.\n-Sunil\n.","AnswerCount":2,"Available Count":2,"Score":0.0996679946,"is_accepted":false,"ViewCount":191,"Q_Id":14307581,"Users Score":1,"Answer":"Did you update djangoappengine without updating django-nonrel and djangotoolbox?\nWhile I haven't upgraded to GAE 1.7.4 yet, I'm running 1.7.2 with no problems.  I suspect your problem is not related to the GAE SDK but rather your django-nonrel installation has mismatching pieces.","Q_Score":0,"Tags":"python,google-app-engine,django-nonrel","A_Id":14368275,"CreationDate":"2013-01-13T20:03:00.000","Title":"Django-nonrel broke after installing new version of Google App Engine SDK","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I had GAE 1.4 installed in my local UBUNTU system and everything was working fine. Only warning I was getting at that time was something like \"You are using old GAE SDK 1.4.\" So, to get rid of that I have done following things:\n\nI removed old version of GAE and installed GAE 1.7. Along with that I have\nalso changed my djangoappengine folder with latest version.\nI have copied new version of GAE to \/usr\/local directory since my ~\/bashrc file PATH variable pointing to GAE to this directory.\n\nNow, I am getting error\ndjango.core.exceptions.ImproperlyConfigured: 'djangoappengine.db' isn't an available database backend.\n    Try using django.db.backends.XXX, where XXX is one of:\n    'dummy', 'mysql', 'oracle', 'postgresql', 'postgresql_psycopg2', 'sqlite3'\nError was: No module named utils\nI don't think there is any problem of directory structure since earlier it was running fine.\nDoes anyone has any idea ? \nYour help will be highly appreciated.\n-Sunil\n.","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":191,"Q_Id":14307581,"Users Score":0,"Answer":"Actually I changed the google app engine path in \/.bashrc file and restarted the system. It solved the issue. I think since I was not restarting the system after .bashrc changes, hence it was creating problem.","Q_Score":0,"Tags":"python,google-app-engine,django-nonrel","A_Id":14382654,"CreationDate":"2013-01-13T20:03:00.000","Title":"Django-nonrel broke after installing new version of Google App Engine SDK","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I'm working on an NDB based Google App Engine application that needs to keep track of the day\/night cycle of a large number (~2000) fixed locations.  Because the latitude and longitude don't ever change, I can precompute them ahead of time using something like PyEphem.  I'm using NDB.  As I see it, the possible strategies are:\n\nTo precompute a year's worth of sunrises into datetime objects, put\nthem into a list, pickle the list and put it into a PickleProperty\n, but put the list into a JsonProperty\nGo with DateTimeProperty and set repeated=True\n\nNow, I'd like the very next sunrise\/sunset property to be indexed, but that can be popped from the list and places into it's own DateTimeProperty, so that I can periodically use a query to determine which locations have changed to a different part of the cycle.  The whole list does not need to be indexed.  \nDoes anyone know the relative effort -in terms of indexing and CPU load for these three approaches?  Does repeated=True have an effect on the indexing?\nThanks,\nDave","AnswerCount":3,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":537,"Q_Id":14343871,"Users Score":0,"Answer":"I would say precompute those structures and output them into hardcoded python structures that you save in a generated python file.\nJust read those structures into memory as part of your instance startup.\nFrom your description, there's no reason to compute these values at runtime, and there's no reason to store it in the datastore since that has a cost associated with it, as well as some latency for the RPC.","Q_Score":1,"Tags":"python,google-app-engine,python-2.7","A_Id":14365980,"CreationDate":"2013-01-15T17:59:00.000","Title":"Best strategy for storing precomputed sunrise\/sunset data?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I'm working on an NDB based Google App Engine application that needs to keep track of the day\/night cycle of a large number (~2000) fixed locations.  Because the latitude and longitude don't ever change, I can precompute them ahead of time using something like PyEphem.  I'm using NDB.  As I see it, the possible strategies are:\n\nTo precompute a year's worth of sunrises into datetime objects, put\nthem into a list, pickle the list and put it into a PickleProperty\n, but put the list into a JsonProperty\nGo with DateTimeProperty and set repeated=True\n\nNow, I'd like the very next sunrise\/sunset property to be indexed, but that can be popped from the list and places into it's own DateTimeProperty, so that I can periodically use a query to determine which locations have changed to a different part of the cycle.  The whole list does not need to be indexed.  \nDoes anyone know the relative effort -in terms of indexing and CPU load for these three approaches?  Does repeated=True have an effect on the indexing?\nThanks,\nDave","AnswerCount":3,"Available Count":2,"Score":0.0665680765,"is_accepted":false,"ViewCount":537,"Q_Id":14343871,"Users Score":1,"Answer":"For 2000 immutable data points - just calculate them when instance starts or on first use, then keep it in memory. This will be the cheapest and fastest.","Q_Score":1,"Tags":"python,google-app-engine,python-2.7","A_Id":14345283,"CreationDate":"2013-01-15T17:59:00.000","Title":"Best strategy for storing precomputed sunrise\/sunset data?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I have income table which contain recurrence field. Now if user select recurrence_type as \"Monthly\" or \"Daily\" then I have to add row into income table \"daily\" or \"monthly\" . Is there any way in Mysql which will add data periodically into table ? I am using Django Framework for developing web application.","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":214,"Q_Id":14344473,"Users Score":0,"Answer":"Used django-celery package and created job in it to update the data periodically","Q_Score":1,"Tags":"python,mysql,django","A_Id":27122957,"CreationDate":"2013-01-15T18:33:00.000","Title":"add data to table periodically in mysql","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have income table which contain recurrence field. Now if user select recurrence_type as \"Monthly\" or \"Daily\" then I have to add row into income table \"daily\" or \"monthly\" . Is there any way in Mysql which will add data periodically into table ? I am using Django Framework for developing web application.","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":214,"Q_Id":14344473,"Users Score":1,"Answer":"As I know there is no such function in MySQL. Even if MySQL could do it, this should not be its job. Such functions should be part of the business logic in your application.\nThe normal way is to setup the cron job in server. The cron job will wake up at the time you set, and then call your python script or SQL to fulfil the adding data work. And scripts are much better than direct SQL.","Q_Score":1,"Tags":"python,mysql,django","A_Id":14344610,"CreationDate":"2013-01-15T18:33:00.000","Title":"add data to table periodically in mysql","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have written a simple blog using Python in google app engine. I want to implement a voting system for each of my posts. My posts are stored in a SQL database and I have a column for no of votes received. Can somebody help me set up voting buttons for individual posts? I am using Jinja2 as the templating engine. \nHow can I make the voting secure? I was thinking of sending a POST\/GET when someone clicks on the vote button which my python script will then read and update the database accordingly. But then I realized that this was insecure. All suggestions are welcome.","AnswerCount":2,"Available Count":2,"Score":0.0996679946,"is_accepted":false,"ViewCount":1105,"Q_Id":14347244,"Users Score":1,"Answer":"If voting is only for subscribed users, then enable voting after members log in to your site. \nIf not, then you can track users' IP addresses so one IP address can vote once for a single article in a day.\nBy the way, what kind of security do you need?","Q_Score":4,"Tags":"python,mysql,google-app-engine,jinja2","A_Id":14347324,"CreationDate":"2013-01-15T21:27:00.000","Title":"How to implement a 'Vote up' System for posts in my blog?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have written a simple blog using Python in google app engine. I want to implement a voting system for each of my posts. My posts are stored in a SQL database and I have a column for no of votes received. Can somebody help me set up voting buttons for individual posts? I am using Jinja2 as the templating engine. \nHow can I make the voting secure? I was thinking of sending a POST\/GET when someone clicks on the vote button which my python script will then read and update the database accordingly. But then I realized that this was insecure. All suggestions are welcome.","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":1105,"Q_Id":14347244,"Users Score":4,"Answer":"First, keep in mind that there is no such thing as \"secure\", just \"secure enough for X\". There's always a tradeoff\u2014more secure means more annoying for your legitimate users and more expensive for you.\nGetting past these generalities, think about your specific case. There is nothing that has a 1-to-1 relationship with users. IP addresses or computers are often shared by multiple people, and at the same time, people often have multiple addresses or computers. Sometimes, something like this is \"good enough\", but from your question, it doesn't sound like it would be.\nHowever, with user accounts, the only false negatives come from people intentionally creating multiple accounts or hacking others' accounts, and there are no false positives. And there's a pretty linear curve in the annoyance\/cost vs. security tradeoff, all the way from \"\"Please don't create sock puppets\" to CAPTCHA to credit card checks to web of trust\/reputation score to asking for real-life info and hiring an investigator to check it out.\nIn real life, there's often a tradeoff between more than just these two things. For example, if you're willing to accept more cheating if it directly means more money for you, you can just charge people real money to vote (as with those 1-900 lines that many TV shows use).\n\n\nHow do Reddit and Digg check multiple voting from a single registered user?\n\nI don't know exactly how Reddit or Digg does things, but the general idea is simple: Keep track of individual votes.\nNormally, you've got your users stored in a SQL RDBMS of some kind. So, you just add a Votes table with columns for user ID, question ID, and answer. (If you're using some kind of NoSQL solution, it should be easy to translate appropriately. For example, maybe there's a document for each question, and the document is a dictionary mapping user IDs to answers.) When a user votes, just INSERT a row into the database.\nWhen putting together the voting interface, whether via server-side template or client-side AJAX, call a function that checks for an existing vote. If there is one, instead of showing the vote controls, show some representation of \"You already voted Yes.\" You also want to check again at vote-recording time, to make sure someone doesn't hack the system by opening 200 copies of the page, all of which allow voting (because the user hasn't voted yet), and then submitting 200 Yes votes, but with a SQL database, this is as simple as making Question, User into a multi-column unique key.\nIf you want to allow vote changing or undoing, just add more controls to the interface, and handle them with UPDATE and DELETE calls. If you want to get really fancy\u2014like this site, which allows undoing if you have enough rep and if either your original vote was in the past 5 minutes or the answer has been edited since your vote (or something like that)\u2014you may have to keep some extra info, like record a row for each voting action, with a timestamp, instead of just a single answer for each user.\nThis design also means that, instead of keeping a count somewhere, you generate the vote tally on the fly by, e.g., SELECT COUNT(*) FROM Votes WHERE Question=? GROUP BY Answer. But, as usual, if this is too slow, you can always optimize-by-denormalizing and keep the totals along with the actual votes. Similarly, if your user base is huge, you may want to archive votes on old questions and get them out of the operational database. And so on.","Q_Score":4,"Tags":"python,mysql,google-app-engine,jinja2","A_Id":14349144,"CreationDate":"2013-01-15T21:27:00.000","Title":"How to implement a 'Vote up' System for posts in my blog?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"My Question is a bit complex and iam new to OpenERP.\nI have an external database and an OpenERP. the external one isn't PostgreSQL. \nMY job is that I need to synchronize the partners in the two databases. \nExternal one being the more important. This means that if the external one's data change so does the OpenERp's, but if OpenERP's data changes nothing changes onthe external one.\n\nI can access to the external database, and using XML RCP I have acces\nto OpenERP's as well. \nI can import data from the external database simply with XML RCP but \nthe problem is the sync.\nI can't just INSERT the modified partner and delete the old one\nbecause i have no way to identify the old one.\nI need to UPDATE it. But then i need an id that says which is which. \nand external ID.\nTo my knowledge OpenERP can handle external IDs.\n\nHow does this work? and how can i add an external ID to my res.partner using this?\nI was told that I cant create a new module for this alone I need to use the internal ID works.","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":4853,"Q_Id":14356218,"Users Score":0,"Answer":"Add an integer field in res partner table for storing external id on both database. When data is retrived from the external server and adding to your openerp database, store the external id in the record of res partner in local server and also save the id of the newly created partner record in the external server's partner record. So next time when the external partner record is updated, we can search the external id in our local server and update that record. \nPlease check the openerp module base_synchronization and read the codes, which will be helpful for you.","Q_Score":6,"Tags":"python,xml-rpc,openerp","A_Id":14356856,"CreationDate":"2013-01-16T10:27:00.000","Title":"Adding external Ids to Partners in OpenERP withouth a new module","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm working on a web-app that's very heavily database driven. I'm nearing the initial release and so I've locked down the features for this version, but there are going to be lots of other features implemented after release. These features will inevitably require some modification to the database models, so I'm concerned about the complexity of migrating the database on each release. What I'd like to know is how much should I concern myself with locking down a solid database design now so that I can release quickly, against trying to anticipate certain features now so that I can build it into the database before release? I'm also anticipating finding flaws with my current model and would probably then want to make changes to it, but if I release the app and then data starts coming in, migrating the data would be a difficult task I imagine. Are there conventional methods to tackle this type of problem? A point in the right direction would be very useful.\nFor a bit of background I'm developing an asset management system for a CG production pipeline. So lots of pieces of data with lots of connections between them. It's web-based, written entirely in Python and it uses SQLAlchemy with a SQLite engine.","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":120,"Q_Id":14364214,"Users Score":2,"Answer":"Some thoughts for managing databases for a production application:\n\nMake backups nightly. This is crucial because if you try to do an update (to the data or the schema), and you mess up, you'll need to be able to revert to something more stable.\nCreate environments. You should have something like a local copy of the database for development, a staging database for other people to see and test before going live and of course a production database that your live system points to.\nMake sure all three environments are in sync before you start development locally.  This way you can track changes over time.\nStart writing scripts and version them for releases.  Make sure you store these in a source control system (SVN, Git, etc.)  You just want a historical record of what has changed and also a small set of scripts that need to be run with a given release.  Just helps you stay organized.\nDo your changes to your local database and test it.  Make sure you have scripts that do two things, 1) Scripts that modify the data, or the schema, 2) Scripts that undo what you've done in case things go wrong.  Test these over and over locally.  Run the scripts, test and then rollback.  Are things still ok?\nRun the scripts on staging and see if everything is still ok.  Just another chance to prove your work is good and that if needed you can undo your changes.\nOnce staging is good and you feel confident, run your scripts on the production database.  Remember you have scripts to change data (update, delete statements) and scripts to change schema (add fields, rename fields, add tables).\n\nIn general take your time and be very deliberate in your actions.  The more disciplined you are the more confident you'll be.  Updating the database can be scary, so don't rush things, write out your plan of action, and test, test, test!","Q_Score":1,"Tags":"python,database,migration,sqlalchemy","A_Id":14364804,"CreationDate":"2013-01-16T17:29:00.000","Title":"How to approach updating an database-driven application after release?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have been trying to get my head around Django over the last week or two. Its slowly starting to make some sense and I am really liking it. \nMy goal is to replace a fairly messy excel spreadsheet with a database and frontend for my users. This would involve pulling the data out of a table, presenting it in a web tabular format, and allowing changes to be made through text fields and drop down menus, with a simple update button that will update all changes to the DB.\nMy question is, will the built in Django Forms functionality be the best solution? Or would I create some sort of for loop for my objects and wrap them around html form syntax in my template? I'm just not too sure how to approach the solution.\nApologies if this seems like an simple question, I just feel like there is maybe a few ways to do it but maybe there is one perfect way.\nThanks","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":2045,"Q_Id":14370576,"Users Score":1,"Answer":"Exporting the excel sheet in Django and have the them rendered as text fields , is not as easy as 2 step process.\nyou need to know how Django works.\nFirst you need to export the data in mysql in database using either some language or some ready made tools.\nThen you need to make a Model for that table and then you can use Django admin to edit them","Q_Score":3,"Tags":"python,database,django,frontend","A_Id":14371043,"CreationDate":"2013-01-17T01:00:00.000","Title":"Custom Django Database Frontend","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm wrinting a webapp in bottle.\nI have a small interface that lets user run sql statements.\nSometimes it takes about 5 seconds until the user get's a result because the DB is quite big and old.  \nWhat I want to do is the following:\n1.Starte the query in a thread\n2.Give the user a response right away and have ajax poll for the result  \nThere is one thing that I'm not sure of....Where do I store the result of the query?\nShould I store it in a DB ?\nShould I store it in a variable inside my webapp ?\nWhat do you guys think would be best ?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":105,"Q_Id":14377250,"Users Score":0,"Answer":"This would be a good use for something like memcached.","Q_Score":1,"Tags":"python,database,multithreading","A_Id":14377893,"CreationDate":"2013-01-17T10:43:00.000","Title":"Python 3 - SQL Result - where to store it","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"When I try installing mysql-python using below command,\nmacbook-user$ sudo pip install MYSQL-python\nI get these messages:\n\n\/System\/Library\/Frameworks\/Python.framework\/Versions\/2.7\/include\/python2.7\/pyconfig.h:891:1: warning: this is the location of the previous definition\n\/usr\/bin\/lipo: \/tmp\/_mysql-LtlmLe.o and \/tmp\/_mysql-thwkfu.o have the same architectures (i386) and can't be in the same fat output file\nclang: error: lipo command failed with exit code 1 (use -v to see invocation)\nerror: command 'clang' failed with exit status 1\n\nDoes anyone know how to solve this problem? Help me please!","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":506,"Q_Id":14399223,"Users Score":0,"Answer":"At first glance it looks like damaged pip package. Have you tried easy_install instead with the same package?","Q_Score":1,"Tags":"python,mysql,django,pip,mysql-python","A_Id":14399388,"CreationDate":"2013-01-18T12:41:00.000","Title":"clang error when installing MYSQL-python on Lion-mountain (Mac OS X 10.8)","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":0},{"Question":"When I fired redis-py's bgsave() command, the return value was False, but I'm pretty sure the execution was successful because I've checked with lastsave().\nHowever, if I use save() the return value would be True after successful execution.\nCould anyone please explain what False indicates for bgsave()? Not sure if it has anything to do with bgsave() being executed in the background.","AnswerCount":1,"Available Count":1,"Score":0.3799489623,"is_accepted":false,"ViewCount":778,"Q_Id":14417846,"Users Score":2,"Answer":"Thanks to Pavel Anossov, after reading the code of client.py, I found out that responses from 2 commands (BGSAVE and BGREWRITEAOF) were not converted from bytes to str, and this caused the problem in Python 3.\nTo fix this issue, just change lambda r: r == to lambda r: nativestr(r) == for these two commands in RESPONSE_CALLBACKS.","Q_Score":1,"Tags":"python,redis","A_Id":14418853,"CreationDate":"2013-01-19T19:10:00.000","Title":"Why does redis-py's bgsave() command return False after successful execution?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am writing a chat bot that uses past conversations to generate its responses. Currently I use text files to store all the data but I want to use a database instead so that multiple instances of the bot can use it at the same time.\nHow should I structure this database?\nMy first idea was to keep a main table like create table Sessions (startTime INT,ip INT, botVersion REAL, length INT, tableName TEXT). Then for each conversation I create table <generated name>(timestamp INT, message TEXT) with all the messages that were sent or received during that conversation. When the conversation is over, I insert the name of the new table into Sessions(tableName). Is it ok to programmatically create tables in this manner? I am asking because most SQL tutorials seem to suggest that tables are created when the program is initialized.\nAnother way to do this is to have a huge create table Messages(id INT, message TEXT) table that stores every message that was sent or received. When a conversation is over, I can add a new entry to Sessions that includes the id used during that conversation so that I can look up all the messages sent during a certain conversation. I guess one advantage of this is that I don't need to have hundreds or thousands of tables. \nI am planning on using SQLite despite its low concurrency since each instance of the bot may make thousands of reads before generating a response (which will result in one write). Still, if another relational database is better suited for this task, please comment.\nNote: There are other questions on SO about storing chat logs in databases but I am specifically looking for how it should be structured and feedback on the above ideas.","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":1198,"Q_Id":14430856,"Users Score":1,"Answer":"Don't use a different table for each conversation. Instead add a \"conversation\" column to your single table.","Q_Score":1,"Tags":"python,sql,database,sqlite,database-design","A_Id":14430911,"CreationDate":"2013-01-21T00:13:00.000","Title":"Storing chat logs in relational database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"This is my program\n\nimport MySQLdb as mdb\nfrom MySQLdb import IntegrityError\nconn = mdb.connect(\"localhost\", \"asdf\", \"asdf\", \"asdf\")\n\nwhen the connect function is called python prints some text (\"h\" in the shell).\nThis happens only if I execute the script file from a particular folder.\nIf I copy the same script file to some other folder \"h\" is not printed.\nactually i had this line previously in the same script for testing\n\nprint \"h\"\n\nbut now i have removed the line from the script. But still it is printed. What happen to my folder?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":41,"Q_Id":14434712,"Users Score":1,"Answer":"Try deleting *.pyc files. Secondly use script with -v option so that you can view from where the file is being imported","Q_Score":0,"Tags":"python,mysql","A_Id":14434772,"CreationDate":"2013-01-21T08:18:00.000","Title":"python mysqldb printing text even if no print statement in the code","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have populated a combobox with an QSqlQueryModel. It's all working fine as it is, but I would like to add an extra item to the combobox that could say \"ALL_RECORDS\". This way I could use the combobox as a filtering device. \nI obviously don't want to add this extra item in the database, how can I add it to the combobox after it's been populated by a model?","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":243,"Q_Id":14455871,"Users Score":1,"Answer":"You could use a proxy model that takes gets it's data from two models, one for your default values, the other for your database, and use it to populate your QComboBox.","Q_Score":1,"Tags":"python,qt,pyqt,pyqt4,pyside","A_Id":14540595,"CreationDate":"2013-01-22T10:02:00.000","Title":"Adding an item to an already populated combobox","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":1,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm building a finance application in Python to do time series analysis on security prices (among other things). The heavy lifting will be done in Python mainly using Numpy, SciPy, and pandas (pandas has an interface for SQLite and MySQL). With a web interface to present results. There will be a few hundred GB of data.\nI'm curious what is the better option for database in terms of performance, ease of accessing the data (queries), and interface with Python. I've seen the posts about the general pros and cons of SQLite v. MySQL but I'm looking for feedback that's more specific to a Python application.","AnswerCount":3,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":1382,"Q_Id":14509517,"Users Score":0,"Answer":"SQLite is great for embedded databases, but it's not really great for anything that requires access by more than one process at a time. For this reason it cannot be taken seriously for your application.\nMySQL is a much better alternative. I'm also in agreement that Postgres would be an even better option.","Q_Score":0,"Tags":"python,mysql,sqlite,pandas","A_Id":14509945,"CreationDate":"2013-01-24T19:49:00.000","Title":"MySQL v. SQLite for Python based financial web app","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm building a finance application in Python to do time series analysis on security prices (among other things). The heavy lifting will be done in Python mainly using Numpy, SciPy, and pandas (pandas has an interface for SQLite and MySQL). With a web interface to present results. There will be a few hundred GB of data.\nI'm curious what is the better option for database in terms of performance, ease of accessing the data (queries), and interface with Python. I've seen the posts about the general pros and cons of SQLite v. MySQL but I'm looking for feedback that's more specific to a Python application.","AnswerCount":3,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":1382,"Q_Id":14509517,"Users Score":0,"Answer":"For many 'research' oriented time series database loads, it is far faster to do as much analysis in the database than to copy the data to a client and analyze it using a regular programming language.  Copying 10G across the network is far slower than reading it from disk.\nRelational databases do not natively support time series operations, so generating something as simple as security returns from security prices is either impossible or very difficult in both MySQL and SQLite.\nPostgres has windowing operations, as do several other relational-like databases; the trade-off is that that they don't do as many transactions per second.  Many others use K or Q.\nThe financial services web apps that I've seen used multiple databases; the raw data was stored in 'research' databases that were multiply indexed and designed for flexibility, while the web-apps interacted directly with in-memory caches and higher-speed RDBs; the tradeoff was that data had to be copied from the 'research' databases to the 'production' databases.","Q_Score":0,"Tags":"python,mysql,sqlite,pandas","A_Id":14514661,"CreationDate":"2013-01-24T19:49:00.000","Title":"MySQL v. SQLite for Python based financial web app","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am using Celery standalone (not within Django).  I am planning to have one worker task type running on multiple physical machines.  The task does the following\n\nAccept an XML document.\nTransform it.\nMake multiple database reads and writes.\n\nI'm using PostgreSQL, but this would apply equally to other store types that use connections.  In the past, I've used a database connection pool to avoid creating a new database connection on every request or avoid keeping the connection open too long.  However, since each Celery worker runs in a separate process, I'm not sure how they would actually be able to share the pool.  Am I missing something?  I know that Celery allows you to persist a result returned from a Celery worker, but that is not what I'm trying to do here.  Each task can do several different updates or inserts depending on the data processed.\nWhat is the right way to access a database from within a Celery worker?\nIs it possible to share a pool across multiple workers\/tasks or is there some other way to do this?","AnswerCount":6,"Available Count":2,"Score":0.0665680765,"is_accepted":false,"ViewCount":24474,"Q_Id":14526249,"Users Score":2,"Answer":"You can override the default behavior to have threaded workers instead of a worker per process in your celery config:\nCELERYD_POOL = \"celery.concurrency.threads.TaskPool\"\nThen you can store the shared pool instance on your task instance and reference it from each threaded task invocation.","Q_Score":47,"Tags":"python,postgresql,connection-pooling,celery","A_Id":14526700,"CreationDate":"2013-01-25T16:38:00.000","Title":"Celery Worker Database Connection Pooling","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":0},{"Question":"I am using Celery standalone (not within Django).  I am planning to have one worker task type running on multiple physical machines.  The task does the following\n\nAccept an XML document.\nTransform it.\nMake multiple database reads and writes.\n\nI'm using PostgreSQL, but this would apply equally to other store types that use connections.  In the past, I've used a database connection pool to avoid creating a new database connection on every request or avoid keeping the connection open too long.  However, since each Celery worker runs in a separate process, I'm not sure how they would actually be able to share the pool.  Am I missing something?  I know that Celery allows you to persist a result returned from a Celery worker, but that is not what I'm trying to do here.  Each task can do several different updates or inserts depending on the data processed.\nWhat is the right way to access a database from within a Celery worker?\nIs it possible to share a pool across multiple workers\/tasks or is there some other way to do this?","AnswerCount":6,"Available Count":2,"Score":0.0996679946,"is_accepted":false,"ViewCount":24474,"Q_Id":14526249,"Users Score":3,"Answer":"Have one DB connection per worker process. Since celery itself maintains a pool of worker processes, your db connections will always be equal to the number of celery workers. \nFlip side, sort of, it will tie up db connection pooling to celery worker process management. But that should be fine given that GIL allows only one thread at a time in a process.","Q_Score":47,"Tags":"python,postgresql,connection-pooling,celery","A_Id":14549811,"CreationDate":"2013-01-25T16:38:00.000","Title":"Celery Worker Database Connection Pooling","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":0},{"Question":"There is a sqlite3 library that comes with python 2.7.3, but it is hardly the latest version.\nI would like to upgrade it within a virtualenv environment. In other words, the upgrade only applies to the version of python installed within this virtualenv.\nWhat is the correct way to do so?","AnswerCount":3,"Available Count":2,"Score":0.0665680765,"is_accepted":false,"ViewCount":9594,"Q_Id":14541869,"Users Score":1,"Answer":"I was stuck in the same problem once. This solved it for me:\n\nDownload and untar the python version required\nmkdir local\nuntar sqlite after downloading its package\n.\/configure --prefix=\/home\/aanuj\/local\nmake\nmake install\n.\/configure --prefix=\/home\/anauj\/local LDFLAGS='-L\/home\/aaanuj\/local\/lib' CPPFLAGS='-I\/home\/aanuj\/local\/include'\nmake\nFind the sqlite3.so and copy to home\/desired loc\nExtract beaver \nSetup the virtual env with the python version needed\nActivate the env\nunalias python \nexport PYTHONPATH=\/home\/aanuj(location of _sqlite3.so)\nEnjoy","Q_Score":4,"Tags":"python,sqlite,virtualenv","A_Id":17417792,"CreationDate":"2013-01-26T21:42:00.000","Title":"How to upgrade sqlite3 in python 2.7.3 inside a virtualenv?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"There is a sqlite3 library that comes with python 2.7.3, but it is hardly the latest version.\nI would like to upgrade it within a virtualenv environment. In other words, the upgrade only applies to the version of python installed within this virtualenv.\nWhat is the correct way to do so?","AnswerCount":3,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":9594,"Q_Id":14541869,"Users Score":4,"Answer":"The below works for me, but please comment if there is any room for improvement:\n\nActivate the virtualenv to which you are going to install the latest sqlite3\nGet the latest source of pysqlite package from google code: wget http:\/\/pysqlite.googlecode.com\/files\/pysqlite-2.6.3.tar.gz\nCompile pysqlite from source and together with the latest sqlite database: python setup.py build_static\nInstall it to the site-packages directory of the virtualenv: python setup.py install\nThe above will actually install the pysqlite into path-to-virtualenv\/lib\/python2.7\/site-packages, which is where all other pip-installed libraries are.\n\nNow, I have the latest version of sqlite (compiled into pysqlite) installed within a virtualenv, so I can do: from pysqlite2 import dbapi2 as sqlite","Q_Score":4,"Tags":"python,sqlite,virtualenv","A_Id":14550136,"CreationDate":"2013-01-26T21:42:00.000","Title":"How to upgrade sqlite3 in python 2.7.3 inside a virtualenv?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have couple OpenERP modules implemented for OpenERP 6.1 version. When I installed OpenERP 7.0, i copied these modules into addons folder for OpenERP 7. After that, I tried to update modules list trough web interface, but nothings changed. Also, I started server again with options --database=mydb --update=all, but modules list didn't change. Did I miss something? Is it possible in OpenERP version 7, usage of modules from version 6.1? \nThanks for advice. \nUPDATE:\nI already exported my database from version 6.1 in *.sql file. Will it OpenERP 7 work, if I just import these data in new database, which I created with OpenERP 7?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":3217,"Q_Id":14563801,"Users Score":6,"Answer":"Openerp 6.1 modules directly can not be used in openerp  7. You have to do some basic changes \nin openerp 6.1 modules. Like tree, form tag compulsory string and verision=\"7\" include in form. If you have inherited some basic modules like  sale, purchase then you have to do changes in inherit xpath etc. Some objects res.parter.address removed then you have take care of this and replace with res.partner. \nThanks","Q_Score":2,"Tags":"python,openerp,erp","A_Id":14564692,"CreationDate":"2013-01-28T14:06:00.000","Title":"OpenERP 7 with modules from OpenERP 6.1","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am trying to analyse the SQL performance of our Django (1.3) web application. I have added a custom log handler which attaches to django.db.backends and set DEBUG = True, this allows me to see all the database queries that are being executed.\nHowever the SQL is not valid SQL! The actual query is select * from app_model where name = %s with some parameters passed in (e.g. \"admin\"), however the logging message doesn't quote the params, so the sql is select * from app_model where name = admin, which is wrong. This also happens using django.db.connection.queries. AFAIK the django debug toolbar has a complex custom cursor to handle this.\nUpdate For those suggesting the Django debug toolbar: I am aware of that tool, it is great. However it does not do what I need. I want to run a sample interaction of our application, and aggregate the SQL that's used. DjDT is great for showing and shallow learning. But not great for aggregating and summarazing the interaction of dozens of pages.\nIs there any easy way to get the real, legit, SQL that is run?","AnswerCount":4,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":189,"Q_Id":14567172,"Users Score":0,"Answer":"select * from app_model where name = %s is a prepared statement. I would recommend you to log the statement and the parameters separately. In order to get a wellformed query you need to do something like \"select * from app_model where name = %s\" % quote_string(\"user\") or more general query % map(quote_string, params). \nPlease note that quote_string is DB specific and the DB 2.0 API does not define a quote_string method. So you need to write one yourself. For logging purposes I'd recommend keeping the queries and parameters separate as it allows for far better profiling as you can easily group the queries without taking the actual values into account.","Q_Score":0,"Tags":"python,sql,django,django-database","A_Id":14567526,"CreationDate":"2013-01-28T17:00:00.000","Title":"How to retrieve the real SQL from the Django logger?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am trying to use a python set as a filter for ids from a mysql table.\nThe python set stores all the ids to filter (about 30 000 right now) this number will grow slowly over time and I am concerned about the maximum capacity of a python set. Is there a limit to the number of elements it can contain?","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":2460,"Q_Id":14577790,"Users Score":0,"Answer":"I don't know if there is an arbitrary limit for the number of items in a set. More than likely the limit is tied to the available memory.","Q_Score":2,"Tags":"python,set","A_Id":14577827,"CreationDate":"2013-01-29T07:31:00.000","Title":"Is there a limit to the number of values that a python set can contain?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"No code examples here. Just running into an issue with Microsoft Excel 2010 where I have a python script on linux that pulls data from csv files, pushes it into excel, and emails that file to a certain email address as an attachment.\nMy problem is that I'm using formulas in my excel file, and when it first opens up it goes into \"Protected View\". My formulas don't load until after I click \"Enable Editing\". Is there anyway to get my numbers to show up even if Protected Mode is on?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":853,"Q_Id":14592328,"Users Score":0,"Answer":"Figured this out. Just used the for loop to keep a running total. Sorry for the wasted question.","Q_Score":0,"Tags":"python,linux,excel,view,protected","A_Id":14592481,"CreationDate":"2013-01-29T21:08:00.000","Title":"Protected View in Microsoft Excel 2010 and Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"For 100k+ entities in google datastore, ndb.query().count() is going to cancelled by deadline , even with index. I've tried with produce_cursors options but only iter() or fetch_page() will returns cursor but count() doesn't. \nHow can I count large entities?","AnswerCount":3,"Available Count":1,"Score":0.1325487884,"is_accepted":false,"ViewCount":2669,"Q_Id":14673642,"Users Score":2,"Answer":"This is indeed a frustrating issue. I've been doing some work in this area lately to get some general count stats - basically, the number of entities that satisfy some query. count() is a great idea, but it is hobbled by the datastore RPC timeout.\nIt would be nice if count() supported cursors somehow so that you could cursor across the result set and simply add up the resulting integers rather than returning a large list of keys only to throw them away. With cursors, you could continue across all 1-minute \/ 10-minute boundaries, using the \"pass the baton\" deferred approach. With count() (as opposed to fetch(keys_only=True)) you can greatly reduce the waste and hopefully increase the speed of the RPC calls, e.g., it takes a shocking amount of time to count to 1,000,000 using the fetch(keys_only=True) approach - an expensive proposition on backends.\nSharded counters are a lot of overhead if you only need\/want periodic count statistics (e.g., a daily count of all my accounts in the system by, e.g., country).","Q_Score":4,"Tags":"python,google-app-engine,app-engine-ndb,bigtable","A_Id":14713169,"CreationDate":"2013-02-03T14:41:00.000","Title":"ndb.query.count() failed with 60s query deadline on large entities","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I need some help with d3 and MySQL. Below is my question:  \nI have data stored in MySQL (eg: keywords with their frequencies). I now want to visualize it using d3. As far as my knowledge of d3 goes, it requires json file as input. My question is: How do I access this MySQL database from d3 script? One way which i could think of is: \n\nUsing Python, connect with database and convert the data in json format. Save this in some .json file. \nIn d3, read this json file as input and use it in visualization.\n\nIs there any other way to convert the data in MySQL into .json format directly using d3? Can we connect to MySQL from d3 and read the data?\nThanks a lot!","AnswerCount":3,"Available Count":1,"Score":0.0665680765,"is_accepted":false,"ViewCount":8185,"Q_Id":14679610,"Users Score":1,"Answer":"d3 is a javascript library that run on client-side, while MySQL database is supposed to run on server-side.\nd3 can't connect to MySQL database, let alone conversion to json format. The way you thought it was possible (steps 1 and 2) is what you should do.","Q_Score":4,"Tags":"javascript,python,mysql,d3.js,data-visualization","A_Id":14679748,"CreationDate":"2013-02-04T02:22:00.000","Title":"Accessing MySQL database in d3 visualization","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I would like to hear your opinion about the effective implementation of one-to-many relationship with Python NDB. (e.g. Person(one)-to-Tasks(many))\nIn my understanding, there are three ways to implement it.\n\nUse 'parent' argument\nUse 'repeated' Structured property\nUse 'repeated' Key property\n\nI choose a way based on the logic below usually, but does it make sense to you? \nIf you have better logic, please teach me.\n\nUse 'parent' argument\n\nTransactional operation is required between these entities\nBidirectional reference is required between these entities\nStrongly intend 'Parent-Child' relationship\n\nUse 'repeated' Structured property\n\nDon't need to use 'many' entity individually (Always, used with 'one' entity)\n'many' entity is only referred by 'one' entity\nNumber of 'repeated' is less than 100\n\nUse 'repeated' Key property\n\nNeed to use 'many' entity individually\n'many' entity can be referred by other entities\nNumber of 'repeated' is more than 100\n\n\nNo.2 increases the size of entity, but we can save the datastore operations. (We need to use projection query to reduce CPU time for the deserialization though). Therefore, I use this way as much as I can.\nI really appreciate your opinion.","AnswerCount":2,"Available Count":2,"Score":1.0,"is_accepted":false,"ViewCount":1389,"Q_Id":14739044,"Users Score":6,"Answer":"One thing that most GAE users will come to realize (sooner or later) is that the datastore does not encourage design according to the formal normalization principles that would be considered a good idea in relational databases. Instead it often seems to encourage design that is unintuitive and anathema to established norms. Although relational database design principles have their place, they just don't work here.  \nI think the basis for the datastore design instead falls into two questions:\n\nHow am I going to read this data and how do I read it with the minimum number of read operations?\nIs storing it that way going to lead to an explosion in the number of write and indexing operations?\n\nIf you answer these two questions with as much foresight and actual tests as you can, I think you're doing pretty well. You could formalize other rules and specific cases, but these questions will work most of the time.","Q_Score":11,"Tags":"python,google-app-engine,app-engine-ndb","A_Id":14749034,"CreationDate":"2013-02-06T21:22:00.000","Title":"Effective implementation of one-to-many relationship with Python NDB","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":0},{"Question":"I would like to hear your opinion about the effective implementation of one-to-many relationship with Python NDB. (e.g. Person(one)-to-Tasks(many))\nIn my understanding, there are three ways to implement it.\n\nUse 'parent' argument\nUse 'repeated' Structured property\nUse 'repeated' Key property\n\nI choose a way based on the logic below usually, but does it make sense to you? \nIf you have better logic, please teach me.\n\nUse 'parent' argument\n\nTransactional operation is required between these entities\nBidirectional reference is required between these entities\nStrongly intend 'Parent-Child' relationship\n\nUse 'repeated' Structured property\n\nDon't need to use 'many' entity individually (Always, used with 'one' entity)\n'many' entity is only referred by 'one' entity\nNumber of 'repeated' is less than 100\n\nUse 'repeated' Key property\n\nNeed to use 'many' entity individually\n'many' entity can be referred by other entities\nNumber of 'repeated' is more than 100\n\n\nNo.2 increases the size of entity, but we can save the datastore operations. (We need to use projection query to reduce CPU time for the deserialization though). Therefore, I use this way as much as I can.\nI really appreciate your opinion.","AnswerCount":2,"Available Count":2,"Score":1.0,"is_accepted":false,"ViewCount":1389,"Q_Id":14739044,"Users Score":7,"Answer":"A key thing you are missing: How are you reading the data?\nIf you are displaying all the tasks for a given person on a request, 2 makes sense: you can query the person and show all his tasks.\nHowever, if you need to query say a list of all tasks say due at a certain time, querying for repeated structured properties is terrible.  You will want individual entities for your Tasks.\nThere's a fourth option, which is to use a KeyProperty in your Task that points to your Person.  When you need a list of Tasks for a person you can issue a query.\nIf you need to search for individual Tasks, then you probably want to go with #4.  You can use it in combination with #3 as well.\nAlso, the number of repeated properties has nothing to do with 100.  It has everything to do with the size of your Person and Task entities, and how much will fit into 1MB.  This is potentially dangerous, because if your Task entity can potentially be large, you might run out of space in your Person entity faster than you expect.","Q_Score":11,"Tags":"python,google-app-engine,app-engine-ndb","A_Id":14740062,"CreationDate":"2013-02-06T21:22:00.000","Title":"Effective implementation of one-to-many relationship with Python NDB","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":0},{"Question":"Pretty simple question but haven't been able to find a good answer.\nIn Excel, I am generating files that need to be automatically read. They are read by an ID number, but the format I get is setting it as text. When using xlrd, I get this format:\n\n5.5112E+12\n\nWhen I need it in this format:\n\n5511195414392\n\nWhat is the best way to achieve this? I would like to avoid using xlwt but if it is necessary I could use help on getting started in that process too","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":1158,"Q_Id":14751806,"Users Score":1,"Answer":"I used the CSV module to figure this out, as it read the cells correctly.","Q_Score":2,"Tags":"python,xlrd","A_Id":14854783,"CreationDate":"2013-02-07T13:05:00.000","Title":"Reading scientific numbers in xlrd","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have really big database which I want write to xlsx\/xls file. I already tried to use xlwt, but it allows to write only 65536 rows (some of my tables have more than 72k rows). I also found openpyxl, but it works too slow, and use huge amount of memory for big spreadsheets. Are there any other possibilities to write excel files?\nedit:\nFollowing kennym's advice i used Optimised Reader and Writer. It is less memory consuming now, but still time consuming. Exporting takes more than hour now (for really big tables- up to 10^6 rows). Are there any other possibilities?  Maybe it is possible to export whole table from HDF5 database file to excel, instead of doing it row after row- like it is now in my code?","AnswerCount":3,"Available Count":1,"Score":0.0665680765,"is_accepted":false,"ViewCount":5375,"Q_Id":14754090,"Users Score":1,"Answer":"XlsxWriter work for me. I try openpyxl but it error. 22k*400 r*c","Q_Score":8,"Tags":"python,excel,hdf5","A_Id":31982266,"CreationDate":"2013-02-07T14:56:00.000","Title":"How to write big set of data to xls file?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"How would one go about connecting to a different database based on which module is being used? Our scenario is as follows:\nWe have a standalone application with its own database on a certain server and OpenERP running on different server. We want to create a module in OpenERP which can utilise entities on the standalone application server rather than creating its own entities in its own database, is this possible? How can we change the connection parameters that the ORM uses to connect to its own database to point to a different database?\nOfcourse, one way is to use the base_synchro module to synchronise the required entities between both database but considering the large amount of data, we don't want duplication. Another way is to use xmlrpc to get data into OpenERP but that still requires entities to be present in OpenERP database.\nHow can we solve this problem without data duplication? How can a module in OpenERP be created based on a different database?","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":1877,"Q_Id":14756365,"Users Score":1,"Answer":"One way to connect to an external application is to create a connector module. There are already several connector modules that you can take a look at:\n\nthe thunderbird and outlook plugins\nthe joomla and magento modules\nthe 'event moodle' module\n\nFor example, the joomla connector uses a joomla plugin to handle the communication between OpenERP and joomla. The communication protocol used is XML-RPC but you can choose any protocol you want. You can even choose to connect directly to the external database using the psycopg2 modules (if the external database is using Postgresql) but this is not recommended. But perhaps you don't have the choice if this external application has no connection API.\nYou need to know what are the available ways to connect to this external application and choose one of these. Once you have chosen the right protocol, you can create your OpenERP module.\nYou can map entities stored on the external application using osv.TransientModel objects (formerly known as osv memory). The tables related to these objects will still be created in the OpenERP database but the data is volatile (deleted after some time).","Q_Score":1,"Tags":"python,xml-rpc,openerp","A_Id":14796657,"CreationDate":"2013-02-07T16:45:00.000","Title":"How to connect to a different database in OpenERP?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have pip installed psycopg2, but when I try to runserver or syncdb in my Django project, it raises an error saying there is \"no module named _psycopg\".\nEDIT: the \"syncdb\" command now raises:\ndjango.core.exceptions.ImproperlyConfigured: ImportError django.contrib.admin: No module named _psycopg\nThanks for your help","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1586,"Q_Id":14758024,"Users Score":1,"Answer":"This was solved by performing a clean reinstall of django. There was apparently some dependecies missing that the recursive pip install did not seem to be able to solve.","Q_Score":2,"Tags":"python,django,pip,psycopg2,psycopg","A_Id":15337328,"CreationDate":"2013-02-07T18:10:00.000","Title":"Psycopg missing module in Django","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"TLDR; Are there drawbacks to putting two different types of documents into the same collection to save a round-trip to the database?\nSo I have documents with children, and a list of keys in the parent referencing the children, and almost whenever we want a parent, we also want the children to come along. The naive way to do this is to fetch the parent, and then get the children using the list of child keys with $IN (in SQL, we would use a join). However, this means making 2 round trips for a fairly frequent operation. We have a few options to improve this, especially since we can retrieve the child keys at the same time as the parent keys:\n\nPut the children in the parent document\nWhile this would play to mongo's strength, we also want to keep this data normalized\nPipeline database requests in threads\nWhich may or may not improve performance once we factor in the connection pool. It also means dealing with threading in a python app, which isn't terrible, but isn't great.\nKeep the parent\/child documents in the same collection (not embedded)\nThis way we can do one query for all the keys at once; this does mean some conceptual overhead in the wrapper for accessing the database, and forcing all indexes to be sparse, but otherwise seems straightforward.\n\nWe could profile all these options, but it does feel like someone out there should already have experience with this despite not finding anything online. So, is there something I am missing in my analysis?","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":339,"Q_Id":14780381,"Users Score":1,"Answer":"I'll address the three points separately. You should know that it absolutely depends on the situation on what works best. There is no \"theoretically correct\" answer as it depends on your data store\/access patterns.\n\nIt is always a fairly complex decision on how you store your data. I think the main rule should be \"How do I query my data?\", and not \"We want to have all data normalised\". Data normalisation is something you do for a relational database, not for MongoDB. If you almost always query the children with the parent, and you don't have an unbound list of children, then that is how you should store them. Just be aware that a document in MongoDB is limited to 16MB (which is a lot more than you think). \nAvoid threading. You will just be better off running two queries in sequence, from two different collections. Less complex is a good thing!\nThis works, but it is a fairly ugly way. But then again, ugly isn't always a bad thing if it makes things go a lot faster. I don't quite know how distinct your parent and child documents are of course, so it's a difficult to say whether this is a good solution. A sparse index, which I assume you will do on a specific field depending on whether it is a parent or child, is a good idea. But perhaps you can get away with one index as well. I'd be happy to update your answer after you've shown your suggested schemas.\n\nI would recommend you do some benchmarking, but forget about option 2.","Q_Score":0,"Tags":"python,performance,mongodb","A_Id":14780990,"CreationDate":"2013-02-08T19:58:00.000","Title":"Put different \"schemas\" into same MongoDB collection","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"My python project involves an externally provided database: A text file of approximately 100K lines.\nThis file will be updated daily.\nShould I load it into an SQL database, and deal with the diff daily? Or is there an effective way to \"query\" this text file?\nADDITIONAL INFO:\n\nEach \"entry\", or line, contains three fields - any one of which can be used as an index.\nThe update is is the form of the entire database - I would have to manually generate a diff\nThe queries are just looking up records and displaying the text.\nQuerying the database will be a fundamental task of the application.","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":336,"Q_Id":14795810,"Users Score":0,"Answer":"What I've done before is create SQLite databases from txt files which were created from database extracts, one SQLite db for each day.\nOne can query across SQLite db to check the values etc and create additional tables of data.\nI added an additional column of data that was the SHA1 of the text line so that I could easily identify lines that were different. \nIt worked in my situation and hopefully may form the barest sniff of an acorn of an idea for you.","Q_Score":2,"Tags":"python,sql,database,text","A_Id":14797390,"CreationDate":"2013-02-10T07:53:00.000","Title":"Large text database: Convert to SQL or use as is","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"My python project involves an externally provided database: A text file of approximately 100K lines.\nThis file will be updated daily.\nShould I load it into an SQL database, and deal with the diff daily? Or is there an effective way to \"query\" this text file?\nADDITIONAL INFO:\n\nEach \"entry\", or line, contains three fields - any one of which can be used as an index.\nThe update is is the form of the entire database - I would have to manually generate a diff\nThe queries are just looking up records and displaying the text.\nQuerying the database will be a fundamental task of the application.","AnswerCount":2,"Available Count":2,"Score":0.0996679946,"is_accepted":false,"ViewCount":336,"Q_Id":14795810,"Users Score":1,"Answer":"How often will the data be queried? On the one extreme, if once per day, you might use a sequential search more efficiently than maintaining a database or index.\nFor more queries and a daily update, you could build and maintain your own index for more efficient queries. Most likely, it would be worth a negligible (if any) sacrifice in speed to use an SQL database (or other database, depending on your needs) in return for simpler and more maintainable code.","Q_Score":2,"Tags":"python,sql,database,text","A_Id":14795870,"CreationDate":"2013-02-10T07:53:00.000","Title":"Large text database: Convert to SQL or use as is","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I dropped my database that I had previously created for django using :\ndropdb <database>\nbut when I go to the psql  prompt and say \\d, I still see the relations there :\nHow do I remove everything from postgres so that I can do everything from scratch ?","AnswerCount":2,"Available Count":2,"Score":0.0996679946,"is_accepted":false,"ViewCount":88,"Q_Id":14869718,"Users Score":1,"Answer":"Most likely somewhere along the line, you created your objects in the template1 database (or in older versions the postgres database) and every time you create a new db i thas all those objects in it.  You can either drop the template1 \/ postgres database and recreate it or connect to it and drop all those objects by hand.","Q_Score":0,"Tags":"python,django,postgresql","A_Id":14880796,"CreationDate":"2013-02-14T07:23:00.000","Title":"postgres : relation there even after dropping the database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I dropped my database that I had previously created for django using :\ndropdb <database>\nbut when I go to the psql  prompt and say \\d, I still see the relations there :\nHow do I remove everything from postgres so that I can do everything from scratch ?","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":88,"Q_Id":14869718,"Users Score":0,"Answer":"Chances are that you never created the tables in the correct schema in the first place.  Either that or your dropdb failed to complete.\nTry to drop the database again and see what it says.  If that appears to work then go in to postgres and type \\l, putting the output here.","Q_Score":0,"Tags":"python,django,postgresql","A_Id":14870374,"CreationDate":"2013-02-14T07:23:00.000","Title":"postgres : relation there even after dropping the database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"We have a Python application with over twenty modules, most of which are shared by several web and console applications.\nI've never had a clear understanding of the best practice for establishing and managing database connection in multi module Python apps.  Consider this example:\nI have a module defining an object class for Users. It has many defs for creating\/deleting\/updating users in the database.  The users.py module is imported into a) a console based utility, 2) a web.py based web application and 3) a constantly running daemon process.\nEach of these three application have different life cycles.  The daemon can open a connection and keep it open.  The console utility connects, does work, then dies.  Of course the http requests are atomic, however the web server is a daemon.\nI am currently opening, using then closing a connection inside each function in the Users class.  This seems the most inefficient, but it works in all examples.  An alternative used as a test is to declare and open a global connection for the entire module.  Another option would be to create the connection at the top application layer and pass references when instantiating classes, but this seems the worst idea to me.\nI know every application architecture is different.  I'm just wondering if there's a best practice, and what it would be?","AnswerCount":2,"Available Count":2,"Score":0.3799489623,"is_accepted":false,"ViewCount":6022,"Q_Id":14883346,"Users Score":4,"Answer":"MySQL connections are relatively fast, so this might not be a problem (i.e. you should measure). Most other databases take much more resources to create a connection.\nCreating a new connection when you need one is always the safest, and is a good first choice.  Some db libraries, e.g. SqlAlchemy, have connection pools built in that transparently will re-use connections for you correctly.\nIf you decide you want to keep a connection alive so that you can re-use it, there are a few points to be aware of:\n\nConnections that are only used for reading are easier to re-use than connections that that you've used to modify database data.\nWhen you start a transaction on a connection, be careful that nothing else can use that connection for something else while you're using it.\nConnections that sit around for a long time get stale and can be closed from underneath you, so if you're re-using a connection you'll need to check if it is still \"alive\", e.g. by sending \"select 1\" and verifying that you get a result.\n\nI would personally recommend against implementing your own connection pooling algorithm.  It's really hard to debug when things go wrong.  Instead choose a db library that does it for you.","Q_Score":17,"Tags":"python,mysql","A_Id":14883719,"CreationDate":"2013-02-14T20:20:00.000","Title":"How should I establish and manage database connections in a multi-module Python app?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"We have a Python application with over twenty modules, most of which are shared by several web and console applications.\nI've never had a clear understanding of the best practice for establishing and managing database connection in multi module Python apps.  Consider this example:\nI have a module defining an object class for Users. It has many defs for creating\/deleting\/updating users in the database.  The users.py module is imported into a) a console based utility, 2) a web.py based web application and 3) a constantly running daemon process.\nEach of these three application have different life cycles.  The daemon can open a connection and keep it open.  The console utility connects, does work, then dies.  Of course the http requests are atomic, however the web server is a daemon.\nI am currently opening, using then closing a connection inside each function in the Users class.  This seems the most inefficient, but it works in all examples.  An alternative used as a test is to declare and open a global connection for the entire module.  Another option would be to create the connection at the top application layer and pass references when instantiating classes, but this seems the worst idea to me.\nI know every application architecture is different.  I'm just wondering if there's a best practice, and what it would be?","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":6022,"Q_Id":14883346,"Users Score":16,"Answer":"The best method is to open a connection when you need to do some operations (like getting and\/or updating data); manipulate the data; write it back to the database in one query (very important for performance), and then close the connection.  Opening a connection is a fairly light process.  \nSome pitfalls for performance include\n\nopening the database when you won't definitely interact with it\nusing selectors that take more data than you need (e.g., getting data about all users and filtering it in Python, instead of asking MySQL to filter out the useless data)\nwriting values that haven't changed (e.g. updating all values of a user profile, when just their email has changed)\nhaving each field update the server individually (e.g., open the db, update the user email, close the db, open the db, update the user password, close the db, open th... you get the idea)\n\nThe bottom line is that it doesn't matter how many times you open the database, it's how many queries you run.  If you can get your code to join related queries, you've won the battle.","Q_Score":17,"Tags":"python,mysql","A_Id":14883590,"CreationDate":"2013-02-14T20:20:00.000","Title":"How should I establish and manage database connections in a multi-module Python app?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a MySQL database with around 10,000 articles in it, but that number will probably go up with time. I want to be able to search through these articles and pull out the most relevent results based on some keywords. I know there are a number of projects that I can plug into that can essentially do this for me. However, the application for this is very simple, and it would be nice to have direct control and working knowledge of how the whole thing operates. Therefore, I would like to look into building a very simple search engine from scratch in Python.\nI'm not even sure where to start, really. I could just dump everything from the MySQL DB into a list and try to sort that list based on relevance, however that seems like it would be slow, and get slower as the amount of database items increase. I could use some basic MySQL search to get the top 100 most relevant results from what MySQL thinks, then sort those 100. But that is a two step process which may be less efficient, and I might risk missing an article if it is just out of range.\nWhat are the best approaches I can take to this?","AnswerCount":2,"Available Count":1,"Score":0.2913126125,"is_accepted":false,"ViewCount":643,"Q_Id":14889206,"Users Score":3,"Answer":"The best bet for you to do \"Search Engine\" for the 10,000 Articles is to read \"Programming Collective Intelligence\" by Toby Segaran. Wonderful read and to save your time go to Chapter 4 of August 2007 issue.","Q_Score":0,"Tags":"python,mysql,search,search-engine","A_Id":14889522,"CreationDate":"2013-02-15T06:10:00.000","Title":"Search engine from scratch","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a situation where my script parse approx 20000 entries and save them to db. I have used transaction which takes around 35 seconds to save and also consume high memory since until committed queries are saved in memory.\nI have Found another way to write CSV then load into postgres using \"copy_from\" which is very fast. If anyone can suggest that if I should open file once at start then close file while loading to postgres or open file when single entry is ready to write then close.\nwhat will be the best approach to save memory utilization?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":90,"Q_Id":14890211,"Users Score":1,"Answer":"Reduce the size of your transactions?","Q_Score":0,"Tags":"python,file,postgresql,csv","A_Id":14890240,"CreationDate":"2013-02-15T07:45:00.000","Title":"File writing in python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"If we have a json format data file which stores all of our database data content, such as table name, row, and column, etc content, how can we use DB-API object to insert\/update\/delete data from json file into database, such as sqlite, mysql, etc.  Or please share if you have better idea to handle it. People said it is good to save database data information into json format, which will be much convenient to work with database in python. \nThanks so much! Please give advise!","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":454,"Q_Id":14942462,"Users Score":1,"Answer":"There's no magic way, you'll have to write a Python program to load your JSON data in a database. SQLAlchemy is a good tool to make it easier.","Q_Score":0,"Tags":"python,database,json,sqlalchemy,python-db-api","A_Id":14951638,"CreationDate":"2013-02-18T17:57:00.000","Title":"how will Python DB-API read json format data into an existing database?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"Example scenario:\nMySQL running a single server -> HOSTNAME\nTwo MySQL databases on that server -> USERS ,  GAMES .\nTask -> Fetch 10 newest games from GAMES.my_games_table ,  and fetch users playing those games from USERS.my_users_table ( assume no joins )\nIn Django as well as Python MySQLdb , why is having one cursor for each database more preferable ?\nWhat is the disadvantage of an extended cursor which is single per MySQL server and can switch databases ( eg by querying \"use USERS;\" ), and then work on corresponding database \nMySQL connections are cheap, but isn't single connection better than many , if there is a linear flow and no complex tranasactions which might need two cursors ?","AnswerCount":3,"Available Count":3,"Score":1.2,"is_accepted":true,"ViewCount":1351,"Q_Id":14986129,"Users Score":10,"Answer":"A shorter answer would be, \"MySQL doesn't support that type of cursor\", so neither does Python-MySQL, so the reason one connection command is preferred is because that's the way MySQL works. Which is sort of a tautology.\nHowever, the longer answer is:\n\nA 'cursor', by your definition, would be some type of object accessing tables and indexes within an RDMS, capable of maintaining its state.\nA 'connection', by your definition, would accept commands, and either allocate or reuse a cursor to perform the action of the command, returning its results to the connection.\nBy your definition, a 'connection' would\/could manage multiple cursors.\nYou believe this would be the preferred\/performant way to access a database as 'connections' are expensive, and 'cursors' are cheap.\n\nHowever:\n\nA cursor in MySQL (and other RDMS) is not a the user-accessible mechanism for performing operations. MySQL (and other's) perform operations in as \"set\", or rather, they compile your SQL command into an internal list of commands, and do numerous, complex bits depending on the nature of your SQL command and your table structure.\nA cursor is a specific mechanism, utilized within stored procedures (and there only), giving the developer a way to work with data in a procedural way.\nA 'connection' in MySQL is what you think of as a 'cursor', sort of. MySQL does not expose it's internals for you as an iterator, or pointer, that is merely moving over tables. It exposes it's internals as a 'connection' which accepts SQL and other commands, translates those commands into an internal action, performs that action, and returns it's result to you.\nThis is the difference between a 'set' and a 'procedural' execution style (which is really about the granularity of control you, the user, is given access to, or at least, the granularity inherent in how the RDMS abstracts away its internals when it exposes them via an API).","Q_Score":6,"Tags":"python,mysql,django,mysql-python","A_Id":15328753,"CreationDate":"2013-02-20T17:27:00.000","Title":"Why django and python MySQLdb have one cursor per database?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Example scenario:\nMySQL running a single server -> HOSTNAME\nTwo MySQL databases on that server -> USERS ,  GAMES .\nTask -> Fetch 10 newest games from GAMES.my_games_table ,  and fetch users playing those games from USERS.my_users_table ( assume no joins )\nIn Django as well as Python MySQLdb , why is having one cursor for each database more preferable ?\nWhat is the disadvantage of an extended cursor which is single per MySQL server and can switch databases ( eg by querying \"use USERS;\" ), and then work on corresponding database \nMySQL connections are cheap, but isn't single connection better than many , if there is a linear flow and no complex tranasactions which might need two cursors ?","AnswerCount":3,"Available Count":3,"Score":0.1325487884,"is_accepted":false,"ViewCount":1351,"Q_Id":14986129,"Users Score":2,"Answer":"As you say, MySQL connections are cheap, so for your case, I'm not sure there is a technical advantage either way, outside of code organization and flow. It might be easier to manage two cursors than to keep track of which database a single cursor is currently talking to by painstakingly tracking SQL 'USE' statements. Mileage with other databases may vary -- remember that Django strives to be database-agnostic.\nAlso, consider the case where two different databases, even on the same server, require different access credentials. In such a case, two connections will be necessary, so that each connection can successfully authenticate.","Q_Score":6,"Tags":"python,mysql,django,mysql-python","A_Id":15302237,"CreationDate":"2013-02-20T17:27:00.000","Title":"Why django and python MySQLdb have one cursor per database?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Example scenario:\nMySQL running a single server -> HOSTNAME\nTwo MySQL databases on that server -> USERS ,  GAMES .\nTask -> Fetch 10 newest games from GAMES.my_games_table ,  and fetch users playing those games from USERS.my_users_table ( assume no joins )\nIn Django as well as Python MySQLdb , why is having one cursor for each database more preferable ?\nWhat is the disadvantage of an extended cursor which is single per MySQL server and can switch databases ( eg by querying \"use USERS;\" ), and then work on corresponding database \nMySQL connections are cheap, but isn't single connection better than many , if there is a linear flow and no complex tranasactions which might need two cursors ?","AnswerCount":3,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":1351,"Q_Id":14986129,"Users Score":0,"Answer":"One cursor per database is not necessarily preferable, it's just the default behavior.\nThe rationale is that different databases are more often than not on different servers, use different engines, and\/or need different initialization options. (Otherwise, why should you be using different \"databases\" in the first place?)\nIn your case, if your two databases are just namespaces of tables (what should be called \"schemas\" in SQL jargon) but reside on the same MySQL instance, then by all means use a single connection. (How to configure Django to do so is actually an altogether different question.)\nYou are also right that a single connection is better than two, if you only have a single thread and don't actually need two database workers at the same time.","Q_Score":6,"Tags":"python,mysql,django,mysql-python","A_Id":15421235,"CreationDate":"2013-02-20T17:27:00.000","Title":"Why django and python MySQLdb have one cursor per database?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm in the process of building a Django powered site that is backed by a MySQL server. This MySQL server is going to be accessed from additional sources, other than the website, to read and write table data; such as a program that users run locally which connects to the database.\nCurrently the program running locally is using the MySQL\/C Connector library to connect directly to the sql server and execute queries. In a final release to the public this seems insecure, since I would be exposing the connection string to the database in the code or in a configuration file.\nOne alternative I'm considering is having all queries be sent to the Django website (authenticated with a user's login and password) and then the site will sanitize and execute the queries on the user's behalf and return the results to them.\nThis has a number of downsides that I can think of. The webserver will be under a much larger load by processing all the SQL queries and this could potentially exceed the limit of my host. Additionally, I would have to figure out some way of serializing and transmitting the sql results in Python and then unserializing them in C\/C++ on the client side. This would be a decent amount of custom code to write and maintain.\nAny other downsides to this approach people can think of?\nDoes this sound reasonable and if it does, anything that could ease working on it; such as Python or C libraries to help develop the proxy interface?\nIf it sounds like a bad idea, any suggestions for alternative solutions i.e. a Python library that specializes in this type of proxy sql server logic, a method of encrypting sql connection strings so I can securely use my current solution, etc...?\nLastly, is this a valid concern? The database currently doesn't hold any terribly sensitive information about users (most sensitive would be their email and their site password which they may have reused from another source) but it could in the future which is my cause for concern if it's not secure.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":377,"Q_Id":14991783,"Users Score":1,"Answer":"This is a completely valid concern and a very common problem.  You have described creating a RESTful API.  I guess it could be considered a proxy to a database but is not usually referred to as a proxy.\nDjango is a great tool to use to use to accomplish this.  Django even has a couple packages that will assist in speedy development, Django REST Framework, Tastiepy, and django-piston are the most popular. Of course you could just use plain old Django.  \nYour Django project would be the only thing that interfaces with the  database and clients can send authenticated requests to Django; so clients will never connect directly to your database. This will give you fine grained permission control on a per client, per resource basis.  \n\nThe webserver will be under a much larger load by processing all the\n  SQL queries and this could potentially exceed the limit of my host\n\nI believe scaling a webservice is going to be a lot easier then scaling direct connections from your clients to your database.  There are many tried and true methods for scaling apps that have hundreds of requests per seconds to their databases. Because you have Django between you and the webserver you can implement caching for frequently requested resources.\n\nAdditionally, I would have to figure out some way of serializing and\n  transmitting the SQL results in Python and then unserializing them in\n  C\/C++ on the client side\n\nThis should be a moot issue.  There are lots of extremely popular data interchange formats. I have never used C\/C++ but a quick search I saw a couple of c\/c++ json serializers.  python has JSON built in for free, there shouldn't be any custom code to maintain regarding this if you use a premade C\/C++ JSON library.\n\nAny other downsides to this approach people can think of?\n\nI don't think there are any downsides,  It is a tried and true method.  It has been proven for a decade and the most popular sites in the world expose themselves through restful apis\n\nDoes this sound reasonable and if it does, anything that could ease\n  working on it; such as Python or C libraries to help develop the proxy\n  interface?\n\nIt sounds very reasonable, the Django apps I mentioned at the beginning of the answer should provide some boiler plate to allow you to get started on your API quicker.","Q_Score":3,"Tags":"c++,python,mysql,c,django","A_Id":14992070,"CreationDate":"2013-02-20T23:21:00.000","Title":"Django as a mysql proxy server?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a postgre database with a timestamp column and I have a REST service in Python that executes a query in the database and returns data to a JavaScript front-end to plot a graph using flot.\nNow the problem I have is that flot can automatically handle the date using JavaScript's TIMESTAMP, but I don't know how to convert the Postgre timestamps to JavaScript TIMESTAMP (YES a timestamp, not a date stop editing if you don't know the answer) in Python. I don't know if this is the best approach (maybe the conversion can be done in JavaScript?). Is there a way to do this?","AnswerCount":2,"Available Count":1,"Score":0.2913126125,"is_accepted":false,"ViewCount":4296,"Q_Id":15031856,"Users Score":3,"Answer":"You can't send a Python or Javascript \"datetime\" object over JSON. JSON only accepts more basic data types like Strings, Ints, and Floats.\nThe way I usually do it is send it as text, using Python's datetime.isoformat() then parse it on the Javascript side.","Q_Score":8,"Tags":"javascript,python,postgresql,flot","A_Id":15032100,"CreationDate":"2013-02-22T19:33:00.000","Title":"Converting postgresql timestamp to JavaScript timestamp in Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"The first element of arrays (in most programming languages) has an id (index) of 0. The first element (row) of MySQL tables has an (auto incremented) id of 1. The latter seems to be the exception.","AnswerCount":3,"Available Count":2,"Score":0.2605204458,"is_accepted":false,"ViewCount":2295,"Q_Id":15055175,"Users Score":4,"Answer":"The better question to ask is \"why are arrays zero-indexed?\"  The reason has to do with pointer arithmetic.  The index of an array is an offset relative to the pointer address.  In C++, given array char x[5], the expressions x[1] and *(x + 1) are equivalent, given that sizeof(char) == 1.\nSo auto increment fields starting at 1 make sense.  There is no real correlation between arrays and these fields.","Q_Score":5,"Tags":"php,python,mysql,ruby","A_Id":15056205,"CreationDate":"2013-02-24T18:40:00.000","Title":"Why does MySQL count from 1 and not 0?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"The first element of arrays (in most programming languages) has an id (index) of 0. The first element (row) of MySQL tables has an (auto incremented) id of 1. The latter seems to be the exception.","AnswerCount":3,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":2295,"Q_Id":15055175,"Users Score":0,"Answer":"The main reason I suppose is that a row in a database isnt an array and the autoincrement value isnt an index in the sense that an array index is.  The primary key id can be any value and to a great extent it is simply essential it is unique and is not guaranteed to be anything else (for example you can delete a row and it won't renumber).\nThis is a little like comparing apples and oranges!\nArray start at 0 because that's the first number.  Autoinc fields start at whatever number you want them too, and in that case we would all rather it was 1.","Q_Score":5,"Tags":"php,python,mysql,ruby","A_Id":15055977,"CreationDate":"2013-02-24T18:40:00.000","Title":"Why does MySQL count from 1 and not 0?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"The DBF files are updated every few hours. We need to import new records into MySQL and skip duplicates. I don't have any experience with DBF files but as far as I can tell a handful of the one's we're working with don't have unique IDs. \nI plan to use Python if there are no ready-made utilities that do this.","AnswerCount":2,"Available Count":1,"Score":-0.0996679946,"is_accepted":false,"ViewCount":2974,"Q_Id":15059749,"Users Score":-1,"Answer":"When you say you are using dBase, I presume you have access to the (.) dot prompt.\nAt dot prompt convert the .dbf file into a delimited text file.\nReconvert the delimited text file into a MySql data file with the necessary command in \nMySql. I do not know the actual command for it.  All DBMS will have commands to do that\nwork.\nFor eliminiating the duplicates you will have to do it at the time of populating the \ndata to the .dbf file through a programme written in dBase.","Q_Score":0,"Tags":"python,mysql,dbf,dbase","A_Id":16302184,"CreationDate":"2013-02-25T03:45:00.000","Title":"What's the best way to routinely import DBase (dbf) files into MySQL tables?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm doing a small web application which might need to eventually scale somewhat, and am curious about Google App Engine.  However, I am experiencing a problem with the development server (dev_appserver.py):\nAt seemingly random, requests will take 20-30 seconds to complete, even if there is no hard computation or data usage.  One request might be really quick, even after changing a script of static file, but the next might be very slow.  It seems to occur more systematically if the box has been left for a while without activity, but not always.\nCPU and disk access is low during the period. There is not allot of data in my application either.  \nDoes anyone know what could cause such random slowdowns? I've Google'd and searched here, but need some pointers.. \/:  I've also tried --clear_datastore and --use_sqlite, but the latter gives an error: DatabaseError('file is encrypted or is not a database',).  Looking for the file, it does not seem to exist.\nI am on Windows 8, python 2.7 and the most recent version of the App Engine SDK.","AnswerCount":2,"Available Count":2,"Score":0.1973753202,"is_accepted":false,"ViewCount":237,"Q_Id":15098051,"Users Score":2,"Answer":"Don't worry about it. It (IIRC) keeps the whole DB (datastore) in memory using a \"emulation\" of the real thing. There are lots of other issues that you won't see when deployed. \nI'd suggest that your hard drive is spinning down and the delay you see is it taking a few seconds to wake back up. \nIf this becomes a problem, develop using the deployed version. It's not so different.","Q_Score":2,"Tags":"python,google-app-engine","A_Id":15098634,"CreationDate":"2013-02-26T19:54:00.000","Title":"Google App Engine development server random (?) slowdowns","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I'm doing a small web application which might need to eventually scale somewhat, and am curious about Google App Engine.  However, I am experiencing a problem with the development server (dev_appserver.py):\nAt seemingly random, requests will take 20-30 seconds to complete, even if there is no hard computation or data usage.  One request might be really quick, even after changing a script of static file, but the next might be very slow.  It seems to occur more systematically if the box has been left for a while without activity, but not always.\nCPU and disk access is low during the period. There is not allot of data in my application either.  \nDoes anyone know what could cause such random slowdowns? I've Google'd and searched here, but need some pointers.. \/:  I've also tried --clear_datastore and --use_sqlite, but the latter gives an error: DatabaseError('file is encrypted or is not a database',).  Looking for the file, it does not seem to exist.\nI am on Windows 8, python 2.7 and the most recent version of the App Engine SDK.","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":237,"Q_Id":15098051,"Users Score":0,"Answer":"Does this happen in all web browsers? I had issues like this when viewing a local app engine dev site in several browsers at the same time for cross-browser testing. IE would then struggle, with requests taking about as long as you describe.\nIf this is the issue, I found the problems didn't occur with IETester.\nSorry if it's not related, but I thought this was worth mentioning just in case.","Q_Score":2,"Tags":"python,google-app-engine","A_Id":15106246,"CreationDate":"2013-02-26T19:54:00.000","Title":"Google App Engine development server random (?) slowdowns","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"How do I save an open excel file using python= I currently read the excel workbook using XLRD but I need to save the excel file so any changes the user inputs are read. \nI have done this using a VBA script from within excel which saves the workbook every x seconds, but this is not ideal.","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":758,"Q_Id":15114329,"Users Score":0,"Answer":"It looks like XLRD is used for reading the data, not interfacing with excel. So no, unless you use a different library using python is not the best way to do this, what is wrong with the VBA script?","Q_Score":0,"Tags":"python,excel,xlrd","A_Id":15114556,"CreationDate":"2013-02-27T14:17:00.000","Title":"Save open excel file using python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Django needs MySQL-python package to manipulate MySQL, but MySQL-python doesn't support Python 3.3. I have tried MySQL-for-Python-3, but it doesn't work.\nPlease help! Thanks a lot!","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":713,"Q_Id":15202503,"Users Score":0,"Answer":"As others have noted, Python 3 support in Django 1.5 is \"experimental\" and, as such, not everything should be expected to work. \nThat being said, if you absolutely need to get this working, you may be able to run the 2to3 tool on a source version of MySQL-python to translate it to Python 3 (and build against Python 3 headers if required).","Q_Score":1,"Tags":"python,mysql,django","A_Id":15203056,"CreationDate":"2013-03-04T13:18:00.000","Title":"How can I use MySQL with Python 3.3 and Django 1.5?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"So, in order to avoid the \"no one best answer\" problem, I'm going to ask, not for the best way, but the standard or most common way to handle sessions when using the Tornado framework.  That is, if we're not using 3rd party authentication (OAuth, etc.), but rather we have want to have our own Users table with secure cookies in the browser but most of the session info stored on the server, what is the most common way of doing this?  I have seen some people using Redis, some people using their normal database (MySQL or Postgres or whatever), some people using memcached.\nThe application I'm working on won't have millions of users at a time, or probably even thousands.  It will need to eventually get some moderately complex authorization scheme, though.  What I'm looking for is to make sure we don't do something \"weird\" that goes down a different path than the general Tornado community, since authentication and authorization, while it is something we need, isn't something that is at the core of our product and so isn't where we should be differentiating ourselves.  So, we're looking for what most people (who use Tornado) are doing in this respect, hence I think it's a question with (in theory) an objectively true answer.\nThe ideal answer would point to example code, of course.","AnswerCount":4,"Available Count":3,"Score":1.2,"is_accepted":true,"ViewCount":14722,"Q_Id":15254538,"Users Score":14,"Answer":"Tornado designed to be stateless and don't have session support out of the box. \nUse secure cookies to store sensitive information like user_id. \nUse standard cookies to store not critical information. \nFor storing large objects - use standard scheme - MySQL + memcache.","Q_Score":14,"Tags":"python,tornado","A_Id":15265556,"CreationDate":"2013-03-06T17:55:00.000","Title":"standard way to handle user session in tornado","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"So, in order to avoid the \"no one best answer\" problem, I'm going to ask, not for the best way, but the standard or most common way to handle sessions when using the Tornado framework.  That is, if we're not using 3rd party authentication (OAuth, etc.), but rather we have want to have our own Users table with secure cookies in the browser but most of the session info stored on the server, what is the most common way of doing this?  I have seen some people using Redis, some people using their normal database (MySQL or Postgres or whatever), some people using memcached.\nThe application I'm working on won't have millions of users at a time, or probably even thousands.  It will need to eventually get some moderately complex authorization scheme, though.  What I'm looking for is to make sure we don't do something \"weird\" that goes down a different path than the general Tornado community, since authentication and authorization, while it is something we need, isn't something that is at the core of our product and so isn't where we should be differentiating ourselves.  So, we're looking for what most people (who use Tornado) are doing in this respect, hence I think it's a question with (in theory) an objectively true answer.\nThe ideal answer would point to example code, of course.","AnswerCount":4,"Available Count":3,"Score":1.0,"is_accepted":false,"ViewCount":14722,"Q_Id":15254538,"Users Score":17,"Answer":"Here's how it seems other micro frameworks handle sessions (CherryPy, Flask for example):\n\nCreate a table holding session_id and whatever other fields you'll want to track on a per session basis. Some frameworks will allow you to just store this info in a file on a per user basis, or will just store things directly in memory. If your application is small enough, you may consider those options as well, but a database should be simpler to implement on your own.\nWhen a request is received (RequestHandler initialize() function I think?) and there is no session_id cookie, set a secure session-id using a random generator. I don't have much experience with Tornado, but it looks like setting a secure cookie should be useful for this. Store that session_id and associated info in your session table. Note that EVERY user will have a session, even those not logged in. When a user logs in, you'll want to attach their status as logged in (and their username\/user_id, etc) to their session.\nIn your RequestHandler initialize function, if there is a session_id cookie, read in what ever session info you need from the DB and perhaps create your own Session object to populate and store as a member variable of that request handler.\n\nKeep in mind sessions should expire after a certain amount of inactivity, so you'll want to check for that as well. If you want a \"remember me\" type log in situation, you'll have to use a secure cookie to signal that (read up on this at OWASP to make sure it's as secure as possible, thought again it looks like Tornado's secure_cookie might help with that), and upon receiving a timed out session you can re-authenticate a new user by creating a new session and transferring whatever associated info into it from the old one.","Q_Score":14,"Tags":"python,tornado","A_Id":16320593,"CreationDate":"2013-03-06T17:55:00.000","Title":"standard way to handle user session in tornado","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"So, in order to avoid the \"no one best answer\" problem, I'm going to ask, not for the best way, but the standard or most common way to handle sessions when using the Tornado framework.  That is, if we're not using 3rd party authentication (OAuth, etc.), but rather we have want to have our own Users table with secure cookies in the browser but most of the session info stored on the server, what is the most common way of doing this?  I have seen some people using Redis, some people using their normal database (MySQL or Postgres or whatever), some people using memcached.\nThe application I'm working on won't have millions of users at a time, or probably even thousands.  It will need to eventually get some moderately complex authorization scheme, though.  What I'm looking for is to make sure we don't do something \"weird\" that goes down a different path than the general Tornado community, since authentication and authorization, while it is something we need, isn't something that is at the core of our product and so isn't where we should be differentiating ourselves.  So, we're looking for what most people (who use Tornado) are doing in this respect, hence I think it's a question with (in theory) an objectively true answer.\nThe ideal answer would point to example code, of course.","AnswerCount":4,"Available Count":3,"Score":0.1973753202,"is_accepted":false,"ViewCount":14722,"Q_Id":15254538,"Users Score":4,"Answer":"The key issue with sessions is not where to store them, is to how to expire them intelligently. Regardless of where sessions are stored, as long as the number of stored sessions is reasonable (i.e. only active sessions plus some surplus are stored), all this data is going to fit in RAM and be served fast. If there is a lot of old junk you may expect unpredictable delays (the need to hit the disk to load the session).","Q_Score":14,"Tags":"python,tornado","A_Id":16346968,"CreationDate":"2013-03-06T17:55:00.000","Title":"standard way to handle user session in tornado","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I have a problem in kettle connecting python. In kettle, I only find the js script module.\nDoes kettle support python directly? I mean, can I call a python script in kettle without using js or others?\nBy the way, I want to move data from Oracle to Mongo regularly. I choose to use python to implement the transformation. So without external files, does it have some easy methods to keep the synchronization between a relational db and a no-rdb?\nThanks a lot.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":6043,"Q_Id":15263196,"Users Score":2,"Answer":"It doesnt support it directly from what I've seen.\nHowever there is a mongodb input step. And a lot of work has been done on it recently ( and still ongoing.  \nSo given there is a mongodb input step, if you're using an ETL tool already then why would you want to make it execute a python script to do the job??","Q_Score":3,"Tags":"python,kettle","A_Id":15274794,"CreationDate":"2013-03-07T04:39:00.000","Title":"how to call python script in kettle","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm working on a Django application that needs to interact with a mongoDB instance ( preferably through django's ORM) The meat of the application still uses a relational database - but I just need to interact with mongo for a single specific model. \nWhich mongo driver\/subdriver for python will suite my needs best ?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":258,"Q_Id":15314025,"Users Score":0,"Answer":"You could use django-nonrel which is a fork of Django and will let you use the same ORM.\nIf you dont want a forked Django you could use MongoEngine which has a similar syntax otherwise just raw pymongo.","Q_Score":0,"Tags":"python,django,mongodb","A_Id":15498874,"CreationDate":"2013-03-09T18:00:00.000","Title":"Use MongoDB with Django but also use relational database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have created a cronjob in Python. The purpose is to insert data into a table from another one based on certain conditions. There is more than 65000 record to be inserted. \nI have executed the cronjob and has seen more than 25000 records inserted. But after that the record are getting automatically deleted from that table. Even the records that has already inserted into the table that day before executing the cronjob is getting deleted.\n   \"The current database is hosted in Xeround cloud.\"\nIs MySQL doing so, i.e some kind of rollback or something\nDoes anybody have any idea about this. Please give me a solution.\nThanks in advance..","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":637,"Q_Id":15332618,"Users Score":1,"Answer":"Run your django orm statement in the django shell and print the traceback. Look for delete statements in the django traceback sql.","Q_Score":4,"Tags":"mysql,django,python-2.7,xeround","A_Id":15388969,"CreationDate":"2013-03-11T06:40:00.000","Title":"Records getting deleted from Mysql table automatically","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm currently exploring using python to develop my server-side implementation. I've decided to use SQLAlchemy for database stuff.\nWhat I'm not currently to sure about is how it should be set up so that more than one developer can work on the project. For the code it is not a problem but how do I handle the database modifications? How do the users sync databases and how should potential data be set up? Should\/can each developer use their own sqlite db for development?\nFor production postgresql will be used but the developers must be able to work offline.","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":195,"Q_Id":15345864,"Users Score":0,"Answer":"Make sure you have a python programs or programs to fill databases with test data from scratch. It allows each developer to work from different starting points, but also test with the same environment.","Q_Score":0,"Tags":"python,database,development-environment","A_Id":15346132,"CreationDate":"2013-03-11T18:28:00.000","Title":"Multi developer environment python and sqlalchemy","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"So I know how to download Excel files from Google Drive in .csv format. However, since .csv files do not support multiple sheets, I have developed a system in a for loop to add the '&grid=tab_number' to the file download url so that I can download each sheet as its own .csv file. The problem I have run into is finding out how many sheets are in the excel workbook on the Google Drive so I know how many times to set the for loop for.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":95,"Q_Id":15456709,"Users Score":0,"Answer":"Ended up just downloading with xlrd and using that. Thanks for the link Rob.","Q_Score":0,"Tags":"python,excel,google-drive-api","A_Id":15505507,"CreationDate":"2013-03-17T01:39:00.000","Title":"Complicated Excel Issue with Google API and Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":1,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a huge csv file which contains millions of records and I want to load it into Netezza DB using python script I have tried simple insert query but it is very very slow. \nCan point me some example python script or some idea how can I do the same?\nThank you","AnswerCount":3,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":4583,"Q_Id":15592980,"Users Score":0,"Answer":"You need to get the nzcli installed on the machine that you want to run nzload from - your sysadmin should be able to put it on your unix\/linux application server. There's a detailed process to setting it all up, caching the passwords, etc - the sysadmin should be able to do that to.\nOnce it is set up, you can create NZ control files to point to your data files and execute a load. The Netezza Data Loading guide has detailed instructions on how to do all of this (it can be obtained through IBM).\nYou can do it through aginity as well if you have the CREATE EXTERNAL TABLE privledge - you can do a INSERT INTO FROM EXTERNAL ... REMOTESOURCE ODBC to load the file from an ODBC connection.","Q_Score":2,"Tags":"python,netezza","A_Id":15643468,"CreationDate":"2013-03-23T22:45:00.000","Title":"How to use NZ Loader (Netezza Loader) through Python Script?","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a huge csv file which contains millions of records and I want to load it into Netezza DB using python script I have tried simple insert query but it is very very slow. \nCan point me some example python script or some idea how can I do the same?\nThank you","AnswerCount":3,"Available Count":2,"Score":0.0665680765,"is_accepted":false,"ViewCount":4583,"Q_Id":15592980,"Users Score":1,"Answer":"you can use nz_load4  to load the data,This is the support utility \/nz\/support\/contrib\/bin\nthe syntax is same like nzload,by default nz_load4 will load the data using 4 thread and you can go upto 32 thread by using -tread option\nfor more details use nz_load4 -h \nThis will create the log files based on the number of thread,like if","Q_Score":2,"Tags":"python,netezza","A_Id":17522337,"CreationDate":"2013-03-23T22:45:00.000","Title":"How to use NZ Loader (Netezza Loader) through Python Script?","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"For my app, I need to determine the nearest points to some other point and I am looking for a simple but relatively fast (in terms of performance) solution. I was thinking about using PostGIS and GeoDjango but I think my app is not really that \"geographic\" (I still don't really know what that means though). The geographic part (around 5 percent of the whole) is that I need to keep coordinates of objects (people and places) and then there is this task to find the nearest points. To put it simply, PostGIS and GeoDjango seems to be an overkill here. \nI was also thinking of django-haystack with SOLR or Elasticsearch because I am going to need a strong, strong text search capabilities and these engines have also these \"geographic\" features. But not sure about it either as I am afraid of core db <-> search engine db synchronisation and hardware requirements for these engines. At the moment I am more akin to use posgreSQL trigrams and some custom way to do that \"find near points problem\". Is there any good one?","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":689,"Q_Id":15593572,"Users Score":0,"Answer":"You're probably right, PostGIS\/GeoDjango is probably overkill, but making your own Django app would not be too much trouble for your simple task. Django offers a lot in terms of templating, etc. and with the built in admin makes it pretty easy to enter single records. And GeoDjango is part of contrib, so you can always use it later if your project needs it.","Q_Score":0,"Tags":"python,django,postgresql,postgis,geodjango","A_Id":15593621,"CreationDate":"2013-03-24T00:09:00.000","Title":"Django + postgreSQL: find near points","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"In my company we want to build an application in Google app engine which will manage user provisioning to Google apps. But we do not really know what data source to use?\nWe made two propositions :\n\nspreadsheet which will contains users' data and we will use spreadsheet API to get this data and use it for user provisioning\nDatastore which will contains also users' data and this time we will use Datastore API.\n\nPlease note that my company has 3493 users and we do not know too many advantages and disadvantages of each solution.\nAny suggestions please?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":248,"Q_Id":15671591,"Users Score":0,"Answer":"If you use the Datastore API, you will also need to build out a way to manage users data in the system.\nIf you use Spreadsheets, that will serve as your way to manage users data, so in that way managing the data would be taken care of for you.\nThe benefits to use the Datastore API would be if you'd like to have a seamless integration of managing the user data into your application.  Spreadsheet integration would remain separate from your main application.","Q_Score":0,"Tags":"python,google-app-engine,google-sheets,google-cloud-datastore","A_Id":15671792,"CreationDate":"2013-03-27T23:37:00.000","Title":"Datastore vs spreadsheet for provisioning Google apps","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"If I've been given a Query object that I didn't construct, is there a way to directly modify its WHERE clause?  I'm really hoping to be able remove some AND statements or replace the whole FROM clause of a query instead of starting from scratch.  \nI'm aware of the following methods to modify the SELECT clause:\nQuery.with_entities(), Query.add_entities(), Query.add_columns(), Query.select_from()\nwhich I think will also modify the FROM.  And I see that I can view the WHERE clause with Query.whereclause, but the docs say that it's read-only.  \nI realize I'm thinking in SQL terms, but I'm more familiar with those concepts than the ORM, at this point.  Any help is very appreciated.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":489,"Q_Id":15705511,"Users Score":2,"Answer":"you can modify query._whereclause directly, but I'd seek to find a way to not have this issue in the first place - whereever it is that the Query is generated should be factored out so that the non-whereclause version is made available.","Q_Score":2,"Tags":"python,orm,sqlalchemy,where-clause","A_Id":15707037,"CreationDate":"2013-03-29T14:41:00.000","Title":"SQLAlchemy ORM: modify WHERE clause","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have installd Python 2.7.3 on Linux 64 bit machine. I have Oracle 11g client(64bit) as well installed. And I set ORACLE_HOME, PATH, LD_LIBRARY_PATH, and installed cx_oracle 5.1.2 version for Python 2.7 & Oracle 11g. But ldd command on cx_oracle is unable to find libclntsh.so.11.1.\nI tried creating symlinks to libclntsh.so.11.1 under \/usr\/lib64, updated oracle.conf file under \/etc\/ld.so.conf.d\/. Tried all possible solutions that have been discussed on this issue on the forums, but no luck.\nPlease let me know what am missing.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":412,"Q_Id":15740464,"Users Score":0,"Answer":"The issue with me was that I installed python, cx_oracle as root but Oracle client installation was done by \"oracle\" user. I got my own oracle installation and that fixed the issue. \nLater I ran into PyUnicodeUCS4_DecodeUTF16 issues with Python and for that I had to install python with \u2014enable-unicode=ucs4 option","Q_Score":0,"Tags":"python,cx-oracle","A_Id":15745441,"CreationDate":"2013-04-01T09:00:00.000","Title":"cx_oracle unable to find Oracle Client","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":0},{"Question":"I try to connect to a remote oracle server by cx_Oracle:\ndb = cx_Oracle.connect('username', 'password', dsn_tns)\nbut it says databaseError: ORA-12541 tns no listener","AnswerCount":3,"Available Count":1,"Score":0.0665680765,"is_accepted":false,"ViewCount":17494,"Q_Id":15772351,"Users Score":1,"Answer":"In my case it was due to the fact that my server port was wrong:\n\n.\/install_database_new.sh   localhost:1511 XE full \n\nI changed the port to \"1521\" and I could connect.","Q_Score":6,"Tags":"python,cx-oracle","A_Id":46728202,"CreationDate":"2013-04-02T19:10:00.000","Title":"ocx_Oracle ORA-12541 tns no listener","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm using Sqlalchemy in a multitenant Flask application and need to create tables on the fly when a new tenant is added. I've been using Table.create to create individual tables within a new Postgres schema (along with search_path modifications) and this works quite well.\nThe limitation I've found is that the Table.create method blocks if there is anything pending in the current transaction. I have to commit the transaction right before the .create call or it will block. It doesn't appear to be blocked in Sqlalchemy because you can't Ctrl-C it. You have to kill the process. So, I'm assuming it's something further down in Postgres.\nI've read in other answers that CREATE TABLE is transactional and can be rolled back, so I'm presuming this should be working. I've tried starting a new transaction with the current engine and using that for the table create (vs. the current Flask one) but that hasn't helped either.\nDoes anybody know how to get this to work without an early commit (and risking partial dangling data)?\nThis is Python 2.7, Postgres 9.1 and Sqlalchemy 0.8.0b2.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1872,"Q_Id":15774899,"Users Score":3,"Answer":"(Copy from comment)\nAssuming sess is the session, you can do sess.execute(CreateTable(tenantX_tableY)) instead.\nEDIT: CreateTable is only one of the things being done when calling table.create(). Use table.create(sess.connection()) instead.","Q_Score":0,"Tags":"python,postgresql,sqlalchemy,ddl,flask-sqlalchemy","A_Id":15775816,"CreationDate":"2013-04-02T21:38:00.000","Title":"How do you create a table with Sqlalchemy within a transaction in Postgres?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm writing a python app that connects to perforce on a daily basis. The app gets the contents of an excel file on perfoce, parses it, and copies some data to a database. The file is rather big, so I would like to keep track of which revision of the file the app last read on the database, this way i can check to see if the revision number is higher and avoid reading the file if it has not changed.\nI could make do with getting the revision number, or the changelist number when the file was last checked in \/ changed. Or if you have any other suggestion on how to accomplish my goal of avoiding doing an unnecessary read of the file.\nI'm using python 2.7 and the perforce-python API","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1797,"Q_Id":15795038,"Users Score":2,"Answer":"Several options come to mind.\n\nThe simplest approach would be to always let your program use the same client and let it sync the file. You could let your program call p4 sync and see if you get a new version or not. Let it continue if you get a new version. This approach has the advantage that you don't need to remember any states\/version from the previous run of your program.\nIf you don't like using a fixed client you could let your program always check the current head revision of the file in question: \np4 fstat \/\/depot\/path\/yourfile |grep headRev | sed 's\/.*headRev \\(.*\\)\/\\1\/'\nYou could store that version for the next run of your program in some temp file and compare versions each time.\nIf you run your program at fixed times (e.g. via cron) you could check the last modification time (either with p4 filelog or with p4 fstat) and if the time is between the time of the last run and the current time then you need to process the file. This option is a bit intricate since you need to parse those different time formats.","Q_Score":0,"Tags":"python,python-2.7,perforce","A_Id":15806216,"CreationDate":"2013-04-03T18:23:00.000","Title":"How to get head revision number of a file, or the changelist number when it was checked in \/ changed","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am searching for a persistent data storage solution that can handle heterogenous data stored on disk.  PyTables seems like an obvious choice, but the only information I can find on how to append new columns is a tutorial example.  The tutorial has the user create a new table with added column, copy the old table into the new table, and finally delete the old table.  This seems like a huge pain.  Is this how it has to be done?\nIf so, what are better alternatives for storing mixed data on disk that can accommodate new columns with relative ease?  I have looked at sqlite3 as well and the column options seem rather limited there, too.","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":2350,"Q_Id":15797163,"Users Score":5,"Answer":"Yes, you must create a new table and copy the original data.  This is because Tables are a dense format.  This gives it a huge performance benefits but one of the costs is that adding new columns is somewhat expensive.","Q_Score":5,"Tags":"python,pytables","A_Id":19470951,"CreationDate":"2013-04-03T20:13:00.000","Title":"Is the only way to add a column in PyTables to create a new table and copy?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm writing a web application in Python (on Apache server on a Linux system) that needs to connect to a Postgres database. It therefore needs a valid password for the database server. It seems rather unsatisfactory to hard code the password in my Python files.\nI did wonder about using a .pgpass file, but it would need to belong to the www-data user, right? By default, there is no \/home\/www-data directory, which is where I would have expected to store the .pgpass file. Can I just create such a directory and store the .pgpass file there? And if not, then what is the \"correct\" way to enable my Python scripts to connect to the database?","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":1239,"Q_Id":15895788,"Users Score":1,"Answer":"No matter what approach you use, other apps running as www-data will be able to read your password and log in as you to the database. Using peer auth won't help you out, it'll still trust all apps running under www-data.\nIf you want your application to be able to isolate its data from other databases you'll need to run it as a separate user ID. The main approaches with this are:\n\nUse the apache suexec module to run scripts as a separate user;\nUse fast-cgi (fcgi) or scgi to run the cgi as a different user; or\nHave the app run its own minimal HTTP server and have Apache reverse proxy for it\n\nOf these, by far the best option is usually to use scgi\/fcgi. It lets you easily run your app as a different unix user but avoids the complexity and overhead of reverse proxying.","Q_Score":3,"Tags":"python,apache,postgresql,mod-wsgi","A_Id":15897981,"CreationDate":"2013-04-09T07:23:00.000","Title":"\"Correct\" way to store postgres password in python website","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am having trouble finding this answer anywhere on the internet. I want to be able to monitor a row in a MySQL table for changes and when this occurs, run a Python function. This Python function I want to run has nothing to do with MySQL; it just enables a pin on a Raspberry Pi. I have tried looking into SQLAlchemy; however, I can't tell if it is a trigger or a data mapping. Is something like this even possible?\nThanks in advance!","AnswerCount":2,"Available Count":1,"Score":0.3799489623,"is_accepted":false,"ViewCount":6558,"Q_Id":15903357,"Users Score":4,"Answer":"What about a cron job instead of create a loop? I think it's a bit nicer.","Q_Score":1,"Tags":"python,sql,sqlalchemy,raspberry-pi","A_Id":15904750,"CreationDate":"2013-04-09T13:31:00.000","Title":"How to execute Python function when value in SQL table changes?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a couple of python scripts which I plan to put up on a server and run them repeatedly once a day. This python script does some calculation and finally uploads the data to a central database. Of course to connect to the database a password and username is required. Is it safe to input this username and password on my python script. If not is there any better way to do it?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":284,"Q_Id":15905113,"Users Score":0,"Answer":"Create a DB user with limited access rights, for example, to that only table where it uploads data to. Hardcode that user in your script or pass it as command line arguments. There is little else you can do for a automated script because it has to use some username and password to connect to the DB somehow.\nYou could encrypt the credentials and decrypt them in your script, but once a sufficiently determined attacker gets access to your user account and script extracting the username and password from a plain text script should not be too hard. You could use a compiled script to hide the credentials from the prying eyes, but again, it depends on how valuable access to your database is.","Q_Score":0,"Tags":"python","A_Id":15907470,"CreationDate":"2013-04-09T14:47:00.000","Title":"Connecting to a database using python and running it as a cron job","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"What's a reasonable default for pool_size in a ZODB.DB call in a multi-threaded web application?\nLeaving the actual default value 7 gives me some connection WARNINGs even when I'm the only one navigating through db-interacting handlers. Is it possible to set a number that's too high? What factors play into deciding what exactly to set it to?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":485,"Q_Id":15914198,"Users Score":4,"Answer":"The pool size is only a 'guideline'; the warning is logged when you exceed that size; if you were to use double the number of connections an CRITICAL log message would be registed instead. These are there to indicate you may be using too many connections in your application.\nThe pool will try to reduce the number of retained connections to the pool size as you close connections.\nYou need to set it to the maximum number of threads in your application. For Tornado, which I believe uses asynchronous events instead of threading almost exclusively, that might be harder to determine; if there is a maximum number of concurrent connections configurable in Tornado, then the pool size needs to be set to that number.\nI am not sure how the ZODB will perform when your application scales to hundreds or thousands of concurrent connections, though. I've so far only used it with at most 100 or so concurrent connections spread across several processes and even machines (using ZEO or RelStorage to serve the ZODB across those processes).\nI'd say that if most of these connections only read, you should be fine; it's writing on the same object concurrently that is ZODB's weak point as far as scalability is concerned.","Q_Score":2,"Tags":"python,connection-pooling,zodb","A_Id":15919692,"CreationDate":"2013-04-09T23:12:00.000","Title":"Reasonable settings for ZODB pool_size","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have to implement nosetests for Python code using a MongoDB store. Is there any python library which permits me initializing a mock in-memory MongoDB server?\nI am using continuous integration. So, I want my tests to be independent of any MongoDB running server. \nIs there a way to mock mongoDM Server in memory to test the code independently of connecting to a Mongo server?\nThanks in advance!","AnswerCount":4,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":14649,"Q_Id":15915031,"Users Score":4,"Answer":"I don\u2019t know about Python, but I had a similar concern with C#. I decided to just run a real instance of Mongo on my workstation pointed at an empty directory. It\u2019s not great because the code isn\u2019t isolated but it\u2019s fast and easy.\nOnly the data access layer actually calls Mongo during the test. The rest can rely on the mocks of the data access layer. I didn\u2019t feel like faking Mongo was worth the effort when really I want to verify the interaction with Mongo is correct anyway.","Q_Score":17,"Tags":"python,mongodb,python-2.7,pymongo","A_Id":15915744,"CreationDate":"2013-04-10T00:42:00.000","Title":"Use mock MongoDB server for unit test","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"We need to store a text field ( say 2000 characters) and its unique hash ( say SHA1 ) in a MySQL table.\nTo test that text already exists in the MySQL table, we generate SHA1 of the text , and find whether it exists in the unique field hash .\nNow lets assume there are two texts:\n\n\"This is the text which will be stored in the database, and its hash will be generated\"\n\"This is the text,which will be stored in the database and its hash will be generated.\"\n\nNotice the minor differences.\nLets say 1 has already been added to the database, the check for 2 will not work as their SHA1 hashes will be drastically different.\nOne obvious solution is to use Leveinstein distance, or difflib to iterate over all already added text fields to fine near matches from the MySQL table.\nBut that is not performance oriented.\nIs there a good hashing algorithm which has a correlation with the text content ? i.e. Two hashes generated for very similar texts will be very similar in themselves.\nThat way it would be easier to detect possible duplicates before adding them in the MySQL table.","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":496,"Q_Id":15919063,"Users Score":1,"Answer":"I highly doubt anything you're looking for exists, so I propose a simpler solution:\nCome up with a simple algorithm for normalizing your text, e.g.:\n\nNormalize whitespace\nRemove punctuation\n\nThen, calculate the hash of that and store it in a separate column (normalizedHash) or store an ID to a table of normalized hashes.  Then you can compare the two different entries by their normalized content.","Q_Score":1,"Tags":"python,mysql,string-matching","A_Id":15919118,"CreationDate":"2013-04-10T07:00:00.000","Title":"Good hashing algorithm with proximity to original text input , less avalanche effect?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I wrote a little script that copies files from bucket on one S3 account to the bucket in another S3 account.\nIn this script I use bucket.copy_key() function to copy key from one bucket in another bucket.\nI tested it, it works fine, but the question is: do I get charged for copying files between S3 to S3 in same region? \nWhat I'm worry about that may be I missed something in boto source code, and I hope it's not store the file on my machine, than send it to another S3. \nAlso (sorry, if its to much questions in one topic) if I upload and run this script from EC2 instance will I get charge for bandwidth?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":322,"Q_Id":15956099,"Users Score":3,"Answer":"If you are using the copy_key method in boto then you are doing server-side copying.  There is a very small per-request charge for COPY operations just as there are for all S3 operations but if you are copying between two buckets in the same region, there is no network transfer charges.  This is true whether you run the copy operations on your local machine or on an EC2 instance.","Q_Score":1,"Tags":"python,amazon-web-services,amazon-s3,boto,data-transfer","A_Id":15957021,"CreationDate":"2013-04-11T18:24:00.000","Title":"Will I get charge for transfering files between S3 accounts using boto's bucket.copy_key() function?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":1,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Things to note in advance:\n\nI am using wampserver 2.2\nIve forwarded port 80\nI added a rule to my firewall to accept traffic through port 3306\nI have added \"Allow from all\" in directory of \"A file i forget\"\nMy friend can access my phpmyadmin server through his browser \nI am quite the novice, so bear with me.\n\nI am trying to get my friend to be able to alter my databases on my phpmyadmin server through \npython. I am able to do so on the host machine using \"127.0.0.1\" as the HOST. My Question is, does he have to use my external ip as the HOST or my external ip\/phpmyadmin\/ as the HOST? And if using the external ip iscorrect...What could the problem be?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":120,"Q_Id":15958249,"Users Score":0,"Answer":"If your phpmyadmin runs on the same machine as mysql-server, 127.0.0.1 is enough (and safer if your mysql server binds to 127.0.0.1, rather than 0.0.0.0) if you use tcp(rather than unix socket).","Q_Score":0,"Tags":"python,sql,phpmyadmin,mysql-python,host","A_Id":16370493,"CreationDate":"2013-04-11T20:27:00.000","Title":"What do I use for HOST to connect to a remote server with mysqldb python?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"So there has been a lot of hating on singletons in python. I generally see that having a singleton is usually no good, but what about stuff that has side effects, like using\/querying a Database? Why would I make a new instance for every simple query, when I could reuse a present connection already setup again? What would be a pythonic approach\/alternative to this?\nThank you!","AnswerCount":2,"Available Count":2,"Score":0.0996679946,"is_accepted":false,"ViewCount":6703,"Q_Id":15958678,"Users Score":1,"Answer":"If you're using an object oriented approach, then abamet's suggestion of attaching the database connection parameters as class attributes makes sense to me. The class can then establish a single database connection which all methods of the class refer to as self.db_connection, for example.\nIf you're not using an object oriented approach, a separate database connection module can provide a functional-style equivalent. Devote a module to establishing a database connection, and simply import that module everywhere you want to use it. Your code can then refer to the connection as db.connection, for example. Since modules are effectively singletons, and the module code is only run on the first import, you will be re-using the same database connection each time.","Q_Score":7,"Tags":"python,database,singleton","A_Id":15960691,"CreationDate":"2013-04-11T20:53:00.000","Title":"DB-Connections Class as a Singleton in Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"So there has been a lot of hating on singletons in python. I generally see that having a singleton is usually no good, but what about stuff that has side effects, like using\/querying a Database? Why would I make a new instance for every simple query, when I could reuse a present connection already setup again? What would be a pythonic approach\/alternative to this?\nThank you!","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":6703,"Q_Id":15958678,"Users Score":7,"Answer":"Normally, you have some kind of object representing the thing that uses a database (e.g., an instance of MyWebServer), and you make the database connection a member of that object.\nIf you instead have all your logic inside some kind of function, make the connection local to that function. (This isn't too common in many other languages, but in Python, there are often good ways to wrap up multi-stage stateful work in a single generator function.)\nIf you have all the database stuff spread out all over the place, then just use a global variable instead of a singleton. Yes, globals are bad, but singletons are just as bad, and more complicated. There are a few cases where they're useful, but very rare. (That's not necessarily true for other languages, but it is for Python.) And the way to get rid of the global is to rethink you design. There's a good chance you're effectively using a module as a (singleton) object, and if you think it through, you can probably come up with a good class or function to wrap it up in.\n\nObviously just moving all of your globals into class attributes and @classmethods is just giving you globals under a different namespace. But moving them into instance attributes and methods is a different story. That gives you an object you can pass around\u2014and, if necessary, an object you can have 2 of (or maybe even 0 under some circumstances), attach a lock to, serialize, etc.\nIn many types of applications, you're still going to end up with a single instance of something\u2014every Qt GUI app has exactly one MyQApplication, nearly every web server has exactly one MyWebServer, etc. No matter what you call it, that's effectively a singleton or global. And if you want to, you can just move everything into attributes of that god object.\nBut just because you can do so doesn't mean you should. You've still got function parameters, local variables, globals in each module, other (non-megalithic) classes with their own instance attributes, etc., and you should use whatever is appropriate for each value.\nFor example, say your MyWebServer creates a new ClientConnection instance for each new client that connects to you. You could make the connections write MyWebServer.instance.db.execute whenever they want to execute a SQL query\u2026 but you could also just pass self.db to the ClientConnection constructor, and each connection then just does self.db.execute. So, which one is better? Well, if you do it the latter way, it makes your code a lot easier to extend and refactor. If you want to load-balance across 4 databases, you only need to change code in one place (where the MyWebServer initializes each ClientConnection) instead of 100 (every time the ClientConnection accesses the database). If you want to convert your monolithic web app into a WSGI container, you don't have to change any of the ClientConnection code except maybe the constructor. And so on.","Q_Score":7,"Tags":"python,database,singleton","A_Id":15958721,"CreationDate":"2013-04-11T20:53:00.000","Title":"DB-Connections Class as a Singleton in Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have an error no such table: mytable, even though it is defined in models\/tables.py. I use sqlite. Interesting enough, if I go to admin panel -> my app -> database administration then I see a link mytable, however when I click on it then I get no such table: mytable.\nI don't know how to debug such error? \nAny ideas?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1115,"Q_Id":16026776,"Users Score":3,"Answer":"web2py keeps the structure it thinks the table has in a separate file. If someone has manually dropped the table, web2py will still think it exists, but of course you get an error when you try to actually use the table\nLook for the *.mytable.table file in the databases directory","Q_Score":2,"Tags":"python,web2py","A_Id":16026857,"CreationDate":"2013-04-16T00:21:00.000","Title":"web2py. no such table error","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I understand how to save a redis database using bgsave.  However, once my database server restarts, how do I tell if a saved database is present and how do I load it into my application.  I can tolerate a few minutes of lost data, so I don't need to worry about an AOF, but I cannot tolerate the loss of, say, an hour's worth of data.  So doing a bgsave once an hour would work for me.  I just don't see how to reload the data back into the database.\nIf it makes a difference, I am working in Python.","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":1375,"Q_Id":16068644,"Users Score":1,"Answer":"You can stop redis and replace dump.rdb in \/var\/lib\/redis (or whatever file is in the dbfilename variable in your redis.conf). Then start redis again.","Q_Score":2,"Tags":"python,redis,persistence,reload","A_Id":16069631,"CreationDate":"2013-04-17T19:33:00.000","Title":"How to load a redis database after","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a python script that retrieves the newest 5 records from a mysql database and sends email notification to a user containing this information.\nI would like the user to receive only new records and not old ones.\nI can retrieve data from mysql without problems...\nI've tried to store it in text files and compare the files but, of course, the text files containing freshly retrieved data will always have 5 records more than the old one.\nSo I have a logic problem here that, being a newbie, I can't tackle easily.\nUsing lists is also an idea but I am stuck in the same kind of problem.\nThe infamous 5 records can stay the same for one week and then we can have a new record or maybe 3 new records a day.\nIt's quite unpredictable but more or less that should be the behaviour.\nThank you so much for your time and patience.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":85,"Q_Id":16078856,"Users Score":2,"Answer":"Are you assigning a unique incrementing ID to each record?  If you are, you can create a separate table that holds just the ID of the last record fetched, that way you can only retrieve records with IDs greater than this ID.  Each time you fetch, you could update this table with the new latest ID.\nLet me know if I misunderstood your issue, but saving the last fetched ID in the database could be a solution.","Q_Score":0,"Tags":"python","A_Id":16079138,"CreationDate":"2013-04-18T09:11:00.000","Title":"How to check if data has already been previously used","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I need to scrap about 40 random webpages at the same time.These pages vary on each request.\nI have used rpcs in python to fetch the urls and scraped the data using BeautifulSoup. It takes about 25 seconds to scrap all the data and display on the screen. \nTo increase the speed i stored the data in appengine datastore so that each data is scraped only once and can be accessed from there quickly.\nBut the problem is-> as the size of the data increases in the datastore, it is taking too long to fetch the data from the datastore(more than the scraping).\nShould i use memcache Or shift to mysql? Is mysql faster than gae-datastore?\nOr is there any other better way to fetch the data as quickly as possible?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":402,"Q_Id":16098570,"Users Score":0,"Answer":"Based on what I know about your app it would make sense to use memcache. It will be faster, and will automatically take care of things like expiring stale cache entries.","Q_Score":0,"Tags":"python,mysql,google-app-engine,google-cloud-datastore,web-scraping","A_Id":16131039,"CreationDate":"2013-04-19T06:29:00.000","Title":"What is the fastest way to get scraped data from so many web pages?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I've had my python program removed from windows a while ago, and recently downloaded python2.7.4 from the main site, but when I type \"python\" in the Windows PowerShell(x86) prompt from C:, I get the message \"'python' is not recognized as an internal or external command, operable program or batch file.\", and I'd like to find out how to fix this.\nI get the same message when I'm in the actual python27 folder (and the python.exe is indeed there). However, when I type in .\\python, it runs as expected, and my computer can run other .exe's just fine. I'm using Windows 7 Home Premium Service Pack 1 on a Sony VAIO laptop. I'm not very familiar with the inner workings of my computer, so I'm not sure where to look from here.\nMy current path looks like this, with the python folder at the very end:\n%SystemRoot%\\system32\\WindowsPowerShell\\v1.0\\;C:\\Program Files\\Common Files\\Microsoft Shared\\Windows Live;C:\\Program Files (x86)\\Common Files\\Microsoft Shared\\Windows Live;C:\\Windows\\system32;C:\\Windows;C:\\Windows\\System32\\Wbem;C:\\Windows\\System32\\WindowsPowerShell\\v1.0\\;C:\\Program Files\\WIDCOMM\\Bluetooth Software\\;C:\\Program Files\\WIDCOMM\\Bluetooth Software\\syswow64;C:\\Program Files (x86)\\Common Files\\Roxio Shared\\10.0\\DLLShared\\;C:\\Program Files (x86)\\Common Files\\Roxio Shared\\DLLShared\\;C:\\Program Files (x86)\\Common Files\\Adobe\\AGL;C:\\Program Files (x86)\\Windows Live\\Shared;C:\\Program Files\\Java\\jdk1.6.0_23\\bin;c:\\Program Files (x86)\\Microsoft SQL Server\\100\\Tools\\Binn\\;c:\\Program Files\\Microsoft SQL Server\\100\\Tools\\Binn\\;c:\\Program Files\\Microsoft SQL Server\\100\\DTS\\Binn\\;C:\\Program Files (x86)\\MySQL\\MySQL Workbench CE 5.2.42;C:\\Program Files\\MySQL\\MySQL Server 5.5\\bin;C:\\Program Files (x86)\\apache-ant-1.8.4\\bin;C:\\Program Files\\TortoiseSVN\\bin;C:\\Windows\\system32\\WindowsPowerShell\\v1.0\\;C:\\Program Files\\Common Files\\Microsoft Shared\\Windows Live;C:\\Program Files (x86)\\Common Files\\Microsoft Shared\\Windows Live;C:\\Windows\\system32;C:\\Windows;C:\\Windows\\System32\\Wbem;C:\\Windows\\System32\\WindowsPowerShell\\v1.0\\;C:\\Program Files\\WIDCOMM\\Bluetooth Software\\;C:\\Program Files\\WIDCOMM\\Bluetooth Software\\syswow64;C:\\Program Files (x86)\\Common Files\\Roxio Shared\\10.0\\DLLShared\\;C:\\Program Files (x86)\\Common Files\\Roxio Shared\\DLLShared\\;C:\\Program Files (x86)\\Common Files\\Adobe\\AGL;C:\\Program Files (x86)\\Windows Live\\Shared;C:\\Program Files\\Java\\jdk1.6.0_23\\bin;c:\\Program Files (x86)\\Microsoft SQL Server\\100\\Tools\\Binn\\;c:\\Program Files\\Microsoft SQL Server\\100\\Tools\\Binn\\;c:\\Program Files\\Microsoft SQL Server\\100\\DTS\\Binn\\;C:\\Program Files (x86)\\MySQL\\MySQL Workbench CE 5.2.42;C:\\Program Files\\MySQL\\MySQL Server 5.5\\bin;C:\\Program Files (x86)\\apache-ant-1.8.4\\bin;C:\\Program Files\\TortoiseSVN\\bin;C:\\Program Files\\Java\\jdk1.6.0_23\\bin;C:\\Python27","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":1533,"Q_Id":16107658,"Users Score":1,"Answer":"Making the comments an answer for future reference:\nHave a ; at the end of the PATH and logout and log back in.","Q_Score":1,"Tags":"python,windows,powershell,path,exe","A_Id":16108206,"CreationDate":"2013-04-19T15:02:00.000","Title":"Can't open python.exe in Windows Powershell","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":0},{"Question":"My little website has a table of comments and a table of votes. Each user of the website gets to vote once on each comment.\nWhen displaying comments to the user, I will select from the comments table and outerjoin a vote if one exists for the current user.\nIs there a way to make a query where the vote will be attached to the comment through comment.my_vote ?\nThe way I'm doing it now, the query is returning a list for each result - [comment, vote] - and I'm passing that directly to my template. I'd prefer if the vote could be a child object of the comment.","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":149,"Q_Id":16114939,"Users Score":0,"Answer":"In the end I decided that working with the tuple returned by the query wasn't a problem.","Q_Score":0,"Tags":"python,sqlalchemy","A_Id":17140662,"CreationDate":"2013-04-19T23:35:00.000","Title":"SqlAlchemy: Join onto another object","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Is there any SQL injection equivalents, or other vulnerabilities I should be aware of when using NoSQL?\nI'm using Google App Engine DB in Python2.7, and noticed there is not much documentation from Google about security of Datastore.\nAny help would be appreciated!","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":973,"Q_Id":16134927,"Users Score":7,"Answer":"Standard SQL injection techniques rely on the fact that SQL has various statements to either query or modify data. The datastore has no such feature. The GQL (the query language for the datastore) can only be used to query, not modify. Inserts, updates, and deletes are done using a separate method that does not use a text expression. Thus, the datastore is not vulnerable to such injection techniques. In the worst case, an attacker could only change the query to select data you did not intend, but never change it.","Q_Score":2,"Tags":"python,security,google-app-engine,nosql,google-cloud-datastore","A_Id":16140194,"CreationDate":"2013-04-21T18:51:00.000","Title":"NDB\/DB NoSQL Injection Google Datastore","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I am totally fresh and noob as you can be on Twisted. I chose a database proxy as my final project. The idea is, have a mysql as a database. A twisted proxy runs in between client and the database.The proxy makes the methods like UPDATE,SELECT,INSERT through its XMLRPC to the client. And, the methods itself in the proxy hits the database and grabs the data. And, I was thinking of some caching mechanism too on the proxy. So, any heads up on the project? How does chaching work in twisted","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":166,"Q_Id":16155776,"Users Score":0,"Answer":"As you use XML-RPC, you will have to write simple Twisted web application that handles XML-RPC calls.  There are many possibilities for cache: expiring, storing on disk, invalidating, etc etc.  You may start from simple dict for storing queries and find its limitations.","Q_Score":1,"Tags":"python,twisted","A_Id":16171818,"CreationDate":"2013-04-22T20:07:00.000","Title":"Database Proxy using Twisted","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am a rails developer that is learning python and I am doing a project using the pyramid framework. I am used to having some sort of way of rolling back the database changes If I change the models in some sort of way. Is there some sort of database rollback that works similar to the initialize_project_db command?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":139,"Q_Id":16157144,"Users Score":2,"Answer":"initialize_db is not a migration script. It is for bootstrapping your model and that's that. If you want to tie in migrations with upgrade\/rollback support, look at alembic for SQL schema migrations.","Q_Score":0,"Tags":"python,database,pyramid","A_Id":16159421,"CreationDate":"2013-04-22T21:36:00.000","Title":"Is there some sort of way to roll back the initialize_project_db script in pyramid?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have an old SQLite 2 database that I would like to read using Python 3 (on Windows). Unfortunately, it seems that Python's sqlite3 library does not support SQLite 2 databases. Is there any other convenient way to read this type of database in Python 3? Should I perhaps compile an older version of pysqlite? Will such a version be compatible with Python 3?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":445,"Q_Id":16193630,"Users Score":0,"Answer":"As the pysqlite author I am pretty sure nobody has ported pysqlite 1.x to Python 3 yet. The only solution that makes sense effort-wise is the one theomega suggested.\nIf all you need is access the data from Python for importing them elsewhere, but doing the sqlite2 dump\/sqlite3 restore dance is not possible, there is an option, but it is not convenient: Use the builtin ctypes module to access the necessary functions from the SQLite 2 DLL. You would then implement a minimal version of pysqlite yourself that only wraps what you really need.","Q_Score":0,"Tags":"sqlite,python-3.x","A_Id":23542492,"CreationDate":"2013-04-24T13:43:00.000","Title":"Read an SQLite 2 database using Python 3","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"What's the best way to automatically query several dozen MySQL databases with a script on a nightly basis? The script usually returns no results, so I'd ideally have it email or notify me if any are ever returned.\nI've looked into PHP, Ruby and Python for this, but I'm a little stumped as to how best to handle this.","AnswerCount":3,"Available Count":1,"Score":0.0665680765,"is_accepted":false,"ViewCount":307,"Q_Id":16203859,"Users Score":1,"Answer":"I believe the only one can answer this question is you. All 3 examples you gave can do what you need to do with cron to automate the job. But the best script language to be used is the one you are most comfortable to use.","Q_Score":0,"Tags":"php,python,mysql,sql,ruby","A_Id":16203901,"CreationDate":"2013-04-24T23:19:00.000","Title":"What's the best way to automate running MySQL scripts on several databases on a daily basis?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am quite new to heroku and I reached a bump in my dev...\nI am trying to write a server\/client kind of application...on the server side I will have a DB(I installed postgresql for python) and I was hoping I could reach the server, for now, via a python client(for test purposes) and send data\/queries and perform basic tasks on the DB.\nI am using python with Heroku, I manage to install the DB and it seems to be working(i.e i can query, insert, delete, etc...)\nnow all i want is to write a server(in python) that would be my app and would listen on a port and receive messages and then perform whatever tasks it is asked to do...I tought about using sockets for this and have managed to write a basic server\/client locally...however when I deploy the app on heroku i cannot connect to the server and my code is basically worthless\ncan somebody plz advise on the basic framework for this sort of requirements...surely I am not the first guy to want to write a client\/server app...if you could point to a tutorial\/doc i would be much obliged.\nThx","AnswerCount":1,"Available Count":1,"Score":0.537049567,"is_accepted":false,"ViewCount":569,"Q_Id":16244924,"Users Score":3,"Answer":"Heroku is for developing Web (HTTP, HTTPS) applications. You can't deploy code that uses socket to Heroku.\nIf you want to run your app on Heroku, the easier way is to use a web framework (Flask, CherryPy, Django...). They usually also come with useful libraries and abstractions for you to talk to your database.","Q_Score":0,"Tags":"python,heroku","A_Id":16245012,"CreationDate":"2013-04-26T20:44:00.000","Title":"how to write a client\/server app in heroku","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a SQLAlchemy Session object and would like to know whether it is dirty or not. The exact question what I would like to (metaphorically) ask the Session is: \"If at this point I issue a commit() or a rollback(), the effect on the database is the same or not?\".\nThe rationale is this: I want to ask the user wether he wants or not to confirm the changes. But if there are no changes, I would like not to ask anything. Of course I may monitor myself all the operations that I perform on the Session and decide whether there were modifications or not, but because of the structure of my program this would require some quite involved changes. If SQLAlchemy already offered this opportunity, I'd be glad to take advantage of it.\nThanks everybody.","AnswerCount":4,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":12854,"Q_Id":16256777,"Users Score":0,"Answer":"Sessions have a private _is_clean() member which seems to return true if there is nothing to flush to the database. However, the fact that it is private may mean it's not suitable for external use. I'd stop short of personally recommending this, since any mistake here could obviously result in data loss for your users.","Q_Score":18,"Tags":"python,sqlalchemy","A_Id":16257019,"CreationDate":"2013-04-27T20:54:00.000","Title":"How to check whether SQLAlchemy session is dirty or not","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm building a web app in GAE that needs to make use of some simple relationships between the datastore entities. Additionally, I want to do what I can from the outset to make import and exportability easier, and to reduce development time to migrate the application to another platform.\nI can see two possible ways of handling relationships between entities in the datastore:\n\nIncluding the key (or ID) of the related entity as a field in the entity\nOR\nCreating a unique identifier as an application-defined field of an entity to allow other entities to refer to it\n\nThe latter is less integrated with GAE, and requires some kind of mechanism to ensure the unique identifier is in fact unique (which in turn will rely on ancestor queries).\nHowever, the latter may make data portability easier. For example, if entities are created on a local machine they can be uploaded (provided the unique identifier is unique) without problem. By contrast, relying on the GAE defined ID will not work as the ID will not be consistent from the development to the deployed environment.\nThere may be data exportability considerations too that mean an application-defined unique identifier is preferable.\nWhat is the best way of doing this?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":48,"Q_Id":16266979,"Users Score":1,"Answer":"GAE's datastore just doesn't export well to SQL.  There's often situations where data needs to be modeled very differently on GAE to support certain queries, ie many-to-many relationships.  Denormalizing is also the right way to support some queries on GAE's datastore.  Ancestor relationships are something that don't exist in the SQL world.\nIn order to import export data, you'll need to write scripts specific to your data models.\nIf you're planning for compatibility with SQL, use CloudSQL instead of the datastore.\nIn terms of moving data between dev\/production, you've already identified the ways to do it.  There's no real \"easy\" way.","Q_Score":0,"Tags":"google-app-engine,python-2.7,google-cloud-datastore","A_Id":16268751,"CreationDate":"2013-04-28T19:40:00.000","Title":"GAE: planning for exportability and relational databases","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I am using wx.Grid to build spreadsheetlike input interface. I want to lock the size of the cells so the user can not change them. I have successfully disabled the drag-sizing with grid.EnableDragGridSize(False) of the grid but user can still resize the cells by using borders between column and row labels. I am probably missing something in wxGrid documentation.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":426,"Q_Id":16278613,"Users Score":0,"Answer":"I found the solution. To completely lock user ability to resize cells it is needed to use .EnableDragGridSize(False) , .DisableDragColSize() and .DisableDragRowSize()  methods.","Q_Score":1,"Tags":"python,wxpython","A_Id":16279016,"CreationDate":"2013-04-29T12:26:00.000","Title":"wx.Grid cell size lock","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":1,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am able to easily call a python script from php using system(), although there are several options. They all work fine, except they all fail. Through trial and error I have narrowed it down to it failing on \nimport MySQLdb\nI am not too familiar with php, but I am using it in a pinch. I understand while there could be reasons why such a restriction would be in place, but this will be on a local server, used in house, and the information in the mysql db is backed up and not to critical. Meaning such a restriction can be reasonably ignored. \nBut how to allow php to  call a python script that imports mysql? I am on a Linux machine (centOs) if that is relevant.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":322,"Q_Id":16281823,"Users Score":1,"Answer":"The Apache user (www-data in your case) has a somewhat restricted environment. Check where the Python MySQLdb package is installed and edit the Apache user's env (cf Apache manual and your distrib's one about this) so it has a usable Python environment with the right PYTHONPATH etc.","Q_Score":0,"Tags":"php,python,mysql,linux","A_Id":16282538,"CreationDate":"2013-04-29T14:55:00.000","Title":"call python script from php that connects to MySQL","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Let's say I have some free form entries for names, where some are in the format \"Last Name, First Name\" and others are in the format \"First Name Last Name\" (eg \"Bob MacDonald\" and \"MacDonald. Bob\" are both present).\nFrom what I understand, Lucene indexing does not allow for wildcards in the beginning of the sentence, so what would be some ways in which I could find both. This is for neo4j and py2neo, so solutions in either lucene pattern matching, or in python regex matching are welcome.","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":194,"Q_Id":16290237,"Users Score":1,"Answer":"Can you just use OR? \"Hilary Clinton\" OR \"Clinton, Hilary\"?","Q_Score":2,"Tags":"python,regex,neo4j,lucene","A_Id":16290406,"CreationDate":"2013-04-30T00:09:00.000","Title":"Lucene or Python: Select both \"Hilary Clinton\" and \"Clinton, Hilary\" name entries","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":1},{"Question":"There are two possible cases where I am finding MySQL and RDBMS too slow. I need a recommendation for a better alternative in terms of NOSQL.\n1) I have an application that's saving tons of emails for later analysis. Email content is saved in a simple table with a couple of relations to another two tables. Columns are sender, recepient, content, headers, timestamp, etc.\nNow that the records are a close to a million, it's taking longer to search through. Basically there are some pattern searches we are running.\nWhich would be the best free\/open source NOSQL for replacement to store mails so that searching through them would be faster?\n2) Another use case is fundamentally ann asset management library consisting of files. System very simplar to mails. Here we have files of all type of extensions. When the files are created or changed, we are storing meta data of the files in a table. Again data sizes have grown big over time, that searching them is not easy.\nIdeas welcome. Someone suggested Mongo. Is there anything better and faster?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":56,"Q_Id":16304959,"Users Score":1,"Answer":"If search is your primary use case, I'd look into a search solution like ElasticSearch or Solr. Even if some databases support some sort of full text indexing, they're not optimized for this problem.","Q_Score":0,"Tags":"python,nosql","A_Id":16306049,"CreationDate":"2013-04-30T16:42:00.000","Title":"Possible NoSQL cases","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have been running a Python octo.py script to do word counting\/author on a series of files. The script works well -- I tried it on a limited set of data and am getting the correct results.\nBut when I run it on the complete data set it takes forever. I am running on a windows XP laptop with dual core 2.33 GHz and 2 GB RAM.\nI opened up my CPU usage and it shows the processors running at 0%-3% of maximum. \nWhat can I do to force Octo.py to utilize more CPU?\nThanks.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":196,"Q_Id":16376374,"Users Score":0,"Answer":"As your application isn't very CPU intensive, the slow disk turns out to be the bottleneck. Old 5200 RPM laptop hard drives are very slow, which, in addition to fragmentation and low RAM (which impacts disk caching), make reading very slow. This in turns slows down processing and yields low CPU usage. You can try defragmenting, compressing the input files (as they become smaller in disk size, processing speed will increase) or other means of improving IO.","Q_Score":0,"Tags":"python-2.7,multiprocessing,cpu-usage","A_Id":16378262,"CreationDate":"2013-05-04T16:20:00.000","Title":"Octo.py only using between 0% and 3% of my CPUs","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm trying to write a function to do a bulk-save to a mongoDB using pymongo, is there a way of doing it? I've already tried using insert and it works for new records but it fails on duplicates. I need the same functionality that you get using save but with a collection of documents (it replaces an already added document with the same _id instead of failing).\nThanks in advance!","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":311,"Q_Id":16379254,"Users Score":1,"Answer":"you can use bulk insert with option w=0 (ex safe=False), but then you should do a check to see if all documents were actually inserted if this is important for you","Q_Score":3,"Tags":"python,mongodb,pymongo","A_Id":16380066,"CreationDate":"2013-05-04T21:42:00.000","Title":"Is there a pymongo (or another Python library) bulk-save?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am executing update in mysqldb which is changing the values of part of a key and field.  When I execute the query in python it triggers something in the database to cause it to add extra rows. When I execute the same exact query from mysql workbench it performs the update correctly without adding extra rows.  What is the difference between calling from the application and calling from python?\nThanks","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":78,"Q_Id":16420461,"Users Score":0,"Answer":"There was a trigger activating that I did not know about. Thanks for the help","Q_Score":0,"Tags":"python,mysql","A_Id":16943780,"CreationDate":"2013-05-07T13:35:00.000","Title":"MySQLdb for python behaves differently for queries than the mysql workbench browser","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"If I have text that is saved in a Postgresql database is there any way to execute that text as Python code and potentially have it update the same database?","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":162,"Q_Id":16470079,"Users Score":0,"Answer":"let me see if I understand what you are trying to accomplish:\n\nstore ad-hoc user code in a varchar field on a database\nread and execute said code\nallow said code to affect the database in question, say drop table ...\n\nAssuming that I've got it, you could write something that\n\nreads the table holding the code (use pyodbc or something)\nruns an eval on what was pulled from the db - this will let you execute ANY code, including self updating code\n\nare you sure this is what you want to do?","Q_Score":0,"Tags":"python,postgresql","A_Id":16470721,"CreationDate":"2013-05-09T19:57:00.000","Title":"Execute text in Postgresql database as Python code","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I can connect to my local mysql database from python, and I can create, select from, and insert individual rows.\nMy question is: can I directly instruct mysqldb to take an entire dataframe and insert it into an existing table, or do I need to iterate over the rows? \nIn either case, what would the python script look like for a very simple table with ID and two data columns, and a matching dataframe?","AnswerCount":9,"Available Count":1,"Score":-0.022218565,"is_accepted":false,"ViewCount":168445,"Q_Id":16476413,"Users Score":-1,"Answer":"df.to_sql(name = \"owner\", con= db_connection, schema = 'aws', if_exists='replace', index = >True, index_label='id')","Q_Score":60,"Tags":"python,mysql,pandas,mysql-python","A_Id":56185092,"CreationDate":"2013-05-10T06:29:00.000","Title":"How to insert pandas dataframe via mysqldb into database?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I want to do something like \nselect * from table where name like '%name%'\nis there anyway to do this in Hbase ? and if there is a way so how to do that\nps. I use HappyBase to communicate with Hbase","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":364,"Q_Id":16606906,"Users Score":1,"Answer":"HBase provides a scanner interface that allows you to enumerate over a range of keys in an HTable. HappyBase has support for scans and this is documented pretty well in their API.\nSo this would solve your question if you were asking for a \"like 'name%'\" type of query which searches for anything that begins with the prefix 'name'. I am assuming name is the row key in your table, otherwise you would need a secondary index which relates the name field to the row key value of the table or go with the sub-awesome approach of scanning the entire table and doing the matching in Python yourself, depending on your usecase...\nEdit: HappyBase also supports passing a 'filter' string assuming you are using a recent HBase version. You could use the SubStringComparator or RegexStringComparator to fit your needs.","Q_Score":0,"Tags":"python,hbase,thrift","A_Id":16608107,"CreationDate":"2013-05-17T10:33:00.000","Title":"Hbase wildcard support","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have to read and write data's into .xlsx extentsion files using python. And I have to use cell formatting features like merging cells,bold,font size,color etc..So which python module is good to use ?","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":367,"Q_Id":16651124,"Users Score":1,"Answer":"openpyxl is the only library I know of that can read and write xlsx files. It's down side is that when you edit an existing file it doesn't save the original formatting or charts. A problem I'm dealing with right now. If anyone knows a work around please let me know.","Q_Score":0,"Tags":"python","A_Id":24190976,"CreationDate":"2013-05-20T13:55:00.000","Title":"Which module has more option to read and write xlsx extension files using Python?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"In MongoDB if we provide a coordinate and a distance, using $near operator will find us the documents nearby within the provided distance, and sorted by distance to the given point. \nDoes Redis provide similar functions?","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":798,"Q_Id":16761134,"Users Score":1,"Answer":"Noelkd was right. There is no inbuilt function in Redis.\nI found that the simplest solution is to use geohash to store the hashed lat\/lng as keys.\nGeohash is able to store locations nearby with similar structure, e.g.\nA hash of a certain location is ebc8ycq, then the nearby locations can be queried with the wildcard ebc8yc* in Redis.","Q_Score":2,"Tags":"python,mongodb,redis,geospatial","A_Id":16886089,"CreationDate":"2013-05-26T16:13:00.000","Title":"How to find geographically near documents in Redis, like $near in MongoDB?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am running my Django site on appengine. In the datastore, there is an entity kind \/ table X which is only updated once every 24 hours. \nX has around 15K entries and each entry is of form (\"unique string of length <20\", integer).\nIn some context, a user request involves fetching an average of 200 entries from X, which is quite costly if done individually.\nWhat is an efficient way I can adopt in this situation?\nHere are some ways I thought about, but have some doubts in them due to inexperience\n\nUsing the Batch query supported by db.get() where a list of keys may be passed as argument and the get() will try to fetch them all in one walk. This will reduce the time quite significantly, but still there will be noticeable overhead and cost. Also, I am using Django models and have no idea about how to relate these two.\nManually copying the whole database into memory (like storing it in a map) after each update job which occurs every 24 hour. This will work really well and also save me lots of datastore reads but I have other doubts. Will it remain persistent across instances? What other factors do I need to be aware of which might interfere? This or something like this seems perfect for my situation.\n\nThe above are just what I could come up with in first thought. There must be ways I am unaware\/missing.\nThanks.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":53,"Q_Id":16773961,"Users Score":1,"Answer":"Your total amout of data is very small and looks like a dict. Why not save it (this object) as a single entry in the database or the blobstore and you can cache this entry.","Q_Score":1,"Tags":"python,django,google-app-engine","A_Id":16775062,"CreationDate":"2013-05-27T13:08:00.000","Title":"A way to optimize reading from a datastore which updates once a day","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I need to represent instances of Python \"Long integer\" in MySQL. I wonder what the most appropriate SQL data type I should use.\nThe Python documentation (v2.7) says (for numbers.Integral):\n\nLong integers\n\nThese represent numbers in an unlimited range, subject to available (virtual) memory only. For the purpose of shift and mask operations, a binary representation is assumed, and negative numbers are represented in a variant of 2\u2019s complement which gives the illusion of an infinite string of sign bits extending to the left.\n\n\nMy read of the MySQL documentation suggests that BIGINT is limited to 64 bits. The DECIMAL type seems to be limited to 65 digits. I can, of course, use BLOB.\nThe application needs to support very large amounts of data, but I don't know yet how big these long integers might get, nor how many of them I'm likely to see.\nI'd like to preserve the spirit of the Python long integer definition, which suggests BLOB. I'd also like to avoid re-inventing the wheel, and so I am appealing to the stackoverflow hive-mind.\nSuggestions?","AnswerCount":4,"Available Count":1,"Score":0.1488850336,"is_accepted":false,"ViewCount":1333,"Q_Id":16867823,"Users Score":3,"Answer":"Yes if you really need unlimited precision then you'll have to use a blob because even strigns are limited. \nBut really I can almost guarantee that you'll be fine with a NUMERIC\/DECIMAL data type. 65 digits means that you can represent numbers in the range (-10^65, 10^65). How large is this? To give you some idea: The number of atoms in the whole universe is estimated to be about 10^80. If you only need positive numbers you can further increase the range by a factor of 2 by subtracting 10^65 -1 beforehand.","Q_Score":2,"Tags":"python,mysql,mysql-python","A_Id":16867914,"CreationDate":"2013-06-01T00:26:00.000","Title":"What are the options for storing Python long integers in MySQL?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Can someone advise on what database is better for storing textual information such as part of speech sequences, dependencies, sentences used in NLP project written in python. Now this information is stored in files and they need to be parsed every time in order to extract the mentioned blocks which are used as an input for next processing stage. \nOptions considered  - MongoDB, Cassandra and MySQL. Are NoSQL databases better in this type of application.\nThanks.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":2075,"Q_Id":16872221,"Users Score":6,"Answer":"This really depends on what exactly you are storing and which operations you will perform on this data.\nSQL vs. NoSQL is a very fundamental decision and no one can give you a good advice here. If your data fits relational model well, then, SQL (PostgreSQL or MySQL) is your choice. If your data is more like documents, use MongoDB.\nThat said, just recently I made a search engine. We had to store indexed pages (raw text), the same text but tokenized and some additional metadata. MongoDB performed really well.","Q_Score":0,"Tags":"python,mysql,mongodb,nlp,bigdata","A_Id":16873052,"CreationDate":"2013-06-01T11:31:00.000","Title":"Database for NLP project","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"So I have my Django app running and I just added South. I performed some migrations which worked fine locally, but I am seeing some database errors on my Heroku version. I'd like to view the current schema for my database both locally and on Heroku so I can compare and see exactly what is different. Is there an easy way to do this from the command line, or a better way to debug this?","AnswerCount":3,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":3348,"Q_Id":16942317,"Users Score":3,"Answer":"From the command line you should be able to do heroku pg:psql to connect directly via PSQL to your database and from in there \\dt will show you your tables and \\d <tablename> will show you your table schema.","Q_Score":2,"Tags":"python,django,postgresql,heroku,django-south","A_Id":16942831,"CreationDate":"2013-06-05T14:15:00.000","Title":"How to View My Postgres DB Schema from Command Line","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am executing an update query using MySQLdb and python 2.7. Is it possible to know which rows affected by retrieving all their ids?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":67,"Q_Id":16961438,"Users Score":2,"Answer":"You can get the number of affected rows by using cursor.rowcount. The information which rows are affected is not available since the mysql api does not support this.","Q_Score":1,"Tags":"python,mysql-python","A_Id":16961869,"CreationDate":"2013-06-06T11:53:00.000","Title":"Python, mySQLdb: Is it possible to retrieve updated keys, after update?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"MySQL is installed at \/usr\/local\/mysql\nIn site.cfg the path for mysql_config is \/usr\/local\/mysql\/bin\/mysql_config\nbut when i try to build in the terminal im getting this error:\nhammads-imac-2:MySQL-python-1.2.4b4 syedhammad$ sudo python setup.py build\nrunning build\nrunning build_py\ncopying MySQLdb\/release.py -> build\/lib.macosx-10.8-intel-2.7\/MySQLdb\nrunning build_ext\nbuilding '_mysql' extension\nclang -fno-strict-aliasing -fno-common -dynamic -g -Os -pipe -fno-common -fno-strict-aliasing -fwrapv -mno-fused-madd -DENABLE_DTRACE -DMACOSX -DNDEBUG -Wall -Wstrict-prototypes -Wshorten-64-to-32 -DNDEBUG -g -Os -Wall -Wstrict-prototypes -DENABLE_DTRACE -pipe -Dversion_info=(1,2,4,'beta',4) -D_version_=1.2.4b4 -I\/usr\/local\/mysql\/include -I\/System\/Library\/Frameworks\/Python.framework\/Versions\/2.7\/include\/python2.7 -c _mysql.c -o build\/temp.macosx-10.8-intel-2.7\/_mysql.o -Wno-null-conversion -Os -g -fno-strict-aliasing -arch x86_64\nunable to execute clang: No such file or directory\nerror: command 'clang' failed with exit status 1\nHelp Please","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":141,"Q_Id":16985604,"Users Score":2,"Answer":"You probably need Xcode's Command Line Tools.\nDownload the lastest version of Xcode, then go to \"Preferences\", select \"Download\" tab, then install Command Line Tools.","Q_Score":1,"Tags":"python,mysql,macos","A_Id":16985650,"CreationDate":"2013-06-07T13:41:00.000","Title":"Configuring MySQL with python on OS X lion","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":0},{"Question":"We are currently developing an application that makes heavy use of PostgreSQL. For the most part we access the database using SQLAlchemy, and this works very well. For testing the relevant objects can be either mocked, or used without database access. But there are some parts of the system that run non-standard queries. These subsystems have to create temporary tables insert a huge number of rows and then merge data back into the main table.\nCurrently there are some SQL statements in these subsystems, but this makes the relevant classes tightly coupled with the database, which in turn makes things harder to unit-test.\nBasically my question is, is there any design pattern for solving this problem? The only thing that I could come up with is to put these SQL statements into a separate class and just pass an instance to the other class. This way I can mock the query-class for unit-tests, but it still feels a bit clumsy. Is there a better way to do this?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":161,"Q_Id":16999676,"Users Score":0,"Answer":"So after playing around with it some more I now have a solution that is halfway decent. I split the class in question up into three separate classes:\n\nA class that provides access to the required data;\nA context manager that supports the temporary table stuff;\nAnd the old class with all the logic (sans the database stuff);\n\nWhen I instantiate my logic class I supply it with an instance of the aforementioned classes. It works ok, abstraction is slightly leaky (especially the context manager), but I can at least unit test the logic properly now.","Q_Score":3,"Tags":"python,sql,design-patterns","A_Id":17017714,"CreationDate":"2013-06-08T12:48:00.000","Title":"Design Pattern for complicated queries","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I've been writing a Python web app (in Flask) for a while now, and I don't believe I fully grasp how database access should work across multiple request\/response cycles. Prior to Python my web programming experience was in PHP (several years worth) and I'm afraid that my PHP experience is misleading some of my Python work.\nIn PHP, each new request creates a brand new DB connection, because nothing is shared across requests. The more requests you have, the more connections you need to support. However, in a Python web app, where there is shared state across requests, DB connections can persist.\nSo I need to manage those connections, and ensure that I close them. Also, I need to have some kind of connection pool, because if I have just one connection shared across all requests, then requests could block waiting on DB access, if I don't have enough connections available.\nIs this a correct understanding? Or have I identified the differences well? In a Python web app, do I need to have a DB connection pool that shares its connections across many requests? And the number of connections in the pool will depend on my application's request load?\nI'm using Psycopg2.","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":351,"Q_Id":17012349,"Users Score":4,"Answer":"Have you looked in to SQLAlchemy at all?  It takes care of a lot of the dirty details - it maintains a pool of connections, and reuses\/closes them as necessary.","Q_Score":4,"Tags":"python,psycopg2","A_Id":17012369,"CreationDate":"2013-06-09T17:36:00.000","Title":"Database access strategy for a Python web app","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Need to get one row from a table, and delete the same row.\nIt does not matter which row it is. The function should be generic, so the column names are unknown, and there are no identifiers. (Rows as a whole can be assumed to be unique.)\nThe resulting function would be like a pop() function for a stack, except that the order of elements does not matter.\nPossible solutions:\n\nDelete into a temporary table.\n(Can this be done in pysqlite?)\nGet * with 1 as limit, and the Delete * with 1 as limit.\n(Is this safe if there is just one user?)\nGet one row, then delete with a WHERE clause that compares the whole row.\n(Can this be done in pysqlite?)\n\nSuggestions?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":64,"Q_Id":17127306,"Users Score":1,"Answer":"Well. every table in a sqlite has a rowid. Select one and delete it?","Q_Score":0,"Tags":"python,database,pysqlite","A_Id":17382716,"CreationDate":"2013-06-15T19:47:00.000","Title":"row_pop() function in pysqlite?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have the user registration form made in django.\nI want to know the city from which the user is registering.\nIs there any way that i get the IP address of the user and then somehow get the city for that IP. using some API or something","AnswerCount":4,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":163,"Q_Id":17159576,"Users Score":0,"Answer":"Not in any reliable way, or at least not in Django. The problem is that user IPs are usually dynamic, hence the address is changing every couple of days. Also some ISPs soon will start to use a single IP for big blocks of users (forgot what this is called) since they are running out of IPv4 IP addresses... In other words, all users from that ISP within a whole state or even country will have a single IP address.\nSo using the IP is not reliable. You could probably figure out the country or region of the user with reasonable accuracy however my recommendation is not to use the IP for anything except logging and permission purposes (e.g. blocking a spam IP).\nIf you want user locations, you can however use HTML5 location API which will have a much better shot of getting more accurate location since it can utilize other methods such us using a GPS sensor in a phone.","Q_Score":0,"Tags":"python,django,ip","A_Id":17159679,"CreationDate":"2013-06-18T02:12:00.000","Title":"Is there any simple way to store the user location while registering in database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am trying to put the items, scraped by my spider, in a mysql db via a mysql pipeline. Everything is working but i see some odd behaviour. I see that the filling of the database is not in the same order as the website itself. There is like a random order. Probably of the dictionary like list of the items scraped i guess.\nMy questions are:\n\nhow can i get the same order as the items of the website itself.\nhow can i reverse this order of question 1.\n\nSo items on website:\n\nA\nB\nC\nD\nE\n\nadding order in my sql:\n\nE\nD\nC\nB\nA","AnswerCount":3,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":201,"Q_Id":17213515,"Users Score":0,"Answer":"Items in a database are have not a special order if you don't impose it. So you should add a timestamp to your table in the database, keep it up-to-date (mysql has a special flag to mark a field as auto-now) and use ORDER BY in your queries.","Q_Score":2,"Tags":"python,scrapy","A_Id":17213740,"CreationDate":"2013-06-20T12:20:00.000","Title":"Scrapy reversed item ordening for preparing in db","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am trying to put the items, scraped by my spider, in a mysql db via a mysql pipeline. Everything is working but i see some odd behaviour. I see that the filling of the database is not in the same order as the website itself. There is like a random order. Probably of the dictionary like list of the items scraped i guess.\nMy questions are:\n\nhow can i get the same order as the items of the website itself.\nhow can i reverse this order of question 1.\n\nSo items on website:\n\nA\nB\nC\nD\nE\n\nadding order in my sql:\n\nE\nD\nC\nB\nA","AnswerCount":3,"Available Count":2,"Score":0.0665680765,"is_accepted":false,"ViewCount":201,"Q_Id":17213515,"Users Score":1,"Answer":"It's hard to say without the actual code, but in theory..\nScrapy is completely async, you cannot know the order of items that will be parsed and processed through the pipeline.\nBut, you can control the behavior by \"marking\" each item with priority key. Add a field priority to your Item class, in the parse_item method of your spider set the priority based on the position on a web page, then in your pipeline you can either write this priority field to the database (in order to have an ability to sort later), or gather all items in a class-wide list, and in close_spider method sort the list and bulk insert it into the database.\nHope that helps.","Q_Score":2,"Tags":"python,scrapy","A_Id":17221923,"CreationDate":"2013-06-20T12:20:00.000","Title":"Scrapy reversed item ordening for preparing in db","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Lets take SQLAlchemy as an example.\nWhy should I use the Flask SQLAlchemy extension instead of the normal SQLAlchemy module?\nWhat is the difference between those two?\nIsn't is perfectly possible to just use the normal module in your Flask app?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":99,"Q_Id":17222824,"Users Score":4,"Answer":"The extensions exist to extend the functionality of Flask, and reduce the amount of code you need to write for common usage patterns, like integrating your application with SQLAlchemy in the case of flask-sqlalchemy, or login handling with flask-login. Basically just clean, reusable ways to do common things with a web application. \nBut I see your point with flask-sqlalchemy, its not really that much of a code saver to use it, but it does give you the scoped-session automatically, which you need in a web environment with SQLAlchemy. \nOther extensions like flask-login really do save you a lot of boilerplate code.","Q_Score":1,"Tags":"python,sqlalchemy,flask,flask-sqlalchemy","A_Id":17223377,"CreationDate":"2013-06-20T20:06:00.000","Title":"Why do Flask Extensions exist?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I would like to save data to sqlite3 databases which will be fetched from the remote system by FTP. Each database would be given a name that is an encoding of the time and date with a resolution of 1 hour (i.e. a new database every hour).\nFrom the Python 3 sqlite3 library, would any problems be encountered if two threads try to create the database at the same time? Or are there protections against this?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":426,"Q_Id":17274626,"Users Score":0,"Answer":"This will work just fine.\nWhen two threads are trying to create the same file, one will fail to do so, but it will continue to try to lock the file.","Q_Score":1,"Tags":"python,python-3.x,sqlite","A_Id":17275138,"CreationDate":"2013-06-24T11:41:00.000","Title":"Can sqlite3 databases be created in a thread-safe way?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a flask application which use three types of databases - MySQL, Mongo and Redis. Now, if it had been simple MySQL I could have use SQLAlchemy or something on that line for database modelling. Now, in the current scenario where I am using many different types of database in a single application, I think I will have to create custom models.\nCan you please suggest what are the best practices to do that? Or any tutorial indicating the same?","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":79,"Q_Id":17276970,"Users Score":0,"Answer":"It's not an efficient model, but this would work:\nYou can write three different APIs (RESTful pattern is a good idea). Each will be an independent Flask application, listening on a different port (likely over localhost, not the public IP interface).\nA forth Flask application is your main application that external clients can access. The view functions in the main application will issue API calls to the other three APIs to obtain data as they see fit.\nYou could optimize and merge one of the three database APIs into the main application, leaving only two (likely the two less used) to be implemented as APIs.","Q_Score":3,"Tags":"python,database,flask,flask-sqlalchemy","A_Id":17289054,"CreationDate":"2013-06-24T13:41:00.000","Title":"How to create models if I am using various types of database simultaneously?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm looking for the best approach for inserting a row into a spreadsheet using openpyxl.\nEffectively, I have a spreadsheet (Excel 2007) which has a header row, followed by (at most) a few thousand rows of data. I'm looking to insert the row as the first row of actual data, so after the header. My understanding is that the append function is suitable for adding content to the end of the file.\nReading the documentation for both openpyxl and xlrd (and xlwt), I can't find any clear cut ways of doing this, beyond looping through the content manually and inserting into a new sheet (after inserting the required row). \nGiven my so far limited experience with Python, I'm trying to understand if this is indeed the best option to take (the most pythonic!), and if so could someone provide an explicit example. Specifically can I read and write rows with openpyxl or do I have to access cells? Additionally can I (over)write the same file(name)?","AnswerCount":12,"Available Count":1,"Score":-0.0166651236,"is_accepted":false,"ViewCount":90928,"Q_Id":17299364,"Users Score":-1,"Answer":"Unfortunately there isn't really a better way to do in that read in the file, and use a library like xlwt to write out a new excel file (with your new row inserted at the top).  Excel doesn't work like a database that you can read and and append to.  You unfortunately just have to read in the information and manipulate in memory and write out to what is essentially a new file.","Q_Score":19,"Tags":"python,excel,xlrd,xlwt,openpyxl","A_Id":17305443,"CreationDate":"2013-06-25T14:00:00.000","Title":"Insert row into Excel spreadsheet using openpyxl in Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"So I have a password protected XLS file which i've forgotten the password for...I'm aware it's a date within a certain range so i'm trying to write a brute forcer to try various dates of the year. However, I can't find how to use python\/java to enter the password for the file. It's protected such that I can't open the xls file unless I have it and it has some very important information on there (so important I kept the password in a safe place that I now can't find lol).\nI'm using fedora. Are there any possible suggestions? Thankyou.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":268,"Q_Id":17344335,"Users Score":0,"Answer":"If you search there are a number of applications that you can download that will unblock the workbook.","Q_Score":0,"Tags":"java,python,excel,passwords,xls","A_Id":17344366,"CreationDate":"2013-06-27T13:20:00.000","Title":"How to enter password in XLS files with python?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"In my python\/django based web application I want to export some (not all!) data from the app's SQLite database to a new SQLite database file and, in a web request, return that second SQLite file as a downloadable file. \nIn other words: The user visits some view and, internally, a new SQLite DB file is created, populated with data and then returned. \nNow, although I know about the :memory: magic for creating an SQLite DB in memory, I don't know how to return that in-memory database as a downloadable file in the web request. Could you give me some hints on how I could reach that? I would like to avoid writing stuff to the disc during the request.","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":169,"Q_Id":17382053,"Users Score":1,"Answer":"I'm not sure you can get at the contents of a :memory: database to treat it as a file; a quick look through the SQLite documentation suggests that its API doesn't expose the :memory: database to you as a binary string, or a memory-mapped file, or any other way you could access it as a series of bytes. The only way to access a :memory: database is through the SQLite API.\nWhat I would do in your shoes is to set up your server to have a directory mounted with ramfs, then create an SQLite3 database as a \"file\" in that directory. When you're done populating the database, return that \"file\", then delete it. This will be the simplest solution by far: you'll avoid having to write anything to disk and you'll gain the same speed benefits as using a :memory: database, but your code will be much easier to write.","Q_Score":0,"Tags":"python,django,sqlite","A_Id":17382483,"CreationDate":"2013-06-29T16:01:00.000","Title":"Python: Create and return an SQLite DB as a web request result","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"suppose there was  a database table with one column, and it's a PK. To make things more specific this is a django project and the database is in mysql. \nIf I needed an additional column with all unique values, should I create a new UniqueField with unique integers, or just write a hash-like function to convert the existing PK's for each existing row (model instance) into a new unique variable. The current PK is a varchar\/ & string. \nWith creating a new column it consumes more memory but I think writing a new function and converting fields frequently has disadvantages also. Any ideas?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":50,"Q_Id":17393291,"Users Score":1,"Answer":"Having a string-valued PK should not be a problem in any modern database system. A PK is automatically indexed, so when you perform a look-up with a condition like table1.pk = 'long-string-key', it won't be a string comparison but an index look-up. So it's ok to have string-valued PK, regardless of the length of the key values.\nIn any case, if you need an additional column with all unique values, then I think you should just add a new column.","Q_Score":0,"Tags":"python,mysql,django","A_Id":17393525,"CreationDate":"2013-06-30T18:03:00.000","Title":"Database design, adding an extra column versus converting existing column with a function","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"i am working on developing a Django application with Cassandra as the back end database. while Django supports ORM feature for SQL, i wonder if there is any thing similar for Cassandra.\nwhat would be the best approach to load the schema into the Cassandra server and perform CRUD operations.\nP.S. I am complete beginner to Cassandra.","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":410,"Q_Id":17403346,"Users Score":3,"Answer":"There's an external backend for Cassandra, but it has some issues with the authentication middleware, which doesn't handle users correctly in the admin. If you use a non-relational database, you lose a lot of goodies that django has. You could try using Postgres' nosql extension for the parts of your data that you want to store in a nosql'y way, and the regular Postgres' tables for the rest.","Q_Score":1,"Tags":"python,django,orm,cassandra","A_Id":17403637,"CreationDate":"2013-07-01T11:25:00.000","Title":"Cassandra-Django python application approach","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a state column in my table which has the following possible values: discharged, in process and None.\nCan I fetch all the records in the following order: in process, discharged followed by None?","AnswerCount":1,"Available Count":1,"Score":0.3799489623,"is_accepted":false,"ViewCount":1384,"Q_Id":17408276,"Users Score":2,"Answer":"If you've declared that column as an enum type (as you should for cases such as these where the values are drawn from a small, fixed set of strings), then using ORDER BY on that column will order results according to the order in which the values of the enum were declared.  So the datatype for that column should be ENUM('in process', 'discharged', 'None'); that will cause ORDER BY to sort in the order you desire.  Specifically, each value in an enum is assigned a numerical index and that index is used when comparing enum values for sorting purposes.  (The exact way in which you should declare an enum will vary according to which type of backend you're using.)","Q_Score":1,"Tags":"python,sql,sqlalchemy","A_Id":17408674,"CreationDate":"2013-07-01T15:33:00.000","Title":"Sqlalchemy order_by custom ordering?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm trying to work with oursql in python 3.2, and it's really not going so well.  \nFacts:\nI downloaded oursql binary and ran the installer.\nI have MySQL 5.1 installed.\nI separately downloaded the libmysql dll and placed it in the System32 directory.\nI downloaded cython for version 3.1 because there wasn't one for 2.7 or 3.2.\nI have python versions 2.7, 3.1, and 3.2 installed.\nI rebooted.\nI now still get the ImportError: DLL load failed: The specified module could not be found. error when running import oursql from the Python 3.1 shell.\nAny ideas?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":196,"Q_Id":17420396,"Users Score":0,"Answer":"OK, I moved libmysql.dll to the same directory as python.exe, instead of in the DLL's folder, and it seems like it works.","Q_Score":0,"Tags":"python,mysql,python-3.x,oursql","A_Id":17420506,"CreationDate":"2013-07-02T08:00:00.000","Title":"Error on installing oursql for Python 3.1","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am using python 2.7 and Mysql. I am using multi-threading and giving connections to different threads by using PooledDB . I give db connections to different threads by\npool.dedicated_connection().Now if a thread takes a connection from pool and dies due to some reason with closing it(ie. without returning it to the pool).What happens to this connection.\nIf it lives forever how to return it to the pool??","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":178,"Q_Id":17423384,"Users Score":2,"Answer":"No, it does not.  You have to tell the server on the other side that the connection is closed, because it can't tell the difference between \"going away\" and \"I haven't sent my next query yet\" without an explicit signal from you.\nThe connection can time out, of course, but it won't be closed or cleaned up without instructions from you.","Q_Score":0,"Tags":"python,mysql,multithreading,python-2.7","A_Id":17423440,"CreationDate":"2013-07-02T10:37:00.000","Title":"Does database connection return to pool if a thread holding it dies?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have an existing MySQL database that I set up on PMA, it has FKs that references columns that are not primary keys. Now I am trying to move the database to Django and am having trouble because when I try to set up d Foreign Keys in django it automatically references the Primary Key of the table that I am attempting to reference so the data doesnt match because column A and column B do not contain the same info. Is there a way to tell django what column to reference?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":62,"Q_Id":17491720,"Users Score":0,"Answer":"You can use the to_field attribute of a ForeignKey.\nDjango should detect this automatically if you use .\/manage.py inspectdb, though.","Q_Score":0,"Tags":"python,mysql,django,phpmyadmin","A_Id":17491830,"CreationDate":"2013-07-05T14:54:00.000","Title":"Moving database from PMA to Django","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"What is the easiest way to export the results of a SQL Server query to a CSV file? I have read that the pymssql module is the preferred way, and I'm guessing I'll need csv as well.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1521,"Q_Id":17495581,"Users Score":0,"Answer":"Do you need to do this programmatically or is this a one-off export?\nIf the latter, the easiest way by far is to use the SSMS export wizard. In SSMS, select the database, right-click and select Tasks->Export Data.","Q_Score":0,"Tags":"python,sql-server,csv,pymssql","A_Id":17495797,"CreationDate":"2013-07-05T19:20:00.000","Title":"Export SQL Server Query Results to CSV using pymssql","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"im using openpyxl to edit an excel file that contains some formulas in certain cells. Now when i populate the cells from a text file, im expecting the formula to work and give me my desired output. But what i observe is that the formulas get removed and the cells are left blank.","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":1400,"Q_Id":17522521,"Users Score":1,"Answer":"I had the same problem when saving the file with openpyxl: formulas removed.\nBut I pointed out that some intermediate formulas were still there.\nAfter some tests, it appears that, in my case, all formulas which are displaying blank result (nothing) are cleaned when the save occured, unlike the formulas with an output in the cell, which are preserved.\nex :\n=IF((SUM(P3:P5))=0;\"\";(SUM(Q3:Q5))\/(SUM(P3:P5))) => can be removed when saving because of the blank result\nex :\n=IF((SUM(P3:P5))=0;\"?\";(SUM(Q3:Q5))\/(SUM(P3:P5))) => preserved when saving\nfor my example I'm using openpyxl-2.0.3 on Windows. Open and save function calls are :\nself._book = load_workbook(\"myfile.xlsx\", data_only=False)\nself._book.save(\"myfile.xlsx\")","Q_Score":0,"Tags":"python-2.7,openpyxl","A_Id":24183661,"CreationDate":"2013-07-08T08:55:00.000","Title":"Openpyxl: Formulas getting removed when saving file","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have two tables  with a common field I want to find all the the\n  items(user_id's) which present in first table but not in second.\n\nTable1(user_id,...)\nTable2(userid,...)\nuser_id in and userid in frist and second table are the same.","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":225,"Q_Id":17541225,"Users Score":1,"Answer":"session.query(Table1.user_id).outerjoin(Table2).filter(Table2.user_id == None)","Q_Score":1,"Tags":"python,sqlalchemy","A_Id":17542024,"CreationDate":"2013-07-09T06:15:00.000","Title":"find missing value between to tables in sqlalchemy","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I want to build Python 3.3.2 from scratch on my SLE 11 (OpenSUSE).\nDuring the compilation of Python I got the message that the modules _bz2, _sqlite and _ssl have not been compiled.\nI looked for solutions with various search engines. It is often said that you have to install the -dev packages with your package management system, but I have no root access.\nI downloaded the source packages of the missing libs, but I have no idea how to tell Python to use these libs. Can somebody help me?","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":444,"Q_Id":17546628,"Users Score":0,"Answer":"I don't use that distro, but Linux Mint (it's based on Ubuntu).\nIn my case before the compilation of Python 3.3.2 I've installed the necessary -dev libraries:\n $ sudo apt-get install libssl-dev\n $ sudo apt-get install libbz2-dev\n ...\nThen I've compiled and installed Python and those imports work fine.\nHope you find it useful\nLe\u00f3n","Q_Score":1,"Tags":"python-3.x,sqlite,ssl,compilation,non-admin","A_Id":17979292,"CreationDate":"2013-07-09T11:05:00.000","Title":"How to build python 3.3.2 with _bz2, _sqlite and _ssl from source","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I've got a fairly simple Python program as outlined below:\nIt has 2 threads plus the main thread. One of the threads collects some data and puts it on a Queue. \nThe second thread takes stuff off the queue and logs it. Right now it's just printing out the stuff from the queue, but I'm working on adding it to a local MySQL database.\nThis is a process that needs to run for a long time (at least a few months). \nHow should I deal with the database connection? Create it in main, then pass it to the logging thread, or create it directly in the logging thread? And how do I handle unexpected situations with the DB connection (interrupted, MySQL server crashes, etc) in a robust manner?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":84,"Q_Id":17578630,"Users Score":0,"Answer":"How should I deal with the database connection? Create it in main,\n  then pass it to the logging thread, or create it directly in the\n  logging thread?\n\nI would perhaps configure your logging component with the class that creates the connection and let your logging component request it. This is called dependency injection, and makes life easier in terms of testing e.g. you can mock this out later. \nIf the logging component created the connections itself, then testing the logging component in a standalone fashion would be difficult. By injecting a component that handles these, you can make a mock that returns dummies upon request, or one that provides connection pooling (and so on).\nHow you handle database issues robustly depends upon what you want to happen. Firstly make your database interactions transactional (and consequently atomic). Now, do you want your logger component to bring your system to a halt whilst it retries a write. Do you want it to buffer writes up and try out-of-band (i.e. on another thread) ? Is it mission critical to write this or can you afford to lose data (e.g. abandon a bad write). I've not provided any specific answers here, since there are so many options depending upon your requirements. The above details a few possible options.","Q_Score":1,"Tags":"python,mysql,database,multithreading","A_Id":17578684,"CreationDate":"2013-07-10T18:49:00.000","Title":"Architechture of multi-threaded program using database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"How do you install pyodbc package on a Linux (RedHat server RHEL) onto a Zope\/Plone bundled Python path instead of in the global Python path? \nyum install pyodbc and python setup.py install, all put pyodbc in the sys python path.\nI read articles about putting pyodbc in python2.4\/site-packages\/\nI tried that, but it didn't work for my Plone external method, which still complains about no module named pyodbc.","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":265,"Q_Id":17662330,"Users Score":1,"Answer":"Add the package to the eggs section in buildout and then re-run buildout.\nThere might be additional server requirements to install pyodbc.","Q_Score":1,"Tags":"python,plone,zope,pyodbc","A_Id":17794367,"CreationDate":"2013-07-15T19:32:00.000","Title":"pyodbc Installation Issue on Plone Python Path","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a client-server interface realized using the module requests as client and tornado as server. I use this to query a database, where some dataitems may not be avaiable. For example the author in a query might not be there or the book-title. \nIs there a recommended way to let my client know, what was missing? Like an HTTP 404: Author missing or something like that?","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":237,"Q_Id":17678927,"Users Score":1,"Answer":"Since HTTP 404 responses can have a response body, I would put the detailed error message in the body itself. You can, for example, send the string Author Not Found in the response body. You could also send the response string in the format that your API already uses, e.g. XML, JSON, etc., so that every response from the server has the same basic shape.\nWhether using code 404 with a X Not Found message depends on the structure of your API. If it is a RESTful API, where each URL corresponds to a resource, then 404 is a good choice if the resource itself is the thing missing. If a requested data field is missing, but the requested resource exists, I don't think 404 would be a good choice.","Q_Score":0,"Tags":"python,http,tornado,http-status-codes","A_Id":17681053,"CreationDate":"2013-07-16T14:13:00.000","Title":"Can I have more semantic meaning in an http 404 error?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"my teammate and i wrote a Python script running on the same server where the database is. Now we want to know if the performance changes when we write the same code as a stored procedure in our postgres database. What is the difference or its the same??\nThanks.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":507,"Q_Id":17682444,"Users Score":2,"Answer":"There can be differences - PostgreSQL stored procedures (functions) uses inprocess execution, so there are no any interprocess communication - so if you process more data, then stored procedures (in same language) can be faster than server side application. But speedup depends on size of processed data.","Q_Score":2,"Tags":"python,database,performance,postgresql,plpgsql","A_Id":17686435,"CreationDate":"2013-07-16T16:48:00.000","Title":"What is the difference between using a python script running on server and a stored procedure?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have been using the datastore with ndb for a multiplayer app. This appears to be using a lot of reads\/writes and will undoubtedly go over quota and cost a substantial amount.\nI was thinking of changing all the game data to be stored only in memcache. I understand that data stored here can be lost at any time, but as the data will only be needed for, at most, 10 minutes and as it's just a game, that wouldn't be too bad.\nAm I right to move to solely use memcache, or is there a better method, and is memcache essentially 'free' short term data storage?","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":341,"Q_Id":17702165,"Users Score":1,"Answer":"As a commenter on another answer noted, there are now two memcache offerings: shared and dedicated.  Shared is the original service, and is still free.  Dedicated is in preview, and presently costs $.12\/GB hour.\nDedicated memcache allows you to have a certain amount of space set aside.  However, it's important to understand that you can still experience partial or complete flushes at any time with dedicated memcache, due to things like machine reboots.  Because of this, it's not a suitable replacement for the datastore. \nHowever, it is true that you can greatly reduce your datastore usage with judicious use of memcache.  Using it as a write-through cache, for example, can greatly reduce your datastore reads (albeit not the writes).\nHope this helps.","Q_Score":3,"Tags":"python,google-app-engine,memcached,google-cloud-datastore,app-engine-ndb","A_Id":17816617,"CreationDate":"2013-07-17T14:13:00.000","Title":"Datastore vs Memcache for high request rate game","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I have some very complex XSD schemas to work with. By complex I mean that each of these XSD would correspont to about 20 classes \/ tables in a database, with each table having approximately 40 fields. And I have 18 different XSD like that to program.\nWhat I'm trying to achieve is: Get a XML file defined by the XSD and save all the data in a PostgreSQL database using SQLAlchemy. Basically I need a CRUD application that will persist a XML file in the database following the model of the XSD schema, and also be able to retrieve an object from the database and create a XML file.\nI want to avoid having to manually create the python classes, the sqlalchemy table definitions, the CRUD code. This would be a monumental job, subject to a lot of small mistakes, given the complexity of the XSD files.\nI can generate python classes from XSD in many ways like GenerateDS, PyXB, etc... I need to save those objects in the database. I'm open to any suggestions, even if the suggestion is conceptually different that what I'm describing.\nThank you very much","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":2179,"Q_Id":17750340,"Users Score":1,"Answer":"Not sure if there is a way directly, but you could indirectly go from XSD to a SQL Server DB, and then import the DB from SQLAlchemy","Q_Score":2,"Tags":"python,xml,postgresql,xsd,sqlalchemy","A_Id":34734878,"CreationDate":"2013-07-19T15:50:00.000","Title":"Generate Python Class and SQLAlchemy code from XSD to store XML on Postgres","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am working with Python, fetching huge amounts of data from MS SQL Server Database and processing those for making graphs.\nThe real issue is that I wanted to know whether it would be a good idea to repeatedly perform queries to filter the data (using pyodbc for SQL queries) using attributes like WHERE and SELECT DISTINCT etc. in queries \nOR \nTo fetch the data and use the list comprehensions, map and filter functionalities of python to filter the data in my code itself.\nIf I choose the former, there would be around 1k queries performed reducing significant load on my python code, otherwise if I choose the latter, I would be querying once and add on a bunch of functions to go through all the records I have fetched, more or less the same number of times(1k). \nThe thing is python is not purely functional, (if it was, I wouldnt be asking and would have finished and tested my work hundreds of times by now). \nWhich one would you people recommend? \nFor reference I am using Python 2.7. It would be highly appreciated if you could provide sources of information too. Also, Space is not an issue for fetching the whole data.\nThanks","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":470,"Q_Id":17757031,"Users Score":0,"Answer":"If you have bandwidth to burn, and prefer Python to SQL, go ahead and do one big query and filter in Python.\nOtherwise, you're probably better off with multiple queries.\nSorry, no references here.  ^_^","Q_Score":1,"Tags":"python,sql-server-2008,map,bigdata","A_Id":17757423,"CreationDate":"2013-07-19T23:33:00.000","Title":"SQL query or Programmatic Filter for Big Data?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a load of data in CSV format.  I need to be able to index this data based on a single text field (the primary key), so I'm thinking of entering it into a database.  I'm familiar with sqlite from previous projects, so I've decided to use that engine.\nAfter some experimentation, I realized that that storing a hundred million records in one table won't work well: the indexing step slows to a crawl pretty quickly.  I could come up with two solutions to this problem:\n\npartition the data into several tables\npartition the data into several databases\n\nI went with the second solution (it yields several large files instead of one huge file).  My partition method is to look at the first two characters of the primary key: each partition has approximately 2 million records, and there are approximately 50 partitions.\nI'm doing this in Python with the sqlite3 module.  I keep 50 open database connections and open cursors for the entire duration of the process.  For each row, I look at the first two characters of the primary key, fetch the right cursor via dictionary lookup, and perform a single insert statement (via calling execute on the cursor).\nUnfortunately, the insert speed still decreases to an unbearable level after a while (approx. 10 million total processed records).  What can I do to get around this?  Is there a better way to do what I'm doing?","AnswerCount":2,"Available Count":1,"Score":0.4621171573,"is_accepted":false,"ViewCount":1881,"Q_Id":17826391,"Users Score":5,"Answer":"Wrap all insert commands into a single transaction.\nUse prepared statements.\nCreate the index only after inserting all the data (i.e., don't declare a primary key).","Q_Score":1,"Tags":"python,database,sqlite","A_Id":17826461,"CreationDate":"2013-07-24T06:07:00.000","Title":"What's the best way to insert over a hundred million rows into a SQLite database?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Psycopg is the most popular PostgreSQL adapter for the Python programming language.\nThe name Psycopg does not make sense to me.\nI understand the last pg means Postgres, but what about Psyco?","AnswerCount":1,"Available Count":1,"Score":1.0,"is_accepted":false,"ViewCount":2412,"Q_Id":17869761,"Users Score":11,"Answer":"I've always thought of it as psycho-Postgres.","Q_Score":21,"Tags":"python,postgresql","A_Id":17869993,"CreationDate":"2013-07-25T22:19:00.000","Title":"Where does the name `Psycopg` come from?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am trying to copy the entire \/contentstore\/ folder on a bucket to a timestamped version. Basically \/contenstore\/ would be copied to \/contentstore\/20130729\/.\nMy entire script uses s3s3mirror first to clone my production S3 bucket to a backup. I then want to rename the backup to a timestamped copy so that I can keep multiple versions of the same. \nI have a working version of this using s3cmd but it seems to take an abnormally long time. The s3s3mirror part between the two buckets is done within minutes, possibly because it is a refresh on existing folder. But even in the case of a clean s3s3mirror (no existing contentstore on backup) it take around 20 minutes.\nOn the other hand copying the conentstore to a timestamped copy on the backup bucket takes over an hour and 10 minutes.\nAm I doing something incorrectly? Should the copy of data on the same bucket take longer than a full clone between two different buckets?\nAny ideas would be appreciated.\nP.S: The command I am running is s3cmd --recursive cp backupBucket\/contentStore\/ backupBucket\/20130729\/","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":995,"Q_Id":17931579,"Users Score":0,"Answer":"Since your source path contains your destination path, you may actually be copying things more than once -- first into the destination path, and then again when that destination path matches your source prefix. This would also explain why copying to a different bucket is faster than within the same bucket.\nIf you're using s3s3mirror, use the -v option and you'll see exactly what's getting copied. Does it show the same key being copied multiple times?","Q_Score":1,"Tags":"python,amazon-web-services,amazon-s3,boto,s3cmd","A_Id":20389005,"CreationDate":"2013-07-29T18:32:00.000","Title":"Copying files in the same Amazon S3 bucket","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have an html file on network which updates almost every minute with new rows in a table. At any point, the file contains close to 15000 rows I want to create a MySQL table with all data in the table, and then some more that I compute from the available data.\nThe said HTML table contains, say rows from the last 3 days. I want to store all of them in my mysql table, and update the table every hour or so (can this be done via a cron?)\nFor connecting to the DB, I'm using MySQLdb which works fine. However, I'm not sure what are the best practices to do so. I can scrape the data using bs4, connect to table using MySQLdb. But how should I update the table? What logic should I use to scrape the page that uses the least resources?\nI am not fetching any results, just scraping and writing.\nAny pointers, please?","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":509,"Q_Id":17939824,"Users Score":0,"Answer":"My Suggestion is instead of updating values row by row try to use Bulk Insert in temporary table and then move the data into an actual table based on some timing key. If you have key column that will be good for reading the recent rows as you added.","Q_Score":1,"Tags":"python,mysql,beautifulsoup,mysql-python","A_Id":17940205,"CreationDate":"2013-07-30T06:33:00.000","Title":"Update a MySQL table from an HTML table with thousands of rows","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Title question says it all. I was trying to figure out how I could go about integrating the database created by sqlite3 and communicate with it through Python from my website. \nIf any further information is required about the development environment, please let me know.","AnswerCount":3,"Available Count":1,"Score":0.0665680765,"is_accepted":false,"ViewCount":1713,"Q_Id":17953552,"Users Score":1,"Answer":"It looks like your needs has changed and you are going into direction where static web site is not sufficient any more.\nFirstly, I would pick appropriate Python framework for your needs. if static website was sufficient until recently Django can be perfect for you.\nNext I would suggest describing your DB schema for ORM used in chosen framework. I see no point in querying your DB using SQL until you would have a specific reason.\nAnd finally, I would start using static content of your website as templates, replacing places where dynamic data is required. Django internal template language can be easily used that way. If not, Jinja2 also could be good.\nMy advise is base on many assumptions, as your question is quite open and undefined.\nAnyway, I think it would be the best way to start transition period from static to dynamic.","Q_Score":5,"Tags":"python,sqlite,static-site","A_Id":18099967,"CreationDate":"2013-07-30T17:29:00.000","Title":"I have a static website built using HTML, CSS and Javascript. How do I integrate this with a SQLite3 database accessed with the Python API?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm currently running into an issue in integrating ElasticSearch and MongoDB. Essentially I need to convert a number of Mongo Documents into searchable documents matching my ElasticSearch query. That part is luckily trivial and taken care of. My problem though is that I need this to be fast. Faster than network time, I would really like to be able to index around 100 docs\/second, which simply isn't possible with network calls to Mongo.\nI was able to speed this up a lot by using ElasticSearch's bulk indexing, but that's only half of the problem. Is there any way to either bundle reads or cache a collection (a manageable part of a collection, as this collection is larger than I would like to keep in memory) to help speed this up? I was unable to really find any documentation about this, so if you can point me towards relevant documentation I consider that a perfectly acceptable answer. \nI would prefer a solution that uses Pymongo, but I would be more than happy to use something that directly talks to MongoDB over requests or something similar. Any thoughts on how to alleviate this?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":195,"Q_Id":17955275,"Users Score":0,"Answer":"pymongo is thread safe, so you can run multiple queries in parallel. (I assume that you can somehow partition your document space.)\nFeed the results to a local Queue if processing the result needs to happen in a single thread.","Q_Score":1,"Tags":"python,performance,mongodb,pymongo","A_Id":24357799,"CreationDate":"2013-07-30T19:04:00.000","Title":"Bundling reads or caching collections with Pymongo","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm working on an app that employs the python sqlite3 module. My database makes use of the implicit ROWID column provided by sqlite3. I expected that the ROWIDs be reordered after I delete some rows and vacuum the database. Because in the sqlite3 official document:\n\nThe VACUUM command may change the ROWIDs of entries in any tables that\n  do not have an explicit INTEGER PRIMARY KEY.\n\nMy pysqlite version is 2.6.0 and the sqlite version is 3.5.9. Can anybody tell me why it is not working? Anything I should take care when using vacuum?\nP.S. I have a standalone sqlite installed whose version is 3.3.6. I tested the vacuum statement in it, and the ROWIDs got updated. So could the culprit be the version? Or could it be a bug of pysqlite? \nThanks in advance for any ideas or suggestions!","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":134,"Q_Id":17987732,"Users Score":0,"Answer":"This behaviour is version dependent.\nIf you want a guaranteed reordering, you have to copy all records into a new table yourself.\n(This works with both implicit and explicit ROWIDs.)","Q_Score":1,"Tags":"python,sqlite,pysqlite","A_Id":17988741,"CreationDate":"2013-08-01T07:30:00.000","Title":"Why are not ROWIDs updated after VACUUM when using python sqlite3 module?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am stuck with this issue: I had some migration problems and I tried many times and on the way, I deleted migrations and tried again and even deleted one table in db. there is no data in db, so I don't have to fear. But now if I try syncdb it is not creating the table I deleted manually. \nHonestly, I get really stuck every time with this such kind of migration issues. \nWhat should I do to create the tables again?","AnswerCount":4,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":824,"Q_Id":17995963,"Users Score":0,"Answer":"are you using south? \nIf you are, there is a migration history database that exists.\nMake sure to delete the row mentionnaing the migration you want to run again.","Q_Score":0,"Tags":"python,django,django-south","A_Id":17996086,"CreationDate":"2013-08-01T13:51:00.000","Title":"syncdb is not creating tables again?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am stuck with this issue: I had some migration problems and I tried many times and on the way, I deleted migrations and tried again and even deleted one table in db. there is no data in db, so I don't have to fear. But now if I try syncdb it is not creating the table I deleted manually. \nHonestly, I get really stuck every time with this such kind of migration issues. \nWhat should I do to create the tables again?","AnswerCount":4,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":824,"Q_Id":17995963,"Users Score":0,"Answer":"Try renaming the migration file and running python manage.py syncdb.","Q_Score":0,"Tags":"python,django,django-south","A_Id":29407625,"CreationDate":"2013-08-01T13:51:00.000","Title":"syncdb is not creating tables again?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm designing a g+ application for a big international brand. the entities I need to create are pretty much in form of a graph, hence a lot of many-to-many relations (arcs) connecting nodes that can be traversed in both directions. I'm reading all the readable docs online, but I haven't found anything so far specific to ndb design best practices and guidelines. unfortunately I am under nda, and cannot reveal details of the app, but it can match almost one to one the context of scientific conferences with proceedings, authors, papers and topics.\nbelow the list of entities envisioned so far (with context shifted to match the topics mentioned):\n\norganization (e.g. acm)\nconference (e.g. acm multimedia)\nconference issue (e.g. acm multimedia 13)\nconference track (e.g. nosql, machine learning, computer vision, etc.)\nauthor (e.g. myself)\npaper (e.g. \"designing graph like db for ndb\")\n\nas you can see, I can visit and traverse the graph through any direction (or facet, from a frontend point of view): \n\nauthor with co-authors\nauthor to conference tracks\nconference tracks to papers\n...\n\nand so on, you fill the list.\nI want to make it straight and solid because it will launch with a lot of p.r. and will need to scale consistently overtime, both in content and number of users. I would like to code it from scratch hence designing my own models, restful api to read\/write this data, avoiding non-rel django and keeping the presentation layer to a minimum template mechanism. I need to check with the company where I work, but we might be able to release part of the code with a decent open source license (ideally, a restful service for ndb models).\nif anyone could point me towards the right direction, that would be awesome.\nthanks!\nthomas\n[edit: corrected typo related to many-to-many relations]","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":478,"Q_Id":18017150,"Users Score":1,"Answer":"There's two ways to implement one-to-many relationships in App Engine.\n\nInside entity A, store a list of keys to entities B1, B2, B3.  In th old DB, you'd use a ListProperty of db.Key.  In ndb you'd use a KeyProperty with repeated = True.\nInside entity B1, B2, B3, store a KeyProperty to entity A.\n\nIf you use 1:\n\nWhen you have Entity A, you can fetch B1, B2, B3 by id.  This can be potentially more consistent than the results of a query.  \nIt could be slightly less expensive since you save 1 read operation over a query (assuming you don't count the cost of fetching entity A).  Writing B instances is slightly cheaper since  it's one less index to update.\nYou're limited in the number of B instances you can store by the maximum entity size and number of indexed properties on A.  This makes sense for things like conference tracks since there's generally a limited number of tracks that doesn't go into the thousands.\nIf you need to sort the order of B1, B2, B3 arbitrarily, it's easier to store them in order in a list than to sort them using some sorted indexed property.\n\nIf you use 2:\n\nYou only need entity A's Key in order to query for B1, B2, B3.  You don't actually need to fetch entity A to get the list.\nYou can have pretty much unlimited # of B entities.","Q_Score":1,"Tags":"python,google-app-engine,app-engine-ndb,graph-databases","A_Id":18035092,"CreationDate":"2013-08-02T12:42:00.000","Title":"best practice for graph-like entities on appengine ndb","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I have read somewhere that you can store python objects (more specifically dictionaries) as binaries in MongoDB by using BSON. However right now I cannot find any any documentation related to this.\nWould anyone know how exactly this can be done?","AnswerCount":3,"Available Count":1,"Score":0.3215127375,"is_accepted":false,"ViewCount":23835,"Q_Id":18089598,"Users Score":5,"Answer":"Assuming you are not specifically interested in mongoDB, you are probably not looking for BSON. BSON is just a different serialization format compared to JSON, designed for more speed and space efficiency. On the other hand, pickle does more of a direct encoding of python objects.\nHowever, do your speed tests before you adopt pickle to ensure it is better for your use case.","Q_Score":18,"Tags":"python,mongodb,pymongo,bson","A_Id":18089722,"CreationDate":"2013-08-06T20:14:00.000","Title":"Is there a way to store python objects directly in mongoDB without serializing them","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have several S3 buckets containing a total of 40 TB of data across 761 million objects.  I undertook a project to copy these objects to EBS storage.  To my knowledge, all buckets were created in us-east-1.  I know for certain that all of the EC2 instances used for the export to EBS were within us-east-1.\nThe problem is that the AWS bill for last month included a pretty hefty charge for inter-regional data transfer.  I'd like to know how this is possible?\nThe transfer used a pretty simple Python script with Boto to connect to S3 and download the contents of each object.  I suspect that the fact that the bucket names were composed of uppercase letters might have been a contributing factor (I had to specify OrdinaryCallingFormat()), but I don't know this for sure.","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":878,"Q_Id":18113426,"Users Score":0,"Answer":"The problem ended up being an internal billing error at AWS and was not related to either S3 or Boto.","Q_Score":0,"Tags":"python,amazon-web-services,amazon-s3,boto","A_Id":18366790,"CreationDate":"2013-08-07T20:42:00.000","Title":"Boto randomly connecting to different regions for S3 transfers","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":1,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am trying to run the following db2 command through the python pyodbc module \nIBM DB2 Command : \"DB2 export to C:\\file.ixf of ixf select * from emp_hc\" \ni am successfully connected to the DSN using the pyodbc module in python and works fine for select statement \nbut when i try to execute the following command from the Python IDLE 3.3.2\ncursor.execute(\" export to ? of ixf select * from emp_hc\",r\"C:\\file.ixf\") \npyodbc.ProgrammingError: ('42601', '[42601] [IBM][CLI Driver][DB2\/LINUXX8664] SQL0104N  An unexpected token \"db2 export to ? of\" was found following \"BEGIN-OF-STATEMENT\".  Expected tokens may include:  \"\".  SQLSTATE=42601\\r\\n (-104) (SQLExecDirectW)')\nor \ncursor.execute(\" export to C:\\file.ixf of ixf select * from emp_hc\")\nTraceback (most recent call last):\n  File \"\", line 1, in \n    cursor.execute(\"export to C:\\myfile.ixf of ixf select * from emp_hc\")\npyodbc.ProgrammingError: ('42601', '[42601] [IBM][CLI Driver][DB2\/LINUXX8664] SQL0007N  The character \"\\\" following \"export to C:\" is not valid.  SQLSTATE=42601\\r\\n (-7) (SQLExecDirectW)')\nam i doing something wrong ? any help will be greatly appreciated.","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":1372,"Q_Id":18134390,"Users Score":1,"Answer":"db2 export is a command run in the shell, not through SQL via odbc.\nIt's possible to write database query results to a file with python and pyodbc, but db2 export will almost certainly be faster and effortlessly handle file formatting if you need it for import.","Q_Score":0,"Tags":"python,sql,db2,pyodbc","A_Id":18135069,"CreationDate":"2013-08-08T19:24:00.000","Title":"sql import export command error using pyodbc module python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"when connecting to mysql database in Django ,I get the error.\n\nI'm sure mysql server is running.\n\/var\/run\/mysqld\/mysqld.sock doesn't exist.\nWhen I run $ find \/ -name *.sock -type s, I only get \/tmp\/mysql.sock and some other irrelevant output.\nI added socket = \/tmp\/mysql.sock to \/etc\/my.cnf. And then restared mysql, exited django shell, and connected to mysql database. I still got the same error.\n\nI searched a lot, but I still don't know how to do.\nAny help is greate. Thanks in advance.\nWell, I just tried some ways. And it works.\nI did as follows.\n\nAdd socket = \/tmp\/mysql.sock .Restart the mysql server.\nln -s \/tmp\/mysql.sock \/var\/lib\/mysqld\/mysqld.sock\n\nI met an another problem today. I can't login to mysql.\nI'm newbie to mysql. So I guess mysql server and client use the same socket to communicate.\nI add socket = \/var\/mysqld\/mysqld.sock to [mysqld] [client] block in my.cnf  and it wokrs.","AnswerCount":5,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":101165,"Q_Id":18150858,"Users Score":0,"Answer":"I faced this problem when connecting MySQL with Django when using Docker.\nTry 'PORT':'0.0.0.0'.\nDo not use 'PORT': 'db'. This will not work if you tried to run your app outside Docker.","Q_Score":26,"Tags":"python,mysql,django,mysql.sock","A_Id":66405102,"CreationDate":"2013-08-09T15:55:00.000","Title":"OperationalError: (2002, \"Can't connect to local MySQL server through socket '\/var\/run\/mysqld\/mysqld.sock' (2)\")","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"when connecting to mysql database in Django ,I get the error.\n\nI'm sure mysql server is running.\n\/var\/run\/mysqld\/mysqld.sock doesn't exist.\nWhen I run $ find \/ -name *.sock -type s, I only get \/tmp\/mysql.sock and some other irrelevant output.\nI added socket = \/tmp\/mysql.sock to \/etc\/my.cnf. And then restared mysql, exited django shell, and connected to mysql database. I still got the same error.\n\nI searched a lot, but I still don't know how to do.\nAny help is greate. Thanks in advance.\nWell, I just tried some ways. And it works.\nI did as follows.\n\nAdd socket = \/tmp\/mysql.sock .Restart the mysql server.\nln -s \/tmp\/mysql.sock \/var\/lib\/mysqld\/mysqld.sock\n\nI met an another problem today. I can't login to mysql.\nI'm newbie to mysql. So I guess mysql server and client use the same socket to communicate.\nI add socket = \/var\/mysqld\/mysqld.sock to [mysqld] [client] block in my.cnf  and it wokrs.","AnswerCount":5,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":101165,"Q_Id":18150858,"Users Score":0,"Answer":"in flask, you may use that\napp=Flask(__name__)\napp.config[\"MYSQL_HOST\"]=\"127.0.0.1 \napp.config[\"MYSQL_USER\"]=\"root\"...","Q_Score":26,"Tags":"python,mysql,django,mysql.sock","A_Id":56762083,"CreationDate":"2013-08-09T15:55:00.000","Title":"OperationalError: (2002, \"Can't connect to local MySQL server through socket '\/var\/run\/mysqld\/mysqld.sock' (2)\")","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"when connecting to mysql database in Django ,I get the error.\n\nI'm sure mysql server is running.\n\/var\/run\/mysqld\/mysqld.sock doesn't exist.\nWhen I run $ find \/ -name *.sock -type s, I only get \/tmp\/mysql.sock and some other irrelevant output.\nI added socket = \/tmp\/mysql.sock to \/etc\/my.cnf. And then restared mysql, exited django shell, and connected to mysql database. I still got the same error.\n\nI searched a lot, but I still don't know how to do.\nAny help is greate. Thanks in advance.\nWell, I just tried some ways. And it works.\nI did as follows.\n\nAdd socket = \/tmp\/mysql.sock .Restart the mysql server.\nln -s \/tmp\/mysql.sock \/var\/lib\/mysqld\/mysqld.sock\n\nI met an another problem today. I can't login to mysql.\nI'm newbie to mysql. So I guess mysql server and client use the same socket to communicate.\nI add socket = \/var\/mysqld\/mysqld.sock to [mysqld] [client] block in my.cnf  and it wokrs.","AnswerCount":5,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":101165,"Q_Id":18150858,"Users Score":0,"Answer":"You need to change your HOST from 'localhost' to '127.0.0.1' and check your django app :)","Q_Score":26,"Tags":"python,mysql,django,mysql.sock","A_Id":72389079,"CreationDate":"2013-08-09T15:55:00.000","Title":"OperationalError: (2002, \"Can't connect to local MySQL server through socket '\/var\/run\/mysqld\/mysqld.sock' (2)\")","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I used mysqldb to connect to a database in my localhost.\nIt works, but if I add data to a table in the database when the program is running, it shows that it has been added, but when I check the table from localhost, it hasn't been updated.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":30,"Q_Id":18245510,"Users Score":0,"Answer":"if your table uses innodb engine, you should call connection.commit() on every cursor.execute().","Q_Score":0,"Tags":"python,mysql,database-connection,mysql-python","A_Id":18245522,"CreationDate":"2013-08-15T02:41:00.000","Title":"musqldb-python doesnt really update the original database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm trying to understand which of the following is a better option:\n\nData calculation using Python from the output of a MySQL query.\nPerform the calculations in the query itself.\n\nFor example, the query returns 20 rows with 10 columns.\nIn Python, I compute the difference or division of some of the columns.\nIs it a better thing to do this in the query or in Python ?","AnswerCount":2,"Available Count":2,"Score":0.0996679946,"is_accepted":false,"ViewCount":2805,"Q_Id":18270585,"Users Score":1,"Answer":"It is probably a matter of taste but...\n... to give you an exact opposite answer as the one by Alma Do Mundo, for (not so) simple calculation made on the SELECT ... clause, I generally push toward using the DB \"as a calculator\".\nCalculations (in the SELECT ... clause) are performed as the last step while executing the query. Only the relevant data are used at this point. All the \"big job\" has already been done (processing JOIN, where clauses, aggregates, sort).\nAt this point, the extra load of performing some arithmetic operations on the data is really small. And that will reduce the network traffic between your application and the DB server.\nIt is probably a matter of taste thought...","Q_Score":2,"Tags":"python,mysql,query-performance,sql-tuning,query-tuning","A_Id":18270751,"CreationDate":"2013-08-16T09:53:00.000","Title":"Data Calculations MySQL vs Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm trying to understand which of the following is a better option:\n\nData calculation using Python from the output of a MySQL query.\nPerform the calculations in the query itself.\n\nFor example, the query returns 20 rows with 10 columns.\nIn Python, I compute the difference or division of some of the columns.\nIs it a better thing to do this in the query or in Python ?","AnswerCount":2,"Available Count":2,"Score":0.0996679946,"is_accepted":false,"ViewCount":2805,"Q_Id":18270585,"Users Score":1,"Answer":"If you are doing basic arithmetic operation on calculations in a row, then do it in SQL.  This gives you the option of encapsulating the results in a view or stored procedure.  In many databases, it also gives the possibility of parallel execution of the statements (although performance is not an issue with so few rows of data).\nIf you are doing operations between rows in MySQL (such as getting the max for the column), then the balance is more even.  Most databases support simple functions to these calculations, but MySQL does not.  The added complexity to the query gives some weight to doing these calculations on the client-side.\nIn my opinion, the most important consideration is maintainability of the code.  By using a database, you are necessary incorporating business rules in the database itself (what entities are related to which other entities, for instance).  A major problem with maintaining code is having business logic spread through various systems.  I much prefer to have an approach where such logic is as condensed as possible, creating very clear APIs between different layers.\nFor such an approach, \"read\" access into the database would be through views.  The logic that you are talking about would go into the views and be available to any user of the database -- ensuring consistency across different functions using the database.  \"write\" access would be through stored procedures, ensuring that business rules are checked consistently and that operations are logged appropriately.","Q_Score":2,"Tags":"python,mysql,query-performance,sql-tuning,query-tuning","A_Id":18271329,"CreationDate":"2013-08-16T09:53:00.000","Title":"Data Calculations MySQL vs Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm trying to use python for manipulating some data in MySQL DB.\nDB is on a remote PC. And I will use another PC with Python to connect to the DB.\nWhen I searched how to install MySQLdb module to Python, they all said MySQL need to be installed on the local PC.\nIs it right? Or I don't need to install MySQL on the local PC?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":323,"Q_Id":18288616,"Users Score":1,"Answer":"You just need it if you want to compile the Python MySQL bindings from source. If you already have the binary version of the python library then the answer is no, you don't need it.","Q_Score":0,"Tags":"python,mysql","A_Id":18288628,"CreationDate":"2013-08-17T12:07:00.000","Title":"Do I need MySQL installed on my local PC to use MySQLdb for Python to connect MySQL server remotely?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm using the python packages xlrd and xlwt to read and write from excel spreadsheets using python. I can't figure out how to write the code to solve my problem though.\nSo my data consists of a column of state abbreviations and a column of numbers, 1 through 7. There are about 200-300 entries per state, and i want to figure out how many ones, twos, threes, and so on exist for each state. I'm struggling with what method I'd use to figure this out. \nnormally i would post the code i already have but i don't even know where to begin.","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":247,"Q_Id":18413606,"Users Score":0,"Answer":"Prepare a dictionary to store the results.\nGet the numbers of line with data you have using xlrd, then iterate over each of them. \nFor each state code, if it's not in the dict, you create it also as a dict.\nThen you check if the entry you read on the second column exists within the state key on your results dict.\n4.1 If it does not, you'll create it also as a dict, and add the number found on the second column as a key to this dict, with a value of one.\n4.2 If it does, just increment the value for that key (+1).\n\nOnce it has finished looping, your result dict will have the count for each individual entry on each individual state.","Q_Score":0,"Tags":"python,excel,xlrd,xlwt","A_Id":18413675,"CreationDate":"2013-08-24T00:09:00.000","Title":"Python Programming approach - data manipulation in excel","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I've been working with Python MySQLdb. With InnoDB tables autocommit is turned off in default and that was what I needed. But since I'm now working with MyISAM tables, the docs for MySQL say \n\nMyISAM tables effectively always operate in autocommit = 1 mode\n\nSince I'm running up to a few hundreds of queries a second, does committing with every single query slow down the performance of my script? Because I used to commit once every 1000 queries before, now I can't do that with MyISAM. If it slows it down, what can I try?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":440,"Q_Id":18462528,"Users Score":0,"Answer":"MyISAM has no transactions, so you can't not to \"autocommit\" using MyISAM.\nYour runtime change may be also caused by the fact you moved from innoDB to MyISAM.\nThe best approach for DB runtime issues in general is benchmarking, benchmarking and benchmarking.","Q_Score":1,"Tags":"python,mysql,commit","A_Id":18463239,"CreationDate":"2013-08-27T10:06:00.000","Title":"does autocommit slow down performance in python?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have an application which receives data over a TCP connection and writes it to a postgres database. I then use a django web front end to provide a gui to this data. Since django provides useful database access methods my TCP receiver also uses the django models to write to the database.\nMy issue is that I need to use a forked TCP server. Forking results in both child and parent processes sharing handles. I've read that Django does not support forking and indeed the shared database connections are causing problems e.g. these exceptions:\nDatabaseError: SSL error: decryption failed or bad record mac\nInterfaceError: connection already closed\nWhat is the best solution to make the forked TCP server work?\n\nCan I ensure the forked process uses its own database connection?\nShould I be looking at other modules for writing to the postgres database?","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":941,"Q_Id":18492467,"Users Score":0,"Answer":"The libpq driver, which is what the psycopg2 driver usually used by django is built on, does not support forking an active connection. I'm not sure if there might be another driver does not, but I would assume not - the protocol does not support multiplexing multiple sessions on the same connection.\nThe proper solution to your problem is to make sure each forked processes uses its own database connection. The easiest way is usually to wait to open the connection until after the fork.","Q_Score":2,"Tags":"python,django,postgresql","A_Id":18496589,"CreationDate":"2013-08-28T15:42:00.000","Title":"Forking Django DB connections","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I have an application which receives data over a TCP connection and writes it to a postgres database. I then use a django web front end to provide a gui to this data. Since django provides useful database access methods my TCP receiver also uses the django models to write to the database.\nMy issue is that I need to use a forked TCP server. Forking results in both child and parent processes sharing handles. I've read that Django does not support forking and indeed the shared database connections are causing problems e.g. these exceptions:\nDatabaseError: SSL error: decryption failed or bad record mac\nInterfaceError: connection already closed\nWhat is the best solution to make the forked TCP server work?\n\nCan I ensure the forked process uses its own database connection?\nShould I be looking at other modules for writing to the postgres database?","AnswerCount":2,"Available Count":2,"Score":0.0996679946,"is_accepted":false,"ViewCount":941,"Q_Id":18492467,"Users Score":1,"Answer":"So one solution I found is to create a new thread to spawn from. Django opens a new connection per thread so spawning from a new thread ensures you pass a new connection to the new process. \nIn retrospect I wish I'd used psycopg2 directly from the beginning rather than Django. Django is great for the web front end but not so great for a standalone app where all I'm using it for is the model layer. Using psycopg2 would have given be greater control over when to close and open connections. Not just because of the forking issue but also I found Django doesn't keep persistent postgres connections - something we should have better control of in 1.6 when released and should for my specific app give a huge performance gain. Also, in this type of application I found Django intentionally leaks - something that can be fixed with DEBUG set to False. Then again, I've written the app now :)","Q_Score":2,"Tags":"python,django,postgresql","A_Id":18531322,"CreationDate":"2013-08-28T15:42:00.000","Title":"Forking Django DB connections","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"The company I work for is starting development of a Django business application that will use MySQL as the database engine. I'm looking for a way to keep from having database credentials stored in a plain-text config file.\nI'm coming from a Windows\/IIS background where a vhost can impersonate an existing Windows\/AD user, and then use those credentials to authenticate with MS SQL Server.\nAs an example: If the Django application is running with apache2+mod_python on an Ubuntu server, would it be sane to add a \"www-data\" user to MySQL and then let MySQL verify the credentials using its PAM module?\nHopefully some of that makes sense. Thanks in advance!","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":691,"Q_Id":18495773,"Users Score":1,"Answer":"MySQL controls access to tables from its own list of users, so it's better to create MySQL users with permissions.  You might want to create roles instead of users so you don't have as many to manage: an Admin, a read\/write role, a read-only role, etc.\nA Django application always runs as the web server user.  You could change that to \"impersonate\" an Ubuntu user, but what if that user is deleted?  Leave it as \"www-data\" and manage the database role that way.","Q_Score":3,"Tags":"python,mysql,django","A_Id":18496083,"CreationDate":"2013-08-28T18:39:00.000","Title":"Can a Django application authenticate with MySQL using its linux user?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have an excel file whose extension is .xls but his type is Tab Space separated Text.\nWhen I try to open the file by MS Excel it tells me that the extension is fake. And So I have to confirm that I trust the file and so I can read it then.\nBut my real problem is that when I try to read my file by the xlrd library it gives me this message :\nxlrd.biffh.XLRDError: Unsupported format, or corrupt file: Expected BOF record;\nAnd so to resolve this problem, I go to Save as in MS Excel and I change the type manually to .xls.\nBut my boss insist that I have to do this by code. I have 3 choices : Shell script under Linux, .bat file under Windows or Python.\nSo, how can I change the type of the excel file from Tab space separated Text to xls file by Shell script (command line), .bat or Python?","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":399,"Q_Id":18570143,"Users Score":1,"Answer":"mv file.{xls,csv}\nIt's a csv file, stop treating it as an excel file and things will work a lot better. :)  There are nice csv manipulation tools available in most languages. Do you really need the excel library?","Q_Score":0,"Tags":"python,linux,excel,shell,xlrd","A_Id":18574653,"CreationDate":"2013-09-02T09:46:00.000","Title":"How to change automatically the type of the excel file from Tab space separated Text to xls file?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I need to do the following\n\nDelete many entities from a database, also those entities have a file associated with them saved into the file system, which are accessed also by the web server (images!).\n\nThe problem: File deletion might fail, I have all the files in a folder for the main entity (its actually a 1-N relation, being each one of the N the file owners). If I try to delete a file when the web server is accessing them, I will get an exception and the process will go in half, some images deleted, and some doesnt, leaving the system inconsistent.\nIs there a way to to do something similar to a transaction but in the file system (either delete all files or don't delete any)? Or perhaps another approach (the worst plan is to save the files in the database, but it is bad)","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":708,"Q_Id":18581117,"Users Score":2,"Answer":"There is no way to transactionally delete multiple files on normal filesystems (you might be able to find esoteric filesystems where it is, but even if so I doubt that helps you. Apparently your current filesystem doesn't even let you delete a file that's being read, so presumably you're stuck with what you have!).\nPerhaps you could save in the database not the file contents, but a list of which filenames in the filesystem \"really exist\". Refer to that list for anything that requires consistency. If file deletion fails, you can mark the file as \"not really existing\" and requiring future attempts at deletion, then retry whenever seems sensible (maybe an occasional maintenance job, maybe a helper process retrying each failure with exponential backoff to a limit).\nFor this to work either (a) your webserver must refer to the database before serving the file, or else (b) it must be OK for there to be a indefinite period after the file fails to delete, during which it may nevertheless be served. And of course there is also the \"natural race condition\" that a file that begins to be served before the deletion attempt, will complete its download even after the transaction is complete.\n[Edit: Ah, it just occurred to me that \"i have all the files in a folder for the main entity\" might actually be really helpful. In your transaction, rename the directory. That atomically \"removes\" all the files, from their old names at least, and it will fail (on filesystems that forbid that sort of thing) if any of the files is in use. If the rename succeeds, and nobody else knows the new name, then they won't be accessing the files and you should be able to delete them all without trouble. I think. Of course this doesn't work if you encounter another reason for failing to delete the file, because then you might be able to rename the folder but unable to delete the file.]","Q_Score":0,"Tags":"python,django,transactions","A_Id":18581616,"CreationDate":"2013-09-02T21:41:00.000","Title":"Delete files atomically\/transactionally in python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a Mac running OS X 10.6.8, which comes pre-installed with SQLite3 v3.6. I installed v3.8 using homebrew. But when I type \"sqlite3\" in my terminal it continues to run the old pre-installed version. Any help? Trying to learn SQL as I'm building my first web app.\nNot sure if PATH variable has anything to do with it, but running echo $PATH results in the following: \/usr\/local\/bin:\/Library\/Frameworks\/Python.framework\/Versions\/2.7\/bin:\/usr\/bin:\/bin:\/usr\/sbin:\/sbin:\/usr\/local\/bin:\/usr\/X11\/bin\nAnd the NEW version of SQLite3 is in the following directory: \/usr\/local\/Cellar\/sqlite\nI should add that I also downloaded the binary executable to my desktop, and that works if I click from my desktop, but doesn't work from the terminal.\nAny help would be greatly appreciated?","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1449,"Q_Id":18626114,"Users Score":0,"Answer":"To figure out exactly which sqlite3 binaries your system can find type which -a sqlite3. This will list the apps in the order that they are found according to your PATH variable, this also shows what order the thes ystem would use when figuring out which to run if you have multiple versions.\nHomebrew should normally links binaries into your \/usr\/local\/bin, but as sqlite3 is provided by MAC OS, it is only installed into \/usr\/local\/Cellar\/sqlite3, and not linked into \/usr\/local\/bin. As the Cellar path is not in your PATH variable, the system doesn't know that the binaries exist to run.\nLong story short, you can just run the Homebrew binary directly with \/usr\/local\/Cellar\/sqlite\/3.8.0\/bin\/sqlite3.","Q_Score":1,"Tags":"python,linux,macos,sqlite","A_Id":18629528,"CreationDate":"2013-09-05T00:54:00.000","Title":"Running upgraded version of SQLite (3.8) on Mac when Terminal still defaults to old version 3.6","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":0},{"Question":"I want to use BDB as a time-series data store, and planning to use the microseconds since epoch as the key values. I am using BTREE as the data store type.\nHowever, when I try to store integer keys, bsddb3 gives an error saying TypeError: Integer keys only allowed for Recno and Queue DB's. \nWhat is the best workaround? I can store them as strings, but that probably will make it unnecessarily slower.\nGiven BDB itself can handle any kind of data, why is there a restriction? can I sorta hack the bsddb3 implementation? has anyone used anyother methods?","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":689,"Q_Id":18664940,"Users Score":-1,"Answer":"Well, there's no workaround. But you can use two approaches\n\nStore the integers as string using str or repr. If the ints are big, you can even use string formatting\nuse cPickle\/pickle module to store and retrieve data. This is a good way if you have data types other than basic types. For basics ints and floats this actually is slower and takes more space than just storing strings","Q_Score":0,"Tags":"python,berkeley-db,bsddb","A_Id":18793657,"CreationDate":"2013-09-06T19:11:00.000","Title":"Use integer keys in Berkeley DB with python (using bsddb3)","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have some code that I am working on that scrapes some data from a website, and then extracts certain key information from that website and stores it in an object.  I create a couple hundred of these objects each day, each from unique url's.  This is working quite well, however, I'm inexperienced in what options are available to me in Python for persistence and what would be best suited for my needs.\nCurrently I am using pickle.  To do so, I am keeping all of these webpage objects and appending them in a list as new ones are created, then saving that list to a pickle (then reloading it whenever the list is to be updated).  However, as i'm in the order of some GB of data, i'm finding pickle to be somewhat slow.  It's not unworkable, but I'm wondering if there is a more well suited alternative.  I don't really want to break apart the structure of my objects and store it in a sql type database, as its important for me to keep the methods and the data as a single object.\nShelve is one option I've been looking into, as my impression is then that I wouldn't have to unpickle and pickle all the old entries (just the most recent day that needs to be updated), but am unsure if this is how shelve works, and how fast it is.  \nSo to avoid rambling on, my question is: what is the preferred persistence method for storing a large number of objects (all of the same type), to keep read\/write speed up as the collection grows?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":95,"Q_Id":18674630,"Users Score":0,"Answer":"Martijn's suggestion could be one of the alternatives.\nYou may consider to store the pickle objects directly in a sqlite database which still can manage from the python standard library.\nUse a StringIO object to convert between the database column and python object.\nYou didn't mention the size of each object you are pickling now. I guess it should stay well within sqlite's limit.","Q_Score":0,"Tags":"python,persistence","A_Id":18674706,"CreationDate":"2013-09-07T15:02:00.000","Title":"Persistence of a large number of objects","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"For a music project I want to find what which groups of artists users listens to. I have extracted three columns from the database: the ID of the artist, the ID of the user, and the percentage of all the users stream that is connected to that artist. \nE.g. Half of the plays from user 15, is of the artist 12. \n12 | 15 | 0.5\nWhat I hope to find is a methodology to group clusters of groups together, so e.g. find out that users who tends to listen to artist 12 also listens to 65, 74, and 34. \nI wonder what kind of methodologies that can be used for this grouping, and if there are any good sources for this approach (Python or Ruby would be great).","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":261,"Q_Id":18705223,"Users Score":0,"Answer":"Sounds like a classic matrix factorization task to me.\nWith a weighted matrix, instead of a binary one. So some fast algorithms may not be applicable, because they support binary matrixes only.\nDon't ask for source on Stackoverflow: asking for off-site resources (tools, libraries, ...) is off-topic.","Q_Score":0,"Tags":"python,ruby,data-mining,data-analysis","A_Id":18712558,"CreationDate":"2013-09-09T19:09:00.000","Title":"Data Mining: grouping based on two text values (IDs) and one numeric (ratio)","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm a beginner of openerp 7. i just want to know the details regarding how to generate report in openerp 7 in xls format. \nThe formats supported in OpenERP report types are : pdf, odt, raw, sxw, etc..\nIs there any direct feature that is available in OpenERP 7 regarding printing the report in EXCEL format(XLS)","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":2902,"Q_Id":18716623,"Users Score":0,"Answer":"In python library are available to export data in pdf and excel\nFor excel you can use:\n           1)xlwt\n           2)Elementtree\nFor pdf genration :\n           1)Pypdf\n           2)Reportlab \n      are available","Q_Score":1,"Tags":"python,openerp","A_Id":18716823,"CreationDate":"2013-09-10T10:34:00.000","Title":"How to print report in EXCEL format (XLS)","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"The context for this question is:\n\nA Google App Engine backend for a two-person multiplayer turn-based card game\nThe game revolves around different combinations of cards giving rise to different scores in the game\n\nObviously, one would store the state of a game in the GAE datastore, but I'm not sure on the approach for the design of the game logic itself.  It seems I might have two choices:\n\nStore entries in the datastore with a key that is a sorted list of the valid combinations of cards that can be player.  These will then map to the score values.  When a player tries to play a combination of cards, the server-side python will sort the combination appropriately and lookup the key.  If it succeeds, it can do the necessary updates for the score, if it fails then the combination wasn't valid.\nStore the valid combinations as a python dictionary written into the server-side code and perform the same lookups as above to test the validity\/get the score but without a trip to the datastore.\n\nFrom a cost point of view (datastore lookups aren't free), option 2 seems like it would be better.  But then there is the performance of the instance itself - will the startup time, processing time, memory usage start to tip me into greater expense?\nThere's also the code maintanence issue of constructing that Python dictionary, but I can bash together some scripts to help me write the code for that on the infrequently occasions that the logic changes.  I think there will be on the order of 1000 card combinations (that can produce a score) of between 2 and 6 cards if that helps anyone who wants to quantify the problem.\nI'm starting out with this design, and the summary of the above is whether it is sensible to store the static logic of this kind of game in the datastore, or simply keep it as part of the CPU bound logic?  What are the pros and cons of both approaches?","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":209,"Q_Id":18807022,"Users Score":1,"Answer":"If the logic is fixed, keep it in your code. Maybe you can procedurally generate the dicts on startup. If there is a dynamic component to the logic (something you want to update frequently), a data store might be a better bet, but it sounds like that's not applicable here. Unless the number of combinations runs over the millions, and you'd want to trade speed in favour of a lower memory footprint, stick with putting it in the application itself.","Q_Score":0,"Tags":"python,google-app-engine,google-cloud-datastore","A_Id":18807184,"CreationDate":"2013-09-14T22:29:00.000","Title":"Where to hold static information for game logic?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a postgres DB in which most of the tables have a column 'valid_time' indicating when the data in that row is intended to represent and an 'analysis_time' column, indicating when the estimate was made (this might be the same or a later time than the valid time in the case of a measurement or an earlier time in the case of a forecast). Typically there are multiple analysis times for each valid time, corresponding to different measurements (if you wait a bit, more data is available for a given time, so the analysis is better but the measurment is less prompt) and forecasts with different lead times.\nI am using SQLalchemy to access this DB in Python.\nWhat I would like to do is be able to pull out all rows with the most recent N unique datetimes of a specified column. For instance I might want the 3 most recent unique valid times, but this will typically be more than 3 rows, because there will be multiple analysis times for each of those 3 valid times.\nI am new to relational databases. In a sense there are two parts to this question; how can this be achieved in bare SQL and then how to translate that to the SQLalchemy ORM?","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":144,"Q_Id":18818634,"Users Score":1,"Answer":"I'm not sure about the SQLalchemy part, but as far as the SQL queries I would do it in two steps:\n\nGet the times.  For example, something like.\nSELECT DISTINCT valid_time FROM MyTable LIMIT 3 ORDER BY valid_time DESC;\nGet the rows with those times, using the previous step as a subquery:\nSELECT * FROM MyTable WHERE valid_time IN (SELECT DISTINCT valid_time FROM MyTable LIMIT 3 ORDER BY valid_time DESC);","Q_Score":0,"Tags":"python,sql,postgresql,sqlalchemy","A_Id":18818835,"CreationDate":"2013-09-15T23:45:00.000","Title":"Selecting the rows with the N most recent unique values of a datetime","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm looking into the software architecture for using a NoSQL database (MongoDB). I would ideally want to use a database independent ORM\/ODM for this, but I can't find any similar library to SQLAlchemy for NoSQL. Do you know any?\nI do find a lot of wrappers, but nothing that seems to be database independent. If there's none, is it because all the NoSQL databases out there have different use cases that a common ORM\/ODM wouldn't make sense like it does in the SQL case ?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":943,"Q_Id":18827379,"Users Score":0,"Answer":"Not sure about python, but in Java you can use frameworks like PlayORM for this purpose which supports Csasandra, HBase and MongoDb.","Q_Score":3,"Tags":"python,mongodb,nosql","A_Id":18980345,"CreationDate":"2013-09-16T11:54:00.000","Title":"NoSQL database independent ORM\/ODM for Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have multiple xlsx File which contain two worksheet(data,graph). I have created graph using xlsxwriter in graph worksheet and write data in data worksheet. So I need to combine all graph worksheet into single xlsx File. So My question is:\nopenpyxl : In openpyxl module, we can load another workbook and modify the value.is there anyway to append new worksheet of another File. For Example.\nI have two xlsx data.xlsx(graph worksheet) and data_1.xlsx(graph worksheet)\nSo Final xlsx (graph worksheet and graph_1 worksheet)\nxlsxwriter : As of my understanding, we can not modify existing xlsx File. Do we any update into this module.","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":2875,"Q_Id":18913370,"Users Score":0,"Answer":"In answer to the last part of the question:\n\nxlsxwriter : As of my understanding, we can not modify existing xlsx File. Do we any update into this module.\n\nThat is correct. XlsxWriter only writes new files. It cannot be used to modify existing files. Rewriting files is not a planned feature.","Q_Score":2,"Tags":"python,openpyxl,xlsxwriter","A_Id":18917174,"CreationDate":"2013-09-20T09:33:00.000","Title":"Combine multiple xlsx File in single Xlsx File","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a 17gb xml file. I want to store it in MySQL. I tried it using xmlparser in php but it says maximum execution time of 30 seconds exceeded and inserts only a few rows. I even tried in python using element tree but it is taking lot of memory gives memory error in a laptop of 2 GB ram. Please suggest some efficient way of doing this.","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":215,"Q_Id":18945802,"Users Score":0,"Answer":"I'd say, turn off execution time limit in PHP (e.g. use a CLI script) and be patient. If you say it starts to insert something into database from a 17 GB file, it's actually doing a good job already. No reason to hasten it for such one-time job. (Increase memory limit too, just in case. Default 128 Mb is not that much.)","Q_Score":4,"Tags":"php,mysql,python-2.7,xml-parsing","A_Id":18945969,"CreationDate":"2013-09-22T16:01:00.000","Title":"extremely large xml file to mysql","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"in my program , ten process to write mongodb by update(key, doc, upsert=true)\nthe \"key\" is mongodb index, but is not unique.\n\nquery = {'hotelid':hotelid,\"arrivedate\":arrivedate,\"leavedate\":leavedate}\nwhere = \"data.%s\" % sourceid\ndata_value_where = {where:value}\nself.collection.update(query,{'$set':data_value_where},True)\n\nthe \"query\" id the not unique index\nI found sometimes the update not update exists data, but create a new data.\nI write a log for update method return, the return is \" {u'ok': 1.0, u'err': None, u'upserted': ObjectId('5245378b4b184fbbbea3f790'), u'singleShard': u'rs1\/192.168.0.21:10000,192.168.1.191:10000,192.168.1.192:10000,192.168.1.41:10000,192.168.1.113:10000', u'connectionId': 1894107, u'n': 1, u'updatedExisting': False, u'lastOp': 5928205554643107852L}\"\nI modify the update method to update(query, {'$set':data_value_where},upsert=True, safe=True),  but three is no change for this question.","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":820,"Q_Id":18995966,"Users Score":0,"Answer":"You would not end up with duplicate documents due to the operator you are using. You are actually using an atomic operator to update. \nAtomic (not to be confused with SQL atomic operations of all or nothing here) operations are done in sequence so each process will never pick up a stale document or be allowed to write two ids to the same array since the document each $set operation picks up will have the result of the last $set.\nThe fact that you did get duplicate documents most likely means you have an error in your code.","Q_Score":0,"Tags":"python,mongodb,pymongo","A_Id":18998582,"CreationDate":"2013-09-25T04:00:00.000","Title":"mongodb update(use upsert=true) not update exists data, insert a new data?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"in my program , ten process to write mongodb by update(key, doc, upsert=true)\nthe \"key\" is mongodb index, but is not unique.\n\nquery = {'hotelid':hotelid,\"arrivedate\":arrivedate,\"leavedate\":leavedate}\nwhere = \"data.%s\" % sourceid\ndata_value_where = {where:value}\nself.collection.update(query,{'$set':data_value_where},True)\n\nthe \"query\" id the not unique index\nI found sometimes the update not update exists data, but create a new data.\nI write a log for update method return, the return is \" {u'ok': 1.0, u'err': None, u'upserted': ObjectId('5245378b4b184fbbbea3f790'), u'singleShard': u'rs1\/192.168.0.21:10000,192.168.1.191:10000,192.168.1.192:10000,192.168.1.41:10000,192.168.1.113:10000', u'connectionId': 1894107, u'n': 1, u'updatedExisting': False, u'lastOp': 5928205554643107852L}\"\nI modify the update method to update(query, {'$set':data_value_where},upsert=True, safe=True),  but three is no change for this question.","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":820,"Q_Id":18995966,"Users Score":0,"Answer":"You can call it \"threadsafe\", as the update itself is not done in Python, it's in the mongodb, which is built to cater many requests at once.\nSo in summary: You can safely do that.","Q_Score":0,"Tags":"python,mongodb,pymongo","A_Id":18996136,"CreationDate":"2013-09-25T04:00:00.000","Title":"mongodb update(use upsert=true) not update exists data, insert a new data?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am considering to serialize a big set of database records for cache in Redis, using python and Cassandra. I have either to serialize each record and persist a string in redis or to create a dictionary for each record and persist in redis as a list of dictionaries.\nWhich way is faster? pickle each record? or create a dictionary for each record?\nAnd second : Is there any method to fetch from database as list of dic's? (instead of a list of model obj's)","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":2722,"Q_Id":19025952,"Users Score":3,"Answer":"Instead of serializing your dictionaries into strings and storing them in a Redis LIST (which is what it sounds like you are proposing), you can store each dict as a Redis HASH. This should work well if your dicts are relatively simple key\/value pairs. After creating each HASH you could add the key for the HASH to a LIST, which would provide you with an index of keys for the hashes. The benefits of this approach could be avoiding or lessening the amount of serialization needed, and may make it easier to use the data set in other applications and from other languages.\nThere are of course many other approaches you can take and that will depend on lots of factors related to what kind of data you are dealing with and how you plan to use it.\nIf you do go with serialization you might want to at least consider a more language agnostic serialization format, like JSON, BSON, YAML, or one of the many others.","Q_Score":4,"Tags":"python,redis,cassandra,cql,cqlengine","A_Id":19033019,"CreationDate":"2013-09-26T10:39:00.000","Title":"Python - Redis : Best practice serializing objects for storage in Redis","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"datetime is stored in postgres DB with UTC. I could see that the date is 2013-09-28 00:15:52.62504+05:30 in postgres table. \nBut when I fetch the value via django model, I get the  same datetime field as datetime.datetime(2013, 9, 27, 18, 45, 52, 625040, tzinfo=).\nUSE_TZ is True and TIME_ZONE is 'Asia\/Kolkata' in settings.py file. I think saving to DB works fine as DB contains datetime with correct UTC of +5:30.\nWhat am i doing wrong here?\nPlease help. \nThanks\nKumar","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1585,"Q_Id":19058491,"Users Score":3,"Answer":"The issue has been solved. The problem was that I was using another naive datetime field for calculation of difference in time, whereas the DB field was an aware field. I then converted the naive to timezone aware date, which solved the issue.\nJust in case some one needs to know.","Q_Score":2,"Tags":"python,django,postgresql,timezone","A_Id":19076075,"CreationDate":"2013-09-27T19:19:00.000","Title":"Postgres datetime field fetched without timezone in django","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm a complete beginner to Flask and I'm starting to play around with making web apps. \nI have a hard figuring out how to enforce unique user names. I'm thinking about how to do this in SQL, maybe with something like user_name text unique on conflict fail, but then how to I catch the error back in Python?\nAlternatively, is there a way to manage this that's built in to Flask?","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1118,"Q_Id":19086885,"Users Score":0,"Answer":"You can use SQLAlchemy.It's a plug-in","Q_Score":1,"Tags":"python,sql,web-applications,flask","A_Id":19087185,"CreationDate":"2013-09-30T05:17:00.000","Title":"How do I enforce unique user names in Flask?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a program which calculates a set of plain interlinked objects (the objects consist of properties which basically are either String, int or link to another object).\nI would like to have the objects stored in a relational database for easy SQL querying (from another program).\nMoreover, the objects (classes) tend to change and evolve. I would like to have a generic solution not requiring any changes in the 'persistence layer' whenever the classes evolve.\nDo you see any way to do that?","AnswerCount":4,"Available Count":1,"Score":0.049958375,"is_accepted":false,"ViewCount":60,"Q_Id":19142497,"Users Score":1,"Answer":"What about storing the objects in JSON?\nYou could write a function that serialize your object before storing it into the database.\nIf you have a specific identifier for your objects, I would suggest to use it as index so that you can easily retrieve it.","Q_Score":1,"Tags":"python,database,orm","A_Id":19142716,"CreationDate":"2013-10-02T16:56:00.000","Title":"Store Python objects in a database for easy quering","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am dealing with a doubt about sqlalchemy and objects refreshing!\nI am in the situation in what I have 2 sessions, and the same object has been queried in both sessions! For some particular thing I cannot to close one of the sessions.\nI have modified the object and commited the changes in session A, but in session B, the attributes are the initial ones! without modifications!\nShall I implement a notification system to communicate changes or there is a built-in way to do this in sqlalchemy?","AnswerCount":6,"Available Count":1,"Score":1.0,"is_accepted":false,"ViewCount":54352,"Q_Id":19143345,"Users Score":9,"Answer":"I just had this issue and the existing solutions didn't work for me for some reason.  What did work was to call session.commit().  After calling that, the object had the updated values from the database.","Q_Score":37,"Tags":"python,mysql,session,notifications,sqlalchemy","A_Id":54821257,"CreationDate":"2013-10-02T17:43:00.000","Title":"About refreshing objects in sqlalchemy session","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm currently using SQLAlchemy with two distinct session objects. In one object, I am inserting rows into a mysql database. In the other session I am querying that database for the max row id. However, the second session is not querying the latest from the database. If I query the database manually, I see the correct, higher max row id.\nHow can I force the second session to query the live database?","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1599,"Q_Id":19159142,"Users Score":0,"Answer":"Had a similar problem, for some reason i had to commit both sessions. Even the one that is only reading.\nThis might be a problem with my code though, cannot use same session as it the code will run on different machines. Also documentation of SQLalchemy says that each session should be used by one thread only, although 1 reading and 1 writing should not be a problem.","Q_Score":2,"Tags":"python,mysql,database,session,sqlalchemy","A_Id":49755122,"CreationDate":"2013-10-03T12:22:00.000","Title":"How to force SQLAlchemy to update rows","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm working with a somewhat large set (~30000 records) of data that my Django app needs to retrieve on a regular basis.  This data doesn't really change often (maybe once a month or so), and the changes that are made are done in a batch, so the DB solution I'm trying to arrive at is pretty much read-only.  \nThe total size of this dataset is about 20mb, and my first thought is that I can load it into memory (possibly as a singleton on an object) and access it very fast that way, though I'm wondering if there are other, more efficient ways of decreasing the fetch time by avoiding disk I\/O.  Would memcached be the best solution here? Or would loading it into an in-memory SQLite DB be better?  Or loading it on app startup simply as an in-memory variable?","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1409,"Q_Id":19310083,"Users Score":0,"Answer":"Does the disk IO really become the bottleneck of your application's performance and affect your user experience? If not, I don't think this kind of optimization is necessary.\nOperating system and RDBMS (e.g MySQL , PostgresQL) are really smart nowdays. The data in the disk will be cached in memory by RDBMS and OS automatically.","Q_Score":2,"Tags":"python,django,sqlite,orm,memcached","A_Id":19311615,"CreationDate":"2013-10-11T04:06:00.000","Title":"Load static Django database into memory","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a workbook that has some sheets in it.  One of the sheets has charts in it.  I need to use xlrd or openpyxl to edit another sheet, but, whenever I save the workbook, the charts are gone.\nAny workaround to this?  Is there another python package that preserves charts and formatting?","AnswerCount":1,"Available Count":1,"Score":0.3799489623,"is_accepted":false,"ViewCount":477,"Q_Id":19323049,"Users Score":2,"Answer":"This is currently not possible with either but I hope to have it in openpyxl 2.x. Patches \/ pull requests always welcome! ;-)","Q_Score":4,"Tags":"python,xlrd,xlwt,openpyxl,xlutils","A_Id":20910668,"CreationDate":"2013-10-11T16:33:00.000","Title":"How can I edit Excel Workbooks using XLRD or openpyxl while preserving charts?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a simple python\/Django Application in which I am inserting records in database through some scanning event. And I am able to show the data on a simple page. I keep reloading the page every second to show the latest inserted database records.But I want it to improve so that page should update the records when ever new entry comes in database, instead of reloading every second.\nIs there any way to do this?\nDatabase: I am using mysql\nPython: Python 2.7\nFramework: Django","AnswerCount":3,"Available Count":1,"Score":0.1325487884,"is_accepted":false,"ViewCount":824,"Q_Id":19332760,"Users Score":2,"Answer":"you need to elemplments the  poll\/long poll or server push.","Q_Score":1,"Tags":"python,mysql,django","A_Id":19333028,"CreationDate":"2013-10-12T09:38:00.000","Title":"Updating client page only when new entry comes in database in Django","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I understand that ForeignKey constrains a column to be an id value contained in another table so that entries in two different tables can be easily linked, but I do not understand the behavior of relationships(). As far as I can tell, the primary effect of declaring a relationship between Parent and Child classes is that parentobject.child will now reference the entries linked to the parentobject in the children table. What other effects does declaring a relationship have? How does declaring a relationship change the behavior of the SQL database or how SQLAlchemy interacts with the database?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":251,"Q_Id":19366605,"Users Score":5,"Answer":"It doesn't do anything at the database level, it's purely for convenience.  Defining a relationship lets SQLAlchemy know how to automatically query for the related object, rather than you having to manually use the foreign key.  SQLAlchemy will also do other high level management such as allowing assignment of objects and cascading changes.","Q_Score":1,"Tags":"python,sql,sqlalchemy,relationship","A_Id":19369883,"CreationDate":"2013-10-14T18:21:00.000","Title":"SQLAlchemy Relationships","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm just curious if there's a way to make the no default value warning I get from Storm to go away. I have an insert trigger in MySQL that handles these fields and everything is functioning as expected so I just want to remove this unnecessary information. I tried setting the default value to None but that causes an error because the fields do not allow nulls. So how do I make the warning go away?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":770,"Q_Id":19373289,"Users Score":0,"Answer":"Is it not possible for you to remove the 'IsNull' constraint from your MySQL database? I'm not aware of any where it is not possible to do this. Otherwise you could set a default string which represents a null value.","Q_Score":1,"Tags":"python,mysql,apache-storm","A_Id":20010872,"CreationDate":"2013-10-15T04:26:00.000","Title":"How can I avoid \"Warning: Field 'xxx' doesn't have a default value\" in Storm?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a few large hourly upload tables with RECORD fieldtypes. I want to pull select records out of those tables and put them in daily per-customer tables. The trouble I'm running into is that using QUERY to do this seems to flatten the data out.\nIs there some way to preserve the nested RECORDs, or do I need to rethink my approach?\nIf it helps, I'm using the Python API.","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":234,"Q_Id":19458338,"Users Score":0,"Answer":"Unfortunately, there isn't a way to do this right now, since, as you realized, all results are flattened.","Q_Score":1,"Tags":"python,google-bigquery","A_Id":19459294,"CreationDate":"2013-10-18T20:17:00.000","Title":"Bigquery: how to preserve nested data in derived tables?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm looking for a simple way to extract text from excel\/word\/ppt files. The objective is to index contents in whoosh for search with haystack.\nThere are some packages like xlrd and pandas that work for excel, but they go way beyond what I need, and I'm not really sure that they will actually just print the cell's unformatted text content straight from the box.\nAnybody knows of an easy way around this? My guess is ms office files must be xml-shaped. \nThanks!\nA.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":631,"Q_Id":19500625,"Users Score":2,"Answer":"I've done this \"by hand\" before--as it turns out, .(doc|ppt|xls)x files are just zip files which contain .xml files with all of your content. So you can use zipfile and your favorite xml parser to read the contents if you can find no better tool to do it.","Q_Score":1,"Tags":"python,django-haystack,whoosh","A_Id":19500864,"CreationDate":"2013-10-21T17:07:00.000","Title":"Extract text from ms office files with python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"Rackspace has added the feature to select certain cloud servers (as hosts) while creating a user in a cloud database instance. This allows the specified user to be accessed, only from those cloud servers.\nSo I would like to know whether there is an API available in pyrax(python SDK for Rackspace APIs) to accomplish this or not.\nIf possible, then how to pass multiple cloud server IPs using the API.\nThanks,","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":70,"Q_Id":19585830,"Users Score":0,"Answer":"I released version 1.6.1 of pyrax a few days ago that adds support for the 'host' parameter for users, as well as for Cloud Database backups.","Q_Score":1,"Tags":"python,mysql,database,cloud,rackspace-cloud","A_Id":19761340,"CreationDate":"2013-10-25T09:17:00.000","Title":"Host Parameter While Creating a User in Rackspace Cloud Database Instance","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"We are building a datawarehouse in PostgreSQL. We want to connect to different data sources. Most data will come from ms access. We not not python experts (yet :-)).\nWe found several database connectors. We want to use (as much as possible) standard SQL for our queries.\nWe looked at pyodbc pscopg2.\nGiven that we use MS Access and PostgreSQL and want to have the same query syntax and return data types; Which drivers should we use ?","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":126,"Q_Id":19605580,"Users Score":1,"Answer":"Your query syntax differences will depend on PostgreSQL extensions vs MS Access-specific quirks.  The psycodb and pyodbc will both provide a query interface using whatever SQL dialect (with quirks) the underlying db connections provide.","Q_Score":0,"Tags":"python,postgresql,ms-access,psycopg2,pyodbc","A_Id":20310119,"CreationDate":"2013-10-26T10:25:00.000","Title":"python postgresql ms access driver advice","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"The goal is to find values in an Excel spreadsheet which match values in a separate list, then highlight the row with a fill color (red) where matches are found. In other words:\n\nExcel file A: source list (approximately 200 items)\nExcel file B: has one column containing the list we are checking; must apply fill color (red) to entire row where matches are found\n\nWondering what the best approach might be. I'm currently using AppleScript to highlight and sort data in a large volume of spreadsheets; a looped find checks each cell in a range for a single string of text and colors all matching rows. While this task is similar, the source list contains hundreds of items so it feels silly (and very slow) to include all this data in the actual script. Any suggestions would be greatly appreciated.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":961,"Q_Id":19612872,"Users Score":0,"Answer":"I don't know what format your original list is in, but this sounds like a job for conditional formatting, if you can get the list into Excel.  You can do conditional formatting based on a formula, and you can use a VLOOKUP() formula to do it.","Q_Score":2,"Tags":"python,regex,excel,macos,applescript","A_Id":20011728,"CreationDate":"2013-10-26T23:07:00.000","Title":"Find text in Excel file matching text in separate file, then apply fill color to row","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'd like my Python script to read some data out of a postgresql dump file. The Python will be running on a system without postgresql, and needs to process the data in a dump file.\nIt looks fairly straightforward to parse the CREATE TABLE calls to find the column names, then the INSERT INTO rows to build the contents.  But I'm sure there would be quite a few gotchas in doing this reliably.  Does anyone know of a module which will do this?","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":4660,"Q_Id":19638019,"Users Score":1,"Answer":"Thanks for all the comments, even if they are mostly \"don't do this!\" ;)\nGiven:\n\nThe dump is always produced in the same format from a 3rd-party system\nI need to be able to automate reading it on another 3rd-party system without postgres\n\nI've gone for writing my own basic parser, which is doing a good enough job for what I require.","Q_Score":3,"Tags":"python,postgresql","A_Id":19703149,"CreationDate":"2013-10-28T14:53:00.000","Title":"How to read postgresql dump file in Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm using Django + Postgres. When I do a SQL query using psql, \ne.g. \\d+ myapp_stories\ncorrectly shows the columns in the table\nBut when I do SELECT * FROM myapp_stories, it returns nothing. But querying the same database & table from my python code returns data just fine. So there is data in the table. Any thoughts? I'm using venv, not sure if that affects anything. Thanks in advance!","AnswerCount":2,"Available Count":2,"Score":0.0996679946,"is_accepted":false,"ViewCount":82,"Q_Id":19664732,"Users Score":1,"Answer":"I guess you forgot to enter semicolon:\n\nSELECT * FROM myapp_stories;","Q_Score":1,"Tags":"python,django,postgresql","A_Id":19665116,"CreationDate":"2013-10-29T17:05:00.000","Title":"SELECT using psql returns no rows even though data is there","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm using Django + Postgres. When I do a SQL query using psql, \ne.g. \\d+ myapp_stories\ncorrectly shows the columns in the table\nBut when I do SELECT * FROM myapp_stories, it returns nothing. But querying the same database & table from my python code returns data just fine. So there is data in the table. Any thoughts? I'm using venv, not sure if that affects anything. Thanks in advance!","AnswerCount":2,"Available Count":2,"Score":0.0996679946,"is_accepted":false,"ViewCount":82,"Q_Id":19664732,"Users Score":1,"Answer":"Prefix the table in your query with the schema, as the search_path might be causing your query (or psql) to look in a schema other than what you are expecting.","Q_Score":1,"Tags":"python,django,postgresql","A_Id":19666882,"CreationDate":"2013-10-29T17:05:00.000","Title":"SELECT using psql returns no rows even though data is there","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have PyQt application which uses SQLite files to store data and would like to allows multiple users to read and write to the same database.  It uses QSqlDatabase and QSqlTableModels with item views for reading and editing.  \nAs is multiple users can launch the application and read\/write to different tables.  The issue is this:\nSay user1's application reads table A then user2 writes to index 0,0 on table A.  Since user1 application has already read and cached that cell and doesn't see user2's change right away.  The Qt item view's will update when the dataChanged signal emits but in this case the data is being changed by another application instance.  Is there some way to trigger file changes by another application instance.  What's the best way to handle this.  \nI'm assuming this is really best solved by using an SQL server host connection rather than SQLite for the database, but in the realm of SQLite what would be my closest workaround option?\nThanks","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":74,"Q_Id":19759594,"Users Score":0,"Answer":"SQLite has no mechanism by which another user can be notified.\nYou have to implement some communication mechanism outside of SQLite.","Q_Score":0,"Tags":"python,sql,qt,sqlite","A_Id":19764106,"CreationDate":"2013-11-03T23:40:00.000","Title":"Signaling Cell Changes across multiple QSqlDatabase to the same SQliteFile","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":1,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm trying to get Django running on OS X Mavericks and I've encountered a bunch of errors along the way, the latest way being that when runpython manage.py runserver to see if everything works, I get this error, which I believe means that it misses libssl:\n\nImportError: dlopen(\/Library\/Frameworks\/Python.framework\/Versions\/2.7\/lib\/python2.7\/site-packages\/psycopg2\/_psycopg.so, 2): Library not loaded: @loader_path\/..\/lib\/libssl.1.0.0.dylib Referenced from: \/Library\/Frameworks\/Python.framework\/Versions\/2.7\/lib\/python2.7\/site-packages\/psycopg2\/_psycopg.so Reason: image not found\n\nI have already upgraded Python to 2.7.6 with the patch that handles some of the quirks of Mavericks.\nAny ideas?\nFull traceback:\n\nUnhandled exception in thread started by >\n  Traceback (most recent call last):\n    File \"\/Library\/Frameworks\/Python.framework\/Versions\/2.7\/lib\/python2.7\/site-packages\/django\/core\/management\/commands\/runserver.py\", line 93, in inner_run\n      self.validate(display_num_errors=True)\n    File \"\/Library\/Frameworks\/Python.framework\/Versions\/2.7\/lib\/python2.7\/site-packages\/django\/core\/management\/base.py\", line 280, in validate\n      num_errors = get_validation_errors(s, app)\n    File \"\/Library\/Frameworks\/Python.framework\/Versions\/2.7\/lib\/python2.7\/site-packages\/django\/core\/management\/validation.py\", line 28, in get_validation_errors\n      from django.db import models, connection\n    File \"\/Library\/Frameworks\/Python.framework\/Versions\/2.7\/lib\/python2.7\/site-packages\/django\/db\/init.py\", line 40, in \n      backend = load_backend(connection.settings_dict['ENGINE'])\n    File \"\/Library\/Frameworks\/Python.framework\/Versions\/2.7\/lib\/python2.7\/site-packages\/django\/db\/init.py\", line 34, in getattr\n      return getattr(connections[DEFAULT_DB_ALIAS], item)\n    File \"\/Library\/Frameworks\/Python.framework\/Versions\/2.7\/lib\/python2.7\/site-packages\/django\/db\/utils.py\", line 93, in getitem\n      backend = load_backend(db['ENGINE'])\n    File \"\/Library\/Frameworks\/Python.framework\/Versions\/2.7\/lib\/python2.7\/site-packages\/django\/db\/utils.py\", line 27, in load_backend\n      return import_module('.base', backend_name)\n    File \"\/Library\/Frameworks\/Python.framework\/Versions\/2.7\/lib\/python2.7\/site-packages\/django\/utils\/importlib.py\", line 35, in import_module\n      import(name)\n    File \"\/Library\/Frameworks\/Python.framework\/Versions\/2.7\/lib\/python2.7\/site-packages\/django\/db\/backends\/postgresql_psycopg2\/base.py\", line 14, in \n      from django.db.backends.postgresql_psycopg2.creation import DatabaseCreation\n    File \"\/Library\/Frameworks\/Python.framework\/Versions\/2.7\/lib\/python2.7\/site-packages\/django\/db\/backends\/postgresql_psycopg2\/creation.py\", line 1, in \n      import psycopg2.extensions\n    File \"\/Library\/Frameworks\/Python.framework\/Versions\/2.7\/lib\/python2.7\/site-packages\/psycopg2\/init.py\", line 50, in \n      from psycopg2._psycopg import BINARY, NUMBER, STRING, DATETIME, ROWID\n  ImportError: dlopen(\/Library\/Frameworks\/Python.framework\/Versions\/2.7\/lib\/python2.7\/site-packages\/psycopg2\/_psycopg.so, 2): Library not loaded: @loader_path\/..\/lib\/libssl.1.0.0.dylib\n    Referenced from: \/Library\/Frameworks\/Python.framework\/Versions\/2.7\/lib\/python2.7\/site-packages\/psycopg2\/_psycopg.so\n    Reason: image not found","AnswerCount":5,"Available Count":1,"Score":0.0798297691,"is_accepted":false,"ViewCount":9380,"Q_Id":19767569,"Users Score":2,"Answer":"It seems that it's libssl.1.0.0.dylib that is missing. Mavericks comme with libssl 0.9.8. You need to install libssl via homebrew.\nIf loaderpath points to \/usr\/lib\/, you also need to symlink libssl from \/usr\/local\/Cell\/openssl\/lib\/ into \/usr\/lib.","Q_Score":2,"Tags":"python,django,macos,postgresql","A_Id":19772866,"CreationDate":"2013-11-04T12:15:00.000","Title":"Django can't find libssl on OS X Mavericks","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I have two different python programs. One of the program uses the python BeautifulSoup module, the other uses the MySQLdb module. When I run the python files individually, I have no  problem and the program run fine and give me the desired output. However I need to combine the two programs so to achieve my ultimate goal. However the Beautiful soup module only runs if I open it in python 2.7.3 and the MySQLdb runs only on the python 2.7.4 (64bit) version. I installed both the modules exactly the way it was mentioned in the docs. Any help will be much appreciated.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":50,"Q_Id":19799605,"Users Score":0,"Answer":"If you have 2 versions of python installed on your system, then you've somehow installed one library in each of them.\nYou either need to install both libraries in both versions of python (which 2 seperate versions of pip can do), or need to setup your PYTHONPATH environment variable to allow loading of modules from additional paths (like the site-packages folder of the python 2.7.4 (64bit) installation from the python 2.7.3 executable).","Q_Score":0,"Tags":"python,python-2.7,beautifulsoup,mysql-python","A_Id":19801757,"CreationDate":"2013-11-05T21:42:00.000","Title":"Modules not Working across different python versions","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Situation: \nI have a requirement to use connection pooling while connecting to Oracle database in python. Multiple python applications would use the helper connection libraries I develop.\nMy Thought Process:\nHere I can think of two ways of connection pooling:\n1) Let connection pool be maintained and managed by database itself (as provided by Oracle's DRCP) and calling modules just ask connections from the connection broker described by Oracle DRCP.\n2) Have a server process that manages the connection pool and all caller modules ask for connections from this pool (like dbcp?)\nWhat suggestions do I need:\noption 1) looks very straight forward since pool does not need to be stored by application. \nBut I wanted to know what advantages do I get other than simplicity using option 1)?\nI am trying to avoid option 2) since it would require a dedicated server process always running (considering shelving is not possible for connection objects).\nIs there any other way?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":622,"Q_Id":19848191,"Users Score":0,"Answer":"Let the database handle the pool. . . it's smarter than you'll be, and you'll leverage every bug fix\/performance improvement Oracle's installed base comes up with.","Q_Score":4,"Tags":"python,oracle,connection-pooling","A_Id":19848278,"CreationDate":"2013-11-07T22:40:00.000","Title":"Application vs Database Resident Connection Pool","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I got one  table in which modifications are made :-account_bank_statement, what other tables are needed for the point of sale and if i make a sale in which tables modifications are made.I want to make a sale but not through the pos provided.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":49,"Q_Id":19892934,"Users Score":0,"Answer":"All the sales done through post is registered in post.order. If you are creating orders from an external source other than pos, you can create the order in this table and call the confirm bottom action. Rest changes in all other table will be done automatically..","Q_Score":0,"Tags":"python,openerp","A_Id":19897059,"CreationDate":"2013-11-10T17:46:00.000","Title":"In which tables changes are made in openERP when an items is sold at Point of sale","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I know there exists a plugin for nginx to load the config through perl. I was wondering, does anyone have any experience doing this without using a plugin? Possibly a fuse-backed Python script that queries a DB?\nI would really like to not use the perl plugin, as it doesn't seem that stable.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":722,"Q_Id":19957613,"Users Score":1,"Answer":"I haven't seen any working solution to solve your task, a quick google search doesn't give any useful information either (it doesn't look like HttpPerlModule could help with DB stored configuration). \nIt sounds like it's a good task to develop and contribute to Nginx project !","Q_Score":0,"Tags":"python,sql,configuration,nginx,fuse","A_Id":20018813,"CreationDate":"2013-11-13T15:23:00.000","Title":"Running Nginx with a database-backed config file","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm trying to share an in-memory database between processes. I'm using Python's sqlite3. The idea is to create a file in \/run\/shm and use it as a database. Questions are:\n\nIs that safe? In particular: do read\/write locks (fcntl) work the same in shm?\nIs that a good idea in the first place? I'd like to keep things simple and not have to create a separate database process.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":230,"Q_Id":19976664,"Users Score":0,"Answer":"I've tested fcntl (in Python) with shm files and it seems that locking works correctly. Indeed, from process point of view it is a file and OS handles everything correctly.\nI'm going to keep this architecture since it is simple enough and I don't see any (major) drawbacks.","Q_Score":1,"Tags":"python,sqlite,shared-memory","A_Id":20004051,"CreationDate":"2013-11-14T11:38:00.000","Title":"sqlite3 database in shared memory","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm working on a web app in Python (Flask) that, essentially, shows the user information from a PostgreSQL database (via Flask-SQLAlchemy) in a random order, with each set of information being shown on one page. Hitting a Next button will direct the user to the next set of data by replacing all data on the page with new data, and so on.\nMy conundrum comes with making the presentation truly random - not showing the user the same information twice by remembering what they've seen and not showing them those already seen sets of data again.\nThe site has no user system, and the \"already seen\" sets of data should be forgotten when they close the tab\/window or navigate away.\nI should also add that I'm a total newbie to SQL in general.\nWhat is the best way to do this?","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":512,"Q_Id":20072309,"Users Score":1,"Answer":"The easiest way is to do the random number generation in javascript at the client end...\nTell the client what the highest number row is, then the client page keeps track of which ids it has requested (just a simple js array).  Then when the \"request next random page\" button is clicked, it generates a new random number less than the highest valid row id, and providing that the number isn't in its list of previously viewed items, it will send a request for that item.\nThis way, you (on the server) only have to have 2 database accessing views:\n\nmain page (which gives the js, and the highest valid row id)\ndisplay an item (by id) \n\nYou don't have any complex session tracking, and the user's browser is only having to keep track of a simple list of numbers, which even if they personally view several thousand  different items is still only going to be a meg or two of memory.\nFor performance reasons, you can even pre-fetch the next item as soon as the current item loads, so that it displays instantly and loads the next one in the background while they're looking at it. (jQuery .load() is your friend :-) )\nIf you expect a large number of items to be removed from the database (so that the highest number is not helpful), then you can instead generate a list of random ids, send that, and then request them one at a time.  Pre-generate the random list, as it were.\nHope this helps! :-)","Q_Score":1,"Tags":"python,sql,flask,flask-sqlalchemy","A_Id":20081554,"CreationDate":"2013-11-19T13:03:00.000","Title":"Best way to show a user random data from an SQL database?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am wondering if anyone knows a way to generate a connection to a SQLite database in python from a StringIO object.\nI have a compressed SQLite3 database file and I would like to decompress it using the gzip library and then connect to it without first making a temp file.\nI've looked into the slqite3 library source, but it looks like filename gets passed all the way through into the C code. Are there any other SQLite3 connection libraries that you could use a file ID for? Or is there some why I can trick the builtin sqlite3 library into thinking that my StringIO (or some other object type) is an actual file?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1371,"Q_Id":20084135,"Users Score":4,"Answer":"The Python sqlite3 module cannot open a database from a file number, and even so, using StringIO will not give you a file number (since it does not open a file, it just emulates the Python file object).\nYou can use the :memory: special file name to avoid writing a file to disk, then later write it to disk once you are done with it. This will also make sure the file is optimized for size, and you can opt not to write e.g. indexes if size is really a big issue.","Q_Score":10,"Tags":"python,sqlite,stringio","A_Id":20084315,"CreationDate":"2013-11-19T23:10:00.000","Title":"SQLite3 connection from StringIO (Python)","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a MYSQL database with users table, and I want to make a python application which allows me to login to that database with the IP, pass, username and everything hidden. The thing is, the only IP which is allowed to connect to that mysql database, is the server itself (localhost).\nHow do I make a connection to that database from a user's computer, and also be able to retrieve data from it securely? Can I build some PHP script on the server that is able to take parameters and retrieve data to that user?","AnswerCount":3,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":143,"Q_Id":20193144,"Users Score":0,"Answer":"As i understood you are able to connect only with \"server itself (localhost)\" so to connect from any ip do this: \n     mysql> CREATE USER 'myname'@'%.mydomain.com' IDENTIFIED BY 'mypass';\nI agree with @Daniel no PHP script needed...","Q_Score":0,"Tags":"php,python,mysql,python-2.7","A_Id":20193357,"CreationDate":"2013-11-25T12:29:00.000","Title":"Secure MySQL Connection in Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a MYSQL database with users table, and I want to make a python application which allows me to login to that database with the IP, pass, username and everything hidden. The thing is, the only IP which is allowed to connect to that mysql database, is the server itself (localhost).\nHow do I make a connection to that database from a user's computer, and also be able to retrieve data from it securely? Can I build some PHP script on the server that is able to take parameters and retrieve data to that user?","AnswerCount":3,"Available Count":2,"Score":0.0665680765,"is_accepted":false,"ViewCount":143,"Q_Id":20193144,"Users Score":1,"Answer":"You should not make a connection from the user's computer. By default, most database configurations are done to allow only requests from the same server (localhost) to access the database. \nWhat you will need is this: \n\nA server side script such as Python, PHP, Perl, Ruby, etc to access the database. The script will be on the server, and as such, it will access the database locally\nSend a web request from the user's computer using Python, Perl, or any programming language to the server side script as described above.\nSo, the application on the user's computer sends a request to the script on the server. The script connects to the database locally, accesses the data, and  sends it back to the application. The application can then use the data as needed.\n\nThat is basically, what you are trying to achieve.  \nHope the explanation is clear and it helps.","Q_Score":0,"Tags":"php,python,mysql,python-2.7","A_Id":20193562,"CreationDate":"2013-11-25T12:29:00.000","Title":"Secure MySQL Connection in Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"win32com is a general library to access COM objects from Python.\nOne of the major hallmarks of this library is ability to manipulate excel documents.\nHowever, there is lots of customized modules, whose only purpose it to manipulate excel documents, like openpyxl, xlrd, xlwt, python-tablefu.\nAre these libraries any better for this specific task? If yes, in what respect?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":3031,"Q_Id":20263021,"Users Score":9,"Answer":"Open and write directly and efficiently excel files, for instance.\n\nwin32com uses COM communication, which while being very useful for certain purposes, it needs to perform complicated API calls that can be very slow (so to say, you are using code that controls Windows, that controls Excel)\nopenpyxl or others, just open an excel file, parse it and let you work with it.\n\nTry to populate an excel file with 2000 rows, 100 cells each, with win32com and then with any other direct parser. While a parser needs seconds, win32com will need minutes. \nBesides, openpyxl (I haven't tried the others) does not need that excel is installed in the system. It does not even need that the OS is windows.\nTotally different concepts. win32com is a piece of art that opens a door to automate almost anything, while the other option is just a file parser. In other words, to iron your shirt, you use a $20 iron, not a 100 ton metal sheet attached to a Lamborghini Diablo.","Q_Score":3,"Tags":"python,excel,win32com,xlrd,openpyxl","A_Id":20263978,"CreationDate":"2013-11-28T10:04:00.000","Title":"What do third party libraries like openpyxl or xlrd\/xlwt have, what win32com doesn't have?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"trying to import python-mysql.connector on Python 3.2.3 and receiving an odd stack. I suspect bad configuration on my ubuntu 12.04 install.\n\n    vfi@ubuntu:\/usr\/share\/pyshared$ python3\n    Python 3.2.3 (default, Sep 25 2013, 18:22:43) \n    [GCC 4.6.3] on linux2\n    Type \"help\", \"copyright\", \"credits\" or \"license\" for more information.\n    >>> import mysql.connector\n    Traceback (most recent call last):\n      File \"\", line 1, in \n    ImportError: No module named mysql.connector\n    Error in sys.excepthook:\n    Traceback (most recent call last):\n      File \"\/usr\/share\/pyshared\/apport_python_hook.py\", line 66, in apport_excepthook\n        from apport.fileutils import likely_packaged, get_recent_crashes\n      File \"apport\/__init__.py\", line 1, in \n        from apport.report import Report\n      File \"apport\/report.py\", line 20, in \n        import apport.fileutils\n      File \"apport\/fileutils.py\", line 22, in \n        from apport.packaging_impl import impl as packaging\n      File \"apport\/packaging_impl.py\", line 20, in \n        import apt\n      File \"apt\/__init__.py\", line 24, in \n        from apt.package import Package\n      File \"apt\/package.py\", line 1051\n        return file_list.read().decode(\"utf-8\").split(u\"\\n\")\n                                                          ^\n    SyntaxError: invalid syntax\n\n    Original exception was:\n    Traceback (most recent call last):\n      File \"\", line 1, in \n    ImportError: No module named mysql.connector\n\nhere is the related modules state on my pc:\n\nvfi@ubuntu:\/usr\/share\/pyshared$ sudo aptitude search python3-apt\ni   python3-apt                                                                                    - Python 3 interface to libapt-pkg                                                                        \np   python3-apt:i386                                                                               - Python 3 interface to libapt-pkg                                                                        \np   python3-apt-dbg                                                                                - Python 3 interface to libapt-pkg (debug extension)                                                      \np   python3-apt-dbg:i386                                                                           - Python 3 interface to libapt-pkg (debug extension)                                                      \nv   python3-apt-dbg:any                                                                            -                                                                                                         \nv   python3-apt-dbg:any:i386                                                                       -                                                                                                         \nv   python3-apt:any                                                                                -                                                                                                         \nv   python3-apt:any:i386                                                                           -                                                                                                         \nvfi@ubuntu:\/usr\/share\/pyshared$ sudo aptitude search python-apt\ni   python-apt                                                                                     - Python interface to libapt-pkg                                                                          \np   python-apt:i386                                                                                - Python interface to libapt-pkg                                                                          \ni   python-apt-common                                                                              - Python interface to libapt-pkg (locales)                                                                \np   python-apt-dbg                                                                                 - Python interface to libapt-pkg (debug extension)                                                        \np   python-apt-dbg:i386                                                                            - Python interface to libapt-pkg (debug extension)                                                        \nv   python-apt-dbg:any                                                                             -                                                                                                         \nv   python-apt-dbg:any:i386                                                                        -                                                                                                         \np   python-apt-dev                                                                                 - Python interface to libapt-pkg (development files)                                                      \np   python-apt-doc                                                                                 - Python interface to libapt-pkg (API documentation)                                                      \nv   python-apt-p2p                                                                                 -                                                                                                         \nv   python-apt-p2p-khashmir                                                                        -                                                                                                         \nv   python-apt:any                                                                                 -                                                                                                         \nv   python-apt:any:i386                                                                            -                                                                                                         \ni   python-aptdaemon                                                                               - Python module for the server and client of aptdaemon                                                    \np   python-aptdaemon-gtk                                                                           - Transitional dummy package                                                                              \ni   python-aptdaemon.gtk3widgets                                                                   - Python GTK+ 3 widgets to run an aptdaemon client                                                        \np   python-aptdaemon.gtkwidgets                                                                    - Python GTK+ 2 widgets to run an aptdaemon client                                                        \ni   python-aptdaemon.pkcompat                                                                      - PackageKit compatibilty for AptDaemon                                                                   \np   python-aptdaemon.test                                                                          - Test environment for aptdaemon clients                                                                  \nvfi@ubuntu:\/usr\/share\/pyshared$ sudo aptitude search python-mysql.connector\npi  python-mysql.connector                                                                         - pure Python implementation of MySQL Client\/Server protocol     \n\nHope you can help!\nThanks","AnswerCount":3,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":20264,"Q_Id":20275176,"Users Score":0,"Answer":"pip3 install mysql-connector-python worked for me","Q_Score":4,"Tags":"mysql,python-3.x,python-module","A_Id":65242155,"CreationDate":"2013-11-28T21:46:00.000","Title":"ImportError: No module named mysql.connector using Python3?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"trying to import python-mysql.connector on Python 3.2.3 and receiving an odd stack. I suspect bad configuration on my ubuntu 12.04 install.\n\n    vfi@ubuntu:\/usr\/share\/pyshared$ python3\n    Python 3.2.3 (default, Sep 25 2013, 18:22:43) \n    [GCC 4.6.3] on linux2\n    Type \"help\", \"copyright\", \"credits\" or \"license\" for more information.\n    >>> import mysql.connector\n    Traceback (most recent call last):\n      File \"\", line 1, in \n    ImportError: No module named mysql.connector\n    Error in sys.excepthook:\n    Traceback (most recent call last):\n      File \"\/usr\/share\/pyshared\/apport_python_hook.py\", line 66, in apport_excepthook\n        from apport.fileutils import likely_packaged, get_recent_crashes\n      File \"apport\/__init__.py\", line 1, in \n        from apport.report import Report\n      File \"apport\/report.py\", line 20, in \n        import apport.fileutils\n      File \"apport\/fileutils.py\", line 22, in \n        from apport.packaging_impl import impl as packaging\n      File \"apport\/packaging_impl.py\", line 20, in \n        import apt\n      File \"apt\/__init__.py\", line 24, in \n        from apt.package import Package\n      File \"apt\/package.py\", line 1051\n        return file_list.read().decode(\"utf-8\").split(u\"\\n\")\n                                                          ^\n    SyntaxError: invalid syntax\n\n    Original exception was:\n    Traceback (most recent call last):\n      File \"\", line 1, in \n    ImportError: No module named mysql.connector\n\nhere is the related modules state on my pc:\n\nvfi@ubuntu:\/usr\/share\/pyshared$ sudo aptitude search python3-apt\ni   python3-apt                                                                                    - Python 3 interface to libapt-pkg                                                                        \np   python3-apt:i386                                                                               - Python 3 interface to libapt-pkg                                                                        \np   python3-apt-dbg                                                                                - Python 3 interface to libapt-pkg (debug extension)                                                      \np   python3-apt-dbg:i386                                                                           - Python 3 interface to libapt-pkg (debug extension)                                                      \nv   python3-apt-dbg:any                                                                            -                                                                                                         \nv   python3-apt-dbg:any:i386                                                                       -                                                                                                         \nv   python3-apt:any                                                                                -                                                                                                         \nv   python3-apt:any:i386                                                                           -                                                                                                         \nvfi@ubuntu:\/usr\/share\/pyshared$ sudo aptitude search python-apt\ni   python-apt                                                                                     - Python interface to libapt-pkg                                                                          \np   python-apt:i386                                                                                - Python interface to libapt-pkg                                                                          \ni   python-apt-common                                                                              - Python interface to libapt-pkg (locales)                                                                \np   python-apt-dbg                                                                                 - Python interface to libapt-pkg (debug extension)                                                        \np   python-apt-dbg:i386                                                                            - Python interface to libapt-pkg (debug extension)                                                        \nv   python-apt-dbg:any                                                                             -                                                                                                         \nv   python-apt-dbg:any:i386                                                                        -                                                                                                         \np   python-apt-dev                                                                                 - Python interface to libapt-pkg (development files)                                                      \np   python-apt-doc                                                                                 - Python interface to libapt-pkg (API documentation)                                                      \nv   python-apt-p2p                                                                                 -                                                                                                         \nv   python-apt-p2p-khashmir                                                                        -                                                                                                         \nv   python-apt:any                                                                                 -                                                                                                         \nv   python-apt:any:i386                                                                            -                                                                                                         \ni   python-aptdaemon                                                                               - Python module for the server and client of aptdaemon                                                    \np   python-aptdaemon-gtk                                                                           - Transitional dummy package                                                                              \ni   python-aptdaemon.gtk3widgets                                                                   - Python GTK+ 3 widgets to run an aptdaemon client                                                        \np   python-aptdaemon.gtkwidgets                                                                    - Python GTK+ 2 widgets to run an aptdaemon client                                                        \ni   python-aptdaemon.pkcompat                                                                      - PackageKit compatibilty for AptDaemon                                                                   \np   python-aptdaemon.test                                                                          - Test environment for aptdaemon clients                                                                  \nvfi@ubuntu:\/usr\/share\/pyshared$ sudo aptitude search python-mysql.connector\npi  python-mysql.connector                                                                         - pure Python implementation of MySQL Client\/Server protocol     \n\nHope you can help!\nThanks","AnswerCount":3,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":20264,"Q_Id":20275176,"Users Score":5,"Answer":"Finally figured out what was my problem. \npython-mysql.connector was not a py3 package and apt-get nor aptitude was proposing such version.\nI managed to install it with pip3 which was not so simple on ubuntu 12.04 because it's only bundled with ubuntu starting at 12.10 and the package does not have the same name under pip...\n\nvfi@ubuntu:$sudo apt-get install python3-setuptools\nvfi@ubuntu:$sudo easy_install3 pip\n\nvfi@ubuntu:$ pip --version\npip 1.4.1 from \/usr\/local\/lib\/python3.2\/dist-packages\/pip-1.4.1-py3.2.egg (python 3.2)\n\nvfi@ubuntu:$sudo pip install mysql-connector-python","Q_Score":4,"Tags":"mysql,python-3.x,python-module","A_Id":20275797,"CreationDate":"2013-11-28T21:46:00.000","Title":"ImportError: No module named mysql.connector using Python3?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm getting different information for a particular thing and i'm storing those information in a dictionary\ne.g.  {property1:val , property2:val, property3:val} \nnow I have several dictionary of this type (as I get many things ..each dictionary is for a thing)\nnow I want to save information in DB so there would be as many columns as key:value pair in a dictionary \nso what is the best or simplest way to do that.\nPlease provide all steps to do that (I mean syntax for login in DB, push data into row or execute sql query etc... I hope there wont be more than 4 or 5 steps )\nPS: All dictionaries have the same keys, and each key always has the same value-type . and also number of columns are predefined.","AnswerCount":4,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":861,"Q_Id":20304863,"Users Score":0,"Answer":"You're doing it wrong!\nMake an object that represents a row in the database, use __getitem__ to pretend it's a dictionary. \nPut your database logic in that.\nDon't go all noSQL unless your tables are not related. Just by being tables they are ideal for SQL!","Q_Score":0,"Tags":"python,database,python-2.7,beautifulsoup,mysql-python","A_Id":20305193,"CreationDate":"2013-11-30T19:46:00.000","Title":"How to save Information in Database using BeautifulSoup","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm getting different information for a particular thing and i'm storing those information in a dictionary\ne.g.  {property1:val , property2:val, property3:val} \nnow I have several dictionary of this type (as I get many things ..each dictionary is for a thing)\nnow I want to save information in DB so there would be as many columns as key:value pair in a dictionary \nso what is the best or simplest way to do that.\nPlease provide all steps to do that (I mean syntax for login in DB, push data into row or execute sql query etc... I hope there wont be more than 4 or 5 steps )\nPS: All dictionaries have the same keys, and each key always has the same value-type . and also number of columns are predefined.","AnswerCount":4,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":861,"Q_Id":20304863,"Users Score":0,"Answer":"If your dictionaries all have the same keys, and each key always has the same value-type, it would be pretty straight-forward to map this to a relational database like MySQL.\nAlternatively, you could convert your dictionaries to objects and use an ORM like SQLAlchemy to do the back-end work.","Q_Score":0,"Tags":"python,database,python-2.7,beautifulsoup,mysql-python","A_Id":20305076,"CreationDate":"2013-11-30T19:46:00.000","Title":"How to save Information in Database using BeautifulSoup","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am hosting a web app at pythonanywhere.com and experiencing a strange problem. Every half-hour or so I am getting the OperationalError: (2006, 'MySQL server has gone away'). However, if I resave my wsgi.py file, the error disappears. And then appears again some half-an-hour later...\nDuring the loading of the main page, my app checks a BOOL field in a 1x1 table (basically whether sign-ups should be open or closed). The only other MySQL actions are inserts into another small table, but none of these appear to be associated with the problem.\nAny ideas for how I can fix this? I can provide more information as is necessary. Thanks in advance for your help.\nEDIT\nProblem turned out to be a matter of knowing when certain portions of code run. I assumed that every time a page loaded a new connection was opened. This was not the case; however, I have fixed it now.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":2432,"Q_Id":20308097,"Users Score":4,"Answer":"It normally because your mysql network connect be disconnected, may by your network gateway\/router, so you have two options. One is always build a mysql connect before every query (not using connect pool etc). Second is try and catch this error, then get connect and query db again.","Q_Score":2,"Tags":"python,mysql,mysql-python,pythonanywhere","A_Id":20309286,"CreationDate":"2013-12-01T02:33:00.000","Title":"Periodic OperationalError: (2006, 'MySQL server has gone away')","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Have some programming background, but in the process of both learning Python and making a web app, and I'm a long-time lurker but first-time poster on Stack Overflow, so please bear with me. \nI know that SQLite (or another database, seems like PostgreSQL is popular) is the way to store data between sessions. But what's the most efficient way to store large amounts of data during a session?  \nI'm building a script to identify the strongest groups of employees to work on various projects in a company. I have received one SQLite database per department containing employee data including skill sets, achievements, performance, and pay. \nMy script currently runs one SQL query on each database in response to an initial query by the user, pulling all the potentially-relevant employees and their data. It stores all of that data in a list of Python dicts so the end-user can mix-and-match relevant people. \nI see two other options: I could still run the comprehensive initial queries but instead of storing it in Python dicts, dump it all into SQLite temporary tables; my guess is that this would save some space and computing because I wouldn't have to store all the joins with each record. Or I could just load employee name and column\/row references, which would save a lot of joins on the first pass, then pull the data on the fly from the original databases as the user requests additional data, storing little if any data in Python data structures. \nWhat's going to be the most efficient? Or, at least, what is the most common\/proper way of handling large amounts of data during a session? \nThanks in advance!","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":2649,"Q_Id":20320642,"Users Score":1,"Answer":"Aren't you over-optimizing? You don't need the best solution, you need a solution which is good enough. \nImplement the simplest one, using dicts; it has a fair chance to be adequate. If you test it and then find it inadequate, try SQLite or Mongo (both have downsides) and see if it suits you better. But I suspect that buying more RAM instead would be the most cost-effective solution in your case.\n(Not-a-real-answer disclaimer applies.)","Q_Score":2,"Tags":"python,python-2.7,sqlite,sqlalchemy","A_Id":20320905,"CreationDate":"2013-12-02T04:05:00.000","Title":"What's faster: temporary SQL tables or Python dicts for session data?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have two databases (infact two database dump  ... db1.sql and db2.sql)\nboth database have only 1 table in each.\nin each table there are few columns (not equal number nor type) but 1 or 2 columns have same type and same value \ni just want to go through both databases and find a row from each table so that they both have one common value\nnow from these two rows(one from each table) i would extract some information and would write into a file.\nI want efficient methods to do that \nPS: If you got my question please edit the title \nEDIT: I want to compare these two tables(database) by a column which have contact number as primary key.\nbut the problem is one table has it is as an integer(big integer) and other table has it is as a string. now how could i inner-join them.\nbasically i dont want to create another database, i simply want to store two columns from each table into a file so I guess i dont need inner-join. do i? \ne.g. \nin table-1 = 9876543210\nin table-2 = \"9876543210\"","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":1032,"Q_Id":20348584,"Users Score":0,"Answer":"Not sure if I understand what it is you want to do. You want to match a value from a column from one table to a value from a column from another table?\nIf you'd have the data in two tables in a database, you could make an inner join.\nDepending on how big the file is, you could use a manual comparison tool like WinMerge.","Q_Score":0,"Tags":"python,mysql,sql,database,mysql-python","A_Id":20348851,"CreationDate":"2013-12-03T10:28:00.000","Title":"Compare two databases and find common value in a row","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have two databases (infact two database dump  ... db1.sql and db2.sql)\nboth database have only 1 table in each.\nin each table there are few columns (not equal number nor type) but 1 or 2 columns have same type and same value \ni just want to go through both databases and find a row from each table so that they both have one common value\nnow from these two rows(one from each table) i would extract some information and would write into a file.\nI want efficient methods to do that \nPS: If you got my question please edit the title \nEDIT: I want to compare these two tables(database) by a column which have contact number as primary key.\nbut the problem is one table has it is as an integer(big integer) and other table has it is as a string. now how could i inner-join them.\nbasically i dont want to create another database, i simply want to store two columns from each table into a file so I guess i dont need inner-join. do i? \ne.g. \nin table-1 = 9876543210\nin table-2 = \"9876543210\"","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":1032,"Q_Id":20348584,"Users Score":0,"Answer":"You can use Join with alias name.","Q_Score":0,"Tags":"python,mysql,sql,database,mysql-python","A_Id":20348719,"CreationDate":"2013-12-03T10:28:00.000","Title":"Compare two databases and find common value in a row","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"So I was making a simple chat app with python. I want to store user specific data in a database, but I'm unfamiliar with efficiency. I want to store usernames, public rsa keys, missed messages, missed group messages, urls to profile pics etc.\nThere's a couple of things in there that would have to be grabbed pretty often, like missed messages and profile pics and a couple of hashes. So here's the question: what database style would be fastest while staying memory efficient? I want it to be able to handle around 10k users (like that's ever gonna happen).\nheres some I thought of:\n\neverything in one file (might be bad on memory, and takes time to load in, important, as I would need to load it in after every change.)\nseperate files per user (Slower, but memory efficient)\nseperate files\nper data value\n\ndirectory for each user, seperate files for each value.\n\n\nthanks,and try to keep it objective so this isnt' instantly closed!","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":45,"Q_Id":20380661,"Users Score":0,"Answer":"The only answer possible at this point is 'try it and see'.\nI would start with MySQL (mostly because it's the 'lowest common denominator', freely available everywhere); it should do everything you need up to several thousand users, and if you get that far you should have a far better idea of what you need and where the bottlenecks are.","Q_Score":0,"Tags":"python,database,performance,chat","A_Id":20382525,"CreationDate":"2013-12-04T16:27:00.000","Title":"efficient database file trees","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Is there a way to know how many rows were commited on the last commit on a SQLAlchemy Session? For instance, if I had just inserted 2 rows, I wish to know that there were 2 rows inserted,  etc.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":193,"Q_Id":20389368,"Users Score":1,"Answer":"You can look at session.new, .dirty, and .deleted to see what objects will be committed, but that doesn't necessarily represent the number of rows, since those objects may set extra rows in a many-to-many association, polymorphic table, etc.","Q_Score":0,"Tags":"python,sqlalchemy","A_Id":20389560,"CreationDate":"2013-12-05T00:59:00.000","Title":"SQLAlchemy, how many rows were commited on last commit","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a giant (100Gb) csv file with several columns and a smaller (4Gb) csv also with several columns. The first column in both datasets have the same category. I want to create a third csv with the records of the big file which happen to have a matching first column in the small  csv. In database terms it would be a simple join on the first column. \nI am trying to find the best approach to go about this in terms of efficiency. As the smaller dataset fits in memory, I was thinking of loading it in a sort of set structure and then read the big file line to line and querying the in memory set, and write to file on positive.\nJust to frame the question in SO terms, is there an optimal way to achieve this?\nEDIT: This is a one time operation.\nNote: the language is not relevant, open to suggestions on column, row oriented databases, python, etc...","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":154,"Q_Id":20389982,"Users Score":0,"Answer":"If you are only doing this once, your approach should be sufficient. The only improvement I would make is to read the big file in chunks instead of line by line. That way you don't have to hit the file system as much. You'd want to make the chunks as big as possible while still fitting in memory.\nIf you will need to do this more than once, consider pushing the data into some database. You could insert all the data from the big file and then \"update\" that data using the second, smaller file to get a complete database with one large table with all the data. If you use a NoSQL database like Cassandra this should be fairly efficient since Cassandra is pretty good and handling writes efficiently.","Q_Score":0,"Tags":"c#,python,database,bigdata","A_Id":20390085,"CreationDate":"2013-12-05T02:00:00.000","Title":"Intersecting 2 big datasets","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Just wondering how to store files in the google app engine datastore.\nThere are lots of examples on the internet, but they are using blobstore\nI have tried importing db.BlobProperty, but when i put() the data\nit shows up as a <Blob> i think. It appears like there is no data\nSimilar to None for a string\nAre there any examples of using the Datastore to store files\nOr can anyone point me in the right direction\nI am new to programming, so not to complex, but I have a good\nhang of Python, just not an expert yet.\nThanks for any help","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":71,"Q_Id":20421965,"Users Score":0,"Answer":"Datastore has a limit on the size of objects stored there, thats why all examples and documentation say to use the blobstore or cloud storage. Do that.","Q_Score":0,"Tags":"python,google-app-engine,blob,google-cloud-datastore","A_Id":20424484,"CreationDate":"2013-12-06T10:47:00.000","Title":"How do I store files in googleappengine datastore","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I'm using a python script to run hourly scrapes of a website that publishes the most popular hashtags for a social media platform. They're to be stored in a database (MYSQL), with each row being a hashtag and then a column for each hour that it appears in the top 20, where the number of uses within that past hour is listed. \nSo, the amount of rows as well as columns will constantly increase, as new hashtags appear and ones that have previously appeared resurface into the top 20.\nIs there a best way to go about this?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":48,"Q_Id":20452796,"Users Score":2,"Answer":"Your design is poorly suited for a relational database such as MySQL.  The best way to go about it is to either redesign your storage layout to a form that a relational database works well with (eg. make each row  a (hashtag, hour) pair), or use something other than a relational database to store it.","Q_Score":0,"Tags":"python,mysql","A_Id":20452854,"CreationDate":"2013-12-08T11:17:00.000","Title":"Best way to handle a database with lots of dynamically added columns?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Problem\nI have a list of ~5000 locations with latitude and longitude coordinates called A, and a separate subset of this list called B. I want to find all locations from A that are within n miles of any of the locations in B.\nStructure\nAll of this data is stored in a mysql database, and requested via a python script.\nApproach\nMy current approach is to iterate through all locations in B, and request locations within n miles of each location, adding them to the list if they don't exist yet.\nThis works, but in the worst case, it takes a significant amount of time, and is quite inefficient. I feel like there has to be a better way, but I am at a loss as for how to do it.\nIdeas\n\nLoad all locations into a list in python, and calculate distances there. This would reduce the number of mysql queries, and likely speed up the operation. It would still be slow though.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":71,"Q_Id":20455129,"Users Score":1,"Answer":"Load B into a python list and for each calculate maxlat, minlat, maxlong, minlong that everything outside of the box is definitely outside of your radius, if your radius is in nautical miles and lat\/long in degrees.  You can then raise an SQL query for points meeting criteria of minlat < lat < maxlat and minlong < long < maxlong.  The resulting points can then be checked for exact distance and added to the in range list if they are in range.  \nI would suggest doing this in multiple processes.","Q_Score":0,"Tags":"python,mysql,latitude-longitude","A_Id":20455724,"CreationDate":"2013-12-08T15:29:00.000","Title":"Finding Locations with n Miles of Existing Locations","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I can convert date read from excel to a proper date using xldate_as_tuple function. Is there any function which can do the reverse i.e. convert proper date to float which is stored as date in excel ?","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1405,"Q_Id":20464887,"Users Score":0,"Answer":"Excel dates are represented as pywintypes.Time type objects. So in order to e.g. assign the current timestamp to a cell you do:\nworkbook.Worksheets(1).Cells(1,1).Value = pywintypes.Time(datetime.datetime.now())","Q_Score":2,"Tags":"python,excel,xlrd","A_Id":21302801,"CreationDate":"2013-12-09T06:57:00.000","Title":"How to convert current date to float which is stored in excel as date?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"how to do file uploading in turbogears 2.3.1? I am using CrudRestController and tgext.datahelpers and it is uploading the file in the sqlite3 database but in an unknown format. I want to make a copy of the uploaded file in the hard drive. My query is how to ensure that when user uploads a file, it is loaded both in the database and the hard drive.\n(Thank you for suggestions)","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":226,"Q_Id":20492587,"Users Score":0,"Answer":"tgext.datahelpers uploads files on disk inside the public\/attachments directory (this can be change with tg.config['attachments_path']).\nSo your file is already stored on disk, only the file metadata, like the URL, filename, thumbnail_url and so on are stored on database in JSON format","Q_Score":1,"Tags":"python-2.7,turbogears2","A_Id":20525832,"CreationDate":"2013-12-10T10:57:00.000","Title":"file upload turbogears 2.3.1","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I tend to start projects that are far beyond what I am capable of doing, bad habit or a good way to force myself to learn, I don't know. Anyway, this project uses a postgresql database, python and sqlalchemy. I am slowly learning everything from sql to sqlalchemy and python. I have started to figure out models and the declarative approach, but I am wondering: what is the easiest way to populate the database with data that needs to be there from the beginning, such as an admin user for my project? How is this usually done?\nEdit:\nPerhaps this question was worder in a bad way. What I wanted to know was the possible ways to insert initial data in my database, I tried using sqlalchemy and checking if every item existed or not, if not, insert it. This seemed tedious and can't be the way to go if there is a lot of initial data. I am a beginner at this and what better way to learn is there than to ask the people who do this regularly how they do it? Perhaps not a good fit for a question on stackoverflow, sorry.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":995,"Q_Id":20587888,"Users Score":0,"Answer":"You could use a schema change management tool like liquibase. Normally this is used to keep your database schema in source control, and apply patches to update your schema.\nYou can also use liquibase to load data from CSV files. So you could add a startup.csv file in liquibase that would be run the first time you run liquibase against your database. You can also have it run any time, and will merge data in the CSV with the database.","Q_Score":1,"Tags":"python,sql,postgresql,sqlalchemy","A_Id":20589295,"CreationDate":"2013-12-14T20:26:00.000","Title":"Sqlalchemy, python, easiest way to populate database with data","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am building the back-end for my web app; it would act as an API for the front-end and it will be written in Python (Flask, to be precise).\nAfter taking some decisions regarding design and implementation, I got to the database part. And I started thinking whether NoSQL data storage may be more appropriate for my project than traditional SQL databases. Following is a basic functionality description which should be handled by the database and then a list of pros and cons I could come up with regarding to which type of storage should I opt for. Finally some words about why I have considered RethinkDB over other NoSQL data storages.\nBasic functionality of the API\nThe API consists of only a few models: Artist, Song, Suggestion, User and UserArtists.\nI would like to be able to add a User with some associated data and link some Artists to it. I would like to add Songs to Artists on request, and also generate a Suggestion for a User, which will contain an Artist and a Song.\nMaybe one of the most important parts is that Artists will be periodically linked to Users (and also Artists can be removed from the system -- hence from Users too -- if they don't satisfy some criteria). Songs will also be dynamically added to Artists. All this means is that Users don't have a fixed set of Artists and nor do Artists have a fixed set of Songs -- they will be continuously updating.\nPros\nfor NoSQL:\n\nFlexible schema, since not every Artist will have a FacebookID or Song a SoundcloudID;\nWhile a JSON API, I believe I would benefit from the fact that records are stored as JSON;\nI believe the number of Songs, but especially Suggestions will raise quite a bit, hence NoSQL will do a better job here;\n\nfor SQL:\n\nIt's fixed schema may come in handy with relations between models;\nFlask has support for SQLAlchemy which is very helpful in defining models;\n\nCons\nfor NoSQL:\n\nRelations are harder to implement and updating models transaction-like involves a bit of code;\nFlask doesn't have any wrapper or module to ease things, hence I will need to implement some kind of wrapper to help me make the code more readable while doing database operations;\nI don't have any certainty on how should I store my records, especially UserArtists\n\nfor SQL:\n\nOperations are bulky, I have to define schemas, check whether columns have defaults, assign defaults, validate data, begin\/commit transactions -- I believe it's too much of a hassle for something simple like an API;\n\nWhy RethinkDB?\nI've considered RehinkDB for a possible implementation of NoSQL for my API because of the following:\n\nIt looks simpler and more lightweight than other solutions;\nIt has native Python support which is a big plus;\nIt implements table joins and other things which could come in handy in my API, which has some relations between models;\nIt is rather new, and I see a lot of implication and love from the community. There's also the will to continuously add new things that leverage database interaction.\n\nAll these being considered, I would be glad to hear any advice on whether NoSQL or SQL is more appropiate for my needs, as well as any other pro\/con on the two, and of course, some corrections on things I haven't stated properly.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":2835,"Q_Id":20597590,"Users Score":14,"Answer":"I'm working at RethinkDB, but that's my unbiased answer as a web developer (at least as unbiased as I can).\n\nFlexible schema are nice from a developer point of view (and in your case). Like you said, with something like PostgreSQL you would have to format all the data you pull from third parties (SoundCloud, Facebook etc.). And while it's not something really hard to do, it's not something enjoyable.\nBeing able to join tables, is for me the natural way of doing things (like for user\/userArtist\/artist). While you could have a structure where a user would contain artists, it is going to be unpleasant to use when you will need to retrieve artists and for each of them a list of users.\n\nThe first point is something common in NoSQL databases, while JOIN operations are more a SQL databases thing.\nYou can see RethinkDB as something providing the best of each world.\nI believe that developing with RethinkDB is easy, fast and enjoyable, and that's what I am looking for as a web developer.\nThere is however one thing that you may need and that RethinkDB does not deliver, which is transactions. If you need atomic updates on multiple tables (or documents - like if you have to transfer money between users), you are definitively better with something like PostgreSQL. If you just need updates on multiple tables, RethinkDB can handle that.\nAnd like you said, while RethinkDB is new, the community is amazing, and we - at RethinkDB - care a lot about our users.\nIf you have more questions, I would be happy to answer them : )","Q_Score":11,"Tags":"python,sql,database,nosql,rethinkdb","A_Id":20600546,"CreationDate":"2013-12-15T17:37:00.000","Title":"How suitable is opting for RethinkDB instead of traditional SQL for a JSON API?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am working with an Oracle database with millions of rows and 100+ columns. I am attempting to store this data in an HDF5 file using pytables with certain columns indexed. I will be reading subsets of these data in a pandas DataFrame and performing computations.\nI have attempted the following:\nDownload the the table, using a utility into a csv file, read the csv file chunk by chunk using pandas and append to HDF5 table using pandas.HDFStore. I created a dtype definition and provided the maximum string sizes.\nHowever, now when I am trying to download data directly from Oracle DB and post it to HDF5 file via pandas.HDFStore, I run into some problems.\npandas.io.sql.read_frame does not support chunked reading. I don't have enough RAM to be able to download the entire data to memory first.\nIf I try to use cursor.fecthmany() with a fixed number of records, the read operation takes ages at the DB table is not indexed and I have to read records falling under a date range. I am using DataFrame(cursor.fetchmany(), columns = ['a','b','c'], dtype=my_dtype) \nhowever, the created DataFrame always infers the dtype rather than enforce the dtype I have provided (unlike read_csv which adheres to the dtype I provide). Hence, when I append this DataFrame to an already existing HDFDatastore, there is a type mismatch for e.g. a float64 will maybe interpreted as int64 in one chunk.\nAppreciate if you guys could offer your thoughts and point me in the right direction.","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":5171,"Q_Id":20618523,"Users Score":0,"Answer":"Okay, so I don't have much experience with oracle databases, but here's some thoughts:\nYour access time for any particular records from oracle are slow, because of a lack of indexing, and the fact you want data in timestamp order. \nFirstly, you can't enable indexing for the database?\nIf you can't manipulate the database, you can presumably request a found set that only includes the ordered unique ids for each row?\nYou could potentially store this data as a single array of unique ids, and you should be able to fit into memory. If you allow 4k for every unique key (conservative estimate, includes overhead etc), and you don't keep the timestamps, so it's just an array of integers, it might use up about 1.1GB of RAM for 3 million records. That's not a whole heap, and presumably you only want a small window of active data, or perhaps you are processing row by row?\nMake a generator function to do all of this. That way, once you complete iteration it should free up the memory, without having to del anything, and it also makes your code easier to follow and avoids bloating the actual important logic of your calculation loop.\nIf you can't store it all in memory, or for some other reason this doesn't work, then the best thing you can do, is work out how much you can store in memory. You can potentially split the job into multiple requests, and use multithreading to send a request once the last one has finished, while you process the data into your new file. It shouldn't use up memory, until you ask for the data to be returned. Try and work out if the delay is the request being fulfilled, or the data being downloaded.\nFrom the sounds of it, you might be abstracting the database, and letting pandas make the requests. It might be worth looking at how it's limiting the results. You should be able to make the request for all the data, but only load the results one row at a time from the database server.","Q_Score":12,"Tags":"python,pandas,hdf5,pytables","A_Id":29225626,"CreationDate":"2013-12-16T18:50:00.000","Title":"Reading a large table with millions of rows from Oracle and writing to HDF5","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I dont even know if this is possible. But if it is, can someone give me the broadstrokes on how I can use a Python script to populate a Google spreadsheet?\nI want to scrape data from a web site and dump it into a google spreadsheet. I can imagine what the Python looks like (scrapy, etc). But does the language support writing to Google Drive? Can I kick off the script within the spreadsheet itself or would it have to run outside of it?\nIdeal scenario would be to open a google spreadsheet, click on a button, Python script executes and data is filled in said spreadsheet.","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":3149,"Q_Id":20693168,"Users Score":0,"Answer":"Yes, it is possible and this is how I am personally doing it so.\nsearch for \"doGet\" and \"doPost(e)","Q_Score":0,"Tags":"python,google-sheets","A_Id":50629830,"CreationDate":"2013-12-19T22:45:00.000","Title":"Is this possible - Python script to fill a Google spreadsheet?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"i have deployed a simple Django application on AWS. The database i use is MySQL. Most parts of this application runs well. But there happens to be a problem when i submitted a form and store data from the form into a model. The error page presents Data truncated for column 'temp' at row 1. temp is a ChoiceField like this: temp = forms.ChoiceField(label=\"temperature\", choices=TEMP), in the model file the temp is a CharField like this temp = models.CharField(max_length=2, choices=TEMP). The error happens at .save(). How can i fix this problem? Any advice and help is appreciated. BTW, as what i have searched, the truncation problem happens because of data type to be stored in database. But i still cannot figure out how to modify my code.","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":2106,"Q_Id":20712174,"Users Score":1,"Answer":"Your column is only 2 chars wide, but you are trying to store the strings 'HIGH', 'MEDIUM', 'LOW' from your TEMP choices (the first value of each tuple is saved in the database). Increase max_length or choose different values for choices, e.g. TEMP = ( ('H', 'High'), ('M', 'Medium'), ('L', 'Low'), ). \nIt worked fine in SQLite because SQLite simply ignores the max_length attribute (and other things).","Q_Score":0,"Tags":"python,mysql,database,django,amazon-ec2","A_Id":20712349,"CreationDate":"2013-12-20T21:24:00.000","Title":"Data truncated for column 'temp' at row 1","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm started enhancing an application which has developed in Python. Zope server has been used to deploy the application.\nIn many modules DB connection has established and used for DB transaction, and which has not used any connection pooling mechanism. Considering the volume of users it is vulnerable to have DB connections established for every request and it is a bad design.\n\nNow In order to have connection pooling, what should I do? My application\n  uses Python 2.4,Zope 2.11.4 and MySQL 5.5.\n\nIs Zope provides any way to achieve it, like configure the DB in external file and inside the Python code referring the connection which Zope takes care of utilizing from connection pool? Or Do I need to write in a Python code in such a way that independent of the server(Zope or other) provided MySQL module for python","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":309,"Q_Id":20798818,"Users Score":0,"Answer":"I guess you've advanced with your problem, but this is not a reason not to comment.\n1) Long-term answer: seriously consider building a path to migrating to ZODB instead of mysql. ZODB is integrated with Zope and is way more efficient than mysql for storing Zope data. You can't do it at once, but may be you can identify part of the data that can be migrated to ZODB first, and then do it by \"clusters of data\".\n2) short-term answer: I don't know what library you're using to connect to mysql (there aren't many of them), let's say it's python-mysqldb, and the function to Connect to the database is Connect. You Can write your own MySqlDB module, and put it before the system MySqlDB in the sys.path (manipulating the sys.path of your zope application if necessary), so your module is called instead of the system MySqlDB one. In your module, you write a Connect function that encapsulates your pooling logic and proxy everything else to the original (system) MySqlDB module.\nHope I've been clear for you or everyone else having the same problem.","Q_Score":1,"Tags":"python,mysql,connection-pooling,mysql-python,zope","A_Id":21954872,"CreationDate":"2013-12-27T10:15:00.000","Title":"How to configure DB connection pooling in Python Zope server","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am trying to import sqlalchemy.databases.sqlite.DateTimeMixIn. I get ImportError: No module named sqlite. SQLAlchemy 0.8.4 is installed. If I do import sqlite I get the same error.","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":79,"Q_Id":20834740,"Users Score":1,"Answer":"Sounds like the python binary you are using wasn't compiled with the sqlite module.  If you are compiling from source, make sure you have the sqlite headers available.","Q_Score":0,"Tags":"python,sqlite,sqlalchemy","A_Id":20835718,"CreationDate":"2013-12-30T06:52:00.000","Title":"Importing SQLAlchemy DateTimeMixin raises ImportErrror","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Is there any way to check whether a row in a table has been modified or not in Cassandra.\nI don't want to compare the date before and after updating row in table.\nAfter Update operation I need to verify the query executed properly or not using python scripts. I am using Cassandra Driver for python.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":167,"Q_Id":20855659,"Users Score":0,"Answer":"If you want to verify that an update happened as planned, execute a SELECT against the updated row.","Q_Score":0,"Tags":"python,cassandra","A_Id":20928821,"CreationDate":"2013-12-31T10:15:00.000","Title":"Cassandra row update check in a table","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I want to publish an Android application that I have developed but have a minor concern.\nThe application will load with a database file (or sqlite3 file). If updates arise in the future and these updates are only targeting the application's functionality without the database structure, I wish to allow users to keep their saved entries in their sqlite3 files.\nSo what is the best practice to send updates? Compile the apk files with the new updated code only and without the database files? Or is there any other suggestion?\nPS: I am not working with Java and Eclipse, but with python for Android and the Kivy platform which is an amazing new way for developing Android applications.","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":487,"Q_Id":20856465,"Users Score":0,"Answer":"if you're using local sqlite then you have to embed the database file within the app as failure to do so it means there's no database, in case for updates database have version numbers where as it can not upgrade the database provided the version number is the same as the previous app updates","Q_Score":4,"Tags":"android,python-2.7,sqlite,apk,kivy","A_Id":20856571,"CreationDate":"2013-12-31T11:14:00.000","Title":"Update apk file on Google Play","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":1,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I want to publish an Android application that I have developed but have a minor concern.\nThe application will load with a database file (or sqlite3 file). If updates arise in the future and these updates are only targeting the application's functionality without the database structure, I wish to allow users to keep their saved entries in their sqlite3 files.\nSo what is the best practice to send updates? Compile the apk files with the new updated code only and without the database files? Or is there any other suggestion?\nPS: I am not working with Java and Eclipse, but with python for Android and the Kivy platform which is an amazing new way for developing Android applications.","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":487,"Q_Id":20856465,"Users Score":0,"Answer":"I had the same issue when I started my app but since kivy has no solution for this I tried to create a directory outside my app directory in android with a simple os.mkdir('..\/##') and I put all the files there. Hope this helps!","Q_Score":4,"Tags":"android,python-2.7,sqlite,apk,kivy","A_Id":46767741,"CreationDate":"2013-12-31T11:14:00.000","Title":"Update apk file on Google Play","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":1,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a Django app that has several database backends - all connected to different instances of Postgresql database. One of them is not guaranteed to be always online. It even can be offline when application starts up.\nCan I somehow configure Django to use lazy connections? I would like to:\n\nTry querying\nreturn \"sorry, try again later\" if database is offline\nor return the results if database is online\n\nIs this possible?","AnswerCount":1,"Available Count":1,"Score":0.3799489623,"is_accepted":false,"ViewCount":380,"Q_Id":20878709,"Users Score":2,"Answer":"The original confusion is that Django tries to connect to its databases on startup. This is actually not true. Django does not connect to database, until some app tries to access the database.\nSince my web application uses auth and site apps, it looks like it tries to connect on startup. But its not tied to startup, its tied to the fact that those app access the database \"early\".\nIf one defines second database backend (non-default), then Django will not try connecting to it unless application tries to query it.\nSo the solution was very trivial - originally I had one database that hosted both auth\/site data and also \"real\" data that I've exposed to users. I wanted to make \"real\" database connection to be volatile. So I've defined separate psql backend for it and switched default backend to sqlite. \nNow when trying to access \"real\" database through Query, I can easily wrap it with try\/except and handle \"Sorry, try again later\" over to the user.","Q_Score":1,"Tags":"python,django,django-models","A_Id":21235393,"CreationDate":"2014-01-02T08:01:00.000","Title":"Lazy psql connection with Django","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"As the title suggests, I am using the s3cmd tool to upload\/download files on Amazon.\nHowever I have to use Windows Server and bring in some sort of progress reporting. \nThe problem is that on windows, s3cmd gives me the following error:\nERROR: Option --progress is not yet supported on MS Windows platform. Assuming -\n-no-progress.\nNow, I need this --progress option.\nAre there any workarounds for that? Or maybe some other tool?\nThanks.","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":701,"Q_Id":21017853,"Users Score":2,"Answer":"OK, I have found a decent workaround to that:\nJust navigate to C:\\Python27\\Scripts\\s3cmd and comment out lines 1837-1845.\nThis way we can essentially skip a windows check and print progress on the cmd.\nHowever, since it works normally, I have no clue why the authors put it there in the first place.\nCheers.","Q_Score":1,"Tags":"python,windows,progress-bar,progress,s3cmd","A_Id":21165278,"CreationDate":"2014-01-09T10:38:00.000","Title":"s3cmd tool on Windows server with progress support","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":1,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am trying to install psycopg2 on Mac OS X Mavericks but it doesn't see any pg_config file.\nPostgres was installed via Postgres.app .\nI found pg_config in \/Applications\/Postgres.app\/Contents\/MacOS\/bin\/ and put it to setup.cfg but still can't install psycopg2.\nWhat might be wrong?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":916,"Q_Id":21033198,"Users Score":0,"Answer":"I had the same problem when I tried to install psycopg2 via Pycharm and using Postgres93.app. The installer (when running in Pycharm) insisted it could not find the pg_config file despite the fact that pg_config is on my path and I could run pg_config and psql successfully in Terminal. For me the solution was to install a clean version of python with homebrew. Navigate to the homebrew installation of Python and run pip in the terminal (rather than with Pycharm). It seems pip running in Pycharm did not see the postgres installation on my PATH, but running pip directly in a terminal resolved the problem.","Q_Score":2,"Tags":"python,macos,postgresql,psycopg2","A_Id":21414139,"CreationDate":"2014-01-09T23:15:00.000","Title":"Can't install psycopg2 on Maverick","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":0},{"Question":"Recently i m working on web2py postgresql i made few changes in my table added new fields with fake_migration_all = true it does updated my .table file but the two new added fields were not able to be altered in postgres database table and i also tried fake_migration_all = false and also deleted mu .table file but still it didnt help to alter my table does able two add fields in datatable\nAny better solution available so that i should not drop my data table and fields should also be altered\/added in my table so my data shouldn't be loast","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":535,"Q_Id":21046136,"Users Score":0,"Answer":"fake_migrate_all doesn't do any actual migration (hence the \"fake\") -- it just makes sure the metadata in the .table files matches the current set of table definitions (and therefore the actual database, assuming the table definitions in fact match the database).\nIf you want to do an actual migration of the database, then you need to make sure you do not have migrate_enabled=False in the call to DAL(), nor migrate=False in the relevant db.define_table() calls. Unless you explicitly set those to false, migrations are enabled by default.\nAlways a good idea to back up your database before doing a migration.","Q_Score":0,"Tags":"python,web2py","A_Id":21050586,"CreationDate":"2014-01-10T13:55:00.000","Title":"Web2py postgreSQL database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Forgive my ignorance as I am new to oursql.  I'm simply trying to pass a parameter to a statement:\ncursor.execute(\"select blah from blah_table where blah_field = ?\", blah_variable)\nthis treated whatever is inside the blah_variable as a char array so if I pass \"hello\" it will throw a ProgrammingError telling me that 1 parameter was expected but 5 was given.\nI've tried looking through the docs but their examples are not using variables.  Thanks!","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":233,"Q_Id":21053472,"Users Score":1,"Answer":"IT is expecting a sequence of parameters. Use:\n[blah_variable]","Q_Score":0,"Tags":"python,parameters,oursql","A_Id":21053569,"CreationDate":"2014-01-10T20:06:00.000","Title":"Python oursql treating a string variable as a char array","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am deploying my flask app to EC2, however i get the error in my error.log file once i visit the link of my app.\nMy extensions are present in the site-packages of my flask environment and not the \"usr\" folder of the server, however it tries to search usr folder to find the hook\n\nFile \"\/usr\/local\/lib\/python2.7\/dist-packages\/flask\/exthook.py\", line 87, in load_module\n\nIt is located in \n\n\/var\/www\/sample\/flask\/lib\/python2.7\/site-packages\n\nHow to get over this issue?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":2246,"Q_Id":21107967,"Users Score":0,"Answer":"You should be building your python apps in a virtualenv rather than using the system's installation of python.  Try creating a virtualenv for your app and installing all of the extensions in there.","Q_Score":0,"Tags":"python,deployment,amazon-ec2,flask,flask-sqlalchemy","A_Id":21124613,"CreationDate":"2014-01-14T07:23:00.000","Title":"ImportError: No module named flask.ext.sqlalchemy","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"What I am using: PostgreSQL and Python. I am using Python to access PostgreSQL\nWhat I need: Receive a automatic notification, on Python, if anyone records something on a specific table on database.\nI think that it is possible using a routine that go to that table, over some interval, and check changes. But it requires a loop and I would like something like an a assynchronous way.\nIs it possible?","AnswerCount":3,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":17343,"Q_Id":21117431,"Users Score":17,"Answer":"donmage is quite right - LISTEN and NOTIFY are what you want. You'll still need a polling loop, but it's very lightweight, and won't cause detectable server load.\nIf you want psycopg2 to trigger callbacks at any time in your program, you can do this by spawning a thread and having that thread execute the polling loop.  Check to see whether psycopg2 enforces thread-safe connection access; if it doesn't, you'll need to do your own locking so that your polling loop only runs when the connection is idle, and no other queries interrupt a polling cycle.  Or you can just use a second connection for your event polling.\nEither way, when the background thread that's polling for notify events receives one, it can invoke a Python callback function supplied by your main program, which might modify data structures \/ variables shared by the rest of the program. Beware, if you do this, that it can quickly become a nightmare to maintain.\nIf you take that approach, I strongly suggest using the multithreading \/ multiprocessing modules. They will make your life massively easier, providing simple ways to exchange data between threads, and limiting modifications made by the listening thread to simple and well-controlled locations.\nIf using threads instead of processes, it is important to understand that in cPython (i.e. \"normal Python\") you can't have a true callback interrupt, because only one thread may be executing in cPython at once. Read about the \"global interpreter lock\" (GIL) to understand more about this. Because of this limitation (and the easier, safer nature of shared-nothing by default concurrency) I often prefer multiprocessing to multithreading.","Q_Score":21,"Tags":"python,postgresql,events,triggers,listener","A_Id":21128034,"CreationDate":"2014-01-14T15:35:00.000","Title":"How to receive automatic notifications about changes in tables?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"We have a database that contains personally-identifying information (PII) that needs to be encrypted. \nFrom the Python side, I can use PyCrypto to encrypt data using AES-256 and a variable salt; this results in a Base64 encoded string.\nFrom the PostgreSQL side, I can use the PgCrypto functions to encrypt data in the same way, but this results in a bytea value.\nFor the life of me, I can't find a way to convert between these two, or to make a comparison between the two so that I can do a query on the encrypted data. Any suggestions\/ideas?\nNote: yes, I realize that I could do all the encryption\/decryption on the database side, but my goal is to ensure that any data transmitted between the application and the database still does not contain any of the PII, as it could, in theory, be vulnerable to interception, or visible via logging.","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":2355,"Q_Id":21122847,"Users Score":3,"Answer":"Imagine you have a Social Security Number field in your table. Users must be able to query for a particular SSN when needed. The SSN, obviously, needs to be encrypted. I can encrypt it from the Python side and save it to the database, but then in order for it to be searchable, I would have to use the same salt for every record so that I can incorporate the encrypted value as part of my WHERE clause, and that just leaves us vulnerable. I can encrypt\/decrypt on the database side, but in that case, I'm sending the SSN in plain-text whenever I'm querying, which is also bad.\n\nThe usual solution to this kind of issue is to store a partial value, hashed unsalted or with a fixed salt, alongside the randomly salted full value. You index the hashed partial value and search on that. You'll get false-positive matches, but still significantly benefit from DB-side indexed searching. You can fetch all the matches and, application-side, discard the false positives.\nQuerying encrypted data is all about compromises between security and performance. There's no magic answer that'll let you send a hashed value to the server and have it compare it to a bunch of randomly salted and hashed values for a match. In fact, that's exactly why we salt our hashes - to prevent that from working, because that's also pretty much what an attacker does when trying to brute-force.\nSo. Compromise. Either live with sending the SSNs as plaintext (over SSL) for comparison to salted & hashed stored values, knowing that it still greatly reduces exposure because the whole lot can't be dumped at once. Or index a partial value and search on that.\nDo be aware that another problem with sending values unhashed is that they can appear in the server error logs. Even if you don't have log_statement = all, they may still appear if there's an error, like query cancellation or a deadlock break. Sending the values as query parameters reduces the number of places they can appear in the logs, but is far from foolproof. So if you send values in the clear you've got to treat your logs as security critical. Fun!","Q_Score":1,"Tags":"python,postgresql,encryption","A_Id":21128178,"CreationDate":"2014-01-14T20:01:00.000","Title":"Encryption using Python and PostgreSQL","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have several million rows in a Sqlite database that need 5 columns updated. Each row\/column value is different, so I have to update each row individually.\nBecause of the way I'm looping through JSON from an external API, for each row, I have the option of either:\n1) do 5 UPDATE operations, one for value. \n2) build a temporary dict in python, then unpack it into a single UPDATE operation that updates all 5 columns at once. \nBasically I'm trading off Python time (slower language, but in memory) for SQLite time (faster language, but on disk).\nWhich is faster?","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":71,"Q_Id":21150012,"Users Score":1,"Answer":"Building a dict doesn't really take that much memory. It's much more efficient since you'll only need to do one operation - and let SQLite handle it. Well, python is going to clean the dict anyway, so this is definitely the way to go. \nBut as @JoranBeasley mentioned in the comment.. You never know until you try. \nHope this helps!","Q_Score":1,"Tags":"python,python-2.7,sqlite","A_Id":21150081,"CreationDate":"2014-01-15T22:55:00.000","Title":"For a single Sqlite row, faster to do 5 UPDATEs or build a python dict, then 1 Update?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am using Oracle database and in a certain column I need to insert Strings, which in some cases are larger than 4000 symbols (Oracle 11g limits Varchar2 size to 4000). We are required to use Oracle 11g, and I know about the 12g extended mode. I would not like to use the CLOB datatype for performance considerations. The solution that I have in mind is to split the column and write a custom SQLAlchemy datatype that writes the data to the second column in case of string larger than 4000.\nSo, my questions are:\n\nAre we going to gain any significant performance boost from that (rather than using Clob)?\nHow should that SQLAlchemy be implemented? Currently we are using types.TypeDecorator for custom types, but in this case we need to read\/write in two fields.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":820,"Q_Id":21237645,"Users Score":1,"Answer":"CLOB or NCLOB would be the best options. Avoid splitting data into columns. What would happen when you have data larger than 2 columns - it will fail again. It also makes it maintenance nightmare. I've seen people split data into rows in some databases just because the database would not support larger character datatypes (old Sybase versions). However, if your database has a datatype built for this purpose by all means use it.","Q_Score":0,"Tags":"python,oracle,oracle11g,sqlalchemy","A_Id":21238505,"CreationDate":"2014-01-20T15:20:00.000","Title":"SQLAlchemy type containing strings larger than 4000 on Oracle using Varchar2","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a serious problem, I don't now how to solve it.\nI have a Win 7 64bit laptop, with MS Office 2007 installed (32 bits).\nI installed Anaconda 64bits, BUT I am trying to connect to a MS Access MDB file with the ACE drives and I got an error that there is no driver installed.\nDue to MS Office 2007, I was forced to install ACE drivers 32 bits.\nAny help?\nThe same code runs perfect under Win XP, with exactly the same installed: Anaconda, ACE drivers and MS Office 2007.\nIt can be a problem mixin 32bits and 64 bits?","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":217,"Q_Id":21296441,"Users Score":1,"Answer":"I finally got it!\nYes, the problem was mixing 32 and 64 bits.\nI solved the problem installing the Microsoft ACE Drivers 64bits on a MS-DOS console, writting:\nAccessDatabaseEngine_x64.exe \/passive\nAnd everything works!","Q_Score":1,"Tags":"python,ms-access,ms-office,anaconda","A_Id":21333377,"CreationDate":"2014-01-22T23:39:00.000","Title":"Python on Win 7 64bits error MS Access","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a big problem here with python, openpyxl and Excel files. My objective is to write some calculated data to a preconfigured template in Excel. I load this template and write the data on it. There are two problems:\n\nI'm talking about writing Excel books with more than 2 millions of cells, divided into several sheets.\nI do this successfully, but the waiting time is unthinkable.\n\nI don't know other way to solve this problem. Maybe openpyxl is not the solution. I have tried to write in xlsb, but I think openpyxl does not support this format. I have also tried with optimized writer and reader, but the problem comes when I save, due to the big data. However, the output file size is 10 MB, at most. I'm very stuck with this. Do you know if there is another way to do this?\nThanks in advance.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":5110,"Q_Id":21328884,"Users Score":4,"Answer":"The file size isn't really the issue when it comes to memory use but the number of cells in memory. Your use case really will push openpyxl to the limits at the moment which is currently designed to support either optimised reading or optimised writing but not both at the same time. One thing you might try would be to read in openpyxl with use_iterators=True this will give you a generator that you can call from xlsxwriter which should be able to write a new file for you. xlsxwriter is currently significantly faster than openpyxl when creating files. The solution isn't perfect but it might work for you.","Q_Score":5,"Tags":"python,excel,openpyxl","A_Id":21352070,"CreationDate":"2014-01-24T09:25:00.000","Title":"openpyxl: writing large excel files with python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"is it possible to use custom _id fields with Django and MongoEngine?\nThe problem is, if I try to save a string to the _id field it throws an Invalid ObjectId eror. What I want to do is using my own Id's. This never was a problem without using Django because I caught the DuplicateKeyError on creation if a given id was already existing (which was even necessary to tell the program, that this ID is already taken) \nNow it seems as if Django\/MongoEngine won't even let me create a custom _id field :-\/\nIs there any way to work arround this without creating a second field for the ID and let the _id field create itself?\nGreetings Codehai","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":2413,"Q_Id":21370889,"Users Score":6,"Answer":"You can set the parameter primary_key=True on a Field. This will make the target Field your _id Field.","Q_Score":0,"Tags":"python,django,mongodb,mongoengine","A_Id":21498341,"CreationDate":"2014-01-26T23:51:00.000","Title":"custom _id fields Django MongoDB MongoEngine","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have python 2.7 32 bit running on a Windows 8.1 64 bit machine.  \nI have Access 2013 and a .accdb file that I'm trying to access from python and pyodbc.\nI can create a 64 bit DSN in the 64 bit ODBC manager.  However, when I try to connect to it from python, I get the error: \n\nError: (u'IM002', u'[IM002] [Microsoft][ODBC Driver Manager] Data source name not found and no default driver specified')\n\nPresumably, python is only looking for 32-bit DSNs and doesn't find the 64-bit one that I've created.\nWhen I try to create a 32-bit DSN within the 32-bit ODBC manager, there is no driver for a accdb file (just .mdb).\nI think I need a 32 bit ODBC driver for Access 2013 files (.accdb), but haven't been able to find one.\nIs it possible to do what I'm trying to do? -- 32bit python access a Access 2013 .accdb file?","AnswerCount":3,"Available Count":1,"Score":0.1325487884,"is_accepted":false,"ViewCount":10567,"Q_Id":21393558,"Users Score":2,"Answer":"Trial and error showed that installing the \"Access Database Engine\" 2007 seemed to create 32-bit ODBC source for Access accdb files.","Q_Score":4,"Tags":"python,ms-access,odbc","A_Id":21393854,"CreationDate":"2014-01-27T23:03:00.000","Title":"32 bit pyodbc reading 64 bit access (accdb)","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I would like to integrate a Python application and PHP application for data access. I have a Python app and it stores data in its application, now i want to access the data from python database to php application database. For PHP-Python integration which methods are used?\nThanks","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":561,"Q_Id":21399625,"Users Score":0,"Answer":"The easiest way to accomplish this is to build a private API for your PHP app to access your Python app. For example, if using Django, make a page that takes several parameters and returns JSON-encoded information. Load that into your PHP page, use json_decode, and you're all set.","Q_Score":0,"Tags":"php,python,web-services,integration","A_Id":21410252,"CreationDate":"2014-01-28T07:43:00.000","Title":"Integration of PHP-Python applications","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm using Flask-Babel for translating string.\nIn some templates I'm reading the strings from the database(postgresql). \nHow can I translate the strings from the database using Flask-Babel?","AnswerCount":2,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":1789,"Q_Id":21497489,"Users Score":2,"Answer":"It's not possible to use Babel in database translations, as database content is dynamic and babel translations are static (they didn't change). \nIf you read the strings from the database you must save the translations on the database. You can create a translation table, something like (locale, source, destination), and get the translated values with a query.","Q_Score":9,"Tags":"python,flask,python-babel,flask-babel","A_Id":22099629,"CreationDate":"2014-02-01T11:31:00.000","Title":"translating strings from database flask-babel","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm having trouble in establishing an ideal setup where I can distinguish between production and test environment for my django app. \nI'm using a postgresql database that stores a relative file path to a s3 bucket after I upload an image. Am I supposed to make a production copy of all the files in the s3 bucket and connect my current development code to this static directory to do testing? I certainly don't want to connect to production ... What's best practice in this situation?\nAlso I may be doing things wrong here by having the file path in a postgresql database. Would it be more ideal to have some foreign key to a mongodb table which then holds the file path for the file path in aws s3?\nAnother best practice question is how should the file path should be organized? Should I just organize the file path like the following:\n~somebucket\/{userName}\/{date}\/{fileNameName}\nOR\n~somebucket\/{userName}\/{fileName}\nOR\n~somebucket\/{fileName}\nOR\n~somebucket\/{date}\/{userName}\/{fileNameName}\nOR\n~somebucket\/{fileName} = u1234d20140101funnypic.png ??\nThis is really confusing for me on how to build an ideal way to store static files for development and production. Any better recommendations would be greatly appreciated. \nThanks for your time :)","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":41,"Q_Id":21518268,"Users Score":1,"Answer":"Its good to have different settings for production and dev. \nSo you can just create a settings folder and have settings may  be prod.py and dev.py. this will let you use diff apps for eg: you actually don't need debug tool bar on prod. \nAnd regarding the file, I feel you dont have to worry about the structure as such, you can always refer to Etag and get the file (md5 hash of the object)","Q_Score":0,"Tags":"python,django,mongodb,postgresql,amazon-s3","A_Id":21518701,"CreationDate":"2014-02-03T00:53:00.000","Title":"How should I set up my dev enviornment for a django app so that I can pull on static s3 files?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a Model class which is part of my self-crafted ORM. It has all kind of methods like save(), create() and so on. Now, the thing is that all these methods require a connection object to act properly. And I have no clue on what's the best approach to feed a Model object with a connection object.\nWhat I though of so far:\n\nprovide a connection object in a Model's __init__(); this will work, by setting an instance variable and use it throughout the methods, but it will kind of break the API; users shouldn't always feed a connection object when they create a Model object;\ncreate the connection object separately, store it somewhere (where?) and on Model's __init__() get the connection from where it has been stored and put it in an instance variable (this is what I thought to be the best approach, but have no idea of the best spot to store that connection object);\ncreate a connection pool which will be fed with the connection object, then on Model's __init__() fetch the connection from the connection pool (how do I know which connection to fetch from the pool?).\n\nIf there are any other approached, please do tell. Also, I would like to know which is the proper way to this.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":76,"Q_Id":21650889,"Users Score":1,"Answer":"Here's how I would do:\n\nUse a connection pool with a queue interface. You don't have to choose a connection object, you just pick the next on the line. This can be done whenever you need transaction, and put back afterwards.\nUnless you have some very specific needs, I would use a Singleton class for the database connection. No need to pass parameters on the constructor every time.\nFor testing, you just put a mocked database connection on the Singleton class.\n\nEdit:\nAbout the connection pool questions (I could be wrong here, but it would be my first try):\n\nKeep all connections open. Pop when you need, put when you don't need it anymore, just like a regular queue. This queue could be exposed from the Singleton.\nYou start with a fixed, default number of connections (like 20). You could override the pop method, so when the queue is empty you block (wait for another to free if the program is multi-threaded) or create a new connection on the fly.\nDestroying connections is more subtle. You need to keep track of how many connections the program is using, and how likely it is you have too many connections. Take care, because destroying a connection that will be needed later slows the program down. In the end, it's a n heuristic problem that changes the performance characteristics.","Q_Score":0,"Tags":"python,database-connection","A_Id":21651170,"CreationDate":"2014-02-08T19:39:00.000","Title":"Getting connection object in generic model class","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm creating a Google App Engine application (python) and I'm learning about the general framework. I've been looking at the tutorial and documentation for the NDB datastore, and I'm having some difficulty wrapping my head around the concepts. I have a large background with SQL databases and I've never worked with any other type of data storage system, so I'm thinking that's where I'm running into trouble.\nMy current understanding is this: The NDB datastore is a collection of entities (analogous to DB records) that have properties (analogous to DB fields\/columns). Entities are created using a Model (analogous to a DB schema). Every entity has a key that is generated for it when it is stored. This is where I run into trouble because these keys do not seem to have an analogy to anything in SQL DB concepts. They seem similar to primary keys for tables, but those are more tightly bound to records, and in fact are fields themselves. These NDB keys are not properties of entities, but are considered separate objects from entities. If an entity is stored in the datastore, you can retrieve that entity using its key. \nOne of my big questions is where do you get the keys for this? Some of the documentation I saw showed examples in which keys were simply created. I don't understand this. It seemed that when entities are stored, the put() method returns a key that can be used later. So how can you just create keys and define ids if the original keys are generated by the datastore?\nAnother thing that I seem to be struggling with is the concept of ancestry with keys. You can define parent keys of whatever kind you want. Is there a predefined schema for this? For example, if I had a model subclass called 'Person', and I created a key of kind 'Person', can I use that key as a parent of any other type? Like if I wanted a 'Shoe' key to be a child of a 'Person' key, could I also then declare a 'Car' key to be a child of that same 'Person' key? Or will I be unable to after adding the 'Shoe' key?\nI'd really just like a simple explanation of the NDB datastore and its API for someone coming from a primarily SQL background.","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":7423,"Q_Id":21655862,"Users Score":13,"Answer":"I think you've overcomplicating things in your mind. When you create an entity, you can either give it a named key that you've chosen yourself, or leave that out and let the datastore choose a numeric ID. Either way, when you call put, the datastore will return the key, which is stored in the form [<entity_kind>, <id_or_name>] (actually this also includes the application ID and any namespace, but I'll leave that out for clarity).\nYou can make entities members of an entity group by giving them an ancestor. That ancestor doesn't actually have to refer to an existing entity, although it usually does. All that happens with an ancestor is that the entity's key includes the key of the ancestor: so it now looks like [<parent_entity_kind>, <parent_id_or_name>, <entity_kind>, <id_or_name>]. You can now only get the entity by including its parent key. So, in your example, the Shoe entity could be a child of the Person, whether or not that Person has previously been created: it's the child that knows about the ancestor, not the other way round.\n(Note that that ancestry path can be extended arbitrarily: the child entity can itself be an ancestor, and so on. In this case, the group is determined by the entity at the top of the tree.)\nSaving entities as part of a group has advantages in terms of consistency, in that a query inside an entity group is always guaranteed to be fully consistent, whereas outside the query is only eventually consistent. However, there are also disadvantages, in that the write rate of an entity group is limited to 1 per second for the whole group.","Q_Score":17,"Tags":"python,google-app-engine,app-engine-ndb","A_Id":21658988,"CreationDate":"2014-02-09T05:53:00.000","Title":"Simple explanation of Google App Engine NDB Datastore","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I am just beginning learning Django and working through the tutorial, so sorry if this is very obvious. \nI have already a set of Python scripts whose ultimate result is an sqlite3 db that gets constantly updated; is Django the right tool for turning this sqlite db something like a pretty HTML table for a website? \nI can see that Django is using an sqlite db for managing groups\/users and data from its apps (like the polls app in the tutorial), but I'm not yet sure where my external sqlite db, driven by my other scripts, fits into the grand scheme of things?\nWould I have to modify my external python scripts to write out to a table in the Django db (db.sqlite3 in the Django project dir in tutorial at least), then make a Django model based on my database structure and fields?\nBasically,I think my question boils down to:\n1) Do I need to create Django model based on my db, then access the one and only Django \"project db\", and have my external script write into it.\n2) or can Django utilise somehow a seperate db driven by another script somehow?\n3) Finally, is Django the right tool for such a task before I invest weeks of reading...","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1298,"Q_Id":21767229,"Users Score":1,"Answer":"If you care about taking control over every single aspect of how you want to render your data in HTML and serve it to others, Then for sure Django is a great tool to solve your problem.\nDjango's ORM models make it easier for you to read and write to your database, and they're database-agnostic. Which means that you can reuse the same code with a different database (like MySQL) in the future.\nSo, to wrap it up. If you're planning to do more development in the future, then use Django. If you only care about creating these HTML pages once and for all, then don't.\nPS: With Django, you can easily integrate these scripts into your Django project as management commands, run them with cronjobs and integrate everything you develop together with a unified data access layer.","Q_Score":0,"Tags":"python,django,sqlite","A_Id":21768188,"CreationDate":"2014-02-13T22:48:00.000","Title":"Django and external sqlite db driven by python script","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am trying to serve up some user uploaded files with Flask, and have an odd problem, or at least one that I couldn't turn up any solutions for by searching. I need the files to retain their original filenames after being uploaded, so they will have the same name when the user downloads them. Originally I did not want to deal with databases at all, and solved the problem of filename conflicts by storing each file in a randomly named folder, and just pointing to that location for the download. However, stuff came up later that required me to use a database to store some info about the files, but I still kept my old method of handling filename conflicts. I have a model for my files now and storing the name would be as simple as just adding another field, so that shouldn't be a big problem. I decided, pretty foolishly after I had written the implmentation, on using Amazon S3 to store the files. Apparently S3 does not deal with folders in the way a traditional filesystem does, and I do not want to deal with the surely convoluted task of figuring out how to create folders programatically on S3, and in retrospect, this was a stupid way of dealing with this problem in the first place, when stuff like SQLalchemy exists that makes databases easy as pie.  Anyway, I need a way to store multiple files with the same name on s3, without using folders. I thought of just renaming the files with a random UUID after they are uploaded, and then when they are downloaded (the user visits a page and presses a download button so I need not have the filename in the URL), telling the browser to save the file as its original name retrieved from the database. Is there a way to implement this in Python w\/Flask? When it is deployed I am planning on having the web server handle the serving of files, will it be possible to do something like this with the server? Or is there a smarter solution?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":143,"Q_Id":21807032,"Users Score":0,"Answer":"I'm stupid. Right in the Flask API docs it says you can include the parameter attachment_filename in send_from_directory if it differs from the filename in the filesystem.","Q_Score":0,"Tags":"python,amazon-s3,flask","A_Id":21817783,"CreationDate":"2014-02-16T03:48:00.000","Title":"Is there a way to tell a browser to download a file as a different name than as it exists on disk?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Maybe I got this wrong: Is there a way to automatically create the target table for a tabledata.insertAll command? If yes please point me in the right direction.\nIf not - what is the best approach to create the tables needed? Check for existing tables on startup and create the ones that does not exist by loading from GCS? Or can they be created directly from code without a load job?\nI have a number of event classes (Python Cloud endpoints) defined and the perfect solution would be using those definitions to create matching BQ tables.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":973,"Q_Id":21830868,"Users Score":4,"Answer":"There is no way to create a table automatically during streaming, since BigQuery doesn't know the schema. JSON data that you post doesn't have type information -- if there is a field \"123\" we don't know if that will always be a string or whether it should actually be an integer. Additionally, if you post data that is missing an optional field, the schema that got created would be narrower than the one you wanted.\nThe best way to create the table is with a tables.insert() call (no need to run a load job to load data from GCS). You can provide exactly the schema you want, and once the table has been created you can stream data to it. \nIn some cases, customers pre-create a month worth of tables, so they only have to worry about it every 30 days. In other cases, you might want to check on startup to see if the table exists, and if not, create it.","Q_Score":3,"Tags":"python,google-bigquery","A_Id":21868123,"CreationDate":"2014-02-17T13:51:00.000","Title":"Auto-create BQ tables for streaming inserts","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I tried to use pymsql with sqlalchemy using this code : \n    \n    from sqlalchemy import create_engine\n    engine = create_engine(\"mysql+pymsql:\/\/root:@localhost\/pydb\")\n    conn = engine.connect()\n    \nand this exception is raised here is the full stack trace : \n    \n    Traceback (most recent call last):\n      File \"D:\\Parser\\dal__init__.py\", line 3, in \n        engine = create_engine(\"mysql+pymsql:\/\/root:@localhost\/pydb\")\n      File \"C:\\Python33\\lib\\site-packages\\sqlalchemy-0.9.2-py3.3.egg\\sqlalchemy\\engine__init__.py\", line 344, in create_engine\n      File \"C:\\Python33\\lib\\site-packages\\sqlalchemy-0.9.2-py3.3.egg\\sqlalchemy\\engine\\strategies.py\", line 48, in create\n      File \"C:\\Python33\\lib\\site-packages\\sqlalchemy-0.9.2-py3.3.egg\\sqlalchemy\\engine\\url.py\", line 163, in make_url\n      File \"C:\\Python33\\lib\\site-packages\\sqlalchemy-0.9.2-py3.3.egg\\sqlalchemy\\engine\\url.py\", line 183, in _parse_rfc1738_args\n      File \"C:\\Python33\\lib\\re.py\", line 214, in compile\n        return _compile(pattern, flags)\n      File \"C:\\Python33\\lib\\re.py\", line 281, in _compile\n        p = sre_compile.compile(pattern, flags)\n      File \"C:\\Python33\\lib\\sre_compile.py\", line 498, in compile\n        code = _code(p, flags)\n      File \"C:\\Python33\\lib\\sre_compile.py\", line 483, in _code\n        _compile(code, p.data, flags)\n      File \"C:\\Python33\\lib\\sre_compile.py\", line 75, in _compile\n        elif _simple(av) and op is not REPEAT:\n      File \"C:\\Python33\\lib\\sre_compile.py\", line 362, in _simple\n        raise error(\"nothing to repeat\")\n    sre_constants.error: nothing to repeat","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1686,"Q_Id":21853660,"Users Score":0,"Answer":"Drop the : from your connection string after your username. It should instead be mysql+pymsql:\/\/root@localhost\/pydb","Q_Score":0,"Tags":"python,sqlalchemy,pymysql","A_Id":21866204,"CreationDate":"2014-02-18T12:20:00.000","Title":"Error when trying to use pymysql with sqlalchemy sre_constants.error: nothing to repeat","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have created an excel sheet using XLWT plugin using Python. Now, I need to re-open the excel sheet and append new sheets \/ columns to the existing excel sheet. Is it possible by Python to do this?","AnswerCount":2,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":8628,"Q_Id":21856559,"Users Score":2,"Answer":"You read in the file using xlrd, and then 'copy' it to an xlwt Workbook using xlutils.copy.copy().\nNote that you'll need to install both xlrd and xlutils libraries.\nNote also that not everything gets copied over. Things like images and print settings are not copied, for example, and have to be reset.","Q_Score":1,"Tags":"python,xlwt","A_Id":22414279,"CreationDate":"2014-02-18T14:20:00.000","Title":"How to append to an existing excel sheet with XLWT in Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm sometimes using a TextField to store data with a structure that may change often (or very complex data) into model instances, instead of modelling everything with the relational paradigm.\nI could mostly achieve the same kind of things using more models, foreignkeys and such, but it sometimes feels more straightforward to store JSON directly.\nI still didn't delve into postgres JSON type (can be good for read-queries notably, if I understand well). And for the moment I perform some json.dumps and json.loads each time I want to access this kind of data.\nI would like to know what are (theoretically) the performance and caching drawbacks of doing so (using JSON type and not), compared to using models for everything.\nHaving more knowledge about that could help me to later perform some clever comparison and profiling to enhance the overall performance.","AnswerCount":1,"Available Count":1,"Score":0.537049567,"is_accepted":false,"ViewCount":1302,"Q_Id":21908068,"Users Score":3,"Answer":"Storing data as json (whether in text-typed fields, or PostgreSQL's native jsontype) is a form of denormalization.\nLike most denormalization, it can be an appropriate choice when working with very difficult to model data, or where there are serious performance challenges with storing data fully normalized into entities.\nPostgreSQL reduces the impact of some of the problems caused by data denormalization by supporting some operations on json values in the database - you can iterate over json arrays or key\/value pairs, join on the results of json field extraction, etc. Most of the useful stuff was added in 9.3; in 9.2, json support is just a validating data type. In 9.4, much more powerful json features will be added, including some support for indexing in json values.\nThere's no simple one-size-fits all answer to your question, and you haven't really characterized your data or your workload. Like most database challenges \"it depends\" on what you're doing with the data.\nIn general, I would tend to say it's best to relationally model the data if it is structured and uniform. If it's unstructured and non-uniform, storage with something like json may be more appropriate.","Q_Score":1,"Tags":"python,json,django,postgresql","A_Id":21909779,"CreationDate":"2014-02-20T12:38:00.000","Title":"Django & postgres - drawbacks of storing data as json in model fields","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a django app which provides a rest api using Django-rest-framework. The API is used by clients as expected, but I also have another process(on the same node) that uses Django ORM to read the app's database, which is sqlite3.\nIs it better architecture for the process to use the rest api to interact(only reads) with the app's database? Or is there a better, perhaps more efficient way than making a ton of HTTP requests from the same node?\nThe problem with the ORM approach(besides the hacky nature) is that occasionally reads fail and must be retried. Also, I want to write to the app's db which would probably causes more sqlite concurrency issues.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":138,"Q_Id":21912993,"Users Score":0,"Answer":"It depends on what your application is doing.  If your REST application reads a piece of data from SQLITE using the Django ORM and then the other app does a write you can run into some interesting race situations.  To prevent that it might make sense to have both these applications as django-app in a single Django project.","Q_Score":0,"Tags":"python,django,sqlite,rest,orm","A_Id":21914906,"CreationDate":"2014-02-20T15:57:00.000","Title":"SOA versus Django ORM with multiple processes","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am trying to design an app that uses Google AppEngine to store\/process\/query data that is then served up to mobile devices via Cloud Endpoints API in as real time as possible.\nIt is straight forward enough solution, however I am struggling to get the right balance between, performance, cost and latency on AppEngine.\nScenario (analogy) is a user checks-in (many times per day from different locations, cities, countries), and we would like to allow the user to query all the data via their device and provide as up to date information as possible.\n\nSuch as:\n\nThe number of check-ins over the last:\n24 hours\n1 week\n1 month\nAll time\nWhere is the most checked in place\/city\/country over the same time periods\nWhere is the least checked in place over the same time periods\nOther similar querying reports\n\n\nWe can use Memcache to store the most recent checkins, pushing to the Datastore every 5 minutes, but this may not scale very well and is not robust!\nUse a Cron job to run the Task Queue\/Map Reduce to get the aggregates, averages for each location every 30 mins and update the Datastore.\nThe challenge is to use as little read\/writes over the datastore because the last \"24 hours\" data is changing every 5 mins, and hence so is the last weeks data, last months data and so on. The data has to be dynamic to some degree, so it is not fixed points in time, they are always changing - here in lies the issue!\nIt is not a problem to set this up, but to set it up in an efficient manner, balancing performance\/latency for the user and cost\/quotas for us is not so easy! \nThe simple solution would be to use SQL, and run date range queries but this will not scale very well.\nWe could eventually use BigTable & BigQuery for the \"All time\" time period querying, but in order to give the users as real-time as possible data via the API for the other time periods is proving quite the challenge!\nAny suggestions of AppEngine architecture\/approaches would be seriously welcomed.\nMany thanks.","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":173,"Q_Id":21941030,"Users Score":0,"Answer":"First, writes to the datastore take milliseconds. By the time your user hits the refresh button (or whatever you offer), the data will be as \"real-time\" as it gets.\nTypically, developers become concerned with real-time when there is a synchronization\/congestion issue, i.e. each user can update something (e.g. bid on an item), and all users have to get the same data (the highest bid) in real time. In your case, what's the harm if a user gets the number of check-ins which is 1 second old?\nSecond, data in Memcache can be lost at any moment. In your proposed solution (update the datastore every 5 minutes), you risk losing all data for the 5 min period.\nI would rather use Memcache in the opposite direction: read data from datastore, put it in Memcache with 60 seconds (or more) expiration, serve all users from Memcache, then refresh it. This will minimize your reads. I would do it, of course, unless your users absolutely must know how many checkins happened in the last 60 seconds.\nThe real question for you is how to model your data to optimize writes. If you don't want to lose data, you will have to record every checkin in datastore. You can save by making sure you don't have unnecessary indexed fields, separate out frequently updated fields from the rest, etc.","Q_Score":1,"Tags":"python,google-app-engine,mapreduce,task-queue","A_Id":21962823,"CreationDate":"2014-02-21T17:23:00.000","Title":"AppEngine real time querying - cost, performance, latency balancing act and quotas","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"Going through Django tutorial 1 using Python 2.7 and can't seem to resolve this error:\nOperationalError: no such table: polls_poll\nThis happens the moment I enter Poll.objects.all() into the shell.\nThings I've already tried based on research through the net:\n1) Ensured that 'polls' is listed under INSTALLED_APPS in settings.py\nNote: I've seen lots of suggestions inserting 'mysite.polls' instead of 'polls' into INSTALLED_APPS but this gives the following error: ImportError: cannot import name 'polls' from 'mysite'\n2) Run python manage.py syncdb . This creates my db.sqlite3 file successfully and seemingly without issue in my mysite folder.\n3) Finally, when I run python manage.py shell, the shell runs smoothly, however I do get some weird Runtime Warning when it starts and wonder if the polls_poll error is connected:\n\\django\\db\\backends\\sqlite3\\base.py:63: RuntimeWarning: SQLite received a naive datetime (2014-02-03 17:32:24.392000) while time zone support is active.\nAny help would be appreciated.","AnswerCount":4,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":13012,"Q_Id":21976383,"Users Score":11,"Answer":"I meet the same problem today and fix it I think you miss some command in tutorial 1 just do follow: \n.\/python manage.py makemigrations polls\npython manage.py sql polls\n.\/python manage.py syncdb\nthen fix it and gain the table polls and you can see the table created you should read the \"manage.py makemigrations\" command","Q_Score":5,"Tags":"python,django,shell,sqlite","A_Id":23184956,"CreationDate":"2014-02-23T23:49:00.000","Title":"Django Error: OperationalError: no such table: polls_poll","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a csv file with about 280 columns, which are possibly changing from time to time. Is there a way to import a csv file to sqlite3 and have it 'guess' the column types? \nI am using a python script to import this.","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1025,"Q_Id":22004809,"Users Score":0,"Answer":"make headers of the columns in csv as  the same column names in sqlite3 table. Then directly read and check the type by using type() before inserting into DB.","Q_Score":2,"Tags":"python,csv,sqlite","A_Id":22005726,"CreationDate":"2014-02-25T04:44:00.000","Title":"csv import sqlite3 without specifying column types","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"On OS X 10.9 and 10.9.1, the cx_Oracle works OK. But after I updated my system to OS X 10.9.2 yesterday, it cannot work. When connecting to Oracle database, DatabaseError is raised. And the error message is:\n\nORA-21561: OID generation failed\n\nCan anyone help me?","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":1020,"Q_Id":22060338,"Users Score":0,"Answer":"I haven't seen this on OS X but the general Linux solution is to add your hostname to \/etc\/hosts for the IP 127.0.0.1.","Q_Score":2,"Tags":"python,macos,oracle","A_Id":39339545,"CreationDate":"2014-02-27T06:04:00.000","Title":"cx_Oracle can't connect to Oracle database after updating OS X to 10.9.2","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"On OS X 10.9 and 10.9.1, the cx_Oracle works OK. But after I updated my system to OS X 10.9.2 yesterday, it cannot work. When connecting to Oracle database, DatabaseError is raised. And the error message is:\n\nORA-21561: OID generation failed\n\nCan anyone help me?","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":1020,"Q_Id":22060338,"Users Score":0,"Answer":"This can be fixed with a simple edit to your hosts file.\n\nFind the name of your local-machine by running hostname in your local-terminal\n$hostname\nEdit your local hosts file \n$vi \/etc\/hosts\nassuming $hostname gives local_machine_name append it to your localhost ,\n127.0.0.1       localhost       local_machine_name\npress esc and type wq! to save\n\nCheers!","Q_Score":2,"Tags":"python,macos,oracle","A_Id":41649509,"CreationDate":"2014-02-27T06:04:00.000","Title":"cx_Oracle can't connect to Oracle database after updating OS X to 10.9.2","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm using Amazon Linux AMI release 2013.09. I've install virtualenv and after activation then I run pip install mysql-connector-python, but when I run my app I get an error: ImportError: No module named mysql.connector. Has anyone else had trouble doing this? I can install it outside of virtualenv and my script runs without issues. Thanks in advance for any help!","AnswerCount":14,"Available Count":1,"Score":0.0428309231,"is_accepted":false,"ViewCount":73109,"Q_Id":22100757,"Users Score":3,"Answer":"Also something that can go wrong: Don't name your own module mysql\nimport mysql.connector will fail because the import gives the module in the project precedence over site packages and yours likely doesnt have a connector.py file.","Q_Score":35,"Tags":"python,mysql","A_Id":44177264,"CreationDate":"2014-02-28T16:37:00.000","Title":"Can not get mysql-connector-python to install in virtualenv","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I know that Redis have 16 databases by default, but what if i need to add another database, how can i do that using redis-py?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":460,"Q_Id":22110562,"Users Score":0,"Answer":"You cannot. The number of databases is not a dynamic parameter in Redis.\nYou can change it by updating the Redis configuration file (databases parameter) and restarting the server.\nFrom a client (Python or other), you can retrieve this value using the \"GET CONFIG DATABASES\" command. But the \"SET CONFIG DATABASES xxx\" command will be rejected.","Q_Score":1,"Tags":"python,database,redis,redis-py","A_Id":22111910,"CreationDate":"2014-03-01T05:29:00.000","Title":"Insert a new database in redis using redis.StrictRedis()","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'd rather just use raw MySQL, but I'm wondering if I'm missing something besides security concerns.  Does SQLAlchemy or another ORM handle scaling any better than just using pymysql or MySQLdb?","AnswerCount":2,"Available Count":2,"Score":0.0996679946,"is_accepted":false,"ViewCount":941,"Q_Id":22128419,"Users Score":1,"Answer":"SQL Alchemy is generally not faster (esp. as it uses those driver to connect).\nHowever, SQL Alchemy will help you structure your data in a sensible way and help keep the data consistent. Will also make it easier for you to migrate to a different db if needed.","Q_Score":0,"Tags":"python,sqlalchemy,flask,flask-sqlalchemy","A_Id":22128680,"CreationDate":"2014-03-02T13:49:00.000","Title":"Should I use an ORM like SQLAlchemy for a lightweight Flask web service?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'd rather just use raw MySQL, but I'm wondering if I'm missing something besides security concerns.  Does SQLAlchemy or another ORM handle scaling any better than just using pymysql or MySQLdb?","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":941,"Q_Id":22128419,"Users Score":1,"Answer":"Your question is too open to anyone guarantee SQLAlchemy is not a good fit, but SQLAlchemy probably will never be your problem to handle scalability. You'll have to handle almost the same problems with or without SQLAlchemy.\nOf course SQLAlchemy has some performance impact, it is a layer above the database driver, but it also will help you a lot.\nThat said, if you want to use SQLAlchemy to help with your security (SQL escaping), you can use the SQLAlchemy just to execute your raw SQL queries, but I recommend it to fix specific bottlenecks, never to avoid the ORM.","Q_Score":0,"Tags":"python,sqlalchemy,flask,flask-sqlalchemy","A_Id":22134840,"CreationDate":"2014-03-02T13:49:00.000","Title":"Should I use an ORM like SQLAlchemy for a lightweight Flask web service?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I would like for a user, without having to have an Amazon account, to be able to upload mutli-gigabyte files to an S3 bucket of mine. \nHow can I go about this? I want to enable a user to do this by giving them a key or perhaps through an upload form rather than making a bucket world-writeable obviously. \nI'd prefer to use Python on my serverside, but the idea is that a user would need nothing more than their web browser or perhaps opening up their terminal and using built-in executables. \nAny thoughts?","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":141,"Q_Id":22160820,"Users Score":0,"Answer":"This answer is relevant to .Net as language.\nWe had such requirement, where we had created an executable. The executable internally called a web method, which validated the app authenticated to upload files to AWS S3 or NOT.\nYou can do this using a web browser too, but I would not suggest this, if you are targeting big files.","Q_Score":0,"Tags":"python,file-upload,amazon-web-services,amazon-s3","A_Id":22162436,"CreationDate":"2014-03-04T00:59:00.000","Title":"user upload to my S3 bucket","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I've a bit of code that involves sending an e-mail out to my housemates when it's time to top up the gas meter. This is done by pressing a button and picking whoever's next from the database and sending an email. This is open to a lot of abuse as you can just press the button 40 times and send 40 emails.\nMy plan was to add the time the e-mail was sent to my postgres database and any time the button is pressed after, it checks to see if the last time the button was pressed was greater than a day. \nIs this the most efficient way to do this?\n(I realise an obvious answer would be to password protect the site so no outside users can access it and mess with the gas rota but unfortunately one of my housemates the type of gas-hole who'd do that)","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":76,"Q_Id":22178513,"Users Score":0,"Answer":"I asked about a soft button earlier. If your computer program is password\/access protected you could just store it all in a pickle\/config file somewhere, I am unsure what the value of the sql file is:\nuse last_push = time.time() and check the difference to current push if seconds difference less than x do not progress, if bigger than x reset last_push and progress....\nor am I missing something","Q_Score":0,"Tags":"python","A_Id":22181923,"CreationDate":"2014-03-04T17:13:00.000","Title":"Check time since last request","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I've a bit of code that involves sending an e-mail out to my housemates when it's time to top up the gas meter. This is done by pressing a button and picking whoever's next from the database and sending an email. This is open to a lot of abuse as you can just press the button 40 times and send 40 emails.\nMy plan was to add the time the e-mail was sent to my postgres database and any time the button is pressed after, it checks to see if the last time the button was pressed was greater than a day. \nIs this the most efficient way to do this?\n(I realise an obvious answer would be to password protect the site so no outside users can access it and mess with the gas rota but unfortunately one of my housemates the type of gas-hole who'd do that)","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":76,"Q_Id":22178513,"Users Score":0,"Answer":"If this is the easiest solution for you to implement, go right ahead. Worst case scenario, it's too slow to be practical and you'll need to find a better way. Any other scenario, it's good enough and you can forget about it.\nHonestly, it'll almost certainly be efficient enough to serve your purposes. The number of users at any one time will very rarely exceed one. An SQL query to determine if the timestamp is over a day before the current time will be quick, enough so that even the most determined gas-hole(!) wouldn't be able to cause any damage by spam-clicking the button. I would be very surprised if you ran into any problems.","Q_Score":0,"Tags":"python","A_Id":22179026,"CreationDate":"2014-03-04T17:13:00.000","Title":"Check time since last request","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I sometimes run python scripts that access the same database concurrently. This often causes database lock errors. I would like the script to then retry ASAP as the database is never locked for long.\nIs there a better way to do this than with a try except inside a while loop and does that method have any problems?","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":619,"Q_Id":22191236,"Users Score":0,"Answer":"If you are looking for concurrency, SQlite is not the answer. The engine doesn't perform good when concurrency is needed, especially when writing from different threads, even if the tables are not the same.\nIf your scripts are accessing different tables, and they have no relationships at DB level (i.e. declared FK's), you can separate them in different databases and then your concurrency issue will be solved.\nIf they are linked, but you can link them in the app level (script), you can separate them as well.\nThe best practice in those cases is implementing a lock mechanism with events, but honestly I have no idea how to implement such in phyton.","Q_Score":0,"Tags":"python,sqlite","A_Id":22222873,"CreationDate":"2014-03-05T07:23:00.000","Title":"Sqlite3 and Python: Handling a locked database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"Inside an web application ( Pyramid ) I create certain objects on POST which need some work done on them ( mainly fetching something from the web ). These objects are persisted to a PostgreSQL database with the help of SQLAlchemy. Since these tasks can take a while it is not done inside the request handler but rather offloaded to a daemon process on a different host. When the object is created I take it's ID ( which is a client side generated UUID ) and send it via ZeroMQ to the daemon process. The daemon receives the ID, and fetches the object from the database, does it's work and writes the result to the database.\n\nProblem: The daemon can receive the ID before it's creating transaction is committed. Since we are using pyramid_tm, all database transactions are committed when the request handler returns without an error and I would rather like to leave it this way. On my dev system everything runs on the same box, so ZeroMQ is lightning fast. On the production system this is most likely not an issue since web application and daemon run on different hosts but I don't want to count on this. \nThis problem only recently manifested itself since we previously used MongoDB with a write_convern of 2. Having only two database servers the write on the entity always blocked the web-request until the entity was persisted ( which is obviously is not the greatest idea ).\n\nHas anyone run into a similar problem?\nHow did you solve it?\n\nI see multiple possible solutions, but most of them don't satisfy me:\n\nFlushing the transaction manually before triggering the ZMQ message. However, I currently use SQLAlchemy after_created event to trigger it and this is really nice since it decouples this process completely and thus eliminating the risk of \"forgetting\" to tell the daemon to work. Also think that I still would need a READ UNCOMMITTED isolation level on the daemon side, is this correct?\nAdding a timestamp to the ZMQ message, causing the worker thread that received the message, to wait before processing the object. This obviously limits the throughput.\nDish ZMQ completely and simply poll the database. Noooo!","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":2062,"Q_Id":22245407,"Users Score":0,"Answer":"This comes close to your second solution:\nCreate a buffer, drop the ids from your zeromq messages in there and let you worker poll regularly this id-pool. If it fails retrieving an object for the id from the database, let the id sit in the pool until the next poll, else remove the id from the pool.\nYou have to deal somehow with the asynchronous behaviour of your system. When the ids arrive constantly before persisting the object in the database, it doesnt matter whether pooling the ids (and re-polling the the same id) reduces throughput, because the bottleneck is earlier.\nAn upside is, you could run multiple frontends in front of this.","Q_Score":1,"Tags":"python,postgresql,sqlalchemy,zeromq","A_Id":22247025,"CreationDate":"2014-03-07T08:48:00.000","Title":"ZeroMQ is too fast for database transaction","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am using mongodb 2.4.6 and python 2.7 .I have frequent executing queries.Is it possible to save the frequent qaueries results in cache.?\nThanks in advance!","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1377,"Q_Id":22250987,"Users Score":1,"Answer":"Yes but you will need to make one, how about memcached or redis?\nHowever as a pre-cautionary note, MongoDB does have its recently used data cached to RAM by the OS already so unless you are doing some really resource intensive aggregation query or you are using the results outside of your working set window you might not actually find that it increases performance all that much.","Q_Score":0,"Tags":"mongodb,python-2.7,caching","A_Id":22251094,"CreationDate":"2014-03-07T13:09:00.000","Title":"How to cache Mongodb Queries?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"Introduction\nI am working on a GPS Listener, this is a service build on twisted python, this app receive at least 100 connections from gps devices, and it is working without issues, each GPS send data each 5 seconds, containing positions. ( the next week must be at least 200 gps devices connected )\nDatabase\nI am using a unique postgresql connection, this connection is shared between all gps devices connected for save and store information, postgresql is using pgbouncer as pooler\nServer\nI am using a small pc as server, and I need to find a way to have a high availability application with out loosing data\nProblem\nAccording with my high traffic on my app, I am having issues with memory data after 30 minutes start to appear as no saved, however queries are being executed on postgres ( I have checked that on last activity )\nFake Solution\nI have amke a script that restart my app, postgres ang pgbouncer, however this is a wrong solution, because each time that I restart my app, gps get disconnected, and must to reconnected again\nPosible Solution\nI am thinking on a high availability solution based on a Data Layer, where each time when database have to be restarted or something happened, a txt file store data from gps devices.\nFor get it, I am thing on a no unique connection, I am thinking on a simple connection each time one data must be saved, and then test database, like a pooler, and then if database connection is wrong, the txt file store it, until database is ok again, and the other process read txt file and send info to database\nQuestion\nSince I am thinking on a app data pooler and a single connection each time when this data must be saved for try to no lost data, I want to know\n\nIs ok making single connection each time that data is saved for this\n  kind of app, knowing that connections will be done more than 100 times\n  each 5 seconds?\n\nAs I said, my question is too simple, which one is the right way on working with db connections on a high traffic app? single connections per query or shared unique connection for all app.\nThe reason on looking this single question, is looking for the right way on working with db connections considering memory resources.\nI am not looking for solve postgresql issues or performance, just to know the right way on working with this kind of applications. And that is the reason on give as much of possible about my application\nNote\nOne more thing,I have seen one vote to close this question, that is related to no clear question, when the question is titled with the word \"question\" and was marked on italic, now I have marked as gray for notice people that dont read the word \"question\"\nThanks a lot","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":270,"Q_Id":22256760,"Users Score":1,"Answer":"Databases do not just lose data willy-nilly. Not losing data is pretty much number one in their job description. If it seems to be losing data, you must be misusing transactions in your application. Figure out what you are doing wrong and fix it. \nMaking and breaking a connection between your app and pgbouncer for each transaction is not good for performance, but is not terrible either; and if that is what helps you fix your transaction boundaries then do that.","Q_Score":0,"Tags":"python,database,postgresql,gps,twisted","A_Id":22409012,"CreationDate":"2014-03-07T17:28:00.000","Title":"Right way to manage a high traffic connection application","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I use driving_distance function in pgRouting to work with my river network. There are 12 vertices in my river network, and I want to get the distance between all of these 12 vertices, starting from vertex_id No.1.\nThe result is fine, but I want to get other results using other vertices as starting point. I know it would not cost much time to change the SQL code everytime, but thereafter I would have more than 500 vertices in this river network, so I need to do this more efficiently.\nHow to use python to get what I want\uff1f How can I write a python script to do this\uff1f Or there are existing python script that I want\uff1f\nI am a novice with programming language, please give me any detailed advice, thank you.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":684,"Q_Id":22279499,"Users Score":1,"Answer":"pyscopg2 Is an excellent python module that allows your scripts to connect to your postgres database and run SQL whether as inputs or as fetch queries. You can have python walk through the number of possible combinations between vertices and have it build the individual SQL queries as strings. It can then run through them and print your output into a text file.","Q_Score":0,"Tags":"python,postgresql,pgrouting","A_Id":22392600,"CreationDate":"2014-03-09T07:23:00.000","Title":"How to use python to loop through all possible results in postgresql\uff1f","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Unfortunately I have a REHL3 and Python 2.3 and no chance of upgrading.\nDoes anyone have any examples of how to interact with the DB, openning sqlplus, logging in and then I only want a simple SELECT query bring the data to a CSV and then I can figure out the rest. \nAny ideas please?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":319,"Q_Id":22300744,"Users Score":0,"Answer":"I used a bash script to produce the csv file and then manipulated the data with Python.\nThat was the only solution I could think of with Python 2.3.","Q_Score":0,"Tags":"sql,oracle,shell,oracle10g,python-2.x","A_Id":23064270,"CreationDate":"2014-03-10T12:56:00.000","Title":"Simple query to Oracle SQL using Python 2.3","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm trying to determine the best practices for storing and displaying user input in MongoDB. Obviously, in SQL databases, all user input needs to be encoded to prevent injection attacks. However, my understanding is that with MongoDB we need to be more worried about XSS attacks, so does user input need to be encoded on the server before being stored in mongo? Or, is it enough to simply encode the string immediately before it is displayed on the client side using a template library like handlebars?\nHere's the flow I'm talking about:\n\nOn the client side, user updates their name to \"<script>alert('hi');<\/script>\".\n\nDoes this need to be escaped to \"&lt;script&gt;alert(&#x27;hi&#x27;);&lt;&#x2F;script&gt;\" before sending it to the server?\n\nThe updated string is passed to the server in a JSON document via an ajax request.\nThe server stores the string in mongodb under \"user.name\".\n\nDoes the server need to escape the string in the same way just to be safe? Would it have to first un-escape the string before fully escaping so as to not double up on the '&'?\n\nLater, user info is requested by client, and the name string is sent in JSON ajax response.\nImmediately before display, user name is encoded using something like _.escape(name).\n\nWould this flow display the correct information and be safe from XSS attacks? What about about unicode characters like Chinese characters?\nThis also could change how text search would need to be done, as the search term may need to be encoded before starting the search if all user text is encoded.\nThanks a lot!","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":2232,"Q_Id":22312452,"Users Score":4,"Answer":"Does this need to be escaped to \"&lt;script&gt;alert(&#x27;hi&#x27;);&lt;&#x2F;script&gt;\" before sending it to the server?\n\nNo, it has to be escaped like that just before it ends up in an HTML page - step (5) above.\nThe right type of escaping has to be applied when text is injected into a new surrounding context. That means you HTML-encode data at the moment you include it in an HTML page. Ideally you are using a modern templating system that will do that escaping for you automatically.\n(Similarly if you include data in a JavaScript string literal in a <script> block, you have to JS-encode it; if you include data in in a stylesheet rule you have to CSS-encode it, and so on. If we were using SQL queries with data injected into their strings then we would need to do SQL-escaping, but luckily Mongo queries are typically done with JavaScript objects rather than a string language, so there is no escaping to worry about.)\nThe database is not an HTML context so HTML-encoding input data on the way to the database is not the right thing to do.\n(There are also other sources of XSS than injections, most commonly unsafe URL schemes.)","Q_Score":7,"Tags":"javascript,python,ajax,mongodb,unicode","A_Id":22315740,"CreationDate":"2014-03-10T22:12:00.000","Title":"Encoding user input to be stored in MongoDB","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":1},{"Question":"building bsddb3-6.0.1, Python 3.3.2, BerkeleyDB 5.3, Windows7. \nFirst linker asked for libdb53s.lib, but there's no such file, so I deleted 's' symbol (in setup3.py) and now linker can find libdb53.lib, but... \n_bsddb.obj : error LNK2019: unresolved external symbol db_create referenced in f\nunction newDBObject\n_bsddb.obj : error LNK2019: unresolved external symbol db_strerror referenced in\n function makeDBError\n_bsddb.obj : error LNK2019: unresolved external symbol db_env_create referenced\nin function newDBEnvObject\n_bsddb.obj : error LNK2019: unresolved external symbol db_version referenced in\nfunction _promote_transaction_dbs_and_sequences\n_bsddb.obj : error LNK2019: unresolved external symbol db_full_version reference\nd in function _promote_transaction_dbs_and_sequences\n_bsddb.obj : error LNK2019: unresolved external symbol db_sequence_create refere\nnced in function newDBSequenceObject\nbuild\\lib.win-amd64-3.3\\bsddb3_pybsddb.pyd : fatal error LNK1120: 6 unresolved\nexternals\nerror: command '\"C:\\Program Files (x86)\\Microsoft Visual Studio 11.0\\VC\\BIN\\amd6\n4\\link.exe\"' failed with exit status 1120\nCopied BDB folders to bsddb3-6.0.1\\db \nbsddb3-6.0.1\\db\\lib contains libdb53.lib \nbsddb3-6.0.1\\db\\bin contains libdb53.dll \nAre there any ready to use bsddb3 binaries for Python3.3.2 ?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":183,"Q_Id":22373983,"Users Score":0,"Answer":"Deleting the 's' symbol isn't appropriate - the s designates the static libdb53 library.  Assuming you are building libdb53 from source as well, in the build_windows directory there is a Berkeley_DB.sln that includes Static_Debug and Static_Release configurations that will build these.\nHowever, your troubles may not end there.  I'm using the static libraries and still getting similar unresolved external errors.","Q_Score":2,"Tags":"python,windows,berkeley-db,bsddb","A_Id":22391487,"CreationDate":"2014-03-13T09:18:00.000","Title":"bsddb3-6.0.1 Windows7 bulid error: _bsddb.obj : error LNK2019: unresolved external symbol db_create referenced in function newDBObject","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I keep seeing what appears to be a partly-commited transaction using innodb tables:\n\nall my tables use innodb as a backend\nmysql  version:  5.5.31-0ubuntu0.13.04.1-log\npython web application based on uwsgi, each http request is wrapped in a separate transaction that is either commited or rolled back depending on whether an exception is generated during the request\neach request-serving process uses a single mysql connection that is not shared across processes\na couple of other processes connect to the DB to perform background tasks that are all wrapped in transactions\ntransactions are all created and tracked through a sqlalchemy middleware which is configured to not change the default mysql isolation level which is REPEATABLE READ\n\nDespite all this (I triple checked each item a couple of times), my DB appears to contain half-commited transactions:\n 1. 2 tables A and B with A that contains a foreign key to B (there are no constraints defined in the DB)\n 2. A contains a valid row that points to a non-existent row in B. \n 3. B contains rows with id + 1 and id - 1.\n 4. both rows in both tables are inserted within a single transaction\nTo summarize, I can't see what I could have possibly done wrong. I can't imagine I am hitting a bug in the mysql storage backend so, I am looking for help on how I could debug this further and what assumption I made above is the most likely to be wrong.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":73,"Q_Id":22389675,"Users Score":0,"Answer":"It took me a while but it appears that the transaction was automatically rolled back by error 1213 (deadlock) and 1205 (lock wait timeout exceeded). It did not help that these errors were caught in some internal middleware that tried to execute again the statement that failed instead of forwarding the error up to the transaction layer where the entire transaction could be retried or abandoned as a whole. The result was that the code would keep on executing normally under the assumption that the ongoing transaction was still ongoing while it had been rolled back by the mysql server.","Q_Score":0,"Tags":"python,mysql,sqlalchemy","A_Id":22668180,"CreationDate":"2014-03-13T20:03:00.000","Title":"mysql transaction commited only partly","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am using MySQLdb in python 3 to insert multiple rows using executemany. \nNow I need to get the primary keys after the multi insert.. \nIs there any way to get them?","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":591,"Q_Id":22399825,"Users Score":3,"Answer":"You can use connection.insert_id()","Q_Score":3,"Tags":"python,mysql","A_Id":22399907,"CreationDate":"2014-03-14T08:36:00.000","Title":"Get primary keys inserted after executemany","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am using MySQLdb in python 3 to insert multiple rows using executemany. \nNow I need to get the primary keys after the multi insert.. \nIs there any way to get them?","AnswerCount":2,"Available Count":2,"Score":0.0996679946,"is_accepted":false,"ViewCount":591,"Q_Id":22399825,"Users Score":1,"Answer":"When you use executemany you insert multiple rows at a time. You will get first inserted rows primery key using connection.inster_id() \nTo get all inserted ids, you have to run another query.","Q_Score":3,"Tags":"python,mysql","A_Id":22399968,"CreationDate":"2014-03-14T08:36:00.000","Title":"Get primary keys inserted after executemany","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have list of nested Json objects which I want to save into cassandra (1.2.15).\nHowever the constraint I have is that I do not know the column family's column data types before hand i.e each Json object has got a different structure with fields of different datatypes.\nSo I am planning to use dynamic composite type for creating a column family.\nSo I would like to know if there is an API or suggest some ideas on how to save such Json object list into cassandra.\nThanks","AnswerCount":1,"Available Count":1,"Score":0.3799489623,"is_accepted":false,"ViewCount":1459,"Q_Id":22437058,"Users Score":2,"Answer":"If you don't need to be able to query individual items from the json structure, just store the whole serialized string into one column.\nIf you do need to be able to query individual items, I suggest using one of the collection types: list, set, or map.  As far as typing goes, I would leave the value as text or blob and rely on json to handle the typing.  In other words, json encode the values before inserting and then json decode the values when reading.","Q_Score":1,"Tags":"java,python,json,cassandra,cassandra-cli","A_Id":22519952,"CreationDate":"2014-03-16T12:51:00.000","Title":"Import nested Json into cassandra","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I want to convert a csv file to a db (database) file using python. How should I do it ?","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":933,"Q_Id":22443297,"Users Score":0,"Answer":"I don't think this can be done in full generality without out-of-band information or just treating everything as strings\/text. That is, the information contained in the CSV file won't, in general, be sufficient to create a semantically \u201csatisfying\u201d solution. It might be good enough to infer what the types probably are for some cases, but it'll be far from bulletproof.\nI would use Python's csv and sqlite3 modules, and try to:\n\nconvert the cells in the first CSV line into names for the SQL columns (strip \u201coddball\u201d characters)\ninfer the types of the columns by going through the cells in the second CSV file line (first line of data), attempting to convert each one first to an int, if that fails, try a float, and if that fails too, fall back to strings\nthis would give you a list of names and a list of corresponding probably types from which you can roll a CREATE TABLE statement and execute it\ntry to INSERT the first and subsequent data lines from the CSV file\n\nThere are many things to criticize in such an approach (e.g. no keys or indexes, fails if first line contains a field that is a string in general but just so happens to contain a value that's Python-convertible to an int or float in the first data line), but it'll probably work passably for the majority of CSV files.","Q_Score":0,"Tags":"python,linux,database,sqlite","A_Id":22443606,"CreationDate":"2014-03-16T21:31:00.000","Title":"How do I convert a .csv file to .db file using python?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I made a script that opens a .xls file, writes a few new values in it, then saves the file.\nLater, the script opens it again, and wants to find the answers in some cells which contain formulas.\nIf I call that cell with openpyxl, I get the formula (ie: \"=A1*B1\").\nAnd if I activate data_only, I get nothing.\nIs there a way to let Python calculate the .xls file? (or should I try PyXll?)","AnswerCount":6,"Available Count":1,"Score":0.0333209931,"is_accepted":false,"ViewCount":24869,"Q_Id":22451973,"Users Score":1,"Answer":"No, and in openpyxl there will never be. I think there is a Python library that purports to implements an engine for such formualae which you can use.","Q_Score":13,"Tags":"python,excel,xlwt,openpyxl,pyxll","A_Id":22486256,"CreationDate":"2014-03-17T10:31:00.000","Title":"Calculating Excel sheets without opening them (openpyxl or xlwt)","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm using Django 1.6 with PostgreSQL and I want to use a two different Postgres users - one for creating the initial tables (syncdb) and performing migrations, and one for general access to the database in my application.  Is there a way of doing this?","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":78,"Q_Id":22523519,"Users Score":1,"Answer":"From .\/manage.py help syncdb:\n\n--database=DATABASE Nominates a database to synchronize. Defaults to the\n                          \"default\" database.\n\nYou can add another database definition in your DATABASES configuration, and run .\/manage.py syncdb --database=name_of_database_definition. You might want to create a small wrapper script for running that command, so that you don't have to type out the --database=... parameter by hand every time.\nsouth also supports that option, so you can also use it to specify the database for your migrations.","Q_Score":3,"Tags":"python,django,postgresql","A_Id":22527486,"CreationDate":"2014-03-20T04:28:00.000","Title":"Different Postgres users for syncdb\/migrations and general database access in Django","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Is it possible to call Python within an Oracle procedure? I've read plenty of literature about the reverse case (calling Oracle SQL from Python), but not the other way around.\nWhat I would like to do is to have Oracle produce a database table, then I would like to call Python and pass this database table to it in a DataFrame so that I could use Python to do something to it and produce results. I might need to call Python several times during the Oracle procedure. Does anyone know if this is possible and how could it be done?","AnswerCount":7,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":12854,"Q_Id":22564503,"Users Score":0,"Answer":"kind of complicated but possible. I have seen it once. You need to \n\ncreate a javaclass inside oracle database. This class calls a .py file in the directory which contains it.\ncreate a procedure that calls the java class of item 1.\nin your sql query, call the procedure of item 2 whenever you need it.","Q_Score":18,"Tags":"python,sql,oracle,pandas,cx-oracle","A_Id":53431165,"CreationDate":"2014-03-21T16:40:00.000","Title":"Calling Python from Oracle","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"insert_query = u\"\"\"\n        INSERT INTO did_you_know (\n        name, to_be_handled, creator, nominator, timestamp)\n        VALUES ('{0}', '{1}', '{2}', '{3}', '{4}')\n    \"\"\".format(\"whatever\", \"whatever\", \"whatever\", \"whatever\", \"whatever\") is my example.\nDoes every single value in a MySQL query have to contain quotes?\nWould this be acceptable or not?\nINSERT INTO TABLE VALUES ('Hello', 1, 1, 0, 1, 'Goodbye')\nThank you.","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":55,"Q_Id":22600861,"Users Score":0,"Answer":"You need to quote only character and other non-integer data types.\nInteger data types need not be quoted.","Q_Score":0,"Tags":"python,mysql,mysql-python","A_Id":22600910,"CreationDate":"2014-03-24T04:01:00.000","Title":"Does every single value in a MySQL query have to be quoted?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"so I am new to both programming and Python, but I think I have the issue narrowed down enough to ask a meaningful question.\nI am trying to use MySQLdb on my computer. No problem, right? I just enter:\nimport PyMySQL\nPyMySQL.install_as_MySQLdb()\nimport MySQLdb\nAt the top of the script.\nBut here is the problem. I installed Anaconda the other day to try to get access to more stats packages.\nAs a result, on the command line, \"which python\" returns:\n\/Users\/vincent\/anaconda\/bin\/python\nBased on reading other people's questions and answers, I think the problem is caused by being through Anaconda and not usr\/bin\/python, but I have no idea if this is correct... I would rather not uninstall Anaconda as I know that is not the right solution.\nSo, I would like to ask for a very basic list of steps of how fix this if possible.\nI am on OSX (10.9) Anaconda is 1.9.1 and I think python is 2.7\nThank you!","AnswerCount":1,"Available Count":1,"Score":0.3799489623,"is_accepted":false,"ViewCount":7318,"Q_Id":22602065,"Users Score":2,"Answer":"You don't need to uninstall anaconda. In your case, Try pip install PyMySql. If which pip return \/Users\/vincent\/anaconda\/bin\/pip, this should work.","Q_Score":1,"Tags":"python,compatibility,mysql-python,anaconda","A_Id":24050784,"CreationDate":"2014-03-24T05:56:00.000","Title":"ImportError: No module named PyMySQL - issues connecting with Anaconda","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am working on a Python\/Django application. The core logic rests in a Python application, and the web UI is taken care of by Django. I am planning on using ZMQ for communication between the core and UI apps. \nI am using a time-series database, which uses PostgreSQL in the background to store string data, and another time-series tool to store time-series data. So I already have a PostgreSQL requirement as part of the time-series db. But I need another db to store data (other than time-series), and I started work using PostgreSQL. \nsqlite3 was a suggestion from one of my team members. I have not worked on either, and I understand there are pros and cons to each one of them, I would like to understand the primary differences between the two databases in question here, and the usage scenarios.","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":759,"Q_Id":22662456,"Users Score":1,"Answer":"use postgreSQL, our team worked with sqlite3 for a long time. However, when you import data to db,it often give the information 'database is locked!'\nThe advantages of sqlite3\n\nit is small,as you put it, no server setup needed\nmax_length in models.py is not strictly, you set max_length=10, if you put 100 chars in the field, sqlite3 never complain about it,and never truncate it.\n\nbut postgreSQL is faster than sqlite3, and if you use sqlite3.\nsome day you want to migrate to postgreSQL, It is a matter beacuse sqlite3 never truncate string but postgreSQL complains about it!","Q_Score":1,"Tags":"python,database,django,sqlite,postgresql","A_Id":22664876,"CreationDate":"2014-03-26T13:26:00.000","Title":"Database engine choice for Django\/ Python application","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm making a Django app with the Two Scoops of Django template. Getting this Heroku error, are my Postgres production settings off? \n\nOperationalError at \/\ncould not connect to server: Connection refused\nIs the server running on host \"localhost\" (127.0.0.1) and accepting\nTCP\/IP connections on port 5432?\nException Location: \/app\/.heroku\/python\/lib\/python2.7\/site-packages\/psycopg2\/__init__.py\nforeman start works fine\nProcfile: web: python www_dev\/manage.py runserver 0.0.0.0:$PORT --noreload \nlocal.py settings: \nDATABASES = {\n    'default': {\n        'ENGINE': 'django.db.backends.postgresql_psycopg2',\n        'NAME': 'www',\n        'USER': 'amyrlam',\n        'PASSWORD': '*',\n        'HOST': 'localhost',\n        'PORT': '5432',\n    }\n}\nproduction.py settings: commented out local settings from above, added standard Heroku Django stuff:  \nimport dj_database_url\nDATABASES['default'] =  dj_database_url.config()\nSECURE_PROXY_SSL_HEADER = ('HTTP_X_FORWARDED_PROTO', 'https')\nALLOWED_HOSTS = ['*']\nimport os\nBASE_DIR = os.path.dirname(os.path.abspath(file))\nSTATIC_ROOT = 'staticfiles'\nSTATIC_URL = '\/static\/'\nSTATICFILES_DIRS = (\n    os.path.join(BASE_DIR, 'static'),\n)\nUPDATE: production settings, tried changing:\n\nimport dj_database_url\nDATABASES['default'] =  dj_database_url.config(default=os.environ[\"DATABASE_URL\"])\n(named my Heroku color URL to DATABASE_URL, same link in heroku config)","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1923,"Q_Id":22674128,"Users Score":5,"Answer":"Have you set your DJANGO_SETTINGS_MODULE environment variable? I believe what is happening is this: by default Django is using your local.py settings, which is why it's trying to connect on localhost.\nTo make Django detect and use your production.py settings, you need to do the following:\nheroku config:set DJANGO_SETTINGS_MODULE=settings.production\nThis will make Django load your production.py settings when you're on Heroku :)","Q_Score":3,"Tags":"python,django,postgresql,heroku","A_Id":22693845,"CreationDate":"2014-03-26T22:12:00.000","Title":"Can't get Django\/Postgres app settings working on Heroku","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"What is the code sintax to import an excel file to an MS access database IN PYTHON ?\nI have already tried making it a text file but with no sucesss","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":993,"Q_Id":22695359,"Users Score":0,"Answer":"In Access select \"External Data\" then under \"Import & Link\" select Excel. You should be able to just use the wizard to choose the Excel file and import the data to a new table.","Q_Score":0,"Tags":"excel,python-2.7,ms-access-2010","A_Id":22695473,"CreationDate":"2014-03-27T17:47:00.000","Title":"Import Excel spread sheet into Access","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm using a flask on an ec2 instance as server, and on that same machine I'm using that flask talking to a MongoDB. \nFor the ec2 instance I only leaves port 80 and 22 open, without leaving the mongo port (27017) because all the clients are supposed to talk to the flask server via http calls. Only in the flask I have code to insert or query the server.\nWhat I'm wondering is\nIs it secure enough? I'm using a key file to ssh to that ec2 machine, but I do need to be 99% sure that nobody else could query\/insert into the mongodb\nIf not, what shall I do?\nThanks!","AnswerCount":2,"Available Count":2,"Score":0.1973753202,"is_accepted":false,"ViewCount":182,"Q_Id":22715888,"Users Score":2,"Answer":"EC2 security policies by default block all incoming ports except ones you have sanctioned, as such the firewall will actually stop someone from getting directly to your MongoDB instance; as such yes it is secure enough.\nSince the instances are physically isolated there is no chance of the problems you would get on shared hosting of someone being able to route through the back of their instances to yours (though some things are still shared like IO read head).","Q_Score":1,"Tags":"python,mongodb,security,amazon-web-services,amazon-ec2","A_Id":22716431,"CreationDate":"2014-03-28T14:39:00.000","Title":"Security concerning MongoDB on ec2?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm using a flask on an ec2 instance as server, and on that same machine I'm using that flask talking to a MongoDB. \nFor the ec2 instance I only leaves port 80 and 22 open, without leaving the mongo port (27017) because all the clients are supposed to talk to the flask server via http calls. Only in the flask I have code to insert or query the server.\nWhat I'm wondering is\nIs it secure enough? I'm using a key file to ssh to that ec2 machine, but I do need to be 99% sure that nobody else could query\/insert into the mongodb\nIf not, what shall I do?\nThanks!","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":182,"Q_Id":22715888,"Users Score":2,"Answer":"Should be secure enough. If I understand correctly, you don't have ports 27017 open to the world, i.e. you have (or should)block it thru your aws security group and perhaps your local firewall on the ec2 instance, then the only access to that port will be from calls originating on the same server.\nNothing is 100% secure, but I don't see any holes in what you have done.","Q_Score":1,"Tags":"python,mongodb,security,amazon-web-services,amazon-ec2","A_Id":22716299,"CreationDate":"2014-03-28T14:39:00.000","Title":"Security concerning MongoDB on ec2?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am building a web crawler in Python using MongoDB to store a queue with all URLs to crawl. I will have several independent workers that will crawl URLs. Whenever a worker completes crawling a URL, it will make a request in the MongoDB collection \"queue\" to get a new URL to crawl. \nMy issue is that since there will be multiple crawlers, how can I ensure that two crawlers won't query the database at the same time and get the same URL to crawl?\nThanks a lot for your help","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":510,"Q_Id":22737982,"Users Score":0,"Answer":"Since reads in MongoDB are concurrent I completely understand what your saying. Yes, it is possible for two workers to pick the same row, amend it and then re-save it overwriting each other (not to mention wasted resources on crawling).\nI believe you must accept that one way or another you will lose performance, that is an unfortunate part of ensuring consistency.\nYou could use findAndModify to pick exclusively, since findAndModify has isolation it can ensure that you only pick a URL that has not been picked before. The problem is that findAndModify, due to being isolated, to slow down the rate of your crawling.\nAnother way could be to do an optimistic lock whereby you write a lock to the database rows picked very quickly after picking them, this will mean that there is some wastage when it comes to crawling duplicate URLs but it does mean you will get the maximum performance and concurrency out of your workers.\nWhich one you go for requires you to test and discover which best suites you.","Q_Score":0,"Tags":"python,mongodb,queue,mongodb-query,worker","A_Id":22738408,"CreationDate":"2014-03-29T22:55:00.000","Title":"Multiple workers getting information from a single MongoDB queue","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":1,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Hi Everyone Ive hit a road block in sql. Its the dreaded storing images in sql database. Apparently the solution to this is to store image in a file system.  Does anyone know any book or video tutorial that teaches this I cant seem to find any in the web. Im using My Sql and Python to learn how to work with images. I cant find any examples in the web.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":67,"Q_Id":22750497,"Users Score":1,"Answer":"Store the image as a file, and store the path of the file in the database.\nThe fact that the file is an image is irrelevant. If you want a more specific answer, you will need to ask a more specific question. Also, please edit your title so that it corresponds to the question.","Q_Score":0,"Tags":"python,sql,database,image","A_Id":22750529,"CreationDate":"2014-03-30T22:06:00.000","Title":"Sql Filesystem programming Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm using xlwt to create tables in excel. In excel there is a feature format as table which makes the table have an automatic filters for each column. Is there a way to do it using python?","AnswerCount":3,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":10141,"Q_Id":22831520,"Users Score":8,"Answer":"OK, after searching the web, I realized that with xlwt it's not possible to do it, but with XlsxWriter it's possible and very easy and convenient.","Q_Score":9,"Tags":"python,excel,python-2.7,xlwt","A_Id":22837578,"CreationDate":"2014-04-03T08:10:00.000","Title":"how to do excel's 'format as table' in python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm just about getting started on deploying my first live Django website, and I'm wondering how to set the Ubuntu server file permissions in the optimal way for security, whilst still granting the permissions required.\nFirstly a question of directories: I'm currently storing the site in ~\/www\/mysite.com\/{Django apps}, but have often seen people using \/var\/www\/... or \/srv\/www; is there any reason picking one of these directories is better than the other? or any reason why keeping the site in my home dir is a bad idea?\nSecondly, the permissions of the dir and files themselves. I'm serving using apache with mod_wsgi, and have the file WSGIScriptAlias \/ ~\/www\/mysite.com\/mainapp\/wsgi.py file. Apache runs as www-data user. For optimal security who should own the wsgi.py file, and what permissions should I grant it and its containing dir?\nSimilarly, for the www, www\/mysite.com, and www\/mysite.com\/someapp directories? What are the minimal permissions that are needed for the dirs and files?\nCurrently I am using 755 and 644 for dir and files respecitvely, which works well enough which allows the site to function, but I wonder if it is optimal\/too liberal. My Ubuntu user is the owner of most files, and www-data owns the sqlite dbs.","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":1003,"Q_Id":22872888,"Users Score":1,"Answer":"In regards to serving the application from your home directory, this is primarily preference based. However, deployment decisions may be made depending on the situation. For example, if you have multiple users making use of this server to host their website, then you would likely have the files served from their home directories. From a system administrator's perspective that is deploying the applications; you may want them all accessible from \/var\/www... so they are easier to locate. \nThe permissions you set for serving the files seem fine, however they may need to run as different users... depending on the number of people using this machine. For example, lets say you have one other application running on the server and that both applications run as www-data. If the www-data user has read permissions of Django's config file, then the other user could deploy a script that can read your database credentials.","Q_Score":4,"Tags":"python,django,apache,security,permissions","A_Id":24634526,"CreationDate":"2014-04-04T20:58:00.000","Title":"Security optimal file permissions django+apache+mod_wsgi","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm writing a little chatserver and client. There I got the idea to let users connect (nice :D) and when they want to protect their account by a password, they send \/password <PASS> and the server will store the account information in a sqlite database file, so only users, who know the passphrase, are able to use the name.\nBut there's the problem: I totally forgot, that sqlite3 in python is not thread-safe :( And now its not working. Thanks to git I can undo all changes with the storage.\nDoes anyone have an idea how to store this stuff, so that they are persistent when stopping\/starting the server?\nThanks.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":85,"Q_Id":22886350,"Users Score":0,"Answer":"OK, I'm using a simple JSON text file with automatic saving every minute","Q_Score":0,"Tags":"python,multithreading,sqlite","A_Id":24468686,"CreationDate":"2014-04-05T20:26:00.000","Title":"python simple data storage","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I wrote a migration script which works fine on sqlite, but if i try to apply the same to postgres it is stuck forever.\nWith a simple ps i can see the postres stuck on \"create table waiting\".\nThere are any best practice?","AnswerCount":4,"Available Count":2,"Score":0.0996679946,"is_accepted":false,"ViewCount":10633,"Q_Id":22896496,"Users Score":2,"Answer":"your database is most likely locked by another query.\nEspecially if you do stuff with their GUI pgAdmin, this can happen a lot I found. (truncating tables is especially tricky, sometimes pgAdmin crashes and the db gets stuck)\nwhat you want to do is to restart the complete postgresql service and try again.\nMake sure that you:\n\nminimize the usage of GUI pgadmin\nclose your cursors\/dbs with psycopg2 if you don't need them","Q_Score":20,"Tags":"python,postgresql,alembic","A_Id":22896742,"CreationDate":"2014-04-06T16:08:00.000","Title":"Alembic migration stuck with postgresql?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I wrote a migration script which works fine on sqlite, but if i try to apply the same to postgres it is stuck forever.\nWith a simple ps i can see the postres stuck on \"create table waiting\".\nThere are any best practice?","AnswerCount":4,"Available Count":2,"Score":0.1488850336,"is_accepted":false,"ViewCount":10633,"Q_Id":22896496,"Users Score":3,"Answer":"You can always just restart postgresql.","Q_Score":20,"Tags":"python,postgresql,alembic","A_Id":35921043,"CreationDate":"2014-04-06T16:08:00.000","Title":"Alembic migration stuck with postgresql?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am facing a problem while installing cx_Oracle module.\nI have installed Oracle Sql developer using which I can connect to any Oracle Server. I have also installed cx_oracle module. Now when I try to import the module I am reciving below mentioned error.\n\n\n\nimport cx_Oracle\nTraceback (most recent call last):\nFile \"\", line 1, in \n          import cx_Oracle\nImportError: DLL load failed: The specified module could not be found.\n\n\n\nAfter googling I can find that they want me to install Oracle client, but since I already have Oracle Sql developer which can act as a oracle client, I am unable to find the difference between two. Can someone please help me out.","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":112,"Q_Id":22943247,"Users Score":1,"Answer":"You will need C-language based Oracle \"client\" libraries installed on your local machine. (SQL Developer uses Java libraries). To connect to a remote database you can install the Oracle Instant Client.","Q_Score":0,"Tags":"python-2.7,cx-oracle","A_Id":25801626,"CreationDate":"2014-04-08T16:43:00.000","Title":"Error while importing cx_Oracle on windows","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am new to python. Could someone help me to figure out how to execute  following commands using cx_Oracle in python?\n\nSpool C:\\drop_tables.sql\nSELECT 'DROP TABLE ' || table_name || ' CASCADE CONSTRAINTS;' FROM user_tables;\nSpool off\n@C:\\drop_tables.sql\n\nI know I can use cursor.execute() for 2nd command but for other non sql commands specially 1 & 3 I am not getting any clue.\nAppreciate if someone can help.\nThanks,\nAravi","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":912,"Q_Id":22945637,"Users Score":1,"Answer":"So I achieved what I need by following way\ncur.execute(\"SELECT table_name FROM user_tables\")\nresult = cur.fetchall()\nfor row in result:\ncur.execute('DROP TABLE ' + row[0] + ' CASCADE CONSTRAINTS')*\nThanks much Luke for your idea.","Q_Score":1,"Tags":"python,cx-oracle","A_Id":22962131,"CreationDate":"2014-04-08T18:43:00.000","Title":"How to execute non sql commands in python using cx_Oracle","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm trying to store user data for a website in Python I'm making. Which is more efficient: \n-Storing all the user data in one huge table\n-Storing all the user data in several tables, one per user, in one database. \n-Storing each user's data in a XML or JSON file, one file per user. Each file has a unique name based on the user id. \nAlso, which is safer? I'm biased towards storing user data in JSON files because that is something I already know how to do. \nAny advice? I'd post some code I already have, but this is more theoretical than code-based.","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":242,"Q_Id":22951806,"Users Score":1,"Answer":"I don't think efficiency should be part of your calculus.\nI don't like either of your proposed designs.\nOne table?  That's not normalized.  I don't know what data you're talking about, but you should know about normalization.\nMultiple copies?  That's not scalable.  Every time you add a user you add a table?  Sounds like the perfect way to ensure that your user population will be small.\nIs all the data JSON?  Document based?  Maybe you should consider a NoSQL document based solution like MongoDB.","Q_Score":0,"Tags":"python,json,database,performance,security","A_Id":22951848,"CreationDate":"2014-04-09T02:39:00.000","Title":"Storing user data in one big database or in a different file for each user - which is more efficient?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":1},{"Question":"So I have a sqlite3 db, which I access from Python (2.7), where I would like to store more than the by default allowed 2.000 columns. I understand that there is a setting or command, SQLITE_MAX_COLUMN, which I can alter, so that my database can store up to ~32.000 columns. My question is how do I in practice set the maximum number of columns to for example 30.000 - what is the specific code, that I should run? Hope my question is clearly stated. Thanks","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1019,"Q_Id":22964033,"Users Score":2,"Answer":"That's a compile-time parameter for SQLite itself.  As in, you'll need to recompile the SQLite library in order to change it.  Nothing you can do in Python will be able to overcome this.","Q_Score":1,"Tags":"python-2.7,sqlite,max","A_Id":22964138,"CreationDate":"2014-04-09T13:27:00.000","Title":"How to actually change the maximum number of columns in SQLITE","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a script running continuously (using a for loop and time.sleep). It performs queries on models after loading Django. Debug is set to False in Django settings. However, I have noticed that the process will eat more and more memory. Before my time.sleep(5), I have added a call to django.db.reset_queries().\nThe very small leak (a few K at a time) has come to an almost full stop, and the issue appears to be addressed. However, I still can't explain why this solves the issue, since when I look at what reset_queries does, it seems to clear a list of queries located in each of connections.all().queries. When I try to output the length of these, it turns out to be 0. So the reset_queries() method seems to clear lists that are already empty.\nIs there any reason this would still work nevertheless? I understand reset_queries() is run when using mod wsgi regardless of whether DEBUG is True or not.\nThanks,","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":801,"Q_Id":22976981,"Users Score":4,"Answer":"After running a debugger, indeed, reset_queries() is required for a non-web python script that uses Django to make queries. For every query made in the while loop, I did find its string representation appended to ones of the queries list in connections.all(), even when DEBUG was set as False.","Q_Score":3,"Tags":"python,django,memory-leaks,daemon","A_Id":23063519,"CreationDate":"2014-04-10T01:25:00.000","Title":"Is django.db.reset_queries required for a (nonweb) script that uses Django when DEBUG is False?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I need to store anonymous form data (string, checkbox, FileUpload,...) for a Conference registration site, but ATContentTypes seems to me a little bit oversized.\nIs there a lightweight alternative to save the inputs - \nSQL and PloneFormGen are not an option\nI need to list, view and edit the data inputs in the backend...\nPlone 3.3.6\npython 2.4\nThanks","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":153,"Q_Id":22985483,"Users Score":0,"Answer":"One approach is to create a browser view that accepts and retrieves JSON data and then just do all of the form handling in custom HTML. The JSON could be stored in an annotation against the site root, or you could create a simple content type with a single field for holding the JSON and create one per record. You'll need to produce your own list and item view templates, which would be easier with the item-per-JSON-record approach, but that's not a large task.\nIf you don't want to store it in the ZODB, then pick whatever file store you want - like shelf - and dump it there instead.","Q_Score":2,"Tags":"python,forms,plone","A_Id":22986589,"CreationDate":"2014-04-10T10:33:00.000","Title":"Plone store form inputs in a lightweight way","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"folks. I'm very new to coding and Python. This is my second Stack question ever. Apologies if I'm missing the obvious. But, I've researched this and am still stuck.\nI've been trying to install and use mod_wsgi on CentOS 6.5 and am getting an error when trying to add a VirtualHost to Apache.\nThe mod_wsgi install seemed to go fine and my Apache status says:\nServer Version: Apache\/2.2.26 (Unix) mod_ssl\/2.2.26 OpenSSL\/1.0.1e-fips DAV\/2 mod_wsgi\/3.4 Python\/2.6.6 mod_bwlimited\/1.4\nSo, it looks to me like mod_wsgi is installed and running.\nI have also added this line to the my pre-main include file for httpd.conf:\nLoadModule wsgi_module modules\/mod_wsgi.so\n(I have looked ad mod_wsgi is in apache\/modules.)\nAnd, I have restarted Apache several times.\nThe error comes when I try to add a VirtualHost to any of the include files for https.conf.\nI always get an error message that says:\nInvalid command 'WSGIScriptAlias', perhaps misspelled or defined by a module not included in the server configuration\nIf I try to use a VirtualHost with a WSGIDaemonProcess reference, I get a similar error message about WSGIDaemonProcess.\nFrom reading on Stack and other places, it sounds like I don't have mod_wsgi installed, or I don't have the Apache config file loading it, or that I haven't restarted Apache since doing those things. But, I really think I have taken all of those steps.\nWhat am I missing here? Thanks!\nMarc  :-)","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":1164,"Q_Id":22992857,"Users Score":1,"Answer":"I think I figured the out. I needed to load the module and define the VirtualHost in the same include file. I was trying to load in the first include file and define the VirtualHost in the second. Putting them both in one file kept the error from happening.","Q_Score":0,"Tags":"python,linux,apache,mod-wsgi","A_Id":23104951,"CreationDate":"2014-04-10T15:48:00.000","Title":"mod_wsgi Error on CentOS 6.5","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"How do you set the header\/footer height in openpyxl? I don't find a setting for it. In a spreadsheet there are settings for height and autofit height but I don't see a means for setting either of those in openpyxl.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":563,"Q_Id":23068670,"Users Score":0,"Answer":"Look at the HeaderFooter class in the worksheet section of the code.","Q_Score":0,"Tags":"python,openpyxl","A_Id":23135653,"CreationDate":"2014-04-14T19:32:00.000","Title":"how to set the header\/footer height in openpyxl","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm trying to stop duplicates of a database entity called \"Post\" in my program. In order to do this I want to append a number like \"1\" or \"2\" next to it. In other words:\nhelloworld\nhelloworld1\nhelloworld2\nIn order to do this I need to query the database for postid's starting with helloworld. I read that GQL doesn't support the LIKE operation, so what can I do instead? \nThanks!","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":117,"Q_Id":23070947,"Users Score":0,"Answer":"Could you make the number a separate field?  Then you won't have to search for prefix.","Q_Score":0,"Tags":"python,google-app-engine,webapp2,gql","A_Id":23071550,"CreationDate":"2014-04-14T21:39:00.000","Title":"How to look for a substring GQL?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I need ID of an object which I've just added using session.add(). I need the auto-increment ID of this object before committing session. \nIf I called the object instance.id, I get None.\nIs there a way to get ID of a object without committing?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":6464,"Q_Id":23076483,"Users Score":13,"Answer":"Simple answer: call session.flush().","Q_Score":9,"Tags":"python,sqlalchemy","A_Id":23080688,"CreationDate":"2014-04-15T06:51:00.000","Title":"SQLAlchemy get added object's id without committing session","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Using postgresql9.1.9 in pylons1.0 project with mod_wsgi.\nGetting \"out of memory error\". \nQuery is of about 1.4 million lines and it crashes on query.all().\nThe column used for filtering is indexed.\nIn postgresql.conf, shared_buffers=24MB, max_connections=100.\nCan you please suggest the work around?","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":292,"Q_Id":23077972,"Users Score":1,"Answer":"Query is of about 1.4 million lines and it crashes on query.all().\n\nWhen you say it crashes: Do you mean the python client executable, or the PostgreSQL server?\nI strongly suspect the crash is in Python. I'd say you're reading all results into memory at once, and they jus tdon't fit.\nWhat you will need to do is progressively read the query results, process them, and discard them from memory. In psycopg2 you do this by iterating over the cursor object, or using cursor.fetchone(). Pylons should offer similar methods.","Q_Score":0,"Tags":"python,postgresql,mod-wsgi","A_Id":23084850,"CreationDate":"2014-04-15T08:10:00.000","Title":"MemoryError for postgresql 9.1.9","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I want to connect to a mySQL database with python, then query a number corresponding to an image, and load this image in Qt.  From what I found online, it is suggested not to use mysql database to store the image, but instead store a file location on the server.  If this is the case, can I load the image (do i have to download it?) into qt using mysql or do i have to open another connection with ftp, download the image to a folder, and then load it with qt?  If there are any resources on this type of workflow I would appreciate it.","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":421,"Q_Id":23190976,"Users Score":1,"Answer":"You don't need to download the file using FTP (or the like) to load it into Qt.\nAssuming the database stores the correct file path to the image, you can just use the same functionality once you get the file path, i.e. you anyway only need the file path to load the image into Qt. There is nothing special you would do by downloading the image itself.\nIf the database is on a remote server, a possible approach is to use the JDBC API to access the database, get the image as a binary file and then serialize it, which can be transferred over the network.","Q_Score":0,"Tags":"python,mysql,pyqt","A_Id":23191497,"CreationDate":"2014-04-21T04:50:00.000","Title":"mySQL connection and loading images to Qt","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":1,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I searched around and couldn't really find any information on this. Basically i have a database \"A\" and a database \"B\". What i want to do is create a python script (that will likely run as a cron job) that will collect data from database \"A\" via sql, perform an action on it, and then input that data into database \"B\".\nI have written it using functions something along the lines of:\n\nFunction 1 gets the date the script was last run\nFunction 2 Gets the data from Database \"A\" based on function 1\nFunction 3-5 Perform the needed actions\nFunction 6 Inserts data into Database \"B\"\n\nMy question is, it was mentioned to me that i should use a Class to do this rather than just functions. The only problem is, I am honestly a bit hazy on Classes and when to use them.\nWould a Class be better for this? Or is writing this out as functions that feed into each other better? If i would use a Class, could you tell me how it would look?","AnswerCount":1,"Available Count":1,"Score":0.6640367703,"is_accepted":false,"ViewCount":156,"Q_Id":23237444,"Users Score":4,"Answer":"Would a Class be better for this?\n\nProbably not.\nClasses are useful when you have multiple, stateful instances that have shared methods.  Nothing in your problem description matches those criteria.\nThere's nothing wrong with having a script with a handful of functions to perform simple data transfers (extract, transform, store).","Q_Score":3,"Tags":"python,mysql,database,class,oop","A_Id":23237519,"CreationDate":"2014-04-23T07:17:00.000","Title":"Collecting Data from Database, functions vs classes","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have made a database file using SQL commands in python. i have used quite a lot of foreign keys as well but i am not sure how to display this data onto qt with python? any ideas? i would also like the user to be able to add\/edit\/delete data","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":4532,"Q_Id":23268179,"Users Score":1,"Answer":"This question is a bit broad, but I'll try answering it anyway. Qt does come with some models that can be connected to a database. Specifically classes like QSqlTableModel. If you connect such a model to your database and set it as the model for a QTableView it should give you most of the behavior you want.\nUnfortunately I don't think I can be any more specific than that. Once you have written some code, feel free to ask a new question about a specific issue (remember to include example code!)","Q_Score":1,"Tags":"python,sql,qt,pyqt","A_Id":23281662,"CreationDate":"2014-04-24T11:55:00.000","Title":"How to display data from a database file onto pyqt so that the user can add\/delete\/edit the data?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":1,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Is there a way to use pandas to_excel function to write to the desktop, no matter which user is running the script? I've found answers for VBA but nothing for python or pandas.","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":781,"Q_Id":23279546,"Users Score":1,"Answer":"This depends on your operating system.\nYou're saying you'd like to save the file on the desktop of the user who is running the script right? \nOn linux (not sure if this is true of every distribution) you could pass in \"~\/desktop\/my_file.xls\" as the path where you're saving the file","Q_Score":2,"Tags":"python,pandas","A_Id":23279735,"CreationDate":"2014-04-24T20:51:00.000","Title":"to_excel on desktop regardless of the user","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"This is a very very strange issue. I have quite a large excel file (the contents of which I cannot discuss as it is sensitive data) that is a .xlsx and IS a valid excel file. \nWhen I download it from my email and save it on my desktop and try to open the workbook using xlrd, xlrd throws an AssertionError and does not show me what went wrong. \nWhen I open the file using my file browser, then save it (without making any changes), it works perfectly with xlrd. \nHas anyone faced this issue before? I tried passing in various flags to the open_workbook function to no avail and I tried googling for the error. So far I haven't found anything. \nThe method I used was as follows\n\n\n    file = open('bigexcelfile.xlsx')\n    fileString = file.read()\n    wb = open_workbook(file_contents=filestring)\n\n\nPlease help! The error is as follows\n\n\n    Traceback (most recent call last):\n      File \".\/varify\/samples\/resources.py\", line 354, in post\n        workbook = xlrd.open_workbook(file_contents=fileString)\n      File \"\/home\/vagrant\/varify-env\/lib\/python2.7\/site-packages\/xlrd\/__init__.py\", line 416, in open_workbook\n        ragged_rows=ragged_rows,\n      File \"\/home\/vagrant\/varify-env\/lib\/python2.7\/site-packages\/xlrd\/xlsx.py\", line 791, in open_workbook_2007_xml\n        x12sheet.process_stream(zflo, heading)\n      File \"\/home\/vagrant\/varify-env\/lib\/python2.7\/site-packages\/xlrd\/xlsx.py\", line 528, in own_process_stream\n        self_do_row(elem)\n      File \"\/home\/vagrant\/varify-env\/lib\/python2.7\/site-packages\/xlrd\/xlsx.py\", line 722, in do_row\n        assert tvalue is not None\n    AssertionError","AnswerCount":2,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":2289,"Q_Id":23346771,"Users Score":2,"Answer":"rename or Save as your Excel file as .xls instead of .xlsx\nThank You","Q_Score":6,"Tags":"python,excel,xlrd,fileparsing","A_Id":29564738,"CreationDate":"2014-04-28T16:50:00.000","Title":"xlrd cannot read xlsx file downloaded from email attachment","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have installed Python version 3.4.0 and I would like to do a project with MySQL database. I downloaded and tried installing MySQLdb, but it wasn't successful for this version of Python.\nAny suggestions how could I fix this problem and install it properly?","AnswerCount":11,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":143430,"Q_Id":23376103,"Users Score":0,"Answer":"for fedora and python3 use: dnf install mysql-connector-python3","Q_Score":53,"Tags":"python,mysql,python-3.x,mysql-python,python-3.4","A_Id":49185013,"CreationDate":"2014-04-29T22:01:00.000","Title":"Python 3.4.0 with MySQL database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm running a python script that makes modifications in a specific database.\nI want to run a second script once there is a modification in my database (local server).\nIs there anyway to do that?\nAny help would be very appreciated.\nThanks!","AnswerCount":3,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":20648,"Q_Id":23382499,"Users Score":3,"Answer":"You can use 'Stored Procedures' in your database a lot of RDBMS engines support one or multiple programming languages to do so. AFAIK postgresql support signals to call external process to. Google something like 'Stored Procedures in Python for PostgreSQL' or 'postgresql trigger call external program'","Q_Score":8,"Tags":"python,mysql,database,events","A_Id":23382595,"CreationDate":"2014-04-30T07:49:00.000","Title":"Run python script on Database event","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm trying to use the data collected by a form I to a sqlite query. In this form I've made a spin button which gets any numeric input (ie. either2,34 or 2.34) and sends it in the form of 2,34 which python sees as str.\nI've already tried to float() the value but it doesn't work. It seems to be a locale problem but somehow locale.setlocale(locale.LC_ALL, '') is unsupported (says WinXP).\nAll these happen even though I haven't set anything to greek (language, locale, etc) but somehow Windows does its magic.\nCan someone help?\nPS: Of course my script starts with # -*- coding: utf-8 -*- so as to have anything in greek (even comments) in the code.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":48,"Q_Id":23388647,"Users Score":1,"Answer":"AFAIK, WinXP supports setlocale just fine.\nIf you want to do locale-aware conversions, try using locale.atof('2,34') instead of float('2,34').","Q_Score":0,"Tags":"python,sqlite,pygtk","A_Id":23389055,"CreationDate":"2014-04-30T12:53:00.000","Title":"pygtk spinbutton \"greek\" floating point","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":1,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm using fixtures with SQLAlchemy to create some integration tests.\nI'd like to put SQLAlchemy into a \"never commit\" mode to prevent changes ever being written to the database, so that my tests are completely isolated from each other. Is there a way to do this?\nMy initial thoughts are that perhaps I could replace Session.commit with a mock object; however I'm not sure if there are other things that might have the same effect that I also need to mock if I'm going to go down that route.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":838,"Q_Id":23394785,"Users Score":3,"Answer":"The scoped session manager will by default return the same session object for each connection. Accordingly, one can replace .commit with .flush, and have that change persist across invocations to the session manager.\nThat will prevent commits.\nTo then rollback all changes, one should use session.transaction.rollback().","Q_Score":3,"Tags":"python,testing,sqlalchemy","A_Id":23702417,"CreationDate":"2014-04-30T17:48:00.000","Title":"sqlalchemy - force it to NEVER commit?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am writing a small web application using Flask and I have to use DynamoDB as backend for some hard requirements.\nI went through the tutorial on Flask website without establishing sqlite connection. All data were pulled directly from DynamoDB and it seemed to work.\nSince I am new to web development in general and Flask framework, do you see any problems with this approach?","AnswerCount":1,"Available Count":1,"Score":0.3799489623,"is_accepted":false,"ViewCount":637,"Q_Id":23510212,"Users Score":2,"Answer":"No. SQLite is just one option for backend storage.  SQLite is mentioned in the tutorial only for its simplicity in getting something working fast and simply on a typical local developers environment. (No db to or service to install\/configure etc.)","Q_Score":0,"Tags":"python,flask,amazon-dynamodb","A_Id":23512512,"CreationDate":"2014-05-07T06:21:00.000","Title":"Use Flask with Amazon DynamoDB without SQLite","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a mysql database with some huge tables, i have a task that I must run three queries one after another and the last one exports to the outfile.csv.\ni.e. \nQuery 1. Select values from some tables with certain parameter. then write into a new table. aprox 4.5 hours\nQuery 2. After the first one is done, then use the new table join with another to get results to new table. Then write to outfile.csv. aprox 2 hours\nHow do I manage to automatically call these queries one after another even though one can take 4 hours to finish\nI am open to any solution, Scripts, or database functions. I am running on ubuntu server so, no graphical solutions. \nThanks for your help.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":121,"Q_Id":23529212,"Users Score":2,"Answer":"you can just separate the queries with a semi-column and run them as a batch.","Q_Score":0,"Tags":"scripting,mysql-python","A_Id":23529243,"CreationDate":"2014-05-07T21:56:00.000","Title":"How to automatically run chain multiple mysql queries","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a server with a database, the server will listen for http requests, and using JSONs for \ndata transferring.\nCurrently, what my server code(python) mainly do is read the JSON file, convert it to SQL and make some modifications to the database. And the function of the server, as I see, is only like a converter between JSON and SQL. Is this the right procedure that people usually do?\nThen I come up with another idea, I can define a class for user information and every user's information in the database is an instance of that class. When I get the JSON file, first I put it into the instance, do some operation and then put it into the database. In my understanding, it adds a language layer between the http request and the database.\nThe question is, what do people usually do?","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":46,"Q_Id":23593618,"Users Score":0,"Answer":"People usually make use of a Web framework, instead of implementing the basic machinery themselves as you are doing. \nThat is: Python i s a great language that easily allows one to translate \"json into sql\" with a small amount of code - and it is great for learning. If you are doing this for educational purposes, it is a nice project to continue fiddling with, and maybe you can have some nice ideas in this answer and in others.\nBut for \"real world\" usage, the apparent simple plan comes up with real world issues. Tens or even hundreds of them. How to proper separate html\/css template from content from core logic, how to deal with many, many aspects of security, etc... \nThem, the frameworks come into play: a web-framewrok project is a software project that had, over the years, and soemtimes hundreds of hours of work from several contributors, thought about, and addresses all of the issues a real web application can and will face.\nSo, it is ok if one want to to everything from scratch if he believes he can come up with a a framework taht has distinguished capabilities not available in any existing project. And it is ok to make small projects for learning purposes. It is not ok to try to come up with something from scratch for real server production, without having a deep knowledge of all the issues involved, and knowing well at least 3, 4 frameworks.\nSo, now, you've got the basic understanding of a way to get to a framework - it istime to learn some of the frameworks tehmselves. Try, for example, Bottle and Flask (microframeworks), and Django (a fully featured framework for web application development), maybe Tornado (an http server, but with enough of a web framework in it to be usable, and to be very instructive)- just reading the documentation on \"how to get started\" with these projects, to get to a \"hello world\" page will lead you to lots of concepts you probably had not thought about yet.","Q_Score":0,"Tags":"python,sql,rdbms","A_Id":23593850,"CreationDate":"2014-05-11T14:11:00.000","Title":"How do people usually operate information on server database?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a server with a database, the server will listen for http requests, and using JSONs for \ndata transferring.\nCurrently, what my server code(python) mainly do is read the JSON file, convert it to SQL and make some modifications to the database. And the function of the server, as I see, is only like a converter between JSON and SQL. Is this the right procedure that people usually do?\nThen I come up with another idea, I can define a class for user information and every user's information in the database is an instance of that class. When I get the JSON file, first I put it into the instance, do some operation and then put it into the database. In my understanding, it adds a language layer between the http request and the database.\nThe question is, what do people usually do?","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":46,"Q_Id":23593618,"Users Score":0,"Answer":"The answer is: people do usually that, what they need to do. The layer between database and client normally provides a higher level api, to make the request independent from the actual database. But how this higher level looks like depends on the application you have.","Q_Score":0,"Tags":"python,sql,rdbms","A_Id":23593774,"CreationDate":"2014-05-11T14:11:00.000","Title":"How do people usually operate information on server database?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"Is there an option in psycopg2 (in the connect() method) similar to psql -w (never issue a password prompt) and -W (force psql to prompt for a password before connecting to a database)?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1041,"Q_Id":23606102,"Users Score":5,"Answer":"psycopg2 will never prompt for a password - that's a feature of psql, not of the underlying libpq that both psql and psycopg2 use. There's no equvialent of -w \/ -W because there's no password prompt feature to turn on\/off.\nIf you want to prompt for a password you must do it yourself in your code: trap the exception thrown when authentication fails because a password is required, prompt the user for a password, and reconnect using the password. That's what psql does anyway, if you take a look at the sources.","Q_Score":2,"Tags":"python,postgresql,psycopg2","A_Id":23606436,"CreationDate":"2014-05-12T10:02:00.000","Title":"Is there a way to ask the user for a password or not with psycopg2?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a question in MySQL and Python MySQLdb library:\nSuppose I'd like to insert a bulk in to the DB. When I'm inserting, there are possibly a duplicated among the records in the bulk, or a record in the bulk may be a duplicate of a record in the table. In case of duplicates, I'd like to ignore the duplication and just insert the rest of the bulk. In case of a duplication in within the bulk, I'd like that only one of the records (any of them) will be inserted, and the rest of the bulk will also be inserted.\nHow can I write it in MySQL syntax? And is it built-in in MySQLdb library in Python?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":289,"Q_Id":23636068,"Users Score":0,"Answer":"Step 1 - Make your initial insert into a staging table.  \nStep 2 - deal with duplicate records and all other issues.\nStep 3 - write to your real tables from the staging table.","Q_Score":1,"Tags":"python,mysql,sql,mysql-python","A_Id":23636177,"CreationDate":"2014-05-13T15:56:00.000","Title":"Bulk insert into MySQL on duplicate","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have been going through the Google App Engine documentation (Python) now and found two different types of storage.\n\nNDB Datastore\nDB Datastore \n\nBoth quota limits (free) seem to be same, and their database design too. However NDB automatically cache data in Memcache!\nI am actually wondering when to use which storage? What are the general practices regarding this? \nCan I completely rely on NDB and ignore DB? How should it be done?\nI have been using Django for a while and read that in Django-nonrel the JOIN operations can be somehow done in NDB! and rest of the storage is used in DB! Why is that? Both storages are schemaless and pretty well use same design.. How is that someone can tweak JOIN in NDB and not in DB?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":568,"Q_Id":23645572,"Users Score":5,"Answer":"In simple words these are two versions of datastore . db being the older version and ndb the newer one. The difference is in the models, in the datastore these are the same thing. NDB provides advantages like handling caching (memcache) itself. and ndb is faster than db. so you should definitely go with ndb. to use ndb datastore just use ndb.Model while defining your models","Q_Score":2,"Tags":"python,django,google-app-engine","A_Id":23646875,"CreationDate":"2014-05-14T04:19:00.000","Title":"App Engine: Difference between NDB and Datastore","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I just wanted to know if it is possible to insert the contents of a local tabulated html file into an Excel worksheet using xlsxwriter?  Manually it works fine by just dragging and dropping the file into Excel and the formatting is clear, but I can't find any information on inserting file contents into Excel using xlsxwriter.  I can only find information related to inserting an image into Excel.\nMany thanks for reading this,\nMikG","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":448,"Q_Id":23673433,"Users Score":1,"Answer":"No, such functionality is not what xlsxwriter offers.\nThis package is able to write Excel files, but as importing HTML you describe is using MS Excell GUI functionality and as MS Excel is not an requirement of xlsxwriter, do not expect it to be present.\nOn the other hand, you could play with Python to do the conversion of HTML to spreadsheet data yourself, it is definitely not drag and drop solution, but for repetitive tasks this can be much more productive at the end.","Q_Score":0,"Tags":"python,xlsxwriter","A_Id":23674407,"CreationDate":"2014-05-15T08:50:00.000","Title":"Using Python's xlsxwriter to drop a tabulated html file into worksheet - is this possible?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have an app which will work in multiple timezones. I need the app to be able to say \"Do this at 10 PM, 12 April, 2015, in the America\/New York timezone and repeat every 30 days.\" (And similar).\nIf I get a datetime from the user in PST, should I be storing the datetime in DB after converting to UTC?\nPros: Easier to manage, every datetime in DB is in UTC.\nCons: Can not take DST in account. (I think).","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":158,"Q_Id":23676718,"Users Score":1,"Answer":"Yes, you should store everything in your db in UTC.\nI don't know why you say you won't be able to cope with DST. On the contrary, any good timezone library - such as pytz - is quite capable of translating UTC to the correct time in any timezone, taking DST into account.","Q_Score":0,"Tags":"python,django,datetime,timezone","A_Id":23676984,"CreationDate":"2014-05-15T11:19:00.000","Title":"Convert datetime to UTC before storing in DB?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"My web app asks users 3 questions and simple writes that to a file, a1,a2,a3. I also have real time visualization of the average of the data (reads real time from file).\nMust I use a database to ensure that no\/minimal information is lost? Is it possible to produce a queue of read\/writes>(Since files are small I am not too worried about the execution time of each call). Does python\/flask already take care of this?\nI am quite experienced in python itself, but not in this area(with flask).","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":31,"Q_Id":23703135,"Users Score":0,"Answer":"I see a few solutions:\n\nread \/dev\/urandom a few times, calculate sha-256 of the number and use it as a file name; collision is extremely improbable\nuse Redis and command like LPUSH, using it from Python is very easy; then RPOP from right end of the linked list, there's your queue","Q_Score":0,"Tags":"python,flask","A_Id":23703319,"CreationDate":"2014-05-16T19:24:00.000","Title":"Is it possible to make writing to files\/reading from files safe for a questionnaire type website?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Hi I am trying to write python functional tests for our application. It involves several external components and we are mocking them all out.. We have got a better framework for mocking a service, but not for mocking a database yet. \nsqlite is very lite and thought of using them but its a serverless, is there a way I can write some python wrapper to make it a server or I should look at other options like HSQL DB?","AnswerCount":1,"Available Count":1,"Score":-0.1973753202,"is_accepted":false,"ViewCount":535,"Q_Id":23744128,"Users Score":-1,"Answer":"I don't understand your problem. Why do you care that it's serverless?\nMy standard technique for this is:\n\nuse SQLAlchemy\nin tests, configure it with sqlite:\/\/\/ or sqlite:\/\/\/:memory:","Q_Score":0,"Tags":"python,sqlite,unit-testing","A_Id":23744831,"CreationDate":"2014-05-19T17:52:00.000","Title":"how to do database mocking or make sqlite run on localhost?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am working on my Python project using PySide as my Ui language. My projet is a game which require an internet connection to update the users'score and store in the database.\nMy problem is how can I store my database in the internet. I mean that all users can access this information when they are connected to an internet (when they are playing my game) and the information\/database must be updated all the time.\nI am not sure which database is the most appropriate, how to store this information\/database in the internet, how to access this information.\nI am using Python and PySide.\nFor the database, I currently use PySide.QtSql .\nThank you for answer(s) or suggestion(s).","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":193,"Q_Id":23754108,"Users Score":0,"Answer":"I'm not familiar with PySide .. but the idea is \nyou need to build a function that when internet connection is available it should synchronize your local database with online database and in the server-side you need to build a script that can handle requests ( POST \/ GET ) to receive the scores and send it to database and I suggest MySQL .. \nHope that helps","Q_Score":0,"Tags":"python,database,sockets,pyside,qtsql","A_Id":23754331,"CreationDate":"2014-05-20T07:59:00.000","Title":"Using Database with Pyside and Socket","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":1,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I need to develop an A\/B testing method for my users. Basically I need to split my users into a number of groups - for example 40% and 60%.\nI have around 1,000,00 users and I need to know what would be my best approach. Random numbers are not an option because the users will get different results each time. My second option is to alter my database so each user will have a predefined number (randomly generated). The negative side is that if I get 50 for example, I will always have that number unless I create a new user. I don't mind but I'm not sure that altering the database is a good idea for that purpose. \nAre there any other solutions so I can avoid that?","AnswerCount":4,"Available Count":2,"Score":0.1488850336,"is_accepted":false,"ViewCount":1690,"Q_Id":23846617,"Users Score":3,"Answer":"Run a simple algorithm against the primary key. For instance, if you have an integer for user id, separate by even and odd numbers.\nUse a mod function if you need more than 2 groups.","Q_Score":2,"Tags":"python,mysql,python-2.7","A_Id":23846676,"CreationDate":"2014-05-24T15:16:00.000","Title":"Algorithm for A\/B testing","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I need to develop an A\/B testing method for my users. Basically I need to split my users into a number of groups - for example 40% and 60%.\nI have around 1,000,00 users and I need to know what would be my best approach. Random numbers are not an option because the users will get different results each time. My second option is to alter my database so each user will have a predefined number (randomly generated). The negative side is that if I get 50 for example, I will always have that number unless I create a new user. I don't mind but I'm not sure that altering the database is a good idea for that purpose. \nAre there any other solutions so I can avoid that?","AnswerCount":4,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":1690,"Q_Id":23846617,"Users Score":0,"Answer":"I would add an auxiliary table with just userId and A\/B. You do not change existent table and it is easy to change the percentage per class if you ever need to. It is very little invasive.","Q_Score":2,"Tags":"python,mysql,python-2.7","A_Id":23846772,"CreationDate":"2014-05-24T15:16:00.000","Title":"Algorithm for A\/B testing","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm installing MySQL 5.6 Community Edition using MySQL installer and everything was installed properly except for \"Connector\/Python 2.7 1.1.6\".\nUpon mousing over, I get the error message \"The product requires Python 2.7 but it was not detected on this machine. Python 2.7 requires manual installation and must be installed prior to installing this product\"\nThe problem is, I have Python 2.7 installed in C: already and I can't seem to direct this detection towards where I have Python 2.7.\n(I am using Windows 8)","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":50,"Q_Id":23866874,"Users Score":0,"Answer":"Check if there is any install path dependencies on your installer to figure out if your python is in the right place.\nBut I recommend that you install the connector you want manually.\nP.S. Are you sure you need the connector? Or you just saw the error and assumed you need it?","Q_Score":0,"Tags":"mysql,django,python-2.7","A_Id":23866951,"CreationDate":"2014-05-26T09:24:00.000","Title":"Connector installation error (MySQL installer)","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I was wondering in which cases do I need to restart the database server in Django on production. Whether it is Postgres\/MySQL, I was just thinking do we need to restart the database server at all. If we need to restart it, when and why do we need to restart the server?\nAny explanation would be really helpful, Cheers!","AnswerCount":3,"Available Count":3,"Score":-0.0665680765,"is_accepted":false,"ViewCount":237,"Q_Id":23920481,"Users Score":-1,"Answer":"Usually when the settings that are controlling the application are changed then the server has to be restarted.","Q_Score":0,"Tags":"python,mysql,django,postgresql","A_Id":23920627,"CreationDate":"2014-05-28T19:41:00.000","Title":"When do I need to restart database server in Django?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I was wondering in which cases do I need to restart the database server in Django on production. Whether it is Postgres\/MySQL, I was just thinking do we need to restart the database server at all. If we need to restart it, when and why do we need to restart the server?\nAny explanation would be really helpful, Cheers!","AnswerCount":3,"Available Count":3,"Score":0.1325487884,"is_accepted":false,"ViewCount":237,"Q_Id":23920481,"Users Score":2,"Answer":"You will not NEED to restart your database in production due to anything you've done in Django. You may need to restart it to change your database security or configuration settings, but that has nothing to do with Django and in a lot of cases doesn't even need a restart.","Q_Score":0,"Tags":"python,mysql,django,postgresql","A_Id":23920963,"CreationDate":"2014-05-28T19:41:00.000","Title":"When do I need to restart database server in Django?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I was wondering in which cases do I need to restart the database server in Django on production. Whether it is Postgres\/MySQL, I was just thinking do we need to restart the database server at all. If we need to restart it, when and why do we need to restart the server?\nAny explanation would be really helpful, Cheers!","AnswerCount":3,"Available Count":3,"Score":1.2,"is_accepted":true,"ViewCount":237,"Q_Id":23920481,"Users Score":1,"Answer":"You shouldn't really ever need to restart the database server.\nYou probably do need to restart - or at least reload - the web server whenever any of the code changes. But the db is a separate process, and shouldn't need to be restarted.","Q_Score":0,"Tags":"python,mysql,django,postgresql","A_Id":23920777,"CreationDate":"2014-05-28T19:41:00.000","Title":"When do I need to restart database server in Django?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am using pyhs2 as hive client. The sql statement with \u2018where\u2019 clause was not recognized. Got\n\n'pyhs2.error.Pyhs2Exception: 'Error while processing statement:\nFAILED: Execution Error,  return code 1 from\norg.apache.hadoop.hive.ql.exec.mr.MapRedTask'\n\nBut it runs ok in hive shell.","AnswerCount":1,"Available Count":1,"Score":0.537049567,"is_accepted":false,"ViewCount":945,"Q_Id":23971667,"Users Score":3,"Answer":"Fixed! It was due to permission on remote server. Changed user in connect statement from 'root' to 'hdfs' solved the problem.","Q_Score":1,"Tags":"python,sql,client,hive","A_Id":23984349,"CreationDate":"2014-05-31T15:24:00.000","Title":"python hive client pyhs2 does not recognize 'where' clause in sql statement","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"So in my spare time, I've been developing a piece of network monitoring software that essentially can be installed on a bunch of clients, and the clients report data back to the server(RAM\/CPU\/Storage\/Network usage, and the like). For the administrative console as well as reporting, I've decided to use Django, which has been a learning experience in itself. \nThe Clients report to the Server asynchronously, with whatever data they happen to have(As of right now, it's just received and dumped, not stored in a DB). I need to access this data in Django. I have already created the models to match my needs. However, I don't know how to go about getting the actual data into the django DB safely. \nWhat is the way to go about doing this?  I thought of a few options, but they all had some drawbacks:\n\nGive the Django app a reference to the Server, and just start a thread that continuously checks for new data and writes it to the DB. \nHave the Server access the Django DB directly, and write it's data there. \n\nThe problem with 1 is that im even more tightly coupling the server with the django app, but the upside is that I can use the ORM to write the data nicely. \nThe problem with 2 is that I can't use the ORM to write data, and I'm not sure if it could cause blocking on the DB in some cases. \nIs there some obvious good option I'm missing? I'm sorry if this question is vague. I'm very new to Django, and I don't want to write myself into a corner.","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":849,"Q_Id":23987050,"Users Score":1,"Answer":"I chose option 1 when I set up my environment, which does much of the same stuff.\nI have a JSON interface that's used to pass data back to the server.  Since I'm on a well-protected VLAN, this works great.  The biggest benefit, like you say, is the Django ORM.  A simple address call with proper data is all that's needed.  I also think this is the simplest method.\nThe \"blocking on the DB\" issue should be non-existent.  I suppose that it would depend on the DB backend, but really, that's one of the benefits of a DB.  For example, a single-threaded file-based sqlite instance may not work.\nI keep things in Django as much as I can.  This could also help with DB security\/integrity, since it's only ever accessed in one place.  If your client accesses the DB directly, you'll need to ship username\/password with the Client.\nMy recommendation is to go with 1.  It will make your life easier, with fewer lines of code.  Besides, as long as you code Client properly, it should be easy to modify DB access later on down the road.","Q_Score":2,"Tags":"python,django,orm","A_Id":23987194,"CreationDate":"2014-06-02T03:41:00.000","Title":"How to access Django DB and ORM outside of Django","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm curious if there's a way to insert a new row (that would push all the existing rows down) in an existing openpyxl worksheet?  (I'm looking to insert at the first row if it helps)\nI looked through all the docs and didn't see anything mentioned.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":5098,"Q_Id":24006376,"Users Score":0,"Answer":"This is currently not directly possible in openpyxl because it would require the reassigning of all cells below the new row. \nYou can do it yourself by iterating through the relevant rows (starting at the end) and writing a new row with the values of the previous row. Then you create a row of cells where you wan them.","Q_Score":1,"Tags":"python,openpyxl","A_Id":24012565,"CreationDate":"2014-06-03T02:53:00.000","Title":"How to insert a row in openpyxl","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a \"local\" Oracle database in my work network. I also have a website at a hosting service.\nCan I connect to the 'local' Oracle database from the hosting service? Or does the Oracle database need to be at the same server as my website?\nAt my work computer I can connect to the Oracle database with a host name, username, password, and port number.","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":490,"Q_Id":24015758,"Users Score":1,"Answer":"It can depend on how your hosting is setup, but if it is allowed you will need the following. \n\nStatic IP, or Dynamic DNS setup so your home server can be found regularly. \nPort forwarding on your router to allow traffic to reach the server. \nThe willingness to expose your home systems to the dangers of the internet\n\nStrictly speaking a static IP\/Dynamic DNS setup is not required, but if you don't use that kind of setup, you will have to change the website configuration every time your home system changes IPs, the frequency of which depends on your ISP.  It's also worth noting that many ISP's consider running servers on your home network a violation of the terms of service for residential customers, but in practice as long as you aren't generating too much traffic, it's not usually an issue.\nWith Port forwarding on your router, you can specify traffic incoming on a particular port be redirected to a specific internal address:port on your network, (e.g. myhomesystem.com:12345 could be redirected to 192.168.1.5:1521)\nOnce those are in place, you can use the static IP, or the Dynamic DNS entry as the hostname to connect to.","Q_Score":0,"Tags":"python,database,django,oracle,database-connection","A_Id":24016200,"CreationDate":"2014-06-03T12:54:00.000","Title":"Connect to local Oracle database from online website","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am using Flask to make a small webapp to manage a group project, in this website I need to manage attendances, and also meetings reports. I don't have the time to get into SQLAlchemy, so I need to know what might be the bad things about using CSV as a database.","AnswerCount":4,"Available Count":2,"Score":-0.049958375,"is_accepted":false,"ViewCount":3024,"Q_Id":24072231,"Users Score":-1,"Answer":"I am absolutely baffled by how many people discourage using CSV as an database storage back-end format.\n\nConcurrency: There is NO reason why CSV can not be used with concurrency.  Just like how a database thread can write to one area of a binary file at the same time that another thread writes to another area of the same binary file.  Databases can do EXACTLY the same thing with CSV files.  Just as a journal is used to maintain the atomic nature of individual transactions, the same exact thing can be done with CSV.\n\nSpeed: Why on earth would a database read and write a WHOLE file at a time, when the database can do what it does for ALL other database storage formats, look up the starting byte of a record in an index file and SEEK to it in constant time and overwrite the data and comment out anything left over and record the free space for latter use in a separate index file, just like a database could zero out the bytes of any unneeded areas of a binary \"row\" and record the free space in a separate index file... I just do not understand this hostility to non-binary formats, when everything that can be done with one format can be done with the other... everything, except perhaps raw binary data compression, depending on the particular CSV syntax in use (special binary comments... etc.).\n\nEmergency access: The added benefit of CSV is that when the database dies, which inevitably happens, you are left with a CSV file that can still be accessed quickly in the case of an emergency... which is the primary reason I do not EVER use binary storage for essential data that should be quickly accessible even when the database breaks due to incompetent programming.\n\n\nYes, the CSV file would have to be re-indexed every time you made changes to it in a spread sheet program, but that is no different than having to re-index a binary database after the index\/table gets corrupted\/deleted\/out-of-sync\/etc.\/etc..","Q_Score":3,"Tags":"python,csv,web-applications,flask","A_Id":64239216,"CreationDate":"2014-06-06T00:11:00.000","Title":"Somthing wrong with using CSV as database for a webapp?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am using Flask to make a small webapp to manage a group project, in this website I need to manage attendances, and also meetings reports. I don't have the time to get into SQLAlchemy, so I need to know what might be the bad things about using CSV as a database.","AnswerCount":4,"Available Count":2,"Score":0.049958375,"is_accepted":false,"ViewCount":3024,"Q_Id":24072231,"Users Score":1,"Answer":"I think there's nothing wrong with that as long as you abstract away from it. I.e. make sure you have a clean separation between what you write and how you implement i . That will bloat your code a bit, but it will make sure you can swap your CSV storage in a matter of days.\nI.e. pretend that you can persist your data as if you're keeping it in memory. Don't write \"openCSVFile\" in you flask app. Use initPersistence(). Don't write \"csvFile.appendRecord()\". Use \"persister.saveNewReport()\". When and if you actually realise CSV to be a bottleneck, you can just write a new persister plugin.\nThere are added benefits like you don't have to use a mock library in tests to make them faster. You just provide another persister.","Q_Score":3,"Tags":"python,csv,web-applications,flask","A_Id":47320760,"CreationDate":"2014-06-06T00:11:00.000","Title":"Somthing wrong with using CSV as database for a webapp?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have read a few posts on how to enable remote login to mysql. My question is: is this a safe way to access data remotely? \nI have a my sql db located at home (on Ubuntu 14.04) that I use for research purposes. I would like to run python scripts from my Macbook at work. I was able to remote login from my old windows OS using workbench connection (DNS ip). However the OS change has got me thinking what is the best\/most secure way to accomplish this task?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":49,"Q_Id":24112422,"Users Score":0,"Answer":"Use ssh to login to your home computer, setup authorized keys for it and disable password login. setup iptables on your linux machine if you don't have a firewall on your router, and disable traffic on all ports except 80 and 22 (ssh and internet). That should get you started.","Q_Score":0,"Tags":"python,mysql,ruby-on-rails","A_Id":24112483,"CreationDate":"2014-06-09T01:02:00.000","Title":"Best way to access data from mysql db on other non-local machines","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm trying to use the new excel integration module xlwings \nIt works like a charm under Anaconda 2.0 for python 2.7\nbut I'm getting this error under Anaconda 2.0 for python 3.4\nthe xlwings file does contain class Workbook so I don't understand why it can't import it\nwhen I simply use the xlwings file in my project for 3.4 it works just fine\nFile \"C:\\Users\\xxxxx\\AppData\\Local\\Continuum\\Anaconda3\\lib\\site-packages\\xlwings__init__.py\", line 1, in \n    from xlwings import Workbook, Range, Chart, version\nImportError: cannot import name 'Workbook'","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":2145,"Q_Id":24121692,"Users Score":3,"Answer":"In \"C:\\Users\\xxxxx\\AppData\\Local\\Continuum\\Anaconda3\\lib\\site-packages\\xlwings__init__.py\"\nTry  changing  from xlwings import Workbook, Range, Chart, __version__\nto from xlwings.xlwings import Workbook, Range, Chart, __version__","Q_Score":4,"Tags":"python,excel,xlwings","A_Id":24122113,"CreationDate":"2014-06-09T13:49:00.000","Title":"importing xlwings module into python 3.4","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"The question is pretty much in the header, but here are the specifics. For my senior design project we are going to be writing software to control some hardware and display diagnostics info on a web front. To accomplish this, I'm planning to use a combination of Python and nodejs. Theoretically, a python service script will communicate with the hardware via bacnet IP and log diagnostic info in an SQL database. The nodejs JavaScript server code will respond to webfront requests by querying the database and returning the relevant info. I'm pretty new to SQL, so my primary question is.. Is this possible? My second and more abstract questions would be... is this wise? And, is there any obvious advantage to using the same language on both ends, whether that language is Python, Java, or something else?","AnswerCount":3,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":1076,"Q_Id":24156992,"Users Score":0,"Answer":"Yes its possible.\nTwo applications with different languages using one database is almost exactly the same as one application using several connections to it, so you are probably already doing it. All the possible problems are exactly the same. The database won't even know whether the connections are made from one application or the other.","Q_Score":1,"Tags":"sql,node.js,python-2.7","A_Id":24157502,"CreationDate":"2014-06-11T07:25:00.000","Title":"Can two programs, written in different languages, connect to the same SQL database?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"The question is pretty much in the header, but here are the specifics. For my senior design project we are going to be writing software to control some hardware and display diagnostics info on a web front. To accomplish this, I'm planning to use a combination of Python and nodejs. Theoretically, a python service script will communicate with the hardware via bacnet IP and log diagnostic info in an SQL database. The nodejs JavaScript server code will respond to webfront requests by querying the database and returning the relevant info. I'm pretty new to SQL, so my primary question is.. Is this possible? My second and more abstract questions would be... is this wise? And, is there any obvious advantage to using the same language on both ends, whether that language is Python, Java, or something else?","AnswerCount":3,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":1076,"Q_Id":24156992,"Users Score":1,"Answer":"tl;dr\nYou can use any programming language that provides a client for the database server of your choice.\nTo the database server, as long as the client is communicating as per the server's requirements (that is, it is using the server's library, protocol, etc.), then there is no difference to what programming language or system is being used.\n\nThe database drivers provide a common abstract layer, providing a guarantee that the database server and the client are speaking the same language.\nThe programming language's interface to the database driver takes care of the language specifics - for example, providing syntax that conforms to the language; and on the opposite side it the driver will ensure that all commands are sent in the protocol that the server expects.\nSince drivers are such a core requirement, there are usually multiple drivers available for databases; and also because good database access is a core requirement for programmers, each language strives to have a \"standard\" API for all databases. For example Java has JDBC\nPython has the DB-API, .NET has ODBC (and ADO I believe, but I am not a .NET expert).\nThese are what the database drivers will conform to, so that it doesn't matter which database server you are using, you have one standard way to connect, one standard way to execute queries and one standard way to fetch results - in effect, making your life as a programmer easier.\nIn most cases, there is a reference driver (and API\/library) provided by the database vendor. It is usually in C, and it is also what the \"native\" client to the database uses.  For example the mysql client for the MySQL database server using the MySQL C drivers to connect, and it is the same driver that is used by the Python MySQLdb driver; which conforms to the Python DB-API.","Q_Score":1,"Tags":"sql,node.js,python-2.7","A_Id":24158115,"CreationDate":"2014-06-11T07:25:00.000","Title":"Can two programs, written in different languages, connect to the same SQL database?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a python script running on my server which accessed a database, executes a fetch query and runs a learning algorithm to classify and updates certain values and means depending on the query.\nI want to know if for some reason my server shuts down in between then my python script would shut down and my query lost.\nHow do i get to know where to continue from once I re-run the script and i want to carry on the updated means from the previous queries that have happened.","AnswerCount":1,"Available Count":1,"Score":0.3799489623,"is_accepted":false,"ViewCount":22,"Q_Id":24202386,"Users Score":2,"Answer":"First of all: the question is not really related to Python at all. It's a general problem.\nAnd the answer is simple: keep track of what your script does (in a file or directly in db). If it crashes continue from the last step.","Q_Score":0,"Tags":"python","A_Id":24202505,"CreationDate":"2014-06-13T09:45:00.000","Title":"Python re establishment after Server shuts down","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"How can I use Google Cloud Datastore stats object (in Python ) to get  the number of entities of one kind (i.e. Person) in my database satisfying a given constraint (i.e. age>20)?","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":68,"Q_Id":24227510,"Users Score":1,"Answer":"You can't, that's not what it's for at all. It's only for very broad-grained statistics about the number of each types in the datastore. It'll give you a rough estimate of how many Person objects there are in total, that's all.","Q_Score":0,"Tags":"python,google-app-engine,google-cloud-datastore","A_Id":24227785,"CreationDate":"2014-06-15T07:34:00.000","Title":"How to use Google Cloud Datastore Statistics","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I have a script in Python that retrieves data from a remote server into a MySQL database located on my computer (the one that runs the Python script).\nThis script is executed daily to retrieve fresh data into the MySQL database. I am using Workbench 6.0 for Windows 64.\nI want to add a web GUI to the system that will present some of the data on a web page. I would like to write it in PHP and for my PHP program to use the same MySQL database that my Python script uses. I would like to make it a web server later on so users can log in to the sever and use this web GUI.\nCan the PHP and the Python scripts use the same DB?\nIn the past I have worked with WAMP sever for PHP only. If I install WAMP on the sever, will it be able to use the same DB or can it cause a collision?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1052,"Q_Id":24227779,"Users Score":0,"Answer":"I'd comment, but I don't have enough rep. yet.  You should be able to start the Apache and PHP services separately from the WAMP tray icon.  If you can't, try this:\nYou should be able to use the WAMP menu on the tray icon to open WAMP's my.ini file.  In there, just change the port number from 3306 to something else (might as well use 3307) and save the file, then restart WAMP.  In the future, completely ignore WAMP's MySQL instance and just use the one that Python is connecting to.\nIf that still doesn't work, you might have Skype running.  By default, Skype listens on Port 80 for some bizarre reason.  Open Skype's settings, go to the \"Connection\" section and untick \"Use port 80 as an alternative for incoming connections.\"  Then try restarting WAMP again.","Q_Score":1,"Tags":"php,python,mysql,wamp","A_Id":24228304,"CreationDate":"2014-06-15T08:17:00.000","Title":"Python and PHP use the same mySQL database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm storing strings on the order of 150M. It's well-below the maximum size of strings in Redis, but I'm seeing a lot of different, conflicted opinions on the approach I should take, and no clear path.\nOn the one hand, I've seen that I should use a hash with small data chunks, and on the other hand, I've been told that leads to gapping, and that storing the whole string is most efficient.\nOn the one hand, I've seen that I could pass in the one massive string, or do a bunch of string-append operations to build it up. The latter seems like it might be more efficient than the former.\nI'm reading the data from elsewhere, so I'd rather not fill a local, physical file just so that I can pass a whole string. Obviously, it'd be better all around if I can chunk the input data, and feed it into Redis via appends. However, if this isn't efficient with Redis, it might take forever to feed all of the data, one chunk at a time. I'd try it, but I lack the experience, and it might be inefficient for a number of different reasons.\nThat being said, there's a lot of talk of \"small\" strings and \"large\" strings, but it's not clear what Redis considers an optimally \"small\" string. 512K, 1M, 8M?\nDoes anyone have any definitive remarks?\nI'd love it if I could just provide a file-like object or generator to redis-py, but that's more language-specific than I meant this question to be, and most likely impossible for the protocol, anyway: it'd just require internal chunking of the data, anyway, when it's probably better to just impose this on the developer.","AnswerCount":1,"Available Count":1,"Score":0.3799489623,"is_accepted":false,"ViewCount":2349,"Q_Id":24320040,"Users Score":2,"Answer":"One option would be:\nStoring data as long list of chunks\n\nstore data in List - this allows storing the content as sequence of chunks as well as desctroying whole list in one step\nstore the data using pipeline contenxt manager to ensure, you are the only one, who writes at that moment.\nbe aware, that Redis is always processing single request and all others are blocked for that moment. With large files, which take time to write you can not only slow other clients down, but you are also likely to exceed max execution time (see config for this value).\n\nStore data in randomly named list with known pointer\nAlternative approach, also using list, would be to invent random list name, write content chunk by chunk into it, and when you are done, update value in known key in Redis pointing to this randomly named list. Do not forget to remove old one, this can be done from your code, but you might use expiration if it seems usable in your use case.","Q_Score":4,"Tags":"python,redis","A_Id":24321923,"CreationDate":"2014-06-20T04:36:00.000","Title":"Best way to store large string in Redis... Getting mixed signals","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm looking to insert the current system timestamp into a field on a database. I don't want to use the server side now() function and need to use the python client's system timestamp. What MySQL datatype can store this value, and how should I insert it? Is time.time() sufficient?","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":3202,"Q_Id":24367155,"Users Score":1,"Answer":"time.time() is a float, if a resolution of one second is enough you can just truncate it and store it as an INTEGER.","Q_Score":0,"Tags":"python,mysql,python-3.x,timestamp","A_Id":24368972,"CreationDate":"2014-06-23T13:26:00.000","Title":"Inserting a unix timestamp into MySQL from Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm used to having a remote server I can use via ssh but I am looking at using Amazon Web Services for a new project to give me better performance and resilience at reduced costs but I'm struggling to understand how to  use it.\nThis is what I want to do:\nFirst-time:\n\nCreate a Postgres db\nConnect to Amazon Server\nDownload code to server\n\nOnce a month:\n\nDownload large data file to server\nRun code (written in python) to load database with data\nRun code (written in Java) to create a Lucene Search Index file from data in the database\n\nContinuously:\n\nRun Java code in servlet container, this will use lucense search index file but DOES NOT require access to the database.\n\nNote: Technically I could create do the database population locally the trouble is the resultant lucene index file is about 5GB and I dont have a good enough Internet connection \nto upload a file of that size to Amazon.\nAll that I have managed to do so far is create a Postgres database but I don't understand how to connect to it or get a ssh\/telnet connection to my server (I requested a Direct Connect but this seems to be a different service).\nUpdate so far\nFYI:\n\nSo I created a Postgres database using RDS\nI created a Ubuntu linux installation using EC2\nI connected to the linux installation using ssh\nI installed required software (using apt-get)  \nI downloaded data file to my linux installation\n\nI think according to the installation should be able to connect to my Postgres db from my EC2 instance and even from my local machine however in both cases it just times out.\n* Update 2 **\nProbably security related but I cannot for the life of me understand what I'm meant to do with security groups ands why they don't make the EC2 instance able to talk to my database by default.\nIve checked both RDS and EC2 have the3 same vpc id, and both are in the same availability zone. Postgres is using port 5432 (not 3306) but havent been able to access it yet. So taking my working EC2 instance as the starting point should I create a new security group before creating a database, and if so what values do I need to put into it so I can access the db with psql from within my ec2 ssh session - thats all that is holding me up for now and all I need to do \n* Update 3 *\nAt last I have access to my database, my database had three security groups ( I think the other two were created when I created a new EC2 instance) I removed two of them and in the remaining on the inbound tab I set rule to\n\nAll Traffic\nPorts 0-65535\nProtocol All\nIPAddress 0.0.0.0\/0\n\n(The outbound tab already had the same rule) and it worked !\nI realize this is not the most secure setup but at least its progress.\nI assume to only allow access from my EC2 instance I can change the IPAddress of the inbound rule but I don't how to calculate the CIDR for the ipaddress ?\nMy new problem is having successfully downloaded my datafile to my EC2 instance I am unable to unzip it because I don't not have enough diskspace. I assume I have to use S3 Ive created a bucket but how do I make it visible as diskspace from my EC2 instance so I can\n\nMove my datafile to it\nUnzip the datafile into it\nRun my code against the unzipped datafile to load the database\n\n(Note the datafile is an Xml format and has to be processed with custom code to get it into the database it cannot just be loaded directly into the database using some generic tool)  \nUpdate 4\nS3 is the wrong solution for me instead I can use EBS which is basically disc storage accessible not as a service but by clicking Volumes in EC2 Console. Ensure create the volume in the same Availability zone as the instance, there maybe more than one in each location, for example my EC2 instance was created in eu-west-1a but the first time I created a volume it was in eu-west-1b and therefore could not be used.\nThen attach volume to instance\nBut I cannot see the volume from the linux commandline, seems there is something else required.\nUpdate 5\nOkay, have to format the disk and mount it in linux for it to work\nI now have my code for uploading the data to database working but it is running incredibly slow, much slower than my cheap local server I have at home. I'm guessing that because the data is being loaded one record at a time that the bottleneck is not the micro database but my micro instance, looks like I need to redo with a more expensive instance\nUpdate 6\nUpdated to a large Computative instance still very slow. Im now thinking the issue is the network latency between server and database perhaps need to install a postgres server directly onto my instance to cut that part out.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":186,"Q_Id":24367485,"Users Score":0,"Answer":"First-time:\nCreate a Postgres db - Depending on size(small or large), might want RDS or Redshift\nConnect to Amazon Server - EC2\nDownload code to server - upload your programs to an S3 bucket\nOnce a month:\nDownload large data file to server - Move data to S3, if using redshift data can be loaded directly from s3 to redshift\nRun code (written in python) to load database with data \nRun code (written in Java) to create a Lucene Search Index file from data in the database - might want to look into EMR with this\nContinuously:\nRun Java code in servlet container, this will use lucense search index file but DOES NOT require access to the database - If you have a java WAR file, you can host this using Elasticbean stalk\nIn order to connect to your database, you must make sure the security group allows for this connection, and for an ec2 you must make sure port 22 is open to your IP to conncet to it. It sounds like the security group for RDS isn't opening up port 3306.","Q_Score":0,"Tags":"java,python,amazon-web-services,amazon-ec2","A_Id":24373021,"CreationDate":"2014-06-23T13:40:00.000","Title":"How do i get started with Amazon Web Services for this scenario?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I can't connect with mysql and I can't do \"python manage.py syncdb\" on it\nhow to connect with mysql in django and django-cms without any error?","AnswerCount":2,"Available Count":1,"Score":0.2913126125,"is_accepted":false,"ViewCount":9227,"Q_Id":24380269,"Users Score":3,"Answer":"This is an error message you get if MySQLdb isn't installed on your computer.\nThe easiest way to install it would be by entering pip install MySQL-python into your command line.","Q_Score":1,"Tags":"python,mysql,django,django-cms","A_Id":24380525,"CreationDate":"2014-06-24T06:59:00.000","Title":"Getting \u201cError loading MySQLdb module: No module named MySQLdb\u201d in django-cms","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"There are Python libraries that allow to communicate with a database. Of course, to use these libraries there should be an installed and running database server on the computer (python cannot communicate with something that does not exist).\nMy question is whether the above written is applicable to the sqlite3 library. Can one say that this library does not need any database to be installed (and running) on the computer? Can one say that sqlite3 needs only a file system?","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":878,"Q_Id":24410124,"Users Score":0,"Answer":"No, sqlite package is part of Python standard library and as soon as you have Python installed, you may use sqlite functionality.\nMartijnPieters noted, the actual shared library is not technically part of Python (this was my a bit oversimplified answer) but comes as shared library, which has to be installed too.\nPractically speaking, if you manage installing Python, you have the sqlite available for your Python code.\nAs OP asked for for a need to install sqlite separately, I will not speculate on how to install Python, which is not able to work with it.","Q_Score":2,"Tags":"python,database,sqlite","A_Id":24410155,"CreationDate":"2014-06-25T13:30:00.000","Title":"Does python sqlite3 library need sqlite to be installed?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am using pandas to organize and manipulate data I am getting from the twitter API. The 'id' key returns a very long integer (int64) that pandas has no problem handling (i.e. 481496718320496643). \nHowever, when I send to SQL:\ndf.to_sql('Tweets', conn, flavor='sqlite', if_exists='append', index=False)\nI now have tweet id: 481496718320496640 or something close to that number.\nI converted the tweet id to str but Pandas SQLite Driver \/ SQLite still messes with the number. The data type in the SQLite database is [tweet_id] INTEGER. What is going on and how do I prevent this from happening?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":160,"Q_Id":24416140,"Users Score":0,"Answer":"I have found the issue -- I am using SQLite Manager (Firefox Plugin) as a SQLite client. For whatever reason, SQLite Manager displays the tweet IDs incorrectly even though they are properly stored (i.e. when I query, I get the desired values). Very strange I must say. I downloaded a different SQLite client to view the data and it displays properly.","Q_Score":0,"Tags":"python,sqlite,pandas","A_Id":24419432,"CreationDate":"2014-06-25T18:39:00.000","Title":"Long integer values in pandas dataframe change when sent to SQLite database using to_sql","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"This might sound like a bit of an odd question - but is it possible to load data from a (in this case MySQL) table to be used in Django without the need for a model to be present?\nI realise this isn't really the Django way, but given my current scenario, I don't really know how better to solve the problem.\nI'm working on a site, which for one aspect makes use of a table of data which has been bought from a third party. The columns of interest are liklely to remain stable, however the structure of the table could change with subsequent updates to the data set. The table is also massive (in terms of columns) - so I'm not keen on typing out each field in the model one-by-one. I'd also like to leave the table intact - so coming up with a model which represents the set of columns I am interested in is not really an ideal solution.\nIdeally, I want to have this table in a database somewhere (possibly separate to the main site database) and access its contents directly using SQL.","AnswerCount":3,"Available Count":1,"Score":0.0665680765,"is_accepted":false,"ViewCount":1496,"Q_Id":24423645,"Users Score":1,"Answer":"There is one feature called  inspectdb in Django. for legacy databases like MySQL , it creates models automatically by inspecting your db tables. it stored in our app files as models.py. so we don't need to type all column manually.But read the documentation carefully before creating the models because it may affect the DB data ...i hope this will be useful for you.","Q_Score":2,"Tags":"python,mysql,django,webproject","A_Id":44363554,"CreationDate":"2014-06-26T06:19:00.000","Title":"Loading data from a (MySQL) database into Django without models","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am developing a web app based on the Google App Engine. \nIt has some hundreds of places (name, latitude, longitude) stored in the Data Store. \nMy aim is to show them on google map. \nSince they are many I have registered a javascript function to the idle event of the map and, when executed, it posts the map boundaries (minLat,maxLat,minLng,maxLng) to a request handler which should retrieve from the data store only the places in the specified boundaries.\nThe problem is that it doesn't allow me to execute more than one inequality in the query (i.e. Place.latminLat, Place.lntminLng).\nHow should I do that? (trying also to minimize the number of required queries)","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":144,"Q_Id":24497219,"Users Score":0,"Answer":"You didn't say how frequently the data points are updated, but assuming 1) they're updated infrequently and 2) there are only hundreds of points, then consider just querying them all once, and storing them sorted in memcache.  Then your handler function would just fetch from memcache and filter in memory.\nThis wouldn't scale indefinitely but it would likely be cheaper than querying the Datastore every time, due to the way App Engine pricing works.","Q_Score":0,"Tags":"javascript,python,google-maps,google-app-engine","A_Id":24501164,"CreationDate":"2014-06-30T19:09:00.000","Title":"Google App Engine NDB Query on Many Locations","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I'm used to creating connections using MySQLdb directly so I'm not sure this is at all possible using sqlalchemy, but is there a way to get the mysql connection thread id from a mysql Session a la MySQLdb.connection.thread_id()? I've been digging through and can't seem to find a way to access it. I'm not creating a connection from the Engine directly, and would like to avoid doing so.\nFor reference this is a single-thread application, I just need to get the mysql thread id for other purposes.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":707,"Q_Id":24500665,"Users Score":3,"Answer":"session.connection().connection.thread_id()","Q_Score":3,"Tags":"python,mysql,sqlalchemy,mysql-python","A_Id":24614258,"CreationDate":"2014-07-01T00:02:00.000","Title":"Getting a mysql thread id from sqlalchemy Session","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I made a program that receives user input and stores it on a MySQL database. I want to implement this program on several computers so users can upload information to the same database simoultaneously. The database is very simple, it has just seven columns and the user will only enter four of them.\nThere would be around two-three hundred computers uploading information (not always at the same time but it can happen). How reliable is this? Is that even possible?\nIt's my first script ever so I appreciate if you could point me in the right direction. Thanks in advance.","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":1497,"Q_Id":24502362,"Users Score":0,"Answer":"Yes, it is possible to have up to that many number of mySQL connectins. It depends on a few variables. The maximum number of connections MySQL can support depends on the quality of the thread library on a given platform, the amount of RAM available, how much RAM is used for each connection, the workload from each connection, and the desired response time.\nThe number of connections permitted is controlled by the max_connections system variable. The default value is 151 to improve performance when MySQL is used with the Apache Web server.\nThe important part is to properly handle the connections and closing them appropriately. You do not want redundant connections occurring, as it can cause slow-down issues in the long run. Make sure when coding that you properly close connections.","Q_Score":0,"Tags":"mysql,python-2.7,mysql-python","A_Id":24502420,"CreationDate":"2014-07-01T04:16:00.000","Title":"simultaneous connections to a mysql database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I made a program that receives user input and stores it on a MySQL database. I want to implement this program on several computers so users can upload information to the same database simoultaneously. The database is very simple, it has just seven columns and the user will only enter four of them.\nThere would be around two-three hundred computers uploading information (not always at the same time but it can happen). How reliable is this? Is that even possible?\nIt's my first script ever so I appreciate if you could point me in the right direction. Thanks in advance.","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":1497,"Q_Id":24502362,"Users Score":0,"Answer":"Having simultaneous connections from the same script depends on how you're processing the requests. The typical choices are by forking a new Python process (usually handled by a webserver), or by handling all the requests with a single process.\nIf you're forking processes (new process each request):\nA single MySQL connection should be perfectly fine (since the total number of active connections will be equal to the number of requests you're handling). \nYou typically shouldn't worry about multiple connections since a single MySQL connection (and the server), can handle loads much higher than that (completely dependent upon the hardware of course). In which case, as @GeorgeDaniel said, it's more important that you focus on controlling how many active processes you have and making sure they don't strain your computer.\nIf you're running a single process:\nYet again, a single MySQL connection should be fast enough for all of those requests. If you want, you can look into grouping the inserts together, as well as multiple connections.\nMySQL is fast and should be able to easily handle 200+ simultaneous connections that are writing\/reading, regardless of how many active connections you have open. And yet again, the performance you get from MySQL is completely dependent upon your hardware.","Q_Score":0,"Tags":"mysql,python-2.7,mysql-python","A_Id":24502484,"CreationDate":"2014-07-01T04:16:00.000","Title":"simultaneous connections to a mysql database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm attempting to store information from a decompiled file in Dynamo.\nI have all of the files stored in s3 however I would like to change some of that.\nI have an object id with properties such as a date, etc which I know how to create a table of in dynamo. My issue is that each object also contains images, text files, and the original file. I would like to have the key for s3 for the original file in the properties of the file:\nEx: FileX, date, originalfileLoc, etc, images pointer, text pointer.\nI looked online but I'm confused how to do the nesting. Does anyone know of any good examples? Is there another way? I assume I create an images and a text table. Each with the id and all of the file's s3 keys. Any example code of how to create the link itself?  \nI'm using python boto btw to do this.","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":477,"Q_Id":24520176,"Users Score":0,"Answer":"From what you described, I think you just need to create one table with hashkey. The haskey should be object id. And you will have columns such as \"date\", \"image pointer\", \"text pointer\", etc.\nDynamoDB is schema-less so you don't need to create the columns explicitly. When you call getItem the server will return you a dictionary with column name as key and the value.\nBeing schema-less also means you can create new column dynamically. Assuming you already have a row in the table with only \"date\" column. now you want to add the \"image pointer\" column. you just need to call UpdateItem and gives it the hashkey and image-pointer key-value pair.","Q_Score":0,"Tags":"python,database,amazon-s3,amazon-dynamodb,boto","A_Id":24642053,"CreationDate":"2014-07-01T22:25:00.000","Title":"How to correctly nest tables in DynamoDb","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm attempting to store information from a decompiled file in Dynamo.\nI have all of the files stored in s3 however I would like to change some of that.\nI have an object id with properties such as a date, etc which I know how to create a table of in dynamo. My issue is that each object also contains images, text files, and the original file. I would like to have the key for s3 for the original file in the properties of the file:\nEx: FileX, date, originalfileLoc, etc, images pointer, text pointer.\nI looked online but I'm confused how to do the nesting. Does anyone know of any good examples? Is there another way? I assume I create an images and a text table. Each with the id and all of the file's s3 keys. Any example code of how to create the link itself?  \nI'm using python boto btw to do this.","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":477,"Q_Id":24520176,"Users Score":0,"Answer":"If you stay between the limits of Dynamodb of 64Kb per item.\nYou can have one item (row) per file.\nDynamoDB has String type (for file name, date, etc) and also a StringSet (SS) for list of attributes (for text files, images).\nFrom what you write I assume you are will only save pointers (keys) to binary data in the S3. \nYou could also save binary data and binary sets in DynamoDB but I believe you will reach the limit AND have an expensive solution in terms of throughput.","Q_Score":0,"Tags":"python,database,amazon-s3,amazon-dynamodb,boto","A_Id":24536208,"CreationDate":"2014-07-01T22:25:00.000","Title":"How to correctly nest tables in DynamoDb","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have made an online website which acts as the fronted for a database into which my customers can save sales information. So each customer logs onto the online website with their own credentials and only see their own sales records. The database comes in the form of SQL Server 2008.\nSome of these customers have a third party Windows tool on their PCs which itself acts as a fronted for a database with specific sales records. This tool is used by them for printing receipts. This tool comes with a Python interface which can be used to update the database, if the tool itself is not used. I've installed the tool on my PC and successfully added records to this tool's database by running a simple Python Script.\nAt the moment, customers are adding by hand sales information from my website to the tool on the PC. I would like to provide them with an automatic way of doing this. This syncing should only occur when the customer requests such a sync and indeed they have all requested that it should work so. This is to ensure that they get an opportunity to validate the information. \nHow might I solve this problem? Should I develop a PC application which they install on their local computer or can I do this via the browser? Either solution will need to execute Python code in order to update the database on their PC and then there are of course security issues.","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":995,"Q_Id":24611812,"Users Score":0,"Answer":"So in summary you have a website\/sql server application. Then some of your users have a separate local database with a python front end. And you need to bridge the two applications.\nYou can expose your sql server database with an rest api (using whatever tech of your choice).  Then create a python app that calls that api (either via a button or automatically scheduled) and then executes the needed python code for the reporting. \nAnother approach would be to add that needed reporting functionality into your web app. So if you look at the functionality of what the 3rd party database and reporting provides and add that functionality into your website so there's no longer a need to use that 3rd party application at all. \nThose are your two paths to go down based on on the info provided.","Q_Score":3,"Tags":"python,sql-server,browser,sync","A_Id":24659493,"CreationDate":"2014-07-07T13:32:00.000","Title":"Syncing PC data with online data","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Goal: Take\/attach pictures in a PhoneGap application and send a public URL for each picture to a Google Cloud SQL database.\nQuestion 1: Is there a way to create a Google Cloud Storage object from a base64 encoded image (in Python), then upload that object to a bucket and return a public link?\nI'm looking to use PhoneGap to send images to a Python Google App Engine application, then have that application send the images to a Google Cloud Storage bucket I have set up, then return a public link back to the PhoneGap app. These images can either be taken directly from the app, or attached from existing photo's on the user's device.\nI use PhoneGap's FileTransfer plugin to upload the images to GAE, which are sent as base64 encoded images (this isn't something I can control).\nBased on what I've found in Google Docs, I can upload the images to Blobstore; however, it requires <input type='file'> elements in a form.  I don't have 'file' input elements; I just take the image URI returned from PhoneGap's camera object and display a thumbnail of the picture that was taken (or attached).\nQuestion 2: Is it possible to have an <input type='file'> element and control it's value? As in, is it possible to set it's value based on whether the user chooses a file, or takes a picture?\nThanks in advance!","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":620,"Q_Id":24655877,"Users Score":0,"Answer":"Yes, that is a fine use for GAE and GCS.  You do not need an <input type=file>, per se.  You can just set up POST parameters in your call to your GAE url.  Make sure you send a hidden key as well, and work from SSL-secured urls, to prevent spammers from posting to your app.","Q_Score":1,"Tags":"python,google-app-engine,cordova,google-cloud-storage","A_Id":24657475,"CreationDate":"2014-07-09T14:05:00.000","Title":"Using PhoneGap + Google App Engine to Upload and Save Images","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"So I have a string in Python that contains like 500 SQL INSERT queries, separated by ;. This is purely for performance reasons, otherwise I would execute individual queries and I wouldn't have this problem.\nWhen I run my SQL query, Python throws: IntegrityError: (1062, \"Duplicate entry 'http:\/\/domain.com' for key 'PRIMARY'\")\nLets say on the first query of 500, the error is thrown. How can I make sure those other 499 queries are executed on my database?\nIf I used a try and except, sure the exception wouldn't be raised, but the rest of my statement wouldn't be executed. Or would it, since Python sends it all in 1 big combined string to MySQL?\nAny ideas?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":828,"Q_Id":24664413,"Users Score":0,"Answer":"For anyone that cares, the ON DUPLICATE KEY UPDATE SQL command was what I ended up using.","Q_Score":0,"Tags":"python,mysql,sql","A_Id":24666569,"CreationDate":"2014-07-09T21:55:00.000","Title":"Python Ignore MySQL IntegrityError when trying to add duplicate entry with a Primary key","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I apologize if this has been asked already, or if this is answered somewhere else. \nAnyways, I'm working on a project that, in short, stores image metadata and then allows the user to search said metadata (which resembles a long list of key-value pairs). This wouldn't be too big of an issue if the metadata was standardized. However, the problem is that for any given image in the database, there is any number of key\/values in its metadata. Also there is no standard list of what keys there are. \nBasically, I need to find a way to store a dictionary for each model, but with arbitrary key\/value pairs. And I need to be able to query them. And the organization I'm working for is planning on uploading thousands of images to this program, so it has to query reasonably fast. \nI have one model in my database, an image model, with a filefield. \nSo, I'm in between two options, and I could really use some help from people with more experience on choosing the best one (or any other solutions that would work better)\n\nUsing a traditional relational database like MySql, and creating a separate model with a foreignkey to the image model, a key field, and a value field. Then, when I need to query the data, I'll ask for every instance of this separate table that relates to an image, and then query those rows for the key\/value combination I need.\nUsing something like MongoDB, with django-toolbox and its DictField to store the metadata. Then, when I need to query, I'll access the dict and search it for the key\/value combination I need. \n\nWhile I feel like 1 would be much better in terms of query time, each image may have up to 40 key\/values of metadata, and that makes me worry about that separate \"dictionary\" table growing far too large if there's thousands of images. \nAny advice would be much appreciated. Thanks!","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":992,"Q_Id":24688388,"Users Score":0,"Answer":"In a Django project you've got 4 alternatives for this kind of problem, in no particular order:\n\nusing PostgreSQL, you can use the hstore field type, that's basically a pickled python dictionary. It's not very helpful in terms of querying it, but does its job saving your data.\nusing Django-NoRel with mongodb you get the ListField field type that does the same thing and can be queried just like anything in mongo. (option 2)\nusing Django-eav to create an entity attribute value store with your data. Elegant solution but painfully slow queries. (option 1)\nstoring your data as a json string in a long enough TextField and creating your own functions to serializing and deserializing the data, without thinking on being able to make a query over it.\n\nIn my own experience, if you by any chance need to query over the data, your option two is by far the best choice. EAV in Django, without composite keys, is painful.","Q_Score":0,"Tags":"python,mysql,django,mongodb,database","A_Id":24690665,"CreationDate":"2014-07-11T00:29:00.000","Title":"Django: storing\/querying a dictionary-like data set?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I faced with problem:\nThere is a big old database on microsoft sql server (with triggers, functions etc.). I am writing C# app on top of this db. Most of work is a \"experiments\" like this:\nWrite a part of functionality and see if it works in old Delphi app (i.e. inserted data in C# loaded correctly in Delphi).\nSo I need tool, that can determine which fields of each table is used or not (used in my queries). I think to write python script with sql syntax analyser or just using regular expressions.\nWhat solution would you recommend?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":70,"Q_Id":24690101,"Users Score":0,"Answer":"You can run a trace in SQL Profiler to see the queries being executed on the server.","Q_Score":0,"Tags":"c#,python,sql,tsql","A_Id":24690183,"CreationDate":"2014-07-11T04:26:00.000","Title":"Analyse sql queries text","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"So, locally I've changed my models a few times and used South to get everything working.  I have a postgres database to power my live site, and one model keeps triggering a column mainsite_message.spam does not exist error.  But when I run heroku run python manage.py migrate mainsite from the terminal, I get Nothing to migrate.  All my migrations have been pushed.","AnswerCount":3,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":1178,"Q_Id":24697420,"Users Score":0,"Answer":"I presume that you have created a migration to add mainsite_message.spam to the schema. Have you made sure that this migration is in your git repository?\nIf you type git status you should see untracked files. If the migration is untracked you need to git add path_to_migration and then push it to Heroku before you can run it there.","Q_Score":1,"Tags":"python,django,postgresql,heroku","A_Id":24698874,"CreationDate":"2014-07-11T12:11:00.000","Title":"Add a column to heroku postgres database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"So, locally I've changed my models a few times and used South to get everything working.  I have a postgres database to power my live site, and one model keeps triggering a column mainsite_message.spam does not exist error.  But when I run heroku run python manage.py migrate mainsite from the terminal, I get Nothing to migrate.  All my migrations have been pushed.","AnswerCount":3,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":1178,"Q_Id":24697420,"Users Score":0,"Answer":"Did you run schemamigration before? If yes, go to your database and take a look at your table  \"south_migrationhistory\" there you can see what happened.\nIf you already did the steps above you should try to open your migration file and take a look as well, there you can find if the creation column is specified or not!","Q_Score":1,"Tags":"python,django,postgresql,heroku","A_Id":24697852,"CreationDate":"2014-07-11T12:11:00.000","Title":"Add a column to heroku postgres database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm not sure how to best phrase this question: \nI would like to UPDATE, ADD, or DELETE information in an SQLite3 Table, but I don't want this data to be written to disk yet. I would still like to be able to \nSELECT the data, and get the updated information, but then I want to choose to either rollback or commit. \nIs this possible? Will the SELECT get the data before the UPDATE or after? Or must I rollback or commit before the next statement?","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":91,"Q_Id":24707471,"Users Score":0,"Answer":"If you explicitly need to commit multiple times throughout the code, and you are worried about the performance times of transactions, you could always build the database in memory db=sqlite3.connect(':memory:') and then dump it's contents to disk when all the time-critical aspects of the program have been completed. I.e the end of the script.","Q_Score":1,"Tags":"python,sqlite","A_Id":24707793,"CreationDate":"2014-07-11T22:20:00.000","Title":"Can I Stage data to memory SELECT, then choose to rollback, or commit in sqlite3? python 2.7","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I don't have access PHP server nor database like Mysql on machine I'll be working on. Would it be feasible to use Python instead of PHP and flat file database instead of Mysql? I'm not too concerned about performance  or scalability. It's not like I'm going to create next facebook. I just want to load data from server and show it on webpage and possibly handle some input forms. Also is there any major flaw with my reasoning? Or is there any other way to circumvent lack of PHP and database on server?","AnswerCount":4,"Available Count":2,"Score":0.049958375,"is_accepted":false,"ViewCount":1786,"Q_Id":24727096,"Users Score":1,"Answer":"Python comes bundled with sqlite3 module that gives access to SQLite databases. The only downside is that it is pretty much possible for just one thread can have write locks to it at any given moment.","Q_Score":0,"Tags":"python,web","A_Id":24727209,"CreationDate":"2014-07-13T21:21:00.000","Title":"Using Python and flat file database for server-side","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I don't have access PHP server nor database like Mysql on machine I'll be working on. Would it be feasible to use Python instead of PHP and flat file database instead of Mysql? I'm not too concerned about performance  or scalability. It's not like I'm going to create next facebook. I just want to load data from server and show it on webpage and possibly handle some input forms. Also is there any major flaw with my reasoning? Or is there any other way to circumvent lack of PHP and database on server?","AnswerCount":4,"Available Count":2,"Score":0.049958375,"is_accepted":false,"ViewCount":1786,"Q_Id":24727096,"Users Score":1,"Answer":"There are many ways to serve Python applications, but you should probably look at something that does this using the WSGI standard. Many frameworks will let you do this e.g: Pyramid, Pylons, Django, .....\nIf you haven't picked one then it would be worth looking at your long term requirements and also what you already know.\nIn terms of DB, there are many choices. SQLlite has been mentioned, but there are many other DBs that don't require a server process. If you're only storing a small amount of data then flat files may work for you, but anything bigger or more relational, then look at SQLlite.","Q_Score":0,"Tags":"python,web","A_Id":24727365,"CreationDate":"2014-07-13T21:21:00.000","Title":"Using Python and flat file database for server-side","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I need to be able to query documents that have a date field between some range, but sometimes in my dataset the year doesn't matter (this is represented with a boolean flag in the mongo document).\nSo, for example, I might have a document for Christmas (12\/25-- year doesn't matter) and another document for 2014 World Cup Final Match (8\/13\/2014). If the user searches for dates between 8\/1\/2014 and 12\/31\/2014, both of those documents should match, but another document for 2010 World Cup Final Match would not.\nAll approaches I've gotten to work so far have used a complicated nesting of $and and $or statements, which ends up being too slow for production, even with indexes set appropriately. Is there a simple or ideal way to handle this kind of conditional date searching in mongo?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":61,"Q_Id":24728191,"Users Score":0,"Answer":"For me you have to store specific values you'll search on, and index them.\nFor example, alongside with the date, you may store \"year\", \"month\", and \"day\", index on \"month\" and \"day\", and do your queries on it.\nYou may want to store them as \"y\", \"m\", and \"d\" to gain some bytes (That's sad, I know).","Q_Score":0,"Tags":"python,mongodb","A_Id":24729803,"CreationDate":"2014-07-14T00:41:00.000","Title":"Mongo query on custom date system","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm using matplotlib and MySQLdb to create some graphs from a MySQL database. For example, the number of unique visitors in a given time period, grouped by periods of say, 1 hours. So, there'll be a bunch of (Time, visits in 1-hour period near that time) points.\nI have a table as (ip, visit_time) where each ip can occur multiple times.\nMy question is should I run a single query and then process the results (remove duplicates, do the counting etc.), or should I run multiple SQL queries (for example, for 1 day period, there will be 24 queries for finding out the number of visits in each hour). Which will be faster and more efficient?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":86,"Q_Id":24776000,"Users Score":2,"Answer":"Generally Database queries should be faster than python for two reasons:\n\nDatabases are optimised to work with data, and they will optimise a high level abstraction language like SQL in order to get the best performance, while python might be fast but doesn't have to be\nRunning SQL analyses the data at the source and you don't need to transfer it at first.\n\nThat being said, there might be some extremely complex queries which could be faster in python but this doesn't seem the case for your. Also the more you squash the data with sql the smaller and easier the algorithm in python will be.\nAt last, I don't know your queries, but it should be possible to run them for all 24h at once including the removing duplicates and counting.","Q_Score":1,"Tags":"python,mysql,sql","A_Id":24776157,"CreationDate":"2014-07-16T08:36:00.000","Title":"Python and MySQL - which to use more?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a folder with a large number of Excel workbooks.  Is there a way to convert every file in this folder into a CSV file using Python's xlrd, xlutiles, and xlsxWriter?\nI would like the newly converted CSV files to have the extension '_convert.csv'.\nOTHERWISE...\nIs there a way to merge all the Excel workbooks in the folder to create one large file?\nI've been searching for ways to do both, but nothing has worked...","AnswerCount":5,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":2934,"Q_Id":24785824,"Users Score":0,"Answer":"Look at openoffice's python library. Although, I suspect openoffice would support MS document files. \nPython has no native support for Excel file.","Q_Score":1,"Tags":"python,csv,xlrd,xlsxwriter","A_Id":24785891,"CreationDate":"2014-07-16T16:20:00.000","Title":"Converting a folder of Excel files into CSV files\/Merge Excel Workbooks","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"When compiling documentation using Sphinx, I got the error AttributeError: 'str' object has no attribute 'worksheets'. How do I fix this?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":466,"Q_Id":24790239,"Users Score":0,"Answer":"You're getting the error because you don't have the most recent iPython installed. You probably installed it with sudo apt-get install ipython, but you should upgrade using sudo pip install ipython --upgrade and then making sure that the previous installation was removed by running sudo apt-get remove ipython.","Q_Score":0,"Tags":"ipython,python-sphinx","A_Id":24790240,"CreationDate":"2014-07-16T20:38:00.000","Title":"Compiling Sphinx with iPython doc error \"AttributeError: 'str' object has no attribute 'worksheets'\"","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I currently have a Raspberry Pi running Iperf non stop and collecting results. \nAfter collecting results it uploads the bandwidth tests to MySQL. \nIs there a way to automatically refresh the table to which the data is added?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":726,"Q_Id":24791510,"Users Score":0,"Answer":"Is your goal is to use MySQL workbench to build a live-view of your data ? If so I don't think you're using the right tools.\nYou may just use ElasticSearch to store your data and Kibana to display it, this way you'll have free graphs and charts of your stored data, and auto-refresh (based on an interval, not on events).\nYou also may take a look a Grafana, an event more specialized tool in storing \/ representing graphs of values.\nBut if you really want to store your data on MySQL, you may not want to use MySQL Workbench as a user interface, it's a developper tool to build your database. You may however build a graphical interface from scratch, and send it an event when you're updating your tables so it refreshes itself, but it's a lot of work that Kibana\/Grafana does for you.","Q_Score":0,"Tags":"python,mysql","A_Id":24795785,"CreationDate":"2014-07-16T21:57:00.000","Title":"MySQL WorkBench How to automatically re run query?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm doing data analytics on medium sized data (2GB, 20Mio records) and on the current machine it hardly fits into memory. Windows 7 slows down considerably when reaching 3GB occupation on this 4 GB machine. Most of my current analysis need to iterate over all records and consider properties of groups of records determined by some GroupID.\nHow can approach this task? My current method is to load it into SQLite and iterate by row. I build the groups in-memory, but this too grows quite large.\nI had the following ideas, but maybe you can suggest better approaches:\n\nsort SQLite table by GroupID so that groups come in together\nstore data somehow column-wise so that I don't have to read all columns\nserialize data to parse it faster with Python?\n\nThese ideas seem hard to combine for me :( What should I do?\n(PS: Hardware upgrades are hard to get. Admin right are cumbersome, too)","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":246,"Q_Id":24866113,"Users Score":1,"Answer":"It's hard to say anything without knowing more about the data & aggregation you are trying to do, but definitely don't do serialize data to parse it faster with Python -- most probably that's not where the problem is. And probably not store data somehow column-wise so that I don't have to read all columns.  \nsort SQLite table by GroupID so that groups come in together <- this sounds like a good approach. But lot of aggregations (like count, average, sum etc.) don't require this. In this type of aggregation, you can simply hold a map of (key, aggregation), and iterate through the rows and iteratively apply them to the aggregation (and throw the row away).   \nAre you currently gathering all rows that belong to a group in-memory and then doing the aggregation? If so, you might just need to change the code so that you do the aggregation as you read the rows.   \nEDIT:  In response to the comment:\nIf that's the case, then I'd go for sorting. SQL might be an overkill though if all you do is sort. Maybe you can just write the sorted file on disk? Once you do that you could look into parallilizing. Essentially you'll have one process reading the sorted file (which you don't want to parallelize as long as you don't do distributed processing), which packages one group worth of data and sends it to a pool of processes (the number of processes should be fixed to some number which you tune, to avoid memory shortage) which does the rest of processing.","Q_Score":2,"Tags":"python,database","A_Id":24866662,"CreationDate":"2014-07-21T13:18:00.000","Title":"Iterate over large data fast with Python?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am working on a python app that uses python 2.4, postgres 8.2 and old versions of pygresql, xlrd, etc. Because of this it is quite a pain to use, and has to be used in a windows xp VM. There are other problems such as the version of xlrd doesn't support .xlsx files, but the new version of xlrd doesn't work with python 2.4, understandably.\nI recently made a branch called 'upgrade' where I started to try to get it working with up to date versions of the libraries (python 2.7), for instance unicode handling has changed a bit so required some changes here and there.\nMost of the work I'm doing on the app should work in both environments, but it's nicer to work on the upgrade branch because it doesn't need to run in a vm. \nSo my question is how can I make commits using the upgrade branch but then apply them to the master branch so they will still apply to the old version of the software the client is using? I realise I can cherry pick commits off the upgrade branch onto master but it seems a bit wrong, having commits in both branches. I'm thinking maybe I should be rebasing the upgrade branch so it is always branching off head after the most recent commits, but then that would mean committing to the master branch which means working in a VM.\nHope this makes some kind of sense, I'll try and do some diagrams if not.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":77,"Q_Id":24908188,"Users Score":0,"Answer":"IMHO you should probably commit in your master branch, then rebase your upgrade branch, it will make more sense in your repository history.\nIf those commits are working on both environments, you should use a different branch based on the master one, so you can work out on the newer version of python, then merge it in the master, then rebase your upgrade branch.","Q_Score":0,"Tags":"python,git,version-control,branching-and-merging","A_Id":24913304,"CreationDate":"2014-07-23T10:36:00.000","Title":"Managing a different python version as a branch in git","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I want to order a large SQLite table and write the result into another table. This is because I need to iterate in some order and ordering takes a very long time on that big table.\nCan I rely in a (Python) iterator giving my the rows in the same order as I INSERTed them? Is there a way to guarantee that? (I heard comments that due to caching the order might break)","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":46,"Q_Id":24909851,"Users Score":2,"Answer":"I think you are approaching this wrong. If it is taking too long to extract data in a certain order from a table in any SQL database, that is a sign that you need to add an index.","Q_Score":0,"Tags":"python,sql,sqlite","A_Id":24909921,"CreationDate":"2014-07-23T11:55:00.000","Title":"Are SQLite rows ordered persistently?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"So I'm fairly new to Django development and I started using the cx_Oracle and MySQLdb libraries to connect to Oracle and MySQL databases. The idea is to build an interface that will connect to multiple databases and support CRUD ops. The user logs in with the db credentials for the respective databases. I tried not using the Django ORM (I know you may ask then what is the point)but then it is still all a learning endeavor for me. Without the Django ORM (or any ORM for that matter),I was having trouble persisting db connections across multiple requests(Tried using sessions).I need some direction as to what is the best way to design this.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":110,"Q_Id":24912020,"Users Score":0,"Answer":"Django uses connection pooling (i.e. few requests share the same DB connection). Of course, you can write a middleware to close and reinitialize connection on every request, but I can't guarantee you will not create race conditions, and, as you said, there is no point to do so.\nIf you want to make automatic multi-database CRUD, you'd better use some other framework (maybe, Flask or Bottle), because Django is optimized in much aspects for content sites with pre-set data scheme.\nAlso, it's not quite simple application, and maybe it's not a good way to learn some new technology at all. Try starting with something simpler, maybe.","Q_Score":0,"Tags":"django,mysql-python,django-orm,cx-oracle","A_Id":24917828,"CreationDate":"2014-07-23T13:38:00.000","Title":"How to use the Django ORM for creating an interface like MySQL admin that connects to multiple databases","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I want to store html string in sql server database using pyodbc driver. I have used nvarchar(max)as the data type for storing in the database but it is throwing the following error\nError:\n\n('HY000', '[HY000] [Microsoft][ODBC SQL Server Driver]Warning: Partial insert\/update. The insert\/update of a text or image column(s) did not succeed. (0) (SQLPutData); [42000] [Microsoft][ODBC SQL Server Driver][SQL Server]The text, ntext, or image pointer value conflicts with the column name specified. (7125)')","AnswerCount":1,"Available Count":1,"Score":0.3799489623,"is_accepted":false,"ViewCount":1047,"Q_Id":24930835,"Users Score":2,"Answer":"The link that Anthony Kong supplied includes something that may resolve the issue; it did for me in a very similar situation.\n\nswitch to DRIVER={SQL Server Native Client 10.0} instead of DRIVER={SQL Server} in the connection string\n\nThis would be for Sql Server 2008 (you didn't specify the Edition); for Sql Server 2012 it would be Native Client 11.0.","Q_Score":2,"Tags":"python","A_Id":31753938,"CreationDate":"2014-07-24T10:06:00.000","Title":"Pyodbc Store html unicode string in Sql Server","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a python webpage which pulls information from a MSSQL database with pyodbc.\nThis works, however since some queries that get run are quite heavy. the webpage can take 20-30 seconds to load.\nI want to fix this, What would be the best way to run all queries once every 15-30 minutes and store that data locally on the server or locally and pull that data into the webpage instead of rerunning the query on page load.\nI would like to have a relatively fast way for the webpage to acces the data so accesing the webpage would only take a 1-2 seconds max.\nredis is really fast but isn't really suited as it is too simple. key-value pairs\nthe most advanced I really need is is a table with a few rows and columnes (always less than 10).\nIs there a relatively fast way to store such data locally?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":764,"Q_Id":24933185,"Users Score":0,"Answer":"I have run into this when creating large reports.  Nobody will wait for a 30 second query, even if it's going back over 15 years of sales data.\nYou have a few options:\n\nCreate a SQL Job in the SQL Server Agent to run a stored procedure that runs the query and saves to a table.  (This is what I do)\nUse a scheduled task to run the query and save it to another table.  I think python could drive it on a windows box, but never used it myself.  I would do it in .NET.\nSometimes creating a view is enough of a performance boost, but depends on your data and database setup.  In addition check if there are any indexes or other common performance gains you can make.\n\nI really think #1 is elegant, simple, and keeps all the work in the database.","Q_Score":0,"Tags":"python,sql,sql-server,pyodbc","A_Id":24934239,"CreationDate":"2014-07-24T12:03:00.000","Title":"async information from MSSQL database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am developing a system that will need to connect from a remote mysql database on the fly to do a specific task. To accomplish this, I am thinking to use Mysql-db module in python. Since the remote database is not part of the system itself I do not prefer to add it on the system core database settings (DATABASES settings.py). Is there a much better way to accomplish this aside from using Mysql-db module? Is there a built in django module that I can use?","AnswerCount":2,"Available Count":2,"Score":0.0996679946,"is_accepted":false,"ViewCount":56,"Q_Id":24944869,"Users Score":1,"Answer":"For working inside virtualenv you need to install \n\npip install MySQL-python==1.2.5","Q_Score":0,"Tags":"database,django,mysql-python,django-database","A_Id":24997975,"CreationDate":"2014-07-24T22:10:00.000","Title":"Django Database Module","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am developing a system that will need to connect from a remote mysql database on the fly to do a specific task. To accomplish this, I am thinking to use Mysql-db module in python. Since the remote database is not part of the system itself I do not prefer to add it on the system core database settings (DATABASES settings.py). Is there a much better way to accomplish this aside from using Mysql-db module? Is there a built in django module that I can use?","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":56,"Q_Id":24944869,"Users Score":0,"Answer":"MySQLdb is the best way to do this.","Q_Score":0,"Tags":"database,django,mysql-python,django-database","A_Id":24997774,"CreationDate":"2014-07-24T22:10:00.000","Title":"Django Database Module","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I made a little PostgreSQL trigger with Plpython. This triggers plays a bit with the file system, creates and delete some files of mine. Created files are owned by the \"postgres\" unix user, but I would like them to be owned by another user, let's say foobar. Triggers are installed with user \"foobar\" and executed with user \"foobar\" too.\nIs there a way to execute the SQL trigger with the unix user 'foobar' with PostgreSQL or Plpython?\nShould I use SET ROLE foobar ?\nPlaying with SECURITY INVOKER and SECURITY DEFINER does not seem to be good enough.","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1158,"Q_Id":24951431,"Users Score":3,"Answer":"You're confusing operating system users and PostgreSQL users.\nSECURITY DEFINER lets you run a function as the defining postgresql user. But no matter what PostgreSQL user is running the operating system user the back-end server runs as is always the same - usually the operating system user postgres.\nBy design, the PostgreSQL server cannot run operating system commands or system calls as other operating system users. That would be a nasty security hole.\nHowever, if you want to permit that, you can. You could:\n\nGrant the postgres user sudo rights to run some or all commands as other users; or\nWrite a program to run with setuid rights to do what you want and grant the postgres user the right to execute it.\n\nIn either case, the only way to run these programs is by launching them from an untrusted procedural language like plpython or plperl, or from a C extension.'\nIt isn't clear why you want to set the file ownership like this in the first place, but I suspect it's probably not a great idea. What if the PostgreSQL client and server aren't even on the same computer? What if there's no operating system user for that PostgreSQL user, or the usernames are different? etc.","Q_Score":0,"Tags":"postgresql,roles,plpython","A_Id":24958698,"CreationDate":"2014-07-25T08:35:00.000","Title":"PostgreSQL trigger with a given role","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am using cherrypy along with sqlalchemy-mysql as backend. I would like to know the ways of dealing with UNICODE strings in cherrypy web application. One brute-force way would be to convert all string coming in as parameters into UNICODE (and then decoding them to UTF-8) before storing them to database. But I was wondering if there is any standard way of handling UNICODE characters in a web application. I tried cherrypy's tools.encode but it doesn't seem to work for me (may be I haven't understood it properly yet). Or may be there are standard python libraries to handle UNICODEs which I could just import and use. What ways should I look for?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":153,"Q_Id":24997946,"Users Score":0,"Answer":"SQLAlchemy provides Unicode or UnicodeText for your purposes.\nAlso don't forget about u'text'","Q_Score":0,"Tags":"mysql,python-2.7,unicode,sqlalchemy,cherrypy","A_Id":25016312,"CreationDate":"2014-07-28T14:52:00.000","Title":"how to handle UNICODE characters in cherrypy-sqlalchemy-mysql application?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm using python to write a report which is put into an excel spreadshet.\nThere are four columns, namely:\nProduct Name | Previous Value | Current Value | Difference \nWhen I am done putting in all the values I then want to sort them based on Current Value. Is there a way I can do this in xlwt? I've only seen examples of sorting a single column.","AnswerCount":1,"Available Count":1,"Score":-0.1973753202,"is_accepted":false,"ViewCount":1410,"Q_Id":25024437,"Users Score":-1,"Answer":"You will get data from queries, right? Then you will write them to an excel by xlwt. Just before writing, you can sort them. If you can show us your code, then maybe I can optimize them. Otherwise, you have to follow wnnmaw's advice, do it in a more complicate way.","Q_Score":1,"Tags":"python,excel,xlwt","A_Id":25032965,"CreationDate":"2014-07-29T20:32:00.000","Title":"Sorting multiple columns in excel via xlwt for python","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am using Robot Framework with Database Library to test database queries on localhost. I am running it by XAMPP. \nThis is my test case: \n\n*** Settings ***\nLibrary           DatabaseLibrary\n\n*** Variables ***\n@{DB}             robotframework    root    \\    localhost    3306\n\n*** Test Cases ***\nSelect from database\n    [Tags]    This\n    Connect To Database    MySQLdb    @{DB}[0]    @{DB}[1]    @{DB}[2]    @{DB}[3]    @{DB}[4]\n    @{results}=    Query    Select * From tbName\n    Log Many    @{results}\n\nI have installed MySQLDb for Python 2.7, however, when I run it using pybot, it keeps returning error: \nSelect from database                                                          | FAIL |\nNoSectionError: No section: 'default' \nPlease help me to solve this problem. Thanks.","AnswerCount":1,"Available Count":1,"Score":0.3799489623,"is_accepted":false,"ViewCount":4534,"Q_Id":25072996,"Users Score":2,"Answer":"You should check the content of dbConfigFile. You don't specify one so the default one is .\/resources\/db.cfg. \nThe error says when python try to parse that file it cannot find a section named default. In documentation it says:\n\nnote: specifying dbapiModuleName, dbName dbUsername or dbPassword directly will override the properties of the same key in dbConfigFile\n\nso even if you specify all properties it reads config file.","Q_Score":1,"Tags":"python-2.7,robotframework","A_Id":32266513,"CreationDate":"2014-08-01T04:44:00.000","Title":"Error: No section: 'default' in Robot Framework using DatabaseLibrary","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm initiating celery tasks via after_insert events. \nSome of the celery tasks end up updating the db and therefore need the id of the newly inserted row. This is quite error-prone because it appears that if the celery task starts running immediately sometimes sqlalchemy will not have finished committing to the db and celery won't find the row. \nWhat are my other options? \nI guess I could gather these celery tasks up somehow and only send them on \"after_commit\" but it feels unnecessarily complicated.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":209,"Q_Id":25078815,"Users Score":0,"Answer":"It wasn't so complicated, subclass Session, providing a list for appending tasks via after_insert. Then run through the list in after_commit.","Q_Score":0,"Tags":"python,sqlalchemy,celery","A_Id":25086833,"CreationDate":"2014-08-01T11:01:00.000","Title":"SQLAlchemy after_insert triggering celery tasks","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":0},{"Question":"I'm currently in the process of trying to redesign the general workflow of my lab, and am coming up against a conceptual roadblock that is largely due to my general lack of knowledge in this subject. \nOur data currently is organized in a typical file system structure along the lines of: \nDate\\Cell #\\Sweep #\nwhere for a specific date there are generally multiple Cell folders, and within those Cell folders there are multiple Sweep files (these are relatively simple .csv files where the recording parameters are saved separated in .xml files). So within any Date folder there may be a few tens to several hundred files for recordings that day organized within multiple Cell subdirectory folders. \nOur workflow typically involves opening multiple sweep files within a Cell folder, averaging them, and then averaging those with data points from other Cell folders, often across multiple days. \nThis is relatively straightforward to do with the Pandas and Numpy, although there is a certain \u201cmanual\u201d feel to it when remotely accessing folders saved to the lab server. We also, on occasion, run into issues because we often have to pull in data from many of these files at once. While this isn\u2019t usually an issue, the files can range between a few MBs to 1000s of MBs in size. In the latter case we have to take steps to not load the entire file into memory (or not load multiple files at once at the very least) to avoid memory issues. \nAs part of this redesign I have been reading about Pytables for data organization and for accessing data sets that may be too large to store within memory. So I guess my 2 main questions are \n\nIf the out-of-memory issues aren\u2019t significant (i.e. that utility wouldn\u2019t be utilized often), are there any significant advantages to using something like Pytables for data organization over simply maintaining a file system on a server (or locally)? \nIs there any reason NOT to go the Pytables database route? We are redesigning our data collection as well as our storage, and one option is to collect the data directly into Pandas dataframes and save the files in the HDF5 file type. I\u2019m currently weighing the cost\/benefit of doing this over the current system of the data being stored into csv files and then loaded into Pandas for analysis later on. \n\nMy thinking is that by creating a database vs. the filesystem we current have we may 1. be able to reduce (somewhat anyway) file size on disk through the compression that hdf5 offers and 2. accessing data may overall become easier because of the ability to query based on different parameters. But my concern for 2 is that ultimately, since we\u2019re usually just opening an entire file, that we won\u2019t be utilizing that to functionality all that much \u2013 that we\u2019d basically be performing the same steps that we would need to perform to open a file (or a series of files) within a file system. Which makes me wonder whether the upfront effort that this would require is worth it in terms of our overall workflow.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":332,"Q_Id":25110089,"Users Score":0,"Answer":"First of all, I am a big fan of Pytables, because it helped me manage huge data files (20GB or more per file), which I think is where Pytables plays out its strong points (fast access, built-in querying etc.). If the system is also used for archiving, the compression capabilities of HDF5 will reduce space requirements and reduce network load for transfer. I do not think that 'reproducing' your file system inside an HDF5 file has advantages (happy to be told I'm wrong on this). I would suggest a hybrid approach: keep the normal filesystem structure and put the experimental data in hdf5 containers with all the meta-data. This way you keep the flexibility of your normal filesystem (access rights, copying, etc.) and can still harness the power of pytables if you have bigger files where memory is an issue. Pulling the data from HDF5 into normal pandas or numpy is very cheap, so your 'normal' work flow shouldn't suffer.","Q_Score":0,"Tags":"python,csv,organization,pytables","A_Id":25122607,"CreationDate":"2014-08-03T23:40:00.000","Title":"Benefits of Pytables \/ databases over file system for data organization?","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"My RDS is in a VPC, so it has a private IP address. I can connect my RDS database instance from my local computer with pgAdmin using SSH tunneling via EC2 Elastic IP. \nNow I want to connect to the database instance in my code in python. How can I do that?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":667,"Q_Id":25112648,"Users Score":0,"Answer":"Point your python code to the same address and port you're using for the tunnelling.\nIf you're not sure check the pgAdmin destination in the configuration and just copy it.","Q_Score":2,"Tags":"postgresql,python-2.7,amazon-web-services,psycopg2,amazon-vpc","A_Id":25115502,"CreationDate":"2014-08-04T06:08:00.000","Title":"AWS - Connect to RDS via EC2 tunnel","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":1,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm using wsgi apache and flask to run my application. I'm use from yourapplication import app as application to start my application. That works so far fine. The problem is, with every request a new instance of my application is created. That leads to the unfortunate situation that my flask application creates a new database connection but only closes it after about 15 min. Since my server allows only 16 open DB connections the server starts to block requests very soon. BTW: This is not happening when I run flask without apache\/wsgi since it opens only one connection and serves all requests as I want. \nWhat I want: I want to run only one flask instance which then servers all requests.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1457,"Q_Id":25143105,"Users Score":1,"Answer":"The WSGIApplicationGroup directive may be what you're looking for as long as you have the wsgi app running in daemon mode (otherwise I believe apache's default behavior is to use prefork which spins up a process to handle each individual request):\n\nThe WSGIApplicationGroup directive can be used to specify which application group a WSGI application or set of WSGI applications belongs to. All WSGI applications within the same application group will execute within the context of the same Python sub interpreter of the process handling the request.\n\nYou have to provide an argument to the directive that specifies a name for the application group. There's a few expanding variables: %{GLOBAL}, %{SERVER}, %{RESOURCE} and %{ENV:variable}; or you can specify your own explicit name. %{GLOBAL} is special in that it expands to the empty string, which has the following behavior:\n\nThe application group name will be set to the empty string.\n  Any WSGI applications in the global application group will always be executed within the context of the first interpreter created by Python when it is initialised. Forcing a WSGI application to run within the first interpreter can be necessary when a third party C extension module for Python has used the simplified threading API for manipulation of the Python GIL and thus will not run correctly within any additional sub interpreters created by Python.\n\nI would recommend specifying something other than %{GLOBAL}.\nFor every process you have mod_wsgi spawn, everything will be executed in the same environment. Then you can simply control the number of database connections based on the number of processes you want mod_wsgi to spawn.","Q_Score":1,"Tags":"python,apache,flask,wsgi","A_Id":25143417,"CreationDate":"2014-08-05T15:49:00.000","Title":"start only one flask instance using apache + wsgi","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"My installed version of the python(2.7) module pandas (0.14.0) will not import. The message I receive is this:\nUserWarning: Installed openpyxl is not supported at this time. Use >=1.6.1 and <2.0.0.\nHere's the problem - I already have openpyxl version 1.8.6 installed so I can't figure out what the problem might be! Does anybody know where the issue may lie? Do I need a different combination of versions?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":114,"Q_Id":25168058,"Users Score":0,"Answer":"The best thing would be to remove the version of openpyxl you installed and let Pandas take care.","Q_Score":0,"Tags":"python,pandas,openpyxl,versions","A_Id":25178533,"CreationDate":"2014-08-06T18:55:00.000","Title":"Python pandas module openpxyl version issue","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I've looked through all the docs I could find, and read the source code...and it doesn't seem you can actually create a MySQL database (or any other kind, that I could find) using peewee.  If so, that means for any the database I may need to connect to, I would need to create it manually using mysql or some other tool.\nIs that accurate, or am I missing something?","AnswerCount":3,"Available Count":2,"Score":0.1973753202,"is_accepted":false,"ViewCount":4151,"Q_Id":25194297,"Users Score":3,"Answer":"Peewee cannot create databases with MySql or with other systems that require database and user setup, but will create the database with sqlite when the first table is created.","Q_Score":11,"Tags":"python-3.x,peewee","A_Id":25365070,"CreationDate":"2014-08-08T00:23:00.000","Title":"Can peewee create a new MySQL database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I've looked through all the docs I could find, and read the source code...and it doesn't seem you can actually create a MySQL database (or any other kind, that I could find) using peewee.  If so, that means for any the database I may need to connect to, I would need to create it manually using mysql or some other tool.\nIs that accurate, or am I missing something?","AnswerCount":3,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":4151,"Q_Id":25194297,"Users Score":14,"Answer":"Peewee can create tables but not databases. That's standard for ORMs, as creating databases is very vendor-specific and generally considered a very administrative task. PostgreSQL requires you to connect to a specific database, Oracle muddles the distinction between users and databases, SQLite considers each file to be a database...it's very environment specific.","Q_Score":11,"Tags":"python-3.x,peewee","A_Id":25195428,"CreationDate":"2014-08-08T00:23:00.000","Title":"Can peewee create a new MySQL database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have developed a website where the pages are simply html tables.  I have also developed a server by expanding on python's SimpleHTTPServer.  Now I am developing my database.\nMost of the table contents on each page are static and doesn't need to be touched.  However, there is one column per table (i.e. page) that needs to be editable and stored.  The values are simply text that the user can enter. The user enters the text via html textareas that are appended to the tables via javascript.  \nThe database is to store key\/value pairs where the value is the user entered text (for now at least).\nCurrent situation\nBecause the original format of my webpages was xlsx files I opted to use an excel workbook as my database that basically just mirrors the displayed web html tables (pages).\nI hook up to the excel workbook through win32com.  Every time the table (page) loads, javascript iterates through the html textareas and sends an individual request to the server to load in its respective text from the database.  \nCurrently this approach works but is terribly slow.  I have tried to optimize everything as much as I can and I believe the speed limitation is a direct consequence of win32com.\nThus, I see four possible ways to go:\n\nReplace my current win32com functionality with xlrd\nTry to load all the html textareas for a table (page) at once through one server call to the database using win32com\nSwitch to something like sql (probably use mysql since it's simple and robust enough for my needs)\nUse xlrd but make a single call to the server for each table (page) as in (2)\n\nMy schedule to build this functionality is around two days.\nDoes anyone have any thoughts on the tradeoffs in time-spent-coding versus speed of these approaches?  If anyone has any better\/more streamlined methods in mind please share!","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":273,"Q_Id":25195723,"Users Score":1,"Answer":"Probably not the answer you were looking for, but your post is very broad, and I've used win32coma and Excel a fair but and don't see those as good tools towards your goal. An easier strategy is this: \n\nfor the server, use Flask: it is a Python HTTP server that makes it crazy easy to respond to HTTP requests via Python code and HTML templates. You'll have a fully capable server running in 5 minutes, then you will need a bit of time create code to get data from your DB and render from templates (which are really easy to use). \nfor the database, use SQLite (there is far more overhead intergrating with MysQL); because you only have 2 days, so\n\nyou could also use a simple CSV file, since the API (Python has a CSV file read\/write module) is much simpler, less ramp up time. One CSV per user, easy to manage. You don't worry about insertion of rows for a user, you just append; and you don't implement remove of rows for a user, you just mark as inactive (a column for active\/inactive in your CSV). In processing GET request from client, as you read from the CSV, you can count how many certain rows are inactive, and do a re-write of the CSV, so once in a while the request will be a little slower to respond to client. \neven simpler yet you could use in-memory data structure of your choice if you don't need persistence across restarts of the server. If this is for a demo this should be acceptable limitation. \n\nfor the client side, use jQuery on top of javascript -- maybe you are doing that already. Makes it super easy to manipulate the DOM and use effects like slide-in\/out etc. Get yourself the book \"Learning jQuery\", you'll be able to make good use of jQuery in just a couple hours.\n\nIf you only have two days it might be a little tight, but you will probably need more than 2 days to get around the issues you are facing with your current strategy, and issues you will face imminently.","Q_Score":0,"Tags":"python,mysql,excel,win32com,xlrd","A_Id":25203796,"CreationDate":"2014-08-08T03:38:00.000","Title":"Database in Excel using win32com or xlrd Or Database in mysql","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"This is not a question of a code, I need to extract some BLOB data from an Oracle database using python script. My question is what are the steps in dealing with BLOB data and how to read as images, videos and text? Since I have no access to the database itself, is it possible to know the type of BLOBs stored if it is pictures, videos or texts? Do I need encoding or decoding in order to tranfer these BLOBs into .jpg, .avi or .txt files ? These are very basic questions but I am new to programming so need some help to find a starting point :)","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1342,"Q_Id":25205157,"Users Score":0,"Answer":"If you have a pure BLOB in the database, as opposed to, say, an ORDImage that happens to be stored in a BLOB under the covers, the BLOB itself has no idea what sort of binary data it contains. Normally, when the table was designed, a column would be added that would store the data type and\/or the file name.","Q_Score":0,"Tags":"oracle,python-2.7,blob","A_Id":25205260,"CreationDate":"2014-08-08T13:54:00.000","Title":"Reading BLOB data from Oracle database using python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am still a noob in web app development and sorry if this question might seem obvious for you guys.\nCurrently I am developing a web application for my University using Python and Django. And one feature of my web app is to retrieve a large set of data in a table in the database(postgreSQL), and displaying these data in a tabular form on webpage. Each column of the table need to have the sorting and filtering feature. The data set goes up to roughly 2 millions of rows. \nSo I wonder if something like jpxGrid could help me to achieve such goal or it would be too slow to handle\/sort\/display\/render such a large data set on web page. I plan to retrieve all the data inside the table once (only initiate one database query call) and pass it into jpxGrid, however, my colleague suggests that each sort and filter should initiate a separate query call to the database to achieve better performance(database order by is very fast). I tried to use another open source jquery library that handles the form and enables sorting, filtering and paging(non professional outdated one) at the beginning, which starts to lag after 5k data rows and becomes impossible to use after 20k rows. \nMy question is if something like jpxGrid is a good solution to my problem or I should build my own system that letting the database to handle the sorting and filtering(probably need to add the paging feature too). Thank you very much for helping.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1235,"Q_Id":25207697,"Users Score":3,"Answer":"Are you allowed to use paging in your output? If so, then i'd start by setting a page size of 100 (for example) and then use LIMIT 100 in my various SQL queries. Essentially, each time the user clicks next or prev on the web page a new query would be executed based on the current filtering or sorting options with the LIMIT. The SQL should be pretty easy to figure out.","Q_Score":1,"Tags":"python,database,django,postgresql,web","A_Id":25208098,"CreationDate":"2014-08-08T16:09:00.000","Title":"Handle and display large data set in web browser","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am scoping out a project with large, mostly-uncompressible time series data, and wondering if Django + Postgres with raw SQL is the right call.\nI have time series data that is ~2K objects\/hour, every hour.  This is about 2 million rows per year I store, and I would like to 1) be able to slice off data for analysis through a connection, 2) be able to do elementary overview work on the web, served by Django.  I think the best idea is to use Django for the objects themselves, but drop to raw SQL to deal with the large time series data associated.  I see this as a hybrid approach; that might be a red flag, but using the full ORM for a long series of data samples feels like overkill.  Is there a better way?","AnswerCount":4,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":10343,"Q_Id":25212009,"Users Score":0,"Answer":"You might also consider using the PostGIS postgres extension which includes support for raster data types (basically large grids of numbers) and has many features to make use of them.\nHowever, do not use the ORM in this case, you will want to do SQL directly on the server. The ORM will add a huge amount of overhead for large numerical datasets. It's also not very adapted to handling large matrices within python itself, for that you need numpy.","Q_Score":21,"Tags":"python,django,postgresql,heroku,bigdata","A_Id":25887408,"CreationDate":"2014-08-08T20:48:00.000","Title":"Django + Postgres + Large Time Series","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm working on a project that allows users to enter SQL queries with parameters, that SQL query will be executed over a period of time they decide (say every 2 hours for 6 months) and then get the results back to their email address.\nThey'll get it in the form of an HTML-email message, so what the system basically does is run the queries, and generate HTML that is then sent to the user.\nI also want to save those results, so that a user can go on our website and look at previous results.\nMy question is - what data do I save? \n\nDo I save the SQL query with those parameters (i.e the date parameters, so he can see the results relevant to that specific date). This means that when the user clicks on this specific result, I need to execute the query again.\nSave the HTML that was generated back then, and simply display it when the user wishes to see this result?\n\nI'd appreciate it if somebody would explain the pros and cons of each solution, and which one is considered the best & the most efficient.\nThe archive will probably be 1-2 months old, and I can't really predict the amount of rows each query will return.\nThanks!","AnswerCount":3,"Available Count":3,"Score":0.0665680765,"is_accepted":false,"ViewCount":35,"Q_Id":25222515,"Users Score":1,"Answer":"If I would create such type of application then\n\nI will have some common queries like get by current date,current time , date ranges, time ranges, n others based on my application for the user to select easily.\nSome autocompletions for common keywords.\nIf the data gets changed frequently there is no use saving html, generating new one is good option","Q_Score":0,"Tags":"python,html,database","A_Id":25222611,"CreationDate":"2014-08-09T20:01:00.000","Title":"Creating an archive - Save results or request them every time?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm working on a project that allows users to enter SQL queries with parameters, that SQL query will be executed over a period of time they decide (say every 2 hours for 6 months) and then get the results back to their email address.\nThey'll get it in the form of an HTML-email message, so what the system basically does is run the queries, and generate HTML that is then sent to the user.\nI also want to save those results, so that a user can go on our website and look at previous results.\nMy question is - what data do I save? \n\nDo I save the SQL query with those parameters (i.e the date parameters, so he can see the results relevant to that specific date). This means that when the user clicks on this specific result, I need to execute the query again.\nSave the HTML that was generated back then, and simply display it when the user wishes to see this result?\n\nI'd appreciate it if somebody would explain the pros and cons of each solution, and which one is considered the best & the most efficient.\nThe archive will probably be 1-2 months old, and I can't really predict the amount of rows each query will return.\nThanks!","AnswerCount":3,"Available Count":3,"Score":1.2,"is_accepted":true,"ViewCount":35,"Q_Id":25222515,"Users Score":1,"Answer":"Specifically regarding retrieving the results from queries that have been run previously I would suggest saving the results to be able to view later rather than running the queries again and again. The main benefits of this approach are:\n\nYou save unnecessary computational work re-running the same queries;\nYou guarantee that the result set will be the same as the original report. For example if you save just the SQL then the records queried may have changed since the query was last run or records may have been added \/ deleted.\n\nThe disadvantage of this approach is that it will probably use more disk space, but this is unlikely to be an issue unless you have queries returning millions of rows (in which case html is probably not such a good idea anyway).","Q_Score":0,"Tags":"python,html,database","A_Id":25222656,"CreationDate":"2014-08-09T20:01:00.000","Title":"Creating an archive - Save results or request them every time?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm working on a project that allows users to enter SQL queries with parameters, that SQL query will be executed over a period of time they decide (say every 2 hours for 6 months) and then get the results back to their email address.\nThey'll get it in the form of an HTML-email message, so what the system basically does is run the queries, and generate HTML that is then sent to the user.\nI also want to save those results, so that a user can go on our website and look at previous results.\nMy question is - what data do I save? \n\nDo I save the SQL query with those parameters (i.e the date parameters, so he can see the results relevant to that specific date). This means that when the user clicks on this specific result, I need to execute the query again.\nSave the HTML that was generated back then, and simply display it when the user wishes to see this result?\n\nI'd appreciate it if somebody would explain the pros and cons of each solution, and which one is considered the best & the most efficient.\nThe archive will probably be 1-2 months old, and I can't really predict the amount of rows each query will return.\nThanks!","AnswerCount":3,"Available Count":3,"Score":0.0665680765,"is_accepted":false,"ViewCount":35,"Q_Id":25222515,"Users Score":1,"Answer":"The crucial difference is that if data changes, new query will return different result than what was saved some time ago, so you have to decide if the user should get the up to date data or a snapshot of what the data used to be.\nIf relevant data does not change, it's a matter of whether the queries will be expensive, how many users will run them and how often, then you may decide to save them instead of re-running queries, to improve performance.","Q_Score":0,"Tags":"python,html,database","A_Id":25222678,"CreationDate":"2014-08-09T20:01:00.000","Title":"Creating an archive - Save results or request them every time?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I've done some research, and I don't fully understand what I found. \nMy aim is to, using a udp listener I wrote in python, store data that it receives from an MT4000 telemetry device. This data is received and read in hex, and I want that data to be put into a table, and store it as a string in base64. In terms of storing something as an integer by using the 'columnname' INT format, I would like to know how to store the information as base64? ie. 'data' TEXT(base64)? or something similar. \nCould I do this by simply using the TEXT datatype, and encode the data in the python program?\nI may be approaching this in the wrong way, as I may have misinterpreted what I read online.\nI would be very grateful for any help. Thanks,\nEd","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":5730,"Q_Id":25239361,"Users Score":2,"Answer":"You can just save the base64 string in a TEXT column type. After retrieval just decode this string with base64.decodestring(data) !","Q_Score":2,"Tags":"python,mysql","A_Id":25239591,"CreationDate":"2014-08-11T08:57:00.000","Title":"How to store base64 information in a MySQL table?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I've done some research, and I don't fully understand what I found. \nMy aim is to, using a udp listener I wrote in python, store data that it receives from an MT4000 telemetry device. This data is received and read in hex, and I want that data to be put into a table, and store it as a string in base64. In terms of storing something as an integer by using the 'columnname' INT format, I would like to know how to store the information as base64? ie. 'data' TEXT(base64)? or something similar. \nCould I do this by simply using the TEXT datatype, and encode the data in the python program?\nI may be approaching this in the wrong way, as I may have misinterpreted what I read online.\nI would be very grateful for any help. Thanks,\nEd","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":5730,"Q_Id":25239361,"Users Score":0,"Answer":"You can storage a base64 string in a TEXT column type, but in my experience I recommend to use LONGTEXT type to avoid truncated errors in big base64 texts.","Q_Score":2,"Tags":"python,mysql","A_Id":62777767,"CreationDate":"2014-08-11T08:57:00.000","Title":"How to store base64 information in a MySQL table?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Using Boto, you can create an S3 bucket and configure a lifecycle for it; say expire keys after 5 days. I would like to not have a default lifecycle for my bucket, but instead set a lifecycle depending on the path within the bucket. For instance, having path \/a\/ keys expire in 5 days, and path \/b\/ keys to never expire.\nIs there a way to do this using Boto? Or is expiration tied to buckets and there is no alternative?\nThank you","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":41,"Q_Id":25245710,"Users Score":0,"Answer":"After some research in the boto docs, it looks like using the prefix parameter in the lifecycle add_rule method allows you to do this.","Q_Score":0,"Tags":"python,amazon-web-services,amazon-s3,boto","A_Id":25245827,"CreationDate":"2014-08-11T14:28:00.000","Title":"Setting a lifecycle for a path within a bucket","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":1,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"When mounting and writing files in the google cloud storage using the gcsfs, the gcsfs is creating folders and files but not writing files. Most of the times it shows input\/output error. It even occurs even when we copy files from local directory to the mounted gcsfs directory.\ngcsfs version 0.15","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":554,"Q_Id":25265110,"Users Score":0,"Answer":"Although this is quiet an old topic, I will try to provide an answer especially because of people who might stumble on this in the course of their own work. I have experience using more recent versions of gcsfs and it works quiet well. You can find the latest documentation at https:\/\/gcsfs.readthedocs.io\/en\/latest. To make it work you need to have the environment variable:\nGOOGLE_APPLICATION_CREDENTIALS=SERVICE_ACCOUNT_KEY.json.","Q_Score":1,"Tags":"python-3.x,google-cloud-platform,google-cloud-storage","A_Id":57971532,"CreationDate":"2014-08-12T13:07:00.000","Title":"gcsfs is not writing files in the google bucket","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":0},{"Question":"I am using python to parse an Excel file and am accessing the application COM using excel = Dispatch('Excel.Application') at the beginning of a restart the code will find the application object just fine and I will be able to access the active workbook.  \nThe problem comes when I have had two instances of Excel open and I close the first.  From then on every call to excel = Dispatch('Excel.Application') provides an application object that is different from the open instance of Excel.  If I try excel.Visible=1 it opens a new Excel instance rather than showing the already open instance of excel.  How do I get the COM object of the already open instance of Excel rather than creating a new instance?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1075,"Q_Id":25298281,"Users Score":2,"Answer":"When an application registers itself, only the first instance gets registered, until it dies and then the very next instance to register gets registered.\nThere's no registration queue, so when your first instance dies, the second keeps unregistered, so any call to Excel.Application will launch a third instance and they'll keep using it until it dies too.\nIn summary, the instances launched in between registered instances never get registered.\nIf you need to reuse an instance, you must keep a pointer to it.\nThat said, if you get an instance of an open Excel file, you might obtain a link to an unregistered Excel instance.  For instance, if Excel 1 (registered) has workbook 1 open, and Excel 2 (unregistered) has workbook 2 open, if you ask for workbook 2, you'll get Excel 2's instance (e.g. through Workbook.Application).","Q_Score":3,"Tags":"python,excel,com,win32com","A_Id":25308893,"CreationDate":"2014-08-14T00:26:00.000","Title":"win32com dispatch Won't Find Already Open Application Instance","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":1,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"From a pyramid middleware application I'm calling a stored procedure with pymssql. The procedure responds nicely upon the first request I pass through the middleware from the frontend (angularJS). Upon subsequent requests however, I do not get any response at all, not even a timeout. \nIf I then restart the pyramid application, the same above described happens again.\nI'm observing this behavior with a couple of procedures that were implemented just yesterday. Some other procedures implemented months ago are working just fine, regardless of how often I call them.\nI'm not writing the procedures myself, they are provided for. \nFrom what I'm describing here, can anybody tell where the bug should be hiding most probably?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":122,"Q_Id":25367508,"Users Score":1,"Answer":"The solution was rather trivial. Within one object instance, I was calling two different stored procedures without closing the connection after the first call. That caused a pending request or so in the MSSQL-DB, locking it for further requests.","Q_Score":0,"Tags":"python-2.7,stored-procedures,pyramid,pymssql","A_Id":25646833,"CreationDate":"2014-08-18T16:05:00.000","Title":"pyramid middleware call to mssql stored procedure - no response","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"In general I want to know the possible benefits of Graphite. For now I have a web app that receives data directly from JavaScript Ajax call and plots the data using high chart. \n\nIt first run 20 different queries for each graph using Python from my SQL database.  \nAnd sends each result data to HighChart library using GET Ajax call. \nAnd HighChart adds plot to each graph in realtime. \n\nThere is no need to save data because I need only realtime plotting within certain time range. Data outside time range just plushes. \nBut when I see the 20 Ajax calls in one page I feel like I am doing this in an inefficient way although it gets the job done.\nSo I looked at the Graphite but it is hard for me to decide which is better. Since I will pull up all data from present SQL table I don't need another storage. But everybody says graphite performs fast but I would still need to instantiate 20 different graphite graphs. Please give me some guidance. \nWhat would you do if you have to visualize 20 different realtime graphs in one page concurrently each of which receives its own query data?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":199,"Q_Id":25374338,"Users Score":0,"Answer":"Maybe better is call one ajax which gets all data and then prepare parser which will return data for each chart.","Q_Score":0,"Tags":"javascript,python,ajax,highcharts,graphite","A_Id":25381895,"CreationDate":"2014-08-19T01:18:00.000","Title":"Graphite or multiple query with AJAX call?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am using python's CSV module to output a series of parsed text documents with meta data. I am using the csv.writer module without specifying a special delimiter, so I am assuming it is delimited using commas. There are many commas in the text as well as in the meta data, so I was expecting there to be way more columns in the document rows, when compared to the header row.\nWhat surprises me is that when I load the outputted file in Excel, everything looks exactly right. How does Excel know how to delimit this correctly??? How is it able to figure out which commas are text commas and which ones are delimiters?\nRelated question: Do people usually use CSV for saving text documents? Is this a standard practice? It seems inferior to JSON or creating a SQLite database in every sense, from long-term sustainability to ease of interpreting without errors.","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":518,"Q_Id":25380448,"Users Score":1,"Answer":"You shall inspect the real content of CSV file you have created and you will see, that there are ways to enclose text in quotes. This allows distinction between delimiter and a character inside text value.\nCheck csv module documentation, it explains these details too.","Q_Score":1,"Tags":"python,excel,csv,export-to-csv","A_Id":25380579,"CreationDate":"2014-08-19T09:52:00.000","Title":"Python CSV module - how does it avoid delimiter issues?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"We have a query which returns 0 records sometimes when called. When you call the getQueryResults on the jobId it returns with a valid pageToken with 0 rows. This is a bit unexpected since technically there is no data. Whats worst is if you keep supplying the pageToken for subsequent data-pulls it keeps giving zero rows with valid tokens at each page.\nIf the query does return data initially with a pageToken and you keep using the pageToken for subsequent data pulls it returns pageToken as None after the last page giving a termination condition. \nThe behavior here seems inconsistent?Is this a bug?\nHere is a sample jobresponse I see:\nHere is a sample job response:\n{u'kind': u'bigquery#getQueryResultsResponse', u'jobReference': {u'projectId': u'xxx', u'jobId': u'job_aUAK1qlMkOhqPYxwj6p_HbIVhqY'}, u'cacheHit': True, u'jobComplete': True, u'totalRows': u'0', u'pageToken': u'CIDBB777777QOGQFBAABBAAE', u'etag': u'\"vUqnlBof5LNyOIdb3TAcUeUweLc\/6JrAdpn-kvulQHoSb7ImNUZ-NFM\"', u'schema': {......}}\nI am using python and running queries on GAE using the BQ api","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":471,"Q_Id":25388124,"Users Score":0,"Answer":"This is a known issue that has lingered for far far too long. It is fixed in this week's release, which should go live this afternoon or tomorrow.","Q_Score":1,"Tags":"python,google-app-engine,google-bigquery","A_Id":25393093,"CreationDate":"2014-08-19T16:07:00.000","Title":"BigQuery Api getQueryResults returning pageToken for 0 records","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"Let's assume I am developing a service that provides a user with articles. Users can favourite articles and I am using Solr to store these articles for search purposes.\nHowever, when the user adds an article to their favourites list, I would like to be able to figure out out which articles the user has added to favourites so that I can highlight the favourite button.\nI am thinking of two approaches:\n\nFetch articles from Solr and then loop through each article to fetch the \"favourite-status\" of this article for this specific user from MySQL.\nWhenever a user favourites an article, add this user's ID to a multi-valued column in Solr and check whether the ID of the current user is in this column or not.\n\nI don't know the capacity of the multivalued column... and I also don't think the second approach would be a \"good practice\" (saving user-related data in index).\nWhat other options do I have, if any? Is approach 2 a correct approach?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":102,"Q_Id":25413343,"Users Score":0,"Answer":"I'd go with a modified version of the first one - it'll keep user specific data that's not going to be used for search out of the index (although if you foresee a case where you want to search for favourite'd articles, it would probably be an interesting field to have in the index) for now. For just display purposes like in this case, I'd take all the id's returned from Solr, fetch them in one SQL statement from the database and then set the UI values depending on that. It's a fast and easy solution.\nIf you foresee that \"search only in my fav'd articles\" as a use case, I would try to get that information into the index as well (or other filter applications against whether a specific user has added the field as a favourite). I'd try to avoid indexing anything more than the user id that fav'd the article in that case.\nBoth solutions would however work, although the latter would require more code - and the required response from Solr could grow large if a large number of users fav's an article, so I'd try to avoid having to return a set of userid's if that's the case (many fav's for a single article).","Q_Score":0,"Tags":"python,mysql,solr,django-haystack","A_Id":25414143,"CreationDate":"2014-08-20T19:55:00.000","Title":"Solr & User data","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Logging sql queries is useful for debugging but in some cases, it's useless to log the whole query, especially for big inserts. In this case, display only first N caracters would be enough.\nIs there a simple way to truncate sql queries when they are logged ?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":142,"Q_Id":25446832,"Users Score":2,"Answer":"It's quite simple actually:\nin settings.py, let's say your logger is based on a handler which formatter is named 'simple'. \n\n'formatters': {\n        ...\n        'simple': {\n            'format': '%(asctime)s %(message).150s'\n        },\n        ...\n    },\n\nThe message will now be truncated to the first 150 caracters. Playing with handlers will allow you to specify this parameter per each logger. Thanks Python!","Q_Score":2,"Tags":"python,django","A_Id":25447136,"CreationDate":"2014-08-22T12:15:00.000","Title":"Truncate logging of sql queries in Django","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I ran a simple select query (with no LIMIT applied) using the Big Query python api. I also supplied a destination table as the result was too large. When run, the job returned an \"unexpected LIMIT clause\" error. I used ignore case at the end of the query. There could be a possibility that it might be causing the problem.\nAnybody ran into a similar problem?\nFor reference, my job_id is job_QrkB7t9WFEHqcH5qfsPZZsM476E","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":144,"Q_Id":25483349,"Users Score":1,"Answer":"This issue is an artifact of how bigquery does \"allow large results\" queries interacting poorly with the \"ignore case\" clause. We're tracking an internal bug on the issue, and hopefully will have a fix soon. The workaround is either to remove the \"allow large results\" flag or the \"ignore case\" clause.","Q_Score":1,"Tags":"python,google-bigquery","A_Id":25489066,"CreationDate":"2014-08-25T09:57:00.000","Title":"BigQuery: \"unexpected LIMIT clause at:\" error when using list query job","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Background.\nMy OS is Win7 64bit.\nMy Python is 2.7 64bit from python-2.7.8.amd64.msi\nMy cx_Oracle is 5.0 64bit from cx_Oracle-5.0.4-10g-unicode.win-amd64-py2.7.msi\nMy Oracle client is 10.1 (I don't know 32 or 64 arch, but SQL*Plus is 10.1.0.2.0\nDatabase is \nOracle Database 10g Enterprise Edition Release 10.2.0.4.0 - 64bit\nPL\/SQL Release 10.2.0.4.0 - Production\nCORE    10.2.0.4.0      Production\nTNS for 64-bit Windows: Version 10.2.0.4.0 - Production\nNLSRTL Version 10.2.0.4.0 - Production\nORACLE_HOME variable added from haki reply.\nC:\\Oracle\\product\\10.1.0\\Client_1\\\nNot work problem still persist.\nORACLE_HOME Try Oracle instant from instantclient-basic-win64-10.2.0.5.zip\nC:\\instantclient_10_2\\\nC:\\Users\\PavilionG4>sqlplus Lee\/123@chstchmp\nError 6 initializing SQL*Plus\nMessage file sp1.msb not found\nSP2-0750: You may need to set ORACLE_HOME to your Oracle software directory\nMy sql*plus is not let me set the Oracle.\nORACLE_HOME Come back to the\nC:\\Oracle\\product\\10.1.0\\Client_1\\\nPATH variable  \nC:\\Program Files (x86)\\Seagate Software\\NOTES\\C:\\Program Files (x86)\\Seagate Software\\NOTES\\DATA\\C:\\Program Files (x86)\\Java\\jdk1.7.0_05\\binC:\\Oracle\\product\\10.1.0\\Client_1\\binC:\\Oracle\\product\\10.1.0\\Client_1\\jre\\1.4.2\\bin\\clientC:\\Oracle\\product\\10.1.0\\Client_1\\jre\\1.4.2\\binC:\\app\\PavilionG4\\product\\11.2.0\\dbhome_1\\binC:\\app\\PavilionG4\\product\\11.2.0\\client_2\\binc:\\Program Files (x86)\\AMD APP\\bin\\x86_64c:\\Program Files (x86)\\AMD APP\\bin\\x86C:\\Windows\\system32C:\\WindowsC:\\Windows\\System32\\WbemC:\\Windows\\System32\\WindowsPowerShell\\v1.0\\c:\\Program Files (x86)\\ATI Technologies\\ATI.ACE\\Core-StaticC:\\Users\\PavilionG4\\AppData\\Local\\Smartbar\\Application\\C:\\PROGRA~2\\IBM\\SQLLIB\\BINC:\\PROGRA~2\\IBM\\SQLLIB\\FUNCTIONC:\\Program Files\\gedit\\binC:\\Kivy-1.7.2-w32C:\\Program Files (x86)\\ZBar\\binjC:\\Program Files (x86)\\Java\\jdk1.7.0_05\\binC:\\Program Files\\MATLAB\\R2013a\\runtime\\win64C:\\Program Files\\MATLAB\\R2013a\\binC:\\Python27\nTNS is :\nC:\\Oracle\\product\\10.1.0\\Client_1\\NETWORK\\ADMIN\\tnsnames.ora\nREPORT1 =\n  (DESCRIPTION =\n    (ADDRESS_LIST =\n      (ADDRESS = (PROTOCOL = TCP)(HOST = 172.28.128.110)(PORT = 1521))\n    )\n    (CONNECT_DATA =\n      (SERVICE_NAME = REPORT1)\n    )\n  )\nf1.py shows me error\nimport cx_Oracle\nip = '172.25.25.42'\nport = 1521\nSID = 'REPORT1'\ndns_tns = cx_Oracle.makedsn(ip,port,SID)\nconnection = cx_Oracle.connect(u\"Lee\",u\"123\",dns_tns)\ncursor = connection.cursor()\nconnection.close()\nError\nTraceback (most recent call last):\n  File \"f1.py\", line 6, in \n    connection = cx_Oracle.connect(u\"Lee\",u\"123\",dns_tns)\ncx_Oracle.InterfaceError: Unable to acquire Oracle environment handle\nQuestions\n1. How to acquire Oracle environment handle?\nI had searched the websites. Unfortunately they are not hit my problem at all.\n2. How to let Python use another Oracle client without impact to the existing one?","AnswerCount":1,"Available Count":1,"Score":0.3799489623,"is_accepted":false,"ViewCount":6803,"Q_Id":25542787,"Users Score":2,"Answer":"If python finds more than one OCI.DLL file in the path (even if they are identical) it will throw this error. (Your path statement looks like it may throw up more than one). You can manipulate the path inside your script to constrain where python will look for the supporting ORACLE files which may be your only option if you have to run several versions of oracle\/clients locally.","Q_Score":4,"Tags":"python,oracle","A_Id":27795948,"CreationDate":"2014-08-28T07:10:00.000","Title":"Python + cx_Oracle : Unable to acquire Oracle environment handle","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":0},{"Question":"I need to know, what are the steps to generate an Excel sheet in OpenERP?\nOr put it this way, I want to generate an Excel sheet for data that I have retrieved from different tables through queries with a function that I call from a button on wizard. Now I want when I click on the button an Excel sheet should be generated.\nI have installed OpenOffice, the problem is I don't know how to create that sheet and put data on it. Please will you tell me the steps?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":596,"Q_Id":25552075,"Users Score":1,"Answer":"You can do it easily with python library called XlsxWriter. Just download it and add in openerp Server, look for XlsxWriter Documentation , plus there are also other python libraries for generating Xlsx reports.","Q_Score":0,"Tags":"python,openerp","A_Id":25993349,"CreationDate":"2014-08-28T15:00:00.000","Title":"What are the steps to create or generate an Excel sheet in OpenERP?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I was wondering if one of you could advice me how to tackle a problem I am having. I developed a python script that updates data to a database (MySQL) every iteration (endless while loop). What I want to prevent is that if the script is accidentally closed or stopped half way the script it waits till all the data is loaded into the database and the MySQL connection is closed (I want this to prevent incomplete queries). Is there a way to tell the program to wait till the loop is done before it closes?\nI hope this all makes sense, feel free to ask questions.\nThank you for your time in advance.","AnswerCount":3,"Available Count":1,"Score":0.1325487884,"is_accepted":false,"ViewCount":184,"Q_Id":25561971,"Users Score":2,"Answer":"There are some things you can do to prevent a program from being closed unexpectedly (signal handlers, etc), but they only work in some cases and not others.  There is always the chance of a system shutdown, power failure or SIGKILL that will terminate your program whether you like it or not.  The canonical solution to this sort of problem is to use database transactions.\nIf you do your work in a transaction, then the database will simply roll back any changes if your script is interrupted, so you will not have any incomplete queries.  The worst that can happen is that you need to repeat the query from the beginning next time.","Q_Score":0,"Tags":"python,mysql,while-loop","A_Id":25562066,"CreationDate":"2014-08-29T05:02:00.000","Title":"Closing python MySQL script","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"After importing the module, on script run I get the error and I have the module installed already, I am new with python, so I expect I might have forgot to install something else? Python is version 2.7.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":691,"Q_Id":25623002,"Users Score":1,"Answer":"Maybe you have more versions than 2.7 and You installed the module on another version.","Q_Score":0,"Tags":"python-2.7,mysql-python","A_Id":25797155,"CreationDate":"2014-09-02T12:05:00.000","Title":"error \"No module named MySQLdb\"","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I need help switching my database engine from sqlite to mysql. manage.py datadump is returning the same error that pops up when I try to do anything else with manage.py : ImproperlyConfigured: Error loading MySQL module, No module named MySQLdb.\nThis django project is a team project. I pulled new changes from bitbucket and our backend has a new configuration. This new configuration needs mysql (and not sqlite) to work. Our lead dev is sleeping right now. I need help so I can get started working again. \nEdit: How will I get the data in the sqlite database file into the new MySQL Database?","AnswerCount":2,"Available Count":1,"Score":-0.0996679946,"is_accepted":false,"ViewCount":4742,"Q_Id":25629092,"Users Score":-1,"Answer":"Try the followings steps:\n1. Change DATABASES in settings.py to MYSQL engine\n2. Run $ .\/manage.py syncdb","Q_Score":0,"Tags":"python,mysql,django,sqlite,mysql-python","A_Id":25630191,"CreationDate":"2014-09-02T17:31:00.000","Title":"How can I switch my Django project's database engine from Sqlite to MySQL?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have written an extensive python package that utilizes excel and pywin32.\nI am now in the progress of moving this package to a linux environment on a Vagrant machine.\nI know there are \"emulator-esque\" software packages (e.g. WINE) that can run Windows applications and look-a-likes for some Windows applications (e.g. Excel to OpenOffice).\nHowever, I am not seeing the right path to take in order to get my pywin32\/Excel dependent code written for Windows running in a Linux environment on a Vagrant machine.  Ideally, I would not have to alter my code at all and just do the appropriate installs on my Vagrant machine.\nThanks","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":850,"Q_Id":25629462,"Users Score":2,"Answer":"The short answer is, you can't. WINE does not expose a bottled Windows environment's COM registry out to linux\u2014and, even if it did, pywin32 doesn't build on anything but Windows.\nSo, here are some options, roughly ordered from the least amount of change to your code and setup to the most:\n\nRun both your Python script and Excel under real Windows, inside a real emulator.\nRun both your Python script and Excel under WINE.\nWrite or find a library that does expose a bottled Windows environment's COM registry out to Linux.\nWrite or find a cross-platform DCOM library that presents a win32com-like API, then change your code to use that to connect to the bottled Excel remotely.\nRewrite your code to script Excel indirectly by, e.g., sshing into a Windows box and running minimal WSH scripts.\nRewrite your code to script LibreOffice or whatever you prefer instead of Excel.\nRewrite your code to process Excel files (or CSV or some other interchange format) directly instead of scripting Excel.","Q_Score":0,"Tags":"python,linux,excel,vagrant,pywin32","A_Id":25629595,"CreationDate":"2014-09-02T17:56:00.000","Title":"Porting Python on Windows using pywin32\/excel to Linux on Vagrant Machine","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":0},{"Question":"In Python, I'm using SQLite's executemany() function with INSERT INTO to insert stuff into a table. If I pass executemany() a list of things to add, can I rely on SQLite inserting those things from the list in order? The reason is because I'm using INTEGER PRIMARY KEY to autoincrement primary keys. For various reasons, I need to know the new auto-incremented primary key of a row around the time I add it to the table (before or after, but around that time), so it would be very convenient to simply be able to assume that the primary key will go up one for every consecutive element of the list I'm passing executemany(). I already have the highest existing primary key before I start adding stuff, so I can increment a variable to keep track of the primary key I expect executemany() to give each inserted row. Is this a sound idea, or does it presume too much?\n(I guess the alternative is to use execute() one-by-one with sqlite3_last_insert_rowid(), but that's slower than using executemany() for many thousands of entries.)","AnswerCount":1,"Available Count":1,"Score":0.537049567,"is_accepted":false,"ViewCount":444,"Q_Id":25712611,"Users Score":3,"Answer":"Python's sqlite3 module executes the statement with the list values in the correct order.\nNote: if the code already knows the to-be-generated ID value, then you should insert this value explicitly so that you get an error if this expectation turns out to be wrong.","Q_Score":3,"Tags":"python,sql,sqlite","A_Id":25712762,"CreationDate":"2014-09-07T16:52:00.000","Title":"Python SQLite executemany() always in order?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"After scanning the very large daily event logs using regular expression, I have to load them into a SQL Server database. I am not allowed to create a temporary CSV file and then use the command line BCP to load them into the SQL Server database. \nUsing Python, is it possible to use BCP streaming to load data into SQL Server database? The reason I want to use BCP is to improve the speed of the insert into SQL Server database.\nThanks","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1625,"Q_Id":25740355,"Users Score":0,"Answer":"The BCP API is only available using the ODBC call-level interface and the managed SqlClient .NET API using the SqlBulkCopy class.  I'm not aware of a Python extension that provides BCP API access.\nYou can insert many rows in a single transaction to improve performance.  This can be accomplished by batching individual insert statements or by passing multiple rows at once using an XML parameter (which also reduces round-trips).","Q_Score":1,"Tags":"python,sql-server","A_Id":25743680,"CreationDate":"2014-09-09T08:52:00.000","Title":"Loading Large data into SQL Server [BCP] using Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I've got a sqlite3 database and I want to write in it from multiple threads. I've got multiple ideas but I'm not sure which I should implement.\n\ncreate multiple connection, detect and waif if the DB is locked\nuse one connection and try to make use of Serialized connections (which don't seem to be implemented in python)\nhave a background process with a single connection, which collects the queries from all threads and then executes them on their behalft\nforget about SQlite and use something like Postgresql\n\nWhat are the advances of these different approaches and which is most likely to be fruitful? Are there any other possibilities?","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1466,"Q_Id":25747192,"Users Score":0,"Answer":"I used method 1 before. It is the easiest in coding. Since that project has a small website, each query take only several milliseconds. All the users requests can be processed promptly. \nI also used method 3 before. Because when the query take longer time, it is better to queue the queries since frequent \"detect and wait\" makes no sense here. And would require a classic consumer-producer model. It would require more time to code.\nBut if the query is really heavy and frequent. I suggest look to other db like MS SQL\/MySQL.","Q_Score":4,"Tags":"python,multithreading,postgresql,sqlite","A_Id":25748935,"CreationDate":"2014-09-09T14:28:00.000","Title":"Writing in SQLite multiple Threads in Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"i'm writing a script that puts a large number of xml files into mongodb, thus when i execute the script multiple times the same object is added many times to the same collection.\nI checked out for a way to stop this behavior by checkinng the existance of the object before adding it, but can't find a way.\nhelp!","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":491,"Q_Id":25807271,"Users Score":0,"Answer":"You can index on one or more fields(not _id) of the document\/xml structure. Then make use of find operator to check if a document containing that indexed_field:value is present in the collection. If it returns nothing then you can insert new documents into your collection. This will ensure only new docs are inserted when you re-run the script.","Q_Score":0,"Tags":"python,mongodb,pymongo,upsert","A_Id":25807361,"CreationDate":"2014-09-12T11:28:00.000","Title":"add if no duplicate in collection mongodb python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":1,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I want to store the job in mongodb using python and it should schedule on specific time. \nI did googling and found APScheduler will do. i downloaded the code and tried to run the code.\nIt's schedule the job correctly and run it, but it store the job in apscheduler database of mongodb, i want to store the job in my own database.\nCan please tell me how to store the job in my own database instead of default db.","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":708,"Q_Id":25884242,"Users Score":1,"Answer":"Simply give the mongodb jobstore a different \"database\" argument. It seems like the API documentation for this job store was not included in what is available on ReadTheDocs, but you can inspect the source and see how it works.","Q_Score":0,"Tags":"mongodb,python-2.7,apscheduler","A_Id":25898609,"CreationDate":"2014-09-17T07:01:00.000","Title":"APScheduler store job in custom database of mongodb","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":0},{"Question":"I have built a couple basic workflows using XML tools on top of XLSX workbooks that are mapped to an XML schema. You would enter data into the spreadsheet, export the XML and I had some scripts that would then work with the data.\nNow I'm trying to eliminate that step and build a more integrated and portable tool that others could use easily by moving from XSLT\/XQuery to Python. I would still like to use Excel for the data entry, but have the Python script read the XLSX file directly. \nI found a bunch of easy to use libraries to read from Excel but they need to explicitly state what cells the data is in, like range('A1:C2') etc. The useful thing about using the XML maps was that users could resize  or even move tables to fit different rows and rename sheets. Is their a library that would let me select tables as units?\nAnother approach I tried was to just uncompress the XLSX and just parse the XML directly. The problem with that is that our data is quite complex (taking up to 30-50 sheets) and parsing that in the uncompressed XLSX structure is really daunting. I did find my XML schema within the uncompressed XLSX, so is there any way to reformat the data into this schema outside of Excel? (basically what Excel does when I save a workbook as an .xml file)","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":2150,"Q_Id":25893266,"Users Score":0,"Answer":"The Excel format is pretty complicated with dependencies between components \u2013 you can't for example be sure of that the order of the worksheets in the folder worksheets has any bearing to what the file looks like in Excel.\nI don't really understand exactly what you're trying to do but the existing libraries present an interface for client code that hides the XML layer. If you don't want that you'll have to root around for the parts that you find useful. In openpyxl you want to look at the stuff in openpyxl\/reader specifically worksheet.py.\nHowever, you might have better luck using lxml as this (using libxml2 in the background) will allow you load a single XML into Python and manipulate it directly using the .objectify() method. We don't do this in openpyxl because XML trees consume a lot of memory (and many people have very large worksheets) but the library for working with Powerpoint shows just how easy this can be.","Q_Score":0,"Tags":"python,xml,excel,xlsx,openpyxl","A_Id":25908953,"CreationDate":"2014-09-17T14:25:00.000","Title":"XLSX to XML with schema map","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am close to finishing an ORM for RethinkDB in Python and I got stuck at writing tests. Particularly at those involving save(), get() and delete() operations. What's the recommended way to test whether my ORM does what it is supposed to do when saving or deleting or getting a document?\nRight now, for each test in my suite I create a database, populate it with all tables needed by the test models (this takes a lot of time, almost 5 seconds\/test!), run the operation on my model (e.g.: save()) and then manually run a query against the database (using RethinkDB's Python driver) to see whether everything has been updated in the database.\nNow, I feel this isn't just right; maybe there is another way to write these tests or maybe I can design the tests without even running that many queries against the database. Any idea on how can I improve this or a suggestion on how this has to be really done?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":484,"Q_Id":25916839,"Users Score":3,"Answer":"You can create all your databases\/tables just once for all your test.\nYou can also use the raw data directory:\n- Start RethinkDB\n- Create all your databases\/tables\n- Commit it.\nBefore each test, copy the data directory, start RethinkDB on the copy, then when your test is done, delete the copied data directory.","Q_Score":3,"Tags":"python,unit-testing,testing,orm,rethinkdb","A_Id":25922468,"CreationDate":"2014-09-18T15:32:00.000","Title":"Testing an ORM for RethinkDB","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am using mongoimport in a python script to import multiple CSV files into my Mongo DB. Some values contain backslash escaped commas. How can I use this to correctly import these files to Mongo? I can't find any specific solutions to this.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":313,"Q_Id":25936385,"Users Score":0,"Answer":"I'm not familiar with mongoimport, but I do know that if you use csv.reader, the backslashes are taken care of during reading. Maybe you could consider using a package specifically designed to read the csv, and then pass that along to mongoimport.","Q_Score":0,"Tags":"python,mongoimport","A_Id":25936756,"CreationDate":"2014-09-19T14:34:00.000","Title":"Mongoimport: Escaping commas in CSV","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I know you can read in Excel files with pandas, but I have had trouble reading in files where the column headings in the worksheets are not in a format easily readable like plain text.\nIn other words, if the column headings had special characters then the file would fail to import. Where as if you import data like that into Microsoft Access or other databases, you get the option to import anyway, or remove special characters.\nMy only solution to this has been to write an Excel macro to strip out characters not usually liked by databases when importing - and then import the file using python.\nBut there must be a way of handling this situation purely using python (which is a lot faster).\nMy question, how does python handle importing .xls and .xlsx files when the column headings have special characters which won't import?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1140,"Q_Id":25987179,"Users Score":0,"Answer":"Add a \"u\" before your string. For example, if you're looking for a column named 'liss\u00e9' in a dataframe \"df\" then you should put df[u'liss\u00e9']","Q_Score":1,"Tags":"python,excel,pandas,xls,xlsx","A_Id":49387955,"CreationDate":"2014-09-23T04:56:00.000","Title":"Python: read an Excel file using Pandas when the file has special characters in column headers","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Django 1.7, Python 3.4.\nIn my models I have several TextFields defined.\nWhen I go to load a JSON fixture (which was generated from an SQLite3 dump), it fails on the second object, which has 515 characters for one of its fields.\nThe error printed is \npsycopg2.DataError: value too long for type character varying(500)\nI created a new database (not just a table drop, a whole new db), modified my settings.py file, ran manage.py syncdb on the new database, created a user, and tried to load the data again, getting the same error.\nUpon opening pgAdmin3, all columns, both CharField and TextField defined are listed as type character var.\nSo it seems TextField is being ignored and CharFields are being created instead.  The PostgreSQL documentation explicitly lists both text and character types, and defines text as being unlimited in length.  Any idea why?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1186,"Q_Id":26028200,"Users Score":1,"Answer":"I'm not sure what the exact cause was, but it seems to be related to django's migration tool storing migrations, even on a new database.\nWhat I did to get this behavior:\n\nCreate django project, then apps, using CharField\nsyncdb, run the project's dev server\nkill the devserver, modify fields to be TextField\nCreate a new Postgres database, modify settings.py \nRun syncdb, attempt to load fixtures\nSee the error in question, examine db instance\n\nWhat fixed the problem:\n\nCreate a new database, modify settings.py\ndelete all migrations in apps\/migrations folders\nafter running syncdb, also run createmigrations and migrate\n\nThe last step generated a migration, even though there were none stored in the migrations folder, and there had been no changes to models or data since syncdb was run on the new database, which I found to be odd.\nSomewhere in the last two steps this was fixed.  Future people stumbling upon this: sorry, I'm not going to keep creating django projects to test the behavior further, but perhaps with this information you can fix your own database problems.","Q_Score":2,"Tags":"python,sql,django,postgresql,psycopg2","A_Id":26030265,"CreationDate":"2014-09-24T23:35:00.000","Title":"Why is Django creating my TextField as a varchar in the PostgreSQL database?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a Python script running as a daemon. At startup, it spawns 5 processes, each of which connects to a Postgres database. Now, in order to reduce the number of DB connections (which will eventually become really large), I am trying to find a way of sharing a single connection across multiple processes. And for this purpose I am looking at the multiprocessing.sharedctypes.Value API. However, I am not sure how I can pass a psycopg2.connection object using this API across processes. Can anyone tell me how it might be done?\nI'm also open to other ideas in order to solve this issue.\nThe reason why I did not consider passing the connection as part of the constructor to the 5 processes is mutual exclusion handling. I am not sure how I can prevent more than one process from accessing the connection if I follow this approach. Can someone tell me if this is the right thing to do?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":5128,"Q_Id":26070040,"Users Score":12,"Answer":"You can't sanely share a DB connection across processes like that. You can sort-of share a connection between threads, but only if you make sure the connection is only used by one thread at a time. That won't work between processes because there's client-side state for the connection stored in the client's address space.\nIf you need large numbers of concurrent workers, but they're not using the DB all the time, you should have a group of database worker processes that handle all database access and exchange data with your other worker processes. Each database worker process has a DB connection. The other processes only talk to the database via your database workers.\nPython's multiprocessing queues, fifos, etc offer appropriate messaging features for that.","Q_Score":4,"Tags":"python,postgresql,psycopg2,python-multiprocessing","A_Id":26072257,"CreationDate":"2014-09-27T00:16:00.000","Title":"Share connection to postgres db across processes in Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have CSV files that I want to make database tables from in mysql. I've searched all over and can't find anything on how to use the header as the column names for the table. I suppose this must be possible. In other words, when creating a new table in MySQL do you really have to define all the columns, their names, their types etc in advance. It would be great if MySQL could do something like Office Access where it converts to the corresponding type depending on how the value looks. \nI know this is maybe a too broadly defined question, but any pointers in this matter would be helpful. I am learning Python too, so if it can be done through a python script that would be great too. \nThank you very much.","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":3067,"Q_Id":26108160,"Users Score":0,"Answer":"The csv module can easily give you  the column names from the first line, and then the values from the other ones. The hard part will be do guess the correct column types. When you load a csv file into an Excel worksheet, you only have few types : numeric, string, date.\nIn a database like MySQL, you can define the size of string columns, and you can give the table a primary key and eventually other indexes. You will not be able to guess that part automatically from a csv file.\nAt the simplest way, you can treat all columns as varchar(255). It is really uncommon to have fields in a csv file that do not fit in 255 characters. If you want something more clever, you will have to scan the file twice : first time to control the maximum size for each colum, and at the end, you could take the minimum power of 2 greater than that. Next step would be to control if any column contains only integers or floating point values. It begins to be harder to do that automatically, because the representation of floating point values may be different depending on the locale. For example 12.51 in an english locale would be 12,51 in a french locale. But Python can give you the locale.\nThe hardest thing would be eventual date or datetime fields, because there are many possible formats only numeric (dd\/mm\/yyyy or mm\/dd\/yy) or using plain text (Monday, 29th of september).\nMy advice would be to define a default mode, for example all string, or just integer and strings, and use configuration parameters or even a configuration file to finely tune conversion per column.\nFor the reading part, the csv module will give you all what you need.","Q_Score":0,"Tags":"python,mysql,sql,csv","A_Id":26108522,"CreationDate":"2014-09-29T20:19:00.000","Title":"create database by load a csv files using the header as columnnames (and add a column that has the filename as a name)","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"In my project there is two models ,ORGANISATION and CUSTUMER .Here what i am doing is while i am adding new customer to the organisation i save the organisation_id to the table CUSTOMER .But now i am worrying about the performance of my project when the database becomes huge.\nSo now i am planning to create new database for every newly creating organisation .And save all the information of the organisation in that organisation's database. But i don't know how to create a new database for every newly creating organisation.And i'd like to know which method is better in performance.Please correct the question if not.","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":181,"Q_Id":26157625,"Users Score":1,"Answer":"It doesn't make sense to create a new database for each organization. Even if the number of customers or organizations grows to the hundreds or thousands, keeping data in a single database is your best option.\nEdit:\nYour original concern was that an increase in the number of organizations would impact performance. Well then, imagine if you had to create an entire database for each organization. You would have the same tables, indexes, views, etc replicated n-times. Each database would need system resources and disk space. Not to mention the code needed to make Django aware of the split. You would have to get data from n databases instead of just one table in one database.\nAlso keep in mind that robust databases like PostgreSQL or MySQL are very capable of managing thousands or millions of records. They will do a better job out of the box than any code you may come up with. Just trust them with the data and if you notice a performance decline then you can find plenty of tips online to optimize them.","Q_Score":0,"Tags":"mysql,django,python-2.7","A_Id":26158170,"CreationDate":"2014-10-02T09:07:00.000","Title":"django multiple database for multiple organisation in a single project","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"How can i create Django sqlite3 dump file (*.sql) using terminal?\nThere is a fabric fabfile.py with certain dump scripts, but when i try to use fab command next massage shows up:\nThe program 'fab' is currently not installed.  To run fab please ask your administrator to install the package 'fabric'. \nBut there are fabric files in \/python2.7\/site-packages\/fabric\/.\nI'm not good at Django and Python at all. The guy, who was responsible for our Django project, just left without any explanations.\nIn general i need to know how to create Django sqlite3 dump file (*.sql) via terminal.\nHelp? :)","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1114,"Q_Id":26178633,"Users Score":0,"Answer":"You could also use fixtures. And generate fixtures for your app. Dependes on what you're planing to do with them.\nYou'll just make a loaddata after that.","Q_Score":0,"Tags":"python,django,database,sqlite","A_Id":26179396,"CreationDate":"2014-10-03T12:07:00.000","Title":"Django sqlite3 database dump","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am using Django 1.7 and I want to use MongoDB, So for that I try to install django-nonrel. Please let me know django-nonrel is compatible with Django 1.7?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":250,"Q_Id":26293481,"Users Score":0,"Answer":"Django-nonrel isn't \"compatible\" with anything. It is actually a fork of Django, currently based on the 1.5 release.","Q_Score":1,"Tags":"django,python-2.7,django-nonrel","A_Id":26293980,"CreationDate":"2014-10-10T06:49:00.000","Title":"does django-nonrel is compatible with django 1.7","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have been given a few TSV files containing data, around 800MB total in a couple of files.\nEach of them has columns that link up with columns in another file.\nI have so far imported all of my data into Python and stored it in an array. I now need to find a way to build a database out of this data without using any SQL, NoSQL, etc. \nIn the end I will be performing SQL-like queries on it (without SQL) and performing OLAP operations on the data. I can also NOT use any external libraries.\nAfter doing some research, I have came across using dictionaries as a way to do this project, but I am not sure how to go about linking the tables together with dictionary. Would it be a list of dictionaries?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":101,"Q_Id":26329613,"Users Score":1,"Answer":"Yes, you could fake a lot of DB operations with a nested dict structure. Top level is your \"tables\", each table has entries (use a \"primary key\" on these) and each entry is a dict of key:value pairs where keys are \"column names\" and values are, well, values. \nYou could even write a little sql-like query language on this if you wanted, but you'd want to start by writing some code to manage this. You don't want to be building this DB freehand, it'll be important to define the operations as code. For example, insert should deal with enforcing value restrictions and imposing defaults and setting auto-incrementing keys and so forth (if you really want to be \"performing sql like queries\" against it)","Q_Score":1,"Tags":"python,mysql,sql,database,nosql","A_Id":26329692,"CreationDate":"2014-10-12T20:25:00.000","Title":"Database-like operations without any database use","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am using Python to establish a connection to greenplum and run codes automatically. For that I am using these drivers \u00ad   psycopg2,\u00ad  psycopg2.extensions & psycopg2.extras. I also have to establish a connection to Teradata and run some codes and tranfer tables from Teradata to greenplum. Can someone please suggest some drivers or method to do this? I heard that arrays or alteryx can be used in python to do so but i couldn't anything.","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":694,"Q_Id":26418454,"Users Score":1,"Answer":"I'm guessing the data volumes are at least moderate in size - 10's of millions or greater.\n\nFastExport or Teradata Parallel Transport Export of the Teradata data to a\nflat file or named pipe. \nIngesting using Greenplum's preferred method for bulk\n    loading data from a flat file or named pipe.\n\nOther options may include invoking a Teradata FastExport API via JDBC using Python but then you still have to figure out how to efficiently ingest the data via Greenplum.","Q_Score":0,"Tags":"python,teradata,greenplum","A_Id":26425426,"CreationDate":"2014-10-17T05:31:00.000","Title":"How to tranfer data from Teradata to Greenplum using Python?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Is it possible? If so then how?   \nCurrently I'm inserting strings >16MB into GridFS one-by-one, but its very slow when dealing not with 1 string, but with thousands. I tried to check documentation, but didn't find a single line about bulk insert to GridFS storage, not just simple collection.  \nI'm using PyMongo for communication with MongoDB.","AnswerCount":3,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1705,"Q_Id":26429023,"Users Score":1,"Answer":"I read and researched all the answers but unfortunately they didn't fulfill my requirements. The data that I was needed to use for specifying _id of jsons in GridFS was actually stored inside of JSON itself. It sounds like worst idea ever including redundancy and etc, but unfortunately its requirement.\nWhat I did is I wrote insert thread for multiprocessing insertion to GridFS and inserted all the data with several threads (2 GridFS threads was enough to get proper performance).","Q_Score":1,"Tags":"python,mongodb,pymongo,bulkinsert,gridfs","A_Id":26662382,"CreationDate":"2014-10-17T16:03:00.000","Title":"Bulk insert to GridFS in MongoDB","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm new to Web Dev and I came across a problem. I was wondering if there's a Javascript Framework that will allow me to register and authenticate users to a database like when using PHP and MySql.\nAlso, when the user is granted access to the site, such user will be required to upload files that will be written to the local filesystem of that server.\nCan this be done with Javascript or some sort of Javascript Framework, or is it better just for me to learn PHP and do it in a normal LAMP stack? Or perhaps Ruby on Rails?\nI have been searching online but the majority of results are leaning towards PHP & MySql.\nThanks a lot!","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":959,"Q_Id":26518355,"Users Score":0,"Answer":"Welcome to the world of development.\nIn general, javascript is only used to give more resources to the user's navigation on the site (ex: visual effects).\nAs you're starting out, I advise you to start studying the part of the server-side login. For security purposes who confirms whether the user is logged in or not is always the server.\nSome developers prefer PHP, other developers love Ruby on Rails. Maybe your best friend prefer Python... It is your choice, they both are easy.","Q_Score":0,"Tags":"javascript,python,ruby-on-rails,angularjs,node.js","A_Id":26518519,"CreationDate":"2014-10-22T22:41:00.000","Title":"User Registration and Authentication to a Database using Javascript","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"since I could not find an answer to my question neither here nor in other forums, I decided to ask it to the community:\nDoes anybody know if and how it is possible to realize automatic documentation generation for code generated with Dymola?\nThe background for this e. g. is that I want\/need to store additional information within my model files to explain the concepts of my modelling and to store and get the documentation directly from the model code, which I would later like to be in a convenient way displayable not only from within Dymola, but also by a html and LaTeX documentation.\nI know that there exist several tools for automatic documentation generation like e. g. DoxyGen and Python Sphinx, but I could not figure out if the can be used with Dymola code. Plus, I am pretty new to this topic, so that I do not really know how to find out if they will work out.\nThank you people very much for your help!\nGreetings, mindm49907","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":274,"Q_Id":26529779,"Users Score":3,"Answer":"If you mean the Modelica model code, how does the HTML export in Dymola work for you? What's missing?\nIf you mean the C code generated by Dymola, the source code generation option enables more comments in the code.","Q_Score":1,"Tags":"doxygen,python-sphinx,documentation-generation,dymola","A_Id":26543595,"CreationDate":"2014-10-23T13:56:00.000","Title":"Automatic documentation generation for Dymola code","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm using celery with django and am storing the task results in the DB.\nI'm considering having a single set of workers reading messages from a single message broker. Now I can have multiple clients submitting celery tasks and each client will have tasks and their results created\/stored in a different DB.\nEven though the workers are common, they know which DB to operate upon for each task.\nCan I have duplicate task ids generated because they were submitted by different clients pointing to different DBs?\nThanks,","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":412,"Q_Id":26637631,"Users Score":1,"Answer":"Eventually you will have duplicates. Many people ignore this issue because it is a \"low probability\", and then are surprised when it hits them. And then a story leaks how someone was logged into another uses Facebook account. If you require them to always be unique then you will have to prefix each ID with something that will never repeat - like current date and time with microseconds.\nAnd if that is not good enough, because there still is a even tinier chance of a collision, you can create a small application that will generate those prefixes, and will add an counter (incremented after each hash request, and reset every couple seconds) to the date and microseconds. It will have to work in single-threaded mode, but this will be a guarantee to generate unique prefixes that won't collide.","Q_Score":0,"Tags":"python,django,celery,django-celery","A_Id":26644301,"CreationDate":"2014-10-29T18:06:00.000","Title":"Common celery workers for different clients having different DBs","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"Currently, I'm using Google's 2-step method to backup the datastore and than import it to BigQuery.\nI also reviewed the code using pipeline. \nBoth methods are not efficient and have high cost since all data is imported everytime.\nI need only to add the records added from last import.\nWhat is the right way of doing it?\nIs there a working example on how to do it in python?","AnswerCount":2,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":541,"Q_Id":26722127,"Users Score":2,"Answer":"There is no full working example (as far as I know), but I believe that the following process could help you :\n1- You'd need to add a \"last time changed\" to your entities, and update it. \n2- Every hour you can run a MapReduce job, where your mapper can have a filter to check for last time updated and only pick up those entities that were updated in the last hour\n3- Manually add what needs to be added to your backup.\nAs I said, this is pretty high level, but the actual answer will require a bunch of code. I don't think it is suited to Stack Overflow's format honestly.","Q_Score":2,"Tags":"python,google-app-engine,google-bigquery,google-cloud-datastore","A_Id":26722516,"CreationDate":"2014-11-03T20:00:00.000","Title":"Import Data Efficiently from Datastore to BigQuery every Hour - Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"If there a way using Whoosh to return the documents that have a field matching exactly the terms in a query?\nFor example, say I have a schema that has a autograph field that has three possible values; Autograph, Partial autograph, and No Autograph. If I do a standard query autograph:autograph, I get all the records. Because the term autograph is in all records. I have tried doing something like Term('autograph', 'autograph') and applying that to the filter key word argument for the search function, but I end up getting the same results.\nAm I doing something wrong?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":257,"Q_Id":26723964,"Users Score":0,"Answer":"I have come up with a solution, It works.\nFirst off, I redefined by schema so that autograph was an ID field in whoosh. Then I added a filter to the search call using a Regex query.\nThis works, but I am not going to accept it as the answer in hopes that there is a more elegant solution for filtering results.","Q_Score":2,"Tags":"python,whoosh","A_Id":26740422,"CreationDate":"2014-11-03T21:55:00.000","Title":"Whoosh: matching terms exactly","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a bottle+mongo application running in openshift. when I git-clone the application to my local computer neither the database nor the env-variables get download on my computer --just the  python files. Should I have to mimic the mongo part in my local computer to developed locally? Or I missing something here.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":47,"Q_Id":26921629,"Users Score":0,"Answer":"Yes. You have to run your own Mongodb server locally or port forward and use the OPENSHIFT Mongodb.","Q_Score":0,"Tags":"python,mongodb,openshift,bottle","A_Id":26922793,"CreationDate":"2014-11-14T01:43:00.000","Title":"openshift python mongodb local","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":0},{"Question":"I wrote a database program using SQLAlchemy. So far, I've been using FreeFileSync to sync the database file over the network for two computers when necessary. I want to learn how to set things up so that the file stays in one place and allows multiple user access but I don't know where to begin. \nIs it possible to open and read\/write to a SQLAlchemy database on another computer over a network? I couldn't find information on this (or maybe I just don't understand the terminology)?\nAre there any courses or topics I should look into that I will be able to apply with Python and SQLAlchemy?\nOr would making a web-based program be the best solution? I'm good at algorithms and scientific programming but I'm still a novice at network and web programming. I appreciate any tips on where to start.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":321,"Q_Id":26965270,"Users Score":0,"Answer":"I can't delete this question outright, so I will answer it with what I did.\nPart of the problem was that I was trying to find a solution for moving a sqlite3 database to a server, but it turns out that sqlite3 is only intended for use in simpler local situations. So I decided to migrate to MySQL. The following are the major steps:\n\nI took an old computer that has XP and installed Lubuntu 14.04 as the default OS. \nInstalled MySQL on Lubuntu: sudo apt-get install mysql-server.\nEdit the etc\/mysql\/my.cnf document's bind-address to match the computers network address.\nOn the client computer with Python 2.7 installed PyMySQL: easy_install PyMySQL\n\nWorks great. Now I'm in the process of making sure the program watches for changes to the database and updates the GUI accordingly.","Q_Score":0,"Tags":"python-2.7,sqlalchemy,multi-user","A_Id":27054069,"CreationDate":"2014-11-17T03:55:00.000","Title":"SQLAlchemy, how to transition from single-user to multi-user","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am getting this error when I am querying my rest app built with tornado, gevent, postgres and patched using psycogreen. I am constantly getting this error even when i am making requests at a concurrency of 10. If any one has a solution or info about what I might be doing wrong please share.\nError messages:\nProgrammingError: (ProgrammingError) execute cannot be used while an asynchronous query is underway\nProgrammingError: close cannot be used while an asynchronous query is underway\nStack Trace:\nFile \"\/ENV\/local\/lib\/python2.7\/site-packages\/sqlalchemy\/orm\/query.py\", line 2320, in all\n    return list(self)\n  File \"\/ENV\/local\/lib\/python2.7\/site-packages\/sqlalchemy\/orm\/query.py\", line 2438, in __iter__\n    return self._execute_and_instances(context)\n  File \"\/ENV\/local\/lib\/python2.7\/site-packages\/sqlalchemy\/orm\/query.py\", line 2453, in _execute_and_instances\n    result = conn.execute(querycontext.statement, self._params)\n  File \"\/ENV\/local\/lib\/python2.7\/site-packages\/sqlalchemy\/engine\/base.py\", line 729, in execute\n    return meth(self, multiparams, params)\n  File \"\/ENV\/local\/lib\/python2.7\/site-packages\/sqlalchemy\/sql\/elements.py\", line 322, in _execute_on_connection\n    return connection._execute_clauseelement(self, multiparams, params)\n  File \"\/ENV\/local\/lib\/python2.7\/site-packages\/sqlalchemy\/engine\/base.py\", line 826, in _execute_clauseelement\n    compiled_sql, distilled_params\n  File \"\/ENV\/local\/lib\/python2.7\/site-packages\/sqlalchemy\/engine\/base.py\", line 958, in _execute_context\n    context)\n  File \"\/ENV\/local\/lib\/python2.7\/site-packages\/sqlalchemy\/engine\/base.py\", line 1159, in _handle_dbapi_exception\n    exc_info\n  File \"\/ENV\/local\/lib\/python2.7\/site-packages\/sqlalchemy\/util\/compat.py\", line 199, in raise_from_cause\n    reraise(type(exception), exception, tb=exc_tb)\n  File \"\/ENV\/local\/lib\/python2.7\/site-packages\/sqlalchemy\/engine\/base.py\", line 951, in _execute_context\n    context)\n  File \"\/ENV\/local\/lib\/python2.7\/site-packages\/sqlalchemy\/engine\/default.py\", line 436, in do_execute\n    cursor.execute(statement, parameters)\nProgrammingError: (ProgrammingError) execute cannot be used while an asynchronous query is underway","AnswerCount":1,"Available Count":1,"Score":0.3799489623,"is_accepted":false,"ViewCount":1803,"Q_Id":27025622,"Users Score":2,"Answer":"You are probably using the same connection with two different cursors concurrently.","Q_Score":2,"Tags":"python-2.7,sqlalchemy,tornado,psycopg2,gevent","A_Id":27316073,"CreationDate":"2014-11-19T19:45:00.000","Title":"ProgrammingError: close cannot be used while an asynchronous query is underway","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Sorry i deleted my code because i realized i wasn't supposed to put it up","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":76,"Q_Id":27093359,"Users Score":1,"Answer":"You are getting this error because the __init__() function in your class requires 3 arguments - new_dict, coloumn_name, and coloumn_value - and you did not supply them.","Q_Score":0,"Tags":"python","A_Id":27093407,"CreationDate":"2014-11-23T19:35:00.000","Title":"How do you get a column name and row from table?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm looking for open-ended advice on the best approach to re-write a simple document control app I developed, which is really just a custom file log generator that looks for and logs files that have a certain naming format and file location. E.g., we name all our Change Orders with the format \"CO#3 brief description.docx\". When they're issued, they get moved to an \"issued\" folder under another folder that has the project name. So, by logging the file and querying it's path, we can tell which project it's associated with and whether it's been issued. \nI wrote it with Python 3.3. Works well, but the code's tough to support because I'm building the reports while walking the file structure, which can get pretty messy. I'm thinking it would be better to build a DB of most\/all of the files first and then query the DB with SQL to build the reports.\nSorry for the open-ended question, but I'm hoping not to reinvent the wheel. Anyone have any advice as to going down this road? E.g., existing apps I should look at or bundles that might help? I have lots of C\/C++ coding experience but am still new to Python and MySQL. Any advice would be greatly appreciated.","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":92,"Q_Id":27096588,"Users Score":1,"Answer":"Firstly, if it works well as you suggest, then why fix it? \nSecondly, before doing any changes to your code I would ask myself the following questions:\n\nWhat are the improvements\/new requirements I want to implement that I can't easily do with the current structure?\nDo I have a test suite of the current solution, so that I can regression-test any refactoring? When re-implementing something it is easy to overlook some specific behaviors which are not very well documented but that you\/users rely on. \nDo those improvements warrant an SQL database? For instance:\n\nDo you need to often run reports out of an SQL database without walking the directory structure? \nIs there a problem with walking the directories? \nDo you have network or performance issues? \nAre you facing an increase in usage?\n\nWhen implementing an SQL solution, you will need a new task to update the SQL data. If I understand correctly, the reports are currently generated on-the-fly, and therefore are always up-to-date. That won't be the case with SQL reports, so you need to make sure they are up-to-date too. How frequently will you update the SQL database: \n\na) In real-time? That will necessitate a background service. That could be a operational hassle. \nb) On-demand? Then what would be the difference with the current solution?\nc) At scheduled times? Then your data may be not up-to-date between the updates. \n\n\nI don't have any packages or technical approaches to recommend to you, I just thought I'd give you those general software management advices. \nIn any case, I also have extensive C++ and Python and SQL experience, and I would just stick to Python on this one. \nOn the SQL side, why stick to traditional SQL engines? Why not MongoDB for instance, which would be well suited to storing structured data such as file information.","Q_Score":0,"Tags":"python,mysql,file","A_Id":30106383,"CreationDate":"2014-11-24T01:24:00.000","Title":"Need advice on writing a document control software with Python and MySQL","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am trying to build a simple login \/ register system with python sockets and Tkinter. \nIt might sound like a stupid question, but I really couldn't find by searching in Google.\nI am wondering if using sqlite3 for storing username and password (with a server) is a good idea. If No, please explain why shouldn't I use sqlite3 and what is the alternative for this need.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1093,"Q_Id":27134539,"Users Score":2,"Answer":"You'll need to store the names and (secured) passwords on the server.  SQLite is a perfectly good solution for this but there are many, many other ways to do it.  If your application does not otherwise use a database for storage there's no need to add database support just for this simple task.  Assuming that you don't have a very large and every-growing list of users it could be as easy as pickling Python dictionary.","Q_Score":1,"Tags":"python,database,python-2.7,sqlite","A_Id":27134845,"CreationDate":"2014-11-25T18:57:00.000","Title":"Should I use sqlite3 for storing username and password with python?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am using Ubuntu 14.04 and trying to run snoopy_auth which is a part of the snoopy-ng application I downloaded and installed from their GitHub.\nWhen running, I get an error that is documented on snoopy-ng's GitHub page, which says that it works using version 0.7.8.\nHow can I downgrade sqlalchemy to 0.7.8?\nThe error looks like:\nsnoopy_auth -l\n[+] Available drone accounts:\nTraceback (most recent call last):\n  File \"\/usr\/bin\/snoopy_auth\", line 103, in \n    drones = auth_.manage_drone_account(\"foo\", \"list\")\n  File \"\/usr\/bin\/snoopy_auth\", line 29, in manage_drone_account\n    self.db.create(self.drone_tbl_def )\n  File \"\", line 2, in create\n  File \"\/usr\/local\/lib\/python2.7\/dist-packages\/sqlalchemy\/util\/deprecations.py\", line 106, in warned\n    return fn(*args, **kwargs)\n  File \"\/usr\/local\/lib\/python2.7\/dist-packages\/sqlalchemy\/engine\/interfaces.py\", line 859, in create\n    raise NotImplementedError()\nNotImplementedError","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1813,"Q_Id":27161760,"Users Score":2,"Answer":"To get passed this error I just simply ran the command:\nsudo easy_install \"SQLAlchemy==0.7.8\"\nThe virtual environments do seem like the preferred method though, so hopefully I don't run into any additional problems from downgrading system-wide.","Q_Score":1,"Tags":"python,linux,python-2.7,ubuntu,sqlalchemy","A_Id":27371294,"CreationDate":"2014-11-27T01:37:00.000","Title":"How can I remove version 0.9.7 of sqlalchemy and install 0.7.8 instead?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a working Django 1.6 project using sqlite deployed in Digital Ocean, Ubuntu.\nI use Git to update my project on server side. (Git clone and git pull thereafter)\nMy question is: every time after I update my database locally (e.g. added some new tables), how can I synchronise with the server one? Using git pull results in conflicts that cannot be resolved. I can do it using git fetch --all and git reset --HARD. But it doesn't seem to be the correct way.\nAny help is greatly appreciated! Thank you in advance.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":860,"Q_Id":27162982,"Users Score":2,"Answer":"Follow the following steps to push from local and pull to server.\n\nmake changes to models.py\nUse this cmd to add change to git . > git add models.py\nuse this cmd to commit > git commit -m \"your message\"\ngit push > this will push your local changes to repo.\ngo to sever now.\nrun cmd >  git status\nsee if there are any local changes done to models.py file.\nyou can see those local changes using > git diff models.py\nIf those changes are already in your repo. use this cmd to discard them > git checkout models.py\nNow run cmd which will take your latest changes from server.>  git pull \n\nP.S. : Use the same commands for all the changes made to any file into the clone.\nSouth migrations for syncing database: \nInitial :\n1. python manage.py schemamigration  --initial\n2. python manage.py migrate  --fake\nDo any change to database and do following steps: \n1. python manage.py schemamigration  --auto\n2. python manage.py migrate \nDo not checkin the migration folder created in app as it will conflict between your local and production clone.\nNote: All the history for south migrations are stored in south_migrations table in database.","Q_Score":0,"Tags":"python,django,database,git","A_Id":27163084,"CreationDate":"2014-11-27T04:17:00.000","Title":"How to synchronise local Django sqlite database with the server one?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have uploaded some data into Elastic server as \" job id , job place , job req , job desc \". My index is my_index and doctype = job_list.\nI need to write a query to find a particular term say \" Data Analyst \" and it should give me back matching results with a specified field like \" job place \" .\nie, Data Analyst term matching in the documents , and I need to have all \"job place\" information only.\nAny help. I tried curd . but not working. if it is in python good.","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":5426,"Q_Id":27166357,"Users Score":1,"Answer":"the above search example looks correct.Try lowercasing the Data \"Analyst\" as \"data analyst\".\nif doesn't help post your mappings,query you firing and response you are getting.","Q_Score":0,"Tags":"python,search,curl,elasticsearch","A_Id":27177167,"CreationDate":"2014-11-27T08:43:00.000","Title":"Elastic Search query filtering","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm working on a multithreaded application that uses the SQLAlchemy ORM. It already uses scoped_session with the thread as its scope, but we are having some issues when we pass an ORM object from a worker thread back to the main thread. Since the objects are attached to the worker thread's session, when the worker thread is shut down, we start getting DetachedInstanceErrors on those objects. \nIs there a way I can generically tell the ORM objects to detach\/reattach themselves to the correct session as needed? We spawn a new thread whenever we have a slow operation that we don't want locking up our UI, so putting the reattach code in everywhere we spawn a new thread would be a mess. \nI think we also need to be able to clone the ORM object when we spawn the thread, so that we can have one in the main thread and one in the worker thread. I see a \"merge\" but no \"split\". Is this possible?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1254,"Q_Id":27193849,"Users Score":5,"Answer":"Session.merge() is enough and should do what you're after, but even then it gets fiddly with threads. You might want to rethink this.\nPass the primary key(s) to the worker instead of the objects, and then handle object loading and the actual work in the worker itself. No messing around with threading and open\/closed sessions that will eventually lead to headaches. Once the workers can deal with the objects separately, you could even move the workers to a separate process (similar to what Celery does).","Q_Score":2,"Tags":"python,multithreading,sqlalchemy","A_Id":27194059,"CreationDate":"2014-11-28T17:57:00.000","Title":"SQLAlchemy ORM: safely passing objects between threads without manually reattaching?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Right now I'm using print(), calling the variables I want that are stored in a tuple and then formatting them using: print(format(x,\"<10s\")+ format(y,\"<40s\")...) but this gives me output that isn't aligned in a column form. How do I make it so that each row's element is aligned?\nSo, my code is for storing student details. First, it takes a string and returns a tuple, with constituent parts like: (name,surname,student ID, year).\nIt reads these details from a long text file on student details, and then it parses them through a tuplelayout function (the bit which will format the tuple) and is meant to tabulate the results.\nSo, the argument for the tuplelayout function is a tuple, of the form:\nsurname | name | reg number | course | year","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":5713,"Q_Id":27196501,"Users Score":0,"Answer":"My shell has the font settings changed so the alignment was off. Back to font: \"Courier\" and everything is working fine.\nSorry.","Q_Score":1,"Tags":"python,formatting,tabular","A_Id":27209158,"CreationDate":"2014-11-28T22:07:00.000","Title":"Format strings to make 'table' in Python 3","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm trying to delete cells from an Excel spreadsheet using openpyxl.  It seems like a pretty basic command, but I've looked around and can't find out how to do it.  I can set their values to None, but they still exist as empty cells.  worksheet.garbage_collect() throws an error saying that it's deprecated.  I'm using the most recent version of openpyxl.  Is there any way of just deleting an empty cell (as one would do in Excel), or do I have to manually shift all the cells up?  Thanks.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":2658,"Q_Id":27259478,"Users Score":4,"Answer":"In openpyxl cells are stored individually in a dictionary. This makes aggregate actions like deleting or adding columns or rows difficult as code has to process lots of individual cells. However, even moving to a tabular or matrix implementation is tricky as the coordinates of each cell are stored on each cell meaning that you have process all cells to the right and below an inserted or deleted cell. This is why we have not yet added any convenience methods for this as they could be really, really slow and we don't want the responsibility for that.\nHoping to move towards a matrix implementation in a future version but there's still the problem of cell coordinates to deal with.","Q_Score":1,"Tags":"python,excel,openpyxl","A_Id":27280801,"CreationDate":"2014-12-02T21:38:00.000","Title":"Delete cells in Excel using Python 2.7 and openpyxl","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Is it just about creating models that use the best fitting data store API?\nFor part of the data I need relations, joins and sum(). For other this is not necessary but nosql way is more appropriate.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":62,"Q_Id":27278297,"Users Score":0,"Answer":"MySQL commands cannot be run on NoSQL. You will need to do some conversions during manipulation of the data from both DBs.","Q_Score":1,"Tags":"google-app-engine,google-cloud-storage,google-cloud-datastore,mysql-python,app-engine-ndb","A_Id":28197823,"CreationDate":"2014-12-03T17:47:00.000","Title":"can I combine NDB and mysqldb in one app on google cloud platform","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I am dealing with some performance issues whilst working with a very large dataset. The data is a pairwise distance matrix of ~60k entries. The resulting vectors have been generated in the following format:\nmol_a,mol_b,score, year_a, year_b\n 1,1,1,year,year\n 1,2,x,year,year\n 1,3,y,year,year\n ...\n 1,60000,z,year,year\n 2,1,x,year,year\n 2,2,1,year,year\n ...\nwhere mol_a and mol_b are unique molecules (INTs) and score is their jaccard\/tanimoto similarity score (FLOAT\/REAL) and year_a and b are dates (INT(4)) that are associated with mol_a and b respectively. Since this is a distance matrix the values are reflected across the diagonal ie\n0 1 2 3 \n1 1 x y\n2 x 1 z\n3 y z 1\nThe resulting file has ~3.6 billion rows and becomes a ~100GB sqlite3 db. It take about 10 hours to make using all the PRAGMA tweaks I have read and doing executemany in 5 million entry batches. I would love to throw away half of it while building the but I can't think of a good way of doing this without ending up building a (prohibitively) giant list in memory... It's constructed via 2 nested for loops:\nfor i in MolList: \n     for j in MolList:\n         a = calculate_score(i,j)\n         write_buffer.append(a)\nThough the creation is slow it is not the prohibitive part, the actual analysis i want to do with it is.. I will be grouping things by year_a and year_b so I started creating an index on year_a, year_b and score to have a 'Covering Index' but the build is 13 hours in and occasionally using mass amounts of harddrive space on my c: drive (which is a small SSD vs the raid where the database is). The whole thing is running on 12 core workstation with 16GB of ram, Windows 7 on a 240GB SSD and data storage on a 1TB Raid 1 array (built in MoBo controller).\nI have also been attempting to build a MySql database on a small little ubuntu server that I have (intel core duo 2ghz 4GB ram 128GB SSD) but the python inserts across the network are taking forever! and I'm not convinced I'll see any real improvements.\nSQLite from what I've read seems like what I really wanted, essentially this would all be handled in Python memory if I had ~150GB of RAM at my disposal, but I needed a file based storage solution which seems like exactly what SQLite was designed for. However watching SQLite consume a pittance of memory and CPU while Disk IO bounces around 5MB\/s chugs away makes me think that disk is just a bottleneck.  \nWhat are my options for streamlining this process on a single node (aka no Hadoop clusters at my disposal)? I'm a DB newb so please keep suggestions within the realm of possibility. Having never worked with datasets in the billions I don't quite know what I'm in for but would greatly appreciate help\/advice from this sage community.","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":314,"Q_Id":27322027,"Users Score":0,"Answer":"You have several options. The simplest is to simply save the output in chunks instead (say save one file for all the 1st molecule 'distance' scores, a second file for the second molecule distances, etc., with 60,000 files in all). That would allow you to also process your work in batches, and then aggregate to get the combined result.\nIf that's not possible due to operations you need to do, you can perhaps sign up for a free Amazon Web Services Trial and upload the data to a Redshift server instance there, it has very good compression (>10x is common), is frighteningly fast for data analysis, and if you know SQL, you should be fine.","Q_Score":2,"Tags":"python,mysql,sql,sqlite","A_Id":27323942,"CreationDate":"2014-12-05T18:04:00.000","Title":"database solution for very large table","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I recently downloaded the xlsxwriter version 0.6.4 and installed it on my computer.  It correctly added it to my C:\\Python27\\Lib\\site-packages\\xlsxwriter folder, however when I try to import it I get the error ImportError: No module named xlsxwriter.  The traceback is File \"F:\\Working\\ArcGIS\\ArcGIS .py\\Scripts\\Append_Geodatabase.py\".\nHowever if I try to import numpy (I can't remember what numby is, however it is located in the same site-packages folder C:\\Python27\\Lib\\site-packages\\numpy) it has no problem.\nAny idea of what could be causing this issue?\nThanks for the help.","AnswerCount":9,"Available Count":4,"Score":0.022218565,"is_accepted":false,"ViewCount":200367,"Q_Id":27385097,"Users Score":1,"Answer":"I am not sure what caused this but it went all well once I changed the path name from Lib into lib and I was finally able to make it work.","Q_Score":38,"Tags":"python-2.7,xlsxwriter","A_Id":42188912,"CreationDate":"2014-12-09T17:29:00.000","Title":"ImportError: No module named xlsxwriter","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I recently downloaded the xlsxwriter version 0.6.4 and installed it on my computer.  It correctly added it to my C:\\Python27\\Lib\\site-packages\\xlsxwriter folder, however when I try to import it I get the error ImportError: No module named xlsxwriter.  The traceback is File \"F:\\Working\\ArcGIS\\ArcGIS .py\\Scripts\\Append_Geodatabase.py\".\nHowever if I try to import numpy (I can't remember what numby is, however it is located in the same site-packages folder C:\\Python27\\Lib\\site-packages\\numpy) it has no problem.\nAny idea of what could be causing this issue?\nThanks for the help.","AnswerCount":9,"Available Count":4,"Score":0.0,"is_accepted":false,"ViewCount":200367,"Q_Id":27385097,"Users Score":0,"Answer":"I found the same error when using xlsxwriter in my test.py application. First, check if you have xlsxwriter module installed or not.\nsudo pip install xlsxwriter\nThen check the python version you are using, The following worked for me\npython2 test.py","Q_Score":38,"Tags":"python-2.7,xlsxwriter","A_Id":67318348,"CreationDate":"2014-12-09T17:29:00.000","Title":"ImportError: No module named xlsxwriter","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I recently downloaded the xlsxwriter version 0.6.4 and installed it on my computer.  It correctly added it to my C:\\Python27\\Lib\\site-packages\\xlsxwriter folder, however when I try to import it I get the error ImportError: No module named xlsxwriter.  The traceback is File \"F:\\Working\\ArcGIS\\ArcGIS .py\\Scripts\\Append_Geodatabase.py\".\nHowever if I try to import numpy (I can't remember what numby is, however it is located in the same site-packages folder C:\\Python27\\Lib\\site-packages\\numpy) it has no problem.\nAny idea of what could be causing this issue?\nThanks for the help.","AnswerCount":9,"Available Count":4,"Score":0.022218565,"is_accepted":false,"ViewCount":200367,"Q_Id":27385097,"Users Score":1,"Answer":"in VSCode:\ninstead of activating your environment with script use python select interpreter\nfrom VSCode(press ctrl + shift + p)\nand then select your environment from the list (marked with recommended)","Q_Score":38,"Tags":"python-2.7,xlsxwriter","A_Id":72355605,"CreationDate":"2014-12-09T17:29:00.000","Title":"ImportError: No module named xlsxwriter","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I recently downloaded the xlsxwriter version 0.6.4 and installed it on my computer.  It correctly added it to my C:\\Python27\\Lib\\site-packages\\xlsxwriter folder, however when I try to import it I get the error ImportError: No module named xlsxwriter.  The traceback is File \"F:\\Working\\ArcGIS\\ArcGIS .py\\Scripts\\Append_Geodatabase.py\".\nHowever if I try to import numpy (I can't remember what numby is, however it is located in the same site-packages folder C:\\Python27\\Lib\\site-packages\\numpy) it has no problem.\nAny idea of what could be causing this issue?\nThanks for the help.","AnswerCount":9,"Available Count":4,"Score":0.1106561105,"is_accepted":false,"ViewCount":200367,"Q_Id":27385097,"Users Score":5,"Answer":"I managed to resolve this issue as follows...\nBe careful, make sure you understand the IDE you're using! - Because I didn't.\nI was trying to import xlsxwriter using PyCharm and was returning this error.\nAssuming you have already attempted the pip installation (sudo pip install xlsxwriter) via your cmd prompt, try using another IDE e.g. Geany - & import xlsxwriter.\nI tried this and Geany was importing the library fine. I opened PyCharm and navigated to 'File>Settings>Project:>Project Interpreter' xlslwriter was listed though intriguingly I couldn't import it! I double clicked xlsxwriter and hit 'install Package'... And thats it! It worked!\nHope this helps...","Q_Score":38,"Tags":"python-2.7,xlsxwriter","A_Id":50458074,"CreationDate":"2014-12-09T17:29:00.000","Title":"ImportError: No module named xlsxwriter","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"my job id is  job_7mb6iw3BHoMRC09US9Vqq-Qd06s, while uploading data by this job on Bigquery  The data was not getting uploaded on bigquery. And I am not getting any error for this.","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":95,"Q_Id":27416642,"Users Score":1,"Answer":"That job failed with reason \"invalid\" and message starting with \"Too many errors encountered.\"\nIn order to detect job failure, when you get a successful response from jobs.get, first ensure that the job is in a DONE state, then look for the presence of errors in the status.errorResult.reason and status.errorResult.message. Additionally, the status.errorStream will contain a list of individual failures encountered. In this case, it looks like the job was trying to load data that didn't match the schema of the table. You can find the file\/line\/field offsets in the \"location\" field of each error in the errorStream.\nHere are a couple of causes for \"not finding the errors in the job\" that we've seen:\n\nForgetting to check for DONE before looking for job errors.\nWaiting for job completion with a timeout, but forgetting to treat timeout as failure.\nLetting temporary errors from jobs.get (5xx http response codes) terminate your wait loop early, and then not knowing the state of the job since the jobs.get itself failed.\n\nI hope this helps narrow down the problem for you.","Q_Score":0,"Tags":"google-app-engine,python-2.7,google-bigquery","A_Id":27449004,"CreationDate":"2014-12-11T06:26:00.000","Title":"Bigquery data not getting uploaded","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"My goal was to duplicate my Google App Engine application. I created new application, and upload all needed code from source application(python). Then I uploaded previously created backup files from the Cloud Storage  of the source application (first I downloaded those files to PC and than uploaded files to GCS bucket of the target app)\nAfter that I tried to restore data from those files, by using \"Import Backup Information\" button.\nBackup information file is founded and I can add it to the list of available backups. But when I try to do restore I receive error: \"There was a problem kicking off the jobs. The error was: Backup not readable\"\nAlso I tried to upload those files back to original application and I was able to restore from them, by using the same procedure, so the files are not corrupted.\nI know there are another methods of copying data between applications, but I wanted to use this method. If for example, my Google account is being hacked and I can not access my original application data, but I have all backup data on my hard drive. Then I can simply create new app and copy all data to the new app...\nHas anyone before encountered with the similar problem, and maybe found some solution?\nThanks!","AnswerCount":2,"Available Count":2,"Score":0.3799489623,"is_accepted":false,"ViewCount":961,"Q_Id":27514985,"Users Score":4,"Answer":"Yes!! What you are trying to do is not possible. The reason is that there are absolute references in the backup files to the original backup location (bucket). So moving the files to another GCS location will not work.\nInstead you have to leave the backup files in the original GCS bucket and give your new project read access to that folder. That is done in the \"Edit bucket permissions\" option. eg. add:\nProject - owners-12345678 - Reader\nNow you are able to import from that bucket in your new project in \"Import Bucket Information\".","Q_Score":8,"Tags":"python,google-app-engine","A_Id":34706288,"CreationDate":"2014-12-16T22:17:00.000","Title":"Backup in one and restore in another Google App Engine application by using Cloud Storage?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"My goal was to duplicate my Google App Engine application. I created new application, and upload all needed code from source application(python). Then I uploaded previously created backup files from the Cloud Storage  of the source application (first I downloaded those files to PC and than uploaded files to GCS bucket of the target app)\nAfter that I tried to restore data from those files, by using \"Import Backup Information\" button.\nBackup information file is founded and I can add it to the list of available backups. But when I try to do restore I receive error: \"There was a problem kicking off the jobs. The error was: Backup not readable\"\nAlso I tried to upload those files back to original application and I was able to restore from them, by using the same procedure, so the files are not corrupted.\nI know there are another methods of copying data between applications, but I wanted to use this method. If for example, my Google account is being hacked and I can not access my original application data, but I have all backup data on my hard drive. Then I can simply create new app and copy all data to the new app...\nHas anyone before encountered with the similar problem, and maybe found some solution?\nThanks!","AnswerCount":2,"Available Count":2,"Score":0.0996679946,"is_accepted":false,"ViewCount":961,"Q_Id":27514985,"Users Score":1,"Answer":"Given the message, my guess is that the target application has no read access to the bucket where the backup is stores. Add the application to the permitted users to that bucket before creating the backup so that the backup objects will inherit the permission.","Q_Score":8,"Tags":"python,google-app-engine","A_Id":29852870,"CreationDate":"2014-12-16T22:17:00.000","Title":"Backup in one and restore in another Google App Engine application by using Cloud Storage?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I get an error when trying to run ogr2ogr thru subprocess but I am able to run it using just the windows command prompt. The script will be part of a series of processes that start with batch importing gpx files unto a postgres db. Can somebody please tell me what's wrong? Thanks!\n::::::::::::::::::::::::::::\nRunning THIS script gives me an ERROR: 'ogr2ogr' is not recognized as an internal or external command, operable program or batch file.\n\nimport subprocess\nimport sys\nprint sys.executable\ntrack= \"20131007.gpx\" \nsubprocess.call([\"ogr2ogr\", \"-f\", \"PostgreSQL\", \"PG:dbname=TTBASEMain host=localhost port=5432 user=postgres password=minda\", track], shell=True)\n\n:::::::::::::::::::::::::::::\nTHIS CODE does its job well.\n\nogr2ogr -f PostgreSQL PG:\"dbname='TTBASEMain' host='localhost' port='5432' user='postgres' password='minda'\" \"20131007.gpx\"\n\n:::::::::::::::::::::::::::::\nTHIS is what I have in my environment path:\n\nC:\\Users\\User>path\n  PATH=C:\\Program Files (x86)\\Intel\\iCLS Client\\;C:\\Program Files\\Intel\\iCLS Client\\;C:\\Program Files (x86)\\NVIDIA Corporation\\PhysX\\Common;C:\\windows\\system32;C:\\windows;C:\\windows\\System32\\Wbem;C:\\windows\\System32\\WindowsPowerShell\\v1.0\\;C:\\Program Files (x86)\\Intel\\OpenCL SDK\\3.0\\bin\\x86;C:\\Program Files (x86)\\Intel\\OpenCL SDK\\3.0\\bin\\x64;C:\\Program Files\\Intel\\Intel(R) Management Engine Components\\DAL;C:\\Program Files\\Intel\\Intel(R) Management Engine Components\\IPT;C:\\Program Files (x86)\\Intel\\Intel(R) Management Engine Components\\DAL;C:\\Program Files (x86)\\Intel\\Intel(R) Management Engine C\n  omponents\\IPT;C:\\Program Files\\Lenovo\\Bluetooth Software\\;C:\\Program Files\\Lenovo\\Bluetooth Software\\syswow64;C:\\lastools\\bin;C:\\Python27;C:\\Python27\\Scripts;C:\\Python27\\DLLs;C:\\Python27\\Lib\\site-packages;C:\\Users\\User\\AppData\\Roaming.local\\bin;C:\\Program Files (x86)\\Windows Kits\\8.1\\Windows Performance Toolkit\\;C:\\Program Files\\Microsoft SQL Server\\110\\Tools\\Binn\\;C:\\Program Files\\GDAL","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1962,"Q_Id":27567450,"Users Score":0,"Answer":"REINSTALLING the python bindings resolved my issue. I don't see GDAL on the paths below but its working now. Is it supposed to be there so since its not, I might probably have another round of GDAL head scratching in the future?\n:::::::::::::::::::::::::::::::::::::::\nTHIS is what I currently have when I type in sys.path on python:\n\nMicrosoft Windows [Version 6.2.9200]\n  (c) 2012 Microsoft Corporation. All rights reserved.\nC:\\Users\\User>python\n  Python 2.7.8 (default, Jun 30 2014, 16:08:48) [MSC v.1500 64 bit (AMD64)] on win32\n  Type \"help\", \"copyright\", \"credits\" or \"license\" for more information.\n\n\nimport sys\n      sys.path\n      ['', 'C:\\windows\\SYSTEM32\\python27.zip', 'C:\\Python27\\DLLs', 'C:\\Python27\\lib', 'C:\\Python27\n      \\lib\\plat-win', 'C:\\Python27\\lib\\lib-tk', 'C:\\Python27', 'C:\\Python27\\lib\\site-packages', '\n      C:\\Python27\\lib\\site-packages\\wx-3.0-msw']","Q_Score":0,"Tags":"python-2.7,subprocess","A_Id":27570551,"CreationDate":"2014-12-19T13:48:00.000","Title":"ERROR: 'ogr2ogr' is not recognized as an internal or external command, operable program or batch file when running ogr2ogr in python script","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":0},{"Question":"I'm using the mySQLdb module within my django application which is linked to Apache via WSGI.\nHowever I'm getting permission issues (shown below). This is down to SElinux and if I set it to passive everything is ok.\n\nImproperlyConfigured: Error loading MySQLdb module:\n  \/opt\/django\/virtenv\/django15\/lib\/python2.7\/site-packages\/_mysql.so:\n  failed to map segment from shared object: Permission denied\n\nWhat is the best way to update SELinux to include this without having to turn off the whole the thing. The error is shown below:\n\nImproperlyConfigured: Error loading MySQLdb module:\n  \/opt\/django\/virtenv\/django1\/lib\/python2.7\/site-packages\/_mysql.so: \n  cfailed to map segment from shared object: Permission denied","AnswerCount":4,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1090,"Q_Id":27584508,"Users Score":0,"Answer":"Couple of permission issues that I notice:\n\nMake sure your credentials for mySQLdb have access to the database.\nIf you are using IP and Port to connect to the database, try using localhost.\nMake sure the user (chmod permissions) have access to the folder where mySQL stores stuff. Sometimes when storing media and things it need permission to the actual folder.\nLastly, I would try to reset Apache server (not the entire machine).","Q_Score":8,"Tags":"python,django,mysql-python,selinux","A_Id":27734160,"CreationDate":"2014-12-20T21:29:00.000","Title":"Python MySQLdb with SELinux","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am trying to get writing privileges to my sqlite3.db file in my django project hosted on bluehost, but I cannot get any other chmod command to work besides the dangerous\/risky chmod 777. When I chmod 777 the db file and the directory, everything works perfectly. \nHowever, in order to be more prudent, I\u2019ve tried chmodding 775 the directory of the sqlite file and chmod 664 the actual db file itself. No luck. I still get OperationalError: Attempt to Write to a Read Only Database whenever I access a feature that requires writing to the db. \nI appreciate any assistance.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":310,"Q_Id":27594703,"Users Score":1,"Answer":"The user accessing the database (www-data?) needs to have write privileges to the folder the data resides in as well as the file itself.  I would probably change the group ownership (chgrp) of the folder to www-data and add a group sticky bit to the folder as well (chmod g+s dbfolder).  The last one makes sure that any new files created belongs to the group owner.\nIf you're on bluehost you should also have access to MySql (which is a much better choice for web-facing db).","Q_Score":2,"Tags":"python,django,sqlite","A_Id":27594818,"CreationDate":"2014-12-21T23:04:00.000","Title":"Django on CentOS\/Bluehost: Attempt to Write a Readonly Database, which Chmod besides 777 to use?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I use python 2.7.3 and Windows7. \n\nI want to decorate the Excel chart by using Python.\nIt's not necessary to make charts from start to end.\nFirst step(EXCEL STEP), I store data in the Excel sheet and make line chart roughly.\n(by selecting data range and using hot-key 'ALT+N+N+enter')\nNext step(PYTHON STEP), I want to modify chart made in first step.\nSpecifically border line color and width, chart size, label fonts, fonts size and so on.\nHow can I select or activate existing Excel chart by Python?(Not create chart from Python)","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":191,"Q_Id":27596890,"Users Score":0,"Answer":"It seems that all the python module could only create excels but not activate existing charts. Try xlrd and xlwt. Good luck.","Q_Score":0,"Tags":"python,excel,charts","A_Id":27599618,"CreationDate":"2014-12-22T05:11:00.000","Title":"Selecting or activating existing Excel chart","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm developing intranet web app that is based on Pyramid with SQLAlchemy.\nIt eventually may (will) happen that 2 users will edit the same record. How can I handle the requirement to notify the user who started editing later that particular record is being edited by the first user?","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":55,"Q_Id":27616098,"Users Score":0,"Answer":"You need a table with current editor, record_id and timeout. The first editor asks per POST-request to edit a record and you put a new line in this table, with a reasonable timeout, say 5 min. The first editor gets an \"ok\" in return. For the second editor you find a match for the record_id in the table, look at the timeout, and if it's not timed out, (s)he gets an \"error\" in return to the post request. In an second POST-request, an editor send it's changes. You look in the table, if (s)he's the editor and send \"changed\" or \"rejected\" accordingly.","Q_Score":1,"Tags":"python,web,pyramid","A_Id":27616278,"CreationDate":"2014-12-23T07:44:00.000","Title":"Notifying user's browser of change without websockets","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am generating load test data in a Python script for Cassandra.\nIs it better to insert directly into Cassandra from the script, or to write a CSV file and then load that via Cassandra?\nThis is for a couple million rows.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":364,"Q_Id":27678990,"Users Score":0,"Answer":"For a few million, I'd say just use CSV (assuming rows aren't huge); and see if it works. If not, inserts it is :)\nFor more heavy duty stuff, you might want to create sstables and use sstable loader.","Q_Score":0,"Tags":"python,cassandra,load-testing","A_Id":27688141,"CreationDate":"2014-12-28T17:47:00.000","Title":"Python\/Cassandra: insert vs. CSV import","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a typical Django project with one primary database where I keep all the data I need.\nSuppose there is another DB somewhere with some additional information. That DB isn't directly related to my Django project so let's assume I do not even have a control under it.\nThe problem is that I do ont know if I need to create and maintain a model for this external DB so I could use Django's ORM. Or maybe the best solution is to use raw SQL to fetch data from external DB and then use this ifo to filter data from primary DB using ORM, or directly in views.\nThe solution with creating a model seems to be quite ok but the fact that DB isn't a part of my project means I am not aware of possible schema changes and looks like it's a bad practice then.\nSo in the end if I have some external resources like DBs that are not related to but needed for my project should I:\n\nTry to create django models for them\nUse raw SQL to get info from external DB and then use it for filtering data from the primary DB with ORM as well as using data directly in views if needed\nUse raw SQL both for a primary and an external DB where they intersect in app's logic","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":437,"Q_Id":27742457,"Users Score":0,"Answer":"I would create the minimal django models on the external databases => those that interact with your code:\nSeveral outcomes to this\n\nIf parts of the database you're not interested in change, it won't have an impact on your app.\nIf the external models your using change, you probably want to be aware of that as quickly as possible (your app is likely to break in that case too).\nAll the relational databases queries in your code are handled by the same ORM.","Q_Score":1,"Tags":"python,django","A_Id":27744297,"CreationDate":"2015-01-02T12:45:00.000","Title":"Django models with external DBs","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a Python client program (which will be available to a limited number of users) that fetches data from a remote MySQL-DB using the pymysql-Module.\nThe problem is that the login data for the DB is visible for everyone who takes a look at the code, so everyone could manipulate or delete data in the DB. Even if I would store the login data in an encrypted file, some still could edit the code and insert their own MySql queries (and again manipulate or delete data).\nSo how can I access the DB from my program and still SELECT, DELETE or UPDATE data in it, but make sure that no one can execute his own (evil) SQL Code (except the ones that are triggered by using the GUI)?","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":934,"Q_Id":27743031,"Users Score":0,"Answer":"This happens to be one of the reasons desktop client-server architecture gave way to web architecture. Once a desktop user has access to a dbms, they don't have to use just the SQL in your application. They can do whatever their privileges allow.\nIn those bad old days, client-server apps only could change rows in the DBMS via stored procedures. They didn't have direct privileges to INSERT, UPDATE, or DELETE rows. The users of those apps had accounts that were GRANTed a limited set of privileges; they could SELECT rows and run procedures, and that was it. They certainly did not have any create \/ drop \/ table privilege.\n(This is why a typical DBMS has such granular privilege control.)\nYou should restrict the privileges of the account or accounts employed by the users of your desktop app. (The same is, of course, true for web app access accounts.) Ideally, each user should have her own account. It should only grant access to the particular database your application needs.\nThen, if you don't trust your users to avoid trashing your data, you can write, and test, and deploy, stored procedures to do every insert, update, or delete needed by your app. \nThis is a notoriously slow and bureaucratic way to get IT done; you may want to make good backups and trust your users, or switch to a web app.\nIf you do trust them tolerably well, then restrict them to the particular database employed by your app.","Q_Score":1,"Tags":"python,mysql,pymysql","A_Id":27743210,"CreationDate":"2015-01-02T13:31:00.000","Title":"Secure MySQL login data in a Python client program","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am connecting to MySQL database using torndb in Python. Is there a way to switch between databases after connection is established? Like the select_db method?","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":106,"Q_Id":27760817,"Users Score":0,"Answer":"this ultimately will be decided if the database is running on the same host and in the instance of MySQL.  If it is running in the same instance you should be able to prefix your tables names with the database name. For example; \"select splat from foo.bar where splat is not null\"  where foo is the database name and bar is the table name.  Hope this helps!","Q_Score":0,"Tags":"python,tornado","A_Id":27760934,"CreationDate":"2015-01-03T23:45:00.000","Title":"Torndb - Switch from one database to another","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am connecting to MySQL database using torndb in Python. Is there a way to switch between databases after connection is established? Like the select_db method?","AnswerCount":2,"Available Count":2,"Score":0.1973753202,"is_accepted":false,"ViewCount":106,"Q_Id":27760817,"Users Score":2,"Answer":"Switch db:\n\nconn.execute('use anotherDBName');","Q_Score":0,"Tags":"python,tornado","A_Id":27765801,"CreationDate":"2015-01-03T23:45:00.000","Title":"Torndb - Switch from one database to another","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm running Django with Postgres database. On top of application-level security checks, I'm considering adding database-level restrictions. E.g. the application code should only be able to INSERT into log tables, and not UPDATE or DELETE from them. \nI would manually create database user with appropriate grants for this. I would also need a more powerful user for running database migrations.\nMy question is, do people practice things like this? Any advice, best practices on using restricted database users with Django? \nEdit: To clarify, there's no technical problem, I'm just interested to hear other people's experiences and takeaways. One Django-specific thing is, I'll need at least two DB users: for normal operation and for running migrations. Where do I store credentials for the more privileged user? Maybe make manage.py migrate prompt for password? \nAs for the reasoning, suppose my app has a SQL injection vulnerability. With privileged user, the attacker can do things like drop all tables. With a more limited user there's slightly less damage potential and afterwards there's some evidence in insert-only log tables.","AnswerCount":3,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":1088,"Q_Id":27819930,"Users Score":0,"Answer":"Yes, this is practiced sometimes, but not commonly. The best way to do it is to grant specific privileges on user, not in django. Making such restrictions means that we should not trust application, because it might change some files \/ data in db in the way that we do not expect it to do so.\nSo, to sum up: create another user able to create \/ modify data and user another one with restrictions to use normally.\nIt's also quite common in companies to create one user to insert data and another one for employees \/ scripts to access it.","Q_Score":2,"Tags":"python,django,database,postgresql,security","A_Id":27964212,"CreationDate":"2015-01-07T12:50:00.000","Title":"Restricted database user for Django","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm running Django with Postgres database. On top of application-level security checks, I'm considering adding database-level restrictions. E.g. the application code should only be able to INSERT into log tables, and not UPDATE or DELETE from them. \nI would manually create database user with appropriate grants for this. I would also need a more powerful user for running database migrations.\nMy question is, do people practice things like this? Any advice, best practices on using restricted database users with Django? \nEdit: To clarify, there's no technical problem, I'm just interested to hear other people's experiences and takeaways. One Django-specific thing is, I'll need at least two DB users: for normal operation and for running migrations. Where do I store credentials for the more privileged user? Maybe make manage.py migrate prompt for password? \nAs for the reasoning, suppose my app has a SQL injection vulnerability. With privileged user, the attacker can do things like drop all tables. With a more limited user there's slightly less damage potential and afterwards there's some evidence in insert-only log tables.","AnswerCount":3,"Available Count":2,"Score":0.0665680765,"is_accepted":false,"ViewCount":1088,"Q_Id":27819930,"Users Score":1,"Answer":"For storing the credentials to the privileged user for management commands, when running manage.py you can use the --settings flag, which you would point to another settings file that has the other database credentials.\nExample migrate command using the new settings file:\npython manage.py migrate --settings=myapp.privileged_settings","Q_Score":2,"Tags":"python,django,database,postgresql,security","A_Id":27972123,"CreationDate":"2015-01-07T12:50:00.000","Title":"Restricted database user for Django","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I've gone through many threads related to installing mysql-python in a virtualenv, including those specific to users of Percona. None have solved my problem thus far.\nWith Percona, it is normal to get a long error on pip install MySQL-python in the virtualenv that ultimately says EnvironmentError: mysql_config not found. One method to remedy this is yum install mysql-devel, which I've done. I can actually get mysql-python to install properly outside of the virtualenv via yum.\nI'm getting the error in the virtualenv only - it uses Python 2.7.9, wheareas 2.6.6 is what comes with Centos.\nAlso, with MySQL-python installed via yum it will import to the OS's python interpreter, but will not import into the virtualenv's python interpreter. \nTo clarify, I only installed mysql-python via yum to see whether or not it would work that way. I would prefer it be by pip, in the environment only. \nWhat am I missing here? As far as I'm aware it should work - considering it will work outside of virtualenv.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":110,"Q_Id":27828737,"Users Score":1,"Answer":"Found the solution! \nI think it was improper of my to install mysql-devel in the first place, so I went ahead and uninstalled it. \nInstead, I used a packaged supplied by Percona - Percona-Server-devel-55\nyum install Percona-Server-devel-55 and the problem is solved!","Q_Score":1,"Tags":"python-2.7,virtualenv,mysql-python,centos6,percona","A_Id":27829817,"CreationDate":"2015-01-07T21:11:00.000","Title":"Unable to get these to cooperate: mysql-python + virtualenv + percona + centos6","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a python script set up that captures game data from users while the game is being played. The end goal of this is to get all that data, from every user, into a postgresql database on my web server where it can all be collated and displayed via django\nThe way I see it, I have 2 options to accomplish this:\n\nWhile the python script is running, I can directly open a connection to the db and upload to it in real time\nDuring the game session, instead of uploading to the db directly, I can save out a csv file to their computer and have a separate app that will find these log files and upload them to the db at a later point\n\nI like (1) because it means these log files cannot be tampered with by the user as it is going straight to the db - therefore we can prevent forgery and ensure valid data.\nI like (2) because the initial python script is something that every user would have on their computer, which means they can open it at will (it must be this way for it to work with the game). In other words, if I went with (1) users would be exposed to the user\/pass details for connecting to the db which is not secure. With (2) the app can just be an exe where you cant see the source code and cant see the db login details\nMy questions:\n\nSo in one case I'd be exposing login details, in the other I'd be risking end users tampering with csv files before uploading. Is there a method that could combine the pros of the 2 methods without having to deal with the cons?\nAt the very least, if I had to choose either of these 2 methods, whats the best way to get around its downfall? So is it possible to prevent exposing db credentials in a publicly available python script? And if I have to save out csv files, is there a way to prevent tampering or checking if it has been tampered with?","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":70,"Q_Id":27885733,"Users Score":1,"Answer":"The script makes a POST request to your Django web server either with login\/pwd or unique string.\nThe web server validates credentials and inserts data into DB.","Q_Score":0,"Tags":"python,postgresql,security,csv","A_Id":27885848,"CreationDate":"2015-01-11T09:46:00.000","Title":"Clients uploading to database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I need to backup the current db while logged into odoo. I should be able to do it using a button, so that suppose I click on the button, it works the same way as odoo default backup in manage databases, but I should be able to do it from within while logged in.\nIs there any way to achieve this? I do know that this is possible from outside odoo using bash but thats not what I want.","AnswerCount":9,"Available Count":1,"Score":0.022218565,"is_accepted":false,"ViewCount":4840,"Q_Id":27935745,"Users Score":1,"Answer":"You can use a private browser session to access the Database menu, from the login screen, and perform the the backup form there (you need to know the master password to access that, defined in the server configuration file).","Q_Score":13,"Tags":"python,openerp,odoo","A_Id":28070202,"CreationDate":"2015-01-14T04:11:00.000","Title":"Backup Odoo db from within odoo","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Python 2.7 and 3.4 co-exist in my mac-os. After installing the official mysql connector (downloaded from dev.mysql.com), import mysql.connector can only pass in python 2.7. Is there any way for the connector to work for both python versions?","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":569,"Q_Id":28039131,"Users Score":0,"Answer":"Relative to Python 3.6:\nThe official mysql connector only worked in python 2.7 after i installed it on OSX.\nAs an alternative I used the easy_install-3.6 python module integrated in python 3.6\n\nGo to directory: \/Library\/Frameworks\/Python.framework\/Versions\/3.6\/bin\ncommand: easy_install-3.6 mysql-connector-python","Q_Score":0,"Tags":"python,mysql,mysql-python,mysql-connector,python-3.4","A_Id":47486286,"CreationDate":"2015-01-20T06:36:00.000","Title":"mysql-python connector work with python2.7 and 3.4 at the same time","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I want to build an universal database in which I will keep data from multiple countries so I will need to work with the UNICODE charset.\nI need a little help in order to figure out which is the best way to work with stuff like that and how my queries will be affected ( some sql example queries from php\/python for basic stuff like insert\/update\/select would also be great)\nThank you.","AnswerCount":2,"Available Count":2,"Score":0.0996679946,"is_accepted":false,"ViewCount":1733,"Q_Id":28096856,"Users Score":1,"Answer":"just put a N infront of the string, something like INSERT INTO MYTABLE VALUES(N\"xxx\") and make sure your column type is nvarchar","Q_Score":0,"Tags":"php,python,sql,unicode","A_Id":28096917,"CreationDate":"2015-01-22T19:13:00.000","Title":"How to insert UNICODE characters to SQL db?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I want to build an universal database in which I will keep data from multiple countries so I will need to work with the UNICODE charset.\nI need a little help in order to figure out which is the best way to work with stuff like that and how my queries will be affected ( some sql example queries from php\/python for basic stuff like insert\/update\/select would also be great)\nThank you.","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":1733,"Q_Id":28096856,"Users Score":0,"Answer":"there is nothing special you need to do.\nwith php you can do... query(\"SET NAMES utf8\");","Q_Score":0,"Tags":"php,python,sql,unicode","A_Id":28096868,"CreationDate":"2015-01-22T19:13:00.000","Title":"How to insert UNICODE characters to SQL db?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"i installed PyCharm 4 on my Mac Yosemite, then installed SQLAlchemy through easy_install with console, also I have already official python 2.7.9 IDLE. I tried to import SQLAlchemy module in official IDLE and it works, but in PyCharm 4 IDE it doesn't. How can i fix this error?\nTraceback (most recent call last): File \"\/Users\/artyom\/PycharmProjects\/untitled\/hella.py\", line 1, in  import sqlalchemy ImportError: No module named sqlalchemy","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":664,"Q_Id":28121229,"Users Score":0,"Answer":"Go into Settings -> Project Settings -> Project Interpreter.\nThen press configure interpreter, and navigate to the \"Paths\" tab.\nPress the + button in the Paths area. You can put the path to the module you'd like it to recognize.","Q_Score":0,"Tags":"macos,sqlalchemy,pycharm,osx-yosemite,python-2.x","A_Id":28123162,"CreationDate":"2015-01-24T01:10:00.000","Title":"SQLAlchemy with Pycharm 4","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Many spreadsheets have formulas and formatting that Python tools for reading and writing Excel files cannot faithfully reproduce. That means that any file I want to create programmatically must be something I basically create from scratch, and then other Excel files (with the aforementioned sophistication) have to refer to that file (which creates a variety of other dependency issues).\nMy understanding of Excel file 'tabs' is that they're actually just a collection of XML files. Well, is it possible to use pandas (or one of the underlying read\/write engines such as xlsxwriter or openpyxl to modify just one of the tabs, leaving other tabs (with more wicked stuff in there) intact?\nEDIT: I'll try to further articulate the problem with an example.\n\nExcel Sheet test.xlsx has four tabs (aka worksheets): Sheet1, Sheet2, Sheet3, Sheet4\nI read Sheet3 into a DataFrame (let's call it df) using pandas.read_excel()\nSheet1 and Sheet2 contain formulas, graphs, and various formatting that neither openpyxl nor xlrd can successfully parse, and Sheet4 contains other data. I don't want to touch those tabs at all.\nSheet2 actually has some references to cells on Sheet3\nI make some edits to df and now want to write it back to sheet3, leaving the other sheets untouched (and the references to it from other worksheets in the workbook intact)\n\nCan I do that and, if so, how?","AnswerCount":6,"Available Count":1,"Score":1.0,"is_accepted":false,"ViewCount":32281,"Q_Id":28142420,"Users Score":6,"Answer":"I'm 90% confident the answer to \"can pandas do this\" is no.  Posting a negative is tough, because there always might be something clever that I've missed, but here's a case: \nPossible interface engines are xlrd\/xlwt\/xlutils, openpyxl, and xlsxwriter.  None will work for your purposes, as xlrd\/wt don't support all formulae, xlsxwriter can't modify existing xlsx files, and openpyxl loses images and charts.\nSince I often need to do this, I've taken to only writing simple output to a separate file and then calling the win32api directly to copy the data between the workbooks while preserving all of my colleague's shiny figures.  It's annoying, because it means I have to do it under Windows instead of *nix, but it works.\nIf you're working under Windows, you could do something similar.  (I wonder if it makes sense to add a native insert option using this approach to help people in this situation, or if we should simply post a recipe.)\n\nP.S.: This very problem has annoyed me enough from time to time that I've thought of learning enough of the modern Excel format to add support for this to one of the libraries.\nP.P.S.: But since ignoring things you're not handling and returning them unmodified seems easy enough, the fact that no one seems to support it makes me think there are some headaches, and where Redmond's involved I'm willing to believe it.  @john-machin would know the details, if he's about..","Q_Score":26,"Tags":"python,excel,pandas","A_Id":28254411,"CreationDate":"2015-01-25T22:38:00.000","Title":"Can Pandas read and modify a single Excel file worksheet (tab) without modifying the rest of the file?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Recently I've been receiving this error regarding what appears to be an insufficiency in connection slots along with many of these Heroku errors:\n\nH18 - Request Interrupted\nH19 - Backend connection timeout\nH13 - Connection closed without response\nH12 - Request timeout\n\nError\ndjango.db.utils.OperationalError in \/\nFATAL: remaining connection slots are reserved for non-replication superuser connections\nCurrent Application setup:\n\nDjango 1.7.4\nPostgres\nHeroku (2x 2 dynos, Standard-2) 5ms response time, 13rpm Throughput\n\nAre there general good practices for where one should or should not perform querysets in a Django application, or when to close a database connection?\nI've never experienced this error before. I have increased my dynos on heroku and allocated significantly more RAM and I am still experiencing the same issue.\nI've found similar questions on Stack Overflow but I haven't been able to figure out what might be causing the issue exactly.\nI have querysets in Model methods, views, decorator views, context processors.\nMy first inclination would be that there is an inefficient queryset being performed somewhere causing connections to remain open that eventually crashes the application with enough people accessing the website.\nAny help is appreciated. Thanks.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":3434,"Q_Id":28238144,"Users Score":4,"Answer":"I realized that I was using the django server in my procfile. I accidentally commented out and commited it to heroku instead of using gunicorn. Once I switched to gunicorn on the same heroku plan the issue was resolved.\nUsing a production level application server really makes a big difference. Also don't code at crazy hours of the day when you're prone to errors.","Q_Score":2,"Tags":"python,django,postgresql,heroku,django-queryset","A_Id":28395905,"CreationDate":"2015-01-30T14:35:00.000","Title":"Django\/Postgres: FATAL: remaining connection slots are reserved for non-replication superuser connections","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I've written a python\/webdriver script that scrapes a table online, dumps it into a list and then exports it to a CSV.  It does this daily.\nWhen I open the CSV in Excel, it is unformatted, and there are fifteen (comma-delimited) columns of data in each row of column A.\nOf course, I then run 'Text to Columns' and get everything in order.  It looks and works great.\nBut tomorrow, when I run the script and open the CSV,  I've got to reformat it.\nHere is my question:   \"How can I open this CSV file with the data already spread across the columns in Excel?\"","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":24,"Q_Id":28238830,"Users Score":0,"Answer":"Try importing it as a csv file, instead of opening it directly on excel.","Q_Score":1,"Tags":"python,excel,csv","A_Id":28238935,"CreationDate":"2015-01-30T15:11:00.000","Title":"Retain Excel Settings When Adding New CSV","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Most of the Flask tutorials and examples I see use an ORM such as SQLAlchemy to handle interfacing with the user database. If you have a general working knowledge of SQL, is this extra level of abstraction, heavy with features, necessary? I am tempted to write a lightweight interface\/ORM of my own so I better understand exactly what's going on and have full control over the queries, inserts, etc. But are there pitfalls to this approach that I am not considering that may crop up as the project gets more complex, making me wish I used a heavier ORM like SQLAlchemy?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":970,"Q_Id":28271711,"Users Score":0,"Answer":"No, an ORM is not required, just incredibly convenient.  SQLAlchemy will manage connections, pooling, sessions\/transactions, and a wide variety of other things for you.  It abstracts away the differences between database engines.  It tracks relationships between tables in convenient collections.  It generally makes working with complex data much easier.\nIf you're concerned about performance, SQLAlchemy has two layers, the orm and the core.  Dropping down to the core sacrifices some convenience for better performance.  It won't be as fast as using the database driver directly, but it will be fast enough for most use cases.\nBut no, you don't have to use it.","Q_Score":2,"Tags":"python,sql,orm,flask,sqlalchemy","A_Id":28280443,"CreationDate":"2015-02-02T05:39:00.000","Title":"Handling user database in flask web app without ORM like SQLAlchemy","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I save my data on RethinkDB Database. As long as I dont restart the server, all is well. But when I restart, it gives me an error saying database doesnt exist, although the folder and data does exist in folder rethinkdb_data. What is the problem ?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":897,"Q_Id":28329352,"Users Score":10,"Answer":"You're almost certainly not losing data, you're just starting RethinkDB without pointing it to the data. Try the following:\n\nStart RethinkDB from the directory that contains the rethinkdb_data directory.\nAlternatively, pass the -d flag to RethinkDB to point it to the directory that contains rethinkdb_data. For example, rethinkdb -d \/path\/to\/data\/directory\/rethinkdb_data","Q_Score":7,"Tags":"python,ubuntu-14.04,rethinkdb,rethinkdb-python","A_Id":28330153,"CreationDate":"2015-02-04T19:04:00.000","Title":"RethinkDB losing data after restarting server","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm trying to pip install pymssql in my Centos 6.6, but kept on experiencing this error:\n\n_mssql.c:314:22: error: sqlfront.h: No such file or directory\n  cpp_helpers.h:34:19: error: sybdb.h: No such file or directory\n\nI already installed freetds, freetds-devel, and cython.\nAny ideas? Thanks in advance!","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":2708,"Q_Id":28343666,"Users Score":2,"Answer":"Looking at the full traceback we see that include_dirs includes \/usr\/local\/include but the header files are in \/usr\/include which I imagine has to do with the fact python 2.7 is not the system python.\nYou can change the setup.py script to include  \/usr\/include or copy the files into \/usr\/local\/include","Q_Score":1,"Tags":"python,python-2.7,pip,pymssql","A_Id":28349658,"CreationDate":"2015-02-05T12:12:00.000","Title":"Installing pymssql in Centos 6.6 64-bit","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I m building a web crawler and I wanted to save links in a database with informations like type, size, etc.\nand actually I don't know when I should commit the database (how often)\nin other terms: is it a problem if I commit the database every 0.1 second?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":67,"Q_Id":28400064,"Users Score":0,"Answer":"In terms of logical correctness, you should commit every time a set of one or more queries that are supposed to execute atomically (i.e, all of them, or else none of them, execute) is finished.\nThere is no connection between this logical correctness and any given amount of time between commits.  In your vaguely-sketched use case, I guess I'd be committing every time I'm done with a whole web page -- what I want to avoid is likely the committing of a web page that's \"partially done\" but not completely so -- whether that means 100 msec, or 50, or 200 -- why should that duration matter?","Q_Score":0,"Tags":"python,sqlite","A_Id":28400155,"CreationDate":"2015-02-08T22:23:00.000","Title":"Python sqlite3 correct use of commit","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"i Launch cluster spark cassandra with datastax dse in aws cloud. So my dataset storage in S3. But i don't know how transfer data from S3 to my cluster cassandra. Please help me","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1657,"Q_Id":28417806,"Users Score":1,"Answer":"The details depend on your file format and C* data model but it might look something like this:\n\nRead the file from s3 into an RDD\nval rdd = sc.textFile(\"s3n:\/\/mybucket\/path\/filename.txt.gz\")\nManipulate the rdd\nWrite the rdd to a cassandra table:\nrdd.saveToCassandra(\"test\", \"kv\", SomeColumns(\"key\", \"value\"))","Q_Score":0,"Tags":"python,cassandra,datastax-enterprise","A_Id":28419293,"CreationDate":"2015-02-09T19:34:00.000","Title":"How import dataset from S3 to cassandra?","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I've been looking for ways to do this and haven't found a good solution to this. I'm trying to copy a sheet in an .xlsx file that has macros to another workbook. I know I could do this if the sheet contained data in each cell but that's not the case. The sheet contains checkboxes and SOME text. Is there a way to do this in python (or any other language for that matter?) I just need it done programmatically as it will be part of a larger script.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":194,"Q_Id":28423604,"Users Score":0,"Answer":"Try win32com package.\nThis offers an interface of VBA for python\nYou can find it on SourceForge.\nI've done some projects with this package, we can discuss more on your problem if this package helps.","Q_Score":0,"Tags":"python,xlsx,xlsxwriter","A_Id":28946313,"CreationDate":"2015-02-10T03:32:00.000","Title":"Copy sheet with Macros to workbook in Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Is it possible to connect a Flask app to a database using MySQLdb-python and vertica_python? It seems that the recommended Flask library for accessing databases is Flask-SQLAlchemy.  I have an app that connects to MySQL and Vertica databases, and have written a GUI wrapper for it in Flask using flask-wtforms, but am just getting an error when I try to test a Vertica or MySQL connection through the flask app. Is there a reason that I cannot use the prior libraries that I was using within my app?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":224,"Q_Id":28489779,"Users Score":0,"Answer":"Yes, it is possible. I was having difficulties debugging because of the opacity of the error, but ran it with app.run(debug=True), and managed to troubleshoot my problem.","Q_Score":0,"Tags":"python,flask,flask-sqlalchemy","A_Id":28502445,"CreationDate":"2015-02-12T23:21:00.000","Title":"Can I connect a flask app to a database using MySQLdb-python vertica_python?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Currently I am installing psycopg2 for work within eclipse with python.\nI am finding a lot of problems: \n\nThe first problem sudo pip3.4 install psycopg2 is not working and it is showing the following message \n\n\nError: pg_config executable not found.\n\nFIXED WITH:export PATH=\/Library\/PostgreSQL\/9.4\/bin\/:\"$PATH\u201d\n\nWhen I import psycopg2 in my project i obtein:\n\n\nImportError:\n  dlopen(\/Library\/Frameworks\/Python.framework\/Versions\/3.4\/lib\/python3.4\/site-packages\/psycopg2\/_psycopg.so\n  Library libssl.1.0.0.dylib\n  Library libcrypto.1.0.0.dylib\n\nFIXED WITH: \nsudo ln -s \/Library\/PostgreSQL\/9.4\/lib\/libssl.1.0.0.dylib \/usr\/lib\nsudo ln -s \/Library\/PostgreSQL\/9.4\/lib\/libcrypto.1.0.0.dylib \/usr\/lib\n\nNow I am obtaining:\n\n\nImportError:\n  dlopen(\/Library\/Frameworks\/Python.framework\/Versions\/3.4\/lib\/python3.4\/site-packages\/psycopg2\/_psycopg.so,\n  2): Symbol not found: _lo_lseek64   Referenced from:\n  \/Library\/Frameworks\/Python.framework\/Versions\/3.4\/lib\/python3.4\/site-packages\/psycopg2\/_psycopg.so\n  Expected in: \/usr\/lib\/libpq.5.dylib  in\n  \/Library\/Frameworks\/Python.framework\/Versions\/3.4\/lib\/python3.4\/site-packages\/psycopg2\/_psycopg.so\n\nCan you help me?","AnswerCount":8,"Available Count":2,"Score":1.0,"is_accepted":false,"ViewCount":17998,"Q_Id":28515972,"Users Score":13,"Answer":"I was able to fix this on my Mac (running Catalina, 10.15.3) by using psycopg2-binary rather than psycopg2.\n\npip3 uninstall psycopg2\npip3 install psycopg2-binary","Q_Score":48,"Tags":"python,eclipse,macos,postgresql,psycopg2","A_Id":60101069,"CreationDate":"2015-02-14T13:12:00.000","Title":"Problems using psycopg2 on Mac OS (Yosemite)","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":0},{"Question":"Currently I am installing psycopg2 for work within eclipse with python.\nI am finding a lot of problems: \n\nThe first problem sudo pip3.4 install psycopg2 is not working and it is showing the following message \n\n\nError: pg_config executable not found.\n\nFIXED WITH:export PATH=\/Library\/PostgreSQL\/9.4\/bin\/:\"$PATH\u201d\n\nWhen I import psycopg2 in my project i obtein:\n\n\nImportError:\n  dlopen(\/Library\/Frameworks\/Python.framework\/Versions\/3.4\/lib\/python3.4\/site-packages\/psycopg2\/_psycopg.so\n  Library libssl.1.0.0.dylib\n  Library libcrypto.1.0.0.dylib\n\nFIXED WITH: \nsudo ln -s \/Library\/PostgreSQL\/9.4\/lib\/libssl.1.0.0.dylib \/usr\/lib\nsudo ln -s \/Library\/PostgreSQL\/9.4\/lib\/libcrypto.1.0.0.dylib \/usr\/lib\n\nNow I am obtaining:\n\n\nImportError:\n  dlopen(\/Library\/Frameworks\/Python.framework\/Versions\/3.4\/lib\/python3.4\/site-packages\/psycopg2\/_psycopg.so,\n  2): Symbol not found: _lo_lseek64   Referenced from:\n  \/Library\/Frameworks\/Python.framework\/Versions\/3.4\/lib\/python3.4\/site-packages\/psycopg2\/_psycopg.so\n  Expected in: \/usr\/lib\/libpq.5.dylib  in\n  \/Library\/Frameworks\/Python.framework\/Versions\/3.4\/lib\/python3.4\/site-packages\/psycopg2\/_psycopg.so\n\nCan you help me?","AnswerCount":8,"Available Count":2,"Score":0.0996679946,"is_accepted":false,"ViewCount":17998,"Q_Id":28515972,"Users Score":4,"Answer":"I am using yosemite, postgres.app & django. this got psycopg2 to load properly for me but the one difference was that my libpq.5.dylib file is in \/Applications\/Postgres.app\/Contents\/Versions\/9.4\/lib.\nthus my second line was sudo ln -s  \/Applications\/Postgres.app\/Contents\/Versions\/9.4\/lib\/libpq.5.dylib \/usr\/lib","Q_Score":48,"Tags":"python,eclipse,macos,postgresql,psycopg2","A_Id":28949608,"CreationDate":"2015-02-14T13:12:00.000","Title":"Problems using psycopg2 on Mac OS (Yosemite)","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":0},{"Question":"I have a python process serving as a WSGI-apache server. I have many copies of this process running on each of several machines. About 200 megabytes of my process is read-only python data. I would like to place these data in a memory-mapped segment so that the processes could share a single copy of those data. Best would be to be able to attach to those data so they could be actual python 2.7 data objects rather than parsing them out of something like pickle or DBM or SQLite.\nDoes anyone have sample code or pointers to a project that has done this to share?","AnswerCount":4,"Available Count":1,"Score":0.049958375,"is_accepted":false,"ViewCount":1046,"Q_Id":28570438,"Users Score":1,"Answer":"One possibility is to create a C- or C++-extension that provides a Pythonic interface to your shared data. You could memory map 200MB of raw data, and then have the C- or C++-extension provide it to the WSGI-service. That is, you could have regular (unshared) python objects implemented in C, which fetch data from some kind of binary format in shared memory. I know this isn't exactly what you wanted, but this way the data would at least appear pythonic to the WSGI-app.\nHowever, if your data consists of many many very small objects, then it becomes important that even the \"entrypoints\" are located in the shared memory (otherwise they will waste too much memory). That is, you'd have to make sure that the PyObject* pointers that make up the interface to your data, actually themselves point to the shared memory. I.e, the python objects themselves would have to be in shared memory. As far as I can read the official docs, this isn't really supported. However, you could always try \"handcrafting\" python objects in shared memory, and see if it works. I'm guessing it would work, until the Python interpreter tries to free the memory. But in your case, it won't, since it's long-lived and read-only.","Q_Score":11,"Tags":"python,shared-memory,wsgi,uwsgi","A_Id":30273392,"CreationDate":"2015-02-17T20:23:00.000","Title":"How to store easily python usable read-only data structures in shared memory","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a file that is several G in size and contains a JSON hash on each line.  The document itself is not a valid JSON document, however I have no control over the generation of this data so I cannot change it.\nThe JSON needs to be read, lookups need to be performed on certain \"fields\" in the JSON and then the result of these lookups needs to be inserted into a MySQL database.\nAt the moment, it is taking hours to process this file and I think that it is because I am inserting and commiting on each row instead of using executemany, however I'm struggling to work out how best to approach this because I need to do the lookups as part of the process and then insert into multiple tables.\nThe process is effectively as follows:\n1) Iterate over the file, reading each line as we go\n2) For each line, work out if it needs to be inserted into the database\n3) If the line does need to be inserted into the database, look up foreign keys for various JSON fields and replace them with the FK id\n4) Insert the \"new\" line into the database.\nThe issue comes at (3) as there are some cases where the FK id is created by an insert of a subset of the data.\nIn short, I need to do a mass insert of a nested data structure with various parts of the nested data needing to be inserted into different tables whilst maintaining referential integrity.\nThanks for all and any help,\nMatt","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":76,"Q_Id":28579257,"Users Score":1,"Answer":"1) filter out the lines you can ignore.\n2) work out your table dependency graph and partition rows into multiple files by table.\n3) insert all rows for tables without dependencies; optionally, cache these so you don't have to ask the DB what you just told it for lookups.\nN) use that cache + do any DB lookups required to insert rows that depend on rows inserted in step N-1.\n\nDo all this as multiple processes so you can verify each stage. Use bulk inserts and consider disabling FK verification.","Q_Score":1,"Tags":"python,mysql,json,database","A_Id":34722784,"CreationDate":"2015-02-18T08:42:00.000","Title":"Mass insert of data with intermediate lookups using Python and MySQL","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"Query results from some Postgres data types are converted to native types by  psycopg2.  Neither pgdb (PostgreSQL) and cx_Oracle seem to do this.\n\u2026so my attempt to switch pgdb out for psycopg2cffi is proving difficult, as there is a fair bit of code expecting strings, and I need to continue to support cx_Oracle.\nThe psycopg2 docs explain how to register additional types for conversion, but I'd actually like to remove that conversion if possible and get the strings as provided by Postgres.  Is that doable?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":274,"Q_Id":28597575,"Users Score":3,"Answer":"You can re-register a plain string type caster for every single PostgreSQL type (or at least for every type you expect a string for in your code): when you register a type caster for an already registered OID the new definition takes precedence. Just have a look at the source code of psycopg (both C and Python) to find the correct OIDs.\nYou can also compile your own version of psycopg disabling type casting. I don't have the source code here right now but probably is just a couple line changes.","Q_Score":2,"Tags":"postgresql,psycopg2,python-db-api","A_Id":28602221,"CreationDate":"2015-02-19T02:11:00.000","Title":"Can one disable conversion to native types when using psycopg2?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I need to process a lot of .xls files which come out of this Microscopy image analysis software called Aperio (after analysis with Aperio, it allows you to export the data as \"read-only\" xls format. The save-as only works in Excel on a Mac, on windows machine, the save and save as buttons are greyed out since the files are protected). Unfortunately, the header of these files are not standard OLE2 format. Therefore, they cannot be picked up with Java API POI unless they are manually loaded in Microsoft Excel and save as .xls one by one. \nSince there are so many of them in the directory, it would be pretty painful to do the save-as by hand. Is there a way to write a Java program to automatically save these files as standard xls files? If it is impossible for Java, what other language can handle this situation, Python?\nEdit:\nI loaded one of the files in hex reader and here it is:\n09 04 06 00 07 00 10 00 00 00 5C 00 04 00 05 4D 44 41 80 00 08 00 00 00 00 00 00 00 00 00 92 00 19 00 06 00 00 00 00 00 F0 F0 F0 00 00 00 00 00 FF FF FF 00 00 00 00 00 FF FF FF 0C 00 02 00 01 00 0D 00 02 00 64 00 0E 00 02 00 01 00 0F 00 02 00 01 00 11 00 02 00 00 00 22 00 02 00 00 00 2A 00 02 00 00 00 2B 00 02 00 00 00 25 02 04 00 00 00 FF 00 1F 00 02 00 22 00 1E 04 0A 00 00 00 07 47 65 6E 65 72 61 6C 1E 04 04 00 00 00 01 30 1E 04 07 00 00 00 04 30 2E 30 30 1E 04 08 00 00 00 05 23 2C 23 23 30 1E 04 0B 00 00 00 08 23 2C 23 23 30 2E 30 30 1E 04 18 00 00 00 15 23 2C 23 23 30 5F F0 5F 2E 3B 5C 2D 23 2C 23 23 30 5F F0 5F 2E 1E 04 1D 00 00 00 1A 23 2C 23 23 30 5F F0 5F 2E 3B 5B 52 65 64 5D 5C 2D 23 2C 23 23 30 5F F0 5F 2E 1E 04 1E 00 00 00 1B 23 2C 23 23 30 2E 30 30 5F F0 5F 2E 3B 5C 2D 23 2C 23 23 30 2E 30 30 5F F0 5F 2E 1E 04 23 00 00 00 20 23 2C 23 23 30 2E 30 30 5F F0 5F 2E 3B 5B 52 65 64 5D 5C 2D 23 2C 23 23 30 2E 30 30 5F F0 5F 2E 1E 04 18 00 00 00 15 23 2C 23 23 30 22 F0 2E 22 3B 5C 2D 23 2C 23 23 30 22 F0 2E 22 1E 04 1D 00 00 00 1A 23 2C 23 23 30 22 F0 2E 22 3B 5B 52 65 64 5D 5C 2D 23 2C 23 23 30 22 F0 2E 22 1E 04 1E 00 00 00 1B 23 2C 23 23 30 2E 30 30 22 F0 2E 22 3B 5C 2D 23 2C 23 23 30 2E 30 30 22 F0 2E 22 1E 04 23 00 00 00 20 23 2C 23 23 30 2E 30 30 22 F0 2E 22 3B 5B 52 65 64 5D 5C 2D 23 2C 23 23 30 2E 30 30 22 F0 2E 22 1E 04 05 00 00 00 02 30 25 1E 04 08 00 00 00 05 30 2E 30 30 25 1E 04 0B 00 00 00 08 30 2E 30 30 45 2B 30 30 1E 04 0A 00 00 00 07 23 22 20 22 3F 2F 3F 1E 04 09 00 00 00 06 23 22 20 22 3F 3F 1E 04 0D 00 00 00 0A 64 64 2F 6D 6D 2F 79 79 79 79 1E 04 0C 00 00 00 09 64 64 2F 6D 6D 6D 2F 79 79 1E 04 09 00 00 00 06 64 64 2F 6D 6D 6D 1E 04 09 00 00 00 06 6D 6D 6D 2F 79 79 1E 04 0E 00 00 00 0B 68 3A 6D 6D 5C 20 41 4D 2F 50 4D 1E 04 11 00 00 00 0E 68 3A 6D 6D 3A 73 73 5C 20 41 4D 2F 50 4D 1E 04 07 00 00 00 04 68 3A 6D 6D 1E 04 0A 00 00 00 07 68 3A 6D 6D 3A 73 73 1E 04 13 00 00 00 10 64 64 2F 6D 6D 2F 79 79 79 79 5C 20 68 3A 6D 6D 1E 04 0B 00 00 00 08 23 23 30 2E 30 45 2B 30 1E 04 08 00 00 00 05 6D 6D 3A 73 73 1E 04 04 00 00 00 01 40 1E 04 36 00 00 00 33 5F 2D 2A 20 23 2C 23 23 30 22 F0 2E 22 5F 2D 3B 5C 2D 2A 20 23 2C 23 23 30 22 F0 2E 22 5F 2D 3B 5F 2D 2A 20 22 2D 22 22 F0 2E 22 5F 2D 3B 5F 2D 40 5F 2D 1E 04 36 00 00 00 33 5F 2D 2A 20 23 2C 23 23 30 5F F0 5F 2E 5F 2D 3B 5C 2D 2A 20 23 2C 23 23 30 5F F0 5F 2E 5F 2D 3B 5F 2D 2A 20 22 2D 22 5F F0 5F 2E 5F 2D 3B 5F 2D 40 5F 2D 1E 04 3E 00 00 00 3B 5F 2D 2A 20 23 2C 23 23 30 2E 30 30 22 F0 2E 22 5F 2D 3B 5C 2D 2A 20 23 2C 23 23 30 2E 30 30 22 F0 2E 22 5F 2D 3B 5F 2D 2A 20 22 2D 22 3F 3F 22 F0 2E 22 5F 2D 3B 5F 2D 40 5F 2D 1E 04 3E 00 00 00 3B 5F 2D 2A 20 23 2C 23 23 30 2E 30 30 5F F0 5F 2E 5F 2D 3B 5C 2D 2A 20 23 2C 23 23 30 2E 30 30 5F F0 5F 2E 5F 2D 3B 5F 2D 2A 20 22 2D 22 3F 3F 5F F0 5F 2E 5F 2D 3B 5F 2D 40 5F 2D 31 00 14 00 A0 00 00 00 08 00 0D 4D 53 20 53 61 6E 73 20 53 65 72 69 66 31 00 14 00 A0 00 00 00 0E 00 0D 4D 53 20 53 61 6E 73 20 53 65 72 69 66 31 00","AnswerCount":3,"Available Count":1,"Score":0.0665680765,"is_accepted":false,"ViewCount":415,"Q_Id":28632987,"Users Score":1,"Answer":"Use JODConverter.  You have an Excel 4.0 file; too old for Apache POI.","Q_Score":0,"Tags":"java,python,excel,apache-poi,poi-hssf","A_Id":28634898,"CreationDate":"2015-02-20T15:51:00.000","Title":"How to program to save a bunch of \".xls\" files in Excel","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I could use some help.  My python 3.4 Django 1.7.4 site worked fine using sqlite.  Now I've moved it to Heroku which uses Postgres.  And when I try to create a user \/ password i get this error:\n\ncolumn \"is_superuser\" is of type integer but expression is of type boolean\nLINE 1: ...15-02-08 19:23:26.965870+00:00', \"is_superuser\" = false, \"us...\n                                                             ^\nHINT:  You will need to rewrite or cast the expression.\n\nThe last function call in the stack trace is:\n\/app\/.heroku\/python\/lib\/python3.4\/site-packages\/django\/db\/backends\/utils.py in execute\n                return self.cursor.execute(sql, params) ...\n\u25b6 Local vars\n\nI don't have access to the base django code,  just the code on my app.  So any help getting this to work would be really helpful.","AnswerCount":3,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":2600,"Q_Id":28636141,"Users Score":0,"Answer":"It seems to me that you are using raw SQL queries instead of Django ORM calls and this causes portability issues when you switch database engines. I'd strongly suggest to use ORM if it's possible in your case. If not, then I'd say that you need to detect database engine on your own and construct queries depending on current engine.\nIn this case you could try to use 0 instead of false, I guess this should work both on SQLite and Postgres.","Q_Score":0,"Tags":"django,python-3.x,heroku,heroku-postgres","A_Id":28636553,"CreationDate":"2015-02-20T18:50:00.000","Title":"column \"is_superuser\" is of type integer but expression is of type boolean DJANGO Error","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I could use some help.  My python 3.4 Django 1.7.4 site worked fine using sqlite.  Now I've moved it to Heroku which uses Postgres.  And when I try to create a user \/ password i get this error:\n\ncolumn \"is_superuser\" is of type integer but expression is of type boolean\nLINE 1: ...15-02-08 19:23:26.965870+00:00', \"is_superuser\" = false, \"us...\n                                                             ^\nHINT:  You will need to rewrite or cast the expression.\n\nThe last function call in the stack trace is:\n\/app\/.heroku\/python\/lib\/python3.4\/site-packages\/django\/db\/backends\/utils.py in execute\n                return self.cursor.execute(sql, params) ...\n\u25b6 Local vars\n\nI don't have access to the base django code,  just the code on my app.  So any help getting this to work would be really helpful.","AnswerCount":3,"Available Count":2,"Score":-0.0665680765,"is_accepted":false,"ViewCount":2600,"Q_Id":28636141,"Users Score":-1,"Answer":"The problem is caused by a variable trying to change data types (i.e. from a char field to date-time) in the migration files.  A database like PostgreSQL might not know how to change the variable type.\nSo, make sure the variable has the same type in all migrations.","Q_Score":0,"Tags":"django,python-3.x,heroku,heroku-postgres","A_Id":28638965,"CreationDate":"2015-02-20T18:50:00.000","Title":"column \"is_superuser\" is of type integer but expression is of type boolean DJANGO Error","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a large dataset that I do not have direct access to and am trying to convert the data headers into column headings using Python and then returning it back to Excel. \nI have created the function to do this and it works but I have hit a snag. What I want the Excel VBA to do is loop down the range and if the cell's value matches the criteria call the Python function and return the resulting list items in the columns moving across from the original cell.  For example:\nA1 holds the string to format, the functions returns B1, C1, D1, and so on. I can only get this to work if I hard code B1, C1, D1, etc.\nIs there a way to do this via the get_address() range method? I think I can then use the offset() method but am not sure.","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":5808,"Q_Id":28663658,"Users Score":0,"Answer":"Thanks for your help. I've got this to work now and I'm super excited about the future possibilities for Python, xlwings and Excel.\nMy problem was simple once I got the looping through the range sorted (which incidentally was handily imported as each row per element rather than each cell). I had declared my list outside of the function and so was not reset each time the true condition was met. It was getting very frustrating watching my cells fill with the same values time after time. Simple once you know how :)","Q_Score":0,"Tags":"python,excel,python-3.x,xlwings,vba","A_Id":28684225,"CreationDate":"2015-02-22T21:44:00.000","Title":"xlwings output to iterative cell range","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I want to create the tables of one database called \"database1.sqlite\", so I run the command: \n\npython manage.py syncdb\n\nbut when I execute the command I receive the following error:\n\nUnknown command: 'syncdb'\n  Type 'manage.py help' for usage.\n\nBut when I run \n\nmanage.py help \n\nI don`t see any command suspicious to substitute \n\npython manage.py syncdb\n\nVersion of Python I use: 3.4.2    Version of Django I use:1.9 \nI would be very grateful if somebody could help me to solve this issue.\nRegards and thanks in advance","AnswerCount":10,"Available Count":6,"Score":1.0,"is_accepted":false,"ViewCount":73141,"Q_Id":28685931,"Users Score":8,"Answer":"the new django 1.9 has removed \"syncdb\",\nrun \"python manage.py migrate\",\nif you are trying to create a super user, run \"python manage.py createsuperuser\"","Q_Score":32,"Tags":"django,sqlite,python-3.x,django-1.9","A_Id":35020640,"CreationDate":"2015-02-24T00:01:00.000","Title":"\"Unknown command syncdb\" running \"python manage.py syncdb\"","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I want to create the tables of one database called \"database1.sqlite\", so I run the command: \n\npython manage.py syncdb\n\nbut when I execute the command I receive the following error:\n\nUnknown command: 'syncdb'\n  Type 'manage.py help' for usage.\n\nBut when I run \n\nmanage.py help \n\nI don`t see any command suspicious to substitute \n\npython manage.py syncdb\n\nVersion of Python I use: 3.4.2    Version of Django I use:1.9 \nI would be very grateful if somebody could help me to solve this issue.\nRegards and thanks in advance","AnswerCount":10,"Available Count":6,"Score":0.0,"is_accepted":false,"ViewCount":73141,"Q_Id":28685931,"Users Score":0,"Answer":"You can run the command from the project folder as: \"python.exe manage.py migrate\", from a commandline or in a batch-file.\nYou could also downgrade Django to an older version (before 1.9) if you really need syncdb.\nFor people trying to run Syncdb from Visual Studio 2015:\nThe option syncdb was removed from Django 1.9 (deprecated from 1.7), but this option is currently not updated in the context menu of VS2015.\nAlso, in case you didn't get asked to create a superuser you should manually run this command to create one: python.exe manage.py createsuperuser","Q_Score":32,"Tags":"django,sqlite,python-3.x,django-1.9","A_Id":34814438,"CreationDate":"2015-02-24T00:01:00.000","Title":"\"Unknown command syncdb\" running \"python manage.py syncdb\"","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I want to create the tables of one database called \"database1.sqlite\", so I run the command: \n\npython manage.py syncdb\n\nbut when I execute the command I receive the following error:\n\nUnknown command: 'syncdb'\n  Type 'manage.py help' for usage.\n\nBut when I run \n\nmanage.py help \n\nI don`t see any command suspicious to substitute \n\npython manage.py syncdb\n\nVersion of Python I use: 3.4.2    Version of Django I use:1.9 \nI would be very grateful if somebody could help me to solve this issue.\nRegards and thanks in advance","AnswerCount":10,"Available Count":6,"Score":0.0,"is_accepted":false,"ViewCount":73141,"Q_Id":28685931,"Users Score":0,"Answer":"Run the command python manage.py makemigratons,and than python manage.py migrate to sync.","Q_Score":32,"Tags":"django,sqlite,python-3.x,django-1.9","A_Id":36004441,"CreationDate":"2015-02-24T00:01:00.000","Title":"\"Unknown command syncdb\" running \"python manage.py syncdb\"","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I want to create the tables of one database called \"database1.sqlite\", so I run the command: \n\npython manage.py syncdb\n\nbut when I execute the command I receive the following error:\n\nUnknown command: 'syncdb'\n  Type 'manage.py help' for usage.\n\nBut when I run \n\nmanage.py help \n\nI don`t see any command suspicious to substitute \n\npython manage.py syncdb\n\nVersion of Python I use: 3.4.2    Version of Django I use:1.9 \nI would be very grateful if somebody could help me to solve this issue.\nRegards and thanks in advance","AnswerCount":10,"Available Count":6,"Score":0.0199973338,"is_accepted":false,"ViewCount":73141,"Q_Id":28685931,"Users Score":1,"Answer":"Django has removed python manage.py syncdb command now you can simply use python manage.py makemigrations followed bypython manage.py migrate. The database will sync automatically.","Q_Score":32,"Tags":"django,sqlite,python-3.x,django-1.9","A_Id":42688208,"CreationDate":"2015-02-24T00:01:00.000","Title":"\"Unknown command syncdb\" running \"python manage.py syncdb\"","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I want to create the tables of one database called \"database1.sqlite\", so I run the command: \n\npython manage.py syncdb\n\nbut when I execute the command I receive the following error:\n\nUnknown command: 'syncdb'\n  Type 'manage.py help' for usage.\n\nBut when I run \n\nmanage.py help \n\nI don`t see any command suspicious to substitute \n\npython manage.py syncdb\n\nVersion of Python I use: 3.4.2    Version of Django I use:1.9 \nI would be very grateful if somebody could help me to solve this issue.\nRegards and thanks in advance","AnswerCount":10,"Available Count":6,"Score":0.0399786803,"is_accepted":false,"ViewCount":73141,"Q_Id":28685931,"Users Score":2,"Answer":"In Django 1.9 onwards syncdb command is removed. So instead of use that one, you can use migrate command,eg: python manage.py migrate.Then you can run your server by python manage.py runserver command.","Q_Score":32,"Tags":"django,sqlite,python-3.x,django-1.9","A_Id":42795652,"CreationDate":"2015-02-24T00:01:00.000","Title":"\"Unknown command syncdb\" running \"python manage.py syncdb\"","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I want to create the tables of one database called \"database1.sqlite\", so I run the command: \n\npython manage.py syncdb\n\nbut when I execute the command I receive the following error:\n\nUnknown command: 'syncdb'\n  Type 'manage.py help' for usage.\n\nBut when I run \n\nmanage.py help \n\nI don`t see any command suspicious to substitute \n\npython manage.py syncdb\n\nVersion of Python I use: 3.4.2    Version of Django I use:1.9 \nI would be very grateful if somebody could help me to solve this issue.\nRegards and thanks in advance","AnswerCount":10,"Available Count":6,"Score":0.0,"is_accepted":false,"ViewCount":73141,"Q_Id":28685931,"Users Score":0,"Answer":"Alternarte Way:\n\nUninstall Django Module from environment\nEdit Requirements.txt a type Django<1.9\nRun Install from Requirments option in the enviroment\nTry Syncdb again\n\nThis worked for me.","Q_Score":32,"Tags":"django,sqlite,python-3.x,django-1.9","A_Id":43525717,"CreationDate":"2015-02-24T00:01:00.000","Title":"\"Unknown command syncdb\" running \"python manage.py syncdb\"","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a CherryPy Webapp that I originally wrote using file based sessions. From time to time I store potentially large objects in the session, such as the results of running a report - I offer the option to download report results in a variety of formats, and I don't want to re-run the query when the user selects a download due to the potential of getting different data. While using file based sessions, this worked fine.\nNow I am looking at the potential of bringing a second server online, and as such I need to be able to share session data between the servers, for which it would appear that using the memchached session storage type is the most appropriate. I briefly looked at using a PostgreSQL storage type, but this option was VERY poorly documented, and from what I could find, may well be broken. So I implemented the memcached option.\nNow, however, I am running into a problem where, when I try to save certain objects to the session, I get an \"AssertionError: Session data for id xxx not set\". I'm assuming that this is due to the object size exceeding some arbitrary limit set in the CherryPy session backend or memcached, but I don't really know since the exception doesn't tell me WHY it wasn't set. I have increased the object size limit in memcached to the maximum of 128MB to see if that helped, but it didn't - and that's probably not a safe option anyway.\nSo what's my solution here? Is there some way I can use the memcached session storage to store arbitrarily large objects? Do I need to \"roll my own\" DB based or the like solution for these objects? Is the problem potentially NOT size based? Or is there another option I am missing?","AnswerCount":3,"Available Count":2,"Score":0.0665680765,"is_accepted":false,"ViewCount":1009,"Q_Id":28705661,"Users Score":1,"Answer":"Sounds like you want to store a reference to the object stored in Memcache and then pull it back when you need it, rather than relying on the state to handle the loading \/ saving.","Q_Score":2,"Tags":"python,cherrypy","A_Id":28705996,"CreationDate":"2015-02-24T20:30:00.000","Title":"CherryPy Sessions and large objects?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a CherryPy Webapp that I originally wrote using file based sessions. From time to time I store potentially large objects in the session, such as the results of running a report - I offer the option to download report results in a variety of formats, and I don't want to re-run the query when the user selects a download due to the potential of getting different data. While using file based sessions, this worked fine.\nNow I am looking at the potential of bringing a second server online, and as such I need to be able to share session data between the servers, for which it would appear that using the memchached session storage type is the most appropriate. I briefly looked at using a PostgreSQL storage type, but this option was VERY poorly documented, and from what I could find, may well be broken. So I implemented the memcached option.\nNow, however, I am running into a problem where, when I try to save certain objects to the session, I get an \"AssertionError: Session data for id xxx not set\". I'm assuming that this is due to the object size exceeding some arbitrary limit set in the CherryPy session backend or memcached, but I don't really know since the exception doesn't tell me WHY it wasn't set. I have increased the object size limit in memcached to the maximum of 128MB to see if that helped, but it didn't - and that's probably not a safe option anyway.\nSo what's my solution here? Is there some way I can use the memcached session storage to store arbitrarily large objects? Do I need to \"roll my own\" DB based or the like solution for these objects? Is the problem potentially NOT size based? Or is there another option I am missing?","AnswerCount":3,"Available Count":2,"Score":0.0665680765,"is_accepted":false,"ViewCount":1009,"Q_Id":28705661,"Users Score":1,"Answer":"From what you have explained I can conclude that conceptually it isn't a good idea to mix user sessions and a cache. What sessions are mostly designed for is holding state of user identity. Thus it has security measures, locking, to avoid concurrent changes, and other aspects. Also a session storage is usually volatile. Thus if you mean to use sessions as a cache you should understand how sessions really work and the consequences are.\nWhat I suggest you to do it to establish normal caching of your domain model that produces report data and keep session for identity.\nCherryPy details\nDefault CherryPy session implementation locks the session data. In the OLAP case your user likely won't be able to perform concurrent requests (open another tab for instance) until the report is completed. There's however an option of manual locking management.\nPostgreSQL session storage is broken and may be removed in next releases.\nMemcached session storage doesn't implement distributed locking, so make sure you use consistent rule to balance your user across your servers.","Q_Score":2,"Tags":"python,cherrypy","A_Id":28717896,"CreationDate":"2015-02-24T20:30:00.000","Title":"CherryPy Sessions and large objects?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm making queries from a MS SQL server using Python code (Pymssql library) however I was wondering if there was any way to make the connection secure and encrypt the data being sent from the server to python? \nThanks","AnswerCount":4,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":6365,"Q_Id":28724427,"Users Score":0,"Answer":"If you want to connect SQL server using secured connection using pymssql then you need to provide \"secure\" syntax in your host.. \nfor e.g.\nunsecured connection host : xxx.database.windows.net:1433\nsecured connection host : xxx.database.secure.windows.net:1443","Q_Score":4,"Tags":"python,sql-server,pymssql","A_Id":38181077,"CreationDate":"2015-02-25T16:32:00.000","Title":"Can Pymssql have a secure connection (SSL) to MS SQL Server?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Python application, standard web app.\nIf a particular request gets executed twice by error the second request will try to insert a row with an already existing primary key.  \nWhat is the most sensible way to deal with it.\na) Execute a query to check if the primary key already exists and do the checking and error handling in the python app\nb) Let the SQL engine reject the insertion with a constraint failure and use exception handling to handle it back in the app\nFrom a speed perspective it might seem that a failed request will take the same amount of time as a successful one, making b faster because its only one request and not two.\nHowever, when you take things in account like read-only db slaves and table write-locks and stuff like that things get fuzzy for my experience on scaling standard SQL databases.","AnswerCount":2,"Available Count":2,"Score":0.0996679946,"is_accepted":false,"ViewCount":61,"Q_Id":28787814,"Users Score":1,"Answer":"The latter one you need to do and handle in any case, thus I do not see there is much value in querying for duplicates, except to show the user information beforehand - e.g. report \"This username has been taken already, please choose another\" when the user is still filling in the form.","Q_Score":1,"Tags":"python,mysql,sql","A_Id":28787981,"CreationDate":"2015-02-28T22:40:00.000","Title":"Let the SQL engine do the constraint check or execute a query to check the constraint beforehand","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Python application, standard web app.\nIf a particular request gets executed twice by error the second request will try to insert a row with an already existing primary key.  \nWhat is the most sensible way to deal with it.\na) Execute a query to check if the primary key already exists and do the checking and error handling in the python app\nb) Let the SQL engine reject the insertion with a constraint failure and use exception handling to handle it back in the app\nFrom a speed perspective it might seem that a failed request will take the same amount of time as a successful one, making b faster because its only one request and not two.\nHowever, when you take things in account like read-only db slaves and table write-locks and stuff like that things get fuzzy for my experience on scaling standard SQL databases.","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":61,"Q_Id":28787814,"Users Score":2,"Answer":"The best option is (b), from almost any perspective.  As mentioned in a comment, there is a multi-threading issue.  That means that option (a) doesn't even protect data integrity.  And that is a primary reason why you want data integrity checks inside the database, not outside it.\nThere are other reasons.  Consider performance.  Passing data into and out of the database takes effort.  There are multiple levels of protocol and data preparation, not to mention round trip, sequential communication from the database server.  One call has one such unit of overhead.  Two calls have two such units.\nIt is true that under some circumstances, a failed query can have a long clean-up period.  However, constraint checking for unique values is a single lookup in an index, which is both fast and has minimal overhead for cleaning up.  The extra overhead for handling the error should be tiny in comparison to the overhead for running the queries from the application -- both are small, one is much smaller.\nIf you had a query load where the inserts were really rare with respect to the comparison, then you might consider doing the check in the application.  It is probably a tiny bit faster to check to see if something exists using a SELECT  rather than using INSERT.  However, unless your query load is many such checks for each actual insert, I would go with checking in the database and move on to other issues.","Q_Score":1,"Tags":"python,mysql,sql","A_Id":28788000,"CreationDate":"2015-02-28T22:40:00.000","Title":"Let the SQL engine do the constraint check or execute a query to check the constraint beforehand","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Are null bytes allowed in unicode strings?\nI don't ask about utf8, I mean the high level object representation of a unicode string.\nBackground\nWe store unicode strings containing null bytes via Python in PostgreSQL.\nThe strings cut at the null byte if we read it again.","AnswerCount":3,"Available Count":2,"Score":-0.1325487884,"is_accepted":false,"ViewCount":8634,"Q_Id":28813409,"Users Score":-2,"Answer":"Since a string is basically just data and a pointer, you can save null in it. However, since null represents the end of the string (\"null terminator \"), there is no way to read beyond the null without knowing the size ahead of reading. \nTherefore, seems that you ought to store your data in binary and read it as a buffer.\nGood luck!","Q_Score":5,"Tags":"python,postgresql,unicode","A_Id":28813836,"CreationDate":"2015-03-02T15:27:00.000","Title":"Are null bytes allowed in unicode strings in PostgreSQL via Python?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Are null bytes allowed in unicode strings?\nI don't ask about utf8, I mean the high level object representation of a unicode string.\nBackground\nWe store unicode strings containing null bytes via Python in PostgreSQL.\nThe strings cut at the null byte if we read it again.","AnswerCount":3,"Available Count":2,"Score":0.0665680765,"is_accepted":false,"ViewCount":8634,"Q_Id":28813409,"Users Score":1,"Answer":"Python itself is perfectly capable of having both byte strings and Unicode strings with null characters having a value of zero. However if you call out to a library implemented in C, that library may use the C convention of stopping at the first null character.","Q_Score":5,"Tags":"python,postgresql,unicode","A_Id":28814135,"CreationDate":"2015-03-02T15:27:00.000","Title":"Are null bytes allowed in unicode strings in PostgreSQL via Python?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"For a project I have to use DynamoDB(aws) and python(with boto).\nI have items with a date and I need to display the count grouped by date or by month.\nSomething like\nby date of the month [1\/2: 5, 2\/2: 10, 3\/2: 7, 4\/2: 30, 5\/2: 25, ...]\nor \nby month of the year [January: 5, February: 10, March: 7, ...]","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":3106,"Q_Id":28818394,"Users Score":2,"Answer":"You can create 2 GSIs: 1 with date as hashKey, 1 with month as hashKey.\nThose GSIs will point you to the rows of that month \/ of that day.\nThen you can just query the GSI, get all the rows of that month\/day, and do the aggregation on your own. \nDoes that work for you?\nThanks!\nErben","Q_Score":0,"Tags":"python,amazon-web-services,amazon-dynamodb,boto","A_Id":28890074,"CreationDate":"2015-03-02T19:56:00.000","Title":"Using group by in DynamoDB","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Is it possible to write nice-formatted excel files with dataframe.to_excel-xlsxwriter combo?\nI am aware that it is possible to format cells when writing with pure xlsxwriter. But dataframe.to_excel takes so much less space.\nI would like to adjust cell width and add some colors to column names.\nWhat other alternatives would you suggest?","AnswerCount":1,"Available Count":1,"Score":0.3799489623,"is_accepted":false,"ViewCount":100,"Q_Id":28839976,"Users Score":2,"Answer":"I found xlwings. It's intuitive and does all the things I want to do. Also, it does well with all pandas data types.","Q_Score":1,"Tags":"python,pandas,xlsxwriter","A_Id":28862593,"CreationDate":"2015-03-03T19:10:00.000","Title":"How to do formmating with combination of pandas dataframe.to_excel and xlsxwriter?","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Is it possible to add or remove entries to an excel file or a text file while it is still open (viewing live update of values from python output) instead of seeing the output in terminal?","AnswerCount":1,"Available Count":1,"Score":0.537049567,"is_accepted":false,"ViewCount":2289,"Q_Id":28879391,"Users Score":3,"Answer":"It depends on the application you are using to view the file. You will have to check the features available in the tools you are using.\nFor instance, in Excel, this is impossible. When you open an Excel document, it actually creates an invisible copy. You are not editing the original. It is only when the file is saved that the original is updated. So, if you have a file my_excel_file.xlsx, when you open it, another file is created named ~$my_excel_file.xlsx. So, editing the original file will not update the file being viewed in the Excel application.\nFor text files, on the other hand, there are some applications that will reload changes from disk. Sublime Text is an example of this. If you have a file open in Sublime Text, then make a change to the file with another program, Sublime Text will automatically reload the new version when the application regains focus.","Q_Score":2,"Tags":"python,excel,xlsx","A_Id":28879986,"CreationDate":"2015-03-05T13:50:00.000","Title":"Editing an open document with python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I've written some code that iterates through a flat file. After a certain section is completed reading, I take the data and put it into a spreadsheet. Then, I go back and continue reading the flat file for the next section and write to a new worksheet...and so on and so forth.\nWhen looping through the python code, I create a new worksheet for each section read above. During this looping, I create the new worksheet as such:\nworksheet = workbook.add_worksheet(thename)\nThe problem is that the second time through the loop, python crashes when re-assigning the worksheet object above to a new worksheet. Is there a way to \"close the worksheet object\", then re-assign it?\nFYI: If I can't use the same object name, \"worksheet\" in this case, the code is going to become tremendously long and messy in order to handle \"worksheet1\", \"worksheet2\", \"worksheet3\", etc... (as you might imagine)\nThank you in advance!","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1050,"Q_Id":28909360,"Users Score":0,"Answer":"Instead of assigning the variable worksheet to workbook.add_worksheet(thename), have a list called worksheets. When you normally do worksheet = workbook.add_worksheet(thename), do worksheets.append(workbook.add_worksheet(thename)). Then access your latest worksheet with worksheets[-1].","Q_Score":1,"Tags":"python,xlsxwriter","A_Id":28909616,"CreationDate":"2015-03-06T23:26:00.000","Title":"python xlsxwriter worksheet object reuse","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"after I put the photologue on the server, I have no issue with uploading photos.\nthe issue is when I am creating a Gallery from the admin site, I can choose only one photo to be attached to the Gallery. even if I selected many photos, one of them will be linked to the Gallery only.\nThe only way to add photos to a gallery is by adding them manually to photologue_gallery_photos table in the database :(\nanyone kows how to solve it?","AnswerCount":3,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":184,"Q_Id":28927247,"Users Score":0,"Answer":"I had exactly the same problem. I suspected some problem with django-sortedm2m package.  To associate photo to gallery, it was using SortedManyToMany() from sortedm2m package. For some reason, the admin widget associated with this package did not function well. (I tried Firefox, Chrome and safari browser). \nI actually did not care for the order of photos getting uploaded to Gallery, so I simply replaced that function call with Django's ManyToManyField(). Also, I noticed that SortedManyToMany('Photo') was called with constant string Photo. Instead it should be called with SortedManyToMany(Photo) to identify Photo class. Although it did not resolve my problem entirely. So I used default ManyToMany field and it is showing all the photos from Gallery.","Q_Score":0,"Tags":"python,django,python-3.4,django-1.7,photologue","A_Id":31394483,"CreationDate":"2015-03-08T13:57:00.000","Title":"Gallery in Photologue can have only one Photo","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"after I put the photologue on the server, I have no issue with uploading photos.\nthe issue is when I am creating a Gallery from the admin site, I can choose only one photo to be attached to the Gallery. even if I selected many photos, one of them will be linked to the Gallery only.\nThe only way to add photos to a gallery is by adding them manually to photologue_gallery_photos table in the database :(\nanyone kows how to solve it?","AnswerCount":3,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":184,"Q_Id":28927247,"Users Score":0,"Answer":"I guess your problem is solved by now, but just in case.. I had the same problem. Looking around in the logs, I found it was caused by me not having consolidated the static files from sortedm2m with the rest of my static files (hence the widget was not working properly).","Q_Score":0,"Tags":"python,django,python-3.4,django-1.7,photologue","A_Id":32932624,"CreationDate":"2015-03-08T13:57:00.000","Title":"Gallery in Photologue can have only one Photo","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have the following TimeStamp value: Wed Jun 25 09:18:15 +0000 2014.\nI am writing a MapReduce program in Python that reads JSON objects from an Amazon S3 location and export it to a local CSV file. The CSV file will then export data to a MySQL and HBase database. I have about 200 million records (1 TB), so I need to optimize every processing step.\nWhat data type should I use to store the TimeStamp value in Python, CSV, MySQL and HBase database? I need to store all aspects of the TimeStamp value. My schema has 4 columns in the CSV file, MySQL and HBase database tables.\nThanks!","AnswerCount":1,"Available Count":1,"Score":0.3799489623,"is_accepted":false,"ViewCount":444,"Q_Id":28961577,"Users Score":2,"Answer":"Use long to represent time (milli seconds), so you don't bother about the date formatting\/string encoding. It's space efficient and much easier to perform range queries.","Q_Score":1,"Tags":"python,mysql,csv,hbase","A_Id":28963527,"CreationDate":"2015-03-10T10:41:00.000","Title":"Best way to store TimeStamp","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a python script that queries some data from several web APIs and after some processing writes it to MySQL. This process must be repeated every 10 seconds. The data needs to be available to Google Compute instances that read MySQL and perform CPU-intensive work.\nFor this workflow I thought about using GCloud SQL and running GAppEngine to query the data. NOTE: The python script does not run on GAE directly (imports pandas, scipy) but should run on a properly setup App Engine Managed VM.\nFinally the question: is it possible and would it be reasonable to schedule a cron job on a GApp Managed VM to run a command invoking my data collection script every 10 seconds? Any alternatives to this approach?","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1243,"Q_Id":29044322,"Users Score":1,"Answer":"The finest resolution of a cron job is 1 minute, so you cannot run a cron job once every 10 seconds.\nIn your place, I'd run a Python script that starts a new thread every 10 seconds to do your MySQL work, accompanied by a cronjob that runs every minute. If the cronjob finds that the Python script is not running, it would restart it. \n(i.e., the crontab line would look like * * * * *  \/command\/to\/restart\/Python\/script). \nWorse-case scenario you'd miss 5 runnings of your MySQL worker threads (a 50 seconds' duration).","Q_Score":0,"Tags":"python,google-app-engine,cron,virtual-machine,google-compute-engine","A_Id":29050842,"CreationDate":"2015-03-14T01:06:00.000","Title":"Cron job on google cloud managed virtual machine","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I'm new to python and mysql-python module. Is there any way to reuse db connection so that we may not connect() and close() every time a request comes.\nMore generally, how can I keep 'status' on server-side? Can somebody give me a tutorial to follow or guide me somehow, lots of thanks!","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":101,"Q_Id":29064875,"Users Score":0,"Answer":"Really not possible with CGI, the original Common Gateway Interface dictates that the program be run from scratch for each request. \nYou'd want to use WSGI instead (a Python standard), which allows your application be long-lived. WSGI in turn is easiest if you use a Web Framework such as Pyramid, Flask or Django; their integrations with databases like MySQL support connection pooling out of box.","Q_Score":0,"Tags":"python,cgi","A_Id":29064930,"CreationDate":"2015-03-15T19:02:00.000","Title":"How to Reuse Database Connection under Python CGI?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am new to this so a silly question\nI am trying to make a demo website using Django for that I need a database.. Have downloaded and installed MySQL Workbench for the same. But I don't know how to setup this.\nThank you in advance :)\nI tried googling stuff but didn't find any exact solution for the same.\nPlease help","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1235,"Q_Id":29102422,"Users Score":1,"Answer":"I am a mac user. I have luckily overcome the issue with connecting Django to mysql workbench. I assume that you have already installed Django package created your project directory e.g. mysite.\n\nInitially after installation of MySQL workbench i have created a database : create database djo;\nGo to mysite\/settings.py and edit following piece of block.\nNOTE: Keep Engine name \"django.db.backends.mysql\" while using MySQL server. \nand STOP the other Django MySQL service which might be running.\n\nDATABASES = {\n    'default': {\n        'ENGINE': 'django.db.backends.mysql', # Add 'postgresql_psycopg2', 'mysql', 'sqlite3' or 'oracle'.\n        'NAME': 'djo',                      # Or path to database file if using sqlite3.\n        # The following settings are not used with sqlite3:\n        'USER': 'root',\n        'PASSWORD': '****',       # Replace **** with your set password.\n        'HOST': '127.0.0.1',                      # Empty for localhost through domain sockets or '127.0.0.1' for localhost through TCP.\n        'PORT': '3306',                      # Set to empty string for default.\n    }\n}\n\nnow run manage.py to sync your database :\n$ python mysite\/manage.py syncdb\nbash-3.2$ python manage.py syncdb\nCreating tables ...\nCreating table auth_permission\nCreating table auth_group_permissions\nCreating table auth_group\nCreating table auth_user_groups\nCreating table auth_user_user_permissions\nCreating table auth_user\nCreating table django_content_type\nCreating table django_session\nCreating table django_site\n\nYou just installed Django's auth system, which means you don't have any superusers defined.\nWould you like to create one now? (yes\/no): yes\nUsername (leave blank to use 'ambershe'): root\nEmail address: ambershe@netapp.com\n\/Users\/ambershe\/Library\/Containers\/com.bitnami.django\/Data\/app\/python\/lib\/python2.7\/getpass.py:83: GetPassWarning: Can not control echo on the terminal.\n  passwd = fallback_getpass(prompt, stream)\nWarning: Password input may be echoed.\nPassword: ****\nWarning: Password input may be echoed.\nPassword (again): ****\nSuperuser created successfully.\nInstalling custom SQL ...\nInstalling indexes ...\nInstalled 0 object(s) from 0 fixture(s)","Q_Score":0,"Tags":"python,mysql,django,eclipse,pydev","A_Id":29493720,"CreationDate":"2015-03-17T14:56:00.000","Title":"Connect MySQL Workbench with Django in Eclipse in a mac","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have some very peculiar behavior happening when running a data importer using multiprocessor in python.  I believe that this is a database issue, but I am not sure how to track it down.  Below is a description of the process I am doing:\n1)  Multiprocessor file that runs XX number of processors doing parts two and three\n2)  Queue processor that iterates through an sqs queue pulling a company id.  This id is used to pull a json string stored in mysql.  This json string is loaded as a json object and sent to a parsing file that normalizes the data so that it can be imported into mysql as normalized data.\n3)  Company parser\/importer reads through json object and creates inserts into a mysql database, normalizing the data.  These are batch inserted into RDS in batches of XXX size to mitigate IOPS issues.\nThis code is run from a c4.Large instance and works.  When it is started, it works fast (~30,000 inserts per min) without maxing out IOPS, CPU, or other resources on either the RDS or ec2 instance.  Then, after a certain amount of time (5-30min), the RDS server's CPU drops to ~20% and has a weird heartbeat type of rhythm.  I have tried launching additional ec2 instances to speed up this process and the import speed remains unchanged and slow (~2000 inserts per min), so I believe the bottleneck is with the RDS instance.  I tried changing the RDS instance's size from medium to large with no change.  I also tried changing the RDS instance's IOPS to provisioned SSD with 10k.  This also did not fix the problem  \nAs far as I can tell, there is some sort of throttling or limitation by the RDS server.  But, I don't know where else to look.  There are no red flags about what is being limited.\nCan you please provide other potential reasons for why this type of behavior would be happening?  I don't know what else to test.\nCurrent setup is 500gb t2.medium RDS instance with ~200 Write IOPS, CPU at ~20%, Read IOPS < 20, Queue < 1, stable 12 db connections(this is not connecting and then disconnecting), and plenty of free memory.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":260,"Q_Id":29129589,"Users Score":0,"Answer":"I solved this by upping my instance type to a m3.Large instance without limited CPU credits.  Everything works well now.","Q_Score":0,"Tags":"python,mysql,linux,amazon-ec2,rds","A_Id":29169114,"CreationDate":"2015-03-18T18:10:00.000","Title":"Importing data to mysql RDS with python multiprocessor - RDS","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm not sure what exactly the wording for the problem is so if I haven't been able to find any resource telling me how to do this, that's most likely why.\nThe basic problem is that I have a webcrawler, coded in Python, that has a 'Recipe' object that stores certain data about a specific recipe such as 'Name', 'Instructions', 'Ingredients', etc. with 'Instructions' and 'Ingredients' being a string array.\nNow, the problem I have comes when I want to store this data in a database for access from other sources.\nA basic example of the database looks as follows:\n(Recipes)\nr_id, name, ....\n(Ingredients)\ni_id, name, ....\n(RecipeIngredients)\nr_id, i_id.\nNow, specifically my problem is, how do I make sure I'm not duplicating ingredients and how do I insert the data so that the ingredient is linked to the id of the current Recipe object?\nI know my explanation is bad but I'm struggling to put it into words. Any help is appreciated, thanks.","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":45,"Q_Id":29170268,"Users Score":0,"Answer":"For the first question (how do I make sure I'm not duplicating ingredients?), if I understand well, is basically put your primary key as (i_id, name) in the table ingredients. This way you guarantee that is impossible insert an ingredient with the same key (i_id, name).\nNow for the second question (how do I insert the data so that the ingredient is linked to the id of the current Recipe object?). I really don't understand this question very well. What I think you want is link the recipes with ingredients. This can be made with the table RecipeIngredients. When you want to do that, you simple insert a new row in that table with the id of the recipe and the id of the ingredient. If isn't this what you want sorry, but I really don't understand.","Q_Score":0,"Tags":"python,sql","A_Id":29170744,"CreationDate":"2015-03-20T15:33:00.000","Title":"Inserting data into SQL database that needs to be linked","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a MySQLdb installation for Python 2.7.6. I have created a MySQLdb cursor once and would like to reuse the cursor for every incoming request. If 100 users are simultaneously active and doing a db query, does the cursor serve each request one by one and block others?\nIf that is the case, is there way to avoid that? Will having a connection pool will do the job in a threadsafe manner or should I look at Gevent\/monkey patching?\nYour responses are welcome.","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":633,"Q_Id":29196096,"Users Score":1,"Answer":"For this purpose you can use Persistence Connection or Connection Pool.\nPersistence Connection - very very very bad idea. Don't use use it! Just don't! Especially when you are talking about web programming.\nConnection Pool - Better then Persistence Connection, but with no deep understanding of how it works, you will end with the same problems of Persistence Connection.\nDon't do optimization unless you really have performance problems. In web, its common to open\/close connection per page request. It works really fast. You better think about optimizing sql queries, indexes, caches.","Q_Score":0,"Tags":"python,mysql,mysql-python","A_Id":29199028,"CreationDate":"2015-03-22T15:21:00.000","Title":"Is a MySQLdb cursor for Python blocking in nature by default?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"MS SQL Server supports passing a table as a stored-procedure parameter.  Is there any way to utilize this from Python, using PyODBC or pymssql?","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":830,"Q_Id":29371570,"Users Score":0,"Answer":"Use IronPython.  It allows direct access to the .net framework, and therefore you can build a DataTable object and pass it over.","Q_Score":1,"Tags":"python,sql-server,pyodbc","A_Id":29679132,"CreationDate":"2015-03-31T14:49:00.000","Title":"Can you pass table input parameter to SQL Server from Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am using \ndb = MySQLdb.connect(host=\"machine01\", user=local_settings.DB_USERNAME, passwd=local_settings.DB_PASSWORD, db=local_settings.DB_NAME)\nto connect to a DB, but I am doing this from machine02 and I thought this would still work, but it does not. I get\n_mysql_exceptions.OperationalError: (1045, \"Access denied for user 'test_user'@'machine02' (using password: YES)\") \nas a result. However, if I simply ssh over to machine01 and perform the same query, it works just fine. Isn't the point of host to be able to specify where the MySQL db is and be able to query it from any other host instead of having to jump on there to make the query?","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":41,"Q_Id":29372365,"Users Score":0,"Answer":"The error tells you that 'test_user' at machine 'machine02' is not allowed. Probably user 'test_user' is on 'mysql.user' table registered with 'localhost' as connection's host. Check it using a query like this: select host, user from mysql.user;\nBest regards,\nOscar.","Q_Score":0,"Tags":"python,mysql","A_Id":29372847,"CreationDate":"2015-03-31T15:25:00.000","Title":"Query MySQL db from Python returns \"Access Denied\"","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am using \ndb = MySQLdb.connect(host=\"machine01\", user=local_settings.DB_USERNAME, passwd=local_settings.DB_PASSWORD, db=local_settings.DB_NAME)\nto connect to a DB, but I am doing this from machine02 and I thought this would still work, but it does not. I get\n_mysql_exceptions.OperationalError: (1045, \"Access denied for user 'test_user'@'machine02' (using password: YES)\") \nas a result. However, if I simply ssh over to machine01 and perform the same query, it works just fine. Isn't the point of host to be able to specify where the MySQL db is and be able to query it from any other host instead of having to jump on there to make the query?","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":41,"Q_Id":29372365,"Users Score":0,"Answer":"Make sure your firewall isn't blocking port 3306.","Q_Score":0,"Tags":"python,mysql","A_Id":29372390,"CreationDate":"2015-03-31T15:25:00.000","Title":"Query MySQL db from Python returns \"Access Denied\"","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am passing the output from a sql query to again insert the data to ms sql db. If my data is null python \/ pyodbc is returning None instead of NULL. What is the best way to convert None to NULL when I am calling another query using the same data.\nOr a basic string transformation is the only way out ?\nThanks\nShakti","AnswerCount":2,"Available Count":1,"Score":-0.0996679946,"is_accepted":false,"ViewCount":16822,"Q_Id":29431557,"Users Score":-1,"Answer":"You could overwrite query function in way that None will be replace with \"NULL\"","Q_Score":5,"Tags":"python,sql-server,pyodbc","A_Id":29431913,"CreationDate":"2015-04-03T11:43:00.000","Title":"How convert None to NULL with Python 2.7 and pyodbc","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a script to format a bunch of data and then push it into excel, where I can easily scrub the broken data, and do a bit more analysis.\nAs part of this I'm pushing quite a lot of data to excel, and want excel to do some of the legwork, so I'm putting a certain number of formulae into the sheet.\nMost of these (\"=AVERAGE(...)\" \"=A1+3\" etc) work absolutely fine, but when I add the standard deviation (\"=STDEV.P(...)\" I get a name error when I open in excel 2013.\nIf I click in the cell within excel and hit  (i.e. don't change anything within the cell), the cell re-calculates without the name error, so I'm a bit confused.  \nIs there anything extra that needs to be done to get this to work?\nHas anyone else had any experience of this?\nThanks,\nWill\n  --","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":813,"Q_Id":29486671,"Users Score":0,"Answer":"I suspect that there might be a subtle difference in what you think you need to write as the formula and what is actually required. openpyxl itself does nothing with the formula, not even check it. You can investigate this by comparing two files (one from openpyxl, one from Excel) with ostensibly the same formula. The difference might be simple \u2013 using \".\" for decimals and \",\" as a separator between values even if English isn't the language \u2013 or it could be that an additional feature is required: Microsoft has continued to extend the specification over the years.\nOnce you have some pointers please submit a bug report on the openpyxl issue tracker.","Q_Score":3,"Tags":"python,openpyxl","A_Id":29487114,"CreationDate":"2015-04-07T08:01:00.000","Title":"openpyxl and stdev.p name error","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I think InfluxDB is a really cool time series DB.\nI am planning to use it as an intermediate data aggregator (collecting time based metrics from many sensors).\nThe data needs to be processed in \"moving window\" manner - when X samples received, Python based processing algorithm should be triggered.\nWhat is the best wait to trigger the algorithm upon enough data aggregated? (I assume that polling with select queries is not the best option).\nIs there any events I can wait on?\nThanks!\nMeir","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":528,"Q_Id":29528394,"Users Score":1,"Answer":"Not using Python, but in my case i use continuous queries in InfluxDb to consolidate automatically data in one place\/serie. Then i request every X seconds on the newly created serie using a time window to select my data. They are then draw using a standard framework (highcharts.js)\nMaybe in your case you could wait for a predefined data volume before trigerring the push to the processing function.","Q_Score":0,"Tags":"python,time-series,influxdb","A_Id":29533201,"CreationDate":"2015-04-09T01:51:00.000","Title":"How to use InfluxDB as an intermediate data storage","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm writing a web application in python and postgreSQL. Users are to access a lot of information during a session. All such information (almost) are indexed in the database. My question is, should I litter the code with specific queries, or is it better practice to query larger chunks of information, cashing it, and letting python process the chunk for finer pieces? \nFor example: A user is to ask for entries in a payment log. Either one writes a query asking for the specific entries requested, or one collect the payment history of the user and then use python to select the specific entries. \nOf course cashing is preferred when working with heavy queries, but since nearly all my data is indexed, direct database access is fast and the cashing approach would not yield much if any extra speed. But are there other factors that may still render the cashing approach preferable?","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":30,"Q_Id":29538870,"Users Score":1,"Answer":"Database designers spend a lot of time on caching and optimization.  Unless you hit a specific problem, it's probably better to let the database do the database stuff, and your code do the rest instead of having your code try to take over some of the database functionality.","Q_Score":0,"Tags":"python,postgresql","A_Id":29538970,"CreationDate":"2015-04-09T12:44:00.000","Title":"General queries vs detailed queries to database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am using Python to stream large amounts of Twitter data into a MySQL database.  I anticipate my job running over a period of several weeks.  I have code that interacts with the twitter API and gives me an iterator that yields lists, each list corresponding to a database row.  What I need is a means of maintaining a persistent database connection for several weeks.  Right now I find myself having to restart my script repeatedly when my connection is lost, sometimes as a result of MySQL being restarted.\nDoes it make the most sense to use the mysqldb library, catch exceptions and reconnect when necessary?  Or is there an already made solution as part of sqlalchemy or another package?  Any ideas appreciated!","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":48,"Q_Id":29552868,"Users Score":0,"Answer":"I think the right answer is to try and handle the connection errors; it sounds like you'd only be pulling in a much a larger library just for this feature, while trying and catching is probably how it's done, whatever level of the stack it's at. If necessary, you could multithread these things since they're probably IO-bound (i.e. suitable for Python GIL threading as opposed to multiprocessing) and decouple the production and the consumption with a queue, too, which would maybe take some of the load off of the database connection.","Q_Score":0,"Tags":"python,mysql","A_Id":29552956,"CreationDate":"2015-04-10T03:32:00.000","Title":"Persistant MySQL connection in Python for social media harvesting","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm trying to create unit tests for a function that uses database queries in its implementation. My understanding of unit testing is that you shouldn't be using outside resources such as databases for unit testing, and you should just create mock objects essentially hard coding the results of the queries.\nHowever, in this case, the queries are implementation specific, and if the implementation would change, so would the queries. My understanding is also that unit testing is very useful because it essentially allows you to change the implementation of your code whenever you want while being sure it still works.\nIn this case, would it be better to create a database for testing purposes, or to make the testing tailored to this specific implementation and change the test code if we ever change the implementation?","AnswerCount":2,"Available Count":2,"Score":0.0996679946,"is_accepted":false,"ViewCount":105,"Q_Id":29565712,"Users Score":1,"Answer":"As it seems I got the wrong end of the stick, I had a similarish problem and like you an ORM was not an option.\nThe way I addressed it was with simple collections of Data Transfer objects. \nSo the new code I wrote, had no direct access to the db. It did everything with simple lists of objects. All the business logic and ui could be tested without the db.\nThen I had an other module that did nothing but read and write to the db, to and from my collections of objects. It was a poor mans ORM basically, a lot of donkey work. \nTesting was run the db creation script, then some test helper code to populate the db with data I needed for each test.\nBoring but effective, and you can with a bit of care, refactor it in to the code base without too much risk.","Q_Score":1,"Tags":"python,database,unit-testing","A_Id":29576807,"CreationDate":"2015-04-10T15:51:00.000","Title":"Unit testing on implementation-specific database usage","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm trying to create unit tests for a function that uses database queries in its implementation. My understanding of unit testing is that you shouldn't be using outside resources such as databases for unit testing, and you should just create mock objects essentially hard coding the results of the queries.\nHowever, in this case, the queries are implementation specific, and if the implementation would change, so would the queries. My understanding is also that unit testing is very useful because it essentially allows you to change the implementation of your code whenever you want while being sure it still works.\nIn this case, would it be better to create a database for testing purposes, or to make the testing tailored to this specific implementation and change the test code if we ever change the implementation?","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":105,"Q_Id":29565712,"Users Score":2,"Answer":"Well, to start with, I think this is very much something that depends on the application context, the QA\/dev's skill set & preferences.  So, what I think is right may not be right for others.\nHaving said that...\nIn my case, I have a system where an extremely complex ERP database, which I dont control, is very much in the driver's seat and my code is a viewer\/observer, rather than a driver of that database.  I don't, and can't really, use an ORM layer much, all my added value is in queries that deeply understand the underlying database data model.  Note also that I am mostly a viewer of that db, in fact my code has read-only access to the primary db.  It does have write access to its own tagging database which uses the Django ORM and testing there is different in nature because of my reliance on the ORM.\nFor me, it had better be tested with the database.\nMock objects?  Please, mocking would have guzzled time if there is a lot of legitimate reasons to view\/modify database contents with complex queries.  \nChanging queries.  In my case, changing and tweaking those queries, which are the core of my application logic, is very often needed.  So I need to make fully sure that they perform as intended against real data.\nMulti-platform concerns.  I started coding on postgresql, tweaked my connectivity libraries to support Oracle as well.  Ran the unit tests and fixed anything that popped up as an error.  Would a database abstraction have identified things like the LIMIT clause handling in Oracle?\nVersioning.  Again, I am not the master of the database.  So, as versions change, I need to hook up my code to it.  The unit testing is invaluable, but that's because it hits the raw db.\nTest robustness.  One lesson I learned along the way is to uncouple the test from the test db.  Say you want to test a function that flags active customers that have not ordered anything in a year.  My initial test approach involved manual lookups in the test database, find CUST701 to be a match to the condition.  Then call my function and test if CUST701 is the result set of customers needing review.  Wrong approach.  What you want to do is to write, in your test, a query that finds active customers that have not ordered anything in a year.  No hardcoded CUST701s at all, but your test query query can be as hardcoded as you want - in fact, it should look as little as your application queries as possible - you don't want your test sql to replicate what could potentially be a bug in your production code.  Once you have dynamically identified a target customer meeting the criteria, then call your code under test and see if the results are as expected.  Make sure your coverage tools identify when you've been missing test scenarios and plug those holes in the test db.\nBDD.  To a large extent, I am starting to approach testing from a BDD perspective, rather than a low-level TDD.  So, I will be calling the url that handles the inactive customer lists, not testing individual functions.  If the overall result is OK and I have enough coverage, I am OK, without wondering about the detailed low-level to and fro.  So factor this as well in qualifying my answer.\nCoders have always had test databases.  To me, it seems logical to leverage them for BDD\/unit-testing, rather than pretending they don't exist.  But I am at heart a SQL coder that knows Python very well, not a Python expert who happens to dabble in SQL.","Q_Score":1,"Tags":"python,database,unit-testing","A_Id":29566319,"CreationDate":"2015-04-10T15:51:00.000","Title":"Unit testing on implementation-specific database usage","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a command-line tool that I'm creating and I'm looking for a safe place to put my sqlite database so it doesn't get overwritten or deleted by the user by accident in mac,windows,or linux and be accessible by my application.","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":64,"Q_Id":29587822,"Users Score":1,"Answer":"Your tool runs with the permissions of the user.\nAny file created by it can also be delete by the same user.\nYou can ask the administrator to protect your files, but on most Mac\/Windows\/Linux PCs, the user is the administrator.\nThere is no place that is safe from the user that controls your tool's execution environment.\nFor that matter, no software is safe against users with access to the hardware:\n\n\u201cIf you don\u2019t open that exit hatch this moment I shall zap straight off to your major data banks and reprogram you with a very large axe, got that?\u201d\n\n\u2015 Douglas Adams, The Hitchhiker's Guide to the Galaxy","Q_Score":0,"Tags":"python,linux,windows,macos,sqlite","A_Id":29589262,"CreationDate":"2015-04-12T09:15:00.000","Title":"Where to put sqlite database in python command-line project","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a PostgreSQL db. Pandas has a 'to_sql' function to write the records of a dataframe into a database. But I haven't found any documentation on how to update an existing database row using pandas when im finished with the dataframe.\nCurrently I am able to read a database table into a dataframe using pandas read_sql_table. I then work with the data as necessary. However I haven't been able to figure out how to write that dataframe back into the database to update the original rows.\nI dont want to have to overwrite the whole table. I just need to update the rows that were originally selected.","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":11070,"Q_Id":29607222,"Users Score":0,"Answer":"For sql alchemy case of read table as df, change df, then update table values based on df, I found the df.to_sql to work with name=<table_name> index=False if_exists='replace'\nThis should replace the old values in the table with the ones you changed in the df","Q_Score":25,"Tags":"python,postgresql,pandas","A_Id":68004057,"CreationDate":"2015-04-13T14:01:00.000","Title":"Update existing row in database from pandas df","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"In SQLAlchemy, is there a way to store arbitrary metadata in an column object? For example, I want to store a flag on each column that says whether or not that column should be serialized, and then access this information via inspect( Table ).attrs.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":95,"Q_Id":29611273,"Users Score":2,"Answer":"You can pass extra data at the info param in Column initializer Column(...., info={'data': 'data'})","Q_Score":0,"Tags":"python,sqlalchemy","A_Id":29611824,"CreationDate":"2015-04-13T17:21:00.000","Title":"Storing arbitrary metadata in SQLAlchemy column","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I apologize in advance for my lack of knowledge concerning character encoding. \nMy question is: are there any inherent advantages\/disadvantages to using the 'Unicode' type, rather than the 'String' type,  when storing data in PostgreSQL using SQLAlchemy (or vice-versa)? If so, would you mind elaborating?","AnswerCount":1,"Available Count":1,"Score":0.761594156,"is_accepted":false,"ViewCount":3572,"Q_Id":29617210,"Users Score":5,"Answer":"In 99.99% of the cases go for Unicode and if possible use Python 3 as it would make your life easier.","Q_Score":14,"Tags":"python,postgresql,unicode,sqlalchemy,python-2.x","A_Id":35273011,"CreationDate":"2015-04-14T00:27:00.000","Title":"'Unicode' vs. 'String' with SQLAlchemy and PostgreSQL","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am using the openpyxl module for my Python scripts to create and edit .xlsx files directly from the script.\nNow I want to save a not known amount of number on after the other. How can I increase the cell number? So if the last input was made in A4, how can I say that the next should be in A5?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":90,"Q_Id":29642697,"Users Score":0,"Answer":"You can use the .offset() method of a cell to get a cell a particular number of rows or cells away.","Q_Score":0,"Tags":"python,export-to-excel","A_Id":29658155,"CreationDate":"2015-04-15T06:08:00.000","Title":"openpyxl for Python dynamic lines","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am working on a Python\/MySQL cloud app with a fairly complex architecture. Operating this system (currently) generates temporary files (plain text, YAML) and log files and I had intended to store them on the filesystem.\nHowever, our prospective cloud operator only provides a temporary, non-persistent filesystem to apps. This means that the initial approach with storing the temporary and log files won't work.\nThere must be a standard approach to solving this problem which I am not aware of. I don't want to use object storage like S3 because it would extend the current stack and add complexity. But I have the possibility to install an additional, dedicated app (if there is anything made for this purpose) on a different server with the same provider. The only limitation is that it would have to be in PHP, Python, MySQL.\nThe generic question: What is the standard approach to storing files when no persistent filesystem is available?\nAnd for my specific case: Is there any solution using Python and\/or MySQL which is simple and quick to implement? Is this a usecase for Redis?","AnswerCount":3,"Available Count":1,"Score":-0.0665680765,"is_accepted":false,"ViewCount":976,"Q_Id":29656422,"Users Score":-1,"Answer":"Store your logs in MySQL. Just make a table like this:\n\nx***time*****source*****action\n----------------------------\n****unixtime*somemodule*error\/event\n\nYour temporary storage should be enough for temporary files :)","Q_Score":11,"Tags":"python,mysql,redis,cloud,storage","A_Id":29656524,"CreationDate":"2015-04-15T17:04:00.000","Title":"How\/where to store temp files and logs for a cloud app?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":0},{"Question":"I am using py2neo and I would like to extract the information from query returns so that I can do stuff with it in python. For example, I have a DB containing three \"Person\" nodes:\nfor num in graph.cypher.execute(\"MATCH (p:Person) RETURN count(*)\"):\n     print num\noutputs:\n>> count(*)\n3\nSorry for shitty formatting, it looks essentially the same as a mysql output. However, I would like to use the number 3 for computations, but it has type py2neo.cypher.core.Record. How can I convert this to a python int so that I can use it? In a more general sense, how should I go about processing cypher queries so that the data I get back can be used in Python?","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":2448,"Q_Id":29682897,"Users Score":0,"Answer":"can you int(), float() str() on the __str__() method that looks to be outputting the value you want in your example?","Q_Score":2,"Tags":"python,neo4j,type-conversion,py2neo","A_Id":29683003,"CreationDate":"2015-04-16T18:16:00.000","Title":"How to convert neo4j return types to python types","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I need to use some aggregate data in my django application that changes frequently and if I do the calculations on the fly some performance issues may happen. Because of that I need to save the aggregate results in a table and, when data changes, update them. Because I use django some options may be exist and some maybe not. For example I can use django signals and a table that, when post_save signal is emitted, updates the results. Another option is materialized views in postgresql or indexed views in MSSQL Server, that I do not know how to use in django or if django supports them or not. What is the best way to do this in django for improving performance and accuracy of results.","AnswerCount":2,"Available Count":1,"Score":1.0,"is_accepted":false,"ViewCount":6549,"Q_Id":29716972,"Users Score":14,"Answer":"You can use Materialized view with postgres. It's very simple. \n\nYou have to create a view with query like CREATE MATERIALIZED VIEW\nmy_view as select * from my_table;\nCreate a model with two\noption managed=false and db_name=my_view in the model Meta like\nthis\nMyModel(models.Model):\n     class Meta:\n            managed = False\n            db_table='my_view'\nSimply use powers of ORM and treat MyModel as a regular model. e.g. MyModel.objects.count()","Q_Score":13,"Tags":"python,sql-server,django,database,postgresql","A_Id":55397481,"CreationDate":"2015-04-18T11:54:00.000","Title":"using materialized views or alternatives in django","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"The same attributes stored in __dict__ are needed to restore the object, right?","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":100,"Q_Id":29786322,"Users Score":1,"Answer":"I think a SQLAlchemy RowProxy uses _row, a tuple, to store the value.  It doesn't have a __dict__, so no storage overhead of a _dict__ per row.  Its _parent object has fields which store the column names to index pos in tuple lookup.  Pretty common thing to do if you are trying to cut on down sql fetching result sizes - the column list is always the same for each row of the same select, so you rely on a common parent to keep track of which index of the tuple holds which column rather than having your own per-row __dict__.\nAdditional advantage is that, at the db lib connect level, sql cursors return (always?) their values in tuples, so you have little processing overhead.  But a straight sql fetch is just that, a cursor descr & a bunch of disconnected rows with tuples in them - SQLALchemy bridges that and allows to use column names.\nNow, as to how the unpickling process goes, you'd have to look at the actual implementation.","Q_Score":0,"Tags":"python,sqlalchemy","A_Id":29786610,"CreationDate":"2015-04-22T01:50:00.000","Title":"Why is a pickled SQLAlchemy model object smaller than its pickled `__dict__`?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am using simple_salesforce package in python to extract data from SalesForce.\nI have a table that has around 2.8 million records and I am using query_more to extract all data.\nSOQL extracts 1000 rows at a time. How can I increase the batchsize in python to extract maximum number of rows at a time. [I hope maximum number of rows is 2000 at a time]?\nThanks","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":122,"Q_Id":29799993,"Users Score":0,"Answer":"If you truly wish to extract everything, you can use the query_all function.\nquery_all calls the helper function get_all_results which recursively calls query_more until query_more returns \"done\".  The returned result is the full dictionary of all your results.\nThe plus, you get all of your data in a single dictionary.  The rub, you get all 2.8 million records at once.  They may take a while to pull back and, depending on the size of the record, that may be a significant amount of ram.","Q_Score":0,"Tags":"python,salesforce,soql","A_Id":34097734,"CreationDate":"2015-04-22T14:01:00.000","Title":"Increasing Batch size in SOQL","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm currently running into soft memory errors on my Google App Engine app because of high memory usage.  A number of large objects are driving memory usage sky high.  \nI thought perhaps if I set and recalled them from memcache maybe that might reduce overall memory usage.  Reading through the docs this doesn't seem to be the case, and that the benefit of memcache is to reduce HRD queries.\nDoes memcache impact overall memory positively or negatively?\nEdit: I know I can upgrade the instance class to F2 but I'm trying to see if I can remain on the least expensive while reducing memory.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":130,"Q_Id":29806384,"Users Score":3,"Answer":"Moving objects to and from Memcache will have no impact on your memory unless you destroy these objects in your Java code or empty collections.\nA bigger problem is that memcache entities are limited to 1MB, and memcache is not guaranteed. The first of these limitations means that you cannot push very large objects into Memcache.\nThe second limitations means that you cannot easily replace, for example, a HashMap with memcache - it's impossible to tell if getValue() returns null because an object is not present or because it was bumped out of memcache. So you will have to make an extra call each time to a datastore to see if an object is really not present.","Q_Score":0,"Tags":"python-2.7,google-app-engine,memcached","A_Id":29806800,"CreationDate":"2015-04-22T18:48:00.000","Title":"Will using memcache reduce my instance memory?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I'm using cx_Oracle module in python. Do we need to close opened cursors explicitly? What will happen when we miss to close the cursor after fetching data and closing only the connection object (con.close()) without issuing cursor.close()?\nWill there be any chance of memory leak in this situation?","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":4239,"Q_Id":29843170,"Users Score":1,"Answer":"If you use multiple cursor. cursor.close() will help you to release the resources you don't need anymore.\nIf you just use one cursor with one connection. I think connection.close() is fine.","Q_Score":4,"Tags":"python,cx-oracle","A_Id":30171565,"CreationDate":"2015-04-24T09:05:00.000","Title":"cx_Oracle module cursor close in python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm having this weird problem when using\nModel.objects.get(op1=1,op2=2)\nit raises the does not exist error although it exists. Did that ever happen with anyone?\nI even checked in my logs to make sure that the log happened when the id already existed in the database.\n[2015-04-24 20:18:21,106]  ERROR:   Couldn't find the model entry: Traceback (most recent call last):\nDoesNotExist: NpBilling matching query does not exist.\nand in the database, the last modified date for this row specifically is 20:18:19.\nHow could that possible ever happen?! The weird thing is that sometimes it works and sometimes it throws this error.\nI tried to use get_or_create but I end up with 2 entries in the database. one of them is what was already created.\nThanks in advance for your help. I would appreciate fast responses and suggestions.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":57,"Q_Id":29854433,"Users Score":0,"Answer":"I solved it by using transaction.commit() before my second query.","Q_Score":0,"Tags":"python,django,object,get,models","A_Id":29882375,"CreationDate":"2015-04-24T18:00:00.000","Title":"Model.objects.get returns nothing","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have UNIQUE constraint on two columns of a table in SQLite.\nIf I insert a record with a duplicate on these two columns into the table, I will get an exception (sqlite3.IntegrityError).\nIs it possible to retrieve the primary key ID of this record upon such a violation, without doing an additional SELECT?","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1878,"Q_Id":29871461,"Users Score":1,"Answer":"If the primary key is part of the UNIQUE constraint that led to the violation, you already have its value.\nOtherwise, the two columns in the UNIQUE constraint are an alternate key for the table, i.e., they can uniquely identify the conflicting row.\nIf you need the actual primary key, you need to do an additional SELECT.\n(The primary key of the existing row is not part of the exception because it was never looked at during the INSERT attempt.)","Q_Score":1,"Tags":"python,python-3.x,sqlite,unique-constraint","A_Id":29874681,"CreationDate":"2015-04-25T22:31:00.000","Title":"Return existing primary key ID upon constraint failure in sqlite3","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have two repository written in flask and django.\nThese projects sharing the database model which is written in SQLAlchemy in flask and written in Django ORM.\nWhen I write migration script in flask as alembic, How can django project migrates with that script?\nI also think about Django with SQLAlchemy.  But I can't find out Django projects using SQLAlchemy. Is that bad idea?\nThanks.","AnswerCount":2,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":3757,"Q_Id":29890684,"Users Score":2,"Answer":"Firstly, don't do this; you're in for a world of pain. Use an API to pass data between apps.\nBut if you are resigned to doing it, there isn't actually any problem with migrations. Write all of them in one app only, either Django or Alembic and run them there. Since they're sharing a database table, that's all there is to it.","Q_Score":6,"Tags":"python,django,flask,sqlalchemy","A_Id":29890773,"CreationDate":"2015-04-27T08:25:00.000","Title":"How to manage django and flask application sharing one database model?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am using the psycopg2 library with Python3 on a linux server to create some temporary tables on Redshift and querying these tables to get results and write to files on the server.\n\nSince my queries are long and takes about 15 minutes to create all these temp tables that I ultimate pull data from, how do I ensure that my connection persists and I don't lose the temp tables that I later query? Right now I just do a cursor() before the execute(), is there a default timeout for these?\nI have noticed that whenever I do a \n\n\nSelect a,b from #results_table\n\nor \n\nselect * from #results_table\n\nthe query just freezes\/hangs, but \n\nselect top 35 from #results_table\n\nreturns the results (select top 40 fails!). There are about a 100 rows in #results_table, and I am not able to get them all. I did a ps aux and the process just stays in the S+ state. If I manually run the query on Redshift it finishes in seconds.\nAny ideas?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":82,"Q_Id":29893476,"Users Score":1,"Answer":"Re-declaring a cursor doesn't create new connection while using psycopg2.","Q_Score":0,"Tags":"linux,postgresql,python-3.x,psycopg2,amazon-redshift","A_Id":29915754,"CreationDate":"2015-04-27T10:42:00.000","Title":"Does redeclaring a cursor create new connection while using psycopg2?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am using Python's peewee ORM with MYSQL. I want to list the active connections for the PooledDatabase. Is there any way to list..?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":283,"Q_Id":29962386,"Users Score":2,"Answer":"What do you mean \"active\"? Active as in being \"checked out\" by a thread, or active as in \"has a connection to the database\"?\nFor the first, you would just do pooled_db._in_use.\nFor the second, it's a little trickier -- basically it will be the combination of pooled_db._in_use (a dict) and pooled_db._connections (a heap).","Q_Score":1,"Tags":"python-2.7,peewee","A_Id":29968980,"CreationDate":"2015-04-30T08:10:00.000","Title":"Counting Active connections in peewee ORM","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm stumped on this one, please help me oh wise stack exchangers...\nI have a function that uses xlrd to read in an .xls file which is a file that my company puts out every few months.  The file is always in the same format, just with updated data.  I haven't had issues reading in the .xls files in the past but the newest release .xls file is not being read in and is producing this error: *** formula\/tFunc unknown FuncID:186\nThings I've tried:\n\nI compared the new .xls file with the old to see if I could spot any\ndifferences.  None that I could find.\nI deleted all of the macros that were contained in the file (older versions also had macros)\nUpdated xlrd to version 0.9.3 but get the same error\nThese files are originally .xlsm files.  I open them and save them as\n.xls files so that xlrd can read them in.  This worked just fine on previous releases of the file.  After upgrading to xlrd 0.9.3 which supposedly supports .xlsx, I tried saving the .xlsm file as.xlsx and tried to read it in but got an error with a blank error message\n\nUseful Info:\n\nPython 2.7\nxlrd 0.9.3\nWindows 7 (not sure if this matters but...)\n\nMy guess is that there is some sort of formula in the new file that xlrd doesn't know how to read.  Does anybody know what FuncID: 186 is?\nEdit: Still no clue on where to go with this.  Anybody out there run into this?  I tried searching up FuncID 186 to see if it's an excel function but to no avail...","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1917,"Q_Id":29971186,"Users Score":0,"Answer":"I had the same problem and I think we have to look at the cells excel that these are not picking up empty, that's how I solved it.","Q_Score":4,"Tags":"python,windows,excel,python-2.7,xlrd","A_Id":30945220,"CreationDate":"2015-04-30T15:01:00.000","Title":"Python XLRD Error : formula\/tFunc unknown FuncID:186","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I had a duplicate sqlite database. I tried deleting the duplicate but instead deleted both. Is there a way I can generate a new database? The data was not especially important.","AnswerCount":2,"Available Count":1,"Score":0.2913126125,"is_accepted":false,"ViewCount":5560,"Q_Id":29991871,"Users Score":3,"Answer":"When you have no database in your project, a simple python manage.py migrate will create a new db.sqlite3 file.","Q_Score":7,"Tags":"python,django,web","A_Id":66293699,"CreationDate":"2015-05-01T17:30:00.000","Title":"Generating new SQLite database django","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a table that stores tasks submitted by users, with timestamps. I would like to write a query that returns certain rows based on when they were submitted (was it this day\/week\/month..). \nTo check if it was submitted on this week, I wanted to use date.isocalendar()[1] function. The problem is, that my timestamps are datetimes, so I would need to transform those to dates.\nUsing func:\nfilter(func.date(Task.timestamp) == datetime.date(datetime.utcnow()))\nworks properly. \nBut I need the date object's isocalendar() method, so I try\nfilter(func.date(Task.timestamp).isocalendar()[1]==datetime.date(datetime.utcnow()).isocalendar()[1])\nand it's no good, I get AttributeError: Neither 'Function' object nor 'Comparator' object has an attribute 'isocalendar'\nIf I make a simple query and try datetime.date(task.timestamp).isocalendar()[1] it works properly. \nHow do I get it to work in the query's filter?","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1710,"Q_Id":30029827,"Users Score":0,"Answer":"Can you try sqlalchemy.extract(func.date('year', Task.timestamp)) == ... ?","Q_Score":0,"Tags":"python,sqlite,date,datetime,sqlalchemy","A_Id":30030232,"CreationDate":"2015-05-04T12:10:00.000","Title":"SQLAlchemy func issue with date and .isocalendar()","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Os: Mac 10.9\nPython ver: 2.7.9\ndatabase: postgresql 9.3\nI am putting the following command to install psycopg2 in my virtualenv: \nARCHFLAGS=-Wno-error=unused-command-line-argument-hard-error-in-future pip install psycopg2\nI am getting the following error: \nTraceback (most recent call last):\n  File \"\/Users\/dialynsoto\/python_ex\/crmeasy\/venv\/bin\/pip\", line 7, in \n    from pip import main\n  File \"\/Users\/dialynsoto\/python_ex\/crmeasy\/venv\/lib\/python2.7\/site-packages\/pip\/init.py\", line 13, in \n    from pip.utils import get_installed_distributions, get_prog\n  File \"\/Users\/dialynsoto\/python_ex\/crmeasy\/venv\/lib\/python2.7\/site-packages\/pip\/utils\/init.py\", line 18, in \n    from pip.locations import (\n  File \"\/Users\/dialynsoto\/python_ex\/crmeasy\/venv\/lib\/python2.7\/site-packages\/pip\/locations.py\", line 9, in \n    import tempfile\n  File \"\/opt\/local\/Library\/Frameworks\/Python.framework\/Versions\/2.7\/lib\/python2.7\/tempfile.py\", line 35, in \n    from random import Random as _Random\n  File \"\/opt\/local\/Library\/Frameworks\/Python.framework\/Versions\/2.7\/lib\/python2.7\/random.py\", line 49, in \n    import hashlib as _hashlib\n  File \"\/opt\/local\/Library\/Frameworks\/Python.framework\/Versions\/2.7\/lib\/python2.7\/hashlib.py\", line 138, in \n    _hashlib.openssl_md_meth_names)\nAttributeError: 'module' object has no attribute 'openssl_md_meth_names'\nAny clues ?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":213,"Q_Id":30148133,"Users Score":0,"Answer":"Try to find hashlib module within your system. It is likely that you have two modules and the one that is being imported is the wrong one (remove the wrong one if it is the case) or you should simply upgrade your python version.","Q_Score":0,"Tags":"python","A_Id":30148423,"CreationDate":"2015-05-10T05:41:00.000","Title":"psycopg2 error installation in virtualenv","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"cursor.execute(sql_statement)\nconn.close()\nreturn cursor\nthe above are the closing lines of my program. I've 3 html pages (users, workflows, home), returning curosor is triggering data for workflows and  home page, but not for users page\nWhere as, if i do return cursor.fetchall(), then it's working for all 3 pages. \nThe reason why i want to return cursor is, the client might want to iterate or do other processing on the cursor.\nI'm not sure what am doing different with Users page.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":24,"Q_Id":30181471,"Users Score":0,"Answer":"If you close the connection, you cannot iterate a cursor anymore. There is no connection to the database.","Q_Score":0,"Tags":"python-2.7,postgresql-9.3","A_Id":30181819,"CreationDate":"2015-05-12T03:52:00.000","Title":"Returning cursor isn't retrieving data from DB","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a scenario in which I am writing formula for calculating the sum of values of different cells in xlsx. After calculating the sum I write it into different cell. I am doing this in python and for xlsx writing I am using xlsxwriter.\n                 For writing values I am using inmemory option for xlsxwritter and then I am reading it using xlrd by passing in memory string buffer to its constructor but when I am accessing the cell in which sum is written I am getting 0. I understand why this is happening. But is there any way of calculating the sum value in memory. So that when I read it I get the calculated sum using formula.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":505,"Q_Id":30222389,"Users Score":0,"Answer":"But is there any way of calculating the sum value in memory. \n\nNot with XlsxWriter since it doesn't have a calculation engine like Excel.\nHowever, if you only need to do a sum then you could do that in Python.","Q_Score":1,"Tags":"python,xlsx,xlsxwriter","A_Id":30227506,"CreationDate":"2015-05-13T18:15:00.000","Title":"How to trigger calculation of formula in xlsx while writing value cell","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am using sqlalchemy to query memory logs off a MySql database. I am using:\nsession.query(Memory).filter(Memmory.timestamp.between(from_date, to_date))\nbut the results after using the time window are still too many. \nNow I want to query for results withing the time window, but filtered down by asking for entries logged every X minutes\/hours and skipping the ones between, but cannot find a simple way to do it.\nTo further elaborate, lets say the 'l's are all the results from a query in a given timewindow:\nlllllllllllllllllllllllllllllllllllllllllllllllllllllllllllll\nTo dilute them, I am looking for a query that will return only the 'l's every X minutes\/hours so that I am not overwhelmed:\nl......l......l.....l......l......l......l.....l.....l.....l.\nI could get everything and then write a function that does this, but that beats the purpose of avoiding choking with results in the first place.\nSidenote:\nWorse comes to worse, I can ask for a row after skipping a predifined number of rows, using mod on the row id column. But it would be great to avoid that since there is a timestamp (DateTime type of sqlalchemy).\nEdit:\nThere could be some value using group by on timestamp and then somehow selecting a row from every group, but still not sure how to do this in a useful manner with sqlalchemy.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":587,"Q_Id":30234706,"Users Score":0,"Answer":"If I understand correctly your from_date and to_date are just dates. If you set them to python datetime objects with the date\/times you want your results between, it should work.","Q_Score":0,"Tags":"python,mysql,flask,sqlalchemy","A_Id":30238066,"CreationDate":"2015-05-14T10:14:00.000","Title":"How to query rows with a minute\/hour step interval in SqlAlchemy?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I want to create a table(postgres) that stores data about what items were viewed by what user. authenticated users are no problem but how can I tell one anonymous user from another anonymous user? This is needed for analysis purposes.\nmaybe store their IP address as unique ID? How can I do this?","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":4523,"Q_Id":30297785,"Users Score":7,"Answer":"I think you should use cookies.\nWhen a user that is not authenticated makes a request, look for a cookie named whatever (\"nonuserid\" in this case). If the cookie is not present it means it's a new user so you should set the cookie with a random id. If it's present you can use the id in it to identificate the anonymous user.","Q_Score":8,"Tags":"python,django,authentication","A_Id":30298038,"CreationDate":"2015-05-18T07:52:00.000","Title":"how to give some unique id to each anonymous user in django","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a 3+ million record XLS file which i need to dump in Oracle 12C DB (direct dump) using a python 2.7.\nI am using Cx_Oracle python package to establish connectivity to Oracle , but reading and dumping the XLS (using openpyxl pckg) is extremely slow and performance degrades for thousands\/million records.\nFrom a scripting stand point used two ways-\n\nI've tried bulk load , by reading all the values in array and then dumping it using cursor prepare (with bind variables) and cursor fetchmany.This doesn't work well with huge data.\nIterative loading of the data as it is being fetched.Even this way has performance issues.\n\nWhat options and techniques\/packages can i deploy as a best practise to load this volume of data from XLS to Oracle DB ?Is it advisable to load this volume of data via scripting or should i necessarily use an ETL tool ?\nAs of now i only have option via python scripting so please do answer the former","AnswerCount":5,"Available Count":3,"Score":1.2,"is_accepted":true,"ViewCount":4256,"Q_Id":30324370,"Users Score":2,"Answer":"If is possible to export your excel fila as a CSV, then all you need is to use sqlldr to load the file in db","Q_Score":4,"Tags":"python,oracle,cx-oracle","A_Id":30324469,"CreationDate":"2015-05-19T11:29:00.000","Title":"loading huge XLS data into Oracle using python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a 3+ million record XLS file which i need to dump in Oracle 12C DB (direct dump) using a python 2.7.\nI am using Cx_Oracle python package to establish connectivity to Oracle , but reading and dumping the XLS (using openpyxl pckg) is extremely slow and performance degrades for thousands\/million records.\nFrom a scripting stand point used two ways-\n\nI've tried bulk load , by reading all the values in array and then dumping it using cursor prepare (with bind variables) and cursor fetchmany.This doesn't work well with huge data.\nIterative loading of the data as it is being fetched.Even this way has performance issues.\n\nWhat options and techniques\/packages can i deploy as a best practise to load this volume of data from XLS to Oracle DB ?Is it advisable to load this volume of data via scripting or should i necessarily use an ETL tool ?\nAs of now i only have option via python scripting so please do answer the former","AnswerCount":5,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":4256,"Q_Id":30324370,"Users Score":0,"Answer":"Excel also comes with ODBC support so you could pump straight from Excel to Oracle assuming you have the drivers. That said, anything that involves transforming a large amount of data in memory (from whatever Excel is using internally) and then passing it to the DB is likely to be less performant than a specialised bulk operation which can be optimised to use less memory. Going through Python just adds another layer to the task (Excel to Python to Oracle), though it might be possible to set this up to use streams.","Q_Score":4,"Tags":"python,oracle,cx-oracle","A_Id":30328198,"CreationDate":"2015-05-19T11:29:00.000","Title":"loading huge XLS data into Oracle using python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a 3+ million record XLS file which i need to dump in Oracle 12C DB (direct dump) using a python 2.7.\nI am using Cx_Oracle python package to establish connectivity to Oracle , but reading and dumping the XLS (using openpyxl pckg) is extremely slow and performance degrades for thousands\/million records.\nFrom a scripting stand point used two ways-\n\nI've tried bulk load , by reading all the values in array and then dumping it using cursor prepare (with bind variables) and cursor fetchmany.This doesn't work well with huge data.\nIterative loading of the data as it is being fetched.Even this way has performance issues.\n\nWhat options and techniques\/packages can i deploy as a best practise to load this volume of data from XLS to Oracle DB ?Is it advisable to load this volume of data via scripting or should i necessarily use an ETL tool ?\nAs of now i only have option via python scripting so please do answer the former","AnswerCount":5,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":4256,"Q_Id":30324370,"Users Score":0,"Answer":"Automate the export of XLSX to CSV as mentioned in a previous answer.  But, instead of then calling a sqlldr script, create an external table that uses your sqlldr code.  It will load your table from the CSV each time the table is selected from.","Q_Score":4,"Tags":"python,oracle,cx-oracle","A_Id":63836641,"CreationDate":"2015-05-19T11:29:00.000","Title":"loading huge XLS data into Oracle using python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Sorry for the rookie question. I have a sqlite file and I need to get table column names. How can I get them?","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":696,"Q_Id":30329528,"Users Score":2,"Answer":"use the pragma table_info(spamtable) command.  The table names will be index 1 of the returned tuples.","Q_Score":1,"Tags":"python,database,sqlite","A_Id":30329701,"CreationDate":"2015-05-19T15:12:00.000","Title":"How to get list of column names of a sqlite db file","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am using GoogleScraper for some automated searches in python.\nGoogleScraper keeps search results for search queries in its database named google_scraper.db.e.g. if i have searched site:*.us engineering books and due to internet issue while making json file by GoogleScraper.If the result is missed and json file is not like that what it must be then when i again search that command using GoogleScraper it gives same result while internet is working fine,i mean to say GoogleScraper maintains its database for a query which it has searched and does not search again it, when i search that command whose result is stored in database,it does not give new result but give results from database stored previously","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":192,"Q_Id":30347571,"Users Score":0,"Answer":"I solved the issue which keeps searches in GoogleScraper database,we first have to run following command\nGoogleScraper --clean\nThis command cleans all cache and we can search again with new results.\n\nRegards!","Q_Score":0,"Tags":"python,bash,web-scraping","A_Id":30433834,"CreationDate":"2015-05-20T10:54:00.000","Title":"GoogleScraper keeps searches in database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":1,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"How to do syncdb in django 1.4.2?\ni.e. having data in database, how to load the models again when the data schema is updated?\nThanks in advance","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":2775,"Q_Id":30387974,"Users Score":3,"Answer":"Thanks Amyth for the hints. \nbtw the commands is a bit different, i will post a 10x tested result here.\nUsing south \n1. setup the model\npython manage.py schemamigration models --initial\n\ndump data if you have to\n\npython manage.py dumpdata -e contenttypes -e auth.Permission --natural > data.json\n\nsyncdb \n\npython manage.py syncdb\npython manage.py migrate models\n\nload the data back into the db \n\npython manage.py loaddata data.json\n\nAfterwards, you may use \n\npython manage.py schemamigration models --auto\npython manage.py migrate models\nafter every change you made in the models schema\n\nA few notes \n1. Unloading the database and reload it is essential, because if not doing so the first migration will tell you already have those models. \n2. The -e contenttypes -e auth.Permission --natural parameter in dumpdata is essential otherwise exception will be thrown when doing loaddata.","Q_Score":1,"Tags":"python,django,django-models,django-syncdb","A_Id":30392918,"CreationDate":"2015-05-22T03:38:00.000","Title":"How to do django syncdb in version 1.4.2?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I could create tables using the command alembic revision -m 'table_name' and then defining the versions and migrate using alembic upgrade head.\nAlso,  I could create tables in a database by defining a class in models.py (SQLAlchemy).\nWhat is the difference between the two? I'm very confused. Have I messed up the concept?\nAlso, when I migrate the database using Alembic, why doesn't it form a new class in my models.py? I know the tables have been created because I checked them using a SQLite browser.\nI have done all the configurations already. The target for Alembic's database and SQLALCHEMY_DATABASE-URI in config.py are the same .db file.","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":10088,"Q_Id":30425214,"Users Score":52,"Answer":"Yes, you are thinking about it in the wrong way.\nLet's say you don't use Alembic or any other migration framework. In that case you create a new database for your application with the following steps:\n\nWrite your model classes\nCreate and configure a brand new database\nRun db.create_all(), which looks at your models and creates the corresponding tables in your database.\n\nSo now consider the case of an upgrade. For example, let's say you release version 1.0 of your application and now start working on version 2.0, which requires some changes to your database. How can you achieve that? The limitation here is that db.create_all() does not modify tables, it can only create them from scratch. So it goes like this:\n\nMake the necessary changes to your model classes\nNow you have two options to transfer those changes to the database:\n5.1 Destroy the database so that you can run db.create_all() again to get the updated tables, maybe backing up and restoring the data so that you don't lose it. Unfortunately SQLAlchemy does not help with the data, you'll have to use database tools for that.\n5.2 Apply the changes manually, directly to the database. This is error prone, and it would be tedious if the change set is large.\n\nNow consider that you have development and production databases, that means the work needs to be done twice. Also think about how tedious would it be when you have several releases of your application, each with a different database schema and you need to investigate a bug in one of the older releases, for which you need to recreate the database as it was in that release.\nSee what the problem is when you don't have a migration network?\nUsing Alembic, you have a little bit of extra work when you start, but it pays off because it simplifies your workflow for your upgrades. The creation phase goes like this:\n\nWrite your model classes\nCreate and configure a brand new database\nGenerate an initial Alembic migration, either manually or automatically. If you go with automatic migrations, Alembic looks at your models and generates the code that applies those to the database.\nRun the upgrade command, which runs the migration script, effectively creating the tables in your database.\n\nThen when you reach the point of doing an upgrade, you do the following:\n\nMake the necessary changes to your model classes\nGenerate another Alembic migration. If you let Alembic generate this for you, then it compares your models classes against the current schema in your database, and generates the code necessary to make the database match the models.\nRun the upgrade command. This applies the changes to the database, without the need to destroy any tables or back up data. You can run this upgrade on all your databases (production, development, etc.).\n\nImportant things to consider when using Alembic:\n\nThe migration scripts become part of your source code, so they need to be committed to source control along with your own files.\nIf you use the automatic migration generation, you always have to review the generated migrations. Alembic is not always able to determine the exact changes, so it is possible that the generated script needs some manual fine tuning.\nMigration scripts have upgrade and downgrade functions. That means that they not only simplify upgrades, but also downgrades. If you need to sync the database to an old release, the downgrade command does it for you without any additional work on your part!","Q_Score":19,"Tags":"python,flask,sqlalchemy,alembic","A_Id":30425438,"CreationDate":"2015-05-24T15:30:00.000","Title":"What is the difference between creating db tables using alembic and defining models in SQLAlchemy?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"My problem is rather simple : I have an Excel Sheet that does calculations and creates a graph based on the values of two cells in the sheet. I also have two lists of inputs in text files. I would like to loop through those text files, add the values to the excel sheet, refresh the sheet, and print the resulting graph to a pdf file or an excel file named something like 'input1 - input2.xlsx'.\nMy programming knowledge is limited, I am decent with Python and have looked into python libraries that work with excel such as openpyxl, however most of those don't seem to work for me for various reasons. Openpyxl deletes the graphs when opening an excel file; XlsxWriter can only write files, not read from them; and xlwings won't work for me.\nShould I use python, which I'm familiar with, or would VBA work for this kind of problem? Have any of you ever done something of the sort?\nThanks in advance","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":226,"Q_Id":30436329,"Users Score":1,"Answer":"I think you should consider win32Com for excel operation in python instead of Openpyxl,XlsxWriter.\nyou can read\/write excel, create chart and format excel file using win32com without any limitation.\nAnd creating chart you can consider matplotlib, in that after creating chart you can save it in pdf file also.","Q_Score":1,"Tags":"python,excel","A_Id":30436742,"CreationDate":"2015-05-25T10:34:00.000","Title":"Automatic input from text file in excel","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a large A.csv file (~5 Gb) with several columns. One of the columns is Model.\nThere is another large B.csv file (~15 Gb) with Vendor, Name and Model columns.\nTwo questions:\n1) How can I create result file that combines all columns from A.csv and corresponding Vendor and Name from B.csv (join on Model). The trick is - how to do it when my RAM is 4 Gb only, and I'm using python.\n2) How can I create a sample (say, 1 Gb) result file that combines random subsample from A.csv (all columns) joined with Vendor and Name from B.csv. The trick is, again, in 4 Gb of RAM.\nI know how to do it in pandas, but 4 Gb is limiting factor I can't overcome (","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":862,"Q_Id":30441107,"Users Score":0,"Answer":"As @Marc B said, reading one row at a time is the solution.\nAbout the join I would do the following (pseudocode: I don't know python).\n\n\"Select distinct Model from A\" on first file A.csv\n\nRead all rows, search for Model field and collect distinct values in a list\/array\/map\n\n\"Select distinct Model from B\" on second file B.csv\n\nSame operation as 1, but using another list\/array\/map\n\nFind matching models\n\nCompare the two lists\/arrays\/maps finding only matching models (they will be part of the join)\n\nDo the join\n\nReading rows of file A which match model, read all the rows of file B which match same model and write a file C with join result. To this for all models.\nNote: it's not particularly optimized.\nFor point 2 just choose a subset of matching models and\/or read a part of rows of file A and\/or B with maching models.","Q_Score":0,"Tags":"python,file,memory,merge","A_Id":30441330,"CreationDate":"2015-05-25T14:57:00.000","Title":"Concatenate large files in sql-like way with limited RAM","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm trying to istall mysql server on a windows 7 machine - that has python 3.4.3 installed. However, when trying to install the python connectors for 3.4, the installer fails to recognize the python installation, saying python 3.4 is not installed. \nHas anyone solved this issue before? I'ts driving me nuts...","AnswerCount":12,"Available Count":7,"Score":1.0,"is_accepted":false,"ViewCount":35704,"Q_Id":30467495,"Users Score":13,"Answer":"Just to add to the murkiness, I had the same error with current version of MySql install when attempting with python 3.5 installed (which is the latest python download).  Long story short, I uninstalled python 3.5, installed python 3.4.4 (which interestingly didn't update PATH so I updated it manually) and reran installer and it found the python installation.\nSo my conclusion is the MySql installer is tied to certain versions of the add-on products which in this case meant specifically python 3.4","Q_Score":26,"Tags":"mysql,python-3.x,installation","A_Id":39704698,"CreationDate":"2015-05-26T19:42:00.000","Title":"mysql installer fails to recognize python 3.4","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm trying to istall mysql server on a windows 7 machine - that has python 3.4.3 installed. However, when trying to install the python connectors for 3.4, the installer fails to recognize the python installation, saying python 3.4 is not installed. \nHas anyone solved this issue before? I'ts driving me nuts...","AnswerCount":12,"Available Count":7,"Score":1.0,"is_accepted":false,"ViewCount":35704,"Q_Id":30467495,"Users Score":10,"Answer":"just in case anyone else has this issue in future. Look at what bit version you have for Python 3.4. When I installed 64 bit version of Python 3.4, this issue went away.","Q_Score":26,"Tags":"mysql,python-3.x,installation","A_Id":35611377,"CreationDate":"2015-05-26T19:42:00.000","Title":"mysql installer fails to recognize python 3.4","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm trying to istall mysql server on a windows 7 machine - that has python 3.4.3 installed. However, when trying to install the python connectors for 3.4, the installer fails to recognize the python installation, saying python 3.4 is not installed. \nHas anyone solved this issue before? I'ts driving me nuts...","AnswerCount":12,"Available Count":7,"Score":1.0,"is_accepted":false,"ViewCount":35704,"Q_Id":30467495,"Users Score":8,"Answer":"I ran into a similar issue with Python 3.7.2.\nIn my case, the problem was that I tried to install the 64 bit MySQL connector, but had the 32 bit version of Python installed on my machine.\nI got a similar error message:\n\nPython v3.7 not found. We only support Python installed using the Microsoft Windows Installer (MSI) [...]\n\nThe problem just went away by installing the 32 bit MySQL connector instead.","Q_Score":26,"Tags":"mysql,python-3.x,installation","A_Id":54292906,"CreationDate":"2015-05-26T19:42:00.000","Title":"mysql installer fails to recognize python 3.4","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm trying to istall mysql server on a windows 7 machine - that has python 3.4.3 installed. However, when trying to install the python connectors for 3.4, the installer fails to recognize the python installation, saying python 3.4 is not installed. \nHas anyone solved this issue before? I'ts driving me nuts...","AnswerCount":12,"Available Count":7,"Score":0.0333209931,"is_accepted":false,"ViewCount":35704,"Q_Id":30467495,"Users Score":2,"Answer":"From my experience if you have both Py2.7 and Py3.4 installed when installing the mysql connector for py3.4 you will run into this issue. Not sure of the WHY but for some reason if you have py2.7 installed, the py3.4 mysql connector recognizes that version first and just assumes that you have py2.7 installed and does not recognize that py3.4 is installed.\nThe only way I have found around this is to uninstall py2.7 and then install the py3.4 mysql connector.  You can always install py2.7 again after the fact.","Q_Score":26,"Tags":"mysql,python-3.x,installation","A_Id":30468759,"CreationDate":"2015-05-26T19:42:00.000","Title":"mysql installer fails to recognize python 3.4","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm trying to istall mysql server on a windows 7 machine - that has python 3.4.3 installed. However, when trying to install the python connectors for 3.4, the installer fails to recognize the python installation, saying python 3.4 is not installed. \nHas anyone solved this issue before? I'ts driving me nuts...","AnswerCount":12,"Available Count":7,"Score":0.0,"is_accepted":false,"ViewCount":35704,"Q_Id":30467495,"Users Score":0,"Answer":"I had this problem until I discovered I had installed python based in another architecture (32b). MySQL required 64 bit.","Q_Score":26,"Tags":"mysql,python-3.x,installation","A_Id":53574430,"CreationDate":"2015-05-26T19:42:00.000","Title":"mysql installer fails to recognize python 3.4","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm trying to istall mysql server on a windows 7 machine - that has python 3.4.3 installed. However, when trying to install the python connectors for 3.4, the installer fails to recognize the python installation, saying python 3.4 is not installed. \nHas anyone solved this issue before? I'ts driving me nuts...","AnswerCount":12,"Available Count":7,"Score":0.0166651236,"is_accepted":false,"ViewCount":35704,"Q_Id":30467495,"Users Score":1,"Answer":"I was looking for an similar answer.  The correct answer is that there is a bug in the mysqlconnector MSI.  When python installs, it creates a registry entry under HKLM Software\\Python\\PythonCore\\3.6-32\\InstallPath  however, the MSI for mysqlconnector is looking for installation path in the registry Software\\Python\\PythonCore\\3.6\\InstallPath as part of the RegLocator\/registrypath variable.\nUse ORCA to edit the MSI, change the RegLocator so that -32 is in the path.  It will install now without error or changes to the system.","Q_Score":26,"Tags":"mysql,python-3.x,installation","A_Id":50449146,"CreationDate":"2015-05-26T19:42:00.000","Title":"mysql installer fails to recognize python 3.4","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm trying to istall mysql server on a windows 7 machine - that has python 3.4.3 installed. However, when trying to install the python connectors for 3.4, the installer fails to recognize the python installation, saying python 3.4 is not installed. \nHas anyone solved this issue before? I'ts driving me nuts...","AnswerCount":12,"Available Count":7,"Score":0.0,"is_accepted":false,"ViewCount":35704,"Q_Id":30467495,"Users Score":0,"Answer":"Here is a much simpler work around:\npip install mysql-connector-python\nIs the same package that MySQL is having trouble installing. Just use pip to install it.\nNext, go back to the installation style and select \"Manual\" instead of \"Developer\". They are identical, but \"Manual\" allows you to remove packages. Just remove the \"Connector\/Python\" package from the list to be installed.\nCarry on with the install, you're done.","Q_Score":26,"Tags":"mysql,python-3.x,installation","A_Id":61068804,"CreationDate":"2015-05-26T19:42:00.000","Title":"mysql installer fails to recognize python 3.4","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm not sure if this has been answered before, I didn't get anything on a quick search.\nMy table is built in a random order, but thereafter it is modified very rarely. I do frequent selects from the table and in each select I need to order the query by the same column. Now is there a way to sort a table permanently by a column so that it does not need to be done again for each select?","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":344,"Q_Id":30503358,"Users Score":3,"Answer":"You can add an index sorted by the column you want. The data will be presorted according to that index.","Q_Score":2,"Tags":"python,sqlalchemy","A_Id":30504339,"CreationDate":"2015-05-28T10:04:00.000","Title":"SQLAlchemy: how can I order a table by a column permanently?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"i have two models, when i do request.POST.get('room_id') or ('id') i'm getting an error Room matching query does not exist.\nhow to solved this problem? help me \n\n\n    class Room(models.Model):\n        status = models.BooleanField('Status',default=True)\n        name = models.CharField('Name', max_length=100, unique=True)\n\n    class Book(models.Model):\n        date = models.DateTimeField('Created',auto_now_add=True)\n        from_date = models.DateField('Check-in')\n        to_date = models.DateField('Check-out')\n        room = models.ForeignKey(Room, related_name='booking')\n\n\ni need detail room request get id, booked dates range(from_date,to_date)\n\ndef room_detail(request,pk):\n    room = get_object_or_404(Room,pk=pk)\n    if request.method == 'POST':\n        form = BookForm(request.POST,room=room)\n        if form.is_valid():\n            s = form.save(commit=True)          \n            s.save()\n            return redirect(request.path)\n    else:\n        form = BookForm()\n\n    #roomid = Room.objects.values('id')\n    type = request.POST.get('id') # or get('room_id')\n    rooms = Room.objects.get(id=type)\n\n    start_dates = rooms.booking.values_list('from_date',flat=True)\n    end_dates = rooms.booking.values_list('to_date',flat=True)\n    dates = [start + timedelta(days=i) for start, end in zip(start_dates,end_dates) for i in range((end-start).days+1)]\n\n    c = {}\n    c['form'] = form\n    return render_to_response('rooms_detail.html',c)\n\nplease help me, thanks in advance","AnswerCount":3,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":1484,"Q_Id":30517002,"Users Score":3,"Answer":"You are looking into request.POST, even if the request.method is not equal to 'POST'. This will not work, because when the request is not an HTTP-post, the POST-member of your request is empty.","Q_Score":1,"Tags":"django,python-3.x,django-queryset,models","A_Id":30517111,"CreationDate":"2015-05-28T20:59:00.000","Title":"django models request get id error Room matching query does not exist","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"First, the server setup:\n\nnginx frontend to the world\ngunicorn running a Flask app with gevent workers\nPostgres database, connection pooled in the app, running from Amazon RDS, connected with psycopg2 patched to work with gevent\n\nThe problem I'm encountering is inexplicably slow queries that are sometimes running on the order of 100ms or so (ideal), but which often spike to 10s or more.  While time is a parameter in the query, the difference between the fast and slow query happens much more frequently than a change in the result set. This doesn't seem to be tied to any meaningful spike in CPU usage, memory usage, read\/write I\/O, request frequency, etc.  It seems to be arbitrary.\nI've tried:\n\nOptimizing the query - definitely valid, but it runs quite well locally, as well as any time I've tried it directly on the server through psql.\nRunning on a larger\/better RDS instance - I'm currently working on an m3.medium instance with PIOPS and not coming close to that read rate, so I don't think that's the issue.\nTweaking the number of gunicorn workers - I thought this could be an issue, if the psycopg2 driver is having to context switch excessively, but this had no effect.\nMore - I've been working for a decent amount of time at this, so these were just a couple of the things I've tried.\n\nDoes anyone have ideas about how to debug this problem?","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1181,"Q_Id":30519299,"Users Score":0,"Answer":"You could try this from within psql to get more details on query timing\nEXPLAIN sql_statement\nAlso turn on more database logging. mysql has slow query analysis, maybe PostgreSQL has an equivalent.","Q_Score":0,"Tags":"python,postgresql,amazon-rds,gevent","A_Id":30519353,"CreationDate":"2015-05-29T00:34:00.000","Title":"Inconsistently slow queries in production (RDS)","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I can do http:\/\/127.0.0.1:5000\/people?where={\"lastname\":\"like(\\\"Smi%\\\")\"} to get people.lastname LIKE \"Smi%\" \nHow do I  concat two conditions, like where city=XX and pop<1000 ?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":113,"Q_Id":30672259,"Users Score":2,"Answer":"It's quite simple you just do:\nhttp:\/\/127.0.0.1:5000\/people?where={\"city\":\"XX\", \"pop\":\"<1000\"}","Q_Score":1,"Tags":"python,sqlalchemy,eve","A_Id":30680531,"CreationDate":"2015-06-05T17:15:00.000","Title":"Eve SQLAlchemy query catenation","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm working on a project where I have to store about 17 million 128-dimensional integer arrays e.g [1, 2, 1, 0, ..., 2, 6, 4] and I'm trying to figure out what's the best way to do it. \nThe perfect solution would be one that makes it fast to both store and retrieve the arrays, since I need to access ALL of them to make calculations. With such a vast amount of data, I obviously can't store them all in memory in order to make calculations, so accessing batches of arrays should be as fast as possible.\nI'm working in Python.\nWhat do you recommend ? Using a DB (SQL vs NOSQL ?), storing it in a text file, using python's Pickle?","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1207,"Q_Id":30682311,"Users Score":0,"Answer":"It seems not so big with numpy arrays, if your integers are 8 bits.   a=numpy.ones((17e6,128),uint8) is created in less than  a second on my computer.  but ones((17e6,128),uint16) is difficult, and  ones((17e6,128),uint64) crashed.","Q_Score":2,"Tags":"python,sql,arrays,database,nosql","A_Id":30684782,"CreationDate":"2015-06-06T11:32:00.000","Title":"Fastest way to store and retrieve arrays","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"My use case is simple, i have performed some kind of operation on image and the resulting feature vector is a numpy object of shape rowX1000(what i mean to say is that the row number can be variable but column number is always 1000)\nI want to store this numpy array in mysql. No kind of operation is to be performed on this array. The query will be simple given a image name return the whole feature vector. so is there any way in which the array can be stored (something like a magic container which encapsulates the array and then put it on the table and on retrieval it retrieves the magic container and pops out the array)\nI want to do this in python. If possible support with a short code snippit of how to put the data in the mysql database.","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":7366,"Q_Id":30713062,"Users Score":8,"Answer":"You could use ndarray.dumps() to pickle it to a string then write it to a BLOB field? Recover it using numpy.loads()","Q_Score":9,"Tags":"python,mysql,arrays,numpy","A_Id":30713767,"CreationDate":"2015-06-08T15:20:00.000","Title":"store numpy array in mysql","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"i have tried import file csv using bulk insert but it is failed, is there another way in query to import csv file without using bulk insert ?\nso far this is my query but it use bulk insert :\nbulk insert [dbo].[TEMP] from \n\n'C:\\Inetpub\\vhosts\\topimerah.org\\httpdocs\\SNASPV0374280960.txt' with\n  (firstrow=2,fieldterminator = '~', rowterminator = ' ');","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":777,"Q_Id":30724143,"Users Score":0,"Answer":"My answer is to work with bulk-insert.\n1. Make sure you have bulk-admin permission in server.\n2. Use SQL authentication login (For me most of the time window authentication login haven't worked.) for bulk-insert operation.","Q_Score":0,"Tags":"python,mysql,sql,sql-server,csv","A_Id":30724975,"CreationDate":"2015-06-09T06:05:00.000","Title":"how to import file csv without using bulk insert query?","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a couple thousand lines of data in excel. In one column, however, only every fifth line is filled. What I'm trying to do is fill in the four empty lines below each filled line with the data from the line above. I have a beginner's grasp of python, so if someone could steer me in the right direction, it would be a great help. Thanks a lot.","AnswerCount":3,"Available Count":1,"Score":0.1325487884,"is_accepted":false,"ViewCount":1002,"Q_Id":30810963,"Users Score":2,"Answer":"Based on your description, this seems easy enough to do in Excel: \nAssume row 1 contains column headers, and data begin in row 2. If column A contains your values (starting in A2), in cell B2 use the formula =IF(ISBLANK(A2), B1, A2) and fill down. This formula will return the value of A2 if it is not blank, and will return the previous value in column B if the current value in column A is blank.\nNote that this requires that the first cell in each group contains the value that you want to fill down.\nA post-script for general reference: Excel has a hard time with blank cells resulting from formulas, so the formula =\"\" (or the result of something like =IFERROR(..., \"\")) is not blank, but does have a length of 0. Changing ISBLANK(A2) to LEN(A2)<1 accounts for these situations.","Q_Score":0,"Tags":"python,excel","A_Id":30811295,"CreationDate":"2015-06-12T19:39:00.000","Title":"Filling in missing data in excel","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"What is the convention\/best practices for naming database tables in Django... using the default database naming scheme (appname_classname) or creating your own table name (using your own naming conventions) with the meta class?","AnswerCount":1,"Available Count":1,"Score":0.537049567,"is_accepted":false,"ViewCount":1656,"Q_Id":30872599,"Users Score":3,"Answer":"The default convention is better and cleaner to use :\n\nIt avoids any table naming conflict ( As It's a combination of App name and Model name)\nIt creates well organized database (Tables are ordered by App names)\n\nSo until you have any special case that needs special naming convention , use the default.","Q_Score":0,"Tags":"python,django,database,naming-conventions","A_Id":30872816,"CreationDate":"2015-06-16T15:57:00.000","Title":"Django database table naming convention","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"If I ftp into a database and use pandas.read_sql to read in a huge file, what data type would the variable set equal to this be? And, if applicable, what kind of format would it be in? What object type is a pandas data frame?","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":160,"Q_Id":30881489,"Users Score":1,"Answer":"Variable = ?\nThe variable set would be equal to a pandas.core.frame.DataFrame object. \nFormat?\nThe pandas.core.frame.DataFrame format is a collection of numpy ndarrays, dicts, series, arrays or list-like structures that make up a 2 dimensional (typically) tabular data structure.\nPandas Object Type?\nA pandas.core.frame.DataFrame object is an organized collection of list like structures containing multiple data types.","Q_Score":0,"Tags":"python,pandas","A_Id":30881760,"CreationDate":"2015-06-17T02:46:00.000","Title":"Data type using Pandas","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"If I ftp into a database and use pandas.read_sql to read in a huge file, what data type would the variable set equal to this be? And, if applicable, what kind of format would it be in? What object type is a pandas data frame?","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":160,"Q_Id":30881489,"Users Score":0,"Answer":"The function pandas.read_sql returns a DataFrame. \nThe type of a DataFrame in pandas is pandas.core.frame.DataFrame.","Q_Score":0,"Tags":"python,pandas","A_Id":30881700,"CreationDate":"2015-06-17T02:46:00.000","Title":"Data type using Pandas","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm using Python 3.4. I have a binary column in a my postgresql database with some files and I need to retrieve it from the database and read it... the problem is that for this to work, I first have to (1) open a new file in the filesystem with 'wb', (2) write the contents of the binary column and then (3) read() the filesystem file with 'rb'. \nI would like to skip this whole process... I just wanto to get the file from the database, into a variable and use it AS IF IT WAS OPENED from the filesystem...  \nHow can I do that? I already tried BytesIO and it does not work...\nThank you","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":176,"Q_Id":30920656,"Users Score":0,"Answer":"Answering my own question: bytes(file)","Q_Score":0,"Tags":"python,database,python-3.x,io","A_Id":30922498,"CreationDate":"2015-06-18T16:16:00.000","Title":"Reading a file from database binary column (postgresql) in memory without having to save and open the file in the filesystem","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a txt file with about 100 million records (numbers). I am reading this file in Python and inserting it to MySQL database using simple insert statement from python. But its taking very long and looks like the script wouldn't ever finish. What would be the optimal way to carry out this process ? The script is using less than 1% of memory and 10 to 15% of CPU.\nAny suggestions to handle such large data and insert it efficiently into database, would be greatly appreciated.\nThanks.","AnswerCount":3,"Available Count":1,"Score":0.0665680765,"is_accepted":false,"ViewCount":13099,"Q_Id":30928713,"Users Score":1,"Answer":"Having tried to do this recently, I found a fast method, but this may be because I'm using an AWS Windows server to run python from that has a fast connection to the database.  However, instead of 1 million rows in one file, it was multiple files that added up to 1 million rows.  It's faster than other direct DB methods I tested anyway.\nWith this approach, I was able to read files sequentially and then run the MySQL Infile command. I then used threading with this process too.  Timing the process it took 20 seconds to import 1 million rows into MySQL.\nDisclaimer: I'm new to Python, so I was trying to see how far I could push this process, but it caused my DEV AWS-RDS DB to become unresponsive (I had to restart it), so taking an approach that doesn't overwhelm the process is probably best!","Q_Score":4,"Tags":"python,mysql,insert,sql-insert,large-data","A_Id":53005996,"CreationDate":"2015-06-19T01:55:00.000","Title":"Inserting millions of records into MySQL database using Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am writing a web tool using Python and Pyramid. It access a MySQL database using MySQLdb and does queries based on user input. I created a user account for the tool and granted it read access on the tables it uses. \nIt works fine when I open the page in a single tab, but if I try loading it in second tab the page won't load until the first search is finished. Is there a way to get around this or am I just trying to use MySQL incorrectly?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":69,"Q_Id":30948885,"Users Score":1,"Answer":"What @AlexIvanov is trying to say is that when you're starting your Pyramid app in console it is served using Pyramid's built-in development server. This server is single-threaded and serves requests one after another, so if you have a long request which takes, say, 15 seconds - you won't be able to use your app in another tab until that long request finishes. This sequential nature of the built-in webserver is actually an awesome feature which greatly simplifies debugging.\nIn production, your Pyramid app is normally served by a \"real\" webserver, such as Apache or Nginx. Such webservers normally spawn multiple \"workers\", or use multiple threads which allow them to serve multiple concurrent requests.\nSo I suspect there's nothing wrong with your setup (provided you didn't do anything particularly strange with Pyramid's initial scaffold and it's still using SQLAlchemy's session configured with ZopeTransactionExtension etc.). \nA \"single shared MySQL account\" in no way prevents multiple connected clients from running queries concurrently in MySQL - the thing is, with the development server you only have one single-threaded client.","Q_Score":0,"Tags":"python,mysql,pyramid,mysql-python","A_Id":30969950,"CreationDate":"2015-06-19T23:56:00.000","Title":"Accessing MySQL from multiple views of a web site","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a web application (based on Django 1.5) wherein a user uploads a spreadsheet file. \nI've been using xlrd for manipulating xls files and looked into openpyxl which claims to support xlsx\/xlsm files. \nSo is there a common way to read\/write both xls and xlsx files? \nAnother option could be to convert the uploaded file to xls and use xlrd. For this I looked into gnumeric and ssconvert, this would be favorable since all my existing code in written using xlrd and I will not have to change the existing codebase.\nSo should I change the library I use or go with the conversion solution?\nThanks in advance.","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":1651,"Q_Id":30974575,"Users Score":1,"Answer":"xlrd can read both xlsx and xls files, so it's probably simplest to use that. Support for xlsx isn't as extensive as openpyxl but should be sufficient.\nThere's a risk of losing information in converting xlsx to xls because xlsx files can be much larger.","Q_Score":0,"Tags":"python,xlrd,openpyxl","A_Id":30974768,"CreationDate":"2015-06-22T07:48:00.000","Title":"How do I read\/write both xlsx and xls files in Python?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm using openpyxl to write to an existing file and everything works fine. However after the data is saved on the file, graphs disappear. \nI understand Openpyxl currently only supports chart creation within a worksheet only. Charts in existing workbooks will be lost.\nAre there any alternate libraries in Python to achieve this. I just want to feed a few values, so all the graphs and calculation happen in excel.\nThank you.","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":2336,"Q_Id":31020766,"Users Score":0,"Answer":"This is currently (version 2.2) not possible.","Q_Score":1,"Tags":"python,excel,openpyxl","A_Id":31022634,"CreationDate":"2015-06-24T07:49:00.000","Title":"Graphs lost while overwriting to existing excel file in Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Is this a known limitation that will be addressed at some point, or is this just something that I need to accept?\nIf this is not possible with xlwings, I wonder if any of the other alternatives out there supports connecting to other instances.\nI'm specifically talking about the scenario where you are calling python from within Excel, so the hope is that the getCaller() function will be able to figure out which instance of the Excel is actually calling it.","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":1096,"Q_Id":31106542,"Users Score":1,"Answer":"Ok, based on your comments I think I can answer your question: Actually, yes, xlwings can handle various instances. But workbooks from untrusted locations (like downloaded from the internet or sometimes on shared network drives) don't play nicely.\nSo in your case you could try to add the network location to File > Options > Trust Center >  Trust Center Settings... > Trusted Locations or, under Trusted Documents, tick the checkbox Allow documents on a network to be trusted.\nIf you don't have the previlegies to change these options, then I guess you're left with the options of running the tools locally or indeed, open them in the 1st instance...","Q_Score":1,"Tags":"python,xlwings","A_Id":31110844,"CreationDate":"2015-06-29T01:26:00.000","Title":"Does xlwings only work with the first instance of Excel?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have limited experience with Jira and Jira query language. \nThis is regarding JIRA Query language. I have a set of 124 rows (issues) in Jira that are under a certain 'Label' say 'myLabel'.\nI need to extract columns col1, col2 and col5 for all of the above 124 rows where the Label field is 'myLabel'.\nOnce I have the above result I need to export it to an excel sheet. Is there a JIRA query that I can fire to do this ?\nOr Is there some other way that this can be done, like maybe exporting all of the 124 rows with all the n columns to a SQL table and then doing an SQL query on top of it to retrieve the results that is needed ?\nAlso there is something python-jira. Can that be of some help ?","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":1804,"Q_Id":31123357,"Users Score":1,"Answer":"One way of doing this stuff what you want to do is with Excel directly.\n0. create the filter in JIRA\n1. create a VBA for Excel script which will Open the Exported to Excel filter from JIRA. In order to do that you have to copy the link from JIRA, -> export -> Excel current fields. \n2. Most probably you will have to login first to JIRA from EXCEL VBA, so I recommend you to do this by logging in with REST requests from excel.\n3. Copy all the information from the exported JIRA query to your other worksheet\n4. After copying you can then process as you wish easily with VBA the list of tickets.\nI know this is not the straight forward way of doing this stuff, but I hope it helped you a little to go further into your searches.","Q_Score":1,"Tags":"jira,jira-plugin,jql,python-jira","A_Id":31676903,"CreationDate":"2015-06-29T18:54:00.000","Title":"JQL to retrive specific columns for a cetain label","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am interested in using a cursor to duplicate a database from one mongod to another. I want to limit the amount of insert requests sent so instead of inserting each document in the cursor individually I want to do an insert_many of each cursor batch. \nIs there a way to do this in pymongo\/python? \nI have tried converting the cursor to a list and then calling insert_many and this works, but if the collection is over the amount of ram that I have then it won't work. \nAny ideas on how to grab a batch from a cursor and convert it to a list would be appreciated\nThanks!","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1052,"Q_Id":31123896,"Users Score":0,"Answer":"So far this has been my \"slice\/batch\" solution and it has been much more effective than individually iterating each document from the cursor:\n\nKeep note of the id field last document you have grabbed\nOpen a cursor with the query \"Greater than _id of last doc\" and with a limit of \nwhatever your batch_size is\nNow you should have a cursor with your desired number of documents in a batch\nMake this cursor into a python list by doing list(cursor)\nInsert_many on this list \nUpdate last grabbed, and delete the list to free up ram\n\nYou can adjust your batch size to accommodate your RAM limitations. This is a pretty good solution because it reduces the bottleneck of cursor iteration, and also doesn't take too much ram as you are constantly deleting the batches as you go on.","Q_Score":1,"Tags":"python,mongodb,cursor,pymongo","A_Id":31413796,"CreationDate":"2015-06-29T19:24:00.000","Title":"How to insertmany from a cursor using Pymongo?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm hoping to be pointed in the right direction as far as what tools to use while in the process of developing an application that runs on two servers per client. \n[Main Server][Client db Server]\nEach client has their own server which has a django application managing their respective data, in addition to serving as a simple front end. \nThe main application server has a more feature-rich front end, using the same models\/db schemas. It should have full read\/write access to the client's database server.\nThe final desired effect would be a typical SaaS type deal: \nclient1.djangoapp.com => Connects to mysql database @ client1_IP\nclient2.djangoapp.com => Connects to mysql database @ client2_IP...\nThanks in advance!","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":843,"Q_Id":31226223,"Users Score":1,"Answer":"You could use different settings files, let's say settings_client_1.py and settings_client_2.py, import common settings from a common settings.py file to keep it DRY. Then add respective database settings. \nDo the same with wsgi files, create one for each settings. Say, wsgi_c1.py and wsgi_c2.py\nThen, in your web server direct the requests for client1.djangoapp.com to wsgi_c1.py and client2.djangoapp.com to wsgi_c2.py","Q_Score":0,"Tags":"python,django,web-deployment,multi-tenant,saas","A_Id":31227735,"CreationDate":"2015-07-05T00:30:00.000","Title":"Effectively communicating between two Django applications on two servers (Multitenancy)","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I've been trying to write a script to copy formatting from one workbook to another and, as anyone dealing with openpyxl knows, it's a big script.  I've gotten it to work pretty well, but one thing I can't seem to figure out is how to read from the original if columns are hidden.\nCan anyone tell me where to look in a workbook, worksheet, column or cell object to see where hidden columns are?","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":5323,"Q_Id":31257353,"Users Score":3,"Answer":"Worksheets have row_dimensions and column_dimensions objects which contain information about particular rows or columns, such as whether they are hidden or not. Column dimensions can also be grouped so you'll need to take that into consideration when looking.","Q_Score":5,"Tags":"python,excel,openpyxl","A_Id":31262488,"CreationDate":"2015-07-06T23:26:00.000","Title":"Finding hidden cells using openpyxl","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Let's suppose we have a single host where there is a Web Server and a Database Server. \nAn external application sends an http request to the web server to access to the database. \nThe data access logic is made for example by Python API.\nThe web server takes the request and the Python application calls the method to connect to the database, e.g. MySQLdb.connect(...).\nWhich process establishes the connection with the database server and communicates with it? Is it the web server process?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":26,"Q_Id":31274509,"Users Score":1,"Answer":"Yes, as Python application lives inside of the web server process, this process will establish the connection with database server.","Q_Score":0,"Tags":"python,webserver,database-connection,data-access-layer,database-server","A_Id":31274653,"CreationDate":"2015-07-07T16:37:00.000","Title":"Which process establishes the connection with the database server?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm making an application that will fetch data from a\/n (external) postgreSQL database with multiple tables.\nAny idea how I can use inspectdb only on a SINGLE table? (I only need that table)\nAlso, the data in the database would by changing continuously. How do I manage that? Do I have to continuously run inspectdb? But what will happen to junk values then?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":78,"Q_Id":31295352,"Users Score":0,"Answer":"I think you have misunderstood what inspectdb does. It creates a model for an existing database table. It doesn't copy or replicate that table; it simply allows Django to talk to that table, exactly as it talks to any other table. There's no copying or auto-fetching of data; the data stays where it is, and Django reads it as normal.","Q_Score":0,"Tags":"python,django,postgresql,python-2.7,django-1.8","A_Id":31309910,"CreationDate":"2015-07-08T14:15:00.000","Title":"Django 1.8 and Python 2.7 using PostgreSQL DB help in fetching","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'd like people's views on current design I'm considering for a tornado app. Although I'm using mongoDB to store permanent information I currently have the session information as a python data structure that I've simply added within the Application object at initialisation. \nI will need to perform some iteration and manipulation of the sessions while the server is running. I keep debating whether to move these to another mongoDB or just keep it as a python structure.\nIs there anything wrong with keeping session information this way?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":120,"Q_Id":31311620,"Users Score":2,"Answer":"If you store session data in Python your apllication will:\n\nloose it if you stop the Python process;\nlikely consume more memory as Python isn't very efficient in memory management (and you will have to store all the sessions in memory, not the ones you need right now).\n\nIf these are not problems for you you can go with Python structures. But usually these are serious concerns and most of the projects use some external storage for sessions.","Q_Score":0,"Tags":"python,mongodb,tornado,tornado-motor","A_Id":31311950,"CreationDate":"2015-07-09T08:07:00.000","Title":"Tornado Application design","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I want to enter data into a Microsoft Excel Spreadsheet, and for that data to interact and write itself to other documents and webforms.  \nWith success, I am pulling data from an Excel spreadsheet using xlwings.  Right now, I\u2019m stuck working with .docx files.  The goal here is to write the Excel data into specific parts of a Microsoft Word .docx file template and create a new file.  \nMy specific question is:\nCan you modify just a text string(s) in a word\/document.xml file and still maintain the integrity and functionality of its .docx encasement?  It seems that there are numerous things that can change in the XML code when making even the slightest change to a Word document.  I've been working with python-docx and lxml, but I'm not sure if what I seek to do is possible via this route.\nAny suggestions or experiences to share would be greatly appreciated.  I feel I've read every article that is easily discoverable through a google search at least 5 times.  \nLet me know if anything needs clarification.\nSome things to note:\nI started getting into coding about 2 months ago.  I\u2019ve been doing it intensively for that time and I feel I\u2019m picking up the essential concepts, but there are severe gaps in my knowledge.\nHere are my tools:\nYosemite 10.10,\nMicrosoft Office 2011 for Mac","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":581,"Q_Id":31346625,"Users Score":1,"Answer":"You probably need to be more specific, but the short answer is, in principle, yes.\nAt a certain level, all python-docx does is modify strings in the XML. A couple things though:\n\nThe XML you create needs to remain well-formed and valid according to the schema. So if you change the text enclosed in a <w:t> element, for example, that works fine. Conversely, if you inject a bunch of random XML at an arbitrary point in one of the .xml parts, that will corrupt the file.\nThe XML \"files\", known as parts that make up a .docx file are contained in a Zip archive known as a package. You must unpackage and repackage that set of parts properly in order to have a valid .docx file afterward. python-docx takes care of all those details for you, but if you're going directly at the .docx file you'll need to take care of that yourself.","Q_Score":2,"Tags":"python,xml,lxml,docx,python-docx","A_Id":31349163,"CreationDate":"2015-07-10T17:13:00.000","Title":"Can you modify only a text string in an XML file and still maintain integrity and functionality of .docx encasement?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm trying to install PyODBC on Heroku, but I get fatal error: sql.h: No such file or directory in the logs when pip runs.  How do I fix this error?","AnswerCount":7,"Available Count":4,"Score":0.0,"is_accepted":false,"ViewCount":62898,"Q_Id":31353137,"Users Score":0,"Answer":"RedHat\/CentOS:\ndnf install -y unixODBC-devel\nalong with unixODBC installation","Q_Score":83,"Tags":"python,heroku,pyodbc","A_Id":61108863,"CreationDate":"2015-07-11T03:31:00.000","Title":"sql.h not found when installing PyODBC on Heroku","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm trying to install PyODBC on Heroku, but I get fatal error: sql.h: No such file or directory in the logs when pip runs.  How do I fix this error?","AnswerCount":7,"Available Count":4,"Score":0.0285636566,"is_accepted":false,"ViewCount":62898,"Q_Id":31353137,"Users Score":1,"Answer":"I recently saw this error in Heroku. To fix this problem I took the following steps:\n\nAdd Apt File to the root folder, with the following:\nunixodbc\nunixodbc-dev\npython-pyodbc\nlibsqliteodbc\nCommit that\nRun heroku buildpacks:clear\nRun heroku buildpacks:add --index 1 heroku-community\/apt\nPush to Heroku\n\nFor me the problem was that I previously installed the buildpack for python, which was not needed. By running heroku buildpacks:clearI removed all un-needed buildpacka, then add back the one I needed. So if you do follow these steps be sure to make note of the build packs you need. To view the buildpacks you have run heroku buildpacks before following these steps.","Q_Score":83,"Tags":"python,heroku,pyodbc","A_Id":59790771,"CreationDate":"2015-07-11T03:31:00.000","Title":"sql.h not found when installing PyODBC on Heroku","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm trying to install PyODBC on Heroku, but I get fatal error: sql.h: No such file or directory in the logs when pip runs.  How do I fix this error?","AnswerCount":7,"Available Count":4,"Score":0.0285636566,"is_accepted":false,"ViewCount":62898,"Q_Id":31353137,"Users Score":1,"Answer":"The other answers are more or less correct; you're missing the unixodbc-dev[el] package for your operating system; that's what pip needs in order to build pyodbc from source.\nHowever, a much easier option is to install pyodbc via the system package manager. On Debian\/Ubuntu, for example, that would be apt-get install python-pyodbc. Since pyodbc has a lot of compiled components and interfaces heavily with the UnixODBC OS-level packages, it is probably a better fit for a system package rather than a Python\/pip-installed one.\nYou can still list it as a dependency in your requirements.txt files if you're making code for distribution, but it'll usually be easier to install it via the system PM.","Q_Score":83,"Tags":"python,heroku,pyodbc","A_Id":47557567,"CreationDate":"2015-07-11T03:31:00.000","Title":"sql.h not found when installing PyODBC on Heroku","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm trying to install PyODBC on Heroku, but I get fatal error: sql.h: No such file or directory in the logs when pip runs.  How do I fix this error?","AnswerCount":7,"Available Count":4,"Score":1.0,"is_accepted":false,"ViewCount":62898,"Q_Id":31353137,"Users Score":8,"Answer":"You need the unixODBC devel package. I don't know what distro you are using but you can google it and build from source.","Q_Score":83,"Tags":"python,heroku,pyodbc","A_Id":31358757,"CreationDate":"2015-07-11T03:31:00.000","Title":"sql.h not found when installing PyODBC on Heroku","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"We have a ticket software to manage our work, every ticket is assigned to a tech in one field -the normal stuff-, but now we want to assign the same ticket to several technicians eg: tick 5432: tech_id(2,4,7) where 2,4,7 are tech IDs.\nOf course we can do that using a separate table with the IDs of the tech and the ticket ID, but we have to convert the data.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":136,"Q_Id":31369558,"Users Score":0,"Answer":"The \"right\" way to do this is to have a separate table of ticket\nassignments. Converting the data for something like this is fairly simple on the database end.  create table assign as select tech_id from ... followed by creating any necessary foreign key constraints.\nRewriting your interface code can be trickier, but you're going to\nhave to do that anyway to allow for more than one tech.\nYou could use an array type, but sometimes database\ninterfaces don't understand postgres array types.  There isn't anything\ninherent in arrays that prevents duplicates or imposes ordering, but\nyou could do that with an appropriate trigger.","Q_Score":0,"Tags":"python,postgresql","A_Id":31371403,"CreationDate":"2015-07-12T15:40:00.000","Title":"Is any variable in PostgreSQL to store a list","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am using Spark 1.3.1 (PySpark) and I have generated a table using a SQL query. I now have an object that is a DataFrame. I want to export this DataFrame object (I have called it \"table\") to a csv file so I can manipulate it and plot the columns. How do I export the DataFrame \"table\" to a csv file?\nThanks!","AnswerCount":9,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":340481,"Q_Id":31385363,"Users Score":0,"Answer":"try display(df) and use the download option in the results. Please note: only 1 million rows can be downloaded with this option but its really quick.","Q_Score":106,"Tags":"python,apache-spark,dataframe,apache-spark-sql,export-to-csv","A_Id":69462087,"CreationDate":"2015-07-13T13:56:00.000","Title":"How to export a table dataframe in PySpark to csv?","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a fairly large redshift table with around 200 million records.  I would like to update the values in one of the columns using a user-defined python function.  If I run the function in an EC2 instance, it results in millions of updates to the table, and it is very slow.  Is there a better process for me to speed up these updates?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":56,"Q_Id":31388220,"Users Score":0,"Answer":"Unlike row-based systems, which are ideal for transaction processing, column-based systems (Redshift) are ideal for data warehousing and analytics, where queries often involve aggregates performed over large data sets. Since only the columns involved in the queries are processed and columnar data is stored sequentially on the storage media, column-based systems require far fewer I\/Os, greatly improving query performance.\nIn your example instead of doing multiple separate updatecommands you can perform a single update .. set.. from ... where ....","Q_Score":0,"Tags":"python,amazon-web-services","A_Id":31411856,"CreationDate":"2015-07-13T16:05:00.000","Title":"How to increase performance of large number of updates to a redshift table with python functions","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Everything I found about this via searching was either wrong or incomplete in some way. So, how do I:\n\ndelete everything in my postgresql database\ndelete all my alembic revisions\nmake it so that my database is 100% like new","AnswerCount":3,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":7991,"Q_Id":31392285,"Users Score":3,"Answer":"This works for me:\n1) Access your session, in the same way you did session.create_all, do session.drop_all. \n2) Delete the migration files generated by alembic.\n3) Run session.create_all and initial migration generation again.","Q_Score":7,"Tags":"python,postgresql,sqlalchemy,alembic","A_Id":31392595,"CreationDate":"2015-07-13T19:56:00.000","Title":"Clear postgresql and alembic and start over from scratch","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a 2D array, M 390x420 with float values in it that I would like to save as a table in a sqlite db with python. the row number of the table should be 390, the column number 420.\nexecutemany from sqlite is not optimal because then I would have to write ~ 420 of \"?\" , as far as I've understood.\nThank you!","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1249,"Q_Id":31426367,"Users Score":0,"Answer":"As CL recommended, not to use 420 columns. I would recommend an algorithmic approach to save much processing power. Here is an example, since the size is always 390x420, have a table with 10 columns, and 16380 rows. Referencing any point on this matrix can be done with a simple algorithm, and would be much more efficient. Remember, in sql, it is always better to have more rows than columns because of how the data is managed.","Q_Score":0,"Tags":"python,sqlite,matrix","A_Id":48332928,"CreationDate":"2015-07-15T09:20:00.000","Title":"save a matrix (or a 2 dimensional array) in a sqlite db with Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Each module in odoo have a table in the database.\nI'd like to know if I can create two tables in the odoo database for one module.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":592,"Q_Id":31456406,"Users Score":0,"Answer":"Yes you can, for every class new_class(... with a unique _name=\"new.class\" is created a table in the data base, if you want more than one table, you need to create more than one class in your .py file\nFor more reference look the account module in account_invoice.py you have class account_invoice(models.Model):  _name = \"account.invoice\" and class account_invoice_line(models.Model):  _name = \"account.invoice.line\" for each class are a table in the data base.\nI Hope this will can help you!","Q_Score":0,"Tags":"python-2.7,openerp,odoo","A_Id":31456810,"CreationDate":"2015-07-16T14:00:00.000","Title":"Is there any way to create two tables in the database for one odoo module?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am running a migrate script in postgres, and at the top of one of the files I have from sqlalchemy import *\nin the file I create tables with entries such as\n1Column('tmp1', DOUBLE_PRECISION(precision=53))\nHowever, when I run the script I get the error: \nname 'DOUBLE_PRECISION' is not defined\nWhy is this?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":622,"Q_Id":31459477,"Users Score":0,"Answer":"First off, I'd advise against doing 'from  import *' that can bring unknown things into your namespace that are quite difficult to debug.\nSecond, the sqlalchemy module simply doesn't have a 'DOUBLE_PRECISION' column type. So the reason it says it's not defined, is because sqlalchemy does not define any such name. Perhaps you are looking for 'Float'?","Q_Score":0,"Tags":"python,postgresql,sqlalchemy","A_Id":34866070,"CreationDate":"2015-07-16T16:15:00.000","Title":"name 'DOUBLE_PRECISION' is not defined - PostgreSQL - SQLAlchemy","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am using SQLAlchemy and am trying to update a boolean column value. I have the following command:\nsess.query(Testing).filter(Testing.id == id).update({Testing.state: True})\nI do not seem to get any errors, however, when I go to the database, nothing changes. Have I implemented something incorrectly with the command?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":277,"Q_Id":31517753,"Users Score":0,"Answer":"I simply left out sess.commit() as the next line of code.","Q_Score":0,"Tags":"python,sql","A_Id":31517891,"CreationDate":"2015-07-20T13:25:00.000","Title":"SQLAlchemy Update Command","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm wondering if there is any built-in way in Python to test a MySQL server connection. I know I can use PyMySQL, MySQLdb, and a few others, but if the user does not already have these dependencies installed my script will not work? How can I write a Python script to test a MySQL connection without requiring external dependencies?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":244,"Q_Id":31524210,"Users Score":2,"Answer":"Python distributions do not include support for MySQL, which is only available by installing a third-party module such as PyMySQL or MySQLdb. The only relational support included in Python is for the SQLite database (in the shape of the sqlite3 module).\nThere is, however, nothing to stop you distributing a third-party module as a part of your application, thereby including the support your project requires. PyMySQL would probably be the best choice because, being pure Python, it will run on any platform and give you best portability.","Q_Score":0,"Tags":"python,mysql","A_Id":31524504,"CreationDate":"2015-07-20T18:54:00.000","Title":"Test MySQL Connection with default Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I've been trying to do this and I really got no clue. I've search a lot and i know that i can merge the files with easily with VBA or other languages, but i really want to do it with Python.\nCan anyone get me on track?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":262,"Q_Id":31530728,"Users Score":1,"Answer":"I wished there was a straight forward support from openpyxl\/xlsxwriter to copy sheets across different workbooks.\nHowever, I see you would have to mash up a recipe using a couple of libraries:\n\nOne for reading the worksheet data and,\nAnother for writing data to a unified xlsx\n\nFor both of the above there are lot of options in terms of python packages.","Q_Score":2,"Tags":"python,excel","A_Id":31531821,"CreationDate":"2015-07-21T05:01:00.000","Title":"Merge(Combine) several .xlsx with one worksheet into just one workbook (Python)","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have an excel file with 234 rows and 5 columns. I want to create an array for each column so that when I can read each column separately in xlrd. Does anyone can help please?","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":898,"Q_Id":31540437,"Users Score":0,"Answer":"I might, but as a former user of the excellent xlrd package, I really would recommend switching to pyopenxl. Quite apart from other benefits, each worksheet has a columns attribute that is a list of columns, each column being a list of cells. (There is also a rows) attribute.\nConverting your code would be relatively painless as long as there isn't too much and it's reasonably well-written. I believe I've never had do do anything other than pip install pyopenxl to add it to a virtual environment.\nI observe that there's no code in your question, and it's harder (and more time-consuming) to write examples than point out required changes in code, so since you are an xlrd user I'm going to assume that you can take it from here. If you need help, edit the question and add your problem code. If you get through to what you want, submit it as an answer and mark it correct.\nSuffice to say I recently wrote some code to extract Pandas datasets from UK government health statistics, and pyopenxl was amazingly helpful in my investigations and easy to use.\nSince it appears from the comments this is not a new question I'll leave it at that.","Q_Score":1,"Tags":"python","A_Id":31540754,"CreationDate":"2015-07-21T13:27:00.000","Title":"Creating arrays in Python by using excel data sheet","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Im using python 2.7 with mongodb as my database. (actually it dosen't matter which database i use)\nIn my database i have millions of documents, from time to time i need to iterate over all of them.\nIt's not realistic to pull all the documents in one query because that will kill the memory, instead i pull each iteration 1000 documents and iterate them, when i finish i'm pulling another 1000 and so on.\nI was wondering if there is any formula to calculate the best number of pulling each iteration from the database.\nI couldn't find over the internet something that answer my issue.\nBasically my question is what is the best way of finding the best number to pull from the database in each iteration.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":48,"Q_Id":31542307,"Users Score":0,"Answer":"The only chance you have is to take some sample documents to calculate their average size. The more difficult part is to know what the available memory is, keeping in mind that there are other processes that consume ram in parallel!\nSo even when you take this road, you need to keep an amount of ram free. I doubt that the effort is worth it.","Q_Score":0,"Tags":"python,sql,mongodb,memory-management,mongoengine","A_Id":31543147,"CreationDate":"2015-07-21T14:44:00.000","Title":"Decide how many documents to pull from Database for memory utilization","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I used to use manage.py sqlall app to dump the database to sql statements. While, after upgrading to 1.8, it doesn't work any more.\nIt says:\n\nCommandError: App 'app' has migrations. Only the sqlmigrate and\n  sqlflush commands can be used when an app has migrations.\n\nIt seems there is not a way to solve this.\nI need to dump the database to sql file, so I can use it to clone the whole database else where, how can I accomplish this?","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":309,"Q_Id":31545025,"Users Score":1,"Answer":"You can dump the db directly with mysqldump as allcaps suggested, or run manage.py migrate first and then it should work. It's telling you there are migrations that you have yet to apply to the DB.","Q_Score":1,"Tags":"python,django,django-models","A_Id":31545842,"CreationDate":"2015-07-21T16:49:00.000","Title":"Django: How to dump the database in 1.8?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I've been struggling with \"sqlite3.OperationalError database is locked\" all day....  \nSearching around for answers to what seems to be a well known problem I've found that it is explained most of the time by the fact that sqlite does not work very nice in multithreading where a thread could potentially timeout waiting for more than 5 (default timeout) seconds to write into the db because another thread has the db lock .\nSo having more threads that play with the db , one of them using transactions and frequently writing I've began measuring the time it takes for transactionns to complete. I've found that no transaction takes more than 300 ms , thus rendering as not plausible the above explication. Unless the thread that uses transactions makes ~21 (5000 ms \/ 300 ms) consecutive transactions while any  other thread desiring to write gets ignored all this time\nSo what other hypothesis could potentially explain this behavior ?","AnswerCount":2,"Available Count":1,"Score":1.0,"is_accepted":false,"ViewCount":4653,"Q_Id":31547234,"Users Score":9,"Answer":"I have had a lot of these problems with Sqlite before. Basically, don't have multiple threads that could, potentially, write to the db. If you this is not acceptable, you should switch to Postgres or something else that is better at concurrency.\nSqlite has a very simple implementation that relies on the file system for locking. Most file systems are not built for low-latency operations like this. This is especially true for network-mounted filesystems and the virtual filesystems used by some VPS solutions (that last one got me BTW).\nAdditionally, you also have the Django layer on top of all this, adding complexity. You don't know when Django releases connections (although I am pretty sure someone here can give that answer in detail :) ). But again, if you have multiple concurrent writers, you need a database layer than can do concurrency. Period.\nI solved this issue by switching to postgres. Django makes this very simple for you, even migrating the data is a no-brainer with very little downtime.","Q_Score":3,"Tags":"python,django,sqlite","A_Id":31547325,"CreationDate":"2015-07-21T18:47:00.000","Title":"Django sqlite database is locked","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm working with XLSX files with pivot tables and writing an automated script to parse and extract the data. I have multiple pivot tables per spreadsheet with cost categories, their totals, and their values for each month etc. Any ideas on how to use openpyxl to parse each pivot table?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1122,"Q_Id":31551135,"Users Score":0,"Answer":"This is currently not possible with openpyxl.","Q_Score":0,"Tags":"python,excel,pivot-table,xlsx,openpyxl","A_Id":31556316,"CreationDate":"2015-07-21T23:05:00.000","Title":"Extracting data from excel pivot tables using openpyxl","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have an excel file composed of several sheets. I need to load them as separate dataframes individually. What would be a similar function as pd.read_csv(\"\") for this kind of task?\nP.S. due to the size I cannot copy and paste individual sheets in excel","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":15976,"Q_Id":31582821,"Users Score":0,"Answer":"exFile = ExcelFile(f) #load file f\ndata = ExcelFile.parse(exFile) #this creates a dataframe out of the first sheet in file","Q_Score":4,"Tags":"python,excel,import","A_Id":31582822,"CreationDate":"2015-07-23T09:04:00.000","Title":"How to open an excel file with multiple sheets in pandas?","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a Django application that runs on apache server and uses Sqlite3 db. I want to access this database remotely using a python script that first ssh to the machine and then access the database.\nAfter a lot of search I understand that we cannot access sqlite db remotely. I don't want to download the db folder using ftp and perform the function, instead I want to access it remotely. \nWhat could be the other possible ways to do this?  I don't want to change the database, but am looking for alternate ways to achieve the connection.","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":1226,"Q_Id":31582861,"Users Score":0,"Answer":"Sqlite needs to access the provided file. So this is more of a filesystem question rather than a python one. You have to find a way for sqlite and python to access the remote directory, be it sftp, sshfs, ftp or whatever. It entirely depends on your remote and local OS. Preferably mount the remote subdirectory on your local filesystem.\nYou would not need to make a copy of it although if the file is large you might want to consider that option too.","Q_Score":1,"Tags":"python,django,sqlite","A_Id":31583131,"CreationDate":"2015-07-23T09:07:00.000","Title":"Remotely accessing sqlite3 in Django using a python script","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a Django application that runs on apache server and uses Sqlite3 db. I want to access this database remotely using a python script that first ssh to the machine and then access the database.\nAfter a lot of search I understand that we cannot access sqlite db remotely. I don't want to download the db folder using ftp and perform the function, instead I want to access it remotely. \nWhat could be the other possible ways to do this?  I don't want to change the database, but am looking for alternate ways to achieve the connection.","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":1226,"Q_Id":31582861,"Users Score":3,"Answer":"Leaving aside the question of whether it is sensible to run a production Django installation against sqlite (it really isn't), you seem to have forgotten that, well, you are actually running Django. That means that Django can be the main interface to your data; and therefore you should write code in Django that enables this.\nLuckily, there exists the Django REST Framework that allows you to simply expose your data via HTTP interfaces like GET and POST. That would be a much better solution than accessing it via ssh.","Q_Score":1,"Tags":"python,django,sqlite","A_Id":31583957,"CreationDate":"2015-07-23T09:07:00.000","Title":"Remotely accessing sqlite3 in Django using a python script","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am trying to add users to my Google Analytics account through the API but the code yields this error:\ngoogleapiclient.errors.HttpError: https:\/\/www.googleapis.com\/analytics\/v3\/management\/accounts\/**accountID**\/entityUserLinks?alt=json returned \"Insufficient Permission\">\nI have Admin rights to this account - MANAGE USERS. I can add or delete users through the Google Analytics Interface but not through the API. I have also added the service account email to GA as a user. Scope is set to analytics.manage.users\nThis is the code snippet I am using in my add_user function which has the same code as that provided in the API documentation.\ndef add_user(service):\ntry:\n    service.management().accountUserLinks().insert(\n        accountId='XXXXX',\n           body={\n            'permissions': {\n                'local': [\n                    'EDIT',\n                ]\n            },\n            'userRef': {\n                'email': 'ABC.DEF@gmail.com'\n            }\n        }\n    ).execute()\n\n  except TypeError, error:\n    # Handle errors in constructing a query.\n    print 'There was an error in constructing your query : %s' % error\n\n  return None\nAny help will be appreciated. Thank you!!","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":480,"Q_Id":31621373,"Users Score":0,"Answer":"The problem was I using a service account when I should have been using an installed application. I did not need a service account since I had access using my own credentials.That did the trick for me!","Q_Score":2,"Tags":"api,python-2.7,google-analytics,insert,http-error","A_Id":31866981,"CreationDate":"2015-07-24T23:46:00.000","Title":"Google Analytics Management API - Insert method - Insufficient permissions HTTP 403","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I am trying to access the remote database from one Linux server to another which is connected via LAN.\nbut it is not working.. after some time it will generate an error \n`_mysql_exceptions.OperationalError: (2003, \"Can't connect to MySQL server on '192.168.0.101' (99)\")'\nthis error is random it will raise any time. \neach time create a new db object in all methods.\nand close the connection as well then also why this error raise.\ncan any one please help me to sort out this problem","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":1039,"Q_Id":31645016,"Users Score":0,"Answer":"This issue is due to so many pending request on the remote database.\nSo in this situation MySql closes the connection to the running script.\nto overcome this situation put \ntime.sleep(sec) # here int is a seconds in number that to sleep the script.\nit will solve this issue.. without transferring database to local server or any other administrative task on mysql","Q_Score":2,"Tags":"python,mysql,database-connection,mysql-python,remote-server","A_Id":31717545,"CreationDate":"2015-07-27T04:30:00.000","Title":"python mysql database connection error","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am trying to access the remote database from one Linux server to another which is connected via LAN.\nbut it is not working.. after some time it will generate an error \n`_mysql_exceptions.OperationalError: (2003, \"Can't connect to MySQL server on '192.168.0.101' (99)\")'\nthis error is random it will raise any time. \neach time create a new db object in all methods.\nand close the connection as well then also why this error raise.\ncan any one please help me to sort out this problem","AnswerCount":2,"Available Count":2,"Score":-0.2913126125,"is_accepted":false,"ViewCount":1039,"Q_Id":31645016,"Users Score":-3,"Answer":"My solution was to collect more queries for one commit statement if those were insert queries.","Q_Score":2,"Tags":"python,mysql,database-connection,mysql-python,remote-server","A_Id":41724945,"CreationDate":"2015-07-27T04:30:00.000","Title":"python mysql database connection error","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm trying to embed a bunch of URLs into an Excel file using Python with XLSXWriter's function write_url(), but it gives me the warning of it exceeding the 255 character limit. I think this is happening because it may be using the built-in HYPERLINK Excel function. \nHowever, I found that Apache POI from Java doesn't seem to have that issue. Is it because they directly write it into the cell itself or is there a different reason? Also, is there a workaround in Python that can solve this issue?","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":599,"Q_Id":31661485,"Users Score":0,"Answer":"255 characters in a URL is an Excel 2007+ limitation. Try it in Excel. \nI think the XLS format allowed longer URLs (so perhaps that is the difference). \nAlso XlsxWriter doesn't use the HYPERLINK() function internally (although it is available to the user via the standard interface).","Q_Score":1,"Tags":"java,python,excel,apache-poi,xlsxwriter","A_Id":31662734,"CreationDate":"2015-07-27T19:19:00.000","Title":"Why is Apache POI able to write a hyperlink more than 255 characters but not XLSXWriter?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm trying to embed a bunch of URLs into an Excel file using Python with XLSXWriter's function write_url(), but it gives me the warning of it exceeding the 255 character limit. I think this is happening because it may be using the built-in HYPERLINK Excel function. \nHowever, I found that Apache POI from Java doesn't seem to have that issue. Is it because they directly write it into the cell itself or is there a different reason? Also, is there a workaround in Python that can solve this issue?","AnswerCount":2,"Available Count":2,"Score":0.0996679946,"is_accepted":false,"ViewCount":599,"Q_Id":31661485,"Users Score":1,"Answer":"Obviously the length limitation of a hyperlink address in .xlsx (using Excel 2013) is 2084 characters. Generating a file with a longer address using POI, repairing it with Excel and saving it will yield an address with a length of 2084 characters.\nThe Excel UI and .xls files seem to have a limit of 255 characters, as already mentioned by other commenters.","Q_Score":1,"Tags":"java,python,excel,apache-poi,xlsxwriter","A_Id":36582681,"CreationDate":"2015-07-27T19:19:00.000","Title":"Why is Apache POI able to write a hyperlink more than 255 characters but not XLSXWriter?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"In SQLAlchemy, when I try to query for user by \nrequest.db.query(models.User.password).filter(models.User.email == email).first()\nOf course it works with different DB (SQLite3).\nThe source of the problem is, that the password is \nsqlalchemy.Column(sqlalchemy_utils.types.passwordPasswordType(schemes=['pbkdf2_sha512']), nullable=False)\nI really don't know how to solve it\nI'm using psycopg2","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":84,"Q_Id":31733583,"Users Score":0,"Answer":"Actually it was a problem with Alembic migration, in migration table must be also created with the PasswordType, not String or any other type","Q_Score":0,"Tags":"python,postgresql,sqlalchemy","A_Id":31781831,"CreationDate":"2015-07-30T20:38:00.000","Title":"PasswordType not supported in Postgres","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I need to fetch the data using REST Endpoints(returns JSON file) and load the data(JSON) into Cassandra cluster which is sitting on AWS.\nThis is a migration effort, which involves millions of records. No access to source DB. Only access to REST End points.\n\nWhat are the options I have?\nWhat is the programming language to use?(I am thinking of Python or any scripting language)?\nSince I will have to migrate millions of records, I would like to process the jobs concurrently.\nWhat are the challenges?\n\nThanks for the time and help.\n--GK.","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":129,"Q_Id":31737396,"Users Score":1,"Answer":"Cassandra 2.2.0 give feature to insert and get data as JSON .So you can use that .\nLike for insert json data .\nCREATE TABLE test.example (\n    id int PRIMARY KEY,\n    id2 int,\n    id3 int\n) ;\ncqlsh >  INSERT INTO example JSON '{\"id\":10,\"id2\":10,\"id3\":10}' ;\nFor Select data as Json :\ncqlsh >  SELECT json  * FROM  example;\n [json]\n{\"id\": 10, \"id2\": 10, \"id3\": 10}","Q_Score":1,"Tags":"python,json,rest,cassandra,data-migration","A_Id":31738908,"CreationDate":"2015-07-31T02:59:00.000","Title":"Data Migration to Cassandra using REST End points","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":1,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm using a session with autocommit=True and expire_on_commit=False. I use the session to get an object A with a foreign key that points to an object B. I then call session.expunge(a.b); session.expunge(a).\nLater, when trying to read the value of b.some_datetime, SQLAlchemy raises a DetachedInstanceError. No attribute has been configured for lazy-loading. The error happens randomly.\nHow is this possible? I assumed that all scalar attributes would be eagerly loaded and available after the object is expunged. \nFor what it's worth, the objects get expunged so they can be used in another thread, after all interactions with the database are over.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":573,"Q_Id":31746829,"Users Score":1,"Answer":"One of the mapped class's fields had an onupdate attribute, which caused it to expire whenever the object is changed. \nThe solution is to call session.refresh(myobj) between the flush and the call to session.expunge().","Q_Score":1,"Tags":"python,sqlalchemy","A_Id":31967070,"CreationDate":"2015-07-31T12:59:00.000","Title":"DetachedInstanceError: SQLAlchemy wants to refresh the DateTime attribute of an expunged instance","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a question about SQL, especially SQLite3. I have two tables, let's name them main_table and temp_table. These tables are based on the same relational schema so they have the same columns but different rows (values).\nNow what I want to do: \nFor each row of the main_table I want to replace it if there is a row in a temp_table with the same ID. Otherwise I want to keep the old row in the table.\nI was thinking about using some joins but it does not provides the thing I want.\nWould you give me an advice?\nEDIT: ADITIONAL INFO:\nI would like to avoid writing all columns because those tables conains tens of attributes and since I have to update all columns it couldn't be necessary to write out all of them.","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":334,"Q_Id":31748654,"Users Score":0,"Answer":"You have 2 approaches:\n\nUpdate current rows inside main_table with data from temp_table. The relation will be based by ID.\nAdd a column to temp_table to mark all rows that have to be transferred to main_table or add aditional table to store IDs that have to be transferred. Then delete all rows that have to be transferred from table main_table and insert corresponding rows from temp_table using column with marks or new table.","Q_Score":1,"Tags":"python,sql,sqlite,sql-update","A_Id":31748808,"CreationDate":"2015-07-31T14:29:00.000","Title":"SQL - update main table using temp table","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm writing an application for topology optimization within the ABAQUS PDE. As I have quite some iterations, in each of which FEM is performed, a lot of data is written to the system -- and thus a lot of time is lost on I\/O.\nIs it possible to limit the amount of information that gets written into the ODB file?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":571,"Q_Id":31755078,"Users Score":1,"Answer":"Indeed it's possible. You should check the frequency of your output in the field output section inside the step module. You can configure it in terms of step intervals of time, number of increments, exact amount of outputs, etc.\nIf you're running your analysis from a inp file, you can add FREQ = X after the *STEP command. This way Abaqus will write on the ODB file every X increments.","Q_Score":0,"Tags":"python,abaqus,odb","A_Id":31808849,"CreationDate":"2015-07-31T20:57:00.000","Title":"Limited ODB output in ABAQUS","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a web application that uses flask and mongodb. I recently downloaded a clone of it from github onto a new Linux machine, then proceeded to run it. It starts and runs without any errors, but when I use a function that needs access to the database, I get this error:\n\nFile \"\/usr\/local\/lib\/python2.7\/dist-packages\/pymongo\/cursor.py\", line 533,  in __ getitem__\n       raise IndexError(\"no such item for Cursor instance\")\n   IndexError: no such item for Cursor instance\n\nThis isn't happening on any of the other computers running this same application. Does anybody know what's going on?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1948,"Q_Id":31755276,"Users Score":0,"Answer":"Well, it ended up being an issue with the String specifying the working directory. Once it was resolved I was able to connect to the database.","Q_Score":0,"Tags":"python,mongodb,flask,pymongo","A_Id":31865825,"CreationDate":"2015-07-31T21:14:00.000","Title":"Cursor Instance Error when connecting to mongo db?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a string of categories stored in a table. The categories are separated by a ',', so that I can turn the string into a list of strings as \ncategory_string.split(',')\nI now want to select all elements of a sql table which have one of the the following categories [catergory1, catagory2]. \nI have many such comparisons and the list of categories to compare with is not necessarily 2 elements long, so I would need a comparison of elements of two lists. I know that list comparisons are done as \nTable.categories.in_(category_list)\nin sql-alchemy but I also need to convert a table string element in a list and do the comparison of list elements.\nany ideas?\nthanks\ncarl","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":1109,"Q_Id":31759266,"Users Score":1,"Answer":"I figured it out. Basically one needs to use the like command and or_(\ncarl","Q_Score":0,"Tags":"python,sqlalchemy","A_Id":31759707,"CreationDate":"2015-08-01T07:05:00.000","Title":"sql alchemy filter: string split and comparison of list elements","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Usually the workflow I have is as follows:\n\nPerform SQL query on database, \nLoad it into memory\nTransform data based on logic foo()\nInsert the transformed data to a table in a database.\n\nHow should unit test be written for this kind of workflow? I'm really new to testing.\nAnyway, I'm using Python 3.4.","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":538,"Q_Id":31769814,"Users Score":0,"Answer":"One way to test this kind of workflow is by using a special database just for testing. The test database mirrors the structure of your production database, but is otherwise completely empty (i.e. no data is in the tables). The routine is then as follows\n\nConnect to the test database (and and maybe reload its structure)\nFor every testcase, do the following:\n\n\nLoad the minimal set of data into the database necessary to test your routine\nRun your function to test and grab its output (if any)\nPerform some tests to see that your function did what you expected it to do.\nDrop all data from the database before the next test case runs\n\nAfter all your tests are done, disconnect from the database","Q_Score":1,"Tags":"python,unit-testing,tdd,integration-testing","A_Id":31769998,"CreationDate":"2015-08-02T08:04:00.000","Title":"How should unit test be written for data transformation?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Say you have a column that contains the values for the year, month and date. Is it possible to get just the year? In particular I have\nALTER TABLE pmk_pp_disturbances.disturbances_natural ADD COLUMN sdate timestamp without time zone;\nand want just the 2004 from 2004-08-10 05:00:00. Can this be done with Postgres or must a script parse the string? By the way, any rules as to when to \"let the database do the work\" vs. let the script running on the local computer do the work? I once heard querying databases is slower than the rest of the program written in C\/C++, generally speaking.","AnswerCount":3,"Available Count":1,"Score":-0.1973753202,"is_accepted":false,"ViewCount":38,"Q_Id":31820655,"Users Score":-3,"Answer":"I think no. You're forced to read the entire value of a column. You can divide the date in few columns, one for the year, another for the month, etc. , or store the date on an integer format if you want an aggressive space optimization. But it will doing the database worst about scalability and modifications.\nThe databases are slow, you must assume it, but they offer hardest things to do with C\/C++.\nIf you think make a game and save your 'save game' on SQL forget it. Use it if you're doing a back-end server or a management application, tool, etc.","Q_Score":0,"Tags":"python,postgresql","A_Id":31820790,"CreationDate":"2015-08-04T22:46:00.000","Title":"Can Postgres be used to take only the portion of a date from a field?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have an SQLAlchemy DB column which is of type datetime: \ntype(<my_object>) --> sqlalchemy.orm.attributes.InstrumentedAttribute\nHow do I reach the actual date in order to filter the DB by weekday() ?","AnswerCount":1,"Available Count":1,"Score":1.0,"is_accepted":false,"ViewCount":3875,"Q_Id":31841054,"Users Score":6,"Answer":"I got it:\nfrom sqlalchemy import func\n(func.extract(<my_object>, 'dow') == some_day)\ndow stands for 'day of week'\nThe extract is an SQLAlchemy function allowing the extraction of any field from the column object.","Q_Score":5,"Tags":"python,sqlalchemy,flask-sqlalchemy","A_Id":31857049,"CreationDate":"2015-08-05T19:19:00.000","Title":"Extract a weekday() from an SQLAlchemy InstrumentedAttribute (Column type is datetime)","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have several thousand excel documents. All of these documents are 95% the same in terms of column headings. However, since they are not 100% identical, I cannot simply merge them together and upload it into a database without messing up the data. \nWould anyone happen to have a library or an example that they've ran into that would help?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":177,"Q_Id":31842810,"Users Score":0,"Answer":"If a large proportion of them are similar, and this is a one-off operation it may be worth your while coding the solution for the majority and handling the other documents (or groups of them if they are similar) separately. If using Python to do this you could simply build a dynamic query where the columns that are present in a given excel sheet are built into the INSERT statements. Of course, this assumes that your database table allows for NULLs or that a default value is present on the columns that aren't in a given document.","Q_Score":0,"Tags":"python,excel,pandas,xlwt","A_Id":31842901,"CreationDate":"2015-08-05T21:04:00.000","Title":"Python merge excel documents with dynamic columns","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"This will be a bit of a lengthly post, sorry in advance. I have a bit of experience using MongoDB (been awhile) and I'm so-so with python, but I have a big project and I would like some feedback before spending lots of time coding.\nThe project involves creating a gallery where individual presentation slides (from apple keynote '09) can be selected and parsed together into a presentation. This way a user with a few thousand slides can use this program to create a new presentation by mixing and matching old slides, rather than having to open up each presentation and copy-paste all of the desired slides into a new presentation manually.\nWithin the program there is a master gallery that contains all the slides. Each slide may be selected and assigned searchable tags. New \"groups\" of slides may be formed, where all slides with a specific set of tags are added to the group automatically. In addition, individual slides can be dragged from the master gallery and dropped into a user-created group.\nThere is a folder with preview images for each slide, here is why I believe I need MongoDB: By having a database where each slide is a document that contains the filename of the slide, the filename of the preview thumbnail of the slide, and an array containing searchable tag words, one will be able to query specific sets of slides very quickly. The query will return an array of matching slides which can than be looped through to add each slide thumbnail to the GUI gallery. The user-created \"groups\" can be individual collections, where a collection is created when a group is created, slides are added\/removed from the collection as needed, and the collection can be destroyed when the group is deleted. This also will allow permanent storage as the database and its collections will persist between opening and closing the program.\nMy question is, will I be able to use MongoDB (through pyMongo) to do the following with decent performance:\n-Create and delete collections as needed\n-Copy and delete specific documents from a master collection into newly created collections\n-Store an array of searchable tags in string format in a dynamic array associated with each document\n-Query slides within a collection based on a single tag word stored in an array within each document\n-Maintain the database between system shutdowns and opening \/ closing the program.\nThanks!","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":70,"Q_Id":31862957,"Users Score":0,"Answer":"Your post's points and questions are quoted below. My comments follow each quote.\n\n\nBy having a database where each slide is a document that contains the filename of the slide, the filename of the preview thumbnail of the\n  slide, and an array containing searchable tag words, one will be able\n  to query specific sets of slides very quickly.\n\nSounds good. I'm assuming that the slides are in one collection.\n\nThe user-created \"groups\" can be individual collections, where a\n  collection is created when a group is created, slides are\n  added\/removed from the collection as needed, and the collection can be\n  destroyed when the group is deleted.\n\nI suggest that you do not create a collection for each group. You may end up with hundreds or thousands of collections to represent \"groups\". This could bite you down the road if you decide you want to introduce Sharding (which may only be done on a collection). Consider creating one collection just for \"groups\" that will contain the unique user id to which the group is associated.\n\n[Will I be able to use MongoDB, with decent performance, to] create\n  and delete collections as needed?\n\nConstantly creating and deleting collections is not good design. You probably do not need to do this. If you have any familiarity with RDBMS then a collection is analogous to a table. Would you keep creating dozens\/hundreds\/thousands of tables on the fly? Probably not.\n\n[Will I be able to use MongoDB, with decent performance, to] copy and\n  delete specific documents from a master collection into newly created\n  collections?\n\nYes, it is possible to take data from one collection and save it to another collection. Deleting documents is also quite easy and performant. (Indexing is your friend.)\n\n[Will I be able to use MongoDB, with decent performance, to] store an\n  array of searchable tags in string format in a dynamic array\n  associated with each document?\n\nYes. MongoDB is very good at this.\n\n[Will I be able to use MongoDB, with decent performance, to] query\n  slides within a collection based on a single tag word stored in an\n  array within each document?\n\nYes. Decent performance will depend on the size of your collection and, more importantly, the existence of relevant indexes.\n\n[Will I be able to use MongoDB, with decent performance, to] maintain\n  the database between system shutdowns and opening \/ closing the\n  program?\n\nI'm assuming that you are referring to replication and failover. If so, yes, MongoDB supports this quite well.","Q_Score":0,"Tags":"python,mongodb,pymongo,database","A_Id":31867932,"CreationDate":"2015-08-06T18:14:00.000","Title":"Will I be able to implement this design using MongoDB (via pyMongo)","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"How can I store python 'list' values into MySQL and access it later from the same database like a normal list?\nI tried storing the list as a varchar type and it did store it. However, while accessing the data from MySQL I couldn't access the same stored value as a list, but it instead it acts as a string. So, accessing the list with index was no longer possible. Is it perhaps easier to store some data in the form of sets datatype? I see the MySQL datatype 'set' but i'm unable to use it from python. When I try to store set from python into MySQL, it throws the following error: 'MySQLConverter' object has no attribute '_set_to_mysql'. Any help is appreciated\nP.S. I have to store co-ordinate of an image within the list along with the image number. So, it is going to be in the form [1,157,421]","AnswerCount":2,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":5462,"Q_Id":31879337,"Users Score":2,"Answer":"Are you using an ORM like SQLAlchemy?\nAnyway, to answer your question directly, you can use json or pickle to convert your list to a string and store that. Then to get it back, you can parse it (as JSON or a pickle) and get the list back.\nHowever, if your list is always a 3 point coordinate, I'd recommend making separate x, y, and z columns in your table. You could easily write functions to store a list in the correct columns and convert the columns to a list, if you need that.","Q_Score":3,"Tags":"python,mysql","A_Id":31879445,"CreationDate":"2015-08-07T13:47:00.000","Title":"storing python list into mysql and accessing it","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Let's say I have the following Microsoft Access Database: random.mdb.\nThe main thing I'm trying to achieve is to use read_sql() from pandas so that I can work with the data I have using python. How would I approach this? Is there a way to convert the Microsoft Access database to a SQL database... to eventually pass in to pandas (all in python)?","AnswerCount":3,"Available Count":1,"Score":0.0665680765,"is_accepted":false,"ViewCount":2680,"Q_Id":31949312,"Users Score":1,"Answer":"use sql server import export module to convert, but you will need table structure ready in sql server or there may be many other utilities","Q_Score":0,"Tags":"python,sql,sql-server,ms-access,pandas","A_Id":31949357,"CreationDate":"2015-08-11T18:26:00.000","Title":"How to convert a Microsoft Access Database to a SQL database (and then open it with pandas)?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"So I've been trying to solve this for a while now and can't seem to find a way to speed up performance of inserts with Django despite the many suggestions and tips found on StackOverflow and many Google searches.\nSo basically I need to insert a LOT of data records (~2 million) through Django into my MySQL DB, each record entry being a whopping 180KB. I've scaled my testing down to 2,000 inserts yet still cant get the running time down to a reasonable amount. 2,000 inserts currently takes approximately 120 seconds.\nSo I've tried ALL of the following (and many combinations of each) to no avail:\n\n\"Classic\" Django ORM create model and .save()\nSingle transaction (transaction.atomic())\nBulk_create\nRaw SQL INSERT in for loop\nRaw SQL \"executemany\" (multiple value inserts in one query)\nSetting SQL attributes like \"SET FOREIGN_KEY_CHECKS=0\"\nSQL BEGIN ... COMMIT\nDividing the mass insert into smaller batches\n\nApologizes if I forgot to list something, but I've just tried so many different things at this point, I can't even keep track ahah.\nWould greatly appreciate a little help here in speeding up performance from someone who maybe had to perform a similar task with Django database insertions.\nPlease let me know if I've left out any necessary information!","AnswerCount":3,"Available Count":3,"Score":0.0665680765,"is_accepted":false,"ViewCount":2130,"Q_Id":31977138,"Users Score":1,"Answer":"This is out of django's scope really. Django just translates your python into on INSERT INTO statement. For most performance on the django layer skipping it entirely (by doing sql raw) might be best, even though python processing is pretty fast compared to IO of a sql-database.\nYou should rather focus on the database. I'm a postgres person, so I don't know what config options mysql has, but there is probably some fine tuning available.\nIf you have done that and there is still no increase you should consider using SSDs, SSDs in a RAID 0, or even a db in memory, to skip IO times.\nSharding may be a solution too - splitting the tasks and executing them in parallel.\nIf the inserts however are not time critical, i.e. can be done whenever, but shouldn't block the page from loading, I recommend celery.\nThere you can queue a task to be executed whenever there is time - asynchronously.","Q_Score":2,"Tags":"python,mysql,django,database,insert","A_Id":31977326,"CreationDate":"2015-08-12T23:33:00.000","Title":"Increasing INSERT Performance in Django For Many Records of HUGE Data","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"So I've been trying to solve this for a while now and can't seem to find a way to speed up performance of inserts with Django despite the many suggestions and tips found on StackOverflow and many Google searches.\nSo basically I need to insert a LOT of data records (~2 million) through Django into my MySQL DB, each record entry being a whopping 180KB. I've scaled my testing down to 2,000 inserts yet still cant get the running time down to a reasonable amount. 2,000 inserts currently takes approximately 120 seconds.\nSo I've tried ALL of the following (and many combinations of each) to no avail:\n\n\"Classic\" Django ORM create model and .save()\nSingle transaction (transaction.atomic())\nBulk_create\nRaw SQL INSERT in for loop\nRaw SQL \"executemany\" (multiple value inserts in one query)\nSetting SQL attributes like \"SET FOREIGN_KEY_CHECKS=0\"\nSQL BEGIN ... COMMIT\nDividing the mass insert into smaller batches\n\nApologizes if I forgot to list something, but I've just tried so many different things at this point, I can't even keep track ahah.\nWould greatly appreciate a little help here in speeding up performance from someone who maybe had to perform a similar task with Django database insertions.\nPlease let me know if I've left out any necessary information!","AnswerCount":3,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":2130,"Q_Id":31977138,"Users Score":0,"Answer":"You can also try to delete any index on the tables (and any other constraint), the recreate the indexes and constraints after the insert.\nUpdating indexes and checking constraints can slow down every insert.","Q_Score":2,"Tags":"python,mysql,django,database,insert","A_Id":31977679,"CreationDate":"2015-08-12T23:33:00.000","Title":"Increasing INSERT Performance in Django For Many Records of HUGE Data","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"So I've been trying to solve this for a while now and can't seem to find a way to speed up performance of inserts with Django despite the many suggestions and tips found on StackOverflow and many Google searches.\nSo basically I need to insert a LOT of data records (~2 million) through Django into my MySQL DB, each record entry being a whopping 180KB. I've scaled my testing down to 2,000 inserts yet still cant get the running time down to a reasonable amount. 2,000 inserts currently takes approximately 120 seconds.\nSo I've tried ALL of the following (and many combinations of each) to no avail:\n\n\"Classic\" Django ORM create model and .save()\nSingle transaction (transaction.atomic())\nBulk_create\nRaw SQL INSERT in for loop\nRaw SQL \"executemany\" (multiple value inserts in one query)\nSetting SQL attributes like \"SET FOREIGN_KEY_CHECKS=0\"\nSQL BEGIN ... COMMIT\nDividing the mass insert into smaller batches\n\nApologizes if I forgot to list something, but I've just tried so many different things at this point, I can't even keep track ahah.\nWould greatly appreciate a little help here in speeding up performance from someone who maybe had to perform a similar task with Django database insertions.\nPlease let me know if I've left out any necessary information!","AnswerCount":3,"Available Count":3,"Score":1.2,"is_accepted":true,"ViewCount":2130,"Q_Id":31977138,"Users Score":0,"Answer":"So I found that editing the mysql \/etc\/mysql\/my.cnf file and configuring some of the InnoDB settings significantly increased performance.\nI set:\n\ninnodb_buffer_pool_size = 9000M 75% of your system RAM\ninnodb_log_file_size = 2000M    20%-30% of the above value\n\nrestarted the mysql server and this cut down 50 inserts from ~3 seconds to ~0.8 seconds. Not too bad!\nNow I'm noticing the inserts are gradually taking longer longer for big data amounts. 50 inserts starts at about 0.8 seconds but after 100 or so batches the average is up to 1.4 seconds and continues increasing.\nWill report back if solved.","Q_Score":2,"Tags":"python,mysql,django,database,insert","A_Id":32000816,"CreationDate":"2015-08-12T23:33:00.000","Title":"Increasing INSERT Performance in Django For Many Records of HUGE Data","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"What is the difference between executing raw SQL on the SQLAlchemy engine and the session? Specifically against a MSSQL database.\n\nengine.execute('DELETE FROM MyTable WHERE MyId IN(1, 2, 3)')\n\nversus\n\nsession.execute('DELETE FROM MyTable WHERE MyId IN(1, 2, 3)')\n\nI've noticed that executing the SQL on the session, cause MSSQL to 'hang'.\nPerhaps someone has an idea on how these two executions are different, or perhaps someone can point me where to further investigate.","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":1516,"Q_Id":32020502,"Users Score":1,"Answer":"The reason why MSSQL Server was hanging, was not because of the difference between calling execute on the engine or the session, but because a delete was being called on the table, without a commit, and then a subsequent read.","Q_Score":1,"Tags":"python,sql-server,sqlalchemy","A_Id":32419439,"CreationDate":"2015-08-15T01:02:00.000","Title":"Executing raw SQL on the SQLAlchemy engine versus a session","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am new to Dynamodb and have a requirement of grouping the documents on the basis of a certain condition before performing other operations.\nFrom what i could read on the internet, i figured out that there is no direct way to group dynamodb documents.\nCan anyone confirm if thats true of help out with a solution if that is not the case?","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":582,"Q_Id":32044338,"Users Score":1,"Answer":"Amazon DynamoDB is a NoSQL database, so you won't find standard SQL capabilities like group by and average().\nThere is, however, the ability to filter results, so you will only receive results that match your criteria. It is then the responsibility of the calling app to perform grouping and aggregations.\nIt's really a trade-off between the flexibility of SQL and the sheer speed of NoSQL. Plus, in the case of DynamoDB, the benefit of data being stored in three facilities to improve durability and availability.","Q_Score":0,"Tags":"python,amazon-web-services,amazon-dynamodb","A_Id":32045125,"CreationDate":"2015-08-17T06:52:00.000","Title":"Does Dynamodb support Groupby\/ Aggregations directly?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am writing a script to compare the records in a database in my DynamoDB with record in another database in EC2. \nI will appreciate any help with iterating through the table in Python.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1953,"Q_Id":32073427,"Users Score":0,"Answer":"I came across the same need when I query DynamoDB from an AWS Lambda in Python and expected the dataset to be over 128MB of memory limit. If I can't iterate through, I'll have to pay extra bucks to AWS. Unfortunately, it seems there is no way to do so except converting the query response to an iterator (which wouldn't save memory at all).","Q_Score":1,"Tags":"python,amazon-web-services,amazon-dynamodb","A_Id":48822032,"CreationDate":"2015-08-18T13:10:00.000","Title":"How to iterate through a table in AWS DynamoDB?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I created an Excel spreadsheet using Pandas and xlsxwriter, which has all the data in the right rows and columns. However, the formatting in xlsxwriter is pretty basic, so I want to solve this problem by writing my Pandas spreadsheet on top of a template spreadsheet with Pyxl.\nFirst, however, I need to get Pyxl to only import data up to the first blank row, and to get rid of the column headings. This way I could write my Excel data from the xlsxwriter output to the template.\nI have no clue how to go about this and can't find it here or in the docs. Any ideas? \nHow about if I want to read data from the first column after the first blank column? (I can think of a workaround for this, but it would help if I knew how)","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":256,"Q_Id":32077627,"Users Score":1,"Answer":"To be honest I'd be tempted to suggest you use openpyxl all the way if there is something that xlsxwriter doesn't do, though I think that it's formatting options are pretty extensive. The most recent version of openpyxl is as fast as xlsxwriter if lxml is installed.\nHowever, it's worth noting that Pandas has tended to ship with an older version of openpyxl because we changed the style API.\nOtherwise you can use max_row to get the highest row but this won't check for an empty row.","Q_Score":1,"Tags":"python,excel,openpyxl","A_Id":32119557,"CreationDate":"2015-08-18T16:17:00.000","Title":"Use Pyxl to read Excel spreadsheet data up to a certain row","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm working on a distributed system where one process is controlling a hardware piece and I want it to be running as a service. My app is Django + Twisted based, so Twisted maintains the main loop and I access the database (SQLite) through Django, the entry point being a Django Management Command.\nOn the other hand, for user interface, I am writing a web application on the same Django project on the same database (also using Crossbar as websockets and WAMP server). This is a second Django process accessing the same database.\nI'm looking for some validation here. Is anything fundamentally wrong to this approach? I'm particularly scared of issues with database (two different processes accessing it via Django ORM).","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":143,"Q_Id":32213796,"Users Score":1,"Answer":"No there is nothing inherently wrong with that approach. We currently use a similar approach for a lot of our work.","Q_Score":0,"Tags":"python,django,sqlite,twisted,daemon","A_Id":32235411,"CreationDate":"2015-08-25T20:49:00.000","Title":"Twisted + Django as a daemon process plus Django + Apache","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I made a sheet with a graph using python and openpyxl.    Later on in the code I add some extra cells that I would also like to see in the graph.   Is there a way that I can change the range of cell that the graph is using, or maybe there is another library that lets me do this?\nExample:\nmy graph initially uses columns A1:B10, then I want to update it to use A1:D10\nCurrently I am deleting the sheet, and recreating it, writing back the values and making the graph again,  the problem is that this is a big process that takes days, and there will be a point that rewriting the sheet will take some time.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1178,"Q_Id":32254733,"Users Score":0,"Answer":"At the moment it is not possible to preserve charts in existing files. With rewrite in version 2.3 of openpyxl the groundwork has been laid that will make this possible. When it happens will depend on the resources available to do the work. Pull requests gladly accepted.\nIn the meantime you might be able find a workaround by writing macros to create the charts for you because macros are preserved. A bit clumsy but should work.\nMake sure that you are using version 2.3 or higher when working on charts as the API has changed slightly.","Q_Score":0,"Tags":"python,graph,openpyxl","A_Id":32256294,"CreationDate":"2015-08-27T16:20:00.000","Title":"Python Excel, Is it possible to update values of a created graph?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Anybody know of any currently worked on projects that wire up MongoDB to the most recent version of Django? mongoengine's Django module github hasn't been updated in 2 years (and I don't know if I can use its regular module with Django) and django-nonrel uses Django 1.6. Anybody tried using django-nonrel with Django 1.8?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":210,"Q_Id":32260031,"Users Score":0,"Answer":"If you are using mongoengine, there is no need of django-nonrel.You can directly use django latest versions.","Q_Score":0,"Tags":"python,django,mongodb","A_Id":32260215,"CreationDate":"2015-08-27T21:50:00.000","Title":"Django: MongoDB engine for Django 1.8","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"My original purpose was to bulk insert into my db\nI tried pyodbc, sqlalchemy and ceodbc to do this with executemany function but my dba checked and they execute each row individually.\nhis solution was to run procedure that recieve table (user defined data type) as parameter and load it into the real table.\nThe problem is no library seem to support that (or at least no example on the internet).\nSo my question is anyone try bulk insert before or know how to pass user data defined type to stored procedure?\nEDIT\nI also tried bulk insert query but the problem it requires local path or share and it will not happend because organizition limits","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":826,"Q_Id":32297244,"Users Score":0,"Answer":"Sqlalchemy bulk operations doesn't really inserts a bulk. It's written in the docs.\nAnd we've checked it  with our dba.\nThank you we'll try the xml.","Q_Score":2,"Tags":"sql-server,python-2.7,sqlalchemy,pyodbc,pymssql","A_Id":32305711,"CreationDate":"2015-08-30T13:51:00.000","Title":"Python mssql passing procedure user defined data type as parameter","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I would like to read a column of date from SQL database. However, the format of the date in the database is something like 27-Jan-13 which is day-month-year. When I read this column using peewee DateField it is read in a format which cannot be compared later using datetime.date.\nCan anyone help me solve the issue?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":366,"Q_Id":32303115,"Users Score":0,"Answer":"You need to store the data in the database using the format %Y-%m-%d. When you extract the data you can present it in any format you like, but to ensure the data is sorted correctly (and recognized by SQLite as a date) you must use the %Y-%m-%d format (or unix timestamps if you prefer that way).","Q_Score":0,"Tags":"python,peewee,datefield","A_Id":32429590,"CreationDate":"2015-08-31T02:14:00.000","Title":"Reading DateField with specific format from SQL database using peewee","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I know there are various ETL tools available to export data from oracle to MongoDB but i wish to use python as intermediate to perform this. Please can anyone guide me how to proceed with this?\nRequirement:\nInitially i want to add all the records from oracle to mongoDB and after that I want to insert only newly inserted records from Oracle into MongoDB.\nAppreciate any kind of help.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":889,"Q_Id":32305131,"Users Score":0,"Answer":"To answer your question directly:\n 1. Connect to Oracle\n 2. Fetch all the delta data by timestamp or id (first time is all records)\n 3. Transform the data to json\n 4. Write the json to mongo with pymongo\n 5. Save the maximum timestamp \/ id for next iteration\nKeep in mind that you should think about the data model considerations and usually relational DB (like Oracle) and document DB (like mongo) will have different data model.","Q_Score":1,"Tags":"python,oracle,mongodb","A_Id":32305243,"CreationDate":"2015-08-31T06:29:00.000","Title":"Export from Oracle to MongoDB using python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"We are migrating some data from our production database and would like to archive most of this data in the Cloud Datastore.\nEventually we would move all our data there, however initially focusing on the archived data as a test.\nOur language of choice is Python, and have been able to transfer data from mysql to the datastore row by row.  \nWe have approximately 120 million rows to transfer and at a one row at a time method will take a very long time.\nHas anyone found some documentation or examples on how to bulk insert data into cloud datastore using python?\nAny comments, suggestions is appreciated thank you in advanced.","AnswerCount":3,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":3726,"Q_Id":32316088,"Users Score":7,"Answer":"There is no \"bulk-loading\" feature for Cloud Datastore that I know of today, so if you're expecting something like \"upload a file with all your data and it'll appear in Datastore\", I don't think you'll find anything.\nYou could always write a quick script using a local queue that parallelizes the work.\nThe basic gist would be:\n\nQueuing script pulls data out of your MySQL instance and puts it on a queue.\n(Many) Workers pull from this queue, and try to write the item to Datastore.\nOn failure, push the item back on the queue.\n\nDatastore is massively parallelizable, so if you can write a script that will send off thousands of writes per second, it should work just fine. Further, your big bottleneck here will be network IO (after you send a request, you have to wait a bit to get a response), so lots of threads should get a pretty good overall write rate. However, it'll be up to you to make sure you split the work up appropriately among those threads.\n\nNow, that said, you should investigate whether Cloud Datastore is the right fit for your data and durability\/availability needs. If you're taking 120m rows and loading it into Cloud Datastore for key-value style querying (aka, you have a key and an unindexed value property which is just JSON data), then this might make sense, but loading your data will cost you ~$70 in this case (120m * $0.06\/100k).\nIf you have properties (which will be indexed by default), this cost goes up substantially.\nThe cost of operations is $0.06 per 100k, but a single \"write\" may contain several \"operations\". For example, let's assume you have 120m rows in a table that has 5 columns (which equates to one Kind with 5 properties).\nA single \"new entity write\" is equivalent to:\n\n+ 2 (1 x 2 write ops fixed cost per new entity)\n+ 10 (5 x 2 write ops per indexed property)\n= 12 \"operations\" per entity.\n\nSo your actual cost to load this data is:\n120m entities * 12 ops\/entity * ($0.06\/100k ops) = $864.00","Q_Score":6,"Tags":"python,mysql,google-cloud-datastore","A_Id":33367328,"CreationDate":"2015-08-31T16:47:00.000","Title":"Is it possible to Bulk Insert using Google Cloud Datastore","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I am doing a mini-project on Web-Crawler+Search-Engine. I already know how to scrape data using Scrapy framework. Now I want to do indexing. For that I figured out Python dictionary is the best option for me. I want mapping to be like name\/title of an object (a string) -> the object itself (a Python object).\nNow the problem is that I don't know how to store dynamic dict in MySQL database and I definitely want to store this dict as it is!\nSome commands on how to go about doing that would be very much appreciated!","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":339,"Q_Id":32325390,"Users Score":1,"Answer":"If you want to store dynamic data in a database, here are a few options.  It really depends on what you need out of this.\nFirst, you could go with a NoSQL solution, like MongoDB.  NoSQL allows you to store unstructured data in a database without an explicit data schema.  It's a pretty big topic, with far better guides\/information than I could provide you.  NoSQL may not be suited to the rest of your project, though.\nSecond, if possible, you could switch to PostgreSQL, and use it's HSTORE column (unavailable in MySQL).  The HSTORE column is designed to store a bunch of Key\/Value pairs.  This column types supports BTREE, GIST, GIN, and HASH indexing.  You're going to need to ensure you're familiar with PostgreSQL, and how it differs from MySQL.  Some of your other SQL may no longer work as you'd expect.\nThird, you can serialize the data, then store the serialized entity.  Both json and pickle come to mind.  The viability and reliability of this will of course depend on how complicated your dictionaries are.  Serializing data, especially with pickle can be dangerous, so ensure you're familiar with how it works from a security perspective.  \nFourth, use an \"Entity-Attribute-Value\" table.  This mimics a dictionaries \"Key\/Value\" pairing.  You, essentially, create a new table with three columns of \"Related_Object_ID\", \"Attribute\", \"Value\".  You lose a lot of object metadata you'd normally get in a table, and SQL queries can become much more complicated. \nAny of these options can be a double edged sword.  Make sure you've read up on the downfalls of whatever option you want to go with, or, in looking into the options more, perhaps you'll find something that better suits you and your project.","Q_Score":1,"Tags":"python,mysql,dictionary,scrapy","A_Id":32334348,"CreationDate":"2015-09-01T06:58:00.000","Title":"How to store a dynamic python dictionary in MySQL database?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm working on aws S3 multipart upload, And I am facing following issue.\nBasically I am uploading a file chunk by chunk to s3, And during the time if any write happens to the file locally, I would like to reflect that change to the s3 object which is in current upload process.\nHere is the procedure that I am following,\n\nInitiate multipart upload operation.\nupload the parts one by one [5 mb chunk size.] [do not complete that   operation yet.]\nDuring the time if a write goes to that file, [assuming i have the details for the write [offset, no_bytes_written] ].\nI will calculate the part no for that write happen locally, And read that chunk from the s3 uploaded object.\nRead the same chunk from the local file and write to read part from s3.\nUpload the same part to s3 object.\nThis will be an a-sync operation. I will complete the multipart operation at the end.\n\nI am facing an issue in reading the uploaded part that is in multipart uploading process. Is there any API available for the same?\nAny help would be greatly appreciated.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1069,"Q_Id":32348812,"Users Score":3,"Answer":"There is no API in S3 to retrieve a part of a multi-part upload.  You can list the parts but I don't believe there is any way to retrieve an individual part once it has been uploaded.\nYou can re-upload a part.  S3 will just throw away the previous part and use the new one in it's place.  So, if you had the old and new versions of the file locally and were keeping track of the parts yourself, I suppose you could, in theory, replace individual parts that had been modified after the multipart upload was initiated.   However, it seems to me that this would be a very complicated and error-prone process.  What if the change made to a file was to add several MB's of data to it?  Wouldn't that change  your boundaries?  Would that potentially affect other parts, as well?\nI'm not saying it can't be done but I am saying it seems complicated and would require you to do a lot of bookkeeping on the client side.","Q_Score":1,"Tags":"python,amazon-web-services,file-upload,amazon-s3,boto","A_Id":32352584,"CreationDate":"2015-09-02T08:59:00.000","Title":"How to read a part of amazon s3 key, assuming that \"multipart upload complete\" is yet to happen for that key?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":1,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am trying to migrate django models from sqlite to postgres. I tested it locally and now trying to do the samething with remote database. I dumped the data first then started the application which created the tables in remote database.\nFinally I am trying to loaddata but it looks like hanged and no errors.\nIs there a way to get verbose ? Or I am not sure how to diagnose this issue. It just 199M size file and when I test locally loaddata works in few minutes.","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":353,"Q_Id":32362384,"Users Score":1,"Answer":"I had no solution, so I ran loaddata locally and used pg_dump and ran the dump with pqsl -f and restored the data.","Q_Score":2,"Tags":"python,django,django-south","A_Id":32385965,"CreationDate":"2015-09-02T20:19:00.000","Title":"manage.py loaddata hangs when loading to remote postgres","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Is it bad practice to have Django perform migrations on a predominantly Rails web app?\nWe have a RoR app and have moved a few of the requirements out to Python. One of the devs here has suggested creating some of the latest database migration using Django and my gut says this is a bad idea.\nI haven't found any solid statements one way or the other after scouring the web and am hoping someone can provide some facts of why this is crazy (or why I should keep calm).\ndatabase: Postgres\nhosting: heroku\nskills level: junior","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":254,"Q_Id":32450413,"Users Score":1,"Answer":"I think you need to maintain migrations at one system (in this case, Rails), because it will be difficult to check migrations between two different apps. What you'll do if you'll haven't access to another app?\nBut you can store something like db\/schema.rb for django tracked in git.","Q_Score":0,"Tags":"python,ruby-on-rails,django,postgresql,ruby-on-rails-4","A_Id":32450497,"CreationDate":"2015-09-08T06:11:00.000","Title":"Rails and Django migrations on a shared database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Recently, I used Python and Scrapy to crawl article information like 'title' from a blog. Without using a database, the results are fine \/ as expected.  However, when I use SQLalchemy, I received the following error:\n\nInterfaceError:(sqlite3.InterfaceError)Error binding parameter 0\n  -probably unsupported type.[SQL:u'INSERT INTO myblog(title)  VALUES  (?)']  [PARAMETERS:([u'\\r\\n     Accelerated c++\\u5b66\\u4e60\n  chapter3 -----\\u4f7f\\u7528\\u6279\\u636e            \\r\\n        '],)]\n\nMy xpath expression is:\nitem['title'] = sel.xpath('\/\/*[@class=\"link_title\"]\/a\/text()').extract() \nWhich gives me the following value for item['title']:\n[u'\\r\\n     Accelerated c++ \\u5b66 \\u4e60   chapter3 -----\\u4f7f\\u7528\\u6279\\u636e            \\r\\n        ']\nIt's unicode, why doesn't sqlite3 support it? This blog's title information contains some Chinese.  I am a tired of sqlalchemy.  I've referred its documents, but found nothing, and I'm out of ideas.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":454,"Q_Id":32460120,"Users Score":0,"Answer":"The problem that you're experiencing is that SQLite3 wants a datatype of \"String\", and you're passing in a list with a unicode string in it.\nchange:\nitem['title'] = sel.xpath('\/\/*[@class=\"link_title\"]\/a\/text()').extract()\nto\nitem['title'] = sel.xpath('\/\/*[@class=\"link_title\"]\/a\/text()').extract()[0].\nYou'll be left with a string to be inserted, and your SQLite3 errors should go away.  Warning, though, if your ever wanting to deal with more than just one title, this will limit you to the first.  You can use whatever method you want to persuade those into being a string, though.","Q_Score":2,"Tags":"python,xpath,sqlite,scrapy","A_Id":32471731,"CreationDate":"2015-09-08T14:13:00.000","Title":"InterfaceError:(sqlte3.InterfaceError)Error binding parameter 0","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have to write a python script which will copy a file in s3 to my EBS directory, here the problem is I'm running this python script from my local machine. is there any boto function in which I can copy from s3 to EBS without storing in my local?","AnswerCount":1,"Available Count":1,"Score":0.537049567,"is_accepted":false,"ViewCount":830,"Q_Id":32478432,"Users Score":3,"Answer":"No. EBS volumes are accessible only on the EC2 instance they're mounted on. If you want to download a file directly from S3 to an EBS volume, you need to run your script on the EC2 instance.","Q_Score":0,"Tags":"python,amazon-web-services,amazon-s3,boto,boto3","A_Id":32478697,"CreationDate":"2015-09-09T11:33:00.000","Title":"Copy file from S3 to EBS","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":1,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"My organisation uses Business Objects as a layer over its Oracle database so that people like me (i.e. not in the IT dept) can access the data without the risk of breaking something.\nI have a PythonAnywhere account where I have a few dashboards built using Flask.\nEach morning, BO sends me an email with the cvs files of the data that I want. I then upload these to a MYSQL server, and go from there. There is also an option to send it to an FTP recipient...but that's pretty much it.\nIs it possible to set up an FTP server on my (paid for) PythonAnywhere account? If I could have those files go to a dir like \/data, I could then have a scheduled job to insert them into my DB.\nThe data is already in the public domain and not sensitive.\nOr is there intact a better way?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":875,"Q_Id":32509768,"Users Score":1,"Answer":"PythonAnywhere dev here: we don't support regular FTP, unfortunately.  If there was a way to tell BO to send the data via an HTTP POST to a website, then you could set up a simple Flask app to handle that -- but I'm guessing from what you say that it doesn't :-(","Q_Score":1,"Tags":"ftp,pythonanywhere","A_Id":32530008,"CreationDate":"2015-09-10T19:01:00.000","Title":"Sending csv file via FTP to PythonAnywhere","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am trying to read a data from csv file to postgres table. I have two columns in  table, but there are four fields in csv data file. I want to read only two specific columns from csv to table.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":509,"Q_Id":32553773,"Users Score":0,"Answer":"Would you know how to do it if there were only those two columns in CSV file?\nIf yes, then the simplest solution is to transform the CSV prior to importing into Postgres.","Q_Score":0,"Tags":"python,sql,postgresql,csv,psycopg2","A_Id":32553942,"CreationDate":"2015-09-13T19:36:00.000","Title":"how to copy specific columns from CSV file to postgres table using psycopg2?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"It's been two days I am trying to work with cx_Oracle. I want to connect to oracle from python. But I am getting \"ImportError: DLL load failed: The specified procedure could not be found.\" error. I have already gone through many posts and tried the things suggested on them, but nothing helped me.\nI checked the versions of Windows, Python, Oracle client as suggested on many posts but all of them looks good to me.\nPython veriosn 2.7: 64 bit\nPython 2.7.8 (default, Jun 30 2014, 16:08:48) [MSC v.1500 64 bit (AMD64)] on win\n32\nWindows 7: 64 bit\nOracle client is 11.2.0: 64 bit\nI ran Sqlplus and checked task manager to confirm that. As I have both 32 and 64 bit client installed on my system, but 64 bit is set in PATH variable.\nPlease help me to sort out this problem. Do let me know if any other information is needed.","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":1699,"Q_Id":32561547,"Users Score":1,"Answer":"I was able to sort it out. I had installed the incorrect version of cx_Oracle previously. It was for 12c oracle client. I installed 11g version later and it started working for me.\nNote: There is no need to set ORACLE_HOME environment variable.\nOracle client, Python, Windows OS all of them must be of same architecture. Either 32 or 64 bit.","Q_Score":3,"Tags":"oracle,python-2.7,cx-oracle","A_Id":32578626,"CreationDate":"2015-09-14T09:37:00.000","Title":"Not able to import cx_Oracle in python \"ImportError: DLL load failed: The specified procedure could not be found.\"","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Has anyone installed psycopg2 for python 3 on Centos 7?  I'm sure it's possible, but when I run:\npip install psycopg2\nI get:\nCould not find a version that satisfies the requirement pyscopg2 (from versions: )\nNo matching distribution found for pyscopg2","AnswerCount":1,"Available Count":1,"Score":0.3799489623,"is_accepted":false,"ViewCount":1254,"Q_Id":32576326,"Users Score":2,"Answer":"You have misspelled the name of the library.  The correct name is psycopg2","Q_Score":0,"Tags":"python,postgresql,python-3.x,centos,centos7","A_Id":32576369,"CreationDate":"2015-09-15T01:35:00.000","Title":"psycopg2 for python3 on Centos 7","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I found this line to help configure Postgresql in web2py but I can't seem to find a good place where to put it :\ndb = DAL(\"postgres:\/\/myuser:mypassword@localhost:5432\/mydb\")\nDo I really have to write it in all db.py ?","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":939,"Q_Id":32616625,"Users Score":2,"Answer":"Files in the \/models folder are executed in alphabetical order, so just put the DAL definition at the top of the first model file that needs to use it (it will then be available globally in all subsequent model files as well as all controllers and views).","Q_Score":0,"Tags":"python,database,web2py","A_Id":32618356,"CreationDate":"2015-09-16T19:00:00.000","Title":"web2py database configuration","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I just upgraded my django from 1.7.1 to 1.8.4. I tried to run python manage.py migrate but I got this error:\ndjango.db.utils.ProgrammingError: relation \"django_content_type\" does not exist\nI dropped my database, created a new one, and ran the command again. But I get the same error. Am I missing something? Do I need to do something for upgrading my django?\nEDIT:\nI downgraded back to 1.7.1 and it works. Is there a way to fix it for 1.8.4?","AnswerCount":6,"Available Count":4,"Score":1.2,"is_accepted":true,"ViewCount":10126,"Q_Id":32620930,"Users Score":1,"Answer":"Well, I found the issue. I have auditlog installed as one my apps. I removed it and migrate works fine.","Q_Score":6,"Tags":"django,python-2.7,django-1.7,django-migrations,django-1.8","A_Id":32637043,"CreationDate":"2015-09-17T00:45:00.000","Title":"Django 1.8 migrate: django_content_type does not exist","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I just upgraded my django from 1.7.1 to 1.8.4. I tried to run python manage.py migrate but I got this error:\ndjango.db.utils.ProgrammingError: relation \"django_content_type\" does not exist\nI dropped my database, created a new one, and ran the command again. But I get the same error. Am I missing something? Do I need to do something for upgrading my django?\nEDIT:\nI downgraded back to 1.7.1 and it works. Is there a way to fix it for 1.8.4?","AnswerCount":6,"Available Count":4,"Score":0.0,"is_accepted":false,"ViewCount":10126,"Q_Id":32620930,"Users Score":0,"Answer":"i had drop the database and rebuild it, then in the PyCharm Terminal py manage.py makemigrations and py manage.py migrate fix this problem. I think the reason is the table django_content_type is the django's table, if it misssed can not migrate, so have to drop the database and rebuild.","Q_Score":6,"Tags":"django,python-2.7,django-1.7,django-migrations,django-1.8","A_Id":67501508,"CreationDate":"2015-09-17T00:45:00.000","Title":"Django 1.8 migrate: django_content_type does not exist","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I just upgraded my django from 1.7.1 to 1.8.4. I tried to run python manage.py migrate but I got this error:\ndjango.db.utils.ProgrammingError: relation \"django_content_type\" does not exist\nI dropped my database, created a new one, and ran the command again. But I get the same error. Am I missing something? Do I need to do something for upgrading my django?\nEDIT:\nI downgraded back to 1.7.1 and it works. Is there a way to fix it for 1.8.4?","AnswerCount":6,"Available Count":4,"Score":1.0,"is_accepted":false,"ViewCount":10126,"Q_Id":32620930,"Users Score":6,"Answer":"Delete all the migration folder from your app and delete the database then migrate your database......\nif this does not work delete django_migration table from database and add the \"name\" column in django_content_type table ALTER TABLE django_content_type ADD COLUMN name character varying(50) NOT NULL DEFAULT 'anyName'; and then run $ python manage.py migrate --fake-initial","Q_Score":6,"Tags":"django,python-2.7,django-1.7,django-migrations,django-1.8","A_Id":32623157,"CreationDate":"2015-09-17T00:45:00.000","Title":"Django 1.8 migrate: django_content_type does not exist","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I just upgraded my django from 1.7.1 to 1.8.4. I tried to run python manage.py migrate but I got this error:\ndjango.db.utils.ProgrammingError: relation \"django_content_type\" does not exist\nI dropped my database, created a new one, and ran the command again. But I get the same error. Am I missing something? Do I need to do something for upgrading my django?\nEDIT:\nI downgraded back to 1.7.1 and it works. Is there a way to fix it for 1.8.4?","AnswerCount":6,"Available Count":4,"Score":0.0665680765,"is_accepted":false,"ViewCount":10126,"Q_Id":32620930,"Users Score":2,"Answer":"Here's what I found\/did. I am using django 1.8.13 and python 2.7. The problem did not occur for Sqlite. It did occur for PostgreSQL. \nI have an app the uses a GenericForeignKey (which relies on Contenttypes). I have another app that has a model that is linked to the first app via the GenericForeignKey. If I run makemigrations for both these apps, then migrate works.","Q_Score":6,"Tags":"django,python-2.7,django-1.7,django-migrations,django-1.8","A_Id":37074120,"CreationDate":"2015-09-17T00:45:00.000","Title":"Django 1.8 migrate: django_content_type does not exist","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I've a read-only access to a database server dbserver1. I need to store the result set generated from my query running on dbserver1 into another server of mine dbserver2. How should I go about doing that? \nAlso can I setup a trigger which will automatically copy new entries that will come in to the dbserver1 to dbserver2? Source and destination are both using Microsoft SQL server.\nFollowing on that, I need to call a python script on a database trigger event. Any ideas on how could that be accomplished?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":449,"Q_Id":32659008,"Users Score":1,"Answer":"lad2015 answered the first part. The second part can be infinitely more dangerous as it involves calling outside the Sql Server process.\nIn the bad old days one would use the xp_cmdshell. These days it may be more worthwhile to create an Unsafe CLR stored procedure that'll call the python script.\nBut it is very dangerous and I cannot stress just how much you shouldn't do it unless you really have no other choices.\nI'd prefer to see a polling python script that runs 100% external to Sql that connects to a Status table populated by the trigger and performs work accordingly.","Q_Score":0,"Tags":"python,sql-server,database-design,triggers,database-cloning","A_Id":32659567,"CreationDate":"2015-09-18T18:45:00.000","Title":"Copy database from one server to another server + trigger python script on a database event","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"In the environment, we have an excel file, which includes rawdata in one sheet and pivot table and charts in another sheet.\nI need to append rows every day to raw data automatically using a python job.\nI am not sure, but there may be some VB Script running on the front end which will refresh the pivot tables.\nI used openpyxl and by following its online documentation, I was able to append rows and save the workbook. I used keep_vba=true while loading the workbook to keep the VBA modules inside to enable pivoting. But after saving the workbook, the xlsx is not being opened anymore using MS office and saying the format or the extension is not valid. I can see the data using python but with office, its not working anymore. If I don't use keep_vba=true, then pivoting is not working, only the previous values are present (ofcourse as I understood, as VBA script is needed for pivoting).\nCould you explain me what's happening? I am new to python and don't know its concepts much. \nHow can I fix this in openpyxl or is there any better alternative other than openpyxl. Data connections in MS office is not an option for me.\nAs I understood, xlsx may need special modules to save the VB script to save in the same way as it may be saved using MS office. If it is, then what is the purpose of keep_vba=true ?\nI would be grateful if you could explain in more detail. I would love to know.\nAs I have very short time to complete this task, I am looking for a quick answer here, instead of going through all the concepts.\nThankyou!","AnswerCount":1,"Available Count":1,"Score":0.537049567,"is_accepted":false,"ViewCount":3002,"Q_Id":32682336,"Users Score":3,"Answer":"You have to save the files with the extension \".xlsm\" rather than \".xlsx\". The .xlsx format exists specifically to provide the user with assurance that there is no VBA code within the file. This is an Excel standard and not a problem with openpyxl. With that said, I haven't worked with openpyxl, so I'm not sure what you need to do to be sure your files are properly converted to .xlsm.\nEdit: Sorry, misread your question first time around. Easiest step would be to set keep_vba=False. That might resolve your issue right there, since you're telling openpyxl to look for VBA code that can't possibly exist in an xlsx file. Hard to say more than that until you post the relevant section of your code.","Q_Score":1,"Tags":"python,xlsx,openpyxl","A_Id":32684112,"CreationDate":"2015-09-20T17:37:00.000","Title":"xlsx file extension not valid after saving with openpyxl and keep_vba=true. Which is the best way?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm using Python 2.7.5 in Spyder along with Sqlite3 3.6.21. I have noticed the execute method to be pretty slow, pretty much regardless of the size of the database I'm creating. After doing some research, no solution really works for me:\n\nPython 3 is not supported by Spyder yet\nupdating the Sqlite3 version does not work (replacing the dll file causes problems)\n\nIs there a way around this? If any more details are needed, I'm glad to elaborate further.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":157,"Q_Id":32682674,"Users Score":0,"Answer":"Indeed, inspired by Colonel Thirty Two's comment above, I just realized that I need to wrap all my operations into one transaction. This was trivial to implement and improved overall efficiency drastically. Thanks once again!","Q_Score":0,"Tags":"python,sqlite","A_Id":32700885,"CreationDate":"2015-09-20T18:12:00.000","Title":"python sqlite3 execute method slow","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a large Excel file (450mb+). I need to replace (,) -> (; or .) for one of my fastload scripts to work.  I am not able to open the file at all. Any script would actually involve opening the file, performing operation, saving and closing the file, in that order.\nWill a VB script like that work here for the 450mb+ file, wherein the file is not opening only.\n\nIs there any VB script , Shell script, Python, Java etc I can write actually to perform the replacement(operation) without opening the Excel file?\nOr alternatively, is there any way of opening an Excel file that big\nand performing that operation.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":273,"Q_Id":32690561,"Users Score":0,"Answer":"If you have access to a Linux environment (which you might since you mention shell script as one of your options) then just use sed in a terminal or Putty:\nsed -i .bak 's\/,\/;\/g' yourfile.excel\nSed streams the text without loading the entire file at once.\n-i will make changes to your original file but providing .bak will create a copy named yourfile.excel.bak first","Q_Score":1,"Tags":"python,excel,shell,vbscript","A_Id":32691381,"CreationDate":"2015-09-21T08:27:00.000","Title":"Replace characters without opening Excel file","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I had posted about this error some time back but need some more clarification on this.\nI'm currently building out a Django Web Application using Visual Studio 2013 on a Windows 10 machine (Running Python3.4). While starting out I was constantly dealing with the MySQL connectivity issue, for which I did a mysqlclient pip-install. I had created two projects that use MySQL as a backend and after installing the mysqlclient I was able to connect to the database through the current project I was working on. When I opened the second project and tried to connect to the database, I got the same 'No Module called MySqlDB' error.\nNow, the difference between both projects was that the first one was NOT created within a Virtual Environment whereas the second was.\nSo I have come to deduce that projects created within the Python virtual environment are not able to connect to the database. Can someone here please help me in getting this problem solved. I need to know how the mysqlclient module can be loaded onto a virtual environment so that a project can use it.\nThanks","AnswerCount":3,"Available Count":1,"Score":0.0665680765,"is_accepted":false,"ViewCount":660,"Q_Id":32715175,"Users Score":1,"Answer":"This approach worked ! I was able to install the mysqlclient inside the virtual environment through the following command:-\npython -m pip install mysqlclient\nThanks Much..!!!!!","Q_Score":0,"Tags":"python,mysql,django","A_Id":32723517,"CreationDate":"2015-09-22T11:02:00.000","Title":"No Module Named MySqlDb in Python Virtual Enviroment","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Because I need to parse and then use the actual data in cells, I open an xlsm in openpyxl with data_only = True.\nThis has proved very useful. Now though, having the same need for an xlsm that contains formuale in cells, when I then save my changes, the formulae are missing from the saved version.\nAre data_only = True and formulae mutually exclusive? If not, how can I access the actual value in cells without losing the formulae when I save?\nWhen I say I lose the formulae, it seems that the results of the formulae (sums, concatenattions etc.) get preserved. But the actual formulaes themselves are no longer displayed when a cell is clicked.\nUPDATE:\nTo confirm whether or not the formulaes were being preserved or not, I've re-opened the saved xlsm, this time with data_only left as False. I've checked the value of a cell that had been constructed using a formula. Had formulae been preserved, opening the xlsm with data_only set to False should have return the formula. But it returns the actual text value (which is not what I want).","AnswerCount":2,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":6128,"Q_Id":32772954,"Users Score":2,"Answer":"If you want to preserve the integrity of the workbook, ie. retain the formulae, the you cannot use data_only=True. The documentation makes this very clear.","Q_Score":6,"Tags":"python,python-2.7,openpyxl","A_Id":32776318,"CreationDate":"2015-09-25T00:21:00.000","Title":"How to save in openpyxl without losing formulae?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Arrghh...  I am trying to use mySQL with Python.  I have installed all the libraries for using mySQL, but keep getting the: \"ImportError: No module named mysql.connector\" for \"import mysql.connector\", \"mysql\", etc..\nHere is my config:\nI have a RHEL server:\n\nRed Hat Enterprise Linux Server release 6.7 (Santiago)\n\nwith Python 2.7.9\n\nPython 2.7.9 (default, Dec 16 2014, 10:42:10) \n  [GCC 4.4.7 20120313 (Red Hat 4.4.7-11)] on linux2\n\nwith mySQL 5.1\n\nmysql  Ver 14.14 Distrib 5.1.73, for redhat-linux-gnu (x86_64) using readline 5.1\n\n\nI have all the appropriate libraries\/modules installed, I think!\nyum install MySQL-python\n\nPackage MySQL-python-1.2.3-0.3.c1.1.el6.x86_64 already installed and latest version\n\nyum install mysql-connector-python.noarch\n\nInstalled: mysql-connector-python.noarch 0:1.1.6-1.el6\n  yum install MySQL-python.x86_64\n  Package MySQL-python-1.2.3-0.3.c1.1.el6.x86_64 already installed and latest version\n\nyum install mysql-connector-python.noarch\n\nPackage mysql-connector-python-1.1.6-1.el6.noarch already installed and latest version\n\n\nWhat am I doing wrong?  HELP!?","AnswerCount":2,"Available Count":2,"Score":-0.0996679946,"is_accepted":false,"ViewCount":544,"Q_Id":32786620,"Users Score":-1,"Answer":"Nevermind!!!\nApparently I am installing Python and libraries in the right directories and such (I have always used YUM), but apparently there are other versions of Python installed.. need to clean that up.\n\nRunning: \/usr\/bin\/python\nAll the modules worked!\nRunning: python (Linux finding python in the path somewhere)\nModules are not working!\n\nGrrr...\nMaybe I will checking out the Python \"Virtual Environments\"!\nThanks for the suggestions!","Q_Score":0,"Tags":"python,mysql,linux,python-2.7","A_Id":32786846,"CreationDate":"2015-09-25T16:24:00.000","Title":"mySQL within Python 2.7.9","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Arrghh...  I am trying to use mySQL with Python.  I have installed all the libraries for using mySQL, but keep getting the: \"ImportError: No module named mysql.connector\" for \"import mysql.connector\", \"mysql\", etc..\nHere is my config:\nI have a RHEL server:\n\nRed Hat Enterprise Linux Server release 6.7 (Santiago)\n\nwith Python 2.7.9\n\nPython 2.7.9 (default, Dec 16 2014, 10:42:10) \n  [GCC 4.4.7 20120313 (Red Hat 4.4.7-11)] on linux2\n\nwith mySQL 5.1\n\nmysql  Ver 14.14 Distrib 5.1.73, for redhat-linux-gnu (x86_64) using readline 5.1\n\n\nI have all the appropriate libraries\/modules installed, I think!\nyum install MySQL-python\n\nPackage MySQL-python-1.2.3-0.3.c1.1.el6.x86_64 already installed and latest version\n\nyum install mysql-connector-python.noarch\n\nInstalled: mysql-connector-python.noarch 0:1.1.6-1.el6\n  yum install MySQL-python.x86_64\n  Package MySQL-python-1.2.3-0.3.c1.1.el6.x86_64 already installed and latest version\n\nyum install mysql-connector-python.noarch\n\nPackage mysql-connector-python-1.1.6-1.el6.noarch already installed and latest version\n\n\nWhat am I doing wrong?  HELP!?","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":544,"Q_Id":32786620,"Users Score":2,"Answer":"You should use virtualenv in order to isolate the environment. That way your project libs won't clash with other projects libs. Also, you probably should install the Mysql driver\/connector from pip.\nVirtualenv is a CLI tool for managing your environment. It is really easy to use and helps a lot. What it does is to create all the folders Python needs on a custom location (usually your specific project folder) and it also sets all the shell variables so that Python can find the folders. Your system (\/usr and so on) folders are not removed from the shell; rather, they just get a low priority. That is done by correctly setting your PATH variable, and virtualenv does that when you load a determined environment.\nIt is common practice to use an environment for each project you work on. That way, Python and pip won't install libs on the global folders. Instead, pip installs the libs on the current environment you are using. That avoids version conflicts and even Python version conflicts.","Q_Score":0,"Tags":"python,mysql,linux,python-2.7","A_Id":32786680,"CreationDate":"2015-09-25T16:24:00.000","Title":"mySQL within Python 2.7.9","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I wrote a Python program which produces invoices in a specific form as .xlsx files using openpyxl. I have the general invoice form as an Excel workbook and my program copies this form and fills up the details about the specific client (eg. client refernce number, price, etc.) which are read from another .txt file.\nThe program works perfectly. The only problem is that the form contains a cell which has multiple styles: half of the letters are red and the rest black and there is also size difference. This cell is not edited in my program (it is the same in all the invoices), however after the rest worksheet is edited by my program the cell keeps only the first style (the red letters).\nWhy does openpyxl changes this cell since I don't edit it? Does openpyxl support multiple styles, or I have to split the letters with different styles in seperate cells?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1165,"Q_Id":32788716,"Users Score":0,"Answer":"openpyxl does not support multiple styles within an individual cell.","Q_Score":3,"Tags":"python,excel,openpyxl","A_Id":32790713,"CreationDate":"2015-09-25T18:45:00.000","Title":"Multiple styles in one cell in openpyxl","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I want to install py-MySQLdb but I always get the same lib error..\nAny suggestions?\nThanks in advance\nImportError: \/usr\/lib\/libz.so.6: unsupported file layout\n*** [do-configure] Error code 1\nStop in \/usr\/ports\/databases\/py-MySQLdb.\n*** [install] Error code 1\nStop in \/usr\/ports\/databases\/py-MySQLdb.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":226,"Q_Id":32826804,"Users Score":0,"Answer":"It seems like you mixed 32 and 64bit libraries.\nI suggest cleaning up the wrong libraries (at least libz seems to be affected) and restoring them from backup\/installation medium","Q_Score":1,"Tags":"python,freebsd","A_Id":32839165,"CreationDate":"2015-09-28T15:38:00.000","Title":"FreeBSD 9.3 ImportError while installing py-MySQLdb","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am writing a Python script to fetch and update some data on a remote oracle database from a Linux server. I would like to know how can I connect to remote oracle database from the server.\nDo I necessarily need to have an oracle client installed on my server or any connector can be used for the same?\nAnd also if I use cx_Oracle module in Python, is there any dependency that has to be fulfilled for making it work?","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":6425,"Q_Id":32836510,"Users Score":0,"Answer":"Yes, you definitely need to install an Oracle Client, it even says so in cx_oracle readme.txt.\nAnother recommendation you can find there is installing an oracle instant client, which is the minimal installation needed to communicate with Oracle, and is the simplest to use.\nOther dependencies can usually be found in the readme.txt file, and should be the first place to look for these details.","Q_Score":1,"Tags":"python,oracle,database-connection,cx-oracle","A_Id":32836606,"CreationDate":"2015-09-29T05:47:00.000","Title":"Python connection to Oracle database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I inherited a project and am having what seems to be a permissions issue when trying to interact with the database. Basically we have a two step process of detach and then delete. \nDoes anyone know where the user would come from if the connection string only has driver, server, and database name. \nEDIT\nI am on Windows Server 2008 standard\nEDIT\n\"DRIVER={%s};SERVER=%s;DATABASE=%s;\" Where driver is \"SQL Server\"","AnswerCount":2,"Available Count":2,"Score":0.1973753202,"is_accepted":false,"ViewCount":989,"Q_Id":32914037,"Users Score":2,"Answer":"Since you're on Windows, a few things you should know:\n\nUsing the Driver={SQL Server} only enables features and data types\nsupported by SQL Server 2000. For features up through 2005, use {SQL\nNative Client} and for features up through 2008 use {SQL Server\nNative Client 10.0}.\nTo view your ODBC connections, go to Start and search for \"ODBC\" and\nbring up Data Sources (ODBC). This will list User, System, and File\nDSNs in a GUI. You should find the DSN with username and password\nfilled in there.","Q_Score":3,"Tags":"python,database,permissions,pyodbc","A_Id":32915064,"CreationDate":"2015-10-02T18:57:00.000","Title":"Where does pyodbc get its user and pwd from when none are provided in the connection string","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I inherited a project and am having what seems to be a permissions issue when trying to interact with the database. Basically we have a two step process of detach and then delete. \nDoes anyone know where the user would come from if the connection string only has driver, server, and database name. \nEDIT\nI am on Windows Server 2008 standard\nEDIT\n\"DRIVER={%s};SERVER=%s;DATABASE=%s;\" Where driver is \"SQL Server\"","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":989,"Q_Id":32914037,"Users Score":3,"Answer":"I just did a few tests and the {SQL Server} ODBC driver apparently defaults to using Windows Authentication if the Trusted_connection and UID options are both omitted from the connection string. So, your Python script must be connecting to the SQL Server instance using the Windows credentials of the user running the script.\n(On the other hand, the {SQL Server Native Client 10.0} driver seems to default to SQL Authentication unless Trusted_connection=yes is included in the connection string.)","Q_Score":3,"Tags":"python,database,permissions,pyodbc","A_Id":32951286,"CreationDate":"2015-10-02T18:57:00.000","Title":"Where does pyodbc get its user and pwd from when none are provided in the connection string","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"In my Google App Engine App, I have a large number of entities representing people.  At certain times, I want to process these entities, and it is really important that I have the most up to date data.  There are far too many to put them in the same entity group or do a cross-group transaction.\nAs a solution, I am considering storing a list of keys in Google Cloud Storage.  I actually use the person's email address as the key name so I can store a list of email addresses in a text file.\nWhen I want to process all of the entities, I can do the following:\n\nRead the file from Google Cloud Storage\nIterate over the file in batches (say 100)\nUse ndb.get_multi() to get the entities (this will always give the most recent data)\nProcess the entities\nRepeat with next batch until done\n\nAre there any problems with this process or is there a better way to do it?","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":60,"Q_Id":32915462,"Users Score":1,"Answer":"if, like you say in comments, your lists change rarely and cant use ancestors (I assume because of write frequency in the rest of your system), your proposed solution would work fine. You can do as many get(multi) and as frequently as you wish, datastore can handle it.\nSince you mentioned you can handle having that keys list updated as needed, that would be a good way to do it.\nYou can stream-read a big file (say from cloud storage with one row per line) and use datastore async reads to finish very quickly or use google cloud dataflow to do the reading and processing\/consolidating.\ndataflow can also be used to instantly generate that keys list file in cloud storage.","Q_Score":0,"Tags":"python,google-app-engine,google-cloud-datastore,eventual-consistency","A_Id":32941257,"CreationDate":"2015-10-02T20:35:00.000","Title":"GAE\/P: Storing list of keys to guarantee getting up to date data","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I'm startint a project on my own and I'm having some troubles with importing datas from IMDb. Already downloaded everything that's necessary but I'm kinda newbie in this python and command lines stuff, and it's pissing me off because I'm doing my homework (trying to learn how to do these things) but I can't reach it :(\nSo, is there anybody who could create a step-by-step of how to do it? I mean, something like:\nYou'll need to download this and run this commands on 'x'.\nCreate a database and then run 'x'.\nIt would be amazing for me and other people who don't know how to do this as well and I would truly appreciate A LOT, really!. Oh, I'm using Windows.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1057,"Q_Id":32953669,"Users Score":3,"Answer":"Problem solved!\nFor those who are having the same problem, here it goes:\nDownload the java movie database. It works witch postrgres or mysql. You'll have to download java runtime. After that open the readme in the directory you installed the java movie database, there are all the instructions, but I'll help you.\nFollow the link off the *.list archives and download then. Move them into a new folder. After that, open JMDB (java movie database) and select the right folders of moviecollection, sound etc (they are in C:\/programs...). In IMDb-import select the folder you created which contains the *.files. Well, this is the end. Run the JMDB and you'll have your DB populated.","Q_Score":0,"Tags":"python,postgresql,imdb,imdbpy","A_Id":32972532,"CreationDate":"2015-10-05T16:44:00.000","Title":"How to run imdbpy2sql.py and import data from IMDb to postgres","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I need to change data in large excel file(more than 240 000 rows on sheet), it's possible through win32com.client, but I need use Linux OS ...\nPlease, could you advise something suitable!","AnswerCount":2,"Available Count":1,"Score":-0.0996679946,"is_accepted":false,"ViewCount":414,"Q_Id":32994822,"Users Score":-1,"Answer":"If it's raw data, I always export it to a .csv file and work on it directly. CSV is a simple format with one row per line and all the elements on the row separated with commas. Depending on what you want to do, it's not hard to write a python script to edit that.","Q_Score":4,"Tags":"python,python-2.7","A_Id":32997001,"CreationDate":"2015-10-07T14:22:00.000","Title":"Change data in large excel file(more than 240 000 rows on sheet)","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I tried to open and read the contents of cookie.sqlite file in the firefox.\ncookie.sqlie is the database file were all cookies of webpages opened in firefox are stored. When I am trying to access with a python program it is not allowing to read, as cookie.sqlite is locked. How to open and read the contents.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":858,"Q_Id":33078383,"Users Score":0,"Answer":"That's not a programming question as is -- sqlite sets a flag in the file so that when trying to open the file a second time, the other sqlite instance knows that the file is \"dirty\", because the first Sqlite is actively modifying it. There's no way around this -- data integrity is the core functionality of databases, and hence, you really shouldn't try to do that. \nI'd generally recommend just writing a Firefox extension, which then can access the cookie database as accessible from within firefox, and export whatever you need to your external program.","Q_Score":0,"Tags":"python,sqlite,cookies","A_Id":33078468,"CreationDate":"2015-10-12T10:02:00.000","Title":"how to read cookie.sqlite file in firefox through python program","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm not overly familiar with Linux and am trying to run a Python script that is dependent upon Python 3.4 as well as pymssql.  Both Python 2.7 and 3.4 are installed (usr\/local\/lib\/[PYTHON_VERSION_HERE]).  pymssql is also installed, except it's installed in the Python 2.7 directory, not the 3.4 directory.  When I run my Python script (python3 myscript.py), I get the following error:\nFile \"myscript.py\", line 2, in \n  import pymssql\nImportError: No module named 'pymssql'\nMy belief is that I need to install pymssql to the Python 3.4 folder, but that's my uneducated opinion.  So my question is this:\nHow can I get my script to run using Python 3.4 as well as use the pymssql package (sorry, probably wrong term there)?\nI've tried many different approaches, broken my Ubuntu install (and subsequently reimaged), and at this point don't know what to do.  I am a relative novice, so some of the replies I've seen on the web say to use ENV and separate the versions are really far beyond the scope of my understanding.  If I have to go that route, then I will, but if there is another (i.e. easier) way to go here, I'd really appreciate it, as this was supposed to just be a tiny thing I need to take care of but it's tied up 12 hours of my life thus far!  Thank you in advance.","AnswerCount":2,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":5321,"Q_Id":33114337,"Users Score":2,"Answer":"It is better if when you run python3.4 you can have modules for that version.\nAnother way to get the desire modules running is install pip for python 3.4\nsudo apt-get install python3-pip\nThen install the module you want\npython3.4 -m pip install  pymssql","Q_Score":1,"Tags":"python,linux,pymssql","A_Id":35328465,"CreationDate":"2015-10-13T23:38:00.000","Title":"How to install pymssql to Python 3.4 rather than 2.7 on Ubuntu Linux?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'd like to use the Dropbox API (with access only to my own account) to generate a link to SomeFile.xlsx that I can put in an email to multiple Dropbox account holders, all of whom are presumed to have access to the file. I'd like for the same link, when clicked on, to talk to Dropbox to figure out where SomeFile.xlsx is on their local filesystem and open that up directly.\nIn other words, I do NOT want to link to the cloud copy of the file. I want to link to the clicker's locally-synced version of the file.\nDoes Dropbox have that service and does the API let me consume it? I haven't been able to discover the answer from the documentation yet.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":82,"Q_Id":33134816,"Users Score":1,"Answer":"No, Dropbox doesn't have an API like this.","Q_Score":0,"Tags":"python,dropbox,dropbox-api","A_Id":33136183,"CreationDate":"2015-10-14T20:18:00.000","Title":"Relative link to local copy of Dropbox file","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am doing an application in Excel and I'd like to use python language. I've seen a pretty cool library called xlwings, but to run it a user need to have python installed.\nIs there any possibility to prepare this kind of application that will be launch from a PC without Python?\nAny suggestion are welcome!","AnswerCount":4,"Available Count":3,"Score":1.2,"is_accepted":true,"ViewCount":963,"Q_Id":33172842,"Users Score":0,"Answer":"A small workaround could be to package your application with cx_freeze or pyinstaller. Then it can run on a machine without installing python. The downside is of course that the program tend to be a bit bulky in size.","Q_Score":1,"Tags":"python,excel,xlwings","A_Id":33176797,"CreationDate":"2015-10-16T14:24:00.000","Title":"create an application in excel using python for a user without python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am doing an application in Excel and I'd like to use python language. I've seen a pretty cool library called xlwings, but to run it a user need to have python installed.\nIs there any possibility to prepare this kind of application that will be launch from a PC without Python?\nAny suggestion are welcome!","AnswerCount":4,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":963,"Q_Id":33172842,"Users Score":0,"Answer":"It is possible using xlloop. This is a customized client-server approach, where the client is an excel .xll which must be installed on client's machine. \nThe server can be written in many languages, including python, and of course it must be launched on a server that has python installed. Currently the .xll is available only for 32 bits.","Q_Score":1,"Tags":"python,excel,xlwings","A_Id":33176474,"CreationDate":"2015-10-16T14:24:00.000","Title":"create an application in excel using python for a user without python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am doing an application in Excel and I'd like to use python language. I've seen a pretty cool library called xlwings, but to run it a user need to have python installed.\nIs there any possibility to prepare this kind of application that will be launch from a PC without Python?\nAny suggestion are welcome!","AnswerCount":4,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":963,"Q_Id":33172842,"Users Score":0,"Answer":"no. you must need install a python and for interpreting the python function etc.","Q_Score":1,"Tags":"python,excel,xlwings","A_Id":33172988,"CreationDate":"2015-10-16T14:24:00.000","Title":"create an application in excel using python for a user without python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm new to using databases in Python and I'm playing around with MySQLdb. I have several methods that will issue database calls. Do I need to go through the database connection steps every time I want to make a call or is the instance of the database persistent?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":32,"Q_Id":33243575,"Users Score":1,"Answer":"Connection instance is persistent, you can connect one time and work with connection as long as you need.","Q_Score":1,"Tags":"python,mysql,mysql-python","A_Id":33243613,"CreationDate":"2015-10-20T17:57:00.000","Title":"Do I need to call MySQLdb.connect() in every method where I execute a database operation?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have the following table\ncreate table players (name varchar(30), playerid serial primary key);\nAnd I am working with the script:\ndef registerPlayer(name):\n    \"\"\"Registers new player.\"\"\"\n    db = psycopg2.connect(\"dbname=tournament\")\n    c = db.cursor()\n    player = \"insert into players values (%s);\"\n    scores = \"insert into scores (wins, matches) values (0, 0);\"\n    c.execute(player, (name,))\n    c.execute(scores)\n    db.commit()\n    db.close()\nBut when I try and register a player with the argument in quotes as so:\nregisterPlayer(\"Any Name\")\nIt doesn't work... Now, if I directly enter the query into psql, it works if I only use single quotes as so\nINSERT INTO players VALUES ('Any Name');\nBut not if I use \"Any Name\". If I use the \"\", it tells me:\nERROR:  column \"Any Name\" does not exist Now, this is a problem if I want to enter a name in such as Bob O'Neal, because it will close off that entry after the O.\nThe quotes were working fine the other day, and I went to format so that all the SQL queries were capitalized, and everything stopped working. I returned to the code that was working fine, and now nothing is working!","AnswerCount":1,"Available Count":1,"Score":0.3799489623,"is_accepted":false,"ViewCount":74,"Q_Id":33248482,"Users Score":2,"Answer":"Double-quotes in SQL are not strings - they escape table, index, and other object names (ex. \"John Smith\" refers to a table named John Smith). Only single quoted strings are actually strings.\nIn any case, if you are using query parameters properly (which, in your example code, you seem to be), you should not have to worry about escaping your data. Simply pass the raw values to execute (ex. c.execute(player, (\"Bob O'Niel\",)))","Q_Score":0,"Tags":"python,sql,database,postgresql","A_Id":33248538,"CreationDate":"2015-10-20T23:24:00.000","Title":"Quotations not working in PostgreSQL Queries","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I filled an Excel sheet with a correct float numbers based on the German decimal point format. So, the number 3.142 is correctly written 3,142, and if it is written 3.142 (or '3.142 by declaring it as a text entry in order to avoid English interpretation as 3142), then I want to report an error to the author of the Excel file.\nSo, I want to see a 3,142 in the first case when reading this file by openpyxl, and in the second case a 3.142 - just as writting by hand in Excel.\nHowever, I see 3.142 in both cases. What can I do?","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":549,"Q_Id":33263378,"Users Score":0,"Answer":"When it comes to value of numbers openpyxl doesn't care about their formatting so it will report 3142 in both cases. I don't think coercing this to a string makes any sense at all.","Q_Score":2,"Tags":"python,python-3.x,openpyxl","A_Id":33275544,"CreationDate":"2015-10-21T15:31:00.000","Title":"How to read a cell of a sheet filled with floats containing German decimal point","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have an EC2 instance and an S3 bucket in different region. The bucket contains some files that are used regularly by my EC2 instance.\nI want to programatically download the files on my EC2 instance (using python)\nIs there a way to do that?","AnswerCount":5,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":6069,"Q_Id":33298821,"Users Score":0,"Answer":"As mentioned above, you can do this with Boto. To make it more secure and not worry about the user credentials, you could use IAM to grant the EC2 machine access to the specific bucket only. Hope that helps.","Q_Score":5,"Tags":"python,amazon-web-services,amazon-s3,amazon-ec2,amazon-iam","A_Id":33375622,"CreationDate":"2015-10-23T09:17:00.000","Title":"Access to Amazon S3 Bucket from EC2 instance","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":1,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I create a database connection in the __init__ method of a Python class and want to make sure that the connection is closed on object destruction.\nIt looks like I can do this in __del__() or make the class a context manager and close the connection in __exit__(). I wonder which one is more Pythonic.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":523,"Q_Id":33306517,"Users Score":1,"Answer":"It looks like I can do this in __del__() or make the class a context manager and close the connection in __exit__(). I wonder which one is more Pythonic.\n\nI won't  comment on what's more \"pythonic\", since that is a highly subjective question.\nHowever, Python doesn't make very strict guarantees on when a destructor is called, making the context\/__exit__ approach the right one here.","Q_Score":1,"Tags":"python,database-connection,psycopg2","A_Id":33306596,"CreationDate":"2015-10-23T15:46:00.000","Title":"What's the preferred way to close a psycopg2 connection used by Python object?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"In my django application (django 1.8) I'm using two databases, one 'default' which is MySQL, and another one which is a schemaless, read-only database.\nI've two models which are accessing this database, and I'd like to exclude these two models permanently from data and schema migrations:\n\nmakemigrations should never detect any changes, and create migrations for them\nmigrate should never complain about missing migrations for that app\n\nSo far, I've tried different things, all without any success:\n\nused the managed=False Meta option on both Models\nadded a allow_migrate method to my router which returns False for both models\n\nDoes anyone have an example of how this scenario can be achieved?\nThanks for your help!","AnswerCount":3,"Available Count":2,"Score":0.1325487884,"is_accepted":false,"ViewCount":7061,"Q_Id":33385618,"Users Score":2,"Answer":"So far, I've tried different things, all without any success:\n\nused the managed=False Meta option on both Models\n\n\nThat option (the managed = False attribute on the model's meta options) seems to meet the requirements.\nIf not, you'll need to expand the question to say exactly what is special about your model that managed = False doesn't do the job.","Q_Score":17,"Tags":"python,django,django-models,django-migrations","A_Id":44014653,"CreationDate":"2015-10-28T07:53:00.000","Title":"django: exclude models from migrations","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"In my django application (django 1.8) I'm using two databases, one 'default' which is MySQL, and another one which is a schemaless, read-only database.\nI've two models which are accessing this database, and I'd like to exclude these two models permanently from data and schema migrations:\n\nmakemigrations should never detect any changes, and create migrations for them\nmigrate should never complain about missing migrations for that app\n\nSo far, I've tried different things, all without any success:\n\nused the managed=False Meta option on both Models\nadded a allow_migrate method to my router which returns False for both models\n\nDoes anyone have an example of how this scenario can be achieved?\nThanks for your help!","AnswerCount":3,"Available Count":2,"Score":0.0665680765,"is_accepted":false,"ViewCount":7061,"Q_Id":33385618,"Users Score":1,"Answer":"You have the correct solution:\n\nused the managed=False Meta option on both Models\n\nIt may appear that it is not working but it is likely that you are incorrectly preempting the final result when you see - Create model xxx for models with managed = False when running makemigrations.\nHow have you been checking\/confirming that migrations are being made?\nmakemigrations will still print to terminal - Create model xxx and create code in the migration file but those migrations will not actually result in any SQL code or appear in Running migrations: when you run migrate.","Q_Score":17,"Tags":"python,django,django-models,django-migrations","A_Id":68460381,"CreationDate":"2015-10-28T07:53:00.000","Title":"django: exclude models from migrations","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Well, I tried to understand Open Database Connectivity and Python DB-API, but I can't.\nODBC is some kind of standard and Python DB-API is another standard, but why not use just one standard? Or maybe I got these terms wrong.\nCan someone please explain these terms and the difference between them as some of the explanations I read were too technical?\nThank you","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":342,"Q_Id":33404837,"Users Score":1,"Answer":"There are other programming languages besides python -- java, javascript, ruby, perl, cobol, lisp, smalltalk, go, r, and many, many others. None of them can use the python db-api, but all of them could, potentially use odbc. Python offers odbc for people who come from other languages and already know odbc,and its own db-api for people who only know python and who aren't interested in learning the standard. Also, python db-api isn't really a standard, because it hasn't been accepted by any standards body (afaik)","Q_Score":1,"Tags":"database,odbc,python-db-api","A_Id":33404879,"CreationDate":"2015-10-29T02:15:00.000","Title":"Difference between ODBC and Python DB-API?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm trying to use PyMySQL on Ubuntu.\nI've installed pymysql using both pip and pip3 but every time I use import pymysql, it returns ImportError: No module named 'pymysql'\nI'm using Ubuntu 15.10 64-bit and Python 3.5.\nThe same .py works on Windows with Python 3.5, but not on Ubuntu.","AnswerCount":19,"Available Count":5,"Score":0.0,"is_accepted":false,"ViewCount":196169,"Q_Id":33446347,"Users Score":0,"Answer":"if you are using SPYDER IDE , just try to restart the console or restart the IDE, it works","Q_Score":69,"Tags":"python,python-3.x,ubuntu,pymysql","A_Id":59368220,"CreationDate":"2015-10-30T23:34:00.000","Title":"No module named 'pymysql'","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm trying to use PyMySQL on Ubuntu.\nI've installed pymysql using both pip and pip3 but every time I use import pymysql, it returns ImportError: No module named 'pymysql'\nI'm using Ubuntu 15.10 64-bit and Python 3.5.\nThe same .py works on Windows with Python 3.5, but not on Ubuntu.","AnswerCount":19,"Available Count":5,"Score":0.0,"is_accepted":false,"ViewCount":196169,"Q_Id":33446347,"Users Score":0,"Answer":"I had this same problem just now, and found the reason was my editor (Visual Studio Code) was running against the wrong instance of python; I had it set to run again python bundled with tensorflow, I changed it to my Anaconda python and it worked.","Q_Score":69,"Tags":"python,python-3.x,ubuntu,pymysql","A_Id":50157898,"CreationDate":"2015-10-30T23:34:00.000","Title":"No module named 'pymysql'","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm trying to use PyMySQL on Ubuntu.\nI've installed pymysql using both pip and pip3 but every time I use import pymysql, it returns ImportError: No module named 'pymysql'\nI'm using Ubuntu 15.10 64-bit and Python 3.5.\nThe same .py works on Windows with Python 3.5, but not on Ubuntu.","AnswerCount":19,"Available Count":5,"Score":0.0,"is_accepted":false,"ViewCount":196169,"Q_Id":33446347,"Users Score":0,"Answer":"sudo apt-get install python3-pymysql\nThis command also works for me to install the package required for Flask app to tun on ubuntu 16x with WISG module on APACHE2 server.\nBY default on WSGI uses python 3 installation of UBUNTU.\nAnaconda custom installation won't work.","Q_Score":69,"Tags":"python,python-3.x,ubuntu,pymysql","A_Id":49817699,"CreationDate":"2015-10-30T23:34:00.000","Title":"No module named 'pymysql'","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm trying to use PyMySQL on Ubuntu.\nI've installed pymysql using both pip and pip3 but every time I use import pymysql, it returns ImportError: No module named 'pymysql'\nI'm using Ubuntu 15.10 64-bit and Python 3.5.\nThe same .py works on Windows with Python 3.5, but not on Ubuntu.","AnswerCount":19,"Available Count":5,"Score":0.0,"is_accepted":false,"ViewCount":196169,"Q_Id":33446347,"Users Score":0,"Answer":"Just a note:\nfor Anaconda install packages command:\n\npython setup.py install","Q_Score":69,"Tags":"python,python-3.x,ubuntu,pymysql","A_Id":57734684,"CreationDate":"2015-10-30T23:34:00.000","Title":"No module named 'pymysql'","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm trying to use PyMySQL on Ubuntu.\nI've installed pymysql using both pip and pip3 but every time I use import pymysql, it returns ImportError: No module named 'pymysql'\nI'm using Ubuntu 15.10 64-bit and Python 3.5.\nThe same .py works on Windows with Python 3.5, but not on Ubuntu.","AnswerCount":19,"Available Count":5,"Score":0.0,"is_accepted":false,"ViewCount":196169,"Q_Id":33446347,"Users Score":0,"Answer":"I also got this error recently when using Anaconda on a Mac machine.\nHere is what I found:\n\nAfter running python3 -m pip install PyMySql, pymysql module is under \/Library\/Python\/3.7\/site-packages\nAnaconda wants this module to be under \/opt\/anaconda3\/lib\/python3.8\/site-packages\n\nTherefore, after copying pymysql module to the designated path, it runs correctly.","Q_Score":69,"Tags":"python,python-3.x,ubuntu,pymysql","A_Id":63201272,"CreationDate":"2015-10-30T23:34:00.000","Title":"No module named 'pymysql'","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am trying to read data from text file (which is output given by Tesseract OCR) and save the same in excel file. The problem i am facing here is the text files are in space separated format, and there are multiple files. Now i need to read all the files and save the same in excel sheet.\nI am using MATLAB to import and export data. I even thought of using python to convert the files into CSV format so that i can easily import the same in MATLAB and simply excelwrite the same. But no good solution.\nAny guidance would be of great help.\nthank you","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":212,"Q_Id":33479646,"Users Score":0,"Answer":"To read a text file in Matlab you can use fscanf or textscan then to export to excel you can use xlswrite that write directly to the excel file.","Q_Score":0,"Tags":"matlab,python-2.7,csv,export-to-csv","A_Id":33481202,"CreationDate":"2015-11-02T14:14:00.000","Title":"Importing data from text file and saving the same in excel","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Is it possible to insert many rows into a table using one query in pyhdb? Because when I have millions of records to insert, inserting each record in a loop is not very efficient.","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1564,"Q_Id":33514183,"Users Score":0,"Answer":"pyhdb executemany() is faster than simply execute()\nbut for larger records even if you divide in chunks and use executemany() it still takes significant time.\nFor better and faster performance use string formatting like values (?, ?, ?...) instead of values('%s', '%s', '%s', ...)\nThis saves a lots of time that heavy type conversion uses on server side and gets response faster and hence faster execution.","Q_Score":0,"Tags":"python,sap","A_Id":72168012,"CreationDate":"2015-11-04T05:15:00.000","Title":"How to insert many rows into a table using pyhdb?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"All of the MySql modules I've found are compatible with Python 2.7 or 3.4, but none with 3.5. Any way I can use a MySql module with the newest Python version?\nANSWER:\nThe regular Python versions of mysql-connector-python would not work, but the rf version did.\npython -m pip install mysql-connector-python-rf","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1498,"Q_Id":33524731,"Users Score":3,"Answer":"Python tries hard to be forward compatible.  A pure-python module written for 3.4 should work with 3.5; a binary package may work, you just have to try it and see.","Q_Score":3,"Tags":"mysql,python-3.x","A_Id":33524987,"CreationDate":"2015-11-04T14:45:00.000","Title":"Will a MySql module for Python 3.4 work with 3.5?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm using openpyxl to put data validation to all rows that have \"Default\" in them. But to do that, I need to know how many rows there are.\nI know there is a way to do that if I were using Iterable workbook mode, but I also add a new sheet to the workbook and in the iterable mode that is not possible.","AnswerCount":3,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":117258,"Q_Id":33541692,"Users Score":68,"Answer":"ws.max_row will give you the number of rows in a worksheet.\nSince version openpyxl 2.4 you can also access individual rows and columns and use their length to answer the question.\nlen(ws['A'])\nThough it's worth noting that for data validation for a single column Excel uses 1:1048576.","Q_Score":38,"Tags":"python,excel,openpyxl","A_Id":33543305,"CreationDate":"2015-11-05T10:06:00.000","Title":"How to find the last row in a column using openpyxl normal workbook?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am using sqlAlchemy to interact with a postgres database. It is all set to work with inserting string data. The data I receive is normally utf-8 and the setup works very well. As a edge case, recently, data came up in the format somedata\\xtrailingdata.\nSQLAlchemy is attempting to make this entry with somedata completely stripping out everything after \\x. \nCan you please tell me if there's a way to instruct SQLAlchemy to just attempt inserting the whole thing instead of removing the unicode part.\nI have attempted \ncreate_engine(dbUri, convert_unicode=True, client_encoding='utf8')\ncreate_engine(dbUri, convert_unicode=False, client_encoding='utf8')\ncreate_engine(dbUri, convert_unicode=False)\nNone worked out so far. I really would appreciate your input in inserting this data into string column.\nPS:Can't modify the column type of DB. This is a very edge case, not the norm.","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":442,"Q_Id":33665544,"Users Score":0,"Answer":"There's nothing Unicode about it. \\x is a byte literal prefix and requires a hex value to follow. PostgreSQL also supports the \\x syntax also, so it may be PostgreSQL that's dropping it. \nConsider escaping all slashes or find-replace on \\x before handing to SQLAlchemy","Q_Score":0,"Tags":"python,postgresql,utf-8,sqlalchemy,unicode-string","A_Id":33685308,"CreationDate":"2015-11-12T06:27:00.000","Title":"Inserting unicode into string with sqlAlchemy","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am using sqlAlchemy to interact with a postgres database. It is all set to work with inserting string data. The data I receive is normally utf-8 and the setup works very well. As a edge case, recently, data came up in the format somedata\\xtrailingdata.\nSQLAlchemy is attempting to make this entry with somedata completely stripping out everything after \\x. \nCan you please tell me if there's a way to instruct SQLAlchemy to just attempt inserting the whole thing instead of removing the unicode part.\nI have attempted \ncreate_engine(dbUri, convert_unicode=True, client_encoding='utf8')\ncreate_engine(dbUri, convert_unicode=False, client_encoding='utf8')\ncreate_engine(dbUri, convert_unicode=False)\nNone worked out so far. I really would appreciate your input in inserting this data into string column.\nPS:Can't modify the column type of DB. This is a very edge case, not the norm.","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":442,"Q_Id":33665544,"Users Score":0,"Answer":"The problem turned out to be \\x00. When passed to SQLAlchemy an a value with \\x00, it truncates it to the data preceding \\x00. We traced the problem to the C library underneath the SQLAlchemy.","Q_Score":0,"Tags":"python,postgresql,utf-8,sqlalchemy,unicode-string","A_Id":34233985,"CreationDate":"2015-11-12T06:27:00.000","Title":"Inserting unicode into string with sqlAlchemy","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Ubuntu python2 and python3 both can import sqlite3, but I can not type sqlite3 in command prompt to open it, it said sqlite3 is not installed, if i want to use it out of python should I install sqlite3 solely using apt-get or I can find it in some directory of python, add it to path and use directly in command line.\nI also installed python3.5 on mac, the mac shipped with python2, and I can use sqlite3 in the command line by type sqlite3, it is version 3.8.10.2, seems installed by python2, but the python3.5 installed a different version of sqlite3, where can I find it?","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":16159,"Q_Id":33691635,"Users Score":0,"Answer":"Any Cygwin users who find themselves here: run the Cygwin installation .exe... \nChoose \"Categories\", \"Database\", and then one item says \"sqlite3 client to access sqlite3 databases\", or words to that effect.","Q_Score":1,"Tags":"python,python-3.x,sqlite","A_Id":48045704,"CreationDate":"2015-11-13T11:23:00.000","Title":"How to open sqlite3 installed by Python 3?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am trying to reinstall one of my apps on my project site. These are the steps that I have followed to do so:\n\nRemoving the name of the installed app from settings.py\nManually deleting the app folder from the project folder\nManually removing the data tables from PostgreSQL\nCopying the app folder back into the project folder; making sure that all files, except __init__.py is removed. \nRun python manage.py sqlmigrate app_name 0001\nRun python manage.py makemigrations app_name\nRun python manage.py migrate app_name\nRun python manage.py makemigrations\nRun python manage.py migrate\n\nHowever, after all these steps the message I am getting is that there are \"no changes detected\" and the data tables have not been recreated in the database, PostgreSQL. \nAm I missing some additional steps?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":205,"Q_Id":33703866,"Users Score":0,"Answer":"I think I might have managed to solve the problem. The command, python manage.py sqlmigrate app_name 0001, produces the SQL statements required for the table creation. Thus, I copied and paste the output into the PostgreSQL console and got the tables created. It seems to work for now, but I am not sure if there will be repercussions later.","Q_Score":1,"Tags":"python,django","A_Id":33704110,"CreationDate":"2015-11-14T00:37:00.000","Title":"Reinstalling Django App - Data tables not re-created","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I would like to push sensor data from the raspberry pi to localhost phpmyadmin. I understand that I can install the mysql and phpmyadmin on the raspberry pi itself. But what I want is to access my local machine's database in phpmyadmin from the raspberry pi. Would it be possible?","AnswerCount":2,"Available Count":2,"Score":0.0996679946,"is_accepted":false,"ViewCount":1407,"Q_Id":33704183,"Users Score":1,"Answer":"Well, from what I understand, you'd like to save the sensor data arriving in your Raspberry Pi to a database and access it from another machine. What I suggest is, install a mysql db instance and phpmyadmin in your Raspberry Pi and you can access phpmyadmin from another machine in the network by using the RPi's ip address.\nHope this is what you wanted to do.","Q_Score":0,"Tags":"mysql,python-2.7,phpmyadmin,raspberry-pi2","A_Id":33705227,"CreationDate":"2015-11-14T01:29:00.000","Title":"Push sensor data from raspberry pi to local host phpmyadmin database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I would like to push sensor data from the raspberry pi to localhost phpmyadmin. I understand that I can install the mysql and phpmyadmin on the raspberry pi itself. But what I want is to access my local machine's database in phpmyadmin from the raspberry pi. Would it be possible?","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":1407,"Q_Id":33704183,"Users Score":0,"Answer":"Sure, as long as they're on the same network and you have granted proper permission, all you have to do is use the proper hostname or IP address of the MySQL server (what you call the local machine). In whatever utility or custom script you have that writes data, use the networked IP address instead of 127.0.0.1 or localhost for the database host.\nDepending on how you've installed MySQL, you may not have a user that listens for non-local connections, incoming MySQL connections may be blocked at the firewall, or your MySQL server may not listen for incoming network connections.\nYou've asked about using phpMyAdmin from the Pi, accessing your other computer, which doesn't seem to make much sense to me (I'd think you'd want to run phpMyAdmin on your desktop computer, not a Pi), but if you've got a GUI and compatible web browser running on the Pi then you'd just have phpMyAdmin and the webserver run on the same desktop computer that has MySQL and access that hostname and folder from the Pi (such as http:\/\/192.0.2.15\/phpmyadmin).\nIf you're planning to make the MySQL server itself public-facing, you should really re-think that decision unless you know why that's a bad idea and how to properly secure it (but that may not be a concern; for instance I have one at home that is available on the local network, but my router blocks any incoming connections from external sources).","Q_Score":0,"Tags":"mysql,python-2.7,phpmyadmin,raspberry-pi2","A_Id":33716584,"CreationDate":"2015-11-14T01:29:00.000","Title":"Push sensor data from raspberry pi to local host phpmyadmin database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"can I store PDF files in the database, as object or blob, with Flask-Admin?\nI do not find any reference in the documentation.\nThanks.\nCheers","AnswerCount":2,"Available Count":1,"Score":-0.1973753202,"is_accepted":false,"ViewCount":3809,"Q_Id":33722132,"Users Score":-2,"Answer":"Flask-Admin doesn't store anything. It's just a window into the underlying storage.\nSo yes, you can have blob fields in a Flask-Admin app -- as long as the engine of your database supports blob types.\nIn case further explanation is needed, Flask-Admin is not a database. It is an interface to a database. In a flask-admin app, you connect to a pre-existing database. This might be an sqlite database, PostGresSQL, MySQL, MongoDB or any of a variety of databases.","Q_Score":2,"Tags":"python,mongodb,object,flask-sqlalchemy,flask-admin","A_Id":33724438,"CreationDate":"2015-11-15T16:40:00.000","Title":"Storing a PDF file in DB with Flask-admin","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Is it possible to use same formatting variable for formatting multiple excel workbooks using xlsxwriter? If yes, how? Currently I am able to use formatting variable for single excel workbook as I am initializing it using workbook.add_format method but this variable is bounded to that workbook only.","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":56,"Q_Id":33749918,"Users Score":1,"Answer":"Is it possible to use same formatting variable for formatting multiple excel workbooks using xlsxwriter? \n\nNo.\nA formatting object is created by and thus, tied to, a workbook object.\nHowever, there are other ways of doing what you need to do such as storing the properties for the format in a dict and using that to initialize several format objects in the same way.","Q_Score":1,"Tags":"python,format,xlsxwriter","A_Id":33751625,"CreationDate":"2015-11-17T05:39:00.000","Title":"Use same formatting variable for multiple Excel workbooks","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a database in MS Access. I am trying to query one table to Python using pypyodbc. I get the following error message:\n\nValueError: could not convert string to float: E+6\n\nThe numbers in the table are fairly big, with up to ten significant figures. The error message tells me that MSAccess is formatting them in scientific notation and Python is reading them as strings.\nThe fields in the table are formatted as singles with two decimal places. When I see the numbers in the table in the database they are not formatted using scientific notation. but the error message seems to indicate that they are. \nFurthermore, if I change the numbers in the table (at lest for a test row) to small numbers (integers from 1 to 5) the query runs. Which supports my theory that the problem is scientific formatting of big number. \nAny ideas of how to:\n\nwrite into the database table in a way that the numbers are not formatted in scientific notation, or\nmake pypyodbc retrieve numbers as such and ignore any scientific notation.","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1522,"Q_Id":33769143,"Users Score":0,"Answer":"As I was putting together test files for you to try to reproduce, I noticed that two of the fields in the table were set to Single type rather than Double. Changed them to Double and that solved the problem.\nSorry for the bother and thanks for the help.","Q_Score":3,"Tags":"python,ms-access,pypyodbc","A_Id":33894451,"CreationDate":"2015-11-17T23:35:00.000","Title":"Issue querying from Access database: \"could not convert string to float: E+6\"","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm using Sql alchemy with Sql Server as database engine. I have queries that take long time (approximately 10 second). When I send concurrent requests to database, the response time takes more (Exactly, time = execution time * requests count). I Increased the connection pool but no changes have been happend.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":403,"Q_Id":33775269,"Users Score":1,"Answer":"if the issue is only with threads and not concurrent processes then the\nDBAPI in use would be suspect.  I don't see which driver you are using\nbut perhaps it is not releasing the GIL while it waits for a server\nresponse. produce a test case that isolates it just to that driver running in two threads, and then report\nit as a bug on their system.","Q_Score":2,"Tags":"python,sql-server,sqlalchemy","A_Id":33991887,"CreationDate":"2015-11-18T08:41:00.000","Title":"SQL alchemy is slow in concurrent connection","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a Python program that connects to an MSSQL database using an ODBC connection. The Python library I'm using is pypyodbc.\nHere is my setup:\n\nWindows 8.1 x64\nSQL Server 2014 x64\nPython 2.7.9150\nPyPyODBC 1.3.3\nODBC Driver: SQL Server Native Client 11.0\n\nThe problem I'm having is that when I query a table with a varchar(max) column, the content is being truncated.\nI'm new to pypyodbc and I've been searching around like crazy and can't find anything on how to prevent this from happening in pypyodbc or even pyodbc. At least not with the search terms I've been using and I don't know what other phrases to try.\nI even tried adding SET TEXTSIZE 2147483647; to my SQL query, but the data is still being truncated.\nHow do I prevent this from happening? Or can you point me in the right direction, please?\nUPDATE:\nSo, I tried performing a cast in my SQL query. When I do CAST(my_column as VARCHAR(MAX)) it truncates at the same position. However, if I do CAST(my_column as VARCHAR(8000)) it gives me a larger set of the text, but it's still truncating some of the contents. If I try to do anything larger than 8000 I get an error saying that 8000 is the largest I can use. Anyone know what might be going on here? It seem strange that using MAX won't work.","AnswerCount":3,"Available Count":1,"Score":1.0,"is_accepted":false,"ViewCount":5189,"Q_Id":33878291,"Users Score":8,"Answer":"The \"{SQL Server}\" doesn't work in my case. \"{SQL Server}\" works perfectly well if the database is on my local machine. However, if I tried to connect to the remote server, always the error message below would return:\npypyodbc.DatabaseError: ('08001', '[08001] [Microsoft][ODBC SQL Server Driver][DBNETLIB]SSL Security error')\nFor those who are still struggling in the VARCHAR(MAX) truncation, a brilliant workaround my colleague came out with is to CAST the VARCHAR(MAX) to TEXT type. \nLet's say we have a column called note and its data type is VARCHAR(MAX), instead of using SELECT note FROM notebook, writing in SELECT CAST(note AS TEXT) FROM notebook.\nHope it helps!","Q_Score":8,"Tags":"python,sql-server,pyodbc,pypyodbc","A_Id":53201310,"CreationDate":"2015-11-23T18:45:00.000","Title":"How to get entire VARCHAR(MAX) column with Python pypyodbc","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have 2 different python processes (running from 2 separate terminals) running separately at the same time accessing and updating mysql. It crashes when they are using same table at the same time. Any suggestions on how to fix it?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":41,"Q_Id":33909039,"Users Score":0,"Answer":"Are you using myisam or innodb?  I suggest using innodb since it has a better table\/record locking flexibility for multiple simultaneous updates.","Q_Score":0,"Tags":"python,mysql,python-2.7,mysql-python","A_Id":34680890,"CreationDate":"2015-11-25T05:26:00.000","Title":"python accessing and updating mysql from simultaneously running processes","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I want to connect my project from app engine with (googleSQL), but I get that error exceeded the maximum of 12 connections in python, I have a CLOUDSQL D8 1000 simultaneous connections\nhow can i change this number limit conexions, I'm using django and python\nthanks","AnswerCount":1,"Available Count":1,"Score":0.3799489623,"is_accepted":false,"ViewCount":223,"Q_Id":33977130,"Users Score":2,"Answer":"Each single app engine instance can have no more than 12 concurrent connections to Cloud SQL -- but then, by default, an instance cannot service more than 8 concurrent requests, unless you have deliberately pushed that up by setting the max_concurrent_requests in the automatic_scaling stanza to a higher value.\nIf you've done that, then presumably you're also using a hefty instance_class in that module (perhaps the default module), considering also that Django is not the lightest-weight or fastest of web frameworks;  an F4 class, I imagine. Even so, pushing max concurrent requests above 12 may result in latency spikes, especially if serving each and every request also requires other slow, heavy-weight operations such as MySQL ones.\nSo, consider instead using many more instances, each of a lower (cheaper) class, serving no more than 12 requests each (again, assuming that every request you serve will require its own private connection to Cloud SQL -- pooling those up might also be worth considering). For example, an F2 instance costs, per hour, half as much as an F4 one -- it's also about half the power, but, if serving half as many user requests, that should be OK.\nI presume, here, that all you're using those connections for is to serve user requests (if not, you could dispatch other, \"batch-like\" uses to separate modules, perhaps ones with manual or basic scheduling -- but, that's another architectural issue).","Q_Score":0,"Tags":"python,google-app-engine,google-cloud-sql","A_Id":33978178,"CreationDate":"2015-11-28T22:26:00.000","Title":"As codified the limit of 12 connections appengine to cloudsql","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I'm self-teaching programming through the plethora of online resources to build a startup idea I've had for awhile now. Currently, I'm using the SaaS platform at sharetribe.com for my business but I'm trying to build my own platform as share tribe does not cater to the many options I'd like to have available to my users. \nI'm try to setup the database at this time and I'm currently working on the architecture. I plan to use MySQL for my database.\nThe website will feature an online inventory management system where users can track all their items, update availability, pricing, delivery, payments, analytical tools, etc. This is so the user can easily monitor their current items, create new listings, etc. so it creates more of a \"business\" feel for the users. \nHere is a simple explanation of the work flow. Users will create their profile having access to rent or rent out their items. Once their account is created they can search listing based on the category, subcategory, location, price, etc. When rental is placed, the user will request the rental at specified time, once approved, the rental process will begin. \nMy question is how should I set up the infrastructure\/architecture for the database? I have this as my general workings but I know I'm missing a lot of queries and criteria to suit the application. \nUser queries:\n-user_ID\n-name\n-email\n-username\n-encrypted_password\n-location\n-social_media\n-age\n-photo\nProduct queries:\n-item_ID\n-user_ID\n-category_ID\n-subcategory_ID\n-price\n-description\n-availability\n-delivery_option\nAs you can see, I'm new to this but as many of the resources I've used for my research, all have said the best way to learn is to do. I'm probably taking on a bigger project that I should for my beginning stages but there will be plenty of mistakes made that will assist my learning. \nAny and all recommendations and assistance are appreciated. \nFor general knowledge, I intend to utilize Rails as my server language. If you recommend Python\/Django over Ruby\/Rails, could you please explain why this would be more beneficial to me? \nThanks.","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":657,"Q_Id":34129887,"Users Score":0,"Answer":"Learn a good book on software development methodologies before you get into this . Then read some simple tutorial online on mysql . Then it will be a lot more easy to do this .","Q_Score":0,"Tags":"python,mysql,ruby-on-rails,ruby,database","A_Id":34133045,"CreationDate":"2015-12-07T09:07:00.000","Title":"How do I build the database for my P2P rental marketplace?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"We are developing a b2b application with django. For each client, we launch a new virtual server machine and a database. So each client has a separate installation of our application. (We do so because by the nature of our application, one client may require high use of resources at certain times, and we do not want one client's state to affect the others)\nEach of these installations are binded to a central repository. If we update the application code, when we push to the master branch, all installations detect this, pull the latest version of the code and restart the application.\nIf we update the database schema on the other hand, currently, we need to run migrations manually by connecting to each db instance one by one (settings.py file reads the database settings from an external file which is not in the repo, we add this file manually upon installation). \nCan we automate this process? i.e. given a list of databases, is it possible to run migrations on these databases with a single command?","AnswerCount":2,"Available Count":2,"Score":0.0996679946,"is_accepted":false,"ViewCount":510,"Q_Id":34197011,"Users Score":1,"Answer":"First, I'd really look (very hard) for a way to launch a script that does as masnun suggests on the client side, really hard.\nSecond, if that does not work, then I'd try the following:\n\nConfigure on your local machine all client databases in the settings variable DATABASES\nMake sure you can connect to all the client databases, this may need some fiddling\nThen you run the \"manage.py migrate\" process with the extra flag --database=mydatabase (where \"mydatabase\" is the handle provided in the configuration) for EACH client database\n\nI have not tried this, but I don't see why it wouldn't work ...","Q_Score":1,"Tags":"python,django,django-migrations","A_Id":34878492,"CreationDate":"2015-12-10T08:32:00.000","Title":"Running django migrations on multiple databases simultaneously","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"We are developing a b2b application with django. For each client, we launch a new virtual server machine and a database. So each client has a separate installation of our application. (We do so because by the nature of our application, one client may require high use of resources at certain times, and we do not want one client's state to affect the others)\nEach of these installations are binded to a central repository. If we update the application code, when we push to the master branch, all installations detect this, pull the latest version of the code and restart the application.\nIf we update the database schema on the other hand, currently, we need to run migrations manually by connecting to each db instance one by one (settings.py file reads the database settings from an external file which is not in the repo, we add this file manually upon installation). \nCan we automate this process? i.e. given a list of databases, is it possible to run migrations on these databases with a single command?","AnswerCount":2,"Available Count":2,"Score":0.2913126125,"is_accepted":false,"ViewCount":510,"Q_Id":34197011,"Users Score":3,"Answer":"If we update the application code, when we push to the master branch,\n  all installations detect this, pull the latest version of the code and\n  restart the application.\n\nI assume that you have some sort of automation to pull the codes and restart the web server. You can just add the migration to this automation process. Each of the server's settings.py would read the database details from the external file and run the migration for you. \nSo the flow should be something like: \n\nPull the codes\nMigrate \nCollect Static\nRestart the web server","Q_Score":1,"Tags":"python,django,django-migrations","A_Id":34197250,"CreationDate":"2015-12-10T08:32:00.000","Title":"Running django migrations on multiple databases simultaneously","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Python, Twistd and SO newbie.\nI am writing a program that organises seating across multiple rooms.  I have only included related columns from the tables below.\nBasic Mysql tables\nTable\n\nid \n\nSeat\n\nid\ntable_id\nname\n\nCard\n\nseat_id\n\nThe Seat and Table tables are pre-populated with the 'name' columns initially NULL.\nStage One \nI want to update a seat's name by finding the first available seat given a group of table ids.\nStage Two\nI want to be able to get the updated row id from Stage One (because I don't already know this) to add to the Card table.  Names can be assigned to more than one seat so I can't just find a seat that matches a name.\nI can do Stage One but have no idea how to do Stage Two because lastrowid only works for inserts not updates.\nAny help would be appreciated.\nUsing twisted.enterprise.adbapi if that helps.\nCheers","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":311,"Q_Id":34213706,"Users Score":0,"Answer":"I think the best way to accomplish this is to first make a select for the id (or ids) of the row\/rows you want to update, then update the row with a WHERE condition matching the id of the item to update. That way you are certain that you only updated the specific item.\nAn UPDATE statement can update multiple rows that matches your criteria. That is why you cannot request the last updated id by using a built in function.","Q_Score":3,"Tags":"python,mysql,twisted","A_Id":35131551,"CreationDate":"2015-12-10T23:32:00.000","Title":"Python Twistd MySQL - Get Updated Row id (not inserting)","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":0},{"Question":"I have a python code which needs to retrieve and store data to\/from a database on a LAMP server. The LAMP server and the device running the python code are never on the same internet network. The devices running the python code can be either a Linux, Windows or a MAC system. Any idea how could I implement this?","AnswerCount":1,"Available Count":1,"Score":-0.1973753202,"is_accepted":false,"ViewCount":155,"Q_Id":34242017,"Users Score":-1,"Answer":"are never on the same internet network.\n\nLet me clear the question, the problem is are never on the same internet network. firstly you need to fix the network issue, add router between the two sides which you want to communicate with. No relations with Python or LAMP.\n\nlet me assume your DB is mysql, if you can make you can access that DB from outside servers, you can just talk with that DB directly from another servers. \nbut for another solution, I recommend you to use API which would cover all request above the DB, then you can talk with that API to handle the data.","Q_Score":0,"Tags":"python,mysql,database,lamp,mysql-python","A_Id":34242082,"CreationDate":"2015-12-12T16:11:00.000","Title":"How to fetch or store data into a database on a LAMP server from devices over the internet?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"As the title says, I\u2019 am trying to run Flask alongside a PHP app.\nBoth of them are running under Apache 2.4 on Windows platform. For Flask I\u2019m using wsgi_module.\nThe Flask app is actually an API. The PHP app controls users login therefore users access to API. Keep in mind that I cannot drop the use of the PHP app because it controls much more that the logging functionality [invoicing, access logs etc].\nThe flow is:\n\nUser logs in via PHP app\nPHP stores user data to a database [user id and a flag indicating if user is logged in]\nUser makes a request to Flask API\nFlask checks if user data are in database: If not, redirects to PHP login page, otherwise let user use the Flask API.\n\nI know that between steps 2 and 3, PHP have to share a session variable-cookie [user id] with Flask in order Flask app to check if user is logged in.\nWhatever I try fails. I cannot pass PHP session variables to Flask. \nI know that I can\u2019t pass PHP variables to Flask, but I\u2019m not sure for that.\nHas anyone tried something similar? \nWhat kind of user login strategy should I implement to the above setup?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1770,"Q_Id":34266083,"Users Score":1,"Answer":"I'm not sure this is the answer you are looking for, but I would not try to have the Flask API access session data from PHP. Sessions and API do not go well together, a well designed API does not need sessions, it is instead 100% stateless.\nWhat I'm going to propose assumes both PHP and Flask have access to the user database. When the user logs in to the PHP app, generate an API token for the user. This can be a random sequence of characters, a uuid, whatever you want, as long as it is unique. Write the token to the user database, along with an expiration date if you like. The login process should pass that token back to the client (use https:\/\/, of course).\nWhen the client needs to make an API call, it has to send that token in every request. For example, you can include it in the Authorization header, or you can use a custom header as well. The Flask API gets the token and searches the user database for it. If it does not find the token, it returns 401. If the token is found, it now knows who the user is, without having to share sessions with PHP. For the API endpoints you will be looking up the user from the token for every request.\nHope this helps!","Q_Score":2,"Tags":"php,python,session,flask","A_Id":34272457,"CreationDate":"2015-12-14T11:37:00.000","Title":"Run Flask alongside PHP [sharing session]","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I need to create random entries with a given sql-schema in sql with the help of python programming language.\nIs there a simple way to do that or do I have to write own generators?","AnswerCount":3,"Available Count":1,"Score":0.0665680765,"is_accepted":false,"ViewCount":1307,"Q_Id":34301518,"Users Score":1,"Answer":"You can also use faker.\njust pip install faker\nJust go through documentation and check it out","Q_Score":0,"Tags":"python,sql,generator","A_Id":63923673,"CreationDate":"2015-12-15T23:38:00.000","Title":"How to create random entries in database with python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have created groups to give access rights everything seems fine but I want to custom access - rights for module issue. When user of particular group logins, I want that user only able to create\/edit their own issue and can't see other users issue.Please help me out!!\nThanks","AnswerCount":2,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":6109,"Q_Id":34327655,"Users Score":2,"Answer":"Providing access rule is one part of the solution. If you look at \"Access Control List\" in \"Settings > Technical > Security > Access Controls Lists\", you can see that the group Hr Employee has only read access to the model hr.employee. So first you have to provide write access also to model hr.employee for group Employee. After you have allowed write access to the group Employee for model hr.employee,\n\nCreate a new record rule from Settings > Technical > Security > Record Rules named User_edit_own_employee_rule (As you wish).\nProvide domain for this group User_edit_own_employee_rule as [('user_id', '=', user.id)]. And this domain should apply for Read and Write. ie; by check \"Apply for Read\" and \"Apply for Write\" Boolean field.\nCreate another record rule named User_edit_own_employee_rule_1\nProvide domain for this group User_edit_own_employee_rule as [('user_id', '!=', user.id)]. And this domain should apply for Read only. ie; check \"Apply for Read\".\n\nNow by creating two record rule for the group Employee, we can provide access to read and write his\/her own record but only to read other employee records.\nDetail:\nProvide write access in access control list to model hr.employee for group Employee. Create two record rule:\nUser_edit_own_employee_rule :\n\nName : User_edit_own_employee_rule\nObject : Employee\nApply for Read : Checked\nApply for Write : Checked\nRule Definition : [('user_id', '=', user.id)]\nGroups : Human Resources \/ Employee\n\nUser_edit_own_employee_rule_1 :\n\nName : User_edit_own_employee_rule_1\nObject : Employee\nApply for Read : Checked\nApply for Write : Un Checked\nRule Definition : [('user_id', '!=', user.id)]\nGroups : Human Resources \/ Employee\n\nI hope this will help you.","Q_Score":0,"Tags":"python,xml,openerp","A_Id":34328053,"CreationDate":"2015-12-17T06:03:00.000","Title":"How to make user can only access their own records in odoo?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"MySQLdb as I understand doesn't support Python 3. I've heard about PyMySQL as a replacement for this module. But how does it work in production environment?\nIs there a big difference in speed between these two? I asking because I will be managing a very active webapp that needs to create entries in the database very often.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":79,"Q_Id":34341489,"Users Score":3,"Answer":"PyMySQL is a pure-python database connector for MySQL, and can be used as a drop-in replacement using the install_as_MySQLdb() function. As a pure-python implementation, it will have some more overhead than a connector that uses C code, but it is compatible with other versions of Python, such as Jython and PyPy. \nAt the time of writing, Django recommends to use the mysqlclient package on Python 3. This fork of MySQLdb is partially written in C for performance, and is compatible with Python 3.3+. You can install it using pip install mysqlclient. As a fork, it uses the same module name, so you only have to install it and Django will use it in its MySQL database engine.","Q_Score":0,"Tags":"python,django,python-3.x","A_Id":34341868,"CreationDate":"2015-12-17T18:13:00.000","Title":"MySQL module for Python 3","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I can't connect to a DB2 remote server using Python. Here is what I've done:\n\nCreated a virtualenv with Python 2.7.10 (On Mac OS X 10.11.1)\ninstalled ibm-db using sudo pip install ibm_db\nRan the following code:\nimport ibm_db\n  ibm_db.connect(\"my_connection_string\", \"\", \"\")\n\nI then get the following error:\n\nException: [IBM][CLI Driver] SQL1042C  An unexpected system error\n  occurred.  SQLSTATE=58004 SQLCODE=-1042\n\nI've googled around for hours and trying out different solutions. Unfortunately, I haven't been able to find a proper guide for setting the environment up on Mac OS X + Python + DB2.","AnswerCount":3,"Available Count":1,"Score":0.0665680765,"is_accepted":false,"ViewCount":2550,"Q_Id":34436084,"Users Score":1,"Answer":"We are able to install the driver successfully and connection to db is established without any problem.\nThe steps are:\n1) Upgraded to OS X El Capitan\n2) Install pip - sudo pip install\n3) Install ibm_db  - sudo pip install ibm_db \n4) During installation, below error was hit\nReferenced from: \/Users\/roramana\/Library\/Python\/2.7\/lib\/python\/site-packages\/ibm_db.so\n  Reason: unsafe use of relative rpath libdb2.dylib in \/Users\/roramana\/Library\/Python\/2.7\/lib\/python\/site-packages\/ibm_db.so with restricted binary\nAfter disabling the System Integrity Protection, installation went fine.\nFrom the error sql1042c, it seems like you are hitting some environment setup issue.\nYou could try setting DYLD_LIBRARY_PATH to the path where you have extracted the odbc and cli driver .\nIf the problem still persist, please collect db2 traces and share with us:\ndb2trc on -f trc.dmp\nrun your repro\ndb2trc off\ndb2trc flw trc.dmp trc.flw\ndb2trc fmt trc.dmp trc.fmt\nShare the trc.flw and trc.fmt files.","Q_Score":1,"Tags":"python,db2,dashdb","A_Id":34651608,"CreationDate":"2015-12-23T12:48:00.000","Title":"Can't connect to DB2 Driver through Python: SQL1042C","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":0},{"Question":"I am working on scaling out a webapp and providing some database redundancy for protection against failures and to keep the servers up when updates are needed. The app is still in development, so I have chosen a simple multi-master redundancy with two separate database servers to try and achieve this. Each server will have the Django code and host its own database, and the databases should be as closely mirrored as possible (updated within a few seconds).\nI am trying to figure out how to set up the multi-master (master-master) replication between databases with Django and MySQL. There is a lot of documentation about setting it up with MySQL only (using various configurations), but I cannot find any for making this work from the Django side of things.\nFrom what I understand, I need to approach this by adding two database entries in the Django settings (one for each master) and then write a database router that will specify which database to read from and which to write from. In this scenario, both databases should accept both reads and writes, and writes\/updates should be mirrored over to the other database. The logic in the router could simply use a round-robin technique to decide which database to use. From there on, further configuration to set up the actual replication should be done through MySQL configuration.\nDoes this approach sound correct, and does anyone have any experience with getting this to work?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1628,"Q_Id":34468030,"Users Score":0,"Answer":"Your idea of the router is great! I would add that you need automatically detect whether a databases is [slow] down. You can detect that by the response time and by connection\/read\/write errors. And if this happens then you exclude this database from your round-robin list for a while, trying to connect back to it every now and then to detect if the databases is alive.\nIn other words the round-robin list grows and shrinks dynamically depending on the health status of your database machines.\nThe another important notice is that luckily you don't need to maintain this round-robin list common to all the web servers. Each web server can store its own copy of the round-robin list and its own state of inclusion and exclusion of databases into this list. This is just because a database server can be seen from one web server and can be not seen from another one due to local network problems.","Q_Score":0,"Tags":"python,mysql,django,multi-master-replication","A_Id":34841926,"CreationDate":"2015-12-26T02:34:00.000","Title":"Multi-master database replication with Django webapp and MySQL","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a Django app with a postgres backend hosted on Heroku. I'm now migrating it to Azure. On Azure, the Django application code and postgres backend have been divided over two separate VMs. \nEverything's set up, I'm now at the stage where I'm transferring data from my live Heroku website to Azure. I downloaded a pg_dump to my local machine, transferred it to the correct Azure VM, ran syncdb and migrate, and then ran pg_restore --verbose --clean --no-acl --no-owner -U myuser -d mydb latest.dump. The data got restored (11 errors were ignored, pertaining to 2 tables that get restored, but which my code now doesn't use).\nWhen I try to access my website, I get the kind of error that usually comes in my website if I haven't run syncdb and migrate: \n\nException Type:   DatabaseError Exception Value:  \nrelation \"user_sessions_session\" does not exist LINE 1:\n  ...last_activity\", \"user_sessions_session\".\"ip\" FROM \"user_sess...\n                                                               ^\nException Location:\n    \/home\/myuser\/.virtualenvs\/myenv\/local\/lib\/python2.7\/site-packages\/django\/db\/backends\/postgresql_psycopg2\/base.py\n  in execute, line 54\n\nCan someone who has experienced this before tell me what I need to do here? It's acting as if the database doesn't exist and I had never run syncdb. When I use psql, I can actually see the tables and the data in them. What's going on? Please advise.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":119,"Q_Id":34472609,"Users Score":1,"Answer":"Try those same steps WITHOUT running syncdb and migrate\u00a0at all. So overall, your steps will be:\nheroku pg:backups capture\ncurl -o latest.dump heroku pg:backups public-url\n`scp -P  latest.dump myuser@example.cloudapp.net:\/home\/myuser\ndrop database mydb;\ncreate database mydb;\npg_restore --verbose --clean --no-acl --no-owner -U myuser -d mydb latest.dump","Q_Score":0,"Tags":"python,django,database,postgresql,database-migration","A_Id":34480125,"CreationDate":"2015-12-26T15:18:00.000","Title":"Unable to correctly restore postgres data: I get the same error I usually get if I haven't run syncdb and migrate","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Edited to clarify my meaning:\nI am trying to find a method using a Django action to take data from one database table and then process it into a different form before inserting it into a second table. I am writing a kind of vocabulary dictionary which extracts data about students' vocabulary from their classroom texts. To do this I need to be able to take the individual words from the table field containing the content and then insert the words into separate rows in another table. I have already written the code to extract the individual words from the record in the first database table, I just need a method for putting it into a second database table as part of the same Django action.\nI have been searching for an answer for this, but it seems Django actions are designed to handle the data for only one database table at a time. I am considering writing my own MySQL connection to inject the words into the second table in the database. I thought I would write here first though to see if anyone knows if I am missing a built-in way to do this in Django.","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":884,"Q_Id":34477062,"Users Score":1,"Answer":"I am pretty sure there is no built-in way for something this specific. Finding single words in a text alone is a quite complex task if you take into consideration misspelled words, hyphen-connected words, quotes, all sorts of punctuation and unicode letters.\nYour best bet would be using a regex for each text and save the matches on a second model manually.","Q_Score":0,"Tags":"python,mysql,django","A_Id":34477438,"CreationDate":"2015-12-27T02:18:00.000","Title":"Django way to modify a database table using the contents of another table","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am using MongoVue and Python library Pymongo to insert some documents. I used MongoVue to see the db created. It was not listed. However, I made a find() request in shell. I got all the inserted documents. \nOnce I manually create DB all the inserted documents appears then.Every other db's inside the localhost is not affected.\nWhat is the reason for this behaviour?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":117,"Q_Id":34488751,"Users Score":0,"Answer":"So, found out the fix for this behavior. Refreshing in MongoVue didn't work. So, I had to close it and open the MongoVue again to see the newly created collections.","Q_Score":0,"Tags":"python-2.7,mongovue,pymongo-2.x","A_Id":37524187,"CreationDate":"2015-12-28T06:35:00.000","Title":"Database is not appearing in MongoVue","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am using pymongo driver to work with Mongodb using Python. Every time when I run a query in python shell, it returns me some output which is very difficult to understand. I have used the .pretty() option with mongo shell, which gives the output in a structured way. \nI want to know whether there is any method like pretty() in pymongo, which can return output in a structured way ?","AnswerCount":5,"Available Count":1,"Score":-0.0399786803,"is_accepted":false,"ViewCount":4368,"Q_Id":34493535,"Users Score":-1,"Answer":"It probably depends on your IDE, not the pymongo itself. the pymongo is responsible for manipulating data and communicating with the mongodb. I am using Visual Studio with PTVS and I have such options provided from the Visual Studio. The PyCharm is also a good option for IDE that will allow you to watch your code variables and the JSON in a formatted structure.","Q_Score":6,"Tags":"mongodb,python-3.x,pymongo","A_Id":34493742,"CreationDate":"2015-12-28T12:26:00.000","Title":"Pretty printing of output in pymongo","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I set a key that I have now realizes is wrong. It is set at migration 0005. The last migration I did was 0004. I'm now up to 0008. I want to rebuild the migrations with the current models.py against the current database schema. Migration 0005 is no longer relevant and has been deleted from models.py. Migration 0005 is also an IntegrityError, so it cannot be applied without deleting data that shouldn't be deleted.\nHow do I get past migration 0005 so I can migrate?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":512,"Q_Id":34502379,"Users Score":0,"Answer":"Simply delete 0005-0008 migration files from migrations\/ folder.\nRe. database tables, you won't need to delete anything from there if migrations weren't applied. You can check yourself django_migrations table entries to be sure.","Q_Score":0,"Tags":"python,django,django-migrations,django-1.9","A_Id":61643148,"CreationDate":"2015-12-28T23:37:00.000","Title":"Delete migrations that haven't been migrated yet","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have data in an excel spreadsheet (*.xlsx) that consists of 1,213 rows of sensitive information (so, I'm sorry I can't share the data) and 35 columns. Every entry is a string (I don't know if that is screwing it up or not). The first row is the column names and I've never had a problem importing it with the column names embedded before (it's just easier to click that they're embedded so I don't have to name every column by hand). I put the path to the data in the quick start wizard and hit the next button and it doesn't do anything. I hit it again and it turns the mouse into the loader as if it's loading. I've waited for it for 15 minutes before, but every time I click on QlikView the program just crashes.\nI have a deadline I have to meet here and I can't afford to not finish this project. It's extremely important that I get it working.\nJust as a NB, I used Python to merge two Excel spreadsheets together so I don't know if that may be what's causing the problem either. I can open the file perfectly fine in Excel though.","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":626,"Q_Id":34532708,"Users Score":0,"Answer":"I have had QlikView crash when importing an Excel spreadsheet that was exported with the SQuirreL SQL client (from a Firebird database). Opening the spreadsheet in Excel, and saving it again solved the problem.\nI know that this is no longer relevant to your problem, but hopefully it can help someone with a similarly appearing issue.","Q_Score":0,"Tags":"python,excel,qlikview","A_Id":34534891,"CreationDate":"2015-12-30T15:52:00.000","Title":"Why does QlikView keep crashing when I try to load my data?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":1,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"My application is very database intensive so I'm trying to reduce the load on the database. I am using PostgreSQL as rdbms and python is the programming language.\nTo reduce the load I am already using a caching mechanism in the application. The caching type I used is a server cache, browser cache.\nCurrently I'm tuning the PostgreSQL query cache to get it in line with the characteristics of queries being run on the server.\nQuestions:\n\nIs it possible to fine tune query cache on a per database level?     \nIs it possible to fine tune query cache on a per table basis?\nplease provide tutorial to learn query cache in PostgreSQL.","AnswerCount":2,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":3440,"Q_Id":34553778,"Users Score":2,"Answer":"Tuning PostgreSQL is far more than just tuning caches. In fact, the primary high level things are \"shared buffers\" (think of this as the main data and index cache), and the work_mem.\nThe shared buffers help with reading and writing. You want to give it a decent size, but it's for the entire cluster.. and you can't really tune it on a per table or especially query basis. Importantly, it's not really storing query results.. it's storing tables, indexes and other data. In an ACID compliant database, it's not very efficient or useful to cache query results. \nThe \"work_mem\" is used to sort query results in memory and not have to resort to writing to disk.. depending on your query, this area could be as important as the buffer cache, and easier to tune. Before running a query that needs to do a larger sort, you can issue the set command like \"SET work_mem = '256MB';\"\nAs others have suggested you can figure out WHY a query is running slowly using \"explain\". I'd personally suggest learning the \"access path\" postgresql is taking to get to your data. That's far more involved and honestly a better use of resources than simply thinking of \"caching results\".\nYou can honestly improve things a lot with data design as well and using features such as partitioning, functional indexes, and other techniques.\nOne other thing is that you can get better performance by writing better queries.. things like \"with\" clauses can prevent postgres' optimizer from optimizing queries fully.\nThe optimizer itself also has parameters that can be adjusted-- so that the DB will spend more (or less) time optimizing a query prior to executing it.. which can make a difference.\nYou can also use certain techniques to write queries to help the optimizer. One such technique is to use bind variables (colon variables)--- this will result in the optimizer getting the same query over and over with different data passed in. This way, the structure doesn't have to be evaluated over and over.. query plans can be cached in this way.\nWithout seeing some of your queries, your table and index designs, and an explain plan, it's hard to make specific recommendation. \nIn general, you need to find queries that aren't as performant as you feel they should be and figure out where the contention is. Likely it's disk access, however,the cause is ultimately the most important part.. is it having to go to disk to hold the sort? Is it internally choosing a bad path to get to the data, such that it's reading data that could easily be eliminated earlier in the query process...  I've been an oracle certified DBA for over 20 years, and PostgreSQL is definitely different, however, many of the same techniques are used when it comes to diagnosing a query's performance issues. Although you can't really provide hints, you can still rewrite queries or tune certain parameters to get better performace.. in general, I've found postgresql to be easier to tune in the long run. If you can provide some specifics, perhaps a query and explain info, I'd be happy to give you specific recommendations. Sadly, though, \"cache tuning\" is likely to provide you the speed you're wanting all on its own.","Q_Score":11,"Tags":"python,sql,database,postgresql,caching","A_Id":58349778,"CreationDate":"2016-01-01T05:26:00.000","Title":"Enable the query cache in postgreSQL to improve performance","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am trying to use OpenPyXL to create invoices. I have a worksheet with an area to be printed and some notes outside of that range. I have most everything working but I am unable to find anything in the API for one function. Is there a way to set the print area on a worksheet?\nI am able to find lots of print settings, but not the print area.\nThanks!","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":3471,"Q_Id":34578910,"Users Score":0,"Answer":"This isn't currently directly possible. You could do it manually by creating a definedNamed using the reserved xlnm prefix (see Worksheet.add_print_title for an example.","Q_Score":2,"Tags":"python,openpyxl","A_Id":34579357,"CreationDate":"2016-01-03T16:37:00.000","Title":"OpenPyXL - How to set print area for a worksheet","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am writing a python code for beam sizing.  I have an Excel workbook from AISC that has all the data of the shapes and other various information on the cross-sections.  I would like to be able to reference data in particular cells in this Excel workbook in my python code.\nFor example if the width of rectangle is 2in and stored in cell A1 and the height is 10in and stored in cell B1 I want to write a code in python that somehow pulls in cell A1 and B1 and multiply them.\nI do not need to export back into excel I just want to make python do all the work and use excel purely as reference material.\nThank you in advance for all your advice and input!!","AnswerCount":4,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":2722,"Q_Id":34603090,"Users Score":0,"Answer":"Thank you for you inputs.  I have found the solution I was looking for by using Numpy.\ndata = np.loadtxt('C:\\Users[User_Name]\\Desktop[fname].csv', delimiter=',')\nusing that it took the data and created an array with the data that I needed.  Now I am able to use the data like any other matrix or array.","Q_Score":1,"Tags":"python,excel","A_Id":34603357,"CreationDate":"2016-01-05T02:03:00.000","Title":"Reference Excel in Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I've had a fairly good look on the web for an answer to this question, but I've tended to find that people assume more knowledge of databases than I currently have.  I'm sorry if this is a rookie question - I've always been aware of databases and their advantages, but never actually had to work with them.\nI have a requirement for a series of Python applications to read and write to a single SQL database.\nMy original plan was to create the database using SQLServer (at least while experimenting) and then access it via Python.  However, when I came to look at relevant Python packages (sqlite3, sqlalchemy, etc), they appear to create and maintain the database completely through Python.\nThis is absolutely fine, but will those Python-created-databases be fully compatible with non-Python tools and processes?  We will need to read data from C# as well.\nAs a secondary question, I like the look of sqlalchemy, but has it gone mainstream?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":93,"Q_Id":34609259,"Users Score":1,"Answer":"Although I would consider creating and maintaining databases in Python bad practice ( at least for MySQL and SQL Server), these databases will be fully compatible with non-Python tools and processes as they are created with the same SQL code. Regarding SQLAlchemy, this is used by several major companies and I have never experienced any problems with it, other than slow performance for large inserts.","Q_Score":0,"Tags":"python,mysql,sql-server,database","A_Id":34609510,"CreationDate":"2016-01-05T10:20:00.000","Title":"Python linkage to SQL databases","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"In pyodbc, cursor.rowcount works perfectly when using cursor.execute(). However, it always returns -1 when using cursor.executemany().\nHow does one get the correct row count for cursor.executemany()?\nThis applies to multiple inserts, updates, and deletes.","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":7653,"Q_Id":34613875,"Users Score":1,"Answer":"You can't, only the last query row count is returned from executemany, at least that's how it says in the pyodbc code docs. -1 usually indicates problems with query though.\nIf you absolutely need the rowcount, you need to either cursor.execute in a loop or write a patch for pyodbc library.","Q_Score":5,"Tags":"python,sql,pyodbc","A_Id":47834345,"CreationDate":"2016-01-05T14:20:00.000","Title":"How to get correct row count when using pyodbc cursor.executemany()","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am writing a form submit in my application written in python\/Django.Form has an attachment(upto 3MB) uploaded. On submit it has to save the attachment in aws s3, save the other data in database and also send emails.\nThis form submit is taking too much time and the UI is hanging.\nIs there any other way to do this in python\/django?","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":427,"Q_Id":34673515,"Users Score":0,"Answer":"The usual solution to tasks that are too long to be handled synchronously and can be handled asynchronously is to delegate them to some async queue like celery. \nIn your case, saving the form's data to db should be quite fast so I would not bother with this part, but moving the uploaded file to s3 and sending mails are good candidates.","Q_Score":1,"Tags":"python,django,forms,performance,amazon-s3","A_Id":34673727,"CreationDate":"2016-01-08T09:28:00.000","Title":"Python - On form submit send email and save record in database taking huge time","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Let's say that I need to maintain an index on a table where multiple documents can relate do the same item_id (not primary key of course).\nCan one secondary compound index based on the result of a function which of any item_id returns the most recent document based on a condition, update itself whenever a newer document gets inserted?\nThis table already holds 1.2 million documents in just 25 days, so it's a big-data case here as it will keep growing and must always keep the old records to build whatever pivots needed over the years.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":65,"Q_Id":34750575,"Users Score":0,"Answer":"I'm not 100% sure I understand the question, but if you have a secondary index and insert a new document or change an old document, the document will be in the correct place in the index once the write completes.  So if you had a secondary index on a timestamp, you could write r.table('items').orderBy(index: r.desc('timestamp')).limit(n) to get the most recent n documents (and you could also subscribe to changes on that).","Q_Score":0,"Tags":"indexing,rethinkdb,rethinkdb-python","A_Id":34750764,"CreationDate":"2016-01-12T17:53:00.000","Title":"RethinkDb do function based secondary indexes update themselves dynamically?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm trying to connect to a SQL Server named instance from python 3.4 on a remote server, and get an error.\n\nFile \"C:\\Scripts\\Backups Integrity Report\\Backup Integrity Reports.py\", line 269, in \n  conn = pymssql.connect(host=r'hwcvcs01\\HDPS', user='My-office\\romano', password='PASS', database='CommServ')\n  File \"pymssql.pyx\", line 636, in pymssql.connect (pymssql.c:10178)\n  pymssql.OperationalError: (20002, b'DB-Lib error message 20002, severity 9:\\nAdaptive Server connection failed\\n')\n\nOther SQLs are connected without a problem. Also I manage to connect to the SQL using the Management Studio, from the same remote server.\nTried different ports, tried to connect to the host itself rather than the instance, and also tried pypyodbc.\nWhat might be the problem?","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":4865,"Q_Id":34774326,"Users Score":1,"Answer":"According to the pymssql documentation on the pymssql Connection class, for a named instance containing database theDatabase, looking like this:\nmyhost\\myinstance\nYou could connect as follows:\npymssql.connect(host=r'myhost\\myinstance', database='theDatabase', user='user', password='pw')\nThe r-string is a so-called raw string that does not treat the '' as an escape.","Q_Score":3,"Tags":"python,instance,pymssql,named","A_Id":66684103,"CreationDate":"2016-01-13T18:28:00.000","Title":"Python pymssql - Connecting to Named Instance","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm new to Django. It wasted me whole afternoon to config the MySQL engine. I am very confused about the database engine and the database driver. Is the engine also the driver?  All the tutorial said that the ENGINE should be 'django.db.backends.mysql', but how the ENGINE decide which driver is used to connect MySQL? \nEvery time it says 'django.db.backends.mysql', sadly I can't install MySQLDb and mysqlclient, but PyMysql and the official mysql connector 2.1.3 has been installed. How could I set the driver to PyMysql or mysql connector?\nMany thanks!\n\nOS: OS X Al Capitan\nPython: 3.5\nDjango: 1.9\n\nThis question is not yet solved:\nIs the ENGINE also the DRIVER?","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":18120,"Q_Id":34777755,"Users Score":1,"Answer":"The short answer is no they are not the same.\nThe engine, in a Django context, is in reference to RDBMS technology. The driver is the library developed to facilitate communication to that actual technology when up and running. Letting Django know what engine to use tells it how to translate the ORM functions from a backend perspective. The developer doesn't see a change in ORM code but Django will know how to convert those actions to a language the technology understands. The driver then takes those actions (e.g. selects, updates, deletes) and sends them over to a running instance to facilitate the action.","Q_Score":20,"Tags":"python,mysql,django,pymysql","A_Id":53195032,"CreationDate":"2016-01-13T21:50:00.000","Title":"How to config Django using pymysql as driver?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a Flask-admin application and I have a class with a \"Department\" and a \"Subdepartment\" fields.\nIn the create form, I want that when a Department is selected, the Subdepartment select automatically loads all the corresponding subdepartments.\nIn the database, I have a \"department\" table and a \"sub_department\" table that was a foreign key \"department_id\".\nAny clues on how I could achieve that?\nThanks in advance.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":44,"Q_Id":34786665,"Users Score":0,"Answer":"You have to follow this steps\nJavascript\n\nBind a on change event to your Department select . \nIf the select changes you get the value selected.\nWhen you get the value, you have to send it to the server through an AJAX request.\n\nFlask\n\nImplement a method that reads the value and loads the associated Subdepartments.\nSend a JSON response to the view with your Subdepartments\n\nJavascript\n\nIn your AJAX request implement a success function. This function by default has as first parameter the data received from the server. Loop over them and append them to the wished select.","Q_Score":0,"Tags":"python,flask,flask-admin","A_Id":34786896,"CreationDate":"2016-01-14T10:05:00.000","Title":"Load a select list when selecting another select","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Coming off a NLTK NER problem, I have PERSONS and ORGANIZATIONS, which I need to store in a sqlite3 db. The obtained wisdom is that I need to create separate TABLEs to hold these sets. How can i create a TABLE when len(PERSONs) could vary for each id. It can even be zero.  The normal use of:\n    insert into table_name values (?),(t[0]) will return a fail.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":129,"Q_Id":34824495,"Users Score":0,"Answer":"Thanks to CL.'s comment, I figured out the best way is to think rows in a two-column table, where the first column is id INT, and the second column contains person_names. This way, there will be no issue with varying lengths of PERSONS list. of course, to link the main table with the persons table, the id field has to REFERENCE (foreign keys) to the story_id (main table).","Q_Score":0,"Tags":"python-2.7,database-design,sqlite","A_Id":34827171,"CreationDate":"2016-01-16T07:09:00.000","Title":"insert data in sqlite3 when array could be of different lengths","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have been working on a localhost copy of my Django website for a little while now, but finally decided it was time to upload it to PythonAnywhere. The site works perfectly on my localhost, but I am getting strange errors when I do the initial migrations for the new site. For example, I get this:\n\nmysql.connector.errors.DatabaseError: 1264: Out of range value for\n  column 'applied' at row 1\n\n'applied' is not a field in my model, so this error has to be generated by Django making tables for its own use. I have just checked in the MySQL manager for my localhost and the field 'applied' appears to be from the table django_migrations. \nWhy is Django mishandling setting up tables for its own use? I have dropped and remade the database a number of times, but the errors persist. If anyone has any idea what would cause this I would appreciate your advice very much.\nMy website front end is still showing the Hello World page and the Admin link comes up with a page does not exist error. At this stage I am going to assume this is related to the database errors.\nEDIT: Additional information about why I cannot access the front-end of the site:\nIt turns out when I am importing a pre-built site into PythonAnywhere, I have to edit my wsgi.py file to point to the application. The trouble now is that I don't know exactly what to put there. When I follow the standard instructions in the PythonAnywhere help files nothing seems to change. There website is also seems to be very short on detailed error messages to help sort it out. Is there perhaps a way to turn off their standard hello world placeholder pages and see server error messages instead?","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":463,"Q_Id":34836049,"Users Score":1,"Answer":"As it says in my comment above, it turns out that the problem with the database resulted from running an upgrade of Django from 1.8 to 1.9. I had forgotten about this. After rolling my website back to Django 1.8, the database migrations ran correctly.\nThe reason why I could not access the website turned out to be because I had to edit the wsgi.py file, but I was editing the wrong version. The nginx localhost web server I was using keeps it in the different folder location than PythonAnyhwere's implementation. I uploaded the file from my localhost copy and edited it according to the instructions on PythonAnywhere's help system without realizing it was not being read by PythonAnywhere's server. What I really needed to do was edit the correct file by accessing it through the web tab on their control panel. Once I edited this file, the website front end began to work as expected.","Q_Score":1,"Tags":"python,django,python-3.x,django-forms,pythonanywhere","A_Id":34837989,"CreationDate":"2016-01-17T07:12:00.000","Title":"Strange error during initial database migration of a Django site","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"As part of a big system, I'm trying to implement a service that (among other tasks) will serve large files (up to 300MB) to other servers (running in Amazon).\nThis files service needs to have more than one machine up and running at each time, and there are also multiple clients.\nService is written in Python, using Tornado web server.\nFirst approach was using MySQL, but I figured I'm going to have hell saving such big BLOBs, because of memory consumption.\nTried to look at Amazon's EFS, but it's not available in our region.\nI heard about SoftNAS, and am currently looking into it.\nAny other good alternatives I should be checking?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":191,"Q_Id":34895738,"Users Score":0,"Answer":"You also can use MongoDb , it provides several API, and also you can store file in S3 bucket with the use of Multi-Part Upload","Q_Score":0,"Tags":"python,mysql,amazon-web-services,nas","A_Id":34899601,"CreationDate":"2016-01-20T09:09:00.000","Title":"Serving large files in AWS","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I'm using wget to download Excel file with xlsx extension. The thing is that when I want to deal with the file using openpyxl, I get the above mentioned error. But when I download the file manually using fire fox, I don't have any problems. \nSo I checked the difference between the two downloaded files. I found that the manually one's size is much bigger (269.2 kB) compared to the wget one (7.3 kB), though both files show the same content when open by Excel 2013\nI don't add any options for the wget just use it like wget <downloadLink>\nWhat's wrong with wget and Excel files?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1390,"Q_Id":34896043,"Users Score":0,"Answer":"If the files are different in size then wget isn't getting the right file. Many websites now rely on javascript to handle links which wget can't emulate. I suspect that if you look at the file with less you'll see some HTML source as opposed to the start of a zipfile.","Q_Score":0,"Tags":"python-2.7,debian,wget","A_Id":34896780,"CreationDate":"2016-01-20T09:23:00.000","Title":"wget causes \"BadZipfile: File is not a zip file\" for openpyxl","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a Django website running on an Amazon EC2 instance. I want to add an EBS. In order to do that, I need to change the location of my PGDATA directory if I understand well. The new PGDATA path should be something like \/vol\/mydir\/blabla.\nI absolutely need to keep the data safe (some kind of dump could be useful). \nDo you have any clues on how I can do that ? I can't seem to find anything relevant on the internet.\nThanks","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":62,"Q_Id":34905744,"Users Score":0,"Answer":"Ok, thanks for your answers, I used : \nfind . -name \"postgresql.conf\" to find the configuration find, which was located into the \"\/etc\/postgresql\/9.3\/main\" folder. There is also pg_lsclusters if you want to show the directory data.\nThen I edited that file putting the new path, restarted postgres and imported my old DB.","Q_Score":1,"Tags":"python,django,postgresql,amazon-ec2","A_Id":34922249,"CreationDate":"2016-01-20T16:46:00.000","Title":"Django PostgreSQL : migrating database to a different directory","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a series of python objects, each associated with a different user, e.g., obj1.userID = 1, obj2.userID = 2, etc. Each object also has a transaction history expressed as a python dict, i.e., obj2.transaction_record = {\"itemID\": 1, \"amount\": 1, \"date\": \"2011-01-04\"} etc. \nI need these objects to persist, and transaction records may grow over time. Therefore, I'm thinking of using an ORM like sqlalchemy to make this happen. \nWhat kind of database schema would I need to specify to store these objects in a database?\nI have two alternatives, but neither seems like the correct thing to do:\n\nHave a different table for each user:\n\nCREATE TABLE user_id ( itemID INT PRIMARY KEY, amount INT, date CHARACTER(10) );\n\n\nStore the transaction history dict as a BLOB of json:\n\nCREATE TABLE foo ( userID INT PRIMARY KEY, trasaction_history BLOB);\nIs there a cleaner way to implement this?","AnswerCount":3,"Available Count":1,"Score":-0.0665680765,"is_accepted":false,"ViewCount":358,"Q_Id":34978896,"Users Score":-1,"Answer":"If you didn't make a decision until now for what kind of database you'll use, I advise you to pick mongodb as database server and mongoengine module for persist data, it's what you need, mongoengine has a DictField you can store in it a python dict directly and it's very easy to learn.","Q_Score":0,"Tags":"python,sqlite,sqlalchemy","A_Id":34979208,"CreationDate":"2016-01-24T17:17:00.000","Title":"What kind of database schema would I use to store users' transaction histories?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am trying to call a postgres database procedure using psycopg2 in my python class.\nlCursor.callproc('dbpackage.proc',[In_parameter1,In_parameter2,out_parameter]).\nIn_parameter values is 5008001#60\u00b0V4#FR.tif\nBut I am getting the below error.\nDataError: invalid byte sequence for encoding \"UTF8\": 0xb0\nI have tried mostly solutions given on net, but no luck.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":2227,"Q_Id":34993615,"Users Score":0,"Answer":"Your encoding and the database connection encoding don't match. The database connection is in UTF8 and you're probably trying to send with Latin1 encoding.\nWhen opening the connection send SET client_encoding TO 'Latin1', after that PostgreSQL will assume all strings to be in Latin1 encoding regardless of the database encoding.\nAlternatively you can use conn.set_client_encoding('Latin1')","Q_Score":0,"Tags":"python,postgresql,utf-8","A_Id":34993660,"CreationDate":"2016-01-25T13:17:00.000","Title":"DataError: invalid byte sequence for encoding \"UTF8\": 0xb0 while calling the database procedure","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"When I am defining a model and using unique_together in the Meta, I can define more than one tuple. Are these going to be ORed or ANDed? That is lets say I have a model where\n\nclass MyModel(models.Model):\n    druggie = ForeignKey('druggie', null=True)\n    drunk = ForeignKey('drunk', null=True)\n    quarts = IntegerField(null=True)\n    ounces = IntegerField(null=True)\n\n    class Meta:\n        unique_together = (('drunk', 'quarts'),\n                           ('druggie', 'ounces'))\n\neither both druggie and ounces are unique or both drunk and quarts are unique, but not both.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":5860,"Q_Id":35024007,"Users Score":24,"Answer":"Each tuple results in a discrete UNIQUE clause being added to the CREATE TABLE query. As such, each tuple is independent and an insert will fail if any data integrity constraint is violated.","Q_Score":23,"Tags":"python,django,django-models","A_Id":35024190,"CreationDate":"2016-01-26T21:10:00.000","Title":"Multiple tuples in unique_together","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a python code which queries psql and returns a batch of results using cursor.fetchall().\nIt throws an exception and fails the process if a casting fails, due to bad data in the DB.\nI get this exception:\nFile \"\/usr\/local\/lib\/python2.7\/site-packages\/psycopg2cffi\/_impl\/cursor.py\", line 377, in fetchall\n    return [self._build_row() for _ in xrange(size)]\n  File \"\/usr\/local\/lib\/python2.7\/site-packages\/psycopg2cffi\/_impl\/cursor.py\", line 891, in _build_row\n    self._casts[i], val, length, self)\n  File \"\/usr\/local\/lib\/python2.7\/site-packages\/psycopg2cffi\/_impl\/typecasts.py\", line 71, in typecast\n    return caster.cast(value, cursor, length)\n  File \"\/usr\/local\/lib\/python2.7\/site-packages\/psycopg2cffi\/_impl\/typecasts.py\", line 39, in cast\n    return self.caster(value, length, cursor)\n  File \"\/usr\/local\/lib\/python2.7\/site-packages\/psycopg2cffi\/_impl\/typecasts.py\", line 311, in parse_date\n    raise DataError(\"bad datetime: '%s'\" % bytes_to_ascii(value))\nDataError: bad datetime: '32014-03-03'\n\nIs there a way to tell the caster to ignore this error and parse this as a string instead of failing the entire batch?","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":280,"Q_Id":35033997,"Users Score":0,"Answer":"change your psql query to cast and get the date column as string\ne.g. select date_column_name:: to_char from table_name.","Q_Score":4,"Tags":"python,python-2.7,psycopg2,psql","A_Id":35034708,"CreationDate":"2016-01-27T09:55:00.000","Title":"psql cast parse error during cursor.fetchall()","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I was asked to port a Access database to MySQL and\nprovide a simple web frontend for the users. \nThe DB consists of 8-10 tables and stores data about\nclients consulting (client, consultant,topic, hours, ...).\nI need to provide a webinterface for our consultants to use,\nwhere they insert all this information during a session into a predefined mask\/form.\nMy initial thought was to port the Access-DB to MySQL, which I have done\nand then use the web2py framework to build a user interface with login,\ninserting data, browse\/scroll through the cases and pulling reports.\nweb2py with usermanagment and a few samples views & controllers and \nMySQL-DB is running. I added the DB to the DAL in web2py,\nbut now I noticed, that with web2py it is mandatory to define every table\nagain in web2py for it being able to communicate with the SQL-Server.\nWhile struggeling to succesfully run the extract_mysql_models.py script\nto export the structure of the already existing SQL DB for use in web2py\nconcerns about web2py are accumulating.\nThis double\/redundant way of talking to my DB strikes me as odd and\nweb2py does not support python3.\nIs web2py the correct way to fulfill my task or is there better way?\nThank you very much for listening\/helping out.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":670,"Q_Id":35038543,"Users Score":0,"Answer":"This double\/redundant way of talking to my DB strikes me as odd and web2py does not support python3.\n\nAny abstraction you want to use to communicate with your database (whether it be the web2py DAL, the Django ORM, SQLAlchemy, etc.) will have to have some knowledge of the database schema in order to construct queries.\nEven if you programmatically generated all the SQL statements yourself without use of an ORM\/DAL, your code would still have to have some knowledge of the database structure (i.e., somewhere you have to specify names of tables and fields, etc.).\nFor existing databases, we aim to automate this process via introspection of the database schema, which is the purpose of the extract_mysql_models.py script. If that script isn't working, you should report an issue on Github and\/or open a thread on the web2py Google Group.\nAlso, note that when creating a new database, web2py helps you avoid redundant specification of the schema by handling migrations (including table creation) for you -- so you specify the schema only in web2py, and the DAL will automatically create the tables in the database (of course, this is optional).","Q_Score":0,"Tags":"python,mysql,frontend,crud,web2py","A_Id":35039883,"CreationDate":"2016-01-27T13:21:00.000","Title":"Using web2py for a user frontend crud","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Our current Python pipeline scrapes from the web and stores those data into the MongoDB. After that we load the data into an analysis algorithm. This works well on a local computer since mongod locates the database, but I want to upload the database on sharing platform like Google Drive so that other users can use the data without having to run the scraper again. \nI know that MongoDB stores data at \/data\/db as default, so could I upload the entire \/data\/db onto the Google Drive? \nAnother option seems to be exporting MongoDB into JSON or CSV, but our current implementation for the analysis algorithm already loads directly from MongoDB.","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":7187,"Q_Id":35119959,"Users Score":0,"Answer":"You can create a little Rest API for your database with unique keys and all peoples in your team will can use it.\nIf you want to use export only one time - just export it to JSON and no problem.","Q_Score":1,"Tags":"python,mongodb,pymongo,database","A_Id":35120084,"CreationDate":"2016-01-31T21:52:00.000","Title":"How to share database created by MongoDB?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"My Python script uses an ADODB.Recordset object.  I use an ADODB.Command object with a collection of ADODB.Parameter objects to update a record in the set.  After that, I check the state of the recordset, and it was 1, which is adStateOpen.  But when I call MyRecordset.Close(), I get an exception complaining that the operation is invalid in the set's current state.  What state could an open recordset be in that would make it invalid to close it, and what can I do to fix it?\nCode is scattered between a couple of files.  I'll work on getting an illustration together.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":305,"Q_Id":35133678,"Users Score":0,"Answer":"Yes, that was the problem.  Once I change the value of one of a recordset's ADODB.Field objects, I have to either update the recordset using ADODB.Recordset.Update() or call CancelUpdate().  \nThe reason I'm going through all this rigarmarole of the ADODB.Command object is that ADODB.Recordset.Update() fails at random (or so it seems to me) times, complaining that \"query-based update failed because row to update cannot be found\".  I've never been able to predict when that will happen or find a reliable way to keep it from happening.  My only choice when that happens is to replace the ADODB.Recordset.Update() call with the construction of a complete update query and executing it using an ADODB.Connection or ADODB.Command object.","Q_Score":0,"Tags":"python,adodb","A_Id":35134057,"CreationDate":"2016-02-01T14:59:00.000","Title":"Why can't a close an open ADODB.Recordset?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I created my own python module and packaged it with distutils. Now I installed it on a new system (python setup.py install) and I'm trying to call it from a plpython3u function, but I get an error saying the module does not exist.\nIt was working on a previous Ubuntu instalation, and I'm not sure what I did wrong when setting up my new system.\nI'm trying this on a Ubuntu 15.10 pc with postgresql 9.5, everything freshly installed. I'm also trying this setup in a docker image built with the same componentes (ubuntu 15.10 and pg 9.5). I get the same error in both setups.\nCould you please hint me about why this is failing? I wrote down my installation instructions for both systems (native and docker), so I can provide them if that helps.\nThanks","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":884,"Q_Id":35204352,"Users Score":1,"Answer":"Sorry guys I think I found the problem. I'm using plpython3 in my stored procedure, but intalled my custom module using python 2. I just did sudo python3 setup.py install and now it's working on the native Ubuntu. I'll now try modifying my docker image and see if it works there too.\nThanks","Q_Score":2,"Tags":"python,postgresql,ubuntu,docker","A_Id":35205633,"CreationDate":"2016-02-04T14:58:00.000","Title":"Can't import own python module in Postgresql plpython function","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"In a platform using Flask, SQLAlchemy, and Alembic, we constantly need to create new separate instances with their own set of resources, including a database.\nWhen creating a new instance, SQLAlchemy's create_all gives us a database with all the updates up to the point when the instance is created, but this means that this new instance does not have the migrations history that older instances have. It doesn't have an Alembic revisions table pointing to the latest migration.\nSo when the time comes to update both older instances (with migrations histories) and a newer instance without migrations history we have to either give the newer instance a custom set of revisions (ignoring older migrations than the database itself) or create a fake migrations history for it and use a global set of migrations. For the couple of times that this has happened, we have done the latter.\nIs making a root migration that sets up the entire database as it was before the first migration and then running all migrations instead of create_all a better option for bootstrapping the database of new instances?\nI'm concerned for the scalability of this as migrations increase in number.\nIs there perhaps another option altogether?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":591,"Q_Id":35260536,"Users Score":1,"Answer":"If you know the state of the database you can just stamp the revision you were at when you created in the instance.\n\nsetup instance\nrun create_all\nalembic heads (to determine latest version available in scripts dir)\nalembic stamp  \n\nHere is the doc from the commandline:\nstamp               'stamp' the revision table with the given revision;\n                        don't run any migrations.","Q_Score":4,"Tags":"python,sqlalchemy,flask-sqlalchemy,alembic","A_Id":35275008,"CreationDate":"2016-02-07T23:32:00.000","Title":"SQLAlchemy, Alembic and new instances","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"If one is using Django, what happens with changes made directly to the database (in my case postgres) through either pgadmin or psql? \nHow are such changes handled by migrations? Do they take precedence over what the ORM thinks the state of affairs is, or does Django override them and impose it's own sense of change history?\nFinally, how are any of these issues effected, or avoided, by git, if at all?\nThanks.","AnswerCount":2,"Available Count":1,"Score":0.2913126125,"is_accepted":false,"ViewCount":670,"Q_Id":35273294,"Users Score":3,"Answer":"The migrations system does not look at your current schema at all. It builds up its picture from the graph of previous migrations and the current state of models.py. That means that if you make changes to the schema from outside this system, it will be out of sync; if you then make the equivalent change in models.py and create migrations, when you run them you will probably get an error.\nFor that reason, you should avoid doing this. If it's done already, you could apply the conflicting migration in fake mode, which simply marks it as done without actually running the code against the database. But it's simpler to do everything via migrations in the first place.\ngit has no impact on this at all, other than to reiterate that migrations are code, and should be added to your git repo.","Q_Score":7,"Tags":"python,django,git,postgresql","A_Id":35273897,"CreationDate":"2016-02-08T15:31:00.000","Title":"Edit database outside Django ORM","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am using apache with mod_wsgi in windows platform to deploy my flask application. I am using sqlalchemy to connect redshift database with connection pool(size 10).\nAfter few days suddenly I am getting follwoing error.\n(psycopg2.OperationalError) SSL SYSCALL error: Software caused connection abort  \nCan anybody suggest why I am getting this error and how to fix?  \nIf I do the apache restart then this error gone. But after few days it again comeback.","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":3963,"Q_Id":35322629,"Users Score":1,"Answer":"I solved this error by turning DEBUG=False in my config file [and\/or in the run.py]. Hope it helps someone.","Q_Score":4,"Tags":"python,apache,flask,amazon-redshift","A_Id":44923869,"CreationDate":"2016-02-10T18:00:00.000","Title":"(psycopg2.OperationalError) SSL SYSCALL error: Software caused connection abort","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm developing a Django 1.8 application locally and having reached a certain point a few days ago, I uploaded the app to a staging server, ran migrations, imported the sql dump, etc. and all was fine.\nI've since resumed local development which included the creation of a new model, and changing some columns on an existing model. I ran the migrations locally with success, but after rsync-ing my files to the staging server, I get a 'relation already exists' error when running manage.py migrate. And when I visit the admin page for the new model, I get a 'column does not exist' error.\nIt seems as though the migrations for this model were partially successful but I cannot migrate the entirety of the model schema. I've tried commenting out parts of the migration files, but was not successful.  Would it be possible to create the missing columns via psql? Or is there some way of determining what is missing and then manually write a migration to create the missing database structure?\nI'm using Django 1.8.6, Python 3.4.3, and PostgreSQL 9.3.6. Any advice on this would be great. Thanks.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":772,"Q_Id":35336992,"Users Score":0,"Answer":"Try running migrate --fake-initial since you're getting the \"relation already exists\" error. Failing that, I would manually back up each one of my migration folders, remove them from the server, then re-generate migration files for each app and run them all again from scratch (i.e., the initial makemigrations).","Q_Score":0,"Tags":"python,django,postgresql,django-migrations","A_Id":35343687,"CreationDate":"2016-02-11T10:39:00.000","Title":"Migrations error in Django after moving to new server","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have created a model using QSqlTableModel, then created a tablview using QTableView and set the model on it.\nI want to update the model and view automatically whenever the database is updated by another program. How can I do that?","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":255,"Q_Id":35383018,"Users Score":1,"Answer":"There's no signal emitted for that currently. You could use a timer to query the last update timestamp and refresh the model data at designated intervals.","Q_Score":0,"Tags":"python,pyqt,auto-update,qtableview,qsqltablemodel","A_Id":35392361,"CreationDate":"2016-02-13T17:31:00.000","Title":"Automatically updating QSqlTableModel and QTableView","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":1,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a spreadsheet which references\/caches values from an external spreadsheet.  When viewing the cell in Excel that I want to read using OpenPyxl, I see the the contents as a string: Users .\nWhen I select the cell in Excel, I see the actual content in the Formula Bar is ='C:\\spreadsheets\\[_comments.xlsm]Rules-Source'!C5. I do not have the source spreadsheet stored on my machine.  So, it appears Excel is caching the value from a separate spreadsheet as I am able to view the value Users when viewing the local spreadsheet in Excel.\nWhen I read the cell from the local spreadsheet using OpenPyxl, I get ='[1]Rules-Source'!C5.\nIt is my understanding that OpenPyxl will not evaluate formulas.  However, the string Users has to be cached somewhere in the XLSM document, right? Is there any way I can get OpenPyxl to read the cached source rather than returning the cell formula?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":310,"Q_Id":35385486,"Users Score":0,"Answer":"Yes, Excel does cache the values from the other sheet but openpyxl does not preserve this because there is no way of checking it.","Q_Score":1,"Tags":"python,excel,python-3.x,openpyxl","A_Id":35392192,"CreationDate":"2016-02-13T21:22:00.000","Title":"OpenPyxl - difficulty getting cell value when cell is referencing other source","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm using openpyxl to read an Excel spreadsheet with a lot of formulas. For some cells, if I access the cell's value as e.g. sheet['M30'].value I get the formula as intended, like '=IFERROR(VLOOKUP(A29, other_wksheet, 9, FALSE)*E29, \"\")'. But strangely, if I try to access another cell's value, e.g. sheet['M31'].value all I get is =, even though in Excel that cell as essentially the same formula as M30: '=IFERROR(VLOOKUP(A30, other_wksheet, 9, FALSE)*E29, \"\")'. \nThis is happening in a bunch of other sheets with a bunch of other formulas and I can't seem to find any rhyme or reason for it. I've looked through the docs and I'm not loading data_only=True so I'm not sure what's going wrong.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":637,"Q_Id":35385519,"Users Score":0,"Answer":"This sounds very much like you are looking at cells using \"shared formulae\". When this is the case the same formula is used by several cells. The formula itself is only stored with one of those cells and all others are marked as formulae but just contain a reference. Until version 2.3 of openpyxl all such cells would return \"=\" as their value. However, version 2.3 now performs the necessary transformation of the formula for dependent cells. ie. a shared formula of say \"=A1+1\" for A1 will be translated to \"=B1+1\" for B1.\nPlease upgrade to 2.3 if you are not already using it.\nIf this is not the case then please submit a bug report with the sample file.","Q_Score":1,"Tags":"python,excel,xlrd,openpyxl","A_Id":35392251,"CreationDate":"2016-02-13T21:26:00.000","Title":"openpyxl showing '=' instead of formula","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a Flask app that uses SQLAlchemy (Flask-SQLAlchemy) and Alembic (Flask-Migrate).  The app runs on Google App Engine. I want to use Google Cloud SQL.\nOn my machine, I run python manage.py db upgrade to run my migrations against my local database.  Since GAE does not allow arbitrary shell commands to be run, how do I run the migrations on it?","AnswerCount":3,"Available Count":1,"Score":0.0665680765,"is_accepted":false,"ViewCount":1816,"Q_Id":35391120,"Users Score":1,"Answer":"You can whitelist the ip of your local machine for the Google Cloud SQL instance, then you run the script on your local machine.","Q_Score":8,"Tags":"python,google-app-engine,flask,google-cloud-sql,alembic","A_Id":35395267,"CreationDate":"2016-02-14T11:17:00.000","Title":"Run Alembic migrations on Google App Engine","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I'm working in a Python program which has to access data that is currently stored in plain text files. Each file represents a cluster of data points that will be accessed together. I don't need to support different queries, the only thing I need is to retrieve and copy to memory cluster of data as fast as possible.\nI'm wondering if maybe a document oriented database could work better than my current text file approach. In particular, I would like to know if the seek time and transfer speed are the same in document-oriented DBs that in files.\nShould I switch to a document-oriented database or stay with the plain file?","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":367,"Q_Id":35421803,"Users Score":0,"Answer":"A DODB sounds like a much more reliable and professional solution. Besides you can add stored procedures thinking in the future and besides most databases offer text search capabilities. Backups are also easier, instead of using an incremental tar command, you can use the native DB backup tools.   \nI'm fan of CouchDB and you can add RESTful calls in a \"transparent\" way to it with JSON as the default response.","Q_Score":2,"Tags":"python,database,filesystems,document-oriented-db","A_Id":35421941,"CreationDate":"2016-02-16T00:52:00.000","Title":"Document-oriented databases vs plain text files","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"When Mongoengine rebuild(update) a information about indexes? I mean, if a added or change some field (added uniques or sparse option to filed) or added some meta info in model declaration. \nSo question is:\n\nWhen mongoengine update it?\nHow do they track changes?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":349,"Q_Id":35437458,"Users Score":1,"Answer":"Mongoengine do not rebuild index automaticly. Mongoengine track changes in models (btw dont work if you add sparse to your filed(if field dont have unique options)) and then fire the ensureIndex in mongoDB. But when its fire - make sure you delete oldest index version manualy(Mongoengine doesn't) in mongoDB. \nThe problem is:\n\nif you add sparse to filed w.o unique option - this changes dont mapped in mongoDB index. You need to combine unique = True, sparse = True\nIf you change indexs in models - you need to manualy delete old indexes in mongoDB.","Q_Score":3,"Tags":"python,mongodb,mongoengine","A_Id":35648604,"CreationDate":"2016-02-16T16:11:00.000","Title":"When Mongoengine rebuild indexes?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have about million records in a list that I would like to write to a Netezza table. I have been using executemany() command with pyodbc, which seems to be very slow (I can load much faster if I save the records to Excel and load to Netezza from the excel file). Are there any faster alternatives to loading a list with executemany() command?\nPS1: The list is generated by a proprietary DAG in our company, so writing to the list is very fast. \nPS2: I have also tried looping executemany() into chunks, with each chunk containing a list with 100 records. It takes approximately 60 seconds to load, which seems very slow.","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":806,"Q_Id":35466165,"Users Score":0,"Answer":"Netezza is good for bulk loads, where executeMany() inserts number of rows in one go. The best way to load millions of rows is \"nzload\" utility which can be scheduled by vbscript, Excel Macro from Windows or Shell script from Linux.","Q_Score":1,"Tags":"python,list,pyodbc,netezza,executemany","A_Id":35599759,"CreationDate":"2016-02-17T19:40:00.000","Title":"Loading data to Netezza as a list is very slow","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have about a million rows of data with lat and lon attached, and more to come. Even now reading the data from SQLite file (I read it with pandas, then create a point for each row) takes a lot of time. \nNow, I need to make a spatial joint over those points to get a zip code to each one, and I really want to optimise this process. \nSo I wonder: if there is any relatively easy way to parallelize those computations?","AnswerCount":3,"Available Count":2,"Score":0.0665680765,"is_accepted":false,"ViewCount":939,"Q_Id":35581528,"Users Score":1,"Answer":"I am assuming you have already implemented GeoPandas and are still finding difficulties?\nyou can improve this by further hashing your coords data. similar to how google hashes their search data. Some databases already provide support for these types of operations (eg mongodb). Imagine if you took the first (left) digit of your coords, and put each set of cooresponding data into a seperate sqlite file. each digit can be a hash pointing to the correct file to look for. now your lookup time has improved by a factor of 20 (range(-9,10)), assuming your hash lookup takes minimal time in comparison","Q_Score":2,"Tags":"python,multithreading,pandas,geopandas","A_Id":35583196,"CreationDate":"2016-02-23T15:28:00.000","Title":"Fastest approach for geopandas (reading and spatialJoin)","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have about a million rows of data with lat and lon attached, and more to come. Even now reading the data from SQLite file (I read it with pandas, then create a point for each row) takes a lot of time. \nNow, I need to make a spatial joint over those points to get a zip code to each one, and I really want to optimise this process. \nSo I wonder: if there is any relatively easy way to parallelize those computations?","AnswerCount":3,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":939,"Q_Id":35581528,"Users Score":1,"Answer":"As it turned out, the most convenient solution in my case is to use pandas.read_SQL function with specific chunksize parameter. In this case, it returns a generator of data chunks, which can be effectively feed to the mp.Pool().map() along with the job; \nIn this (my) case job consists of 1) reading  geoboundaries, 2) spatial joint of the chunk 3) writing the chunk to the database.","Q_Score":2,"Tags":"python,multithreading,pandas,geopandas","A_Id":35786998,"CreationDate":"2016-02-23T15:28:00.000","Title":"Fastest approach for geopandas (reading and spatialJoin)","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I need to migrate data from MySQL to Postgres. It's easy to write a script that connects to MySQL and to Postgres, runs a select on the MySQL side and inserts on the Postgres side, but it is veeeeery slow (I have + 1M rows). It's much faster to write the data to a flat file and then import it.\nThe MySQL command line can download tables pretty fast and output them as tab-separated values, but that means executing a program external to my script (either by executing it as a shell command and saving the output to a file or by reading directly from the stdout). I am trying to download the data using Python instead of the MySQL client.\nDoes anyone know what steps and calls does the MySQL command line perform to query a large dataset and output it to stdout? I thought it could be just that the client is in C and should be much faster than Python, but the Python binding for MySQL is itself in C so... any ideas?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":181,"Q_Id":35592092,"Users Score":0,"Answer":"I believe that the problem is that you are inserting each row in a separate transaction (which is the default behavior when you run SQL-queries without explicitly starting a transaction). In that case, the database must write (flush) changes to disk on every INSERT. It can be 100x times slower than inserting data in a single transaction. Try to run BEGIN before importing data and COMMIT after.","Q_Score":0,"Tags":"python,mysql,postgresql","A_Id":35598628,"CreationDate":"2016-02-24T02:22:00.000","Title":"Why is MySQL command line so fast vs. Python?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I first had a updating problem with using google drive api, Even I followed the example of Quickstart, and after making some changes on it, the file on google drive is updated successfully. But now here comes a new problem after updating, I am not sure if it is because my change to the Quickstart is not proper, or something else. The problem is after updating the an excel file on google drive with an excel file on my local machine, the excel file on my local mahine is not editable if I don't close the IDLE terminal; but if I close the IDLE window, I can do everything with the excel file and save the changes. Such as, without closing the IDLE file, and I made some changes on the excel file and try to save it, then the system says something like sharing violation, and save the file as a temporary file 62635600...., if I try to delete the excel file, then the system says the file is being used by pythonw.exe. After closing the IDLE window, the excel goes back to normal, same as a normal excel file. Anybody has any idea?","AnswerCount":3,"Available Count":1,"Score":0.0665680765,"is_accepted":false,"ViewCount":597,"Q_Id":35604605,"Users Score":1,"Answer":"You can install google drive on your local machine and copy the file into the google drive directory at the correct position. then google drive (the client software) will update the file.","Q_Score":1,"Tags":"python,google-api-python-client","A_Id":35604757,"CreationDate":"2016-02-24T14:17:00.000","Title":"After updating file on google drive through google api, the file on local machine is not editable without closing IDLE window","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a flask app that recently had to start using mssql generated guid's as primary keys (previously it was just integers). The guid's are latin-1 encoding. Also, I am not using sqlalchemy. Now, when I'm trying to display the queried mssql guid's in a flask jinja2 template, I get the following error:\n\nUnicodeDecodeError: 'ascii' codec can't decode byte 0xc1 in position 0: ordinal not in range(128).\n\nI've tried:\n\nunsetting the LANG on the linux host\nForcing utf-8 in FreeTDS config (this was already done)\nescaping in the jinja template\nusing python3, no luck\nswitching from pypyodbc to pyodbc3, but the problem presists\n\nNothing seems to work. If I import sys and set the decoding to utf-8, the error changes replacing ascii with utf-8, but the jinja template will not render the guid's.\nAny thoughts? Thanks for reading. Also to note, my dev environment is on windows 7 and this issue does not crop up there. It's only on the linux server.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":167,"Q_Id":35604937,"Users Score":0,"Answer":"Well, this feels like a hack, but since the only time I'm ever using these guid's is when i'm reading them from the database, I just did:\nCAST(REC_GUID_ID as VARCHAR(36)) as REC_GUID_ID\nAnd now they are in a format that everything seems to read just fine.","Q_Score":0,"Tags":"python,sql-server,flask,jinja2","A_Id":35608084,"CreationDate":"2016-02-24T14:31:00.000","Title":"Unicode issue using flask and mssql guids with FreeTDS","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I've built a Django app that uses sqlite (the default database), but I can't find anywhere that allows deployment with sqlite.  Heroku only works with postgresql, and I've spent two days trying to switch databases and can't figure it out, so I want to just deploy with sqlite. (This is just a small application.)\nA few questions:\n\nIs there anywhere I can deploy with sqlite?\nIf so, where\/how?","AnswerCount":3,"Available Count":1,"Score":-0.1325487884,"is_accepted":false,"ViewCount":3302,"Q_Id":35615273,"Users Score":-2,"Answer":"sure you can deploy with sqlite ... its not really recommended but should work ok if you have low network traffic \nyou set your database engine to sqlite in settings.py ... just make sure you have write access to the path that  you specify for your database","Q_Score":0,"Tags":"python,django,postgresql,sqlite,heroku","A_Id":35615302,"CreationDate":"2016-02-24T23:23:00.000","Title":"Is it possible to deploy Django with Sqlite?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a Raspberry Pi collecting data from sensors attached to it. I would like to have this data - collected every minute - accessible from an online DB (Amazon RDS | MySQL).\nCurrently, a python script running on the Pi pushes this data to an Amazon RDS instance every 50 seconds (~per minute). However, I have no records when internet is down. I will appreciate any suggestions on how to fix this.\nHere are my thoughts so far:\n\nstore data on a local MySQL DB, run a separate script that checks for differences between the online and local DB and updates the online one where needed. This will run every minute and write only one record to the online DB every minute if all is well.\nUtilize some sort of feature within MySQL itself - a replication job?","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":476,"Q_Id":35617670,"Users Score":1,"Answer":"I went with my first thought:\n\nstore the sensor data on a local DB (SQLite3 for its small footprint). Records are created every half minute.\na separate script - run regularly via cron - compares the last timestamp entry in the cloud DB with the local one and updates the cloud DB.\n\nEven though the comparison would ideally mean a doubling of DB transactions (a read + a write), if the last timestamp recorded on the online DB is stored locally for reference the remote read becomes unnecessary, thus being more efficient.","Q_Score":1,"Tags":"python,mysql,database,synchronization,raspberry-pi","A_Id":38479349,"CreationDate":"2016-02-25T03:28:00.000","Title":"Syncing locally collected regular data to online DB over unreliable internet connection","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am currently developing an export plugin for MySQL Workbench 6.3. It is my first one.\nIs there any developer tool that I can use to help me (debug console, watches, variables state, etc.)","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":156,"Q_Id":35649215,"Users Score":2,"Answer":"There is the GRT scripting shell, which you can reach via menu -> Scripting -> Scripting Shell. This shell is mostly useful for python plugins, but also shows some useful informations from the GRT (classes, the current tree with all settings, open editors, models etc.)","Q_Score":1,"Tags":"python,debugging,plugins,mysql-workbench","A_Id":35668094,"CreationDate":"2016-02-26T10:26:00.000","Title":"MySQL Workbench developer tools","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am using a postgres database with sql-alchemy and flask. I have a couple of jobs which I have to run through the entire database to updates entries. When I do this on my local machine I get a very different behavior compared to the server. \nE.g. there seems to be an upper limit on how many entries I can get from the database?\nOn my local machine I just query all elements, while on the server I have to query 2000 entries step by step.\nIf I have too many entries the server gives me the message 'Killed'.\nI would like to know\n1. Who is killing my jobs (sqlalchemy, postgres)?\n2. Since this does seem to behave differently on my local machine there must be a way to control this. Where would that be?\nthanks\ncarl","AnswerCount":2,"Available Count":1,"Score":0.2913126125,"is_accepted":false,"ViewCount":2227,"Q_Id":35705211,"Users Score":3,"Answer":"Just the message \"killed\" appearing in the terminal window usually means the kernel was running out of memory and killed the process as an emergency measure.\nMost libraries which connect to PostgreSQL will read the entire result set into memory, by default.  But some libraries have a way to tell it to process the results row by row, so they aren't all read into memory at once.  I don't know if flask has this option or not.\nPerhaps your local machine has more available RAM than the server does (or fewer demands on the RAM it does have), or perhaps your local machine is configured to read from the database row by row rather than all at once.","Q_Score":1,"Tags":"python,database,postgresql,sqlalchemy,flask-sqlalchemy","A_Id":35707179,"CreationDate":"2016-02-29T17:01:00.000","Title":"postgres database: When does a job get killed","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am using mongodb in python. The problem I'm facing is during the generation of a key. The code through which I'm generating a key is:\npost_id = posts.insert_one({msg[\"To\"]:a}\nNow here, the \"To\" consist of an email address (which consists of a symbol dot(.)). I researched few documents online and I got to knew that \u201cTo\u201d of a mail cannot be used as a key, because in mongodb they use \u201c.(dot)\u201d and \u201c$\u201d as a nested document.\nSo now how can I proceed?","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":77,"Q_Id":35716642,"Users Score":1,"Answer":"i have done something like this..\n'To':'test@gmail(dot)com'","Q_Score":0,"Tags":"python,mongodb","A_Id":35765568,"CreationDate":"2016-03-01T07:04:00.000","Title":"How to set a generated key in mongodb using python?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm trying to write some documentation on how to restore a CKAN instance in my organization.\nI have backuped and restored successfully CKAN database and resources folder but i don't know what i have to do with datastore db.\nWhich is the best practice?\nUse pg_dump to dump the database or initialize it from the resources folder (if there is a way)?\nThanks.\nAlex","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1289,"Q_Id":35726924,"Users Score":4,"Answer":"Backup CKAN's databases (the main one and Datastore one if you use it) with pg_dump. If you use Filestore then you need to take a backup copy of the files in the directory specified by ckan.storage_path (default is \/var\/lib\/ckan\/default)\nRestore the database backups (after doing createdb) using psql -f. Then run paster db upgrade just in case it was from an older ckan version. Then paster --plugin=ckan search-index rebuild. In an emergency use rebuild_fast instead of rebuild, but I think it might create some duplicates entries, so to be certain you could then do rebuild -r to do it again carefully but slowly.\n\ninitialize [the datastore database] from the resources folder (if there is a way)\n\nI don't think the CKAN Data Pusher has a command-line interface to push all the resources. It would be a good plan for you to write one and submit a PR for everyone's benefit.","Q_Score":5,"Tags":"python,ckan","A_Id":35729219,"CreationDate":"2016-03-01T15:31:00.000","Title":"Ckan backup and restore","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Hello everybody this is my first post,\nI made a website with Django 1.8.9 and Python 3.4.4 on Windows 7. As I was using SQLite3 everything was fine.\nI needed to change the database to MySQL. I installed MySQL 5.6 and mysqlclient. I changed the database settings and made the migration ->worked.\nBut when I try to register a new account or logging into the admin (made createsuperuser before) I get this Error:\n(1146, \"Table 'community_db.app_cache' doesn't exist\")\nI restarted the server and restarted command prompt.\nWhat also confuses me is the next row:\nC:\\Python34\\lib\\site-packages\\MySQLdb\\connections.py in query, line 280\nI was reading that there isn't any MySQLdb for Python 3\nWould be nice if there is any help. I already spent such a long time for this website and I tried to solve this problem like allllll the other ones before, but for this one I can't find any help via google\/stackover. I don't know what to do","AnswerCount":2,"Available Count":2,"Score":0.0996679946,"is_accepted":false,"ViewCount":2782,"Q_Id":35732758,"Users Score":1,"Answer":"So here is the answer for all the django (or coding in general) noobs like me.\npython manage.py createcachetable\nI totally forgot about that and this caused all the trouble with \"app_cache doesn't exist\". At least in this case...\nI changed my database to PostgreSQL, but I am sure it also helps with MySQL...","Q_Score":0,"Tags":"mysql,django,python-3.x,django-database","A_Id":35777867,"CreationDate":"2016-03-01T20:25:00.000","Title":"Django - MySQL : 1146 Table doesn't exist","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Hello everybody this is my first post,\nI made a website with Django 1.8.9 and Python 3.4.4 on Windows 7. As I was using SQLite3 everything was fine.\nI needed to change the database to MySQL. I installed MySQL 5.6 and mysqlclient. I changed the database settings and made the migration ->worked.\nBut when I try to register a new account or logging into the admin (made createsuperuser before) I get this Error:\n(1146, \"Table 'community_db.app_cache' doesn't exist\")\nI restarted the server and restarted command prompt.\nWhat also confuses me is the next row:\nC:\\Python34\\lib\\site-packages\\MySQLdb\\connections.py in query, line 280\nI was reading that there isn't any MySQLdb for Python 3\nWould be nice if there is any help. I already spent such a long time for this website and I tried to solve this problem like allllll the other ones before, but for this one I can't find any help via google\/stackover. I don't know what to do","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":2782,"Q_Id":35732758,"Users Score":0,"Answer":"I would assume this was an issue with permissions. As in the web-page connects with a user that doesn't have the proper permissions to create content.\nIf your tables are InnoDB, you'll get the table doesn't exist message. You need the ib* files in the root of the MySQL datadir (e.g. ibdata1, ib_logfile0 ib_logfile1)\nIf you don't have these files, you might need to fix permissions by logging directly into your DB","Q_Score":0,"Tags":"mysql,django,python-3.x,django-database","A_Id":35733218,"CreationDate":"2016-03-01T20:25:00.000","Title":"Django - MySQL : 1146 Table doesn't exist","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"What's the best way to switch to a database management software from LibreOffice Calc?\nI would like to move everything from a master spreadsheet to a database with certain conditions. Is it possible to write a script in Python that would do all of this for me?\nThe data I have is well structured I have about 300 columns of assets and under every asset there is 0 - ~50 filenames. The asset names are uniform as well as the filenames.\nThank you all!","AnswerCount":2,"Available Count":2,"Score":0.0996679946,"is_accepted":false,"ViewCount":1516,"Q_Id":35784155,"Users Score":1,"Answer":"You can ofcourse use python for this task but it might be an overkill.\nThe CSV export \/ import sequence is likely much faster, less error prone and needs less ongoing maintainance (e.g if you change the spreadsheet columns). The sequence is roughly as follows:\n\nselect the sheet that you want to import into a DB\nselect Files \/ Save as.. and then text\/csv\nselect a column separator that will not interfere with your data (e.g. |)\n\nThe import sequence into a database depends on your choice of db but today many IDE's and database GUI environments will automatically import \/ introspect your CSV file and create the table \/ insert the data for you. Things to be double check:\n\nYou may have to indicate that the first row is a header\nThe assigned datatype may need fine tuning if the automated guesses are not optimal","Q_Score":0,"Tags":"python,sql,database,libreoffice,libreoffice-calc","A_Id":66788273,"CreationDate":"2016-03-03T22:15:00.000","Title":"How to import data from LibreOffice Calc to a SQL database?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"What's the best way to switch to a database management software from LibreOffice Calc?\nI would like to move everything from a master spreadsheet to a database with certain conditions. Is it possible to write a script in Python that would do all of this for me?\nThe data I have is well structured I have about 300 columns of assets and under every asset there is 0 - ~50 filenames. The asset names are uniform as well as the filenames.\nThank you all!","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":1516,"Q_Id":35784155,"Users Score":0,"Answer":"You can create a python script that will read this spreadsheet row by row and then run insert statements in a database. In fact, would be even better if you save the spreadsheet as CSV for example, if you only need the data there.","Q_Score":0,"Tags":"python,sql,database,libreoffice,libreoffice-calc","A_Id":35784265,"CreationDate":"2016-03-03T22:15:00.000","Title":"How to import data from LibreOffice Calc to a SQL database?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am trying to create my personal web page. So in that I needed to put in the recommendations panel , which contains recommendations by ex employees\/friends etc.\nSo I was planning to create a model in django with following attributes:-\n\nauthor_name\nauthor_designation\nauthor_image\nauthor_comments\n\nI have following questions in my mind related to image part:-\n\nIs it good practice to store images in the backend database?(database is for structured information from what i understand)\nHow to store images so that scaling the content and managing it becomes really easy?","AnswerCount":3,"Available Count":1,"Score":0.0665680765,"is_accepted":false,"ViewCount":1276,"Q_Id":35844303,"Users Score":1,"Answer":"The best way to do this is to store the images in your server in some specific, general folder for this images. After that you store a string in your DB with the path to the image that you want to load. This will be a more efficient way to do this.","Q_Score":3,"Tags":"python,mysql,django","A_Id":35844490,"CreationDate":"2016-03-07T12:54:00.000","Title":"Is it a good practice to save images in the backend database in mysql\/django?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have installed Open edX (Dogwood) on an EC2 ubuntu 12.04 AMI and, honestly, nothing works. \nI can sign up in studio, and create a course, but the process does not complete. I get a nice page telling me that the server has an error. However, the course will show up on the LMS page. But, I cannot edit the course in Studio. \nIf I sign out of studio, I cannot log back without an error. However, upon refreshing the page, I am logged in. \nI can enable the search function and install the search app, but it doesn't show any courses and returns an error. \nCan someone point me to an AMI that works with, or includes, Open edX? The Open edX documentation is worthless. Or, failing that, explain to be what I am missing when installing Open edX using the automated installation scripts from the documention.","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":226,"Q_Id":35948834,"Users Score":1,"Answer":"This one works ami-7de8981d (us-east). Login with ssh as the 'ubuntu' user. Studio is on port 18010 and the LMS is on port 80.","Q_Score":1,"Tags":"python,django,amazon-web-services,edx,openedx","A_Id":36759310,"CreationDate":"2016-03-11T19:57:00.000","Title":"Open edX Dogwood problems","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am using the python cassandra-driver to execute queries on a cassandra database and I am wondering how to re-insert a ResultSet returned from a SELECT query on table A to a table B knowing that A and B have the same columns but a different primary keys.\nThanks in advance","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":294,"Q_Id":35964324,"Users Score":0,"Answer":"There is no magic, you'll need to:\n\ncreate a prepare statement for INSERT ... INTO tableB ...\non each ResultSet from table A, extract the values and create a\nbound statement for table B, then execute the bound statement for\ninsertion into B\n\nYou can use asynchronous queries to accelerate the migration a little bit but be careful to throttle the async.","Q_Score":0,"Tags":"python,cassandra,resultset","A_Id":35969262,"CreationDate":"2016-03-12T22:52:00.000","Title":"Cassandra python driver - how to re-insert a ResultSet","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am thinking if I don't use auto id as primary id in mysql but use other method to implement, may I replace auto id from bson.objectid.ObjectId in mysql?\nAccording to ObjectId description, it's composed of:\n\na 4-byte value representing the seconds since the Unix epoch\na 3-byte machine identifier\na 2-byte process id\na 3-byte counter, starting with a random value.\n\nIt seems it can provide unique and not duplicate key. Is it a good idea?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":373,"Q_Id":35983632,"Users Score":3,"Answer":"You certainly could do this. One issue though is that since this can't be set by the database itself, you'll need to write some Python code to ensure it is set on save.\nSince you're not using MongoDB, though, I wonder why you want to use a BSON id. Instead you might want to consider using UUID, which can indeed be set automatically by the db.","Q_Score":0,"Tags":"python,mysql,django,flask,primary-key","A_Id":35983791,"CreationDate":"2016-03-14T09:23:00.000","Title":"May I use bson.objectid.ObjectId as (primary key) id in sql?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I made a program with using sqlite3 and pyqt modules. The program can be used by different persons simultaneously. Actually I searched but I did not know and understand the concept of server. How can i connect this program with a server. Or just the computers that have connections with the server is enough to run the program simultaneously?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":59,"Q_Id":35986526,"Users Score":2,"Answer":"Do u want to connect to sqlite database server? SQLite Is Serverless. It stores your data in a file.\nU should use maria db for db server. Or u can store your sqlite database file in a network shared drive or cloud or...","Q_Score":0,"Tags":"python,sqlite,server","A_Id":35986703,"CreationDate":"2016-03-14T11:38:00.000","Title":"How to connect my app with the database server","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":1,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am not getting Database tool window under View-> Tool Windows, in pyhcharm community version software, so that I can connect to MYSQL server database. Also,please suggest me if there is other ways by which I can connect to MY SQL server database using pycharm community version.","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":493,"Q_Id":35991312,"Users Score":1,"Answer":"Database support available only in paid Jetbrains IDEs","Q_Score":0,"Tags":"python,pycharm","A_Id":38564886,"CreationDate":"2016-03-14T15:15:00.000","Title":"Unable to connect to MYSQL server database using pycharm community (2.7.11)","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"If cursor.execute('select * from users') returns a 4 row set, and then cursor.fetchone(), is there a way to re-position the cursor to the beginning of the returned results so that a subsequent cursor.fetchall() gives me all 4 rows?\nOr do I need to the cursor.execute again, and then cursor.fetchall()?  This seems awkward.  \nI checked the Python docs and couldn't find something relevant.  What am I missing?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1900,"Q_Id":36022384,"Users Score":2,"Answer":"SQLite computes each result row on demand, so it is neither possible to go back to an earlier row, nor to determine how many following rows there will be.\nThe only way to go back is to re-execute the query. Alternatively, call fetchall() first, and then use the returned list instead of the cursor.","Q_Score":2,"Tags":"python,sqlite","A_Id":36030685,"CreationDate":"2016-03-15T21:19:00.000","Title":"Python & SQLite: fetchone() and fetchall() and cursor control","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am creating an appEngine application in python that will need to perform efficient geospatial queries on datastore data.  An example use case would be, I need to find the first 20 posts within a 10 mile radius of the current user.  Having done some research into my options, I have found that currently what seems like the 2 best approaches for achieving this type of functionality would be:\n\nIndexing geoHashed geopoint data using Python's GeoModel library\nCreating\/deleting documents of structured data using Google's newer SearchAPI\n\nIt seems from a high level perspective that indexing geohashes and performing queries on them directly would be less costly and much faster than having to create and delete a document for every geospatial query, however i've also read that geohashing can be very inaccurate along the equator or along 'faultlines' created by the hashing algorithm. I've seen very few posts contrasting the best methods in detail, and I think stack is a good place to have this conversation, so my questions are as follows:\n\nHas anyone implemented similar features and had positive experiences with either methods? \nWhich method would be the cheaper alternative?\nWhich would be the faster alternative?\nIs there another important method I'm leaving out?\n\nThanks in advance.","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":326,"Q_Id":36092591,"Users Score":1,"Answer":"Geohashing does not have to be inaccurate at all. It's all in the implementation details. What I mean is you can check the neighbouring geocells as well to handle border-cases, and make sure that includes neighbours on the other side of the equator.\nIf your use case is finding other entities within a radius as you suggest, I would definitely recommend using the Search API. They have a distance function tailored for that use.\nSearch API queries are more expensive than Datastore queries yes, but if you weigh in the computation time to do these calculations in your instance and probably iterating through all entities for each geohash to make sure the distance is actually less than the desired radius, then I would say Search API is the winner. And don't forget about the implementation time.","Q_Score":1,"Tags":"python,google-app-engine,google-cloud-datastore,google-search-api,geohashing","A_Id":36110881,"CreationDate":"2016-03-18T19:15:00.000","Title":"Geohashing vs SearchAPI for geospatial querying using datastore","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm completely new to managing data using databases so I hope my question is not too stupid but I did not find anything related using the title keywords...\nI want to setup a SQL database to store computation results; these are performed using a python library. My idea was to use a python ORM like SQLAlchemy or peewee to store the results to a database.\nHowever, the computations are done by several people on many different machines, including some that are not directly connected to internet: it is therefore impossible to simply use one common database.\nWhat would be useful to me would be a way of saving the data in the ORM's format to be able to read it again directly once I transfer the data to a machine where the main database can be accessed.\nTo summarize, I want to do:\n\nOn the 1st machine: Python data -> ORM object -> ORM.fileformat\nAfter transfer on a connected machine: ORM.fileformat -> ORM object -> SQL database\n\nWould anyone know if existing ORMs offer that kind of feature?","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":963,"Q_Id":36104521,"Users Score":0,"Answer":"Is there a reason why some of the machine cannot be connected to the internet?\nIf you really can't, what I would do is setup a database and the Python app on each machine where data is collected\/generated. Have each machine use the app to store into its own local database and then later you can create a dump of each database from each machine and import those results into one database.\nNot the ideal solution but it will work.","Q_Score":2,"Tags":"python,mysql,database,orm","A_Id":36104630,"CreationDate":"2016-03-19T16:59:00.000","Title":"Python ORM - save or read sql data from\/to files","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I try to use pip install psycopg2 on windows10 and python3.5, but it show me below error message. how can i fix it ?\n\nCommand\n  \"d:\\desktop\\learn\\python\\webcatch\\appserver\\webcatch\\scripts\\python.exe\n  -u -c \"import setuptools, tokenize;file='C:\\Users\\16022001\\AppData\\Local\\Temp\\pip-build-rsorislh\\psycopg2\\setup.py';exec(compile(getattr(tokenize,\n  'open', open)(file).read().replace('\\r\\n', '\\n'), file,\n  'exec'))\" install --record\n  C:\\Users\\16022001\\AppData\\Local\\Temp\\pip-kzsbvzx9-record\\install-record.txt\n  --single-version-externally-managed --compile --install-headers d:\\desktop\\learn\\python\\webcatch\\appserver\\webcatch\\include\\site\\python3.5\\psycopg2\"\n  failed with error code 1 in\n  C:\\Users\\16022001\\AppData\\Local\\Temp\\pip-build-rsorislh\\psycopg2\\","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":329,"Q_Id":36115491,"Users Score":0,"Answer":"pip install psycopg this worked for me, don't mention version i.e (pip install psycopg2)","Q_Score":0,"Tags":"python,windows,psycopg2","A_Id":69657488,"CreationDate":"2016-03-20T15:11:00.000","Title":"pip install psycopg2 error","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"In Django database username is used as schema name.\nIn DB2 there is no database level users. OS users will be used for login into the database.\nIn my database I have two different names for database user and database schema.\nSo in django with db2 as backend how can I use different schema name to access the tables?\nEDIT:\nClarifying that I'm trying to access via the ORM and not raw SQLs. The ORM implicitly is using the username as the schema name. How do I avoid that ?","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":688,"Q_Id":36159706,"Users Score":0,"Answer":"DB2 uses so-called two part names, schemaname.objectname. Each object, including tables, can be referenced by the entire name. Within a session there is the current schema which by default is set to the username. It can be changed by the SET SCHEMA myschema statement. \nFor your question there are two options:\n1) Reference the tables with their full name: schemaname.tablename\n2) Use set schema to set the common schemaname and reference just the table.","Q_Score":2,"Tags":"django,python-2.7,django-models,db2","A_Id":36159818,"CreationDate":"2016-03-22T16:15:00.000","Title":"django-db2 use different schema name than database username","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I've tried to deploy (includes migration) production environment. But my Django migration (like add columns) very often stops and doesn't progress anymore.\nI'm working with postgresql 9.3, and I find some reasons of this problem. If postgresql has an active transaction, alter table query is not worked. So until now, restarting postgresql service before migration was a solution, but I think this is a bad idea.\nIs there any good idea to progress deploying nicely?","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":1701,"Q_Id":36212891,"Users Score":1,"Answer":"Open connections will likely stop schema updates. If you can't wait for existing connections to finish, or if your environment is such that long-running connections are used, you may need to halt all connections while you run the update(s).\nThe downtime, if it's likely to be significant to you, could be mitigated if you have a read-only slave that could stay online. If not, ensuring your site fails over to some sort of error\/explanation page\/redirect would at least avoid raw failure code responses to requests that come in if downtime for migrations is acceptable.","Q_Score":1,"Tags":"python,django,postgresql","A_Id":36213045,"CreationDate":"2016-03-25T01:53:00.000","Title":"django migration doesn't progress and makes database lock","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm currently using google cloud sql 2nd generation instances to host my database. I need to make a schema change to a table but Im not sure what the best way to do this. \nIdeally, before I deploy using gcloud preview app deploy my migrations will run so the new version of the code is using the latest schema. Also, if I need to rollback to an old version of my app the migrations should run for that point in time. Is there a way to integrate sql schema migrations with my app engine deploys?\nMy app is app engine managed VM python\/flask.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":180,"Q_Id":36231114,"Users Score":-2,"Answer":"SQL schema migration is a well-known branch of SQL DB administration which is not specific to Cloud SQL, which is mainly different to other SQL systems in how it is deployed and networked. Other than this, you should look up schema migration documentation and articles online to learn how to approach your specific situation. This question is too broad for Stack Overflow as it is, however. Best of luck!","Q_Score":1,"Tags":"python,google-app-engine,google-cloud-sql,gcloud","A_Id":36407336,"CreationDate":"2016-03-26T02:54:00.000","Title":"How to perform sql schema migrations in app engine managed vm?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I want to use psycopg2 (PostgreSQL) with virtualenv.\nI am using Ubuntu and root already having psycopg2 and it is working fine but if i try to use it after activating virtualenv it shows\nImportError: No module named psycopg2\nDo i need to put symbolic link of dist-packages manually ??","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":20,"Q_Id":36246954,"Users Score":2,"Answer":"virtualenvs are by default isolated from the system packages so you need to install all packages into each virtualenv (or you can pass --system-site-packages when creating it).","Q_Score":0,"Tags":"python,postgresql,python-2.7,virtualenv,psycopg2","A_Id":36247000,"CreationDate":"2016-03-27T11:49:00.000","Title":"PostgreSQL not working with virtual envirement","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am using a simple sqlalchemy paginate statement like this\nitems = models.Table.query.paginate(page, 100, False)\nwith page = 1. When running this command twice I get different outputs? If I run it with less element (e.g. 10) it gives me the same outputs when run multiple times? I thought for a paginate command to work it has to result in the same set each time it is called? \ncheers \ncarl","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":193,"Q_Id":36319702,"Users Score":0,"Answer":"ok I don't know the answer to this question but ordering the query (order_by) solved my problem... I am still interested to know why paginate does not have an order by itself, because it basically means that without the order statement, paginate cannot be used to iterate through all elements?\ncheers\ncarl","Q_Score":0,"Tags":"python,pagination,flask-sqlalchemy","A_Id":36334148,"CreationDate":"2016-03-30T21:04:00.000","Title":"flask sqlalchemy paginate() function does not get the same elements when run twice","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I need to develop natural language querying tool for a structured database. I tried two approaches.\n\nusing Python nltk (Natural Language Toolkit for python) using\nJavascript and JSON (for data source)\n\nIn the first case I did some NLP steps to format the natural query by doing removing stop words, stemming, finally mapping keywords using featured grammar mapping. This methodology works for simple scenarios.\nThen I moved to second approach. Finding the data in JSON and getting corresponding column name and table name , then building a sql query. For this one,  I also implemented removing stop words, stemming using javascript.\nBoth of these techniques have limitations.I want to implement semantic search approach.\nPlease can anyone suggest me better approach to do this..","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1077,"Q_Id":36330033,"Users Score":0,"Answer":"As I commented, I think you should add some code, since not everyone has read the book.\nAnyway my conclusion is that yes, as you said it has a lot of limitations and the only way to achieve more complex queries is to write very extensive and complete grammar productions, a pretty hard work.","Q_Score":1,"Tags":"javascript,python,json,nlp,nltk","A_Id":36531992,"CreationDate":"2016-03-31T09:56:00.000","Title":"Natural Language Processing Database Querying","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have been trying to find examples in ZODB documentation about doing a join of 2 or more tables. I know that this is an Object Database, but I am trying to create objects that represent tables.\nAnd I see that ZODB makes use SQLAlchemy.\nSo I was wondering if I can treat things in ZODB in a relational like sense.\nI hope someone can let me know if my train of thought in using this ZODB is OK, or if one has to think in very different way.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":156,"Q_Id":36457076,"Users Score":2,"Answer":"ZODB does not use SQLAlchemy, and there is no relational model. There are no tables to join, period. The ZODB stores an object tree, there is no schema. It's just Python objects in more Python objects.\nAny references to ZODB and SQLAlchemy are all for applications built on top of the ZODB, where transactions for external relational databases accessed through SQLAlchemy are tied in with the ZODB transaction manager to ensure that transactions cover both the ZODB and data in other databases. This essential means that when you commit the ZODB transaction, SQLAlchemy is told about this too.","Q_Score":0,"Tags":"python,sqlalchemy,zodb","A_Id":36479782,"CreationDate":"2016-04-06T16:32:00.000","Title":"ZODB database: table joins","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"There is a use case in which we would like to add columns from the data of a webservice to our original sql data table.\nIf anybody has done that then pls do comment.","AnswerCount":2,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":959,"Q_Id":36526219,"Users Score":2,"Answer":"Shadowfax is correct that you should review the How to Ask guide.\nthat said, Spotfire offers this feature in two ways:\n\nuse IronPython scripting attached to an action control to retrieve the data. this is a very rigid solution that offers no caching, and the data must be retrieved and placed in memory each time the document is opened. I'll leave you to the search feature here on SO; I've posted a sample document somewhere.\nthe ideal solution is to use a separate product called Spotfire Advanced Data Services. this data federation layer can mashup data and perform advanced, custom caching based on your needs. the data is then exposed as an information link in Spotfire Server. you'll need to talk to your TIBCO sales rep about this.","Q_Score":0,"Tags":"sql-server,web-services,ironpython,spotfire","A_Id":36533707,"CreationDate":"2016-04-10T05:33:00.000","Title":"How to use a web service as a datasource in Spotfire","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a dynamo table called 'Table'. There are a few columns in the table, including one called 'updated'. I want to set all the 'updated' field to '0' without having to providing a key to avoid fetch and search in the table.\nI tried batch write, but seems like update_item required Key inputs. How could I update the entire column to have every value as 0 efficiently please?\nI am using a python script.\nThanks a lot.","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":643,"Q_Id":36562764,"Users Score":1,"Answer":"At this point, you cannot do this, we have to pass a key (Partition key or Partition key and sort key) to update the item.\nCurrently, the only way to do this is to scan the table with filters to get all the values which have 0 in \"updated\" column and get respective Keys.\nPass those keys and update the value.\nHopefully, in future AWS will come up with something better.","Q_Score":2,"Tags":"database,python-2.7,amazon-dynamodb,insert-update","A_Id":36564082,"CreationDate":"2016-04-12T02:49:00.000","Title":"DynamoDB update entire column efficiently","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a dynamo table called 'Table'. There are a few columns in the table, including one called 'updated'. I want to set all the 'updated' field to '0' without having to providing a key to avoid fetch and search in the table.\nI tried batch write, but seems like update_item required Key inputs. How could I update the entire column to have every value as 0 efficiently please?\nI am using a python script.\nThanks a lot.","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":643,"Q_Id":36562764,"Users Score":0,"Answer":"If you can get partition key, for each partition key you can update the item","Q_Score":2,"Tags":"database,python-2.7,amazon-dynamodb,insert-update","A_Id":36564129,"CreationDate":"2016-04-12T02:49:00.000","Title":"DynamoDB update entire column efficiently","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am using python with boto3 to upload file into s3 bucket. Boto3 support upload_file() to create s3 object. But this API takes file name as input parameter \nCan we give actual data buffer as a parameter to upload file () function instanced of file name? \nI knew that we can use put_object() function if we want to give data buffer as parameter to create s3 object. But I want to use upload_file with data buffer parameter. Is there any way to get out of this? \nThanks in advance","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":638,"Q_Id":36568713,"Users Score":1,"Answer":"There is currently no way to use a file-like object with upload_file. put_object and upload_part do support these, though you don't get the advantage of automatic multipart uploads.","Q_Score":1,"Tags":"python-2.7,boto,boto3","A_Id":36582398,"CreationDate":"2016-04-12T09:13:00.000","Title":"Boto3 : Can we use actual data buffer as parameter instaed of file name to upload file in s3?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":1,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have just cloned a Django app from Github to a local directory. I know for a fact that the app works because I've run it on others' computers. \nWhen I run the server, I can see the site and register for an account. This works fine (I get a confirmation email). But then my login information causes an error because the DB appears to not have configured properly on my machine. I get the following errors: \n\/Library\/Frameworks\/Python.framework\/Versions\/3.4\/lib\/python3.4\/site-packages\/django\/db\/backends\/utils.py in execute\n                return self.cursor.execute(sql, params) ...\n\u25b6 Local vars\n\/Library\/Frameworks\/Python.framework\/Versions\/3.4\/lib\/python3.4\/site-packages\/django\/db\/backends\/sqlite3\/base.py in execute\n        return Database.Cursor.execute(self, query, params) ...\n\u25b6 Local vars\nThe above exception (no such table: django_session) was the direct cause of the following exception:\n(It then lists a bunch of problems with local vars). \nI tried making migrations with every part of the app but this didn't appear to fix anything.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":315,"Q_Id":36609201,"Users Score":0,"Answer":"The django_sessions table should get initialized when you run your first migrations. You said taht you made your migrations, but did you run them (with python manage.py migrate). Also, do you have django.contrib.auth in the installed_apps in your settings file? This is the app that owns that session table","Q_Score":1,"Tags":"python,django,git,github","A_Id":36613541,"CreationDate":"2016-04-13T20:42:00.000","Title":"Problems with database after cloning Django app from Github","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Need help from someone who has got Apache , Python and cx_Oracle (Lib to run Oracle database using python) .\nEven after setting all the required variables still getting the error \": libclntsh.so.11.1: cannot open shared object file: No such file or directory\" when running python script .\nThe same script works perfectly fine when running it from cli.\nMy working environment is RHEL 6.4\nAn help in this matter would be appreciated , for those who got this  working in their environment \nMerci d'avance","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":2034,"Q_Id":36655812,"Users Score":0,"Answer":"I was able to solve this with the help of mod_env module of python by natively passing the env_variables to apache . What I did to achieve this was \n--> define the my required env variables in the file \/etc\/sysconfig\/httpd like \n    LD_LIBRARY_PATH=$LD_LIBRARY_PATH:\/usr\/lib\/folder_with_library\/\n     export LD_LIBRARY_PATH\n--> Then passing this variable in the httpd.conf file like \n     PassEnv LD_LIBRARY_PATH\nHope this helps","Q_Score":0,"Tags":"python,apache,cx-oracle","A_Id":36711130,"CreationDate":"2016-04-15T19:56:00.000","Title":"libclntsh.so.11.1: cannot open shared object file python error while running CGIusing cx_Oracle","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Which is more efficient? Is there a downside to using open() -> write() -> close() compared to using logger.info()?\nPS. We are accumulating query logs for a university, so there's a perchance that it becomes big data soon (considering that the min-max cap of query logs per day is 3GB-9GB and it will run 24\/7 constantly for a lifetime). It would be appreciated if you could explain and differentiate in great detail the efficiency in time and being error prone aspects.","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":1554,"Q_Id":36819540,"Users Score":0,"Answer":"It is always better to use a built-in facility unless you are facing issues with the built-in functionality.\nSo, use the built-in logging function. It is proven, tested and very flexible - something you cannot achieve with open() -> f.write() -> close().","Q_Score":3,"Tags":"python,logging,file-writing,bigdata","A_Id":36819582,"CreationDate":"2016-04-24T05:15:00.000","Title":"Python logging vs. write to file","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Which is more efficient? Is there a downside to using open() -> write() -> close() compared to using logger.info()?\nPS. We are accumulating query logs for a university, so there's a perchance that it becomes big data soon (considering that the min-max cap of query logs per day is 3GB-9GB and it will run 24\/7 constantly for a lifetime). It would be appreciated if you could explain and differentiate in great detail the efficiency in time and being error prone aspects.","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":1554,"Q_Id":36819540,"Users Score":4,"Answer":"Use the method that more closely describes what you're trying to do. Are you making log entries? Use logger.*. If (and only if!) that becomes a performance issue, then change it. Until then it's an optimization that you don't know if you'll ever need.\nPros for logging:\n\nIt's semantic. When you see logging.info(...), you know you're writing a log message.\nIt's idiomatic. This is how you write Python logs.\nIt's efficient. Maybe not extremely efficient, but it's so thoroughly used that it has lots of nice optimizations (like not running string interpolation on log messages that won't be emitted because of loglevels, etc.).\n\nCons for logging:\n\nIt's not as much fun as inventing your own solution (which will invariably turn into an unfeatureful, poorly tested, less efficient version of logging).\n\nUntil you know that it's not efficient enough, I highly recommend you use it. Again, you can always replace it later if data proves that it's not sufficient.","Q_Score":3,"Tags":"python,logging,file-writing,bigdata","A_Id":36819569,"CreationDate":"2016-04-24T05:15:00.000","Title":"Python logging vs. write to file","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"My database on Amazon currently has only a little data in it (I am making a web app but it is still in development) and I am looking to delete it, make changes to the schema, and put it back up again.  The past few times I have done this, I have completely recreated my elasticbeanstalk app, but there seems like there is a better way. On my local machine, I will take the following steps:\n\n\"dropdb databasename\" and then \"createdb databasename\"\npython manage.py makemigrations\npython manage.py migrate\n\nIs there something like this that I can do on amazon to delete my database and put it back online again without deleting the entire application?  When I tried just deleting the RDS instance a while ago and making a new one, I was having problems with elasticbeanstalk.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":5860,"Q_Id":36820171,"Users Score":4,"Answer":"The easiest way to accomplish this is to SSH to one of your EC2 instances, that has acccess to the RDS DB, and then connect to the DB from there. Make sure that your python scripts can read your app configuration to access the configured DB, or add arguments for DB hostname. To drop and create your DB, you must just add the necessary arguments to connect to the DB. For example:\n$ createdb -h <RDS endpoint> -U <user> -W ebdb\nYou can also create a RDS snapshot when the DB is empty, and use the RDS instance actions Restore to Point in Time or Migrate Latest Snapshot.","Q_Score":1,"Tags":"python,django,amazon-web-services,amazon-elastic-beanstalk,amazon-rds","A_Id":36820728,"CreationDate":"2016-04-24T06:51:00.000","Title":"How to drop table and recreate in amazon RDS with Elasticbeanstalk?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"There is a way to define MongoDB collection schema using mongoose in NodeJS. Mongoose verifies the schema at the time of running the queries.\nI have been unable to find a similar thing for Motor in Python\/Tornado. Is there a way to achieve a similar effect in Motor, or is there a package which can do that for me?","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1449,"Q_Id":36841121,"Users Score":2,"Answer":"No there isn't. Motor is a MongoDB driver, it does basic operations but doesn't provide many conveniences. An Object Document Mapper (ODM) library like MongoTor, built on Motor, provides higher-level features like schema validation.\nI don't vouch for MongoTor. Proceed with caution. Consider whether you really need an ODM: mongodb's raw data format is close enough to Python types that most applications don't need a layer between their code and the driver.","Q_Score":2,"Tags":"python,mongodb,tornado-motor,motordriver","A_Id":36842258,"CreationDate":"2016-04-25T12:50:00.000","Title":"Is there a way to define a MongoDB schema using Motor?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":0},{"Question":"When inserting rows via INSERT INTO tbl VALUES (...), (...), ...;, what is the maximum number of values I can use? \nTo clarify, PostgreSQL supports using VALUES to insert multiple rows at once. My question isn't how many columns I can insert, but rather how many rows of columns I can insert into a single VALUES clause. The table in question has only ~10 columns.\nCan I insert 100K+ rows at a time using this format? \nI am assembling my statements using SQLAlchemy Core \/ psycopg2 if that matters.","AnswerCount":1,"Available Count":1,"Score":0.761594156,"is_accepted":false,"ViewCount":5268,"Q_Id":36879127,"Users Score":5,"Answer":"As pointed out by Gordon, there doesn't appear to be a predefined limit on the number of values sets you can have in your statement. But you would want to keep this to a reasonable limit to avoid consuming too much memory at both the client and the server. The client only needs to build the string and the server needs to parse it as well.\nIf you want to insert a large number of rows speedily COPY FROM is what you are looking for.","Q_Score":7,"Tags":"python,postgresql,sqlalchemy,psycopg2","A_Id":36879218,"CreationDate":"2016-04-27T02:17:00.000","Title":"What is the maximum number of VALUES that can be put in a PostgreSQL INSERT statement?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"So basically I have this collection where objects are stored with a string parameter.\nexample:\n\n{\"string_\": \"MSWCHI20160501\"}\n\nThe last part of that string is a date, so my question is this: Is there a way of writing a mongo query which will take that string, convert part of it into an IsoDate object and then filter objects by that IsoDate. \np.s \nI know I can do a migration but I wonder if I can achieve that without one.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":61,"Q_Id":36888098,"Users Score":1,"Answer":"Depending on the schema of your objects, you could hypothetically write an aggregation pipeline that would first transform the objects, then filter the results based on the results and then return those filtered results.\nThe main reason I would not recommend this way though is that, given a fairly large size for your dataset, the aggregation is going to fail because of memory problems.\nAnd that is without mentioning the long execution time for this command.","Q_Score":2,"Tags":"python,mongodb,pymongo","A_Id":37026108,"CreationDate":"2016-04-27T11:11:00.000","Title":"Write a query in MongoDB's client pymongo that converts a part of the string to a date on the fly","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"Using openpyxl, the charts inserted into my worksheet have a border on them.  Is there any way to set the style of the chart (pie\/bar) to either via the styles.Style\/styles.borders module to have no border, or at least a thin white border so that they would print borderless?\nThe only options I see on the object is .style = <int> which doesn't seem to actually affect the design of the final graphic.","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1846,"Q_Id":36988384,"Users Score":0,"Answer":"This isn't easy but should be possible. You will need to work through the XML source of a suitably formatted sample chart and see which particular variables need setting or changing. openpyxl implements the complete chart API but this unfortunately very complicated.","Q_Score":1,"Tags":"python,python-2.7,charts,openpyxl","A_Id":36988605,"CreationDate":"2016-05-02T17:42:00.000","Title":"openpyxl - Ability to remove border from charts?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"When am trying to create a database on server it shows an error \n\nError Code: 1006. Can't create database 'mmmm' (errno: 2)\n\nHow can I solve this error?\nThe server is mysql.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1074,"Q_Id":36995801,"Users Score":0,"Answer":"Likely you do not have permission to create a database.","Q_Score":0,"Tags":"mysql,mysql-workbench,mysql-python","A_Id":37046039,"CreationDate":"2016-05-03T04:48:00.000","Title":"Error Code: 1006. Can't create database 'mmmm' (errno: 2)","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm using Google Analytics API to make a Python program.\nFor now it's capable to make specific querys, but...\nIs possible to obtain a large JSON with all the data in a Google Analytics account?\nI've been searching and i didn't have found any answer.\nSomeone know if it's possible and how?","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":488,"Q_Id":36998698,"Users Score":0,"Answer":"Google Analytics stores a ton (technical term) of data; there are a lot of metrics and dimensions, and some of them (such as the users metric) have to be calculated specifically for every query. It's easy to underestimate the flexibility of Google Analytics, but the fact that it's easy to apply a carefully defined segment to three-year old data in real time means that the data will be stored in a horrendously complicated format, which is kept away from you for proprietary purposes.\nSo the data set would be vast, and incomprehensible. On top of that, there would be serious ramifications with regard to privacy, because of the way that Google stores the data (an issue which they can circumvent so long as you can only access the data through their protocols.\nShort answer, you can take as much data as you can accurately describe and ask for, but there's no 'download all' button.","Q_Score":1,"Tags":"python,google-analytics,google-api,google-analytics-api","A_Id":37029398,"CreationDate":"2016-05-03T07:59:00.000","Title":"Query all data of a Google Analytcs account","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":1,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I want to install MySQL-python-1.2.5 on an old Linux (Debian) embedded system.\nPython is already installed together with a working MariaDB\/MySQL database.\nProblems: \n1) the system is managed remotely and has no direct internet access;\n2) band is infinitesimal to install further apps\/libraries, so I would avoid doing this if possible;\n3) gcc and mysql_config not installed. \nMy question: is there any possibility to add the MYSQL-PYTHON package already READY to be imported into a python script, compiled and as a single file even better, without going through a painful and local upgrade?\nMy dream: prepare the working package\/file on my local PC and then transfer it using SCP.\nNote: the remote system and my working pc are compatible and I don't need any special toolchain.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":570,"Q_Id":37022937,"Users Score":3,"Answer":"have you tried the .deb files from here packages.debian.org\/wheezy\/python-mysqldb","Q_Score":0,"Tags":"python,mysql","A_Id":37024496,"CreationDate":"2016-05-04T08:56:00.000","Title":"How to install MySQL for python WITHOUT internet access","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am working on a Django project with another developer. I had initially created a model which I had migrated and was synced correctly with a MySQL database.\nThe other developer had later pulled the code I had written so far from the repository and added some additional fields to my model.\nWhen I pulled through his changes to my local machine the model had his changes, and additionly a second migration file had been pulled.\nSo I then executed the migration commands:\npython manage.py makemigrations myapp, then python manage.py migrate in order to update my database schema. The response was that no changes had been made.\nI tried removing the migration folder in my app and running the commands again. A new migrations folder had been generated and again my database schema had not been updated.\nIs there something I am missing here? I thought that any changes to model can simply be migrated to alter the database schema.\nAny help would be greatly appreciated. (Using Django version 1.9).","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":881,"Q_Id":37044634,"Users Score":0,"Answer":"After you pull, do not delete the migrations file or folder. Simply just do python manage.py migrate. Even after this there is no change in database schema then open the migrations file which came through the git pull and remove the migration code of the model whose table is not being created in the database. Then do  makemigrations and migrate. I had this same problem. This worked for me.","Q_Score":0,"Tags":"python,django,git","A_Id":56626356,"CreationDate":"2016-05-05T07:12:00.000","Title":"Django model changes cannot be migrated after a Git pull","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"As the title suggests, I'm trying to use a environment variable in a config file for a Flask project (in windows 10). \nI'm using a virtual env and this far i have tried to add set \"DATABASE_URL=sqlite:\/\/\/models.db\" to \/Scripts\/activate.bat in the virtualenv folder. \nBut it does not seem to work. Any suggestions?","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":2106,"Q_Id":37046677,"Users Score":0,"Answer":"The problem was that PyCharm does not activate the virtualenvironment when pressing the run button. It only uses the virtualenv python.exe.","Q_Score":4,"Tags":"python,windows,flask,pycharm,virtualenv","A_Id":37236689,"CreationDate":"2016-05-05T09:10:00.000","Title":"Setting environment variables in virtualenv (Python, Windows)","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Afternoon,\nI have a really simple python script in which user is asked to input a share purchase price, script looks up price and returns whether user is up or down.\nCurrently the input, and text output are done in the CMD prompt which is not ideal. I would love to have in excel a box for inputing purchase price, a button to press and then a cell in which the output is printed.\nIs there any straightforward ways to put the python code in the button code where you would normally have VBA? Or alternative hacks?\nThanks in advance","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":890,"Q_Id":37052571,"Users Score":0,"Answer":"For windows, the win32com package will allow you to control excel from a python script.  It's not quite the same as embedding the code, but it will allow you to read and write from the spreadsheet.","Q_Score":0,"Tags":"python,excel,vba","A_Id":37052827,"CreationDate":"2016-05-05T13:58:00.000","Title":"Python script input and output in excel","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have downloaded a PG database backup from my Heroku App, it's in my repository folder as latest.dump\nI have installed postgres locally, but I can't use pg_restore on the windows command line, I need to run this command: \npg_restore --verbose --clean --no-acl --no-owner -j 2 -h localhost -d DBNAME latest.dump\nBut the command is not found!","AnswerCount":1,"Available Count":1,"Score":0.761594156,"is_accepted":false,"ViewCount":10221,"Q_Id":37104193,"Users Score":5,"Answer":"Since you're on windows, you probably just don't have pg_restore on your path.\nYou can find pg_restore in the bin of your postgresql installation e.g. c:\\program files\\PostgreSQL\\9.5\\bin.\nYou can navigate to the correct location or simply add the location to your path so you won't need to navigate always.","Q_Score":4,"Tags":"python,django,database,postgresql,heroku","A_Id":37104332,"CreationDate":"2016-05-08T19:55:00.000","Title":"How to use pg_restore on Windows Command Line?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I have to compare two MySql database data, I want to compare two MySql schema and find out the difference between both schema.\nI have created two variables Old_Release_DB and New_Release_DB. In Old_Release_DB I have stored old release schema than after some modification like I deleted some column, Added some column, Renamed some column, changed column property like increase datatype size (ex: varchar(10) to varchar(50)). Than it became new release schema that I have stored in  New_Release_DB.\nNow I want to Table Name, list of column name which has changed in New_Release_DB, and changes along with column name.\nExample,\nTable_A Column_Name Add(if it is added),\nTable_A Column_Name Delete(if it is deleted),\nTable_A Column_Name Change(if its property has changed)\nI am trying it in Shell script in Linux, But I am not getting it. Please let me know If I can use other script like python or java.","AnswerCount":3,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":3461,"Q_Id":37109762,"Users Score":0,"Answer":"I use mysql Workbench which has the schema synchronization utility. Very handy when trying to apply changes from development server to a production server.","Q_Score":1,"Tags":"javascript,python,mysql,linux,shell","A_Id":39398778,"CreationDate":"2016-05-09T07:15:00.000","Title":"How to compare two MySql database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have to compare two MySql database data, I want to compare two MySql schema and find out the difference between both schema.\nI have created two variables Old_Release_DB and New_Release_DB. In Old_Release_DB I have stored old release schema than after some modification like I deleted some column, Added some column, Renamed some column, changed column property like increase datatype size (ex: varchar(10) to varchar(50)). Than it became new release schema that I have stored in  New_Release_DB.\nNow I want to Table Name, list of column name which has changed in New_Release_DB, and changes along with column name.\nExample,\nTable_A Column_Name Add(if it is added),\nTable_A Column_Name Delete(if it is deleted),\nTable_A Column_Name Change(if its property has changed)\nI am trying it in Shell script in Linux, But I am not getting it. Please let me know If I can use other script like python or java.","AnswerCount":3,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":3461,"Q_Id":37109762,"Users Score":0,"Answer":"You can compare two databases by creating database dumps:\nmysqldump -u your-database-user your-database-name > database-dump-file.sql - if you're using a password to connect to a database, also add -p option to a mysqldump command.\nAnd then compare them with diff:\ndiff new-database-dump-file.sql old-database-dump-file.sql\nOptionally, you can save the results of diff execution to a file with STDOUT redirecting  by adding > databases_diff to a previous command.\nHowever, that kind of comparison would require some eye work - you will get literally a difference between two files.","Q_Score":1,"Tags":"javascript,python,mysql,linux,shell","A_Id":37110095,"CreationDate":"2016-05-09T07:15:00.000","Title":"How to compare two MySql database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm working on a project which involves a huge external dataset (~490Gb) loaded in an external database (MS SQL through django-pyodbc-azure). I've generated the Django models marked managed=False in their meta. In my application this works fine, but I can't seem to figure out how to run my unit tests. I can think of two approaches: mocking the data in a test database, and giving the unit tests (and CI) read-only access to the production dataset. Both options are acceptable, but I can't figure out either of them:\nOption 1: Mocked data\nBecause my models are marked managed=False, there are no migrations, and as a result, the test runner fails to create the database.\nOption 2: Live data\ndjango-pyodbc-azure will attempt to create a test database, which fails because it has a read-only connection. Also I suspect that even if it were allowed to do so, the resulting database would be missing the required tables.\nQ How can I run my unittests? Installing additional packages, or reconfiguring the database is acceptable. My setup uses django 1.9 with postgresql for the main DB.","AnswerCount":1,"Available Count":1,"Score":0.3799489623,"is_accepted":false,"ViewCount":299,"Q_Id":37115070,"Users Score":2,"Answer":"After a day of staring at my screen, I found a solution:\nI removed the managed=True from the models, and generated migrations. To prevent actual migrations against the production database, I used my database router to prevent the migrations. (return False in allow_migrate when for the appropriate app and database).\nIn my settings I detect whether unittests are being run, and then just don't define the database router or the external database. With the migrations present, the unit tests.","Q_Score":1,"Tags":"python,django,unit-testing","A_Id":37130919,"CreationDate":"2016-05-09T11:50:00.000","Title":"Unit tests with an unmanaged external read-only database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Just set up an IPython Notebook on Ubuntu 16.04 but I can't use %load_ext sql.\nI get: ImportError: No module named sql\nI've tried using pip and pip3 with and without sudo to install ipython-sql. All 4 times it installed without issue but nothing changes on the notebook.\nThanks in advance!","AnswerCount":4,"Available Count":3,"Score":0.049958375,"is_accepted":false,"ViewCount":19909,"Q_Id":37149748,"Users Score":1,"Answer":"I know this answer will be (very) late to contribute to the discussion but maybe it will help someone. I found out what worked for me by following Thomas, who commented above. However, with a bit of a caveat, that I was using pyenv to setup and manage python on my local machine.\nSo when running sys.executable in a jupyter notebook cell I found out my python path was \/usr\/local\/Cellar\/jupyterlab\/3.2.8\/libexec\/bin\/python3.9, while I expected it to be somewhere along the lines of '\/Users\/<USER_NAME>\/.pyenv\/versions\/3.9.2\/bin\/python'.\nThis error was attributed to me having installed jupyter through command brew install jupyter instead of pyenv exec pip install jupyter. I proceeded to uninstall jupyter with brew and then executing the second command, which now got jupyter up and running!\n(note that you would first have to have pyenv setup properly).","Q_Score":12,"Tags":"python,pip,ipython,ipython-sql","A_Id":70772212,"CreationDate":"2016-05-10T22:04:00.000","Title":"IPython Notebook and SQL: 'ImportError: No module named sql' when running '%load_ext sql'","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"Just set up an IPython Notebook on Ubuntu 16.04 but I can't use %load_ext sql.\nI get: ImportError: No module named sql\nI've tried using pip and pip3 with and without sudo to install ipython-sql. All 4 times it installed without issue but nothing changes on the notebook.\nThanks in advance!","AnswerCount":4,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":19909,"Q_Id":37149748,"Users Score":0,"Answer":"I doubt you're using different IPython Notebook kernel other than which you've installed ipython-sql in.\nIPython Notebook can have more than one kernel. If it is the case, make sure you're in the right place first.","Q_Score":12,"Tags":"python,pip,ipython,ipython-sql","A_Id":54436119,"CreationDate":"2016-05-10T22:04:00.000","Title":"IPython Notebook and SQL: 'ImportError: No module named sql' when running '%load_ext sql'","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"Just set up an IPython Notebook on Ubuntu 16.04 but I can't use %load_ext sql.\nI get: ImportError: No module named sql\nI've tried using pip and pip3 with and without sudo to install ipython-sql. All 4 times it installed without issue but nothing changes on the notebook.\nThanks in advance!","AnswerCount":4,"Available Count":3,"Score":0.2449186624,"is_accepted":false,"ViewCount":19909,"Q_Id":37149748,"Users Score":5,"Answer":"I know it's been a long time, but I faced the same issue, and Thomas' advice solved my problem. Just outlining what I did here.\nWhen I ran sys.executable in the notebook I saw \/usr\/bin\/python2, while the pip I used to install the package was \/usr\/local\/bin\/pip (to find out what pip you are using, just do which pip or sudo which pip if you are installing packages system-wide). So I reinstalled ipython-sql using the following command, and everything worked out just fine.\nsudo -H \/usr\/bin\/python2 -m pip install ipython-sql\nThis is odd since I always install my packages using pip. I'm wondering maybe there's something special about the magic functions in Jupyter.","Q_Score":12,"Tags":"python,pip,ipython,ipython-sql","A_Id":43972590,"CreationDate":"2016-05-10T22:04:00.000","Title":"IPython Notebook and SQL: 'ImportError: No module named sql' when running '%load_ext sql'","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm on Odoo 9, I have an issue when lunching odoo server $odoo.py -r odoo -w password, the localhost:8069 doesn't load and I get an error on terminal \"Peer authentication failed for user \"odoo\"\". \nI already created a user \"odoo\" on postgres.\nWhen lunching $odoo.py I can load the odoo page on browser but I can't create database (as default user).\nIt was working and i already created database but when I logged out I couldn't connect to my database account anymore.\nAny ideas ?","AnswerCount":3,"Available Count":1,"Score":0.3215127375,"is_accepted":false,"ViewCount":23159,"Q_Id":37193143,"Users Score":5,"Answer":"This helped me.\n\nsudo nano \/etc\/postgresql\/9.3\/main\/pg_hba.conf\n\nthen add\n\nlocal all odoo trust\n\nthen restart postgres\n\nsudo service postgresql restart","Q_Score":4,"Tags":"python,postgresql,openerp,odoo-9","A_Id":37199710,"CreationDate":"2016-05-12T16:57:00.000","Title":"Peer authentication failed for user \"odoo\"","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm trying to use a PHP site button to kick off a python script on my server.  When I run it, everything seems fine, on the server I can \"ps ax\" and see that the script is running.\nThe Python script attempts to process some files and write the results to a MySQL database.  When I ultimately check to see that the changes were made to the DB, nothing has happened.  Also, redirecting output shows no errors.\nI have checked to make sure that it's executing (the ps ax)\nI've made sure that all users have access to writing to the output directory (for saving the error report, if there is one)\nI've made sure that the logon to MySql is correct...\nI'm not sure what else to do or check.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":40,"Q_Id":37213568,"Users Score":0,"Answer":"You can check in your web-server logs.(\/var\/www\/log\/apache2\/error.log) if you have apache as your webserver..","Q_Score":0,"Tags":"php,python,mysql","A_Id":37213822,"CreationDate":"2016-05-13T15:10:00.000","Title":"Running a python (with MySQL) script from PHP","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I just created a script with openpyxl to update a xlsx file that we usually update manually every month.\nIt work fine, but the new file lost all the graphs and images that were in the workbook. Is there a way to keep them?","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":3060,"Q_Id":37214983,"Users Score":5,"Answer":"openpyxl version 2.5 will preserve charts in existing files.","Q_Score":5,"Tags":"python,openpyxl","A_Id":37215619,"CreationDate":"2016-05-13T16:25:00.000","Title":"Openpyxl updating sheet and maintaining graphs and images","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am trying to get a project from one machine to another. This project contains a massive log db table. It is too massive. So I exported and imported all db tables except this one via phpmyadmin.\nNo if I run the migrate command I expected django to create everything missing. But it is not.\nHow to make django check for and create missing db tables?\nWhat am I missing, why is it not doing this? I feel like the old syncdb did the job. But the new --run-syncdb does not.\nThank you for your help.","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":2300,"Q_Id":37231032,"Users Score":1,"Answer":"When you exported the data and re-imported it on the other database part of that package would have included the django_migrations table. This is basically a log of all the migrations successfully executed by django.\nSince you have left out only the log table according to you, that should really be the only table that's missing from your schema. Find the entries in django_migrations that correspond to this table and delete them. Then run .\/manage.py migrate again and the table will be created.","Q_Score":1,"Tags":"python,django,django-migrations,django-database,django-1.9","A_Id":37232610,"CreationDate":"2016-05-14T19:35:00.000","Title":"How to create missing DB tables in django?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am retrieving structured numerical data (float 2-3 decimal spaces) via http requests from a server. The data comes in as sets of numbers which are then converted into an array\/list. I want to then store each set of data locally on my computer so that I can further operate on it. \nSince there are very many of these data sets which need to be collected, simply writing each data set that comes in to a .txt file does not seem very efficient. On the other hand I am aware that there are various solutions such as mongodb, python to sql interfaces...ect but i'm unsure of which one I should use and which would be the most appropriate and efficient for this scenario.\nAlso the database that is created must be able to interface and be queried from different languages such as MATLAB.","AnswerCount":3,"Available Count":1,"Score":0.0665680765,"is_accepted":false,"ViewCount":989,"Q_Id":37246342,"Users Score":1,"Answer":"Have you considered HDF5? It's very efficient for numerical data, and is supported by both Python and Matlab.","Q_Score":1,"Tags":"python,sql,arrays,mongodb,database","A_Id":37246905,"CreationDate":"2016-05-16T03:38:00.000","Title":"Python, computationally efficient data storage methods","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm creating a little own game, and I need to solve the problem: where I need to store player's inventory: in database with JSON(text field) or directly in database tables. Which method consume less RAM, and which is faster at all?\nGame server will be written on Python","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":285,"Q_Id":37281218,"Users Score":1,"Answer":"As your required requirements i preferred you to use NoSQL database e.g Mongowith implementation of redisfor memory data storage that gives you more flexibility and performance.It based on objects so helps you for fetching faster","Q_Score":1,"Tags":"python,mysql,json,database","A_Id":37282081,"CreationDate":"2016-05-17T16:01:00.000","Title":"What is better - store player's inventory in JSON(text field in database) or database directly?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm creating a little own game, and I need to solve the problem: where I need to store player's inventory: in database with JSON(text field) or directly in database tables. Which method consume less RAM, and which is faster at all?\nGame server will be written on Python","AnswerCount":2,"Available Count":2,"Score":0.0996679946,"is_accepted":false,"ViewCount":285,"Q_Id":37281218,"Users Score":1,"Answer":"It's probably better to use database tables directly.  That way you can take advantage of other database features such as foreign keys, unique constraints, triggers, and so on.","Q_Score":1,"Tags":"python,mysql,json,database","A_Id":37284304,"CreationDate":"2016-05-17T16:01:00.000","Title":"What is better - store player's inventory in JSON(text field in database) or database directly?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I want to use pymssql on a 24\/7 Linux production app and am worried about stability. As soon as I hear ODBC I start to have reservations, especially on Linux. \nDoes pymssql use ODBC or is it straight to freeTDS?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":184,"Q_Id":37357318,"Users Score":0,"Answer":"No, pymssql does not use ODBC.","Q_Score":0,"Tags":"python,pymssql","A_Id":37366489,"CreationDate":"2016-05-20T23:34:00.000","Title":"Does Linux pymssql use ODBC?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":0},{"Question":"I was running Mongo 2.4 with a replicaset which contains 1 primary, 1 secondary and an arbiter. We were using pymongo 2.6 and mongoengine 0.8.2.\nRecently, we performed an upgrade to Mongo 2.6, and also upgraded pymongo to 2.7.2 and mongoengine to 0.8.7.\nThis setup worked fine for almost 12 hours, after which we started getting the below error :\n[initandlisten] connection refused because too many open connections: 819\nThe ulimit is 1024 which worked perfectly with Mongo 2.4 and hence we have not increased it. Increasing it might solve the problem temporarily but we will hit it again in the future. Somehow the root cause seems to be the inability of Pymongo to close the connections. Any pointers why this happens? \nP.S : When using Mongo 2.4 with pymongo 2.7.2 and mongoengine 0.8.7, everything works well and the max connections are about 250. Only with Mongo 2.6, pymongo 2.7.2 and mongoengine 0.8.7, the number of connections shoot up to 819.","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":586,"Q_Id":37383545,"Users Score":1,"Answer":"So after a lot of struggle and a lot of load testing, we solved the problem by upgrading PyMongo to 2.8.1. PyMongo 2.7.2 is the first version to support MongoDB 2.6 and it sure does have some problems handling connections. Upgrading to PyMongo 2.8.1 helped us resolve the issue. With the same load, the connections do not exceed 250-300.","Q_Score":0,"Tags":"python,mongodb,database-connection,pymongo,mongoengine","A_Id":37915282,"CreationDate":"2016-05-23T06:01:00.000","Title":"Too many open connections with mongo 2.6 + pymongo 2.7.2","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have three programs running, one of which iterates over a table in my database non-stop (over and over again in a loop), just reading from it, using a SELECT statement.\nThe other programs have a line where they insert a row into the table and a line where they delete it. The problem is, that I often get an error sqlite3.OperationalError: database is locked.\nI'm trying to find a solution but I don't understand the exact source of the problem (is reading and writing in the same time what make this error occur? or the writing and deleting? maybe both aren't supposed to work).\nEither way, I'm looking for a solution. If it were a single program, I could match the database I\/O with mutexes and other multithreading tools, but it's not. How can I wait until the database is unlocked for reading\/writing\/deleting without using too much CPU?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":369,"Q_Id":37413919,"Users Score":0,"Answer":"you need to switch databases..\nI would use the following:\npostgresql as my database \npsycopg2 as the driver \nthe syntax is fairly similar to SQLite and the migration shouldn't be too hard for you","Q_Score":0,"Tags":"python,sqlite","A_Id":37414407,"CreationDate":"2016-05-24T12:41:00.000","Title":"Lock and unlock database access - database is locked","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am getting a UnicodeDecodeError in my Python script and I know that the unique character is not in Latin (or English), and I know what row it is in (there are thousands of columns).  How do I go through my SQL code to find this unique character\/these unique characters?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":30,"Q_Id":37425230,"Users Score":1,"Answer":"Do a binary search. Break the files (or the scripts, or whatever) in half, and process both files. One will (should) fail, and the other shouldn't. If they both have errors, doesn't matter, just pick one.\nContinue splitting the broken files until you've narrowed it down to the something more manageable that you can probe in to, even down to the actual line that's failing.","Q_Score":0,"Tags":"python,sql","A_Id":37892058,"CreationDate":"2016-05-24T22:57:00.000","Title":"How do I find unique, non-English characters in a SQL script that has a lot of tables, scripts, etc. related to it?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"It is possible [in any way, even poorly hacked solution] to share in-memory database between many processes? My application has one process that opens the in-memory database and the other are running only SELECT queries on the database.\nNOTE: I need solution only for python 2.7, and btw if it matters the module I use for making new processes is multiprocessing.","AnswerCount":1,"Available Count":1,"Score":0.537049567,"is_accepted":false,"ViewCount":850,"Q_Id":37434949,"Users Score":3,"Answer":"On Linux you can just use \/dev\/shm as the file location of your sqlite.\nThis is a memory mounted drive suitable exactly for that.","Q_Score":3,"Tags":"python,database,sqlite,multiprocessing","A_Id":39020351,"CreationDate":"2016-05-25T10:52:00.000","Title":"Share in-memory database between processes sqlite","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a Python script which user's drag and drop KML files into for easy use. It takes the dropped file as sys.arg[1]. When entered into the command line as myScript.py Location.kml everything works fine. But when I drag and drop the file in an error is thrown saying no module named xlsxwriter. xlsxwriter is in the same folder as my Python script in another folder named Packages. Why does it work for the command line but not when dragged and dropped? Is there some trick I am missing?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":290,"Q_Id":37449333,"Users Score":0,"Answer":"Thanks to erkysun this issue was solved! eryksun's solution worked perfectly and I found another reason it wasn't working. This was because when I dragged and dropped the file into the python script then ran os.getcwd() no matter where the file was it returned C:\\WINDOWS\\system32. To counteract this wherever I had os.getcwd() I changed it to os.path.abspath(os.path.dirname(__file__)) and then it worked!","Q_Score":0,"Tags":"python,windows,drag-and-drop,xlsxwriter","A_Id":37449798,"CreationDate":"2016-05-25T23:41:00.000","Title":"Module not found when drag and drop Python file","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a results analysing spreadsheet where i need to enter my raw data into a 8x6 cell 'plate' which has formatted cells to produce the output based on a graph created. This .xlsx file is heavily formatted with formulas for the analysis, and it is a commercial spreadsheet so I cannot replicate these formulas. \nI am using python 2.7 to obtain the raw results into a list and I have tried using xlwt and xlutils to copy the spreadsheet to enter the results. When I do this it loses all formatting when I save the file. I am wondering whether there is a different way in which I can make a copy of the spreadsheet to enter my results. \nAlso when I have used xlutils.copy I can only save the file as a .xls file, not an xlsx, is this the reason why it loses formatting?","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":2214,"Q_Id":37455466,"Users Score":0,"Answer":"While Destrif is correct, xlutils uses xlwt which doesn't support the .xlsx file format.\nHowever, you will also find that xlsxwritter is unable to write xlrd formatted objects.\nSimilarly, the python-excel-cookbook he recommends only works if you are running Windows and have excel installed. A better alternative for this would be xlwings as it works for Windows and Mac with Excel installed.\nIf you are looking for something more platform agnostic, you could try writing your xlsx file using openpyxl.","Q_Score":2,"Tags":"python,excel,formatting,xlwt,xlutils","A_Id":50905858,"CreationDate":"2016-05-26T08:28:00.000","Title":"How to enter values to an .xlsx file and keep formatting of cells","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"abort MySQLdb.\nI know many process not use same connect, Because this will be a problem .  \nBUT, run the under code , mysql request is block , then many process start to query sql at the same time , the sql is \"select sleep(10)\" , They are one by one. \nI not found code abort lock\/mutux in MySQLdb\/mysql.c ,  Why there is no problem ?  I think there will be problems with same connection fd in general .  But pass my test,  only block io, problems not arise . Where is the lock \uff1f\n\nimport time\nimport multiprocessing\nimport MySQLdb\n\ndb = MySQLdb.connect(\"127.0.0.1\",\"root\",\"123123\",\"rui\" )\n\ndef func(*args):\n    while 1:\n        cursor = db.cursor()\n        cursor.execute(\"select sleep(10)\")\n        data = cursor.fetchall()\n        print len(data)\n        cursor.close()\n        print time.time()\n        time.sleep(0.1)\n\nif __name__ == \"__main__\":\n    task = []\n\n    for i in range(20):\n        p = multiprocessing.Process(target = func, args = (i,))\n        p.start()\n        task.append(p)\n    for i in task:\n        i.join()\n\n\nresult log, we found each request interval is ten seconds. \n\n1\n1464325514.82\n1\n1464325524.83\n1\n1464325534.83\n1\n1464325544.83\n1\n1464325554.83\n1\n1464325564.83\n1\n1464325574.83\n1\n1464325584.83\n1\n1464325594.83\n1\n1464325604.83\n1\n1464325614.83\n1\n1464325624.83\n\n\ntcpdump log:\nwe found each request interval is ten seconds two. \n\n13:07:04.827304 IP localhost.44281 > localhost.mysql: Flags [.], ack 525510411, win 513, options [nop,nop,TS val 2590846552 ecr 2590846552], length 0\n    0x0000:  4508 0034 23ad 4000 4006 190d 7f00 0001  E..4#.@.@.......\n    0x0010:  7f00 0001 acf9 0cea fc09 7cf9 1f52 a70b  ..........|..R..\n    0x0020:  8010 0201 ebe9 0000 0101 080a 9a6d 2e58  .............m.X\n    0x0030:  9a6d 2e58                                .m.X\n13:07:04.928106 IP localhost.44281 > localhost.mysql: Flags [P.], seq 0:21, ack 1, win 513, options [nop,nop,TS val 2590846653 ecr 2590846552], length 21\n    0x0000:  4508 0049 23ae 4000 4006 18f7 7f00 0001  E..I#.@.@.......\n    0x0010:  7f00 0001 acf9 0cea fc09 7cf9 1f52 a70b  ..........|..R..\n    0x0020:  8018 0201 fe3d 0000 0101 080a 9a6d 2ebd  .....=.......m..\n    0x0030:  9a6d 2e58 1100 0000 0373 656c 6563 7420  .m.X.....select.\n    0x0040:  736c 6565 7028 3130 29                   sleep(10)\n\n13:07:14.827526 IP localhost.44281 > localhost.mysql: Flags [.], ack 65, win 513, options [nop,nop,TS val 2590856553 ecr 2590856552], length 0\n    0x0000:  4508 0034 23af 4000 4006 190b 7f00 0001  E..4#.@.@.......\n    0x0010:  7f00 0001 acf9 0cea fc09 7d0e 1f52 a74b  ..........}..R.K\n    0x0020:  8010 0201 9d73 0000 0101 080a 9a6d 5569  .....s.......mUi\n    0x0030:  9a6d 5568                                .mUh\n13:07:14.927960 IP localhost.44281 > localhost.mysql: Flags [P.], seq 21:42, ack 65, win 513, options [nop,nop,TS val 2590856653 ecr 2590856552], length 21\n    0x0000:  4508 0049 23b0 4000 4006 18f5 7f00 0001  E..I#.@.@.......\n    0x0010:  7f00 0001 acf9 0cea fc09 7d0e 1f52 a74b  ..........}..R.K\n    0x0020:  8018 0201 fe3d 0000 0101 080a 9a6d 55cd  .....=.......mU.\n    0x0030:  9a6d 5568 1100 0000 0373 656c 6563 7420  .mUh.....select.\n    0x0040:  736c 6565 7028 3130 29                   sleep(10)\n\n```\n```\nend.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":571,"Q_Id":37475338,"Users Score":0,"Answer":"It works contingency.\nMySQL is request-rensponse protocol.\nWhen two process sends query, it isn't mixed unless the query is large.\nMySQL server (1) receive one query, (2) send response of (1), (3) receive next query, (4) send response of (3).\nWhen first response was send from MySQL server, one of two processes receives it.  Since response is small enough, it is received by atomic.\nAnd next response is received by another process.\nTry sending \"SELECT 1+2\" from one process and \"SELECT 1+3\" from another process.  \"1+2\" may be 4 by chance and \"SELECT 1+3\" may be 3 by chance.","Q_Score":0,"Tags":"mysql,linux,mysql-python,pymysql","A_Id":37517765,"CreationDate":"2016-05-27T05:15:00.000","Title":"use multiprocessing to query in same mysqldb connect , block?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I was writing a PL\/Python function for PostgreSQl, with Python 2.7 and Python 3.5 already installed on Linux.\nWhen I was trying to create extension plpythonu, I got an error, then I fixed executing in terminal the command $ sudo apt-get install postgresql-contrib-9.3 postgresql-plpython-9.3. I understand that this is some other package.\nIf I will not have Python 2.7\/3.5 installed, and I will install the plpython package, will the user defined function still work? Is some how the PL\/Python depending on Python?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":278,"Q_Id":37487072,"Users Score":0,"Answer":"Yes, it will, the package is independent from standard python installation.","Q_Score":0,"Tags":"python,postgresql,plpython","A_Id":42190637,"CreationDate":"2016-05-27T15:19:00.000","Title":"PL\/Python in PostgreSQL","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":0},{"Question":"I tried to use pandas to read an excel sheet into a dataframe but for floating point columns, the data is read incorrectly. I use the function read_excel() to do the task\nIn excel, the value is 225789.479905466 while in the dataframe, the value is 225789.47990546614 which creates discrepancy for me to import data from excel to database.  \nDoes anyone face the same issue with pandas.read_exel(). I have no issue reading a csv to dataframe.\nJeremy","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":4533,"Q_Id":37492173,"Users Score":0,"Answer":"Excel might be truncating your values, not pandas. If you export to .csv from Excel and are careful about how you do it, you should then be able to read with pandas.read_csv and maintain all of your data. pandas.read_csv also has an undocumented float_precision kwarg, that might be useful, or not useful.","Q_Score":4,"Tags":"python,excel,pandas,dataframe,precision","A_Id":37596921,"CreationDate":"2016-05-27T20:59:00.000","Title":"loss of precision when using pandas to read excel","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"py.test sets up a test database.  \nI'd like to use the real database set in settings.py file.\n(Since I'm on test machine with test data already)  \nWould it be possible?","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1804,"Q_Id":37507458,"Users Score":0,"Answer":"yeah you can override the settings on the setUp\n set the real database for the tests and load your databases fixtures.. but I think, it`s not a good pratice, since you want to run yours tests without modify your \"real\" app env.\nyou should try the pytest-django. \nwith this lib you can reuse, create drop your databases test.","Q_Score":1,"Tags":"python,django,pytest","A_Id":37513426,"CreationDate":"2016-05-29T07:46:00.000","Title":"Django py.test run on real database?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"So I have a database that stores a lot of information about many different objects; to simplify it, just imagine a database that stores information about the weights of 100 dogs and 100 cats over a period of a few years. I made a GUI, and I want one of the tabs to allow the user to enter a newly taken weight or change the past weight of a pet if it was wrong. \nI created the GUI using Qt Designer. Before, I communicated with the database using SqlAlchemy. However, PyQt4 also offers QtSql, which I think is another ORM? Could someone explain to me how the ORM exactly works, and what the difference is between SqlAlchemy, QtSql, and even Sql Connector?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":2414,"Q_Id":37578763,"Users Score":0,"Answer":"Qt Sql is the SQL Framework that comes with Qt library. It provides basic (and classic) classes to access a database, execute queries and fetch the results.*Qt can be recompiled to support various DBMS such as MySQL, Postgres etc.\nSql Connector\nI assume you refer to MySql Connector ?\nIf so, it's a set of C++ classes to access natively a MySql database.\nClasses are almost the same than those in QtSQL. But you don't have to support the Wrapper layer of Qt. But of course, you cannot access another database than MySQL.\nSql Alchemy\nIt's hard to briefly explain the complexity of an ORM.\nObject Relation Mapping. Wikipedia says:\n\n\"A technique for converting data between incompatible type systems in\n  object-oriented programming languages\"\n\nIt's a good definition. It's basically a technique to map table \/ queries data into Object-Oriented data structure. \nFor example, an ORM engine hides the process that explicitly maps the fields of a TABLE to an OO class.\nIn addition, it works the same whatever the database you're accessing (as long as the ORM knows the DBMS dialect).\nFor such a purpose, Python language and philosophy perfectly fits an ORM. \nBut an ORM such as SqlAlchemy is everything but an Object-Oriented Database !\nIt has some limitations though.\nIf you need to make complex queries (and believe me, it often happens in specific contexts), it becomes a bit tricky to use it properly and you might experience performance penalties. \nIf you need just need to access a single table with hundreds records...it won't be worth it as the initialization process is a bit laborious.\nZ.","Q_Score":0,"Tags":"python,mysql,orm,sqlalchemy,pyqt","A_Id":37579094,"CreationDate":"2016-06-01T21:05:00.000","Title":"Which ORM to use for Python and MySql?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Use case: I'm writing a backend using MongoDB (and Flask).  At the moment this is not using any ORM like Mongoose\/Mongothon.  I'd like to store the _id of the user which created each document in the document.  I'd like it to be impossible to modify that field after creation.  The backend currently allows arbitrary updates using (essentially) collection.update_one({\"_id\": oid}, {\"$set\": request.json})\nI could filter out the _creator_id field from request.json (something like del request.json[\"_creator_id\"]) but I'm concerned that doesn't cover all possible ways in which the syntax could be modified to cause the field to be updated (hmm, dot notation?).  Ideally I'd like a way to make fields write-once in MongoDB itself, but failing that, some bulletproof way to prevent updates of a field in code.","AnswerCount":2,"Available Count":1,"Score":0.2913126125,"is_accepted":false,"ViewCount":3632,"Q_Id":37580165,"Users Score":3,"Answer":"imho there is no know methods to prevent updates inside mongo.\nAs you can control app behavior, then someone will still able to make this update outside the app. Mongo don't have triggers - which in sql world have the possibility to play as a data guards and prevent field changes.\nAs you re not using ODM, then all you can have is CQRS pattern which will allow you to control app behavior and prevent such updates.","Q_Score":2,"Tags":"python,json,node.js,mongodb,immutability","A_Id":38043469,"CreationDate":"2016-06-01T23:03:00.000","Title":"How to make a field immutable after creation in MongoDB?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"From my understanding BigTable is a Column Oriented NoSQL database. Although Google Cloud Datastore is built on top of Google\u2019s BigTable infrastructure I have yet to see documentation that expressively says that Datastore itself is a Column Oriented database. The fact that names reserved by the Python API are enforced in the API, but not in the Datastore itself makes me question the extent Datastore mirrors the internal workings of BigTable. For example, validation features in the ndb.Model class are enforced in the application code but not the datastore. An entity saved using the ndb.Model class can be retrieved someplace else in the app that doesn't use the Model class, modified, properties added, and then saved to datastore without raising an error until loaded into a new instance of the Model class. With that said, is it safe to say Google Cloud Datastore is a Column Oriented NoSQL database? If not, then what is it?","AnswerCount":1,"Available Count":1,"Score":0.537049567,"is_accepted":false,"ViewCount":429,"Q_Id":37602604,"Users Score":3,"Answer":"Strictly speaking, Google Cloud Datastore is distributed multi-dimensional sorted map. As you mentioned it is based on Google BigTable, however, it is only a foundation.\nFrom high level point of view Datastore actually consists of three layers.\nBigTable\nThis is a necessary base for Datastore. Maps row key, column key and timestamp (three-dimensional mapping) to an array of bytes. Data is stored in lexicographic order by row key.\n\nHigh scalability and availability\nStrong consistency for single row\nEventual consistency for multi-row level\n\nMegastore\nThis layer adds transactions on top of the BigTable.\nDatastore\nA layer above Megastore. Enables to run queries as index scans on BigTable. Here index is not used for performance improvement but is required for queries to return results.\nFurthermore, it optionally adds strong consistency for multi-row level via ancestor queries. Such queries force the respective indexes to update before executing actual scan.","Q_Score":1,"Tags":"python,google-app-engine,google-cloud-datastore","A_Id":37609672,"CreationDate":"2016-06-02T21:41:00.000","Title":"Is Google Cloud Datastore a Column Oriented NoSQL database?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"Is it possible to access same mysql database using python and php.Beacause I am developing a video searching website which based on semantics. Purposely I have to use python and JavaEE. So I have to make a datbase to store video data. But it should be accessed through both python and javaEE, I can use php to interfacing between javaEE mysql database. But my problem is python can access the same database.?\nI new to here and developing. I appreciate your kindness. Think I can get a best solution","AnswerCount":2,"Available Count":2,"Score":0.0996679946,"is_accepted":false,"ViewCount":96,"Q_Id":37757927,"Users Score":1,"Answer":"It's a database. It doesn't care what language or application you're using too access it. That's one of the benefits of having standards like the MySQL protocol, SQL in general, or even things like TCP\/IP: They allow different systems to seamlessly inter-operate.","Q_Score":0,"Tags":"php,python,mysql","A_Id":37759626,"CreationDate":"2016-06-10T22:22:00.000","Title":"can python and php access same mysqldb?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Is it possible to access same mysql database using python and php.Beacause I am developing a video searching website which based on semantics. Purposely I have to use python and JavaEE. So I have to make a datbase to store video data. But it should be accessed through both python and javaEE, I can use php to interfacing between javaEE mysql database. But my problem is python can access the same database.?\nI new to here and developing. I appreciate your kindness. Think I can get a best solution","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":96,"Q_Id":37757927,"Users Score":0,"Answer":"Like @tadman said, yes.\nAll you care about is making a new connection and obtaining a cursor in each of your program (no matter what language).\nThe cursor is what does what you want (analogous to executing an actual query in whatever program you're using).","Q_Score":0,"Tags":"php,python,mysql","A_Id":37760285,"CreationDate":"2016-06-10T22:22:00.000","Title":"can python and php access same mysqldb?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"As the title says, simple question...\nWhen to use pyodbc and when to use jaydebeapi in Python 2\/3?\nLet me elaborate with a couple of example scenarios...\n\nIf I were a solution architect and am looking at a Pyramid Web Server looking to access multiple RDBMS types (HSQLDB, Maria, Oracle, etc) with the expectation of heavy to massive concurrency and need for performance in latency in a monolithic web server, which paradigm would be chosen? And why?\nIf I were to implement an Enterprise Microservice solution (a.k.a. the new SOA) with each microservice accessing specific targeted RDBMS but with heavy load and perfomance latency requirements each, which paradigm would be chosen? And why?\n\nTraditionally JDBCs performed significantly better in large Enterprise solutions requiring good concurrency.  Are the same idiosyncracies prevalent in Python ?  Is there another way besides the two mentioned above?\nI am new to Python so please be patient if my question doesn't make sense and I'll attempt to elaborate further.  It is best to think about my question from a high-level solution design then going from the ground up as a developer.  What would you mandate as the paradigm if you were the sol-architect?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1110,"Q_Id":37792956,"Users Score":2,"Answer":"Simple answer - until more details given in question:\nIn case you want to speak ODBC with the database: Go with pyodbc or for a pure python solution with pypyodbc\nElse if you want to talk JDBC with the database try jaydebeapi \nThis should depend mor on the channel you want to use between python and the database and less on the version of python you are using.","Q_Score":1,"Tags":"python,python-3.x,pyodbc,jaydebeapi","A_Id":37793124,"CreationDate":"2016-06-13T14:54:00.000","Title":"When to use pyodbc and when to use jaydebeapi in Python 2\/3?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm using a python driver (mysql.connector) and do the following:\n_db_config = {\n  'user': 'root',\n  'password': '1111111',\n  'host': '10.20.30.40',\n  'database': 'ddb'\n}\n\n_connection = mysql.connector.connect(**_db_config) # connect to a remote server\n_cursor = _connection.cursor(buffered=True)\n_cursor.execute(\"\"\"SELECT * FROM database LIMIT 1;\"\"\")\n\nIn some cases, the call to _cursor.execute() hangs with no exception\nBy the way, when connecting to a local MySQL server it seems to be ok","AnswerCount":2,"Available Count":1,"Score":-0.0996679946,"is_accepted":false,"ViewCount":1546,"Q_Id":37809163,"Users Score":-1,"Answer":"Moving to MySQLdb (instead of mysql.connector) solved all the issues :-)","Q_Score":1,"Tags":"python,mysql","A_Id":37839311,"CreationDate":"2016-06-14T10:15:00.000","Title":"Call to MySQL cursor.execute() (Python driver) hangs","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm running a python 3.5 worker on heroku.\nself.engine = create_engine(os.environ.get(\"DATABASE_URL\"))\nMy code works on local, passes Travis CI, but gets an error on heroku - OperationalError: (psycopg2.OperationalError) FATAL:  database \"easnjeezqhcycd\" does not exist. \neasnjeezqhcycd is my user, not database name. As I'm not using flask's sqlalchemy, I haven't found a single person dealing with the same person\nI tried destroying my addon database and created standalone postgres db on heroku - same error.\nWhat's different about heroku's URL that SQLAlchemy doesn't accept it? Is there a way to establsih connection using psycopg2 and pass it to SQLAlchemy?","AnswerCount":3,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":2039,"Q_Id":37910066,"Users Score":1,"Answer":"Old question, but the answer seems to be that database_exists and create_database have special case code for when the engine URL starts with postgresql, but if the URL starts with just postgres, these functions will fail.  However, SQLAlchemy in general works fine with both variants.\nSo the solution is to make sure the database URL starts with postgresql:\/\/ and not postgres:\/\/.","Q_Score":1,"Tags":"python,postgresql,heroku,sqlalchemy,heroku-postgres","A_Id":46558758,"CreationDate":"2016-06-19T17:44:00.000","Title":"Heroku SQLAlchemy database does not exist","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm running a python 3.5 worker on heroku.\nself.engine = create_engine(os.environ.get(\"DATABASE_URL\"))\nMy code works on local, passes Travis CI, but gets an error on heroku - OperationalError: (psycopg2.OperationalError) FATAL:  database \"easnjeezqhcycd\" does not exist. \neasnjeezqhcycd is my user, not database name. As I'm not using flask's sqlalchemy, I haven't found a single person dealing with the same person\nI tried destroying my addon database and created standalone postgres db on heroku - same error.\nWhat's different about heroku's URL that SQLAlchemy doesn't accept it? Is there a way to establsih connection using psycopg2 and pass it to SQLAlchemy?","AnswerCount":3,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":2039,"Q_Id":37910066,"Users Score":0,"Answer":"so I was getting the same error and after checking several times I found that I was giving a trailing space in my DATABASE_URL. Which was like DATABASE_URL=\"url<space>\".\nAfter removing the space my code runs perfectly fine.","Q_Score":1,"Tags":"python,postgresql,heroku,sqlalchemy,heroku-postgres","A_Id":62351512,"CreationDate":"2016-06-19T17:44:00.000","Title":"Heroku SQLAlchemy database does not exist","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm quite new to Python and trying to fetch data in HTML and saved to excels using xlwt.\nSo far the program seems work well (all the output are correctly printed on the python console when running the program) except that when I open the excel file, an error message saying 'We found a problem with some content in FILENAME, Do you want us to try to recover as much as we can? If you trust the source of this workbook, click Yes.' And after I click Yes, I found that a lot of data fields are missing. \nIt seems that roughly the first 150 lines are fine and the problem begins to rise after that (In total around 15000 lines). And missing data fields concentrate at several columns with relative high data volume.\nI'm thinking if it's related to sort of cache allocating mechanism of xlwt?\nThanks a lot for your help here.","AnswerCount":1,"Available Count":1,"Score":-0.3799489623,"is_accepted":false,"ViewCount":219,"Q_Id":37925969,"Users Score":-2,"Answer":"seems like a caching issue.\nTry sheet.flush_row_data() every 100 rows or so ?","Q_Score":0,"Tags":"python,xlwt","A_Id":37931428,"CreationDate":"2016-06-20T15:11:00.000","Title":"Python XLWT: Excel generated by Python xlwt contains missing value","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have stored a pyspark sql dataframe in parquet format. Now I want to save it as xml format also. How can I do this? Solution for directly saving the pyspark sql dataframe in xml or converting the parquet to xml anything will work for me. Thanks in advance.","AnswerCount":2,"Available Count":1,"Score":-0.0996679946,"is_accepted":false,"ViewCount":992,"Q_Id":37945725,"Users Score":-1,"Answer":"You can map each row to a string with xml separators, then save as text file","Q_Score":0,"Tags":"xml,python-2.7,pyspark,spark-dataframe,parquet","A_Id":37989050,"CreationDate":"2016-06-21T13:24:00.000","Title":"How to save a pyspark sql DataFrame in xml format","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":1,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"As the data retrieving is too slow when I am querying for the whole data at once in MongoDB using the query db.find({}, {'_id':0}).\nI am using PyMongo\nHow can I retrieve all the documents faster using Python driver.\nI think indexing can make data retrieve faster but how to apply Indexing on whole collection to make db.find({}) query for whole collection runs faster.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":117,"Q_Id":37991245,"Users Score":0,"Answer":"Indexing will drastically speed up finding subsets of documents within a collection, but will not (to my knowledge) speed up pulling the entire collection.\nThe reason indexing speeds up finding subsets is that mongo does not have to iterate through each document to see if they match the query- instead mongo can just go to each specific document location by looking it up in the index.\nIf you are returning the entire collection- then the index has no effect. Mongo fundamentally has to iterate through every document in the collection.\nThe storage engine you chose will effect hte speed, so I suggest you read up on the differences between Wired Tiger and mmapV1. I know there are third party ones but can't think of them off the top of my head.","Q_Score":1,"Tags":"python,mongodb,pymongo","A_Id":37991450,"CreationDate":"2016-06-23T12:10:00.000","Title":"How to apply indexing in mongodb to read the whole data at once faster","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have an exelfile that I want to convert but the default type for numbers is float. How can I change it so xlwings explicitly uses strings and not numbers?\nThis is how I read the value of a field:\nxw.Range(sheet, fieldname ).value\nThe problem is that numbers like 40 get converted to 40.0 if I create a string from that. I strip it with: str(xw.Range(sheetFronius, fieldname ).value).rstrip('0').rstrip('.') but that is not very helpful and leads to errors because sometimes the same field can contain both a number and a string. (Not at the same time, the value is chosen from a list)","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":3124,"Q_Id":37996435,"Users Score":0,"Answer":"In my case conclusion was, just adding one row to the last row of raw data.\nWrite any text in the column you want to change to str, save, load, and then delete the last line.","Q_Score":1,"Tags":"python,converter,type-conversion,xlwings","A_Id":70226530,"CreationDate":"2016-06-23T15:53:00.000","Title":"How can I read every field as string in xlwings?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am new at using raspberry pi.\nI have a python 3.4 program that connects to a database on hostinger server.\nI want to install mysql connector in raspberry pi.I searched a lot but I was not able to find answers . any help would be appreciated","AnswerCount":3,"Available Count":1,"Score":0.0665680765,"is_accepted":false,"ViewCount":31314,"Q_Id":38007240,"Users Score":1,"Answer":"Just use $sudo apt-get install python3-mysqldb and it works on pi-3.","Q_Score":4,"Tags":"mysql,python-3.x,raspberry-pi2","A_Id":48172697,"CreationDate":"2016-06-24T06:50:00.000","Title":"installing mysql connector for python 3 in raspberry pi","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a python program that accesses SQL databases with the database login currently encoded in base64 in a text file. I'd like to encode the login instead using MD5 and store it in a config file, but after some research, I couldn't find much on the topic. Could someone point me in the right direction on where to start?","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":397,"Q_Id":38016242,"Users Score":1,"Answer":"MD5, unfortunately, is a hash signature protocol, not an encryption protocol.  It is used to generate strings that are used to detect even the very-slightest change to the value from which the MD5 hash was produced.  But . . . (by design) . . . you cannot recover the value that was originally used to produce the signature!\nIf you are working in a corporate, \"intra-net\" setting, consider using LDAP (Microsoft OpenDirectory) or some other form of authorization\/authentication, in lieu of \"passwords.\"  In this scenario, the security department authorizes your application to do certain things, and they provide you with an otherwise-meaningless token with which to do it.  The database uses the presented token, along with other rules controlled only by the security department, to recognize your script and to grant selected access to it.  The token is \"useless if stolen.\"\nIf you do still need to use passwords, you'll need to find a different way to securely store them.  MD5 cannot be used.","Q_Score":0,"Tags":"python,sql,python-3.x,config,md5","A_Id":38016382,"CreationDate":"2016-06-24T14:49:00.000","Title":"Encrypting a SQL Login in a Python program using MD5","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"simple question - if I run apache 32bit version, on 64bit OS, with a lot of memory (32GB RAM). Does this mean all the memory will go to waste since 32bit apache can't use more then 3GB ram?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":203,"Q_Id":38040240,"Users Score":0,"Answer":"I would assume so. You should definitely go for a 64-bit version of Apache to make use of all the memory available.","Q_Score":0,"Tags":"python,django,apache,32bit-64bit,32-bit","A_Id":38040277,"CreationDate":"2016-06-26T15:45:00.000","Title":"Apache web server 32bit on 64bit computer","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm new to pythonanywhere. I wonder how to load data from local csv files (there are many of them, over 1,000) into a mysql table. Let's say the path for the folder of the csv files is d:\/data. How can I write let pythonanywhere visit the local files? Thank you very much!","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1111,"Q_Id":38045616,"Users Score":2,"Answer":"You cannot get PythonAnywhere to read the files directly off your machine. At the very least, you need to upload the file to PythonAnywhere first. You can do that from the Files tab. Then the link that Rptk99 provided will show you how to import the file into MySQL.","Q_Score":2,"Tags":"database,python-2.7,pythonanywhere","A_Id":38056627,"CreationDate":"2016-06-27T03:46:00.000","Title":"Pythonanywhere Loading data from local files","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"In Python, what is a database \"cursor\" most like?\n\nA method within a class\nA Python dictionary\nA function\nA file handle\n\nI have searched on internet but I am not getting proper justification of this question.","AnswerCount":2,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":2948,"Q_Id":38067324,"Users Score":2,"Answer":"Probably it is most like a file handle.\nThat does not mean that it is a file handle, and a cursor is actually an object - an instance of a Cursor class (depending on the actual db driver in use).\nThe reason that it's similar to a file handle is that you can consume data from it, but (in general) you can't go back to previously consumed data. Consumption of data is therefore unidirectional. Reading from a file handle returns characters\/bytes, reading from a cursor returns rows.","Q_Score":1,"Tags":"python,database,cursor","A_Id":38067434,"CreationDate":"2016-06-28T04:55:00.000","Title":"Database Cursor","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am trying to migrate database from SQL Server is in 172.16.12.116 to MariaDB (Windows) is in 172.16.12.107 through MySQL Workbench 6.1.4.\nSource selection got succeeded. But when I am trying to connect to target I am getting this error:\n\nError during Check target DBMS connection: MySQLError(\"Host '172.16.12.116' is not allowed to connect to this MariaDB server (code 1130)\"): error calling Python module function DbMySQLFE.connect\n\nWhat possibly could be a problem?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":806,"Q_Id":38100722,"Users Score":0,"Answer":"MySQL Workbench only works with MySQL servers, with the exception of migration sources (which can be Postgres, Sybase and others).\nWhat you can do however is first to migrate to a MySQL server and then dump the imported data and import that in MariaDB. Might require a few adjustments then.","Q_Score":0,"Tags":"mysql,python-2.7,mysql-workbench,mariadb","A_Id":38116416,"CreationDate":"2016-06-29T13:15:00.000","Title":"Error during Check target DBMS connection","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a list of variables with unicode characters, some of them for chemicals like Ozone gas: like 'O\\u2083'. All of them are stored in a sqlite database which is read in a Python code to produce O3. However, when I read I get 'O\\\\u2083'. The sqlite database is created using an csv file that contains the string 'O\\u2083' among others. I understand that \\u2083 is not being stored in sqlite database as unicode character but as 6 unicode characters (which would be \\,u,2,0,8,3). Is there any way to recognize unicode characters in this context? Now my first option to solve it is to create a function to recognize set of characters and replace for unicode characters. Is there anything like this already implemented?","AnswerCount":3,"Available Count":1,"Score":0.1325487884,"is_accepted":false,"ViewCount":1263,"Q_Id":38106808,"Users Score":2,"Answer":"SQLite allows you to read\/write Unicode text directly. u'O\\u2083' is two characters u'O' and u'\\u2083' (your question has a typo: 'u\\2083' != '\\u2083').\n\nI understand that u\\2083 is not being stored in sqlite database as unicode character but as 6 unicode characters (which would be u,\\,2,0,8,3)\n\nDon't confuse u'u\\2083' and u'\\u2083': the latter is a single character while the former is 4-character sequence: u'u', u'\\x10' ('\\20' is interpreted as octal in Python), u'8', u'3'.\nIf you save a single Unicode character u'\\u2083' into a SQLite database; it is stored as a single Unicode character (the internal representation of Unicode inside the database is irrelevant as long as the abstraction holds).\nOn Python 2, if there is no from __future__ import unicode_literals at the top of the module then 'abc' string literal creates a bytestring instead of a Unicode string -- in that case both 'u\\2083' and '\\u2083' are sequences of bytes, not text characters (\\uxxxx is not recognized as a unicode escape sequence inside bytestrings).","Q_Score":0,"Tags":"python,sqlite,unicode","A_Id":38146103,"CreationDate":"2016-06-29T17:51:00.000","Title":"Reading unicode characters from file\/sqlite database and using it in Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"i have been trying to connect to SQL Server (I have SQL Server 2014 installed on my machine and SQL Native Client 11.0 32bit as driver) using Python and specifically pyodbc but i did not manage to establish any connection. \nThis is the connection string i am using:\nconn = pyodbc.connect('''DRIVER={SQL Server Native Client 11.0}; SERVER=\/\/123.45.678.910; DATABASE=name_database;UID=blabla;PWD=password''') \nThe error message i am getting is this:\nError: ('08001', '[08001] [Microsoft][SQL Server Native Client 11.0]Named Pipes Provider: Could not open a connection to SQL Server [161].  (161) (SQLDriverConnect)')\nNow, is this caused by the fact that both Python (i have version 3.5.1) and pyodbc are 64bit while the SQL Driver is 32bit? \nIf yes, how do i go about solving this problem?\nHow do i adapt pyodbc to query a 32bit database?\nI am experiencing the same problem with Oracle database  OraCLient11g32_home1 \nFor your information, my machine runs Anaconda 2.5.0 (64-bit).\nAny help would be greatly appreciated.Thank you very much in advance.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":228,"Q_Id":38145048,"Users Score":0,"Answer":"I may be missing something here.  Why don't you connect to your Oracle database as a SQL Server linked server (or the other way around) ?","Q_Score":0,"Tags":"python,sql-server,database,oracle,python-3.x","A_Id":38146099,"CreationDate":"2016-07-01T12:08:00.000","Title":"Database Connection SQL Server \/ Oracle","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I just started using Ipython in Pycharm.\nWhat's the shortcut for insert a cell for Ipython in Pycharm?\n\nTo insert a cell between the 2nd and 3rd cell.\nTo insert a cell at the end of code\n\nAccording to Pycharm documentation, way to add cell as follows.\nBut it doesn't work for me. Anyone find the same issue?\nSince the new cell is added below the current one, click the cell with import statement - its frame becomes green. Then on the toolbar click add (or press Alt+Insert).","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":2299,"Q_Id":38151292,"Users Score":1,"Answer":"I've had the same concern and right now I remembered that you can just write #%% (for code cell) or #%% md (for markdown cell) anywhere you want and it will create a new cell","Q_Score":2,"Tags":"ipython,pycharm","A_Id":70563736,"CreationDate":"2016-07-01T17:49:00.000","Title":"Shortcut for insert a cell below for Ipython in Pycharm?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I want to do a bulk insertion in SQL alchemy and would prefer to remove an index prior to making the insertion, reading it when the insertion is complete.\nI see adding and removing indexes is supported by Alembic for migrations, but is this possible with SQLAlchemy?  If so, how?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1562,"Q_Id":38238858,"Users Score":1,"Answer":"The best method is to just execute sql.  In this casesession.execute(\"DROP INDEX ...\")","Q_Score":1,"Tags":"python,sqlalchemy,migration","A_Id":38949945,"CreationDate":"2016-07-07T06:34:00.000","Title":"Drop and read index using SQLAlchemy","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm currently using a mix of smart view and power query(sql) to load data into Excel models however my excel always crashes when smart view is used. I'm required to work in Excel but I'm know looking at finding a way to periodically load data from Essbase into my SQL server database and only use power query(sql) for all my models. What would be my best options in doing this? Being a Python enthusiast I found essbasepy.py however there isn't much documentation on it. Please help","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":2203,"Q_Id":38270552,"Users Score":0,"Answer":"There are a couple of ways to go. The most straightforward is to export all of the data from your Essbase database using column export, then designing a process to load the data into SQL Server (such as using the import functionality or BULK IMPORT, or SSIS...). \nAnother approach is to use the DataExport calc script command to export either to a file (that you then load into SQL) or directly to the relational database (DataExport can be configured to export data directly to relational). \nIn either case, you will need privileges that are greater than normal user privileges, and either approach involves Essbase automation that may require you to coordinate with the Essbase admin.","Q_Score":0,"Tags":"python,sql-server,excel,hyperion,essbase","A_Id":38299572,"CreationDate":"2016-07-08T15:37:00.000","Title":"Load data from Essbase into SQL database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I work on a raspberry pi project and use Python + Kivy for such reasons:\nI read some string values comming from a device installed in a field every 300ms. \nAs soon as I see certain value I trigger a python thread to run another function which takes the string and stores it in a list and timestamp it.\nMy kivy app displays the value stored in the list and run some other functions.\nThe question is: Is it better approach to save received strings into DB and let kivy read DB or is it better for Python to append list and let to run another function that runs through list and trigger kivy task?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":56,"Q_Id":38295148,"Users Score":0,"Answer":"Both approaches have pros and cons.\nA database is designed to store and query data. You can query data easily (SQL) from multiple processes. If you don't have multiple processes and no complicated querys a database doesn't really offers that much. Maybe persistence if that is a concern for you. If you don't need the features a database offers, don't use one.\nIf you simply want to store a bit data a list is better. It's probably faster because you don't need inter process communication. Also if you store the data in the database you will still need to get it into the python process somehow, and then you will probably put it in a list.\nBased on your requests a database doesn't offer any features you need, so you should go with a simple list.","Q_Score":0,"Tags":"python,database,kivy","A_Id":38304824,"CreationDate":"2016-07-10T18:24:00.000","Title":"is it better to read from LIST or from Database?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"In the Python 3 docs, it states that the dbm module will use gdbm if it's installed. In my script I use from dbm.gnu import open as dbm_open to try and import the module. It always returns with the exception ImportError: No module named '_gdbm'. I've gone to the gnu website and have downloaded the latest version. I installed it using \n.\/configure --enable-libgdbm-compat, make; make check; make install, and it installed with no errors. I can access the man page for the library but I still can't import it into Python 3.5.2 (Anaconda). How do I install the Python module for gdbm?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":2327,"Q_Id":38385630,"Users Score":0,"Answer":"I got similar issue though I am not sure which platform you are using.\nSteps are:\n\nlook for file _gdbm.cpython-\"python version\"-.so example file: _gdbm.cpython-39-darwin.so\nOnce you find the path check which python version in directory path.\nTry creating same python venv.\nExecute your code.\n\nBefore this make sure you have install appropriate gdbm version installed on host machine, for mac it's different for ubuntu it's different name.","Q_Score":5,"Tags":"python-3.x,gdbm","A_Id":70973357,"CreationDate":"2016-07-14T23:13:00.000","Title":"Python: How to Install gdbm for dbm.gnu","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":1,"Web Development":0},{"Question":"Overview: I have data something like this (each row is a string):\n\n81:0A:D7:19:25:7B, 2016-07-14 14:29:13, 2016-07-14 14:29:15, -69, 22:22:22:22:22:23,null,^M\n3B:3F:B9:0A:83:E6, 2016-07-14 01:28:59, 2016-07-14 01:29:01, -36, 33:33:33:33:33:31,null,^M\nB3:C0:6E:77:E5:31, 2016-07-14 08:26:45, 2016-07-14 08:26:47, -65, 33:33:33:33:33:32,null,^M\n61:01:55:16:B5:52, 2016-07-14 06:25:32, 2016-07-14 06:25:34, -56, 33:33:33:33:33:33,null,^M\n\nAnd I want to sort each row based on the first timestamp that is present in the each String, which for these four records is:\n\n2016-07-14 01:28:59\n2016-07-14 06:25:32\n2016-07-14 08:26:45\n2016-07-14 14:29:13\n\nNow I know the sort() method but I don't understand how can I use here to sort all the rows based on this (timestamp) quantity, and I do need to keep the final sorted data in the same format as some other service is going to use it.\nI also understand I can make the key() but I am not clear how that can be made to sort on the timestamp field.","AnswerCount":3,"Available Count":1,"Score":0.0665680765,"is_accepted":false,"ViewCount":358,"Q_Id":38388799,"Users Score":1,"Answer":"you can use string.split()\uff0cstring.split(',')[1]","Q_Score":5,"Tags":"python,list,python-2.7,sorting","A_Id":38389853,"CreationDate":"2016-07-15T05:57:00.000","Title":"Sort A list of Strings Based on certain field","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a dataframe in Python. Can I write this data to Redshift as a new table?\nI have successfully created a db connection to Redshift and am able to execute simple sql queries.\nNow I need to write a dataframe to it.","AnswerCount":7,"Available Count":1,"Score":0.1418931938,"is_accepted":false,"ViewCount":57271,"Q_Id":38402995,"Users Score":5,"Answer":"Assuming you have access to S3, this approach should work:\nStep 1: Write the DataFrame as a csv to S3 (I use AWS SDK boto3 for this)\nStep 2: You know the columns, datatypes, and key\/index for your Redshift table from your DataFrame, so you should be able to generate a create table script and push it to Redshift to create an empty table\nStep 3: Send a copy command from your Python environment to Redshift to copy data from S3 into the empty table created in step 2\nWorks like a charm everytime.\nStep 4: Before your cloud storage folks start yelling at you delete the csv from S3\nIf you see yourself doing this several times, wrapping all four steps in a function keeps it tidy.","Q_Score":32,"Tags":"python,pandas,dataframe,amazon-redshift,psycopg2","A_Id":42047026,"CreationDate":"2016-07-15T18:33:00.000","Title":"How to write data to Redshift that is a result of a dataframe created in Python?","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have an Excel file(xlsx) that already has lots of data in it. Now I am trying to use Python to write new data into this Excel file. I looked at xlwt, xldd, xlutils, and openpyxl, all of these modules requires you to load the data of my excel sheet, then apply changes and save to a new Excel file. Is there any way to just change the data in the existing excel sheet rather than load workbook or saving to new files?","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":5172,"Q_Id":38463258,"Users Score":7,"Answer":"This is not possible because XLSX files are zip archives and cannot be modified in place. In theory it might be possible to edit only a part of the archive that makes up an OOXML package but, in practice this is almost impossible because relevant data may be spread across different files.","Q_Score":1,"Tags":"python,openpyxl,xlrd,xlwt,xlutils","A_Id":38463454,"CreationDate":"2016-07-19T15:52:00.000","Title":"Modifying and writing data in an existing excel file using Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I already have an owl ontology which contains classes, instances and object properties. How can I map them to a relational data base such as MYSQL using a Python as a programming language(I prefer Python) ?\nFor example, an ontology can contains the classes: \"Country and city\" and  instances like: \"United states and NYC\". \nSo I need manage to store them in relational data bases' tables. I would like to know if there is some Python libraries to so.","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1036,"Q_Id":38498290,"Users Score":0,"Answer":"Use the right tool for the job. You're using RDF, that it's OWL axioms is immaterial, and you want to store and query it. Use an RDF database. They're optimized for storing and querying RDF. It's a waste of your time to homegrow storage & query in MySQL when other folks have already figured out how best to do this.\nAs an aside, there is a way to map RDF to a relational database. There's a formal specification for this, it's called R2RML.","Q_Score":1,"Tags":"python,mysql,relational-database,semantic-web,ontology","A_Id":38534519,"CreationDate":"2016-07-21T07:56:00.000","Title":"How can I map an ontology components to a relational database?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I need to create a dashboard based upon an excel table and I know excel has a feature for creating dashboards. I have seen tutorials on how to do it and have done my research, but in my case, the excel table on which the dashboard would be based is updated every 2 minutes by a python script. My question is, does the dashboard display automatically if a value in the table has modified, or does it need to be reopened, reloaded, etc..?","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":1488,"Q_Id":38518227,"Users Score":1,"Answer":"If the \"dashboard\" is in Excel and if it contains charts that refer to data in the current workbook's worksheets, then the charts will update automatically when the data is refreshed, unless the workbook calculation mode is set to \"manual\". By default calculation mode is set to \"automatic\", so changes in data will immediately reflect in charts based on that data.\nIf the \"dashboard\" lives in some other application that looks at the Excel workbook for the source data, you may need to refresh the data connections in the dashboard application after the Excel source data has been refreshed.","Q_Score":0,"Tags":"python,excel,dashboard","A_Id":38520493,"CreationDate":"2016-07-22T04:33:00.000","Title":"Can Excel Dashboards update automatically?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Would that be possible to create programatically a new OGC WMS (1.1\/1\/3) service using:\n\nPython\nMapProxy\nMapnik\nPostGIS\/Postgres\n\nany script\/gist or sample would be more then appreciated.\nCheers, M","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":662,"Q_Id":38524212,"Users Score":0,"Answer":"If we are looking for publish data in postgres to WMS, enable tilecache, and use more advanced rendering engine like mapnik, then I would say there could be one component missing is the GIS server.\nSo if I am guessing your requirement correctly as I mentioned earlier then here is what the system design could be:\n\nUse postgres\/postgis as database connection.\nWrite your own server side program using python to create the\nservice definition file for the dynamic WMS (mapfile if you are\ngoing to use MapServer).\nThen your program handling tilecache\/tile seeding by change the\nconfiguration file (.yaml) in mapproxy.\nThen escalate WMS to mapnik for rendering and expose the output.\nLike someone else mentioned, it would be easy to have a template\nconfiguration file for each step and do parameter substitution.","Q_Score":0,"Tags":"python,postgis,mapnik","A_Id":39417434,"CreationDate":"2016-07-22T10:32:00.000","Title":"python script for creating maproxy OGC WMS service using Mapnik and PostGIS","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am writing a Django application that will have entries entered by users of the site. Now suppose that everything goes well, and I get the expected number of visitors (unlikely, but I'm planning for the future). This would result in hundreds of millions of entries in a single PostgreSQL database.\nAs iterating through such a large number of entries and checking their values is not a good idea, I am considering ways of grouping entries together.\nIs grouping entries in to sets of (let's say) 100 a better idea for storing this many entries? Or is there a better way that I could optimize this?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":66,"Q_Id":38585719,"Users Score":1,"Answer":"Store one at a time until you absolutely cannot anymore, then design something else around your specific problem.\nSQL is a declarative language, meaning \"give me all records matching X\" doesn't tell the db server how to do this.  Consequently, you have a lot of ways to help the db server do this quickly even when you have hundreds of millions of records.  Additionally RDBMSs are optimized for this problem over a lot of years of experience so to a certain point, you will not beat a system like PostgreSQL.\nSo as they say, premature optimization is the root of all evil.\nSo let's look at two ways PostgreSQL might go through a table to give you the results.\nThe first is a sequential scan, where it iterates over a series of pages, scans each page for the values and returns the records to you.  This works better than any other method for very small tables.  It is slow on large tables.  Complexity is O(n) where n is the size of the table, for any number of records.\nSo a second approach might be an index scan.  Here PostgreSQL traverses a series of pages in a b-tree index to find the records.  Complexity is O(log(n)) to find each record.\nInternally PostgreSQL stores the rows in batches with fixed sizes, as pages.  It already solves this problem for you.  If you try to do the same, then you have batches of records inside batches of records, which is usually a recipe for bad things.","Q_Score":1,"Tags":"python,django,database,postgresql,saas","A_Id":38587539,"CreationDate":"2016-07-26T09:13:00.000","Title":"Storing entries in a very large database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have python 2.7.12 installed on my server. I'm using PuTTY to connect to my server. When running my python script I get the following. \n\nFile \"home\/myuser\/python\/lib\/python2.7\/site-packages\/peewee.py\", line 3657, in _connect\n      raise ImproperlyConfigured('pysqlite or sqlite3 must be installed.')\n  peewee.ImproperlyConfigured: pysqlite or sqlite3 must be installed.\n\nI thought sqlite was installed with python 2.7.12, so I'm assuming the issue is something else. Haven't managed to find any posts on here yet that have been helpful.\nI am missing something?\nThanks in advance","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":955,"Q_Id":38589963,"Users Score":0,"Answer":"Peewee will use either the standard library sqlite3 module or, if you did not compile Python with SQLite, Peewee will look for pysqlite2.\nThe problem is most definitely not with Peewee on this one, as Peewee requires a SQLite driver to use the SqliteDatabase class... If that driver does not exist, then you need to install it.","Q_Score":1,"Tags":"python,sqlite","A_Id":38715072,"CreationDate":"2016-07-26T12:30:00.000","Title":"Python - pysqlite or sqlite3 must be installed","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am attempting to run a python 2.7 program on HTCondor, however after submitting the job and using 'condor_q' to assess the job status, I see that the job is put in 'held'. \nAfter querying using 'condor_q -analyse jobNo.' the error message is \"Hold reason: Error from Ubuntu: Failed to execute '\/var\/lib\/condor\/execute\/dir_12033\/condor_exec.exe': (errno=8: 'Exec format error').\nI am unsure how to resolve this error, any help would be much appreciated. As I am relatively new to HTCondor and Ubuntu could any guidance be step wise and easy to follow\nI am running Ubuntu 16.04 and the latest release of HTCondor","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":197,"Q_Id":38593488,"Users Score":0,"Answer":"Update, managed to solve my problem. I needed to make sure that all directory paths were correct as I found that HTCondor was looking within its own files for the resources my submission program used. I therefore needed to define a variable in the .py file that contains the directory to the resource","Q_Score":0,"Tags":"python,ubuntu","A_Id":38618691,"CreationDate":"2016-07-26T15:03:00.000","Title":"Unable to submit python files to HTCondor- placed in 'held'","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":0},{"Question":"Is there any way in SQLAlchemy by reflection or any other means to get the name that a column has in the corresponding model? For example i have the person table with a column group_id. In my Person class this attribute is refered to as 'group' is there a way to dynamically and generically getting this without importing or call the Person class?","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":937,"Q_Id":38639948,"Users Score":0,"Answer":"Unfortunately it is most likely not possible...","Q_Score":0,"Tags":"python,sqlalchemy","A_Id":38652751,"CreationDate":"2016-07-28T14:55:00.000","Title":"SQLAlchemy get attribute name from table and column name","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a Flask webapp running on Pythonanywhere. I've recently been having a look at using Google Cloud's MYSQL service. It requires a list of IP addresses to be whitelisted for access.\nHow can I find this? I've tried 50.19.109.98 which is the IP address for Python Anywhere, but unless there is a secondary issue thats not it.\nThanks,\nBen","AnswerCount":1,"Available Count":1,"Score":0.3799489623,"is_accepted":false,"ViewCount":1260,"Q_Id":38686528,"Users Score":2,"Answer":"Your code running on PythonAnywhere could be on a whole bunch of IPs that could change at any time. You could try to add all the IPs, but that might not be the best\/most sustainable.","Q_Score":2,"Tags":"pythonanywhere","A_Id":38704698,"CreationDate":"2016-07-31T17:17:00.000","Title":"Pythonanywhere: getting the IP address for database access whitelist","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am creating a web project where I take in Form data and write to a SQL database.\nThe forms will be a questionnaire with logic branching. Due to the nature of the form, and the fact that this is an MVP project, I've opted to use an existing form service (e.g Google Forms\/Typeform). \nI was wondering if it's feasible to have form data submitted to multiple different tables (e.g CustomerInfo, FormDataA, FormDataB, etc.). While this might be possible with a custom form application, I do not think it's possible with Google Forms and\/or Typeform. \nDoes anyone have any suggestions on how to parse user submitted Form data into multiple tables when using Google Forms or Typeform?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":638,"Q_Id":38703892,"Users Score":0,"Answer":"You can add a script in the Google spreadsheet with an onsubmit trigger. Then you can do whatever you want with the submitted data.","Q_Score":0,"Tags":"python,sql,google-forms","A_Id":39074108,"CreationDate":"2016-08-01T16:37:00.000","Title":"Using Google Forms to write to multiple tables?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm trying to serialize results from a SQLAlchemy query. I'm new to the ORM so I'm not sure how to filter a result set after I've retrieved it. The result set looks like this, if I were to flatten the objects:\n\nA1  B1  V1\nA1  B1  V2\nA2  B2  V3\n\nI need to serialize these into a list of objects, 1 per unique value for A, each with a list of the V values. I.E.:\nObject1:\n\nA: A1\n\nB: B1\n\nV: {V1, V2}\n\n\nObject2:\n\nA: A2\n\nB: B2\n\nV: {V3}\n\n\nIs there a way to iterate through all unique values on a given column, but with the ability to return a list of values from the other columns?","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":591,"Q_Id":38708645,"Users Score":0,"Answer":"Turns out I needed to use association tables and the joinedload() function. The documentation is a bit wonky but I got there after playing with it for a while.","Q_Score":0,"Tags":"python,orm,sqlalchemy","A_Id":38882242,"CreationDate":"2016-08-01T21:46:00.000","Title":"How do I filter SQLAlchemy results based on a columns' value?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I wana draw some simple shapes in excel file like as \"arrow, line, rectangle, oval\" using XLSXWriter, but i can find any example to do it. Is it possible ? If not, what library of python can do that ?\nThanks!","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1339,"Q_Id":38738706,"Users Score":0,"Answer":"is it possible?\n\nUnfortunately not. Shapes aren't supported in XlsxWriter, apart from Textbox.","Q_Score":2,"Tags":"python,xlsxwriter","A_Id":38740317,"CreationDate":"2016-08-03T08:46:00.000","Title":"How to drawing shapes using XLSXWriter","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have two separate programs; one counts the daily view stats and another calculates earning based on the stats.\nCounter runs first and followed by Earning Calculator a few seconds later.\nEarning Calculator works by getting stats from counter table using date(created_at) > date(now()).\nThe problem I'm facing is that let's say at 23:59:59 Counter added 100 views stats and by the time the Earning Calculator ran it's already the next day.\nSince I'm using date(created_at) > date(now()), I will miss out the last 100 views added by the Counter.\nOne way to solve my problem is to summarise the previous daily report at 00:00:10 every day. But I do not like this.\nIs there any other ways to solve this issue?\nThanks.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":53,"Q_Id":38766962,"Users Score":0,"Answer":"You have to put a date on your data and instead of using now() use it.","Q_Score":0,"Tags":"python,mysql,analytics","A_Id":38770424,"CreationDate":"2016-08-04T12:10:00.000","Title":"How to solve mysql daily analytics that happens when date changes","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I want to develop a project that need a noSQL database. After searching a lot, I chose OrientDB. I want to make an API Rest that can connect to OrientDB. \nFirstly, I wanted to use Flask to develop but I don't know if it's better to use Java native driver between Python binary driver to connect with database.\nAnyone have results of performance between these drivers?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":127,"Q_Id":38795545,"Users Score":0,"Answer":"AFAIK on remote connection (with a standalone OrientDB server) performance would be the same. \nThe great advantage of using the Java native driver is the option to go embedded. If your deployment scenario allows it, you can avoid the standalone server and use OrientDB embedded into your Java application, avoiding network overhead.","Q_Score":0,"Tags":"java,python,performance,orientdb","A_Id":38802276,"CreationDate":"2016-08-05T18:15:00.000","Title":"Performance between Python and Java drivers with OrientDB","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I recently updated an entity model to include some extra properties, and noticed something odd. For properties that have never been written, the Datastore query page shows a \"\u2014\", but for ones that I've explicitly set to None in Python, it shows \"null\".\nIn SQL, both of those cases would be null. When I query an entity that has both types of unknown properties, they both read as None, which fits with that idea. \nSo why does the NDB datastore viewer differentiate between \"never written\" and \"set to None\", if I can't differentiate between them programatically?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":184,"Q_Id":38814666,"Users Score":4,"Answer":"You have to specifically set the value to NULL, otherwise it will not be stored in the Datastore and you see it as missing in the Datastore viewer.\nThis is an important distinction. NULL values can be indexed, so you can retrieve a list of entities where date of birth, for example, is null. On the other hand, if you do not set a date of birth when it is unknown, there is no way to retrieve a list of entities with date of birth property missing - you'll have to iterate over all entities to find them.\nAnother distinction is that NULL values take space in the Datastore, while missing values do not.","Q_Score":1,"Tags":"python,google-app-engine,null,google-cloud-datastore,app-engine-ndb","A_Id":38815611,"CreationDate":"2016-08-07T13:35:00.000","Title":"Why does the Google App Engine NDB datastore have both \"\u2014\" and \"null\" for unkown data?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"So I have this Python pyramid-based application, and my development workflow has basically just been to upload changed files directly to the production area.\nComing close to launch, and obviously that's not going to work anymore.\nI managed to edit the connection strings and development.ini and point the development instance to a secondary database.\nNow I just have to figure out how to create another copy of the project somewhere where I can work on things and then make the changes live.\nAt first, I thought that I could just make a copy of the project directory somewhere else and run it with different arguments pointing to the new location. That didn't work.\nThen, I basically set up an entirely new project called myproject-dev.  I went through the setup instructions:\nI used pcreate, and then setup.py develop, and then I copied over my development.ini from my project and carefully edited the various references to myproject-dev instead of myproject.\nThen,\ninitialize_myproject-dev_db \/var\/www\/projects\/myproject\/development.ini\nFinally, I get a nice pyramid welcome page that everything is working correctly.\nI thought at that point I could just blow out everything in the project directory and copy over the main project files, but then I got that feeling in the pit of my stomach when I noticed that a lot of things weren't working, like static URLs.\nApparently, I'm referencing myproject in includes and also static URLs, and who knows where else.\nI don't think this idea is going to work, so I've given up for now.\nCan anyone give me an idea of how people go about setting up a development instance for a Python pyramid project?","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":166,"Q_Id":38843404,"Users Score":1,"Answer":"Here's how I managed my last Pyramid app:\nI had both a development.ini and a production.ini. I actually had a development.local.ini in addition to the other two - one for local development, one for our \"test\" system, and one for production.  I used git for version control, and had a main branch for production deployments.  On my prod server I created the virtual environment, etc., then would pull my main branch and run using the production.ini config file.  Updates basically involved jumping back into the virtualenv and pulling latest updates from the repo, then restarting the pyramid server.","Q_Score":2,"Tags":"python,pyramid,pylons","A_Id":38886655,"CreationDate":"2016-08-09T06:17:00.000","Title":"Trying to make a development instance for a Python pyramid project","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I know it's possible to import Google BigQuery tables to R through bigrquery library. But is it possible to export tables\/data frames created in R to Google BigQuery as new tables? \nBasically, is there an R equivalent of Python's temptable.insert_data(df) or df.to_sql() ? \nthanks for your help,\nKasia","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":635,"Q_Id":38847743,"Users Score":1,"Answer":"It looks like bigrquery package does the job with insert_upload_job(). In the package documentation, it says this function \n> is only suitable for relatively small datasets\nbut it doesn't specify any size limits. For me, it's been working for tens of thousands of rows.","Q_Score":0,"Tags":"python,r,dataframe,google-bigquery","A_Id":39119230,"CreationDate":"2016-08-09T10:03:00.000","Title":"Exporting R data.frame\/tbl to Google BigQuery table","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am running a Flask app on an Apache 2.4 server. The app sends requests to an API built by a colleague using the Requests library. The requests are in a specific format and constructed by data stored in a MySQL database. The site is designed to show the feedback from the API on the index, and the user can edit the data stored in the MySQL database (and by extension, the data sent in the request) by another page, the editing page.\nSo let's say for example a custom field date is set to be \"2006\", I would access the index page, a request would be sent, the API does its magic and sends back data relevant to 2006. If I then went and changed the date to \"2007\" then the new field is saved in MySQL and upon navigating back to index the new request is constructed, sent off and data for 2007 should be returned.\nUnfortunately that's not happening.\nMy when I change details on my editing page they are definitely stored to the database, but when I navigate back to the index the request sends the previous set of data. I think that Apache is causing the problem because of two reasons:\n\nWhen I reset the server (service apache2 restart) the data sent back is the 'proper' data, even though I haven't touched the database. That is, the index is initially requesting 2006 data, I change it to request 2007 data, it still requests 2006 data, I restart the server, refresh the index and only then does it request 2007 data like it should have been doing since I edited it.\nWhen I run this on my local Flask development server, navigating to the index page after editing an entry immediately returns the right result - it feeds off the same database and is essentially identical to the deployed server except that it's not running on apache.\n\nIs there a way that Apache could be caching requests or something? I can't figure out why the server would keep sending old requests until I restart it.\nEDIT:\nThe requests themselves are large and ungainly and the responses would return data that I'm not comfortable with making available for examples for privacy reasons.\nI am almost certain that Apache is the issue because as previously stated, the Flask development server has no issues with returning the correct dataset. I have also written some requests to run through Postman, and these also return the data as requested, so the request structure must be fine. The only difference I can see between the local Flask app and the deployed one is Apache, and given that restarting the Apache server 'updates' the requests until the data is changed again, I think that it's quite clearly doing something untoward.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":83,"Q_Id":38854382,"Users Score":0,"Answer":"Dirn was completely right, it turned out not to be an Apache issue at all. It was SQL Alchemy all along.\nI imagine that SQL Alchemy knows not to do any 'caching' when it requests data on the development server but decides that it's a good idea in production, which makes perfect sense really. It was not using the committed data on every search, which  is why restarting the Apache server fixed it because it also reset the connection.\nI guess that's what dirn meant by \"How are you loading data in your application?\" I had assumed that since I turned off Flask's debugging on the development server it would behave just like it would in deployment but it looks like something has slipped through.","Q_Score":0,"Tags":"apache,flask,python-requests","A_Id":38869412,"CreationDate":"2016-08-09T15:06:00.000","Title":"Apache server seems to be caching requests","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Right now in Django, I have two databases: \n\nA default MySQL database for my app and\nan external Oracle database that, for my purposes, is read-only\n\nThere are far more tables in the external database than I need data from, and also I would like to modify the db layout slightly. Is there a way I can selectively choose what data in the external database I would like to sync to my database? The external database is dynamic, and I would like my app to reflect that. \nEx I would like to do something like this:\nSay the external database has two tables (out of 100) as follows:\nTable47\n\nEggs\nSpam\nSausage\n\nTable48\n\nName\nAge\nColor\n\nAnd I want to keep the data like:\nFoo\n\nEggs\nSpam\nType (a foreign key)\n\nBar\n\nName\nAge\nType (foreign key)\n\nType\n\nSome fields\n\nIs there a way I could do this in Django?","AnswerCount":1,"Available Count":1,"Score":-0.1973753202,"is_accepted":false,"ViewCount":218,"Q_Id":38858553,"Users Score":-1,"Answer":"Basically write models that match what you want your destination tables to be and then write something to migrate data between the two. I'd make this a comment if I could but not enough rep.","Q_Score":0,"Tags":"mysql,django,oracle,python-2.7","A_Id":38858633,"CreationDate":"2016-08-09T19:04:00.000","Title":"How do you selectively sync a database in Django?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am writing an application that uses historical time series data to perform simulations.\nIs it better for application to load the data from the database into local data wrapper classes before executing the main loop (up to 30 years day by day) or connect to the database each day to pull the required data?\nWhich is more elegant and efficient?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":15,"Q_Id":38870823,"Users Score":0,"Answer":"For current computers 30 years of day by day data amounts to almost nothing if your dayly data remains below say 10kB. Since your simulation may need efficient retrieval, especially if it combines data from different dates, I'd read all the data in memory in one query and then start processing.\nWhat is considered elegant is changing. Quite some years ago loading everything in to memory would have been considered a cardinal sin. Nowadays in-memory databases are common. Since databases in general offer set-level access (especially when queried by SQL, which you probably use) it would be quite inefficient to retrieve data item by item in a loop (although your database may be clever enough to cache things).","Q_Score":0,"Tags":"python,database,matlab,oop,time-series","A_Id":38870995,"CreationDate":"2016-08-10T10:28:00.000","Title":"Database to wrapper-classes or direct connectivity to database for time-series simulation application?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am using sqlite (development stage) database for my django project. I would like to store a dictionary field in a model. In this respect, i would like to use django-hstore field in my model. \nMy question is, can i use django-hstore dictionary field in my model even though i am using sqlite as my database? \nAs per my understanding django-hstore can be used along with PostgreSQL (Correct me if i am wrong). Any suggestion in the right direction is highly appreciated. Thank you.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":912,"Q_Id":38875927,"Users Score":3,"Answer":"hstore is specific to Postgres. It won't work on sqlite.\nIf you just want to store JSON, and don't need to search within it, then you can use one of the many third-party JSONField implementations.","Q_Score":2,"Tags":"python,django,postgresql,sqlite,django-models","A_Id":38875962,"CreationDate":"2016-08-10T14:15:00.000","Title":"Django hstore field in sqlite","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"What are some basic steps for troubleshooting and narrowing down the cause for the \"django.db.utils.ProgrammingError: permission denied for relation django_migrations\" error from Django?\nI'm getting this message after what was initially a stable production server but has since had some changes to several aspects of Django, Postgres, Apache, and a pull from Github. In addition, it has been some time since those changes were made and I don't recall or can't track every change that may be causing the problem.\nI get the message when I run python manage.py runserver or any other python manage.py ... command except python manage.py check, which states the system is good.","AnswerCount":4,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":32047,"Q_Id":38944551,"Users Score":4,"Answer":"If you receive this error and are using the Heroku hosting platform its quite possible that you are trying to write to a Hobby level database which has a limited number of rows.\nHeroku will allow you to pg:push the database even if you exceed the limits, but it will be read-only so any modifications to content won't be processed and will throw this error.","Q_Score":53,"Tags":"python,django,apache,postgresql,github","A_Id":62814973,"CreationDate":"2016-08-14T17:06:00.000","Title":"Steps to Troubleshoot \"django.db.utils.ProgrammingError: permission denied for relation django_migrations\"","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am working on a project that requires me to read a spreadsheet provided by the user and I need to build a system to check that the contents of the spreadsheet are valid. Specifically I want to validate that each column contains a specific datatype.\nI know that this could be done by iterating over every cell in the spreadsheet, but I was hoping there is a simpler way to do it.","AnswerCount":2,"Available Count":2,"Score":0.1973753202,"is_accepted":false,"ViewCount":109,"Q_Id":38961360,"Users Score":2,"Answer":"In openpyxl you'll have to go cell by cell.\nYou could use Excel's builtin Data Validation or Conditional Formatting, which openpyxl supports, for this. Let Excel do the work and talk to it using xlwings.","Q_Score":1,"Tags":"python,excel,openpyxl","A_Id":39077066,"CreationDate":"2016-08-15T19:05:00.000","Title":"Use openpyxl to verify the structure of a spreadsheet","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am working on a project that requires me to read a spreadsheet provided by the user and I need to build a system to check that the contents of the spreadsheet are valid. Specifically I want to validate that each column contains a specific datatype.\nI know that this could be done by iterating over every cell in the spreadsheet, but I was hoping there is a simpler way to do it.","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":109,"Q_Id":38961360,"Users Score":1,"Answer":"I ended up just manually looking at each cell. I have to read them all into my data structures before I can process anything anyways so it actually made sense to check then.","Q_Score":1,"Tags":"python,excel,openpyxl","A_Id":39088757,"CreationDate":"2016-08-15T19:05:00.000","Title":"Use openpyxl to verify the structure of a spreadsheet","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am facing a strange problem right now. I am using pypyodbc to insert data into a test database hosted by AWS. This database that I created was by hand and did not imitate all relations and whatnot between tables. All I did was create a table with the same columns and the same datatypes as the original (let's call it master) database. When I run my code and insert the data it works in the test environment. Then I change it over to the master database and the code runs all the way through but no data is actually inputted. Is there any chance that there are security protocols in place which prevent me from inputting data in through the Python script rather than through a normal SQL query? Is there something I am missing?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":54,"Q_Id":39027681,"Users Score":3,"Answer":"It sounds like it's not pointing to the correct database.  Have you made sure the connection information changes to point to the correct DB?  So the server name is correct, the login credentials are good, etc.?","Q_Score":0,"Tags":"python,sql-server,pypyodbc","A_Id":39027828,"CreationDate":"2016-08-18T21:18:00.000","Title":"Same code inserts data into one database but not into another","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a Django application where I use django-storages and amazon s3 to store images.\nI need to move those images to a different account: different user different bucket.\nI wanted to know how do I migrate those pictures?\nmy main concern is the links in my database to all those images, how do I update it?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":82,"Q_Id":39062605,"Users Score":0,"Answer":"The URL is relative to the amazon storage address you provide in your settings. so you only need to move the images to a new bucket and update your settings.","Q_Score":0,"Tags":"django,amazon-s3,python-django-storages","A_Id":39062626,"CreationDate":"2016-08-21T09:08:00.000","Title":"changing s3 storages with django-storages","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I need to store some daily information in DynamoDB. Basically, I need to store user actions: UserID, StoreID, ActionID and Timestamp.\nEach night I would like to process the information generated that day, do some aggregations, some reports, and then I can safely deleted those records.\nHow should I model this? I mean the hash key and the sort key... I need to have the full timestamp of each action for the reports but in order to query DynamoDB I guess it is easier to also save the date only.\nI have some PKs as UserID and StoreID but anyhow I need to process all data each night, not the data related to one user or one store...\nThanks!\nPatricio","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":29,"Q_Id":39111598,"Users Score":2,"Answer":"You can use RabbitMQ to schedule jobs asynchronously. This would be faster than multiple DB queries. Basically, this tool allows you to create a job queue (Containing UserID, StoreID & Timestamp) where workers can remove (at midnight if you want) and create your reports (or whatever your heart desires).\nThis also allows you to scale your system horizontally across nodes. Your workers can be different machines executing these tasks. You will also be safe if your DB crashes (though you may still have to design redundancy for a machine running RabbitMQ service).\nDB should be used for persistent storage and not as a queue for processing.","Q_Score":2,"Tags":"python,database-design,amazon-dynamodb","A_Id":39114304,"CreationDate":"2016-08-23T22:22:00.000","Title":"How to build model in DynamoDB if each night I need to process the daily records and then delete them?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"For my app, I am using Flask, however the question I am asking is more general and can be applied to any Python web framework.\nI am building a comparison website where I can update details about products in the database. I want to structure my app so that 99% of users who visit my website will never need to query the database, where information is instead retrieved from the cache (memcached or Redis).\nI require my app to be realtime, so any update I make to the database must be instantly available to any visitor to the site. Therefore I do not want to cache views\/routes\/html.\nI want to cache the entire database. However, because there are so many different variables when it comes to querying, I am not sure how to structure this. For example, if I were to cache every query and then later need to update a product in the database, I would basically need to flush the entire cache, which isn't ideal for a large web app.\nI would prefer is to cache individual rows within the database. The problem is, how do I structure this so I can flush the cache appropriately when an update is made to the database? Also, how can I map all of this together from the cache?\nI hope this makes sense.","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":488,"Q_Id":39128100,"Users Score":0,"Answer":"I had this exact question myself, with a PHP project, though. My solution was to use ElasticSearch as an intermediate cache between the application and database.\nThe trick to this is the ORM. I designed it so that when Entity.save() is called it is first stored in the database, then the complete object (with all references) is pushed to ElasticSearch and only then the transaction is committed and the flow is returned back to the caller.\nThis way I maintained full functionality of a relational database (atomic changes, transactions, constraints, triggers, etc.) and still have all entities cached with all their references (parent and child relations) together with the ability to invalidate individual cached objects.\nHope this helps.","Q_Score":2,"Tags":"python,database,caching,redis,memcached","A_Id":39128415,"CreationDate":"2016-08-24T16:03:00.000","Title":"How do I structure a database cache (memcached\/Redis) for a Python web app with many different variables for querying?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Background\nI studied and found that bigQuery doesn't accept schemas defined by online tools (which have different formats, even though meaning is same).\nSo, I found that if I want to load data (where no. of columns keeps varying and increasing dynamically) into a table which has a fixed schema.\nThoughts\nWhat i could do as a workaround is:\n\nFirst check if the data being loaded has extra fields.\nIf it has, a schema mismatch will occur, so first you create a temporary table in BQ and load this data into the table using \"autodetect\" parameter, which gives me a schema (that is in a format,which BQ accepts schema files).\nNow i can download this schema file and use it,to update my exsisting table in BQ and load it with appropriate data.\n\nSuggestion\nAny thoughts on this, if there is a better approach please share.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":353,"Q_Id":39141642,"Users Score":1,"Answer":"We are in the process of releasing a new feature that can update the schema of the destination table within a load\/query job. With autodetect and the new feature you can directly load the new data to the existing table, and the schema will be updated as part of the load job. Please stay tuned. The current ETA is 2 weeks.","Q_Score":0,"Tags":"python,google-analytics,google-bigquery,google-cloud-platform","A_Id":39172452,"CreationDate":"2016-08-25T09:34:00.000","Title":"schema free solution to BigQuery Load job","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am using Python with SQLite currently and wondering if it is safe to have multiple threads reading and writing to the database simultaneously. Does SQLite handle data coming in as a queue or have sort of mechanism that will stop the data from getting corrupt?","AnswerCount":2,"Available Count":2,"Score":0.2913126125,"is_accepted":false,"ViewCount":1006,"Q_Id":39158621,"Users Score":3,"Answer":"This is my issue too. SQLite using some kind of locking mechanism which prevent you doing concurrency operation on a DB. But here is a trick which i use when my db are small. You can select all your tables data into memory and operate on it and then update the original table.\nAs i said this is just a trick and it does not always solve the problem.\nI advise to create your trick.","Q_Score":2,"Tags":"python,multithreading,sqlite","A_Id":39163285,"CreationDate":"2016-08-26T05:05:00.000","Title":"Can you have multiple read\/writes to SQLite database simultaneously?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am using Python with SQLite currently and wondering if it is safe to have multiple threads reading and writing to the database simultaneously. Does SQLite handle data coming in as a queue or have sort of mechanism that will stop the data from getting corrupt?","AnswerCount":2,"Available Count":2,"Score":0.1973753202,"is_accepted":false,"ViewCount":1006,"Q_Id":39158621,"Users Score":2,"Answer":"SQLite has a number of robust locking mechanisms to ensure the data doesn't get corrupted, but the problem with that is if you have a number of threads reading and writing to it simultaneously you'll suffer pretty badly in terms of performance as they all trip over the others. It's not intended to be used this way, even if it does work.\nYou probably want to look at using a shared database server of some sort if this is your intended usage pattern. They have much better support for concurrent operations.","Q_Score":2,"Tags":"python,multithreading,sqlite","A_Id":39158655,"CreationDate":"2016-08-26T05:05:00.000","Title":"Can you have multiple read\/writes to SQLite database simultaneously?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I would like to create a script in Python for logging into MKS integrity and calling an already defined MKS query. Since I am a newby in programming, I was wondering if there is any script example for the task. That would be a great help for getting me started. \nThank you!","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1411,"Q_Id":39165180,"Users Score":0,"Answer":"I can't help you with python, but for MKS\nconnect to a host: IM connect --hostname=%host% --port=%port%\nrun query: im runquery --hostname=%host% --port=%port% %query_name%\nYou can see the help for each command if you just write IM command -?","Q_Score":0,"Tags":"python,mks-integrity","A_Id":41023731,"CreationDate":"2016-08-26T11:23:00.000","Title":"Python script for MKS integrity query","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have encountered a problem that I can not figure out.\nI'm working on an application written in Python and a Sybase ASE database using sybpydb to communicate with the datbase.\nNow I need to update a post where one of the columns in the where clause is of numeric(10) data type.\nWhen selecting the post Python treats the data as a float no problem there.\nBut when I try to update the post using the numeric value I just got from the select i get a \"Invalid data type\" error.\nMy first thought was to try to convert the float to an integer but it still gives the same error","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":152,"Q_Id":39168251,"Users Score":0,"Answer":"You need to capture the actual SQL query text which is sent to the ASE server before conclusions can be drawn.","Q_Score":0,"Tags":"python,sap-ase","A_Id":39202310,"CreationDate":"2016-08-26T14:06:00.000","Title":"Sybase numeric datatype and Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have this huge Excel (xls) file that I have to read data from. I tried using the xlrd library, but is pretty slow. I then found out that by converting the Excel file to CSV file manually and reading the CSV file is orders of magnitude faster.\nBut I cannot ask my client to save the xls as csv manually every time before importing the file. So I thought of converting the file on the fly, before reading it.\nHas anyone done any benchmarking as to which procedure is faster:\n\nOpen the Excel file with with the xlrd library and save it as CSV file, or\nOpen the Excel file with win32com library and save it as CSV file?\n\nI am asking because the slowest part is the opening of the file, so if I can get a performance boots from using win32com I would gladly try it.","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":582,"Q_Id":39179880,"Users Score":1,"Answer":"if you need to read the file frequently, I think it is better to save it as CSV. Otherwise, just read it on the fly. \nfor performance issue, I think win32com outperforms. however, considering cross-platform compatibility, I think xlrd is better.\nwin32com is more powerful. With it, one can handle Excel in all ways (e.g. reading\/writing cells or ranges). \nHowever, if you are seeking a quick file conversion, I think pandas.read_excel also works.\nI am using another package xlwings. so I am also interested with a comparison among these packages. \nto my opinion,\nI would use pandas.read_excel to for quick file conversion.\nIf demanding more processing on Excel, I would choose win32com.","Q_Score":1,"Tags":"python,excel,csv,win32com","A_Id":39360812,"CreationDate":"2016-08-27T10:07:00.000","Title":"XLRD vs Win32 COM performance comparison","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I want to execute script(probably written in python), when update query is executed on MySQL database. The query is going to be executed from external system written in PHP to which I don't have access, so I can't edit the source code. The MySQL server is installed on our machine. Any ideas how I can accomplish this, or is it even possible?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":54,"Q_Id":39243626,"Users Score":0,"Answer":"No, it is not possible to call external scripts from MySQL.\nThe only thing you can do is adding an ON UPDATE trigger that will write into some queue. Then you will have the python script POLLING the queue and doing whatever it's supposed to do with the rows it finds.","Q_Score":1,"Tags":"php,python,mysql,database","A_Id":39244221,"CreationDate":"2016-08-31T07:45:00.000","Title":"Executing script when SQL query is executed","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I run a number of queries for adhoc analysis against a postgres database. Many times I will leave the connection open through the day instead of ending after each query.\nI receive a postgres dump over scp through a shell script every five minutes and I would like to restore the database without cutting the connections. Is this possible?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":271,"Q_Id":39282825,"Users Score":1,"Answer":"One of the few activities that you cannot perform while a user is connected is dropping the database.\nSo \u2013 if that is what you are doing during restore \u2013 you'll have to change your approach. Don't drop the database (don't use the -C option in pg_dump or pg_restore), but rather drop and recreate the schemas and objects that don't depend on a schema (like large objects).\nYou can use the -c flag of pg_dump or pg_restore for that.\nThe other problem you might run into is connections with open transactions (state \u201cidle in transaction\u201d). Such connections can hold locks that keep you from dropping and recreating objects, and you'll have to use pg_terminate_backend() to get rid of them.","Q_Score":0,"Tags":"python,database,postgresql,restore","A_Id":39286433,"CreationDate":"2016-09-02T00:49:00.000","Title":"Restore postrgres without ending connections","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am trying to debug a Pootle (pootle is build on django) installation which fails with a django transaction error whenever I try to add a template to an existing language. Using the python debugger I can see that it fails when pootle tries to save a model as well as all the queries that have been made in that session.\nWhat I can't see is what specifically causes the save to fail. I figure pootle\/django must have added some database database constraint, how do I figure out which one? MySql (the database being used) apparently can't log just failed transactions.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":223,"Q_Id":39387983,"Users Score":1,"Answer":"Install django debug toolbar, you can easily check all of the queries that have been executed","Q_Score":0,"Tags":"python,mysql,django,pootle","A_Id":39447127,"CreationDate":"2016-09-08T10:01:00.000","Title":"How do I get Django to log why an sql transaction failed?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a web application that accesses large amounts of JSON data.\nI want to use a key value database for storing JSON data owned\/shared by different users of the web application (not users of the database). Each user should only be able to access the records they own or share.\nIn a relational database, I would add a column Owner to the record table, or manage shared ownerships in a separate table, and check access on the application side (Python). For key value stores, two approaches come to mind.\nUser ID as part of the key\nWhat if I use keys like USERID_RECORDID and then write code to check the USERID before accessing the record? Is that a good idea? It wouldn't work with records that are shared between users.\nUser ID as part of the value\nI could store one or more USERIDs in the value data and check if the data contains the ID of the user trying to access the record. Performance is probably slower than having the user ID as part of the key, but shared ownerships are possible.\nWhat are typical patterns to do what I am trying to do?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":171,"Q_Id":39423756,"Users Score":2,"Answer":"Both of the solutions you described have some limitations.\n\nYou point yourself that including the owner ID in the key does not solve the problem of shared data. However, this solution may be acceptable, if you add another key\/value pair, containing the IDs of the contents shared with this user (key: userId:shared, value: [id1, id2, id3...]).\nYour second proposal, in which you include the list of users who were granted access to a given content, is OK if and only if you application needs to make a query to retrieve the list of users who have access to a particular content. If your need is to list all contents a given user can access, this design will lead you to poor performances, as the K\/V store will have to scan all records -and this type of database engine usually don't allow you to create an index to optimise this kind of request.\n\nFrom a more general point of view, with NoSQL databases and especially Key\/Value stores, the model has to be defined according to the requests to be made by the application. It may lead you to duplicate some information. The application has the responsibility of maintaining the consistency of the data.\nBy example, if you need to get all contents for a given user, whether this user is the owner of the content or these contents were shared with him, I suggest you to create a key for the user, containing the list of content Ids for that user, as I already said. But if your app also needs to get the list of users allowed to access a given content, you should add their IDs in a field of this content. This would result in something like :\nkey: contentID, value: { ..., [userId1, userID2...]}\nWhen you remove the access to a given content for a user, your app (and not the datastore) have to remove the userId from the content value, and the contentId from the list of contents for this user.\nThis design may imply for your app to make multiple requests: by example one to get the list of userIDs allowed to access a given content, and one or more to get these user profiles. However, this should not really be a problem as K\/V stores usually have very high performances.","Q_Score":8,"Tags":"python,database,authorization,key-value,nosql","A_Id":39518000,"CreationDate":"2016-09-10T07:31:00.000","Title":"How do you control user access to records in a key-value database?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I used txt files to store data in it and read it any time i need and search in it and append and delete from it \nso \nwhy should i use database i can still using txt files ?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":55,"Q_Id":39437667,"Users Score":0,"Answer":"In fact, you have used files instead of a database. To answer the question, let us check the advantages of using a database:\n\nit is faster: a service is awaiting commands and your app sends some commands to it. Database Management Systems have a lot of cool stuff implemented which you will be lacking if you use a single file. True, you can create a service which loads the file into memory and serves commands, but while that seems to be easy, it will be inferior to RDBMS's, since your implementation is highly unlikely to be even close to a match of the optimizations done for RDBMS's over decades, unless you implement an RDBMS, but then you end up with an RDBMS, after all\nit is safer: RDBMS's encrypt data and have user-password authentication along with port handling\nit is smaller: data is stored in a compressed manner, so if you end up with a lot of data, data size will get critical much later\nit is developed: you will always have possibilities to upgrade your system with juices implemented recently and to keep up the pace with science's current development\nyou can use ORM's and other stuff built to ease the pain of data handling\nit supports concurrent access: imagine the case when many people are reaching your database at the same time. Instead of you implementing very complicated stuff, you can get this feature instantly\n\nAll in all, you will either use a database management system (not necessarily relational), implement your own or work with textual files. Your textual file will quickly be overwhelmed if your application is successful and you will need a database management system. If you write your own, you might have a success story to tell, but it will come only after many years of hard work. So, if you get successful, then you will need database management system. If you do not get successful, you can use textual files, but the question is: is it worth it?\nAnd finally, your textual file is a database, but you are managing it by your custom and probably very primitive (no offence, but it is virtually impossible to achieve results when you are racing against the whole world) database management system compared to the ones out there. So, yes, you should learn to use advanced database management systems and should refactor your project to use one.","Q_Score":1,"Tags":"python,sql","A_Id":39438159,"CreationDate":"2016-09-11T15:26:00.000","Title":"using Python and SQL","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm trying to run a server in python\/django and I'm getting the following error:\n\ndjango.db.uils.OperationslError: (200, \"Can't connect to local MySQL\n  server through socket '\/tmp\/mysql.sock' (2)\").\n\nI have MySQL-python installed (1.2.5 version) and mysql installed (0.0.1), both via pip, so I'm not sure why I can't connect to the MySQL server. Does anyone know why? Thanks!","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":295,"Q_Id":39474896,"Users Score":1,"Answer":"You can't install mysql through pip; it's a database, not a Python library (and it's currently in version 5.7). You need to install the binary package for your operating system.","Q_Score":0,"Tags":"python,mysql,django","A_Id":39475119,"CreationDate":"2016-09-13T16:29:00.000","Title":"OperationalError: Can't connect to local MySQL server through socket","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I wrote a python application that uses cx_Oracle and then generates a pyinstaller bundle (folder\/single executable).  I should note it is on 64 bit linux.  I have a custom spec file that includes the Oracle client libraries so everything that is needed is in the bundle.  \nWhen I run the bundled executable on a freshly installed CentOS 7.1 VM, (no Oracle software installed), the program connects to the database successfully and runs without error.  However, when I install the bundled executable on another system that contains RHEL 7.2, and I try to run it, I get\n\nUnable to acquire Oracle environment handle. \n\nMy understanding is this is due to an Oracle client installation that has some sort of conflict.  I tried unsetting ORACLE_HOME on the machine giving me errors.  It's almost as though the program is looking for the Oracle client libraries in a location other than in the location where I bundled the client files.  \nIt seems like it should work on both machines or neither machine.  I guess I'm not clear on how the Python application\/cx_Oracle finds the Oracle client libraries.  Again, it seems to have found them fine on a machine with a fresh operating system installation.  Any ideas on why this is happening?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":306,"Q_Id":39482504,"Users Score":1,"Answer":"One thing that you may be running into is the fact that if you used the instant client RPMs when you built cx_Oracle an RPATH would have been burned into the shared library. You can examine its contents and change it using the chrpath command. You can use the special path $ORIGIN in the modified RPATH to specify a path relative to the shared library.\nIf an RPATH isn't the culprit, then you'll want to examine the output from the ldd command and see where it is looking and then adjust things to make it behave itself!","Q_Score":0,"Tags":"python,pyinstaller,cx-oracle","A_Id":39503038,"CreationDate":"2016-09-14T04:30:00.000","Title":"Why does pyinstaller generated cx_oracle application work on fresh CentOS machine but not on one with Oracle client installed?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am working with RapidMiner at the moment and am trying to copy my RapidMiner results which are in xlsx files to txt files in order to do some further processing with python. I do have plain text in column A (A1-A1500) as well as the according filename in column C (C1-C1500). \nNow my question: \nIs there any possibility (I am thinking of the xlrd module) to read the content of every cell in column A and print this to a new created txt file with the filename being given in corresponding column C? \nAs I have never worked with the xlrd module before I am a bit lost at the moment...","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":5449,"Q_Id":39512166,"Users Score":0,"Answer":"Good day!  So, I'm not sure I understand your question correctly, but have you tried a combination of Read Excel operator with the Loop Examples operator?  Your loop subprocess could then use Write CSV operator or similar.","Q_Score":1,"Tags":"python-3.x,xlrd,rapidminer","A_Id":39519713,"CreationDate":"2016-09-15T13:22:00.000","Title":"Read Excel Cells and Copy content to txt file","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a MongoDB that houses data from a web scrape that runs weekly via Scrapy. I'm going to setup a cron job to run the scrape job weekly. What I would like to do is also export a CSV out of MongoDB using mongoexport however I would like to inject the current date into the file name. I've tried a few different methods without much success. Any help would be greatly appreciated! For reference, my current export string is: mongoexport --host localhost --db glimpsedb --collection scrapedata --csv --out scrape-export.csv --fields dealerid,unitid,seller,street,city,state,zipcode,rvclass,year,make,model,condition,price\nSo, ideally the file name would be scrape-export-current date.csv\nThanks again!","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":244,"Q_Id":39580809,"Users Score":1,"Answer":"Replace --out scrape-export.csv in your command with --out scrape-export-$(date +\"%Y-%m-%d\").csv\nIt'll create filenames in the format scrape-export-2016-09-05","Q_Score":0,"Tags":"python,mongodb,scrapy,mongoexport","A_Id":39580966,"CreationDate":"2016-09-19T19:38:00.000","Title":"Export MongoDB to CSV Using File Name Variable","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I installed python3.5 on my mac, its installation was automatically. but these days i found there was already python2 on my mac and every module i installed through pip went to \/Library\/Python\/2.7\/site-packages.\nI find python3 installed location is \/Library\/Frameworks\/Python.framework\/Versions\/3.5\nNow download a mysql-connector-python and installed it, install location is python2.7\/site-packages, when i open pycharm whose default interceptor is python3.5, hence i can not use mysql-connector, so is there any body who know this question?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":851,"Q_Id":39585238,"Users Score":0,"Answer":"for mysql-connector installation problem, i found the solution:\nTry go to python3 bin directory and find pip method. this pip method can be override by the system python2 pip command, so if you want to install MySQL-python module to python3.x site-packages, you should cd to such bin directory and .\/pip install MySQL-python, it can download such module successfully but installed error:ImportError:No module named 'ConfigParser', I google such error and find there is no such module in python3 and we can get its fork version:mysqlclient.\nNOTE: In order not to be conflict with system default python2 pip command, cd and go to python3 bin directory and .\/pip install mysqlclient and succeed.","Q_Score":0,"Tags":"python,macos","A_Id":39585904,"CreationDate":"2016-09-20T03:25:00.000","Title":"mac two version python conflict","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a column-family\/table in cassandra-3.0.6 which has a column named \"value\" which is defined as a blob data type.\nCQLSH query select * from table limit 2; returns me:\n\nid   | name  | value\nid_001 | john  | 0x010000000000000000\nid_002 | terry | 0x044097a80000000000\n\nIf I read this value using cqlengine(Datastax Python Driver), I get the output something like:\n\n{'id':'id_001', 'name':'john', 'value': '\\x01\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00'}\n{'id':'id_002', 'name':'terry', 'value': '\\x04@\\x97\\xa8\\x00\\x00\\x00\\x00\\x00'}\n\nIdeally the values in the \"value\" field are 0 and 1514 for row1 and row2 resp.\nHowever, I am not sure how I can convert the \"value\" field values extracted using cqlengine to 0 and 1514. I tried few methods like ord(), decode(), etc but nothing worked. :(\nQuestions:\n\nWhat is this format?\n'\\x01\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00' or\n'\\x04@\\x97\\xa8\\x00\\x00\\x00\\x00\\x00'?\nHow I can convert these arbitrary values to 0 and 1514?\n\nNOTE: I am using python 2.7.9 on Linux\nAny help or pointers would be useful.\nThanks,","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1608,"Q_Id":39611995,"Users Score":0,"Answer":"Blob will be converted to a byte array in Python if you read it directly. That looks like a byte array containing the Hex value of the blob.\nOne way is to explicitly do the conversion in your query.\nselect id, name, blobasint(value) from table limit 3\nThere should be a conversion method with the Python driver as well.","Q_Score":0,"Tags":"python,cassandra,cqlsh,cqlengine","A_Id":39628303,"CreationDate":"2016-09-21T09:02:00.000","Title":"Not able to convert cassandra blob\/bytes string to integer","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":0},{"Question":"In BigQuery it's possible to write to a new table the results of a query. I'd like the table to be created only whenever the query returns at least one row. Basically I don't want to end up creating empty table. I can't find an option to do that. (I am using the Python library, but I suppose the same applies to the raw API)","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":788,"Q_Id":39616849,"Users Score":1,"Answer":"There's no option to do this in one step. I'd recommend running the query, inspecting the results, and then performing a table copy with WRITE_TRUNCATE to commit the results to the final location if the intermediate output contains at least one row.","Q_Score":0,"Tags":"python,google-bigquery","A_Id":39632118,"CreationDate":"2016-09-21T12:41:00.000","Title":"Write from a query to table in BigQuery only if query is not empty","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm attempting to transfer all data over to Neo4j, and am wondering if it would be alright to name all properties on nodes the same as in Postgres exactly. E.g id will be id, name will be name, and so on. Are there any conflicts with doing something like this?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":68,"Q_Id":39713636,"Users Score":0,"Answer":"No, especially if you use the one of the clients to do the migration as they will automatically escape anything that needs to be escaped, but there's nothing I've come across.","Q_Score":0,"Tags":"python,neo4j,neo4jclient,neo4jrestclient","A_Id":39718452,"CreationDate":"2016-09-26T22:59:00.000","Title":"Neo4j Transferring All Data from Postgres","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have been trying to schedule a report in SAP BO CMC. This report was initially written in Python and built into a .exe file. This .exe application runs to save the report into an .xlsx file in a local folder. \nI want to utilize the convenient scheduling functions in SAP BO CMC to send the report in Emails. I tried and created a \"Local Program\" in CMC and linked it to the .exe file, but you can easily imagine the problem I am faced with -- the application puts the file in the folder as usual but CMC won't be able to grab the Excel file generated. \nIs there a way to re-write the Python program a bit so that the output is not a file in some folder, but an object that CMC can get as an attachment to the Emails? \nI have been scheduling Crystal reports in CMC and this happens naturally. The Crystal output can be sent as an attachment to the Email. Wonder if the similar could happen for a .exe , and how? \nKindly share your thoughts. Thank you very much!\nP.S. Don't think it possible to re-write the report in Crystal though, as the data needs to be manipulated based on inputs from different data sources. That's where Python comes in to help. And I hope I don't need to write the program as to cover the Emailing stuff and schedule it in windows' scheduled tasks. Last option... This would be too inconvenient to maintain. We don't get access to the server easily.","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":744,"Q_Id":39726495,"Users Score":1,"Answer":"It's kind of hack-ish, but it can be done.  Have the program (exe) write out the bytes of the Excel file to standard output.  Then configure the program object for email destination, and set the filename to a specific name (ex. \"whatever.xlsx\").\nWhen emailing a program object, the attached file will contain the standard output\/error of the program.  Generally this will just be text but it works for binary output as well.\nAs this is a hack, if the program generates any other text (such as error message) to standard out, it will be included in the .xlsx file, which will make the file invalid.  I'd suggest managing program errors such that they get logged to a file and NOT to standard out\/error.\nI've tested this with a Java program object; but an exe should work just as well.","Q_Score":0,"Tags":"python,excel,email,sap,business-objects","A_Id":39727668,"CreationDate":"2016-09-27T13:50:00.000","Title":"How can I out put an Excel file as Email attachment in SAP CMC?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am using Flask, Flask-SqlAlchemy and Flask-Migrate to manage my models. And I just realize that in my latest database state, when I create a new migration file, python manage.py db migrate -m'test migration, it will not create an empty migration file. Instead it tries to create and drop several unique key and foreign key constraints.\nAny ideas why it behaves like this?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1587,"Q_Id":39744688,"Users Score":4,"Answer":"If you have made no changes to your model from the current migration, but you get a non-empty migration file generated, then it suggests for some reason your models became out of sync with the database, and the contents of this new migration are just the things that are mismatched.\nIf you say that the migration contains code that drops some constraints and add some other ones, it makes me think that the constraint names have probable changed, or maybe you upgraded your SQLAlchemy version to a newer version that generates constraints with different names.","Q_Score":1,"Tags":"python,flask-sqlalchemy,flask-migrate","A_Id":39761658,"CreationDate":"2016-09-28T10:20:00.000","Title":"Why Flask Migrate doesn't create an empty migration file?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm trying to add a text box to a chart I've generated with openpyxl, but can't find documentation or examples showing how to do so. Does openpyxl support it?","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":3047,"Q_Id":39773544,"Users Score":0,"Answer":"I'm not sure what you mean by \"text box\". In theory you can add pretty much anything covered by the DrawingML specification to a chart but the practice may be slightly different.\nHowever, there is definitely no built-in API for this so you'd have to start by creating a sample file and working backwards from it.","Q_Score":2,"Tags":"python,openpyxl","A_Id":39774351,"CreationDate":"2016-09-29T14:49:00.000","Title":"Adding a text box to an excel chart using openpyxl","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have installed PostgreSQL Server 9.6.0 and Python 3.4.2 on Windows 2012 R2 Server.\nI copied plpython3.dll to C:\/Program Files\/PostgreSQL\/9.6\/lib\/\nThe in PostgreSQL I try running this command: CREATE EXTENSION plpython3u;\nAnd I receive this message: \nERROR:  could not load library \"C:\/Program Files\/PostgreSQL\/9.6\/lib\/plpython3.dll\": The specified module could not be found.\nUnder this folder: C:\\Program Files\\PostgreSQL\\9.6\\share\\extension there are plpython3u files.\nHow can I get PostgreSQL to recognize this Python 3 extension?\nThanks!","AnswerCount":5,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":5532,"Q_Id":39800075,"Users Score":0,"Answer":"plpython3.dll in the official package is built against python 3.3, not python 3.4. What it expect is python33.dll in system32 folder. You need to install python 3.3 for your system. \nSince py33 has been phased out, you may soon get frustrated, due to lack of pre-built binary package, lxml, pyzmq etc all needs to be built from source. If you need any binary module, make sure you have a correctly set up compiler.","Q_Score":3,"Tags":"python,postgresql","A_Id":41320600,"CreationDate":"2016-09-30T21:04:00.000","Title":"Error during: CREATE EXTENSION plpython3u; on PostgreSQL 9.6.0","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have installed PostgreSQL Server 9.6.0 and Python 3.4.2 on Windows 2012 R2 Server.\nI copied plpython3.dll to C:\/Program Files\/PostgreSQL\/9.6\/lib\/\nThe in PostgreSQL I try running this command: CREATE EXTENSION plpython3u;\nAnd I receive this message: \nERROR:  could not load library \"C:\/Program Files\/PostgreSQL\/9.6\/lib\/plpython3.dll\": The specified module could not be found.\nUnder this folder: C:\\Program Files\\PostgreSQL\\9.6\\share\\extension there are plpython3u files.\nHow can I get PostgreSQL to recognize this Python 3 extension?\nThanks!","AnswerCount":5,"Available Count":3,"Score":0.0399786803,"is_accepted":false,"ViewCount":5532,"Q_Id":39800075,"Users Score":1,"Answer":"Exactly the same situation I faced with Postgres 9.6 Windows 10.\nPL\/Python3U would not get through.\nWorked around it:\nInstalled Python34 64bit Windows 10 version.\nCopied Python34.dll to c:\\windows\\system32 as Python33.dll and it worked.","Q_Score":3,"Tags":"python,postgresql","A_Id":54007128,"CreationDate":"2016-09-30T21:04:00.000","Title":"Error during: CREATE EXTENSION plpython3u; on PostgreSQL 9.6.0","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have installed PostgreSQL Server 9.6.0 and Python 3.4.2 on Windows 2012 R2 Server.\nI copied plpython3.dll to C:\/Program Files\/PostgreSQL\/9.6\/lib\/\nThe in PostgreSQL I try running this command: CREATE EXTENSION plpython3u;\nAnd I receive this message: \nERROR:  could not load library \"C:\/Program Files\/PostgreSQL\/9.6\/lib\/plpython3.dll\": The specified module could not be found.\nUnder this folder: C:\\Program Files\\PostgreSQL\\9.6\\share\\extension there are plpython3u files.\nHow can I get PostgreSQL to recognize this Python 3 extension?\nThanks!","AnswerCount":5,"Available Count":3,"Score":1.0,"is_accepted":false,"ViewCount":5532,"Q_Id":39800075,"Users Score":6,"Answer":"Copy the python34.dll file to c:\\windows\\system32 and name the copy python33.dll\nThe create language plpython3u should then work without a problem.","Q_Score":3,"Tags":"python,postgresql","A_Id":46281240,"CreationDate":"2016-09-30T21:04:00.000","Title":"Error during: CREATE EXTENSION plpython3u; on PostgreSQL 9.6.0","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have created a rather large CSV file (63000 rows and around 40 columns) and I want to join it with an ESRI Shapefile.\nI have used ArcPy but the whole process takes 30! minutes. If I make the join with the original (small) CSV file, join it with the Shapefile and then make my calculations with ArcPy and continously add new fields and calculate the stuff it takes 20 minutes. I am looking for a faster solution and found there are other Python modules such as PySHP or DBFPy but I have not found any way for joining tables, hoping that could go faster.\nMy goal is already to get away from ArcPy as much as I can and preferable only use Python, so preferably no PostgreSQL and alikes either.\nDoes anybody have a solution for that? Thanks a lot!","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":377,"Q_Id":39868163,"Users Score":0,"Answer":"Not exactly a programmatical solution for my problem but a practical one:\nMy shapefile is always static, only the attributes of the features will change. So I copy my original shapefile (only the basic files with endings .shp, .shx, .prj) to my output folder and rename it to the name I want. \nThen I create my CSV-File with all calculations and convert it to DBF and save it with the name of my new shapefile to the output folder too. ArcGIS will now load the shapefile along with my own DBF file and I don't even need to do any tablejoin at all!\nNow my program runs through in only 50 seconds!\nI am still interested in more solutions for the table join problem, maybe I will encounter that problem again in the future where the shapefile is NOT always static. I did not really understand Nan's solution, I am still at \"advanced beginner\" level in Python :)\nCheers","Q_Score":2,"Tags":"python-2.7,dbf,arcpy,pyshp","A_Id":39892009,"CreationDate":"2016-10-05T07:45:00.000","Title":"DBF Table Join without using Arcpy?","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have been developing a Django project using sqlite3 as the backend and it has been working well. I am now attempting to switch the project over to use postgres as the backend but running into some issues.\nAfter modifying my settings file, setting up postgres, creating the database and user I get the error below when running manage.py migrate\ndjango.db.utils.ProgrammingError: relation \"financemgr_rate\" does not exist\nfinancemgr is an app within the project. rate is a table within the app.\nIf I run this same command but specify sqlite3 as my backend it works fine.\nFor clarity I will repeat:\nEnvironment Config1\n\nUbuntu 14.04, Django 1.10\nSettings file has 'ENGINE': 'django.db.backends.sqlite3'\n\nRun manage.py migrate\nMigration runs and processes all the migrations successfully\n\n\nEnvironment Config2\n\nUbuntu 14.04, Django 1.10\nSettings file has 'ENGINE': 'django.db.backends.postgresql_psycopg2'\n\nRun manage.py migrate\nMigration runs and gives the error django.db.utils.ProgrammingError: relation \"financemgr_rate\" does not exist\n\n\nEverything else is identical. I am not trying to migrate data, just populate the schema etc.\nAny ideas?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":955,"Q_Id":39879939,"Users Score":2,"Answer":"This may help you :\nI think you have pre-stored migration files(migrate for sqlite database).\nNow you have change the database configuration but still django looking for the existing table according to migration files you have(migrated for previous database). \nBetter you delete all the migration files in migration folder of your app, and migrate it again, by running commands python manage.py makemigrations and python manage.py migrate it may work fine.","Q_Score":2,"Tags":"python,django,postgresql,django-models,sqlite","A_Id":40100350,"CreationDate":"2016-10-05T17:06:00.000","Title":"django migrate failing after switching from sqlite3 to postgres","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"im using django-tables2 in order to show values from a database query. And everythings works fine. Im now using Django-dabug-toolbar and was looking through my pages with it. More out of curiosity than performance needs. When a lokked at the page with the table i saw that the debug toolbar registerd over 300 queries for a table with a little over 300 entries. I dont think flooding the DB with so many queries is a good idea even if there is no performance impact (at least not now). All the data should be coming from only one query.\nWhy is this happening and how can i reduce the number of queries?","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":348,"Q_Id":39882504,"Users Score":2,"Answer":"Im posting this as a future reference for myself and other who might have the same problem. \nAfter searching for a bit I found out that django-tables2 was sending a single query for each row. The query was something like SELECT * FROM \"table\"  LIMIT 1 OFFSET 1 with increasing offset. \nI reduced the number of sql calls by calling query = list(query) before i create the table and pass the query. By evaluating the query in the python view code the table now seems to work with the evaulated data instead and there is only one database call instead of hundreds.","Q_Score":3,"Tags":"python,django,django-tables2","A_Id":39882505,"CreationDate":"2016-10-05T19:49:00.000","Title":"django-tables2 flooding database with queries","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"This is quite a general question, though I\u2019ll give the specific use case for context.\nI'm using a FileMaker Pro database to record personal bird observations. For each bird on the national list, I have extracted quite a lot of base data by website scraping in Python, for example conservation status, geographical range, scientific name and so on. In day-to-day use of the database, this base data remains fixed and unchanging. However, once a year or so I will want to re-scrape the base data to pick up the most recent published information on status, range, and even changes in scientific name (that happens).\nI know there are options such as PyFilemaker or bBox which should allow me to write to the FileMaker database from Python, so the update mechanism itself shouldn't be a problem.\nIt would be rather dangerous simply to overwrite all of last year\u2019s base data with the newly scraped data, and I'm looking for general advice as to how best to provide visibility for the changes before manually importing them.  What I have in mind is to use pandas to generate a spreadsheet using the base data, and to highlight the changed cells.  Does that sound a sensible way of doing it?  I suspect that this may be a very standard requirement, and if anybody could help out with comments on an approach which is straightforward to implement in Python that would be most helpful.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":46,"Q_Id":39936352,"Users Score":1,"Answer":"This is not a standard requirement and there is no easy way of doing this. The best way to track changes is a Source Control system like git, but it is not applicable to FileMaker Pro as the files are binary.\nYou can try your approach, or you can try to add the new records in FileMaker instead of updating them and flag them as current or use only the last record\nThere are some amazing guys here, but you might want to take it to one of the FileMAker forums as the FIleMAker audience there is much larger then in SO","Q_Score":0,"Tags":"python,filemaker","A_Id":39941551,"CreationDate":"2016-10-08T19:12:00.000","Title":"Providing visibility of periodic changes to a database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a function like the following that I want to use to compute the hash of a sqlite database file, in order to compare it to the last backup I made to detect any changes.\n\ndef get_hash(file_path):\n    # http:\/\/stackoverflow.com\/a\/3431838\/1391717\n    hash_sha1 = hashlib.sha1\n    with open(file_path, \"rb\") as f:\n        for chunk in iter(lambda: f.read(4096), b\"\"):\n            hash_sha1.update(chunk)\n\n    return hash_sha1.hexdigest()\n\nI plan on locking the database, so no one can write to it while I'm computing the hash. Is it possible for me to cause any harm while doing this?\n\n\/\/ http:\/\/codereview.stackexchange.com\/questions\/78643\/create-sqlite-backups\nconnection = sqlite3.connect(database_file)\ncursor = connection.cursor()\ncursor.execute(\"begin immediate\")\n\ndb_hash = get_hash(args.database)","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1538,"Q_Id":39936697,"Users Score":1,"Answer":"The sqlite3 database files, can and may be read by many different readers at the same time. There is no problem with concurrency in that respect with sqlite3. The problems which is native to sqlite3 concerns writing to the file, only one writer is allowed. \nSo if you only read your fine. \nIf you are planning to lock the database and succeed with that, while you compute the hash, you become a writer with exclusive access.","Q_Score":0,"Tags":"python,sqlite","A_Id":39938696,"CreationDate":"2016-10-08T19:49:00.000","Title":"How to compute a hash of a sqlite database file without causing harm","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I want to use a test db on my test environment, and the production db on production environment in my Python application.\nHow should I handle routing to two dbs? Should I have an untracked config.yml file that has the test db's connection string on my test server, and the production db's connection string on production server?\nI'm using github for version control and travis ci for deployment.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":68,"Q_Id":39950769,"Users Score":0,"Answer":"Let's take Linux environment for example. Often, the user level configuration of an application is placed under your home folder as a dot file. So what you can do is like this:\n\nIn your git repository, track a sample configure file, e.g., config.sample.yaml, and put the configuration structure here.\nWhen deploying, either in test environment or production environment, you can copy and rename this file as a dot-file, e.g., $HOME\/.{app}.config.yaml. Then in your application, you can read this file.\n\nIf you are developing an python package, you can make the file copy operation done in the setup.py. There are some advantages:\n\nYou can always track the structure changes of your configuration file.\nSeparate configuration between test and production enviroment.\nMore secure, you do not need to code your import db connection information in the public file.\n\nHope this would be helpful.","Q_Score":0,"Tags":"python,github,configuration,travis-ci,configuration-files","A_Id":39951058,"CreationDate":"2016-10-10T03:06:00.000","Title":"Using different dbs on production and test environment","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"1) I have Spark on Bluemix platform, how do I add a library there ?\nI can see the preloaded libraries but cant add a library that I want.\nAny command line argument that will install a library?\n\npip install --package is not working there\n\n2)  I have Spark and Mongo DB running, but I am not able to connect both of them.\n\ncon ='mongodb:\/\/admin:ITCW....ssl=true'\n  ssl1 =\"LS0tLS .....\"\n  client = MongoClient(con,ssl=True)\n  db = client.mongo11 \n  collection = db.mongo11 \n  ff=db.sammy.find() \n\n Error I am getting is : \nSSL handshake failed: [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed (_ssl.c:590)","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":106,"Q_Id":40020767,"Users Score":2,"Answer":"In a Python notebook:\n!pip install <package>\nand then\nimport <package>","Q_Score":0,"Tags":"python,apache-spark,ibm-cloud,ibm-cloud-plugin","A_Id":40021035,"CreationDate":"2016-10-13T12:17:00.000","Title":"Add a library in Spark in Bluemix & connect MongoDB , Spark together","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"In New API(Python-Odo o) I Successfully upload Excel File.\nBut if second time i upload same file Data are Duplicated.\nSo How I upload only Unique Data.\nIf No Change in Excel file no changes in recored\nBut if Change in Data \nthis only recored updated reaming recored same as upload.\nThanks","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":58,"Q_Id":40068892,"Users Score":0,"Answer":"Hello viral,\nWhen you upload first time data in excel that time take one unique column(i.e ID)\nand when you second time upload data that time check the unique column, if found so only update their data else upload data as new record.","Q_Score":1,"Tags":"python,openerp,odoo-8","A_Id":44375335,"CreationDate":"2016-10-16T09:40:00.000","Title":"Unique Data Uplload in Python Excel","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"In New API(Python-Odo o) I Successfully upload Excel File.\nBut if second time i upload same file Data are Duplicated.\nSo How I upload only Unique Data.\nIf No Change in Excel file no changes in recored\nBut if Change in Data \nthis only recored updated reaming recored same as upload.\nThanks","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":58,"Q_Id":40068892,"Users Score":0,"Answer":"For that you need atleast one field to identify the record to check the duplicacy.","Q_Score":1,"Tags":"python,openerp,odoo-8","A_Id":40134328,"CreationDate":"2016-10-16T09:40:00.000","Title":"Unique Data Uplload in Python Excel","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"As part of a bigger set of tests I need to extract all the formulas within an uploaded Excel workbook.  I then need to parse each formula into its respective range references and dump those references into a simple database.  For example, if Cell A1 has a formula =B1 + C1 then my database would record B1 and C1 as referenced cells.\nCurrently I read formulas one at a time using openpyxl and then parse them.  This is fine for smaller workbooks, but for large workbooks it can be very slow.  It feels entirely inefficient.\nCould pandas or a similar module extract Excel formulas faster?  Or is there perhaps a better way to extract all workbook formulas than reading it one cell at a time?\nAny advice would be highly appreciated.","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":994,"Q_Id":40117180,"Users Score":2,"Answer":"What do you mean by \"extracting the formulae faster\"? They are stored with each cell so you have to go cell by cell. When it comes to parsing, openpyxl includes a tokeniser which you might find useful. In theory this would allow you to read the worksheet XML files directly and only parse the nodes with formulae in them. However, you'd also have to handle the \"shared formulae\" that some applications use. openpyxl automatically converts such formulae into per-cell ones.\nInternally Pandas relies on xlrd to read the files, so the ETL of getting the stuff into Pandas won't be faster than working directly with worksheet objects.","Q_Score":2,"Tags":"excel,python-3.x,pandas,openpyxl","A_Id":40126930,"CreationDate":"2016-10-18T20:07:00.000","Title":"Fastest way to parse all Excel formulas using Python 3.5","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"As part of a bigger set of tests I need to extract all the formulas within an uploaded Excel workbook.  I then need to parse each formula into its respective range references and dump those references into a simple database.  For example, if Cell A1 has a formula =B1 + C1 then my database would record B1 and C1 as referenced cells.\nCurrently I read formulas one at a time using openpyxl and then parse them.  This is fine for smaller workbooks, but for large workbooks it can be very slow.  It feels entirely inefficient.\nCould pandas or a similar module extract Excel formulas faster?  Or is there perhaps a better way to extract all workbook formulas than reading it one cell at a time?\nAny advice would be highly appreciated.","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":994,"Q_Id":40117180,"Users Score":0,"Answer":"Don't know about python, but a fast approach to the problem is:\n\nget all the formulas in R1C1 mode into an array using specialcells\nfeed into a collection\/dictionary to get uniques\nthen parse the uniques","Q_Score":2,"Tags":"excel,python-3.x,pandas,openpyxl","A_Id":40118989,"CreationDate":"2016-10-18T20:07:00.000","Title":"Fastest way to parse all Excel formulas using Python 3.5","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am storing all the static files in AWS S3 Bucket and I am using Docker containers to run my application. This way, whenever I want to deploy the changes, I create a new container using a new image. \nI am running .\/manage.py collectstatic on every deployment because sometimes I add libraries to the project that have static files; and it takes forever to reupload them to S3 on every deployment. Is there a way I can keep a list of static files uploaded to S3 in my database, so that collectstatic only uploads to the added files.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":228,"Q_Id":40184760,"Users Score":0,"Answer":"Clean solution would be to read the source for collectstatic and write your own management command that would do the same thing, but would write a file list into the database. A quick and dirty way would be to pipe the output of collectstatic into a script of some sort that would reformat it as SQL and pipe it through a database client.","Q_Score":0,"Tags":"python,django,amazon-web-services,amazon-s3,django-staticfiles","A_Id":40185281,"CreationDate":"2016-10-21T20:13:00.000","Title":"How can I make django to write static files list to database when using collectstatic","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"How do I exit dbshell (SQLite\u00a03) on the command line when using Django?\nIt's my first time to use the command. I watch a book and am practicing Django at the same time. After I run this command, I have no idea how to leave the environment since I have never learned SQL before.","AnswerCount":5,"Available Count":3,"Score":0.0399786803,"is_accepted":false,"ViewCount":5764,"Q_Id":40205197,"Users Score":1,"Answer":"Just typing quit does the work.","Q_Score":3,"Tags":"python,django,sqlite","A_Id":40205233,"CreationDate":"2016-10-23T16:36:00.000","Title":"How do I exit dbshell (SQLite 3) on the command line when using Django?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"How do I exit dbshell (SQLite\u00a03) on the command line when using Django?\nIt's my first time to use the command. I watch a book and am practicing Django at the same time. After I run this command, I have no idea how to leave the environment since I have never learned SQL before.","AnswerCount":5,"Available Count":3,"Score":0.0399786803,"is_accepted":false,"ViewCount":5764,"Q_Id":40205197,"Users Score":1,"Answer":"You can just hit the key combination Ctrl + C.","Q_Score":3,"Tags":"python,django,sqlite","A_Id":47724071,"CreationDate":"2016-10-23T16:36:00.000","Title":"How do I exit dbshell (SQLite 3) on the command line when using Django?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"How do I exit dbshell (SQLite\u00a03) on the command line when using Django?\nIt's my first time to use the command. I watch a book and am practicing Django at the same time. After I run this command, I have no idea how to leave the environment since I have never learned SQL before.","AnswerCount":5,"Available Count":3,"Score":0.1194272985,"is_accepted":false,"ViewCount":5764,"Q_Id":40205197,"Users Score":3,"Answer":"You can type .exit in thew shell to exit. For more information about commands, type .help.\nIt raises an error and exits ... it was helpful :)","Q_Score":3,"Tags":"python,django,sqlite","A_Id":51351884,"CreationDate":"2016-10-23T16:36:00.000","Title":"How do I exit dbshell (SQLite 3) on the command line when using Django?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm trying to figure out how to convert the entire column of a spreadsheet from an int to a string. The problem I'm having is that I have a bunch of excell spreadsheets whose values I want to upload to our database. Our numbers are 10 digits long and being converted to scientific notation though, so I want to convert all of our numbers from ints into strings before our upload.\nI've been trying to do some research, but I can't find any libraries that would convert an entire column -- do I need to iterate row by row converting the numbers to strings? \nThank you.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":2713,"Q_Id":40266970,"Users Score":0,"Answer":"You could try:\n    df['column_name'] = df['column_name'].astype(str)","Q_Score":0,"Tags":"python,excel","A_Id":57348868,"CreationDate":"2016-10-26T15:58:00.000","Title":"Converting Excel Column Type From Int to String in Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am using python for reading Unicode data and then Preprocessing it and storing it in a database (Postgres) \nNow the database has 3 tables with 4 attributes and 700,000 tuples each. I read the data and map it to python dictionary and list according to the way I need to use it. \nNow I have to iterate through all these tuples, do some calculations and write again in the database. \nI have to do 1000 iteration like these. The problem is 1 iteration takes about 50 minutes which makes it impossible to make those many iterations. \nIs there anyway I can make these iterations faster?\nAny new idea is welcome. Not necessary in python.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":334,"Q_Id":40282987,"Users Score":0,"Answer":"You don't say what updates each \"iteration\" performs, but clearly you are reading and writing 7 million rows. Would it be possible to use the database to perform the updates?","Q_Score":0,"Tags":"python-3.x,postgresql-9.1","A_Id":40284042,"CreationDate":"2016-10-27T11:03:00.000","Title":"Data Preprocessing with python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a database with time series data split up into even sized chunks stored as arrays in postgres. \nI need to arbitrarily extract ranges of them and concatenate the returned set into a single array. They have an offset field so given a start offset and length you can find any part of the set you are looking for.\nWhich is better: \n\nTo write queries that return each individual array and concatenate in software\n\nor \n\nUse a stored procedure that takes a start point and length and does the concatenation internally before returning the entire array","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":25,"Q_Id":40316891,"Users Score":0,"Answer":"\u201cBetter\u201d is a rather unspecific adjective in this case.\nIf you are asking for aesthetic judgement, simplicity of code and mantainability, I don't feel in a position to pronounce a clear judgement. My gut feeling is that both are similar.\nIf you are asking about good performance, I'd advise you to run a simple test. But even without a test I'd say that both solutions are not optimal and you should write it as a single SQL statement.\nIf you are asking about portability, the answer depends on whether it is more important to port to another database (that would favor the application software solution) or to port to a different programming language (in that case, the solution in the database is preferable).","Q_Score":0,"Tags":"arrays,postgresql,python-3.x","A_Id":40320130,"CreationDate":"2016-10-29T07:07:00.000","Title":"stored procedure versus queries for array concatanation","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm designing a trade management system. I want to be able to enter in values into excel and have python do some computation (rather than excel). Is this even possible?\nWith openpyxl I have to enter in the value to excel, save, close, run the script, reopen excel. This is an unacceptable in terms of the design criteria. \nCan any one recommend a better way to have a live interface which updates when values are changed in the cells ? Ideally I would like to remain with excel","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1126,"Q_Id":40381804,"Users Score":0,"Answer":"I don't know if that is even possible, but it will be at least difficult to do. Because Excel locks the sheet file when it is read, it cannot be modified by other processes while it is opened. \nSo that leave only the possibility to have the Excel process modify the file. And scripting in Excel can only be done in VB as far as I know (but I don't know much about that).","Q_Score":1,"Tags":"python,excel","A_Id":40381980,"CreationDate":"2016-11-02T13:58:00.000","Title":"How to update an Excel worksheet live without closing and reopening python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Is there any difference between cursor in cx_oracle api which is used in python and cursor of plsql in database?\nIf there is a difference please elaborate on it.\nI am using python 3.5 and oracle 11g database and eclipse ide to use api and connect.\nThanks in advance,","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":95,"Q_Id":40406598,"Users Score":0,"Answer":"They both reference the same underlying concepts and methods. What you can do in the one you should be able to do in the other. There are limitations, of course, but these are due to the differences in the languages being used in each case. If you have a specific question, please update your question accordingly!","Q_Score":0,"Tags":"oracle11g,cursor,python-3.5,cx-oracle","A_Id":40425912,"CreationDate":"2016-11-03T16:23:00.000","Title":"Difference between cx_oracle.cursor in python and cursor in database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have web application which dynamically deployed on EC2 instances (scalable). Also I have RDS mysql instance which dynamically created by python with boto3. Now port 3306 of RDS is public, but I want to allow connection only from my EC2's from specific VPC. Can I create RDS on specific VPC (same one with EC2 instances)? What is best practice to create such set EC2 + RDS ?","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":214,"Q_Id":40426863,"Users Score":1,"Answer":"It is certainly best practice to have your Amazon EC2 instances in the same VPC as the Amazon RDS database. Recommended security is:\n\nCreate a Security Group for your web application EC2 instances (Web-SG)\nLaunch your Amazon RDS instance in a private subnet in the same VPC\nConfigure the Security Group on the RDS instance to allow incoming MySQL (3306) traffic from the Web-SG security group\n\nIf your RDS instance is currently in a different VPC, you can take a snapshot and then create a new database from the snapshot.\nIf you are using an Elastic Load Balancer, you could even put your Amazon EC2 instances in a private subnet since all access will be via the Load Balancer.","Q_Score":0,"Tags":"python,amazon-web-services,deployment,amazon-ec2,boto3","A_Id":40433014,"CreationDate":"2016-11-04T15:50:00.000","Title":"Create AWS RDS on specific VPC","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":1,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I was using Zodb for large data storage which was in form of typical dictionary format (key,value). \nBut while storing in ZODB i got following warning message:\n\nC:\\python-3.5.2.amd64\\lib\\site-packages\\ZODB\\Connection. py:550:\n  UserWarning: The  object\n  you're saving is large. (510241658 bytes.)\nPerhaps you're storing media which should be stored in blobs.\nPerhaps you're using a non-scalable data structure, such as a\n  PersistentMapping or PersistentList.\nPerhaps you're storing data in objects that aren't persistent at all.\n  In cases like that, the data is stored in the record of the containing\n  persistent object.\nIn any case, storing records this big is probably a bad idea.\nIf you insist and want to get rid of this warning, use the\n  large_record_size option of the ZODB.DB constructor (or the\n  large-record-size option in a configuration file) to specify a larger\n  size.\nwarnings.warn(large_object_message % (obj.class, len(p)))\n\nplease suggest how can i store large data in ZODB or suggest any other library for this purpose","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":901,"Q_Id":40548608,"Users Score":1,"Answer":"You must store the object on the filesystem and add reference to it in the zodb like using a regular database.","Q_Score":2,"Tags":"python,database,dataset,zodb,object-oriented-database","A_Id":40549472,"CreationDate":"2016-11-11T13:01:00.000","Title":"ZODB or other database for large data storage in python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am using sql to pull in values from 'lookup' table. I will use\ncursor and fetchall and then loop through values and place them into\ndictionary. I do not see reason to keep querying database(open conn,\nquery, close conn) for every lookup performed when a dictionary of\nsubset of data should suffice. Is this 'standard' practice to use dictionary in-lieu of table ? \nIs there  a way to test this with different sets of values without connecting to database? I would prefer at least unit testing without connecting to data store. Some framework or some pattern? Not sure what to investigate.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":56,"Q_Id":40550998,"Users Score":0,"Answer":"I do a lot of this. And although it sounds like a cop out, the answer is \"it depends\":\nIf the dataset is very large I would keep referring back to the database as loading it in to memory could be a resource issue.\nIf the dataset is not to large then loading it in to a memory and referring to it can really improve performance.\nI tend to test and see what the performance is like.","Q_Score":1,"Tags":"python,sql,testing","A_Id":40551282,"CreationDate":"2016-11-11T15:21:00.000","Title":"Python Testing without sql connection","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm developing some project in Django, something to manage assets in warehouses. I want to use two databases to this. First is sqlite database, which contains any data about users. Second is mongoDB database,in which  want to store all the data related to assets. The question is, how to tell to my model classes, which database they should use (models responsible for user registration etc - sqlite, models responsible for managing assets data - mongoDB)? I read about DATABASE_ROUTERS and using Meta classes, but it's solutions for supported databases by Django (or maybe I don't know something), I dont know if it's good and possible to integrate it with mongoengine. \nThanks for any tip!","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1468,"Q_Id":40602640,"Users Score":0,"Answer":"I found a solution, It's very simple. If you want your model to use mongoDB database, just create model class witch Document parameter (or EmbeddedDocument, for example class Magazine(Document):). but if you prefer default database type defined, just create class, like in django documentation (example class Person(models.Model):).","Q_Score":0,"Tags":"python,django,mongodb,sqlite,mongoengine","A_Id":40752618,"CreationDate":"2016-11-15T05:28:00.000","Title":"Managing databases in Django models, sqlite and mongoengine","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm working on a project that I inherited, and I want to add a table to my database that is very similar to one that already exists. Basically, we have a table to log users for our website, and I want to create a second table to specifically log users that our site fails to do a task for.\nSince I didn't write the site myself, and am pretty new to both SQL and Django, I'm a little paranoid about running a migration (we have a lot of really sensitive data that I'm paranoid about wiping).\nInstead of having a django migration create the table itself, can I create the second table in MySQL, and the corresponding model in Django, and then have this model \"recognize\" the SQL table? without explicitly using a migration?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":38,"Q_Id":40616036,"Users Score":0,"Answer":"SHORT ANSWER: Yes. \nMEDIUM ANSWER: Yes.  But you will have to figure out how Django would have created the table, and do it by hand.  That's not terribly hard.\nDjango may also spit out some warnings on startup about migrations being needed...but those are warnings, and if the app works, then you're OK.\nLONG ANSWER:  Yes.  But for the sake of your sanity and sleep quality, get a completely separate development environment and test your backups.  (But you knew that already.)","Q_Score":0,"Tags":"python,mysql,django","A_Id":40616612,"CreationDate":"2016-11-15T17:24:00.000","Title":"Do I Need to Migrate to Link my Database to Django","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am interesting in building databases and have been reading about SQL engines and Pandas framework, and how they interact, but am still confused about the difference between a database and a data framework.\nI wonder if somebody could point me to links which clarify the distinction between them, and which is the best starting point for a data analysis project.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":66,"Q_Id":40658287,"Users Score":1,"Answer":"Database is place where you store data collection. You can manipulate data by DML statement and some statements can be more difficult (like pivots or functions). Data framework is tool to make your computations, pivots and other manipulating much more easier (for example with drag and drop option).","Q_Score":0,"Tags":"python,sql,database,pandas","A_Id":40658564,"CreationDate":"2016-11-17T15:05:00.000","Title":"Database and Data Framework","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I built a simple statement to run a load data local infile on a MySQL table. I'm using Python to generate the string and also run the query. So I'm using the Python package pymysql.\nThis is the line to build the string. Assume metadata_filename is a proper string:\n\nload_data_statement = \"\"\"load data local infile \"\"\" + metadata_filename + \"\"\"INTO TABLE table1 FIELDS TERMINATED BY ',' ENCLOSED BY '\\'';\"\"\"\n\nI originally had string substitution, and wanted to see if that was the issue, but it isn't. If I edit the statement above and commend out the ENCLOSED BY part, it is able to run, but not properly load data since I need the enclosed character\nIf I print(load_data_statement), I get what appears to be proper SQL code, but it doesn't seem to be read by the SQL connector. This is what's printed: \n\nload data local infile 'filename.txt' INTO TABLE table1 FIELDS TERMINATED BY ',' ENCLOSED BY ''';\n\nThat all appears to be correct, but the Mysql engine is not taking it. What should I edit in Python to escape the single quote or just write it properly?\nEdit:\nI've been running the string substitution alternative, but still getting issues: load_data_statement = \"\"\"load data local infile 'tgt_metadata_%s.txt' INTO TABLE table1 FIELDS TERMINATED BY ',' ENCLOSED BY '\\'';\"\"\" % metadata_filename\nAlso tried raw strings:load_data_statement = r\"\"\"load data local infile 'tgt_metadata_%s.txt' INTO TABLE table1 FIELDS TERMINATED BY ',' ENCLOSED BY '\\'';\"\"\" % metadata_filename\nAlso tried raw strings:load_data_statement = r\"\"\"load data local infile 'tgt_metadata_%s.txt' INTO TABLE table1 FIELDS TERMINATED BY ',' ENCLOSED BY '\\'';\"\"\" % metadata_filename\nAnd tried adding extra escapes: Also tried raw strings:load_data_statement = r\"\"\"load data local infile 'tgt_metadata_%s.txt' INTO TABLE table1 FIELDS TERMINATED BY ',' ENCLOSED BY '\\\\'';\"\"\" % metadata_filename\nAlso tried raw strings:load_data_statement = r\"\"\"load data local infile \\'tgt_metadata_%s.txt\\' INTO TABLE table1 FIELDS TERMINATED BY ',' ENCLOSED BY '\\'';\"\"\" % metadata_filename\nThe execute line is simple `cur.execute(load_data_statement)\nAnd the error I'm getting is odd: `pymysql.err.ProgrammingError: (1064, \"You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'tgt_metadta_mal.txt'.txt' INTO table tgt_metadata FIELDS TERMINATED BY ','; ENC' at line 1\")\nI don't understand why the message starts at 'tgt_metadata_mal.txt and shows only the first 3 letters of ENCLOSED BY...","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":4539,"Q_Id":40672551,"Users Score":0,"Answer":"I think the problem is with the SQL statement you print. The single quote in ''' should be escaped: '\\''. Your backslash escapes the quote at Python level, and not the MySQL level. Thus the Python string should end with ENCLOSED BY '\\\\'';\nYou may also use the raw string literal notation:\nr\"\"\"INTO TABLE table1 FIELDS TERMINATED BY ',' ENCLOSED BY '\\'';\"\"\"","Q_Score":1,"Tags":"python,mysql,escaping,load-data-infile,pymysql","A_Id":40672954,"CreationDate":"2016-11-18T08:36:00.000","Title":"In Python how do I escape a single quote within a string that will be used as a SQL statement?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I built a simple statement to run a load data local infile on a MySQL table. I'm using Python to generate the string and also run the query. So I'm using the Python package pymysql.\nThis is the line to build the string. Assume metadata_filename is a proper string:\n\nload_data_statement = \"\"\"load data local infile \"\"\" + metadata_filename + \"\"\"INTO TABLE table1 FIELDS TERMINATED BY ',' ENCLOSED BY '\\'';\"\"\"\n\nI originally had string substitution, and wanted to see if that was the issue, but it isn't. If I edit the statement above and commend out the ENCLOSED BY part, it is able to run, but not properly load data since I need the enclosed character\nIf I print(load_data_statement), I get what appears to be proper SQL code, but it doesn't seem to be read by the SQL connector. This is what's printed: \n\nload data local infile 'filename.txt' INTO TABLE table1 FIELDS TERMINATED BY ',' ENCLOSED BY ''';\n\nThat all appears to be correct, but the Mysql engine is not taking it. What should I edit in Python to escape the single quote or just write it properly?\nEdit:\nI've been running the string substitution alternative, but still getting issues: load_data_statement = \"\"\"load data local infile 'tgt_metadata_%s.txt' INTO TABLE table1 FIELDS TERMINATED BY ',' ENCLOSED BY '\\'';\"\"\" % metadata_filename\nAlso tried raw strings:load_data_statement = r\"\"\"load data local infile 'tgt_metadata_%s.txt' INTO TABLE table1 FIELDS TERMINATED BY ',' ENCLOSED BY '\\'';\"\"\" % metadata_filename\nAlso tried raw strings:load_data_statement = r\"\"\"load data local infile 'tgt_metadata_%s.txt' INTO TABLE table1 FIELDS TERMINATED BY ',' ENCLOSED BY '\\'';\"\"\" % metadata_filename\nAnd tried adding extra escapes: Also tried raw strings:load_data_statement = r\"\"\"load data local infile 'tgt_metadata_%s.txt' INTO TABLE table1 FIELDS TERMINATED BY ',' ENCLOSED BY '\\\\'';\"\"\" % metadata_filename\nAlso tried raw strings:load_data_statement = r\"\"\"load data local infile \\'tgt_metadata_%s.txt\\' INTO TABLE table1 FIELDS TERMINATED BY ',' ENCLOSED BY '\\'';\"\"\" % metadata_filename\nThe execute line is simple `cur.execute(load_data_statement)\nAnd the error I'm getting is odd: `pymysql.err.ProgrammingError: (1064, \"You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'tgt_metadta_mal.txt'.txt' INTO table tgt_metadata FIELDS TERMINATED BY ','; ENC' at line 1\")\nI don't understand why the message starts at 'tgt_metadata_mal.txt and shows only the first 3 letters of ENCLOSED BY...","AnswerCount":2,"Available Count":2,"Score":0.2913126125,"is_accepted":false,"ViewCount":4539,"Q_Id":40672551,"Users Score":3,"Answer":"No need for escaping that string.\ncursor.execute(\"SELECT * FROM Codes WHERE ShortCode = %s\", text) \nYou should use %s instead of your strings and then (in this case text) would be your string. This is the most secure way of protecting from SQL Injection","Q_Score":1,"Tags":"python,mysql,escaping,load-data-infile,pymysql","A_Id":40672606,"CreationDate":"2016-11-18T08:36:00.000","Title":"In Python how do I escape a single quote within a string that will be used as a SQL statement?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am building a social network where each user has 3 different profiles - Profile 1, Profile 2 and Profile 3.\nThis is my use case:\nUser A follows Users B, C and D in Profile 1. User A follows Users C, F and G in Profile 2. User C follows Users A and E in profile 3.\nAnother question is that any user on each of these profiles would need to see the latest or (say top N) posts of the users they are following on their respective profiles (whether it is profile 1, 2 or 3).\nHow can we best store the above information?\nContext: \nI am c using Django framework and a Postgres DB to store user\u2019s profile information. User\u2019s posts are being stored on and retrieved from a Cloud CDN.\nWhich is the best way to go implementing these use cases i.e. the choice of technologies to best suit this scenario? Scalability is an other important factor that comes into play here.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":169,"Q_Id":40813514,"Users Score":0,"Answer":"Neo4J is a graph database, which is good for multiple-hops relation search. Say, you want to get the top N posts of A's brother's friend's sister... AFAIK, it's a standalone instance, you CANNOT partition your data on several nodes. Otherwise, the relation between two person might cross machines.\nRedis is a key-value store, which is good for searching by key. Say you want to get the friend list of A, or get the top N list of A. You can have a Redis cluster to distribute your data on several machines.\nWhich is better? It depends on your scenario. It seems that you don't need multiple-hops relation search. So Redis might be better.\nYou can have a SET to save the friend list of each person. and have a LIST to save the post ids of each person. When you need show posts for user A, call SMEMBERS or SSCAN to get the friend list, and then call LRANGE for each friend to get the top N post ids.","Q_Score":0,"Tags":"python,django,postgresql,neo4j,redis","A_Id":40814518,"CreationDate":"2016-11-25T23:41:00.000","Title":"Should I use Redis or Neo4J for the following use case?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a Python program that I am running as a Job on a Kubernetes cluster every 2 hours. I also have a webserver that starts the job whenever user clicks a button on a page.\nI need to ensure that at most only one instance of the Job is running on the cluster at any given time.\nGiven that I am using Kubernetes to run the job and connecting to Postgresql from within the job, the solution should somehow leverage these two. I though a bit about it and came with the following ideas:\n\nFind a setting in Kubernetes that would set this limit, attempts to start second instance would then fail. I was unable to find this setting.\nCreate a shared lock, or mutex. Disadvantage is that if job crashes, I may not unlock before quitting.\n\n\nKubernetes is running etcd, maybe I can use that\nCreate a 'lock' table in Postgresql, when new instance connects, it checks if it is the only one running. Use transactions somehow so that one wins and proceeds, while others quit. I have not yet thought this out, but is should work.\n\nQuery kubernetes API for a label I use on the job, see if there are some instances. This may not be atomic, so more than one instance may slip through.\n\nWhat are the usual solutions to this problem given the platform choice I made? What should I do, so that I don't reinvent the wheel and have something reliable?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1116,"Q_Id":40958107,"Users Score":1,"Answer":"A completely different approach would be to run a (web) server that executes the job functionality. At a high level, the idea is that the webserver can contact this new job server to execute functionality. In addition, this new job server will have an internal cron to trigger the same functionality every 2 hours.\nThere could be 2 approaches to implementing this:\n\nYou can put the checking mechanism inside the jobserver code to ensure that even if 2 API calls happen simultaneously to the job server, only one executes, while the other waits. You could use the language platform's locking features to achieve this, or use a message queue.\nYou can put the checking mechanism outside the jobserver code (in the database) to ensure that only one API call executes. Similar to what you suggested. If you use a postgres transaction, you don't have to worry about your job crashing and the value of the lock remaining set.\n\nThe pros\/cons of both approaches are straightforward. The major difference in my mind between 1 & 2, is that if you update the job server code, then you might have a situation where 2 job servers might be running at the same time. This would destroy the isolation property you want. Hence, database might work better, or be more idiomatic in the k8s sense (all servers are stateless so all the k8s goodies work; put any shared state in a database that can handle concurrency).\nAddressing your ideas, here are my thoughts:\n\nFind a setting in k8s that will limit this: k8s will not start things with the same name (in the metadata of the spec). But anything else goes for a job, and k8s will start another job.\na) etcd3 supports distributed locking primitives. However, I've never used this and I don't really know what to watch out for.\nb) postgres lock value should work. Even in case of a job crash, you don't have to worry about the value of the lock remaining set.\nQuerying k8s API server for things that should be atomic is not a good idea like you said. I've used a system that reacts to k8s events (like an annotation change on an object spec), but I've had bugs where my 'operator' suddenly stops getting k8s events and needs to be restarted, or again, if I want to push an update to the event-handler server, then there might be 2 event handlers that exist at the same time.\n\nI would recommend sticking with what you are best familiar with. In my case that would be implementing a job-server like k8s deployment that runs as a server and listens to events\/API calls.","Q_Score":0,"Tags":"python,postgresql,mutex,kubernetes,distributed-system","A_Id":40968608,"CreationDate":"2016-12-04T11:28:00.000","Title":"Ensuring at most a single instance of job executing on Kubernetes and writing into Postgresql","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":0},{"Question":"I currently have a Python program which reads a local file (containing a pickled database object) and saves to that file when it's done. I'd like to branch out and use this program on multiple computers accessing the same database, but I don't want to worry about synchronizing the local database files with each other, so I've been considering cloud storage options. Does anyone know how I might store a single data file in the cloud and interact with it using Python? \nI've considered something like Google Cloud Platform and similar services, but those seem to be more server-oriented whereas I just need to access a single file on my own machines.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":57,"Q_Id":41031326,"Users Score":0,"Answer":"You could install gsutil and the boto library and use that.","Q_Score":0,"Tags":"python,database,file,cloud,storage","A_Id":41031479,"CreationDate":"2016-12-08T03:33:00.000","Title":"Access a Cloud-stored File using Python 3?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"i have written MicroServices like for auth, location, etc.\nAll of microservices have different database, with for eg location is there in all my databases for these services.When in any of my project i need a location of user, it first looks in cache, if not found it hits the database. So far so good.Now when location is changed in any of my different databases, i need to update it in other databases as well as update my cache.\ncurrently i made a model (called subscription) with url as its field, whenever a location is changed in any database, an object is created of this subscription. A periodic task is running which checks for subscription model, when it finds such objects it hits api of other services and updates location and updates the cache.\nI am wondering if there is any better way to do this?","AnswerCount":1,"Available Count":1,"Score":0.3799489623,"is_accepted":false,"ViewCount":426,"Q_Id":41043800,"Users Score":2,"Answer":"I am wondering if there is any better way to do this?\n\n\"better\" is entirely subjective. if it meets your needs, it's fine.\nsomething to consider, though: don't store the same information in more than one place.\nif you need an address, look it up from the service that provides address, every time.\nthis may be a performance hit, but it eliminates the problem of replicating the data everywhere.\nanother option would be a more proactive approach, as suggested in comments.\ninstead of creating a task list for changes, and doing that periodically, send a message across rabbitmq immediately when the change happens. let every service that needs to know, get a copy of the message and update it's own cache of info.\njust remember, though. every time you have more than one copy of the information, you reduce the \"correctness\" of the system, as a whole. it will always be possible for the information found in one of your apps to be out of date, because it did not get an update from the official source.","Q_Score":3,"Tags":"python,django,rabbitmq,celery","A_Id":41049986,"CreationDate":"2016-12-08T16:06:00.000","Title":"microservices and multiple databases","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I want to show some SQL queries inside a notebook. I neither need nor want them to run. I'd just like them to be well formatted. At the very least I want them to be indented properly with new lines, though keyword highlighting would be nice too. Does a solution for this exist already?","AnswerCount":3,"Available Count":1,"Score":0.0665680765,"is_accepted":false,"ViewCount":10031,"Q_Id":41046955,"Users Score":1,"Answer":"I found that this fixed the issue I was having.\n``` sql \nProduced styled code in edit mode but not when the cell was run.\n``` mysql\nProduced correct styling","Q_Score":16,"Tags":"sql,ipython-notebook,jupyter-notebook,code-formatting","A_Id":48311365,"CreationDate":"2016-12-08T19:03:00.000","Title":"Formatting SQL Query Inside an IPython\/Jupyter Notebook","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I normally am able to run long queries using pyscopg2+sql magic in a Notebook, but lately my Notebooks seems to lose their connection and stall. When I look at my redshift logs, I can see that the queries completed successfully, but my Notebook never gets any data back and just keeps waiting.\nWhat might be going on?","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":206,"Q_Id":41051422,"Users Score":0,"Answer":"Adding this connection options to my connection string seems to have fixed my problem: keepalives=1&keepalives_idle=60","Q_Score":1,"Tags":"ipython-notebook,amazon-redshift,psycopg2,jupyter-notebook","A_Id":41090841,"CreationDate":"2016-12-09T00:54:00.000","Title":"iPython Notebook Unresponsive Over Long SQL Queries","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a huge log file ~4 GB. I have to parse a log file line by line, for each line I should query database, and also connect to another csv files and join data from different sources. \nExecution time is near 2 days. However unfortunately for any reasons like lost connection to MySQL server during query, i've lost all the parsing so far and i have to run the script again and again. Then, During last one week I have executed this script several time and i've lost all the previous parsing. the script had to write the final result into csv file. I am looking for a solution to avoid of this problem, what can I do? \nIs there any way to keep the last status of the process somewhere in order I re-execute from the last point of process rather that running from the beginning each time? or any other solution that can avoid of this interruption.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":43,"Q_Id":41056503,"Users Score":0,"Answer":"To solve above problem regarding to above discussion I have queried once db, I keep it as dictionary and then each time I get key in dictionary. It speeds up the time execution, more over lost connection is not going to affect anymore the processing. I would like to mention that Time execution is reduced to 20 min. It's incredible!! Thanks to dictionary ..","Q_Score":0,"Tags":"python,connection","A_Id":41058203,"CreationDate":"2016-12-09T08:52:00.000","Title":"Python db lost connection middle of processing and parsing a huge log file","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I've tried everything recommended & still can't get openpyxl to work in Python 3. I've tried both the pip3 and \"sudo apt-get install python3-openpyxl\" installation methods & they seem to work fine, but when I open the python3 interpreter & type \"import openpyxl\", I still get the \n\nImportError: No module named 'openpyxl'.\n\nIt works fine in the python2 interpreter, but I just can't get get it installed for python3 & need to write my programs in python3.\nI'm using Ubuntu 16.04 LTS Xenial Xerus & Python version 3.5.2. I've tried uninstalling & reinstalling the python3-openpyxl module but still get the error. Any help out there?\nThanks","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":798,"Q_Id":41077133,"Users Score":0,"Answer":"Since no one answered this, I will share my eventual work around. I backed up my files & installed Ubuntu 16.10 operating system from a bootable USB. Used Synaptic Package Manager to install openpyxl for Python3 & it is now working.\nNot sure this is a bona fide solution, but it worked for my purposes.","Q_Score":2,"Tags":"python-3.x,python-3.5,ubuntu-16.04,openpyxl","A_Id":41833582,"CreationDate":"2016-12-10T15:29:00.000","Title":"Openpyxl ImportError in Python 3.5.2","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I get this error \n\n\"ProgrammingError at \/admin\/\n  relation \"django_admin_log\" does not exist\n  LINE 1: ...\".\"app_label\", \"django_content_type\".\"model\" FROM \"django_ad...\"\n\ndjango_admin_log table does not exist in the database. Does anyone know how I can create it? I am not worried about deleting the data for my app.\nwhen i try '.\/manage.py sqlmigrate admin 0001' or '.\/manage.py sqlmigrate admin 0001'\ni get \n\"\nBEGIN;\n-- Create model LogEntry\nCREATE TABLE \"django_admin_log\" (\"id\" serial NOT NULL PRIMARY KEY, \"action_time\" timestamp with time zone NOT NULL, \"object_id\" text NULL, \"object_repr\" varchar(200) NOT NULL, \"action_flag\" smallint NOT NULL CHECK (\"action_flag\" >= 0), \"change_message\" text NOT NULL, \"content_type_id\" integer NULL, \"user_id\" integer NOT NULL);\nALTER TABLE \"django_admin_log\" ADD CONSTRAINT \"django_admin_content_type_id_c4bce8eb_fk_django_content_type_id\" FOREIGN KEY (\"content_type_id\") REFERENCES \"django_content_type\" (\"id\") DEFERRABLE INITIALLY DEFERRED;\nALTER TABLE \"django_admin_log\" ADD CONSTRAINT \"django_admin_log_user_id_c564eba6_fk_auth_user_id\" FOREIGN KEY (\"user_id\") REFERENCES \"auth_user\" (\"id\") DEFERRABLE INITIALLY DEFERRED;\nCREATE INDEX \"django_admin_log_417f1b1c\" ON \"django_admin_log\" (\"content_type_id\");\nCREATE INDEX \"django_admin_log_e8701ad4\" ON \"django_admin_log\" (\"user_id\");\nCOMMIT;\"\nbut i still get the same error? i use postgresql if anyone cares.","AnswerCount":3,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":2274,"Q_Id":41094926,"Users Score":0,"Answer":"After .\/manage.py sqlmigrate admin 0001, please run python manage.py migrate.","Q_Score":1,"Tags":"python,django,django-admin","A_Id":47960936,"CreationDate":"2016-12-12T05:56:00.000","Title":"I accidentally deleted django_admin_log and now i can not use the django admin","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I get this error \n\n\"ProgrammingError at \/admin\/\n  relation \"django_admin_log\" does not exist\n  LINE 1: ...\".\"app_label\", \"django_content_type\".\"model\" FROM \"django_ad...\"\n\ndjango_admin_log table does not exist in the database. Does anyone know how I can create it? I am not worried about deleting the data for my app.\nwhen i try '.\/manage.py sqlmigrate admin 0001' or '.\/manage.py sqlmigrate admin 0001'\ni get \n\"\nBEGIN;\n-- Create model LogEntry\nCREATE TABLE \"django_admin_log\" (\"id\" serial NOT NULL PRIMARY KEY, \"action_time\" timestamp with time zone NOT NULL, \"object_id\" text NULL, \"object_repr\" varchar(200) NOT NULL, \"action_flag\" smallint NOT NULL CHECK (\"action_flag\" >= 0), \"change_message\" text NOT NULL, \"content_type_id\" integer NULL, \"user_id\" integer NOT NULL);\nALTER TABLE \"django_admin_log\" ADD CONSTRAINT \"django_admin_content_type_id_c4bce8eb_fk_django_content_type_id\" FOREIGN KEY (\"content_type_id\") REFERENCES \"django_content_type\" (\"id\") DEFERRABLE INITIALLY DEFERRED;\nALTER TABLE \"django_admin_log\" ADD CONSTRAINT \"django_admin_log_user_id_c564eba6_fk_auth_user_id\" FOREIGN KEY (\"user_id\") REFERENCES \"auth_user\" (\"id\") DEFERRABLE INITIALLY DEFERRED;\nCREATE INDEX \"django_admin_log_417f1b1c\" ON \"django_admin_log\" (\"content_type_id\");\nCREATE INDEX \"django_admin_log_e8701ad4\" ON \"django_admin_log\" (\"user_id\");\nCOMMIT;\"\nbut i still get the same error? i use postgresql if anyone cares.","AnswerCount":3,"Available Count":2,"Score":0.1325487884,"is_accepted":false,"ViewCount":2274,"Q_Id":41094926,"Users Score":2,"Answer":"experienced the same issue, the best way is to copy the CREATE TABLE log, login to your database .\/manage.py dbshell and Paste the content over there without adding the last line (COMMIT ) it will solve the problem and manually create the table for you.","Q_Score":1,"Tags":"python,django,django-admin","A_Id":60692503,"CreationDate":"2016-12-12T05:56:00.000","Title":"I accidentally deleted django_admin_log and now i can not use the django admin","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am using the python mysql connector in a little script. The problem I'm facing is: when executing a select statement that returns 0 rows, I'm unable to close the cursor. When closing the cursor, \"mysql.connector.errors.InternalError: Unread result found\" is triggered. However, calling fetchall() results in an \"mysql.connector.errors.InterfaceError: No result set to fetch from.\" error.\nSo basically, I'm unable to close the cursor because of some unread data and I'm unable to read any data because there is no data to read.","AnswerCount":3,"Available Count":1,"Score":0.0665680765,"is_accepted":false,"ViewCount":2753,"Q_Id":41101246,"Users Score":1,"Answer":"It's been a while to this question but I'll post the solution I found anyway.\nUsing the official mysql connector for python, the rows are not fetched from the server until requested. As a result, if there are remaining rows, trying to close the connection throws an exception. One option is to use buffered cursor. A buffered cursor reads all rows from the server and the cursor can be closed at any point. However, this method comes with a memory cost.\nThere is a hard limit of one open cursor per connection for the mysql connector. Trying to open another cursor raised an exception.","Q_Score":1,"Tags":"python,mysql","A_Id":47078137,"CreationDate":"2016-12-12T12:44:00.000","Title":"How to properly handle empty data set with python mysql connector?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"How to get current_date - 1 day in sparksql, same as cur_date()-1 in mysql.","AnswerCount":5,"Available Count":1,"Score":0.0399786803,"is_accepted":false,"ViewCount":78284,"Q_Id":41114875,"Users Score":1,"Answer":"Yes, the date_sub() function is the right for the question, anyway, there's an error in the selected answer:\n\nReturn type: timestamp\n\nThe return type should be date instead, date_sub() function will trim any hh:mm:ss part of the timestamp, and returns only a date.","Q_Score":21,"Tags":"java,python,scala,apache-spark,apache-spark-sql","A_Id":53483109,"CreationDate":"2016-12-13T06:28:00.000","Title":"How to get today -\"1 day\" date in sparksql?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have an issue which may have two possible approaches to getting a solution, im open to either.\nI use a 3rd party application to download data daily into pandas dataframes, which I then write into a local postgres database. The dataframes are large, but since the database is local I simply use df.to_sql and it completes in a matter of seconds.\nThe problem is that now I have moved the database to a remote linux server (VPS). The same to_sql now takes over an hour. I have tried various values for chunksize but that doesn't help much.\nThis wouldn't be an issue if I could simply install the 3rd party app on that remote server, but the server OS does not use a GUI. Is there a way to run that 3rd party app on the server even though it requires a GUI? (note: it is a Windows app so I use wine to run it on my local linux machine and would presumably need to do that on the server as well).\nIf there is no way to run that app which requires a GUI on the VPS, then how should I go about writing these dataframes to the VPS from my local machine in a way that doesn't take over an hour? Im hoping there's some way to write the dataframes in smaller pieces or using something other than to_sql more suited to this.\nA really clunky, inelegant solution would be to write the dataframes to csv files, upload them to the server using ftp, then run a separate python script on the server to save the data to the db. I guess that would work but it's certainly not ideal.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":107,"Q_Id":41117150,"Users Score":0,"Answer":"After investigating countless possible solutions:\n\nCreating a tunnel to forward a port from my local machine to the server so it can access the 3rd party app.\nmodifying all my python code to manually insert the data from my local machine to the server using psycopg2 instead of pandas to_sql\nCreating a docker container for the 3rd party app that can be run on the server\nand several other dead ends or convoluted less than ideal solutions\n\nIn the end, the solution was to simply install the 3rd party app on the server using wine but then ssh into it using the -X flag. I can therefore access the gui on my local machine while it is running on the server.","Q_Score":0,"Tags":"python,postgresql,pandas,vps","A_Id":41165424,"CreationDate":"2016-12-13T09:05:00.000","Title":"Writing data to remote VPS database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":0},{"Question":"I used to use Varchar to text string of dynamical string length. Recently I saw people also use String with length to define it.\nWhat is the difference between them? Which one is better to use?","AnswerCount":1,"Available Count":1,"Score":1.0,"is_accepted":false,"ViewCount":29995,"Q_Id":41136136,"Users Score":10,"Answer":"From what I know,\n\nUse varchar if you want to have a length constraint\n\nUse string if you don't want to restrict the length of the text\n\n\n\nThe length field is usually required when the String type is used\nwithin a CREATE TABLE statement, as VARCHAR requires a length on most\ndatabases\nParameters\nlength - optional, a length for the column for use in DDL and CAST expressions.\nMay be safely omitted if no CREATE TABLE will be issued. Certain\ndatabases may require a length for use in DDL, and will raise an\nexception when the CREATE TABLE DDL is issued if a VARCHAR with no\nlength is included. Whether the value is interpreted as bytes or\ncharacters is database specific.\nSQLAlchemy Docs","Q_Score":8,"Tags":"python,sqlalchemy,sqldatatypes","A_Id":41136521,"CreationDate":"2016-12-14T06:27:00.000","Title":"What is the difference between Varchar and String in sqlalchemy's data type?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"So the issue is that apparently Django uses the sqlite3 that is included with python, I have sqlite3 on my computer and it works fine on its own. I have tried many things to fix this and have not found a solution yet.\nPlease let me know how I can fix this issue so that I can use Django on my computer.\n:~$ python\nPython 3.5.2 (default, Nov 6 2016, 14:10:16)\n[GCC 6.2.0 20161005] on linux\nType \"help\", \"copyright\", \"credits\" or \"license\" for more information.\n\n>>> import sqlite3\nTraceback (most recent call last):\n  File \"<stdin>\", line 1, in <module>\n  File \"\/usr\/local\/lib\/python3.5\/sqlite3\/__init__.py\", line 23, in <module>\n    from sqlite3.dbapi2 import *\n  File \"\/usr\/local\/lib\/python3.5\/sqlite3\/dbapi2.py\", line 27, in <module>\n    from _sqlite3 import *\nImportError: No module named '_sqlite3'\n\n>>> exit()","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":197,"Q_Id":41177692,"Users Score":1,"Answer":"I figured out that this error was caused by me changing my python path to 3.5 from the default of 2.7.","Q_Score":0,"Tags":"linux,django,python-3.x,ubuntu,sqlite","A_Id":41196939,"CreationDate":"2016-12-16T05:17:00.000","Title":"How do I configure the sqlite3 module to work with Django 1.10?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am using openpyxl to write to a workbook. But that workbook needs to be closed in order to edit it. Is there a way to write to an open Excel sheet? I want to have a button that runs a Python code using the commandline and fills in the cells.\nThe current process that I have built is using VBA to close the file and then Python writes it and opens it again. But that is inefficient. That is why I need a way to write to open files.","AnswerCount":5,"Available Count":2,"Score":0.0798297691,"is_accepted":false,"ViewCount":18268,"Q_Id":41191394,"Users Score":2,"Answer":"No this is not possible because Excel files do not support concurrent access.","Q_Score":9,"Tags":"python,python-3.x,openpyxl","A_Id":41207062,"CreationDate":"2016-12-16T19:39:00.000","Title":"How to write to an open Excel file using Python?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am using openpyxl to write to a workbook. But that workbook needs to be closed in order to edit it. Is there a way to write to an open Excel sheet? I want to have a button that runs a Python code using the commandline and fills in the cells.\nThe current process that I have built is using VBA to close the file and then Python writes it and opens it again. But that is inefficient. That is why I need a way to write to open files.","AnswerCount":5,"Available Count":2,"Score":0.0798297691,"is_accepted":false,"ViewCount":18268,"Q_Id":41191394,"Users Score":2,"Answer":"Generally, two different processes shouldn't not be writing to the same file because it will cause synchronization issues.\nA better way would be to close the existing file in parent process (aka VBA code) and pass the location of the workbook to python script. \nThe python script will open it and write the contents in the cell and exit.","Q_Score":9,"Tags":"python,python-3.x,openpyxl","A_Id":41194215,"CreationDate":"2016-12-16T19:39:00.000","Title":"How to write to an open Excel file using Python?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"The application should read data from a serial port every 15 minutes (using the Modbus Protocol) and put them into a database. The data can then be viewed and manipulated in a web interface. I'm using Windows (no server) with a RAID system to prevent data loss.\nMy current setup looks like this:\n\nusing pyserial and minimalmodbus for reading the data and putting them into a MySQL database\nsetting a cron job to run the script every 15 minutes (alternatives?)\nusing Django in order to have a neat interface where one can view stats and download the data as a *.csv file\n\nMy questions are:\n\nDoes this setup makes sense concerning reliability; do you have any improvements?\nHow can i detect if the system has experienced a shutdown and i lost some data?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":120,"Q_Id":41208473,"Users Score":0,"Answer":"For detecting system shutdown compare time stamps of last reading taken to current reading's time stamp. If they differ by more than 15 minutes than something went wrong during the operation.","Q_Score":0,"Tags":"python,django,cron,serial-port","A_Id":41216333,"CreationDate":"2016-12-18T12:48:00.000","Title":"Python reliable project setup: write data from a serial port to a database in a certain time interval","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I want to change mysql's sql_mode to 'NO_UNSIGNED_SUBTRACTION' , when using pyspark. Is there any way?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":156,"Q_Id":41235051,"Users Score":0,"Answer":"I find a solution:\n   add &sessionVariables=sql_mode='NO_UNSIGNED_SUBTRACTION' to jdbc url.","Q_Score":0,"Tags":"python,mysql,apache-spark,pyspark","A_Id":41235443,"CreationDate":"2016-12-20T04:46:00.000","Title":"Is there any way to set mysql's sql_mode in pyspark?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I want to generate excel spreadsheets by python, the first few tabs are exactly same, all are refer to the last page, so how to insert the last page by openpyxl? because the first few tabs are too complex so load_workbook is always failed, is there have any other way to insert tabs without loading?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":198,"Q_Id":41252907,"Users Score":0,"Answer":"As far as i know, openpyxl does not allow you to access only one cell, or a limited number of cells for that matter. In order to access any information in a given worksheet, openpyxl will create one in the memory. This is the reason for which you will be unable to add a Sheet without opening the entire document in memory and overwriting it at the end.","Q_Score":0,"Tags":"python,excel,openpyxl","A_Id":43180932,"CreationDate":"2016-12-20T23:33:00.000","Title":"How to use openpyxl to insert one sheet to a template?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Is closing a cursor needed when the shortcut conn.execute is used in place of an explicitly named cursor in SQLite?  If so how is this done?  Also, is closing a cursor only need for SELECT, when a recordset is returned, or is it also needed for UPDATE, etc.?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":127,"Q_Id":41263383,"Users Score":0,"Answer":"The close() method allows you to close a cursor object before it is garbage collected.\nThe connection's execute() method is exactly the same as conn.cursor().execute(...), so the return value is the only reference to the temporary cursor object. When you just ignore it, CPython will garbage-collect the object immediately (other Python implementations might work differently).","Q_Score":1,"Tags":"python,sqlite,cursor","A_Id":41485462,"CreationDate":"2016-12-21T12:59:00.000","Title":"How does closing SQLite cursor apply when conn.execute is used in place of named cursor","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am wondering if there is any way to create a new model table in SQLite with Django 1.10 (like writing general python code) without having to specify in the models.py. The situation is if there is a new member registered on my website, then I will create a new model table for them to hold their data. Specifically:\nstep 1: John Doe registered on my site\nstep 2: The system create a model table named db_johnDoe (with same set of fields as of the others)\nstep 3: The system can insert and edit data of the db_johnDoe according to John's behavior on the website. \nAny idea? Thanks a lot.","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":292,"Q_Id":41338208,"Users Score":1,"Answer":"I think it's not a good idea to create a table for each user. This may cause bad performance and low security. Why don't you create a table named userInfo and put user.userID as a foreign key?","Q_Score":0,"Tags":"database,sqlite,python-3.x,django-models","A_Id":41338383,"CreationDate":"2016-12-27T02:16:00.000","Title":"Django 1.10 Create Model Tables Automatically","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"We're using SQLAlchemy and Alembic (along with Flask-SQLAlchemy and Flask-Migrate). How to check if there are pending migrations?\nI tried to check both Alembic's and Flask-Migrate's documentation but failed to find the answer.","AnswerCount":3,"Available Count":1,"Score":1.0,"is_accepted":false,"ViewCount":4164,"Q_Id":41343316,"Users Score":7,"Answer":"You can figure out if your project as at the latest migration with the current subcommand:\nExample output when you are at the latest migration:\n(venv) $ python app.py db current\nf4b4aa1dedfd (head)\n\nThe key thing is the (head) that appears after the revision number. That tells you that this is the most recent migration.\nHere is how things change after I add a new migration, but before I upgrade the database:\n(venv) $ python app.py db current\nf4b4aa1dedfd\n\nAnd after I run db upgrade I get:\n(venv) $ python app.py db current\nf3cd9734f9a3 (head)\n\nHope this helps!","Q_Score":8,"Tags":"python,sqlalchemy,flask-sqlalchemy,alembic,flask-migrate","A_Id":41357149,"CreationDate":"2016-12-27T10:24:00.000","Title":"How to check if there are pending migrations when using SQLAlchemy\/Alembic?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm trying to save a snapshot of several tables programatically in python, instead of all DB.\nI couldn't find the API (in boto\/boto3) to do that.\nIs it possible to do?","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":540,"Q_Id":41361091,"Users Score":1,"Answer":"This is not possible using the AWS RDS snapshot mechanism, and it isn't possible using the AWS SDK. It is possible using the API for the specific database engine you are using. You would need to specify what database you are using for further help.","Q_Score":0,"Tags":"python,amazon-web-services,snapshot,boto3,rds","A_Id":41363444,"CreationDate":"2016-12-28T11:25:00.000","Title":"AWS RDS save snapshot of selected tables","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have been using the mysql.connector module with Python 2.7 and testing locally using XAMPP.  Whenever I upload my script to the server, I am getting an import error for the mysql.connector module.  I am assuming this is because, unlike my local machine, I have not installed the mysql.connector module on the server.  \nMy question is: can I somehow use the mysql.connector module on the server or is this something only for local development?  I have looked into it, and apparently do not have SSH access for my server, only for the database.  As well, if I cannot use the mysql.connector module, how do I connect to my MySQL database from my Python script on the server?","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":95,"Q_Id":41454355,"Users Score":0,"Answer":"You can use mysql.connector on the server. However, you will have to install it first. Do you have root (admin) access? If no, you might need help from the server admin.","Q_Score":0,"Tags":"python,mysql","A_Id":41454481,"CreationDate":"2017-01-04T00:17:00.000","Title":"Can you use Python mysql.connector on actual Server?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am using MongoDB 3.4 and Python 2.7.  I have retrieved a document from the database and I can print it and the structure indicates it is a Python dictionary. I would like to write out the content of this document as a JSON file. When I create a simple dictionary like d = {\"one\": 1, \"two\": 2} I can then write it to a file using json.dump(d, open(\"text.txt\", 'w'))\nHowever, if I replace d in the above code with the the document I retrieve from MongoDB I get the error \n\nObjectId is not JSON serializable\n\nSuggestions?","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":5356,"Q_Id":41465836,"Users Score":1,"Answer":"The issue is that \u201c_id\u201d is actually an object and not natively deserialized.  By replacing the _id with a string as in mydocument['_id'] ='123 fixed the issue.","Q_Score":5,"Tags":"json,mongodb,python-2.7","A_Id":41470959,"CreationDate":"2017-01-04T14:10:00.000","Title":"Create JSON file from MongoDB document using Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"Having some odd trouble scheduling a task for a python script. Specifically this script and the problem is intermittent, which made me hesitant to pose the question because I'm very confused. I have other scheduled scripts that run fine. This one is the only one modifying a SQLite database though.\nI call the script daily, I've done this several ways with the same result. I finally settled on Action \"start a program\", Program\/script: \"python\" (it is in my path, but i've also directly called py.exe and pyw.exe, with the same result). Add arguments: \"scriptname.py\". Start in \"location of script and database file\" which the account I'm using in the scheduler has full read\/write\/execute access to. And I've instructed this to work whether or not the user is logged in.\nI use this same operation for several other scripts and they are fine, this one just doesn't work sometimes. It always runs, but every few days it exits with code 2147942401 instead of 0. On these days the database is not updated, so I suppose it had trouble writing? I'm not sure. It seems this error code in windows is associated with invalid function, but I can manually run the script and everything is fine. And half the days (not exactly half, seemingly randomly), it doesn't work. This never happened until about 3 weeks ago. Nothing changed that I'm aware of, everything has been running fine for months and then bam, exit code 2147942401. It did it several days in a row, and then no problems for a few days. Never a problem running task (or script) manually. It is set to run with highest privileges.\nAnyone seen anything like this?","AnswerCount":1,"Available Count":1,"Score":0.537049567,"is_accepted":false,"ViewCount":7724,"Q_Id":41471776,"Users Score":3,"Answer":"Turns out it was my script breaking. This is the error code (oddly enough there's not much documentation) you get when your python program ends with code -1 (exits without finishing properly or has some unhandled exception). It was intermittent because I was checking a web page and sometimes that web server just didn't respond for any number of reason. Leaving this here for posterity. If you get this error code in task scheduler, write some logging and error handling into your script because it may be a weird problem you didn't think of.","Q_Score":2,"Tags":"python,sqlite,task,scheduler,exit","A_Id":41575621,"CreationDate":"2017-01-04T19:26:00.000","Title":"Windows Task Scheduler, python script, code 2147942401","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Looking for an Excel library for Django and Python with specific requirements.\nThere looks to be a number of libraries for Django and Python that enable the user to upload an Excel document into the database.\nWhat I am wondering is if there is a library that allows you to create an Excel document and export with conditional formatting, live formulas, creating tabs, and VLOOKUPS?\nThe company I work for produces Excel reports for our analysts to review that requires these types of things. Researching as we are exploring other solutions than using Access, which is it pretty easy to control Excel from.","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":199,"Q_Id":41498803,"Users Score":1,"Answer":"I think a combination of Pandas and openpyxl will do the trick!","Q_Score":0,"Tags":"python,django,excel","A_Id":41498821,"CreationDate":"2017-01-06T04:11:00.000","Title":"Django\/Python Library for importing and producing Excel documents?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I currently have a database setup where there are 5 columns set as the composite primary key which could uniquely identify a row. Should I still have an ID column to identify each row? It seems redundant, although I am not sure of what is standard.\nI am using SQLAlchemy. I noticed that when I had the 5 columns as the composite primary key, the table was significantly slower inserting the data from a CSV file, as compared to if I had an ID column. It was half the speed with the column (not sure if this is relevant).\nTo be clear: My question is, Should I have an ID column alongside the composite primary key, even though the ID column would be redundant?","AnswerCount":1,"Available Count":1,"Score":-0.1973753202,"is_accepted":false,"ViewCount":199,"Q_Id":41529910,"Users Score":-1,"Answer":"Yes, you should always have a separate rowid (either int based one-up or UUID).  Especially when you get into other aspects of mysql or database DevOps, having that ID field is a lifesaver (e.g., replication or galera clustering).  It also makes working with frameworks like django much easier.","Q_Score":1,"Tags":"python,mysql,sqlalchemy","A_Id":41530033,"CreationDate":"2017-01-08T05:50:00.000","Title":"Can I composite primary key be used in place of an ID primary key?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am new to Python.\nI use putty to manage some servers. I want to use Python to create a Excel file on each server, for that I think if I can use some orders like ssh ip \"python abc.py\" to create the file. It is possible to write a bash script to manage all servers. This is the trouble I meet:\n\nThe servers can't use internet. \n\nAnd it is not allowed to use any third party libraries. When a linux(redhat 6.5) was installed, is there any library in python that can be used to create Excel immediately?\nPlease help me, thanks.","AnswerCount":5,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":15636,"Q_Id":41550060,"Users Score":0,"Answer":"I am not sure if this is what the OP was looking for,but if you have to manipulate data in python without installing any modules (just standard library), you can try the sqlite3 module, which of course allows you to interact with sqlite files (a Relational Database Management System).\nThese databases are conceptually similar to an Excel file. If an excel file is basically a collection of sheets, with each sheet being a matrix where you can put data, sqlite databases are the same (but each \"matrix\" is called a table instead).\nThis format is scripting friendly, as you can read and write data using SQL, but it does not follow the client-server model other DBMS are based on. The whole database is contained in a single file that you can email to a colleague, and you can also install a GUI that gives you a spreadsheet like interface to make it more user-friendly (DB browser for SQLite is avaible for Windows, Linux and Mac).\nThis allows you to include SQL code in your python scripts, which adds a lot of data processing capabilities, and it is an excellent way to achieve data persistence for simple programs.","Q_Score":4,"Tags":"python,excel","A_Id":60421964,"CreationDate":"2017-01-09T14:21:00.000","Title":"how to create a excel file only with python standard library?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am developing a Cloud based data analysis tool, and I am using Django(1.10) for that.\nI have to add columns to the existing tables, create new tables, change data-type of columns(part of data-cleaning activity) at the run time and can't figure out a way to update\/reflect those changes, in run time, in the Django model, because those changes will be required in further analysis process.\nI have looked into 'inspectdb' and 'syncdb', but all of these options would require taking the portal offline and then making those changes, which I don't want.\nPlease can you suggest a solution or a work-around of how to achieve this.\nAlso, is there a way in which I can select what database I want to work from the list of databases on my MySQL server, after running Django.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":43,"Q_Id":41591079,"Users Score":0,"Answer":"Django's ORM might not be the right tool for you if you need to change your schema (or db) online - the schema is defined in python modules and loaded once when Django's web server starts.\nYou can still use Django's templates, forms and other libraries and write your own custom DB access layer that manipulates a DB dynamically using python.","Q_Score":0,"Tags":"python,django,django-1.10","A_Id":41592978,"CreationDate":"2017-01-11T12:32:00.000","Title":"Changing Database in run time and making the changes reflect in Django in run time","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"My main problem is that I would like to check if someone with the same SSN has multiple accounts with us. Currently all personally identifiable info is encrypted and decryption takes a non-trivial amount of time.\nMy initial idea was to add a ssn column to the user column in the database. Then I could simply do a query where I get all users with the ssn or user A.\nI don't want to store the ssn in plaintext in the database. I was thinking of just salting and hashing it somehow.\nMy main question is, is this secure (or how secure is it)? What is there a simple way to salt and hash or encrypt and ssn using python?\nEdit: The SSN's do not need to be displayed.\nThis is using a MySQL database.","AnswerCount":3,"Available Count":2,"Score":-0.0665680765,"is_accepted":false,"ViewCount":2477,"Q_Id":41599285,"Users Score":-1,"Answer":"Your question doesn't make it clear if you need to display those SSNs. I'm going to assume you do not. Store the SSN in a SHA2 hash. You can then do a SQL query to search against those hashed values. Store only the last 4 digits encrypted for display.","Q_Score":2,"Tags":"python,sql,security,hash","A_Id":41599436,"CreationDate":"2017-01-11T19:35:00.000","Title":"How to securely and efficiently store SSN in a database?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"My main problem is that I would like to check if someone with the same SSN has multiple accounts with us. Currently all personally identifiable info is encrypted and decryption takes a non-trivial amount of time.\nMy initial idea was to add a ssn column to the user column in the database. Then I could simply do a query where I get all users with the ssn or user A.\nI don't want to store the ssn in plaintext in the database. I was thinking of just salting and hashing it somehow.\nMy main question is, is this secure (or how secure is it)? What is there a simple way to salt and hash or encrypt and ssn using python?\nEdit: The SSN's do not need to be displayed.\nThis is using a MySQL database.","AnswerCount":3,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":2477,"Q_Id":41599285,"Users Score":4,"Answer":"Do not encrypt SSNs, when the attacker gets the DB he will also get the encryption key.\nJust using a hash function is not sufficient and just adding a salt does little to improve the security.\nBasically handle the SSNs inthe same mannor as passwords.\nInstead iIterate over an HMAC with a random salt for about a 100ms duration and save the salt with the hash. Use functions such as PBKDF2 (aka Rfc2898DeriveBytes), password_hash\/password_verify, Bcrypt and similar functions. The point is to make the attacker spend a lot of time finding passwords by brute force. Protecting your users is important, please use secure password methods.","Q_Score":2,"Tags":"python,sql,security,hash","A_Id":41600634,"CreationDate":"2017-01-11T19:35:00.000","Title":"How to securely and efficiently store SSN in a database?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I want to write a lot of data to a lmdb data base with several named (sub) data bases.  I run into the following problem:\n\nTo write to one named data base, I need to open a transaction for this named data base.\nThis implies: To write to another named data base, I need to open a different transaction.\nTwo write transaction inside the same main data base cannot exist at the same time.\nThis implies: I need to commit and close a transaction each time I want to switch from writing to one named data base to writing to another named data base.\nCreating and committing write transactions is a really slow operation.\n\nI rather would like to keep one long-running write transaction for all write operations and commit it once --- when all the work is done.\nIs this possible with lmdb (if yes, at which point did I err in my analysis)?","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":1421,"Q_Id":41616426,"Users Score":1,"Answer":"You can open as many named databases within the same write transaction as you like.\nSo:\n\nOpen write transaction\nOpen named databases as required and write to them\nCommit your transaction\n\nAs long as you take into account that you can only ever have one write-transaction at a time (read-only transactions are no problem), and that your other transactions will only see the result of your write-transaction once you commit, you can of course have one long-running write transaction.","Q_Score":0,"Tags":"python,python-3.x,lmdb","A_Id":42486747,"CreationDate":"2017-01-12T15:03:00.000","Title":"lmdb: Can I access different named databases in the same transaction?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I wrote a python script to download some files from an s3 bucket. The script works just fine on one machine, but breaks on another. \nHere is the exception I get: botocore.exceptions.ClientError: An error occurred (403) when calling the HeadObject operation: Forbidden.\nI am pretty sure it's related to some system configurations, or something related to the registry, but don't know what exactly. Both machines are running Windows 7 and python 3.5.\nAny suggestions.","AnswerCount":2,"Available Count":1,"Score":1.0,"is_accepted":false,"ViewCount":8191,"Q_Id":41646514,"Users Score":8,"Answer":"The issue was actually being caused by the system time being incorrect. I fixed the system time and the problem is fixed.","Q_Score":6,"Tags":"python,windows,amazon-web-services,amazon-s3,boto3","A_Id":41682857,"CreationDate":"2017-01-14T03:29:00.000","Title":"Trying to access a s3 bucket using boto3, but getting 403","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":1,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am using Python openpyxl package to read values from Excel cells. Cells with formulas always return formula strings instead of the calculated values. I'd rather avoid using 'data_only=True' when loading the workbook as it wipes out all the formulas and I do need to retain some of them. Seemingly a problem not so difficult but turns out to be quite challenging. Appreciate it very much if anyone can shed some lights on this. Thanks a lot!","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1063,"Q_Id":41708061,"Users Score":0,"Answer":"Sorted it out myself and like to share with you guys. xlwings actually does the job while openpyxl\/xlrd seem to have failed around this issue.","Q_Score":0,"Tags":"excel,python-2.7","A_Id":41767777,"CreationDate":"2017-01-17T22:20:00.000","Title":"Python to read Excel cell with the value calculated by the formulas but not the formula strings themselves","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am trying to install MySql Server on Win 8 and as I go through the process, the installer requires Python 3.4 so I installed it manually with the given link of the installer.\nI have installed Python 3.4.6 as it is the latest version but still it is not recognized and the installer returns an error message saying the \"The requirement is still failing\". \nShould I install Python 3.4 instead of 3.4.6?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":131,"Q_Id":41789489,"Users Score":0,"Answer":"I have installed Phyton 3.4 and uninstalled the 3.4.6 version and it worked, I don't know why but it worked","Q_Score":0,"Tags":"php,python,mysql","A_Id":41790010,"CreationDate":"2017-01-22T09:51:00.000","Title":"MySql Server installation dont recognize python 3.4.6","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I must load the Oracle \"instant client\" libraries as part of my AWS lambda python deployment zip file.\nProblem is, many of the essential libraries (libclntsh.so.12.1 is 57MB libociei.so is 105MB) and Amazon only allows deployment zip files under 50MB.   \nI tried: my script cannot connect to Oracle using cx_Oracle without that library in my local ORACLE_HOME and LD_LIBRARY_PATH.  \nHow can I get that library into Lambda considering their zip file size limitation? Linux zip just doesn't compress them enough.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":846,"Q_Id":41833790,"Users Score":3,"Answer":"If you can limit yourself to English error messages and a restricted set of character sets (which does include Unicode), then you can use the \"Basic Lite\" version of the instant client. For Linux x64 that is only 31 MB as a zip file.","Q_Score":1,"Tags":"python,oracle,amazon-web-services,lambda,cx-oracle","A_Id":41837986,"CreationDate":"2017-01-24T16:48:00.000","Title":"AWS python Lambda script that can access Oracle: Driver too big for 50MB limit","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":0},{"Question":"I have some employee data in which there are 3 different roles. Let's say CEO, Manager and Developer. \nCEO can access the whole graph, managers can only access data of some people (their team) and developers can not access employee data.\nHow should I assign subgraph access to user roles and implement this using Python?\nThere are good solutions and comprehensive libraries and documentations but only in Java!","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":304,"Q_Id":41850411,"Users Score":1,"Answer":"At the moment it is not possible to write procedures for custom roles to implement subgraph access control using Python. It is only possible in Java.\nA workaround might be to indirektly implement it using phyton by adding properties to nodes and relationship storing the security levels for these nodes and relationships. Checking the secutiry level of a user it might be possible to use a phyton visualization that checks the properties to only display nodes and relationships that are in agreement with the user security level.","Q_Score":2,"Tags":"python,neo4j,authorization,graph-databases,py2neo","A_Id":42622083,"CreationDate":"2017-01-25T11:25:00.000","Title":"Authorization (subgraph access control) in Neo4j with python driver","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":1,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm trying to figure out how to download a file from google cloud storage bucket.\nMy use-case is to run a scheduled script which downloads a .csv file once a day and save it to a SQL DB.\nI considered doing it using python and the google SDK but got lost with all the options and which one is the right for me.\nCould someone can explain the difference between cloud storage client, boto, gsutil, and google cloud SDK?\nThanks!","AnswerCount":2,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":736,"Q_Id":41862312,"Users Score":2,"Answer":"Look into gcs-fuse: Makes like a lot easier since you then can use the GCS as just a standard file system.","Q_Score":0,"Tags":"python,google-cloud-storage,boto,google-developer-tools","A_Id":41862332,"CreationDate":"2017-01-25T21:51:00.000","Title":"Programatically download file from google cloud storage bucket","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"How can I write an excel file(xls\/xlsx) using xlrd module alone?\nI tried from xlrd import xlsx, but couldn't find anything that will really help me.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":4503,"Q_Id":41886791,"Users Score":2,"Answer":"xlrd only reads excel files.  To write them, look up xlwt, xlutils, xlsxwriter, or openpyxl - all of these packages can write binary files excel can read.  Excel can also read csv files, which the csv package (included with Python) can write (and read).","Q_Score":1,"Tags":"python,excel,python-3.x,module,xlrd","A_Id":41904256,"CreationDate":"2017-01-27T04:04:00.000","Title":"How to use xlrd for writing an excel file","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Hi Stack Overflow community, making some architectural decisions & trying to figure out the best strategy to store locations of 50k users who are moving around, in an environment where we care about read & write speed a lot, but don't mind occasionally losing data. \nShould one \n\nuse an in-memory datastore like Redis or Memcached, or  \nuse Postgres, with an index on the user_id so that it's fast to insert &\nremove, or  \nuse the filesystem directly, have a file for each\nuser_id, and write to it or read from it to store new locations, or \njust store the locations in memory, in a Python program which\nmaintains an ordered list of (user_id, location) tuples\n\nWhat are the advantages\/ disadvantages of each?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":180,"Q_Id":41916404,"Users Score":1,"Answer":"I've had tremendous luck with MySQL and SQLAlchemy.  50k writes per day is nothing.  I write my logs to it, I log my threads (think about that, I write logs to it and log each thread) and I process 2.5 million records per day, each generating about 100 logs each.","Q_Score":0,"Tags":"python,postgresql,memory,redis,memcached","A_Id":41916446,"CreationDate":"2017-01-29T00:29:00.000","Title":"Best database to store locations of users as they move, priority given to read & write speed?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"How beneficial will it be to use Python\/PHP Nonpersistent array for storing 6GB+ data with 800+ million rows in RAM, rather than using MySQL\/MongoDB\/Cassandra\/BigTable\/BigData(Persistence Database) database when it comes to speed\/latency in simple query execution?\nFor example, finding one name in 800+ million rows within 1 second: is it possible? Does anyone have experience of dealing with a dataset of more than 1-2 billion rows and getting the result within 1 second for a simple search query?\nIs there a better, proven methodology to deal with billions of rows?","AnswerCount":3,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":472,"Q_Id":41935280,"Users Score":0,"Answer":"You can still take advantage of RAM based lookup,and still having extra functionalities that specialized databases provide as compared to a plain hashmap\/array in RAM.\nYour objective with ram based lookups is faster lookups, and avoid network overhead. However both can be achieved by hosting the database locally,  or network would not even be a overhead for small data payloads like names.\nBy the RAM array method, the apps' resilience decreases as you have a single point of failure, no easy snapshotting i.e. you would have to do some data warming everytime your app changes or restarts, and you will always be restricted to single querying pattern and may not be able to evolve in future.\nEqually good alternatives with reasonably comparable throughput can be redis in a cluster or master-slave configuration, or aerospike on SSD machines. You get advantage of constant snapshots,high throughput,distribution and resilience through sharding\/clustering i.e. 1\/8 of data in 8 instances so that there is no single point of failure.","Q_Score":16,"Tags":"python,mongodb,optimization,query-optimization,bigdata","A_Id":45958112,"CreationDate":"2017-01-30T11:53:00.000","Title":"Persistence Database(MySQL\/MongoDB\/Cassandra\/BigTable\/BigData) Vs Non-Persistence Array (PHP\/PYTHON)","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"How beneficial will it be to use Python\/PHP Nonpersistent array for storing 6GB+ data with 800+ million rows in RAM, rather than using MySQL\/MongoDB\/Cassandra\/BigTable\/BigData(Persistence Database) database when it comes to speed\/latency in simple query execution?\nFor example, finding one name in 800+ million rows within 1 second: is it possible? Does anyone have experience of dealing with a dataset of more than 1-2 billion rows and getting the result within 1 second for a simple search query?\nIs there a better, proven methodology to deal with billions of rows?","AnswerCount":3,"Available Count":2,"Score":0.2605204458,"is_accepted":false,"ViewCount":472,"Q_Id":41935280,"Users Score":4,"Answer":"It should be very big different, around 4-5 orders of magnitude faster. The database stores records in 4KB blocks (usually), and has to bring each such block into memory it needs some milliseconds. Divide the size of your table with 4KB and get the picture. In contrast, corrresponding times for in-memory data are usually nanoseconds. There is no question that memory is faster, the real question is if you have enough memory and how long you can keep your data there.\nHowever, the above holds for a select * from table query. If you want a select * from table where name=something, you can create an index on the name, so that the database does not have to scan the whole file, and the results should be much, much better, probably very satisfying for practical use.","Q_Score":16,"Tags":"python,mongodb,optimization,query-optimization,bigdata","A_Id":41935572,"CreationDate":"2017-01-30T11:53:00.000","Title":"Persistence Database(MySQL\/MongoDB\/Cassandra\/BigTable\/BigData) Vs Non-Persistence Array (PHP\/PYTHON)","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"We are looking for a solution which uses minimum read\/write units of DynamoDB table for performing full backup, incremental backup and restore operations. Backup should store in AWS S3 (open to other alternatives). We have thought of few options such as:\n1)  Using python multiprocessing and boto modules we were able to perform Full backup and Restore operations, it is performing well, but is taking more DynamoDB read\/write Units.\n2)  Using AWS Data Pipeline service, we were able to perform Full backup and Restore operations.\n3)  Using Dynamo Streams and kinesis Adapter\/ Dynamo Streams and Lambda function, we were able to perform Incremental backup.\nAre there other alternatives for Full backup, Incremental backup and Restore operations. The main limitation\/need is to have a scalable solution by utilizing minimal read\/write units of DynamoDb table.","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":1135,"Q_Id":41973955,"Users Score":1,"Answer":"Option #1 and #2 are almost the same- both do a Scan operation on the DynamoDB table, thereby consuming maximum no. of RCUs.\nOption #3 will save RCUs, but restoring becomes a challenge. If a record is updated more than once, you'll have multiple copies of it in the S3 backup because the record update will appear twice in the DynamoDB stream. So, while restoring you need to pick the latest record. You also need to handle deleted records correctly.\nYou should choose option #3 if the frequency of restoring is less, in which case you can run an EMR job over the incremental backups when needed. Otherwise, you should choose #1 or #2.","Q_Score":3,"Tags":"python-2.7,amazon-web-services,amazon-dynamodb,amazon-dynamodb-streams","A_Id":42009940,"CreationDate":"2017-02-01T07:14:00.000","Title":"How to perform AWS DynamoDB backup and restore operations by utilizing minimal read\/write units?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm using S3 instead of KMS to store essentially a credentials file, and Python to read the file's contents.\nI manually set the file encrypted by clicking on it in S3, going to Properties - Details - Server Side Encryption:AES-256\nAnd in my Python script, I read the key without making changes from when I read the file when it was unencrypted. And I was also able to download the file and open it without having to do anything like decrypting it. I was expecting to have to decrypt it, so I'm a little confused.\nI'm just unable to understand what server-side encryption protects against. Would anyone already with access to S3 or the S3 bucket with the key\/file be able to read the file? Who wouldn't be able to open the file?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":3317,"Q_Id":41987133,"Users Score":7,"Answer":"The \"server-side\" encryption you have enabled turns on encryption at rest. Which means the file is encrypted while it's sitting on S3. But S3 will decrypt the file before it sends you the data when you download the file.\nSo there is no change to how you handle the file when downloading it if the file is encrypted or not.\nThis type of encryption does not protect the file if the file is downloaded via valid means, such as when using the API. It only protects the file from reading if someone were to circumvent the S3 data center or something like that. \nIf you need to protect the file, such that it must be decrypted when downloaded, then you need to encrypt it client-side, before uploading it to S3. \nYou can use any client-side encryption scheme you deem worthy: AES256, etc. But S3 won't do it for you.","Q_Score":1,"Tags":"python,amazon-web-services,encryption,amazon-s3","A_Id":41987427,"CreationDate":"2017-02-01T18:34:00.000","Title":"Do I ever have to decrypt S3-encrypted files?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"How to insert datetime string like this \"2017-10-13T10:53:53.000Z\" into mongo db as ISODate? \nI get a string in mongodb when I insert:\n datetime.strptime(\"2017-10-13T10:53:53.000Z\", \"%Y-%m-%dT%H:%M:%S.000Z\")","AnswerCount":2,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":43049,"Q_Id":41999094,"Users Score":2,"Answer":"use dateutil\ndateutil.parser.parse(\"2017-10-13T10:53:53.000Z\")\nwill return datetime.datetime(2017, 10, 13, 10, 53, 53, tzinfo=tzutc())","Q_Score":25,"Tags":"python,pymongo","A_Id":41999635,"CreationDate":"2017-02-02T09:58:00.000","Title":"How to insert datetime string into Mongodb as ISODate using pymongo","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I was wondering if there is a way to allow a user to export a SQLite database as a .csv file, make some changes to it in a program like Excel, then upload that .csv file back to the table it came from using a record UPDATE method.\nCurrently I have a client that needed an inventory and pricing management system for their e-commerce store. I designed a database system and logic in Python 3 and SQLite. The system from a programming standpoint works flawlessly.\nThe problem I have is that there are some less then technical office staff that need to edit things like product markup within the database. Currently, I have them setup with SQLite DB Browser, from there they can edit products one at a time and write the changes to the database. They can also export tables to a .csv file for data manipulation in Excel.\nThe main issue is getting that .csv file back into the table it was exported from using an UPDATE method. When importing a .csv file to a table in SQLite DB Browser there is no way to perform an update import. It can only insert new rows by default and do to my table constraints that is a problem. \nI like SQLite DB Browser because it is clean and simple and does exactly what I need. However, as soon as you have to edit more then one thing at a time and filter information in more complicated ways it starts to lack the functionality needed. \nIs there a solution out there for SQLite DB Browser to tackle this problem? Is there a better software option all together to interact with a SQLite database that would give me that last bit of functionality?","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":572,"Q_Id":42008720,"Users Score":0,"Answer":"So after researching some off the shelf options I found that the Devart Excel Add Ins did exactly what I needed. They are paid add ins, however, they seem to support almost all modern databases including SQlite. Once the add in is installed you can connect to a database and manipulate the data returned just like normal in Excel including bulk edits and advanced filtering, all changes are highlighted and can easily be written to the database with one click.\nOverall I thought it was a pretty solid solution and everyone seems to be very happy with it as it made interacting with a database intuitive and non threatening to the more technically challenged.","Q_Score":0,"Tags":"python,database,sqlite,csv","A_Id":42173826,"CreationDate":"2017-02-02T17:34:00.000","Title":"User friendly SQLite database csv file import update solution","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm using query like this:\nuser = User.query.options(load_only(\"email\", \"name\")).filter(and_(User.id == id, User.status == 1)).first()\nI want to get only email and name column as an User object. But it returns all columns. \nI can't find any solutions. Can anybody help? Thanks","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":1278,"Q_Id":42019810,"Users Score":1,"Answer":"If you're using a database session, you can simply specify the columns directly.\nsession.query(User.email, User.name).filter(and_(User.id == id, User.status == 1)).first()","Q_Score":3,"Tags":"python,sqlalchemy","A_Id":42028145,"CreationDate":"2017-02-03T08:27:00.000","Title":"SQLAlchemy ORM Load Cols Only not working","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I want to insert document to the collection from json file it says bson.errors.InvalidDocument: key '$oid' must not start with '$'\nHow can I solve it?\nexample of document:\n\n[{\"name\": \"Company\", \"_id\": {\"$oid\": \"1234as123541gsdg\"}, \"info\": {\"email\": \"test@gmail.com\"}}]","AnswerCount":2,"Available Count":1,"Score":-0.0996679946,"is_accepted":false,"ViewCount":9580,"Q_Id":42089045,"Users Score":-1,"Answer":"Try removing all white space in the files (\\n, spaces outside string quotes). It may work like miracle","Q_Score":5,"Tags":"python,pymongo","A_Id":63628554,"CreationDate":"2017-02-07T11:44:00.000","Title":"bson.errors.InvalidDocument: key '$oid' must not start with '$' trying to insert document with pymongo","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm building a platform with a PostgreSQL database (first time) but I've experience with Oracle and MySQL databases for a few years now.\nMy question is about the UUID data type in Postgres.\nI am using an UUIDv4 uuid to indentify a record in multiple tables, so the request to \/users\/2df2ab0c-bf4c-4eb5-9119-c37aa6c6b172 will respond with the user that has that UUID. I also have an auto increment ID field for indexing.\nMy query is just a select with a where clause on UUID. But when the user enters an invalid UUID like this 2df2ab0c-bf4c-4eb5-9119-c37aa6c6b17 (without the last 2) then the database responds with this error: Invalid input syntax for UUID.\nI was wondering why it returned this because when you select on a integer-type with a string-type it does work.\nNow I need to set a middleware\/check on each route that has an UUID-type parameter in it because otherwise the server would crash.\nBtw I'm using Flask 0.12 (Python) and PostgreSQL 9.6","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1782,"Q_Id":42096970,"Users Score":0,"Answer":"The database is throwing an error because you're trying to match in a UUID-type column with a query that doesn't contain a valid UUID.  This doesn't happen with integer or string queries because leaving off the last character of those does result in a valid integer or string, just not the one you probably intended.\nYou can either prevent passing invalid UUIDs to the database by validating your input (which you should be doing anyway for other reasons) or somehow trap on this error.  Either way, you'll need to present a human-readable error message back to the user.\nAlso consider whether users should be typing in URLs with UUIDs in the first place, which isn't very user-friendly; if they're just clicking links rather than typing them, as usually happens, then how did that error even happen?  There's a good chance that it's an attack of some sort, and you should respond accordingly.","Q_Score":0,"Tags":"python,postgresql,uuid","A_Id":51623094,"CreationDate":"2017-02-07T18:11:00.000","Title":"PostgreSQL UUID date type","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am making a database with data in it.  That database has two customers: 1) a .NET webserver that makes the data visible to users somehow someway. 2) a python dataminer that creates the data and populates the tables.\nI have several options. I can use the .NET Entity Framework to create the database, then reverse engineer it on the python side.  I can vice versa that.  I can just write raw SQL statements in one or the other systems, or both.  What are possible pitfalls of doing this one way or the other?  I'm worried, for example, that if I use the python ORM to create the tables, then I'm going to have a hard time in the .NET space...","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":79,"Q_Id":42144698,"Users Score":0,"Answer":"I love questions like that.\nHere is what you have to consider, your web site has to be fast, and the bottleneck of most web sites is a database. The answer to your question would be - make it easy for .NET to work with SQL. That will require little more work with python, like specifying names of the table, maybe row names. I think Django and SQLAlchemy are both good for that. \nAnother solution could be to have a bridge between database with gathered data and database to display data. On a background you can have a task\/job to migrate collected data to your main database. That is also an option and will make your job easier, at least all database-specific and strange code will go to the third component.\nI've been working with .NET for quite a long time before I switched to python, and what you should know is that whatever strategy you chose it will be possible to work with data in both languages and ORMs. Do the hardest part of the job in the language your know better. If you are a Python developer - pick python to mess with the right names of tables and rows.","Q_Score":0,"Tags":"python,.net,database,orm","A_Id":42144831,"CreationDate":"2017-02-09T18:53:00.000","Title":"Sharing an ORM between languages","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am trying to enter about 1 millions records to PostgreSql since I create table dynamically I don't have any models associated with it so I cant perform bulk_insert of django\nHow is there any method of inserting data in a efficient manner.\nI am trying using single insert statement but this is very time consuming and too slow","AnswerCount":1,"Available Count":1,"Score":-0.1973753202,"is_accepted":false,"ViewCount":311,"Q_Id":42153732,"Users Score":-1,"Answer":"Your problem is not about django. You better carry the data(not necesarry but could be good) to the server that you want to insert and create a simple python program or sth. else to insert the data.\nAvoid to insert a data at this size by using an http server.","Q_Score":1,"Tags":"python,django,postgresql","A_Id":42154977,"CreationDate":"2017-02-10T07:24:00.000","Title":"Insert bulk data django using raw query","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have created a table in MySQL command line and I'm able to interact with it using python really well. However, I wanted to be able to change values in the table more easily so I installed MySQL workbench to do so. \nI have been able to connect to my server but when I try to change any values after selecting a table, it doesn't let me edit it. I tried making a new table within MySQL Workbench and I could edit it then. \nSo, I started to use that table. However, trying to edit the table python stopped working, so I made another table with command line again and it works! \nDoes anyone know how to fix either of these problems? It seems MySQL Workbench can only edit tables that have been created with Workbench, and not with Command Line. There must be a configuration option somewhere that is limiting this. \nThanks in advance!","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":94,"Q_Id":42211463,"Users Score":0,"Answer":"Editing a table means to be able to write back data in a way that reliably addresses the records that have changed. In MySQL Workbench there are certain conditions which must be met to make this possible. A result set:\n\nmust have a primary key\nmust not have any aggregates or unions\nmust not contain subselects\n\nWhen you do updates in a script you have usually more freedom by writing a WHERE clause that limits changes to a concrete record.","Q_Score":0,"Tags":"python,mysql,mysql-workbench","A_Id":42220939,"CreationDate":"2017-02-13T18:55:00.000","Title":"MySQL Workbench can't edit a table that was created using Command Line","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a python script (on my local machine) that queries Postgres database and updates a Google sheet via sheets API. I want the python script to run on opening the sheet. I am aware of Google Apps Script, but not quite sure how can I use it, to achieve what I want.\nThanks","AnswerCount":2,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":6619,"Q_Id":42218932,"Users Score":2,"Answer":"you will need several changes. first you need to move the script to the cloud (see google compute engine) and be able to access your databases from there.\nthen, from apps script look at the onOpen trigger. from there you can urlFetchApp to your python server to start the work.\nyou could also add a custom \"refresh\" menu to the sheet to call your server which is nicer than having to reload the sheet.\nnote that onOpen runs server side on google thus its impossible for it to access your local machine files.","Q_Score":0,"Tags":"python,google-apps-script,google-sheets,google-spreadsheet-api","A_Id":42327384,"CreationDate":"2017-02-14T06:00:00.000","Title":"Running python script from Google Apps script","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Now the question is a little tricky.... I have 2 tables that i want to compare them for their content. The tables have same no. of columns and same column names and same ordering of columns(if there is such thing). \nNow i want to compare their contents but the trick is the ordering of their rows can be different ,i.e., row no. 1 in table 1 can be present in row no. 1000 in table 2. I want to compare their contents such that the ordering of the rows don't matter. And also remember that their is no such thing as primary key. \nNow i can use and design Data structures or i can use an existing library to do the job. I want to use some existing APIs (if any). So can any1 point me in the right direction??","AnswerCount":3,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":1752,"Q_Id":42227567,"Users Score":0,"Answer":"You'd need to be more precise on how you intend to compare the tables' content and what is the expected outcome. Sqlite3 itself is a good tool for comparison and you can easily query the comparison results you wish to get.\nIf these tables however are located in different databases, you can dump them into temporary db using python's sqlite3 bulit-in module. \nYou can also dump the query results into a data collection such as list and then perform your comparison but then again we can't help you if we don't know the expected outcome.","Q_Score":0,"Tags":"python,database,sqlite","A_Id":42227865,"CreationDate":"2017-02-14T13:34:00.000","Title":"Comparing two sqlite3 tables using python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Now the question is a little tricky.... I have 2 tables that i want to compare them for their content. The tables have same no. of columns and same column names and same ordering of columns(if there is such thing). \nNow i want to compare their contents but the trick is the ordering of their rows can be different ,i.e., row no. 1 in table 1 can be present in row no. 1000 in table 2. I want to compare their contents such that the ordering of the rows don't matter. And also remember that their is no such thing as primary key. \nNow i can use and design Data structures or i can use an existing library to do the job. I want to use some existing APIs (if any). So can any1 point me in the right direction??","AnswerCount":3,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":1752,"Q_Id":42227567,"Users Score":0,"Answer":"You say \"there is no PRIMARY KEY\".  Does this mean there is truly no way to establish the identity of the item represented by each row?  If that is true, your problem is insoluble since you can never determine which row in one table to compare with each row in the other table.\nIf there is a set of columns that establish identity, then you would read each row from table 1, read the row with the same identity from table 2, and compare the non-identity columns.  If you find all the table 1 rows in table 2, and the non-identity columns are identical, then you finish up with a check for table 2 rows with identities that are not in table 1.\nIf there is no identity and if you don't care about identity, but just whether the two tables would appear identical, then you would read the records from each table sorted in some particular order.  Compare row 1 to row 1, row 2 to row 2, etc.  When you hit a row that's different, you know the tables are not the same.  \nAs a shortcut, you could just use SQLite to dump the data into two text files (again, ordered the same way for both tables) and compare the file contents.\nYou may need to include all the columns in your ORDER BY clause if there is not a subset of columns that guarantee a unique sort order.  (If there is such a subset of columns, then those columns would constitute the identity for the rows and you would use the above algorithm).","Q_Score":0,"Tags":"python,database,sqlite","A_Id":42228061,"CreationDate":"2017-02-14T13:34:00.000","Title":"Comparing two sqlite3 tables using python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am trying to move an Excel sheet say of index 5 to the position of index 0. Right now I have a working solution that copies the entire sheet and writes it into a new sheet created at the index 0, and then deletes the original sheet. \nI was wondering if there is another method that could push a sheet of any index to the start of the workbook without all the need of copy, create and write.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":2015,"Q_Id":42243861,"Users Score":0,"Answer":"Maybe the function from XLRD module can help you\nwhere you can get the sheet contents by index like this:\nworksheet = workbook.sheet_by_index(5)\nand then you can copy that into some other sheet of a different index, like this:\nworkbook.sheet_by_index(0) = worksheet","Q_Score":0,"Tags":"python,excel","A_Id":42244164,"CreationDate":"2017-02-15T08:12:00.000","Title":"Python - Change the sheet index in excel workbook","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I want to import and use dataset package of python at AWS Lambda. The dataset package is about MySQL connection and executing queries. But, when I try to import it, there is an error.\n\"libmysqlclient.so.18: cannot open shared object file: No such file or directory\"\nI think that the problem is because MySQL client package is necessary. But, there is no MySQL package in the machine of AWS Lambda.\nHow to add the third party program and how to link that?","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":131,"Q_Id":42267553,"Users Score":0,"Answer":"You should install your packages in your lambda folder :\n$ pip install YOUR_MODULE -t YOUR_LAMBDA_FOLDER \nAnd then, compress your whole directory in a zip to upload in you lambda.","Q_Score":1,"Tags":"mysql,python-2.7,amazon-web-services,aws-lambda","A_Id":42268813,"CreationDate":"2017-02-16T07:30:00.000","Title":"How to use the package written by another language in AWS Lambda?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I noticed that most examples for accessing mysql from flask suggest using a plugin that calls init_app(app).\nI was just wondering why that is as opposed to just using a mysql connector somewhere in your code as you need it?\nIs it that flask does better resource management with request life cycles?","AnswerCount":1,"Available Count":1,"Score":0.537049567,"is_accepted":false,"ViewCount":100,"Q_Id":42281212,"Users Score":3,"Answer":"Using packages like flask-mysql or Flask-SQLAlchemy, they provided useful defaults and extra helpers that make it easier to accomplish common CRUD tasks.\nAll of such package are good at handling relationships between objects. You only need to create the objects and then the objects contain all the functions and helpers you needed to deal with the database, you don't have to implement such code by yourself and you don't need to worry about the performance of the queries.\nI had worked on a Django project\uff08I believe the theory in Flask is similar\uff09 and its ORM is really amazing, all i need to do is writing Models and encapsulate business logic. All CRUD commands are handled by the built-in ORM, as a developer we don't worry about the SQL statements.\nAnother benefit is that it makes database migration much easier. You can switch it from MySQL to PostgresSQL with minimal code modifications which will speed up development.","Q_Score":1,"Tags":"python,mysql,flask","A_Id":42281576,"CreationDate":"2017-02-16T17:48:00.000","Title":"accessing mysql from within flask","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm having a trouble updating a model in odoo \nthe tables of my module won't change when I make changes to the model, even when I restart the server, upgrade the module, delete the module and reinstall it\nis there a way to make the database synchronized with my model?","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":1475,"Q_Id":42354852,"Users Score":0,"Answer":"Please check that in addons path there is no any duplicate folder having same name. Sometimes if there is zip file with same name in addons path than it doesn't get affect of any updation.","Q_Score":0,"Tags":"python,ubuntu,module,openerp,odoo-10","A_Id":42359847,"CreationDate":"2017-02-20T21:50:00.000","Title":"Updating a module's model in Odoo 10","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm having a trouble updating a model in odoo \nthe tables of my module won't change when I make changes to the model, even when I restart the server, upgrade the module, delete the module and reinstall it\nis there a way to make the database synchronized with my model?","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":1475,"Q_Id":42354852,"Users Score":0,"Answer":"If you save changes to the module, restart the server, and upgrade the module - all changes should be applied.\nChanges to tables (e.g. fields) should only require the module to be upgraded, not a server reboot.\nPython changes (e.g. contents of a method) require a server restart, not a module upgrade.\nIf the changes are not occurring, then it is possible that you have a different problem. I would look at things like: are you looking at the correct database\/tables, are you saving your changes, are the changes being made to the correct files\/in the correct locations.","Q_Score":0,"Tags":"python,ubuntu,module,openerp,odoo-10","A_Id":42359793,"CreationDate":"2017-02-20T21:50:00.000","Title":"Updating a module's model in Odoo 10","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I want to isolate my LAMP installment into a virtual environment, I tried using virtualbox but my 4GB of RAM is not helping. My question is if I run sudo apt-get install lamp-server^ while in \"venv\"... would it install the mysql-server, apache2 and PHP into the virtualenv only or is the installation scope system-wide.\nI really want a good solution for isolating these dev environments and their dependencies, and am hence exploring simple and efficient options given my system constraints. I have another Django (and mysql and gcloud) solution on the same computer and would like for these new installations to not mess with this.\nI'm using:\nOS: Ubuntu 16.04 LTS\nPython: 2.7","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":708,"Q_Id":42356276,"Users Score":1,"Answer":"Read about Docker if You want make separate environments without virtual machine.","Q_Score":1,"Tags":"php,python,mysql,virtualenv,lamp","A_Id":42356311,"CreationDate":"2017-02-20T23:53:00.000","Title":"Install LAMP Stack into Virtual Environment","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm working on a Project with python and openpyxl.\nIn a Excel file are some cells with conditional formatting. These change the infillcolor, when the value changes. I need to extract the color from the cell. \nThe \"normal\" methode\nworksheet[\"F11\"].fill.start_color.index\ndoesn't work. Excel doesn't interpret the infillcolor from the conditional formatting as infillcolor so i get a '00000000' back for no infill.\nAnyone knows how to get the infillcolor?\nThanks!","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":496,"Q_Id":42372121,"Users Score":1,"Answer":"This isn't possible without you writing some of your own code.\nTo do this you will have to write code that can evaluate conditional formatting because openpyxl is a library for the file format and not a replacement for an application like Excel.","Q_Score":2,"Tags":"python-3.x,spyder,openpyxl","A_Id":42372863,"CreationDate":"2017-02-21T15:58:00.000","Title":"Python\/openpyxl get conditional format","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a google drive folder with hundreds of workbooks. I want to cycle through the list and update data. For some reason, gspread can only open certain workbooks but not others. I only recently had this problem. \nIt's not an access issue because everything is in the same folder. \nI get raise SpreadsheetNotFound when I open_by_key(key). But then when I take the key and paste it into an URL, the sheet opens. Which means it's not the key.\nWhat's going on here? I'm surprised other people are not encountering this error.\nHave I hit my limit on the number of Google sheets I can have? I have about 2 thousand.\nUpdate: I find that if I go into the workbook and poke around, the sheet is then recognized??!! What does this mean? It doesn't recognize the sheet if the sheet isn't recently active???\nAlso if I try using Google App Script SpreadsheetApp.openById, the key is recognized! So the sheet is there, I just can't open it with gspread. I have use Google script to write something to the sheet first before it is recognized by gspread.\nI'm able to open the sheet using pygsheets but since it is new and so buggy, i can't use it. It looks like a APIv4 issue? Some sheets can't be opened with APIv3?\nupdate: here is another observation. Once you open the workbook with APIv4, you can no longer open it with V3.","AnswerCount":3,"Available Count":1,"Score":0.2605204458,"is_accepted":false,"ViewCount":3398,"Q_Id":42382847,"Users Score":4,"Answer":"I've run into this issue repeatedly. The only consistent fix I've found is to \"re-share\" the file with the api user. It already lists the api user as shared (since it's in the same shared folder as everything else), but after \"re-sharing\" I can connect with gspread no problem. \nBased on this I believe it may actually be a permissions issue (Google failing to register the correct permission for the API user when accessing it through APIv3).","Q_Score":12,"Tags":"python,google-sheets,gspread","A_Id":42867483,"CreationDate":"2017-02-22T04:40:00.000","Title":"gspread \"SpreadsheetNotFound\" on certain workbooks","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm embarking on a software project, and I have a bit of an idea on how to attack it, but would really appreciate some general tips, advice or guidance on getting the task done. Project is as follows:\nMy company has an ERP (Enterprise Resource Planning) system that we use to record all our business activity (i.e. create purchase orders, receive shipments, create sales orders, manage inventory etc..). All this activity is data entry into the ERP system that gets stored in a SQL Server database.  \nI would like to push this activity to certain Slack channels via text messages.\nFor example, when the shipping department creates a 'receipt entry' (they receiving in a package) in the ERP system, then production team would get a text saying 'item X has been received in' in their Slack channel.\nMy current napkin sketch is this:\nFor a given business activity, create a function that executes a SQL query to return the most recent data entry.\nStore this in my own external database. \nRoutinely execute these calls (Maybe create a Windows scheduler to execute a program that runs through all the functions every 30 minutes or so??), which will compare the data from the query to the data last saved in my external database. \nIf the same, do nothing. But if they're different:\nReplace the data from my external database with this new data, then use Slacks API to post a message of this new data to Slack.\nI'm not too certain about the mechanics of executing a program to check for new activity in the ERP system, and also uncertain about using a second database as a means of remembering what was sent to Slack previously. Any advice would be greatly appreciated.\nThanks!\nJosh","AnswerCount":2,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":192,"Q_Id":42394615,"Users Score":2,"Answer":"Epicor ERP has a powerful extension system built in. \nI would create a Business Process Method (BPM) for ReceiptEntry.Update. This wouldn't check for added rows but more specifically where the Recieved flag has been changed to set. This will prevent you getting multiple notifications every time a user saves an incomplete record. \nIn the BPM you can reference external assemblies and call the Slack APIs from there. \nI strongly recommend you avoid trying to do this at the database level instead of the application level. The schema can change and it is much harder to maintain the system if someone has been adding code to the database. If it isn't done carefully it can break the Data Model Regeneration in the Epicor Administration Console and prevent you from adding UD fields or upgrading your database.","Q_Score":1,"Tags":"python,sql,architecture,slack-api,epicorerp","A_Id":42415248,"CreationDate":"2017-02-22T14:43:00.000","Title":"Project Advice: push ERP\/SQL transaction data to Slack","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I generally use Pandas to extract data from MySQL into a dataframe. This works well and allows me to manipulate the data before analysis. This workflow works well for me.\nI'm in a situation where I have a large MySQL database (multiple tables that will yield several million rows). I want to extract the data where one of the columns matches a value in a Pandas series. This series could be of variable length and may change frequently. How can I extract data from the MySQL database where one of the columns of data is found in the Pandas series? The two options I've explored are:\n\nExtract all the data from MySQL into a Pandas dataframe (using pymysql, for example) and then keep only the rows I need (using df.isin()).\n\nor\n\nQuery the MySQL database using a query with multiple WHERE ... OR ... OR statements (and load this into Pandas dataframe). This query could be generated using Python to join items of a list with ORs.\n\nI guess both these methods would work but they both seem to have high overheads. Method 1 downloads a lot of unnecessary data (which could be slow and is, perhaps, a higher security risk) whilst method 2 downloads only the desired records but it requires an unwieldy query that contains potentially thousands of OR statements.\nIs there a better alternative? If not, which of the two above would be preferred?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":352,"Q_Id":42405493,"Users Score":0,"Answer":"I am not familiar with pandas but strictly speaking from a database point of view you could just have your panda values inserted in a PANDA_VALUES table and then join that PANDA_VALUES table with the table(s) you want to grab your data from.\nAssuming you will have some indexes in place on both PANDA_VALUES table and the table with your column the JOIN would be quite fast.\nOf course you will have to have a process in place to keep PANDA_VALUES tables updated as the business needs change.\nHope it helps.","Q_Score":0,"Tags":"python,mysql,sql,python-3.x,pandas","A_Id":42406043,"CreationDate":"2017-02-23T01:36:00.000","Title":"Selecting data from large MySQL database where value of one column is found in a large list of values","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have about the 3GB 4-5 table in google bigquery and I want to export these table to Postgres. Reading the docs I found I have to do following steps.\n\ncreate a job that will extract data to CSV in the google bucket.\nFrom google storage to local storage.\nParse all CSV to database\n\nSo in the above step is there any efficient way to do all this. I know that step 1 and 2 can't skip no chance of efficiency but in step 3 from reading online, i found that it will take 2-3 hours to do this process.\nCan anyone suggest me an efficient way to do this","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":691,"Q_Id":42443016,"Users Score":0,"Answer":"Make an example project and see what times you get, if you can accept those times it's too early to optimize. I see all this is possible in about 3-5 minutes if you have 1Gbit internet access and server running on SSD.","Q_Score":1,"Tags":"python,postgresql,google-bigquery","A_Id":42454600,"CreationDate":"2017-02-24T15:58:00.000","Title":"Dump Data from bigquery to postgresql","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have an instance of an object (with many attributes) which I want to duplicate.\nI copy it using deepcopy() then modify couple of attributes.\nThen I save my new object to the database using Python \/ PeeWee save() but the save() actually updates the original object (I assume it is because that the id was copied from the original object).\n(btw no primary key is defined in the object model)\nHow do I force save the new object? can I change its id?\nThanks.","AnswerCount":2,"Available Count":1,"Score":0.3799489623,"is_accepted":false,"ViewCount":1374,"Q_Id":42449783,"Users Score":4,"Answer":"Turns out that I can set the id to None (obj.id = None) which will create a new record when performing save().","Q_Score":2,"Tags":"python,mysql,peewee","A_Id":42451623,"CreationDate":"2017-02-24T23:06:00.000","Title":"Copy object instance and insert to DB using peewee creates duplicate ID","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm starting my Python journey with a particular project in mind;\nThe title explains what I'm trying to do (make json api calls with python3.6 and sqlite3). I'm working on a mac.\nMy question is whether or not this setup is possible? Or if I should use MySQL, PostgreSQL or MongoDB?\nIf it is possible, am I going to have to use any 3rd party software to make it run?\nSorry if this is off topic, I'm new to SO and I've been trying to research this via google and so far no such luck. \nThank you in advance for any help you can provide.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":451,"Q_Id":42489060,"Users Score":1,"Answer":"Python 3.6 and sqlite both work on a Mac; whether your json api calls will depends on what service you are trying to make calls to (unless you are writing a server that services such calls, in which case you are fine).\nAny further recommendations are either a) off topic for SO or b) dependent on what you want to do with these technologies.","Q_Score":1,"Tags":"python-3.x,sqlite,json-api","A_Id":42489154,"CreationDate":"2017-02-27T15:06:00.000","Title":"Python3 & SQLite3 JSON api calls","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"Could someone give me an example of using whoosh for a sqlite3 database, I want to index my database. Just a simple connect and searching through the database would be great. I searched online and was not able to find an examples for sqlite3.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":466,"Q_Id":42493984,"Users Score":0,"Answer":"You need to add a post-save function index_data to your database writers. This post-save should get the data to be written in database, normalize it and index it.\nThe searcher could be an independent script given an index and queries to be searched for.","Q_Score":3,"Tags":"python,python-2.7,indexing,sqlite,whoosh","A_Id":51001220,"CreationDate":"2017-02-27T19:16:00.000","Title":"Using Whoosh with a SQLITE3.db (Python)","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"How to remove and add completly new db.sqlite3 database to django project written in pycharm?\nI did something wrong and I need completelty new database. The 'flush' command just removes data from databse but it't dosent remove tables schema. So the question is how to get get back my databse to begin point(no data, no sql table)","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1356,"Q_Id":42514902,"Users Score":4,"Answer":"A SQLite database is just a file. To drop the database, simply remove the file.\nWhen using SQLite, python manage.py migrate will automatically create the database if it doesn't exist.","Q_Score":1,"Tags":"python,sql,django","A_Id":42515036,"CreationDate":"2017-02-28T17:14:00.000","Title":"How to remove and add completly new db.sqlite3 to django project written in pycharm?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"The ping service that I have in mind allows users to keep easily track of their cloud application (AWS, GCP, Digital Ocean, etc.) up-time. \nThe part of the application's design that I am having trouble with is how to effectively read a growing\/shrinking list of hostnames from a database and ping them every \"x\" interval. The service itself will be written in Python and Postgres to store the user-inputted hostnames. Keep in mind that the list of hostnames to ping is variable since a user can add and also remove hostnames at will. \nHow would you setup a system that checks for the most up-to-date list of hostnames, executes pings across said list of hostnames, and store the results, at a specific interval?\nI am pretty new to programming. Any help or pointers in the right direction will be greatly appreciated","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":45,"Q_Id":42524336,"Users Score":0,"Answer":"Let me put it like this. You will be having these 4 statements in the following way. In the simplest way you could keep a table of users and a table of hostnames which will have following columns -> fk to users, hostname, last update and boolean is_running.\nYou will need the following actions.\nUPDATE:\nYou will run this periodically on the whole table. You could optimize this by using a select with a filter on the last update column.\nINSERT and DELETE:\nThis is for when the user adds or removes hostnames. During inserting also ping the hostname and update the last update column as the current time.\nFor the above 3 operations whenever they run they'd be using a lock on the respective rows. After each of the latter 2 operations you could notify the user.\nFinally the READ:\nThis is whenever the user wants to see the status of his hostnames. If he has added or removed a hostname recently he will be notified only after the commit.\nOtherwise do a select * from hostnames where user.id = x and send him the result. Everytime he hits refresh you could run this query.\nYou could also put indices on both the tables as the read operation is the one that has to be fastest. You could afford slightly slower times on the other 2 operations.\nDo let me know if this works or if you've done differently. Thank you.","Q_Score":1,"Tags":"python,architecture","A_Id":42525826,"CreationDate":"2017-03-01T06:01:00.000","Title":"Designing a pinging service","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":0},{"Question":"I'm working with sqlalchemy and oracle, but I don't want to store the database password directly in the connection string, how to store a encrypted password instead?","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":3865,"Q_Id":42776941,"Users Score":0,"Answer":"Encrypting the password isn't necessarily very useful, since your code will have to contains the means to decrypt.  Usually what you want to do is to store the credentials separately from the codebase, and have the application read them at runtime.  For example*:\n\nread them from a file\nread them from command line arguments or environment variables (note there are operating system commands that can retrieve these values from a running process, or they may be logged)\nuse a password-less connection mechanism, for example Unix domain sockets, if available\nfetch them from a dedicated secrets management system\n\nYou may also wish to consider encrypting the connections to the database, so that the password isn't exposed in transit across the network.\n\n* I'm not a security engineer: these examples are not exhaustive and may have other vulnerabilities in addition to those mentioned.","Q_Score":2,"Tags":"python,oracle,sqlalchemy","A_Id":70789442,"CreationDate":"2017-03-14T02:53:00.000","Title":"How to use encrypted password in connection string of sqlalchemy?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"in aws cli we can set output format as json or table. Now I can get json output from json.dumps is there anyway could achieve output in table format? \nI tried pretty table but no success","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":980,"Q_Id":42787327,"Users Score":1,"Answer":"Python Boto3 does not return the data in the tabular format. You will need to parse the data and use another python lib to output the data in the tabular format . Pretty table works good for me, read the pretty table lib docs and debug your code.","Q_Score":0,"Tags":"json,python-2.7,boto3,aws-cli,prettytable","A_Id":42952740,"CreationDate":"2017-03-14T13:27:00.000","Title":"Is it possible to get Boto3 | python output in tabular format","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":1,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have an .ods file that contains many links that must be updated automatically. As I understand there is no easy way to do this with macros or libreoffice command arguments, so I am trying to make all links update upon opening the file and then will save the file and exit. \nAll links are DDE links which should be able to update automatically (and are set to do so in Edit > Links), and I have also enabled this in Tools > Options > Calc > General > Always Update Links When Opening, as well as Tools > Options > Calc > Formulas > Always Recalculate. However, I am still being prompted with a popup to manually update links upon opening, and links will not be up to date if I do not select Update. I need these DDE links to update automatically, why isn't this working? \nIf there is no solution there, I am also willing to try to update links via Python. Will Uno work with libreoffice to do this without ruining any preexisting graphs in the file like openpyxl does?","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":986,"Q_Id":42788839,"Users Score":0,"Answer":"The API does not provide a method to suppress the prompt upon opening the file!\nI've tried running StarBasic code to update DDE links on \"document open\" event, but the question keeps popping up.\nSo, I guess you're out of luck: you have to answer \"Yes\" if you want the actual values.\n[posted the comment to OP's question here again as answer, as suggested by @Jim K]","Q_Score":0,"Tags":"python,libreoffice,dde","A_Id":42806325,"CreationDate":"2017-03-14T14:34:00.000","Title":"Libreoffice - update links automatically upon opening?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm attempting to access a Google Cloud SQL instance stored on one Cloud Platform project from an App Engine application on another project, and it's not working.\nConnections to the SQL instance fail with this error:\nOperationalError: (2013, \"Lost connection to MySQL server at 'reading initial communication packet', system error: 38\")\nI followed the instructions in Google's documentation and added the App Engine service account for the second project to the IAM permissions list for the project housing the Cloud SQL instance (with \"Cloud SQL Editor\" as the role). The connection details and configuration I'm using in my app are identical to those being used in a perfectly functioning App Engine app housed in the same project as the Cloud SQL instance.\nThe only thing that seems off about my configuration is that in my second GCP project, while an App Engine service account that looks like the default one ([MY-PROJECT-NAME]@appspot.gserviceaccount.com) appears in the IAM permissions list, this service account is not listed under the Service Accounts tab of IAM & Admin. The only service account listed is the Compute Engine default service account. I haven't deleted any service accounts; there's never been an App Engine default service account listed here, but apart from the MySQL connection the App Engine app runs fine.\nNot sure if it's relevant, but I'm running a Python 2.7 app on the App Engine Standard Environment, connecting using MySQLdb.","AnswerCount":1,"Available Count":1,"Score":1.0,"is_accepted":false,"ViewCount":3103,"Q_Id":42826560,"Users Score":6,"Answer":"Figured it out eventually - perhaps this will be useful to someone else encountering the same problem. \nProblem:\n\nThe problem was that the \"Cloud SQL Editor\" role is not a superset\n  of the \"Cloud SQL Client\", as I had imagined; \"Cloud SQL Editor\"\n  allows administration of the Cloud SQL instance, but doesn't allow\n  basic connectivity to the database.\n\nSolution:\n\nDeleting the IAM entry granting Cloud SQL Editor permissions and\n  replacing it with one granting Cloud SQL Client permissions fixed the\n  issue and allowed the database connection to go through.","Q_Score":3,"Tags":"python,mysql,google-app-engine,google-cloud-sql","A_Id":42827972,"CreationDate":"2017-03-16T06:14:00.000","Title":"Can't access Google Cloud SQL instance from different GCP project, despite setting IAM permissions","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"How to achieve a read-only connection to the secondary nodes of the MongoDB.\nI have a primary node and two secondary nodes. I want a read-only connection to secondary nodes. \nI tried MongoReplicaSetClient but did not get what I wanted.\nIs it possible to have a read-only connection to primary node?","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":1793,"Q_Id":42849056,"Users Score":1,"Answer":"Secondaries are read-only by default. However, you can specify the read preference to read from secondaries. By default, it reads from the primary.\nThis can be achieved using readPreference=secondary in connection string","Q_Score":1,"Tags":"python,mongodb,pymongo","A_Id":42850060,"CreationDate":"2017-03-17T04:06:00.000","Title":"How to achieve a read only connection using pymongo","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I understand you can do DELETE FROM table WHERE condition, but I was wondering if there was a more elegant way? Since I'm iterating over every row with c.execute('SELECT * FROM {tn}'.format(tn=table_name1)), the cursor is already on the row I want to delete.","AnswerCount":1,"Available Count":1,"Score":0.3799489623,"is_accepted":false,"ViewCount":346,"Q_Id":42888269,"Users Score":2,"Answer":"A cursor is a read-only object, and cursor rows are not necessarily related to table rows. So this is not possible.\nAnd you must not change the table while iterating over it.\nSQLite computes result rows on demand, so deleting the current row could break the computation of the next row.","Q_Score":0,"Tags":"python,python-3.x,sqlite,sql-delete,delete-row","A_Id":42889578,"CreationDate":"2017-03-19T15:16:00.000","Title":"While iterating over the rows in an SQLite table, is it possible to delete the cursor's row?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I need help with the pyodbc Python module. I installed it via Canopy package management, but when I try to import it, I get an error (no module named pyodbc). Why?\nHere's the output from my Python interpreter:\n\n\n\nimport pyodbc\n      Traceback (most recent call last):\n        File \"\", line 1, in \n          import pyodbc\n      ImportError: No module named 'pyodbc","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":62,"Q_Id":42935980,"Users Score":0,"Answer":"For the record: the attempted import was in a different Python installation. It is never good, and usually impossible, to use a package which was installed into one Python installation, in another Python installation.","Q_Score":0,"Tags":"python,pyodbc,canopy","A_Id":42963908,"CreationDate":"2017-03-21T19:00:00.000","Title":"No Module After Install Package via Canopy Package Management","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I downloaded the pyodbc module as a zip and installed it manually using the command python setup.py install. Although I can find the folder inside the Python directory which I pasted, while importing I am getting the error:\nImportError: No module named pyodbc\nI am trying to use to this to connect with MS SQL Server. Help","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":8261,"Q_Id":42944116,"Users Score":0,"Answer":"As installation error showed, installing Visual C++ 9.0 solves problem because setup.py tries to compile some C++ libraries while installing plugin. I thing Cygwin C++ will also work due to contents of setup.py.","Q_Score":1,"Tags":"python,sql-server,database-connection,pyodbc","A_Id":42947078,"CreationDate":"2017-03-22T06:20:00.000","Title":"ImportError: No module named pyodbc","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am trying to generate a flask-sqlalchemy for an existing mysql db.\nI used the following command\nflask-sqlacodegen --outfile rcdb.py mysql:\/\/username:password@hostname\/tablename\nThe project uses python 3.4. Any clues?\n```Traceback (most recent call last):\nFile \"\/var\/www\/devaccess\/py_api\/ds\/venv\/bin\/flask-sqlacodegen\", line 11, in \nsys.exit(main())\nFile \"\/var\/www\/devaccess\/py_api\/ds\/venv\/lib\/python3.4\/site-packages\/sqlacodegen\/main.py\", line 59, in main\nTraceback (most recent call last):\nFile \"\/var\/www\/devaccess\/py_api\/ds\/venv\/bin\/flask-sqlacodegen\", line 11, in \nsys.exit(main())\nFile \"\/var\/www\/devaccess\/py_api\/ds\/venv\/lib\/python3.4\/site-packages\/sqlacodegen\/main.py\", line 59, in main\nargs.flask, ignore_cols, args.noclasses)\nFile \"\/var\/www\/devaccess\/py_api\/ds\/venv\/lib\/python3.4\/site-packages\/sqlacodegen\/codegen.py\", line 606, in init\nmodel = ModelClass(table, links[table.name], inflect_engine, not nojoined)\nFile \"\/var\/www\/devaccess\/py_api\/ds\/venv\/lib\/python3.4\/site-packages\/sqlacodegen\/codegen.py\", line 335, in init\nrelationship_ = ManyToManyRelationship(self.name, target_cls, association_table, inflect_engine)\nFile \"\/var\/www\/devaccess\/py_api\/ds\/venv\/lib\/python3.4\/site-packages\/sqlacodegen\/codegen.py\", line 501, in init\nself.kwargs['secondary'] = repr(assocation_table.schema + '.' + assocation_table.name)\nTypeError: unsupported operand type(s) for +: 'NoneType' and 'str'\n```","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":362,"Q_Id":43008166,"Users Score":1,"Answer":"try specifying your database schema with option --schema","Q_Score":1,"Tags":"python-3.x,sqlalchemy,flask-sqlalchemy,sqlacodegen","A_Id":49161491,"CreationDate":"2017-03-24T20:00:00.000","Title":"flask-sqlacodegen suports python 3.4?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"What I want is that when I have looked up a user in a table, I want to list all the file urls that the user have access to. My first thought was to have a field in the table with a list of file URLs. However, I have now understood that there are no such field type. \nI was then thinking that maybe ForeignKeys might work, but I am having trouble getting my head around it. \nAnother solution maybe is to have one table for each user, with each row representing each file.\nWhat would you say is best practice in this case? \nI am also going to expand into having shared files, but thought that I'd address this issue first.","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":25,"Q_Id":43066877,"Users Score":0,"Answer":"2 tables: user and user_uri_permission? 2 columns in the second: userID and URI. When the User-URI pair is in the table the use has access.","Q_Score":0,"Tags":"mysql,mysql-python","A_Id":43179890,"CreationDate":"2017-03-28T10:18:00.000","Title":"Mapping users to all of their files(URLs) in a mysql database.","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a big-ol' dbm file, that's being created and used by my python program. It saves a good amount of RAM, but it's getting big,  and I suspect I'll have to gzip it soon to lower the footprint. \nI guess usage will involve un-gzipping it to the disk, using it, and erasing the extracted dbm when I'm done.\nI was wondering whether there perhaps exists some nice way of compressing the dbm and keep working with it somehow. In my spcific usecase, I only need to read from it.\nThanks.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":109,"Q_Id":43069291,"Users Score":0,"Answer":"You can gzip the value or use a key\/value store that support compression like wiredtiger.","Q_Score":1,"Tags":"python,compression,gzip,key-value-store,dbm","A_Id":43080032,"CreationDate":"2017-03-28T12:14:00.000","Title":"recipe for working with compressed (any)dbm files in python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"After updating PyCharm (version 2017.1), PyCharm does not display sqlite3 database tables anymore.\nI've tested the connection and it's working.\nIn sqlite client I can list all tables and make queries.\nSomeone else has get this problem? And in this case could solve anyway?","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":3401,"Q_Id":43075420,"Users Score":1,"Answer":"After clicking on the View => Tools => Window => Database click on the green plus icon and then on Data Source => Sqlite (Xerial). Then, on the window that opens install the driver (it's underneath the Test Connection button) that is proposing (Sqlite (Xerial)).\nThat should do it both for db.sqlite3 and identifier.sqlite. I have never any problem with Sqlite database, showing on PyCharm IDE.","Q_Score":2,"Tags":"python,django,sqlite,pycharm","A_Id":43075527,"CreationDate":"2017-03-28T16:50:00.000","Title":"Pycharm does not display database tables","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"So is it possible to mix 2 ORM's in same web app,and if so how optimal would it be ? Why so?\n- I'm working on a web app in flask using flask-mysqldb and I came to a point where I need to implement an auth system, and on flask-mysqldb there's no secure way to do it.\n- With that said now I'm trying to implement flask-security but it only works on flask-sqlalchemy so I'm trying to mix sqlalchemy with mysqldb and before that I want to know if it's optimal and if it works.That would lead to using user auth along sqlalchemy and other data to mysqldb.Thanks!","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":145,"Q_Id":43098668,"Users Score":1,"Answer":"It's possible, but not recommended. Consider this:\n\nHalf of your app will not benefit from anything a proper ORM offers\nAdding a field to the table means editing raw SQL in many places, and then changing the model.\nDon't forget to keep them in sync.\n\nAlternatively, you can port everything that uses raw mysqldb to use SQLAlchemy:\n\nNeed to add a field to your table? Just change the model in one place.\nDon't like SQL queries that ORM generates for you? You still have a low-level control over this.","Q_Score":0,"Tags":"python,flask,flask-sqlalchemy,flask-mysql","A_Id":43098951,"CreationDate":"2017-03-29T16:03:00.000","Title":"Is it possible to mix 2 ORMS in same web app?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"So is it possible to mix 2 ORM's in same web app,and if so how optimal would it be ? Why so?\n- I'm working on a web app in flask using flask-mysqldb and I came to a point where I need to implement an auth system, and on flask-mysqldb there's no secure way to do it.\n- With that said now I'm trying to implement flask-security but it only works on flask-sqlalchemy so I'm trying to mix sqlalchemy with mysqldb and before that I want to know if it's optimal and if it works.That would lead to using user auth along sqlalchemy and other data to mysqldb.Thanks!","AnswerCount":2,"Available Count":2,"Score":0.2913126125,"is_accepted":false,"ViewCount":145,"Q_Id":43098668,"Users Score":3,"Answer":"You can have a module for each orm. One module can be called auth_db and the other can be called data_db. In your main app file just import both modules and initialize the database connections. That being said, this approach will be harder to maintain in the future, and harder for other developers to understand what's going on. I'd recommend moving your flask-mysqldb code to sqlalchemy so that you are only using one ORM.","Q_Score":0,"Tags":"python,flask,flask-sqlalchemy,flask-mysql","A_Id":43098934,"CreationDate":"2017-03-29T16:03:00.000","Title":"Is it possible to mix 2 ORMS in same web app?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am thinking to use AWS API Gateway and AWS Lambda(Python) to create a serverless API's , but while designing this i was thinking of some aspects like pagination,security,caching,versioning ..etc \nso my question is: \nWhat is the best approach performance & cost wise to implement API pagination with very big data (1 million records)? \n\nshould i implement the pagination in postgresql db? (i think this\nwould be slow)\nshould i not use postgresql db pagination and just cache all the results i get from db into aws elastic cache and then do server side pagination in lambda.\n\nI appreciate your help guys.","AnswerCount":1,"Available Count":1,"Score":0.537049567,"is_accepted":false,"ViewCount":1679,"Q_Id":43113198,"Users Score":3,"Answer":"If your data is going to live in a postgresql data base anyway I would start with your requests hitting the database and profile the performance. You've made assumptions about it being slow but you haven't stated what your requirements for latency are or what your schema is, so any assertions people would make about whether or not it would fit your case is completely speculative.\nIf you do decide that after profiling that it is not fast enough, than adding a cache would make sense, though storing the entire contents in the cache seems wasteful unless you can guarantee your clients will always iterate through all results. You may want to consider a mechanism that prefetches blocks of data that would service a few requests rather than trying to cache the whole data.\nTL;DR : Don't prematurely optimize your solution. Quantify how you want your system to respond and test and validate your assumptions.","Q_Score":1,"Tags":"python,postgresql,amazon-web-services,aws-lambda,aws-api-gateway","A_Id":43126859,"CreationDate":"2017-03-30T09:04:00.000","Title":"AWS API Gateway & Lambda - API Pagination","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":1,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am working on a python\/tornado web application.\nI have several options to save in my app.\nThoses options can by changed by the user, and those options will be access very often.\nI have created an sqlite database but there is some disk operation and i am asking you what is the best location for those options.\nDoes tornado embed a feature for custom user options ?\nThanks","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":28,"Q_Id":43145705,"Users Score":0,"Answer":"Yes, there is the tornado.options package, which does pretty much what you need. Keep in mind, however, that the values saved here are not persisted between requests; if you need that kind of functionality, you will have to implement an external persistence solution, which you already have done with SQLite.","Q_Score":0,"Tags":"python,tornado","A_Id":43171572,"CreationDate":"2017-03-31T16:39:00.000","Title":"Where should i save my tornado custom options","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I have PhpMyAdmin to view and edit a database and a Flask + SQLAlchemy app that uses a table from this database. Everything is working fine and I can read\/write to the database from the flask app. However, If I make a change through phpmyadmin, this change is not detected by SQLAlchmey. The only to get those changes is by manually refreshing SQLAlchmey connection \nMy Question is how to tell SQLAlchemy to reload\/refresh its Database connection?","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":665,"Q_Id":43149092,"Users Score":0,"Answer":"I suggest you to look at Server Sent Events(SSE). I am looking for code of SSE for postgres,mysql,etc. It is available for reddis.","Q_Score":0,"Tags":"python,flask,sqlalchemy,flask-sqlalchemy","A_Id":43703427,"CreationDate":"2017-03-31T20:22:00.000","Title":"Flask App using SQLAlcehmy: How to detect external changes committed to the database?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Are there any solutions (preferably in Python) that can repair pdfs with damaged xref tables?\nI have a pdf that I tried to convert to a png in Ghostscript and received the following error:\n**** Error:  An error occurred while reading an XREF table.\n   **** The file has been damaged.  This may have been caused\n   **** by a problem while converting or transfering the file.\nHowever, I am able to open the pdf in Preview on my Mac and when I export the pdf using Preview, I am able to convert the exported pdf.\nIs there any way to repair pdfs without having to manually open them and export them?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":8136,"Q_Id":43149372,"Users Score":1,"Answer":"If the file renders as expected in Ghostscript then you can run it through GS to the pdfwrite device and create a new PDF file which won't be damaged.\nPreview is (like Acrobat) almost certainly silently repairing the problem in the background. Ghostscript will be doing the same, but unlike other applications we feel you need to know that the file has a problem. Firstly so that you know its broken, secondly so that if the file renders incorrectly in Ghostscript (or indeed, other applications) you know why.\nNote that there are two main reasons for a damaged xref; firstly the developer of the application didn't read the specification carefully enough and the file offsets in the xref are correct, but the format is incorrect (this is not uncommon and a repair by GS will be harmless), secondly the file genuinely has been damaged in transit, or by editing it.\nIn the latter case there may be other problems and Ghostscript will try to warn you about those too. If you don't get any other warnings or errors, then its probably just a malformed xref table.","Q_Score":6,"Tags":"python,pdf,ghostscript","A_Id":43154410,"CreationDate":"2017-03-31T20:42:00.000","Title":"Repairing pdfs with damaged xref table","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am directing this question to experienced, Django developers, so as in subject, I have been learning Django since September 2016, but I've started to learn it without any knowledge about databases syntax. I know basic concepts and definitions, so I can easily implement in Django models. Summarizing, have I to know SQL to create web apps in Django? Thanks in advance.","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":1361,"Q_Id":43161718,"Users Score":1,"Answer":"You do not have to be a wizard at it but understanding relations between data sets can be extremely helpful especially if you have a complicated data hierarchy. \nJust learn as you go. If you want you can look at the SQL code Django executes for you in the migrations.py file of each app.","Q_Score":1,"Tags":"python,sql,django","A_Id":43164854,"CreationDate":"2017-04-01T20:33:00.000","Title":"Do I need to know SQL when I work with Django","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm creating and writing into an excel file using xlsxwriter module. But when I open the excel file, I get this popup:\nWe found a problem with some content in 'excel_sheet.xlsx'. Do you want us to try to recover as much as we can? If you trust the source of this workbook, click Yes. If I click Yes, it says Repaired Records: String properties from \/xl\/sharedStrings.xml part (Strings) and then I can see the contents.\nI found that this occurs because of the cells I wrote using write_rich_string.\nmy_work_sheet.write_rich_string(row_no, col_no,format_1, \"Some text in format 1\", format_2, \"Text in format 2\", format_1, \"Again in format 1\")\nIf I write it using write_string this doesn't occur. format_1 and format_2 has font name, color, size and vertical align set.\nCan anyone suggest what goes wrong here?","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1256,"Q_Id":43199359,"Users Score":2,"Answer":"I was trying to recreate(Thanks to @jmcnamara) the problem and I could figure out where it went wrong.\nIn my command to write_rich_string, sometimes it was trying to format the empty string. \nmy_work_sheet.write_rich_string(row_no, col_no,format_1, string_1, format_2, string_2, format_1, string_3)\nI came to know that at some point of time the value of one among string_1, string_2 and string_3 becomes ''. Now I use write_rich_string only after ensuring they are not ''.","Q_Score":1,"Tags":"python-3.x,xlsxwriter","A_Id":43248203,"CreationDate":"2017-04-04T05:59:00.000","Title":"Python xlsxwriter Repaired Records: String properties from \/xl\/sharedStrings.xml part (Strings)","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"So basically I would like to be able to view two different databases within the same Grafana graph panel. The issue is that InfluxDB is a time series database, so it is not possible to see the trend between two databases in the same graph panel unless they have similar timestamps. The workaround is creating two panels in Grafana and adding a delay to one, but this doesn't give a good representation as the graphs are not on the same panel so it is more difficult to see the differences. I am currently working on a script to copy the databases in question and alter the timestamps so that the two newly created databases look like the data was taken at the same time. I am wondering if anyone has any idea how to change the timestamp, and if so, what would be the best way to to do so with a large amount of data points? Thanks.","AnswerCount":2,"Available Count":2,"Score":0.0996679946,"is_accepted":false,"ViewCount":569,"Q_Id":43215443,"Users Score":1,"Answer":"I believe this is currently available via kapacitor, but assume a more elegant solution will be readily accomplished using FluxQL. \nConsuming the influxdb measurements into kapacitor will allow you to force equivalent time buckets and present the data once normalized.","Q_Score":0,"Tags":"python,influxdb,grafana","A_Id":52570244,"CreationDate":"2017-04-04T18:55:00.000","Title":"InfluxDB and Grafana: comparing two databases with different timestamps on same graph panel","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"So basically I would like to be able to view two different databases within the same Grafana graph panel. The issue is that InfluxDB is a time series database, so it is not possible to see the trend between two databases in the same graph panel unless they have similar timestamps. The workaround is creating two panels in Grafana and adding a delay to one, but this doesn't give a good representation as the graphs are not on the same panel so it is more difficult to see the differences. I am currently working on a script to copy the databases in question and alter the timestamps so that the two newly created databases look like the data was taken at the same time. I am wondering if anyone has any idea how to change the timestamp, and if so, what would be the best way to to do so with a large amount of data points? Thanks.","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":569,"Q_Id":43215443,"Users Score":0,"Answer":"I can confirm from my grafana instance that it's not possible to add a shift to one timeseries and not the other in one panel.\nTo change the timestamp, I'd just simply do it the obvious way. Load a few thousands of entries at a time to python, change the the timestamps and write it to a new measure (and indicate the shift in the measurement name).","Q_Score":0,"Tags":"python,influxdb,grafana","A_Id":43306424,"CreationDate":"2017-04-04T18:55:00.000","Title":"InfluxDB and Grafana: comparing two databases with different timestamps on same graph panel","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Currently I am using celery to build a scheduled database synchronization feature, which periodically fetch data from multiple databases. If I want to store the task results, would the performance be better if I store them in Redis instead of a RDB like MySQL?","AnswerCount":1,"Available Count":1,"Score":0.3799489623,"is_accepted":false,"ViewCount":931,"Q_Id":43264701,"Users Score":2,"Answer":"Performance-wise it's probably going to be Redis but performance questions are almost always nuance based.\nRedis stores lists of data with no requirement for them to relate to one another so is extremely fast when you don't need to use SQL type queries against the data it contains.","Q_Score":2,"Tags":"python,mysql,django,redis,celery","A_Id":43264780,"CreationDate":"2017-04-06T19:57:00.000","Title":"Celery: Is it better to store task results in MySQL or Redis?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":0},{"Question":"I have a Django project with 5 different PostgreSQL databases.  The project was preemptively separated in terms of model routing, but has proven quite problematic so now I'm trying to reverse it.  Unfortunately, there's some overlap of empty, migrated tables so pg_dump's out of the question.  It looks like django-dumpdb may suit my needs but it doesn't handle per-database export\/import.  Additionally, Django's dumpdata\/loaddata are installing 0 of the records from generated fixtures.  Can I have some suggestions as to the least painful way to merge the data?","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":650,"Q_Id":43266059,"Users Score":1,"Answer":"there's always the dump data from django, which is pretty easy to use.\nor you could do this manually:\n\nif the 2 databases share the same data (they are mirror one to another) and the same table structure, you could just run a syncdb from django to create the new table structure and then dump and import (i'm assuming you're using mysql, but the general idea is the same) the old database into the new one\nif the two databases share different data (still with the same structure) you should import every single row of the two databases: this way, you'll keep relations etc, but you'll have your unique id updated to the new sole db.\nif the two databases are different in both data and structure, you'll have to run two sincdb and two imports, but this doesn't seem to be your case","Q_Score":2,"Tags":"python,django,postgresql,django-models,django-database","A_Id":43267208,"CreationDate":"2017-04-06T21:27:00.000","Title":"How to intelligently merge Django databases?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I need a small help.\nI am new to postgres and django. I am creating a project in django where there will n number of clients and their data is saved into the database on monthly basis.\nSo my doubts is should i go with only a single table and save all the data inside it or do I have an option to create individual tables dynamically as the user approaches and then save the values into those table?","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":324,"Q_Id":43367732,"Users Score":1,"Answer":"In fact you do not need to create a special table for each customer. SQL databases is designed in a manner to keep all similar data in one table. It is much easier to work with them in such a way.\nAt a moment I'd like to recommend to read about relational databases to better understand ways how to store data in it. Then you'll see how to better design application and data storage.","Q_Score":0,"Tags":"python,django,postgresql","A_Id":43369451,"CreationDate":"2017-04-12T11:01:00.000","Title":"Creating dynamic tables in postgres using django","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm using Python 2.7 and flask framework with flask-sqlalchemy module.\nI always get the following exception when trying to insert : Exception Type: OperationalError. Exception Value: (1366, \"Incorrect string value: \\xF09...\nI already set MySQL database, table and corresponding column to utf8mb4_general_ci and I can insert emoji string using terminal.\nFlask's app config already contains app.config['MYSQL_DATABASE_CHARSET'] = 'utf8mb4', however it doesn't help at all and I still get the exception.\nAny help is appreciated","AnswerCount":4,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1485,"Q_Id":43557926,"Users Score":0,"Answer":"Add config file main file and set set 'charset' => 'utf8mb4'\nyou have to edit field in which you want to store emoji and set collation as utf8mb4_unicode_ci","Q_Score":4,"Tags":"python,mysql,flask","A_Id":43557984,"CreationDate":"2017-04-22T10:08:00.000","Title":"Flask SQLAlchemy can't insert emoji to MySQL","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Can I perform a PATCH request to collection?\nLike UPDATE table SET foo=bar WHERE some>10 in SQL.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":229,"Q_Id":43581457,"Users Score":0,"Answer":"No that is not supported, and probably should not (see Andrey Shipilov comment).","Q_Score":0,"Tags":"python,mongodb,eve","A_Id":43589357,"CreationDate":"2017-04-24T06:45:00.000","Title":"Bulk PATCH in python eve","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I use cqlengine with django. In some occasions Cassandra throws an error indicating that user has no permissions do to something. Sometimes this is select, sometimes this is update or sometimes it is something else. I have no code to share, because there is no specific line that does this. I am very sure that user has all the permissions, and sometimes it works. So if user did not have the permissions it should always throw no permission error. \nSo what might be the reasons behind this and how to find the problem?","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":292,"Q_Id":43622277,"Users Score":0,"Answer":"Is the system_auth keyspace RF the same as the amount of nodes? Did you try to run a repair on the system_auth keyspace already? If not do so.\nFor me it sounds like a consistency issue.","Q_Score":0,"Tags":"python,django,cassandra,permissions,cqlengine","A_Id":43630653,"CreationDate":"2017-04-25T22:54:00.000","Title":"Cassandra: occasional permission errors","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I use cqlengine with django. In some occasions Cassandra throws an error indicating that user has no permissions do to something. Sometimes this is select, sometimes this is update or sometimes it is something else. I have no code to share, because there is no specific line that does this. I am very sure that user has all the permissions, and sometimes it works. So if user did not have the permissions it should always throw no permission error. \nSo what might be the reasons behind this and how to find the problem?","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":292,"Q_Id":43622277,"Users Score":0,"Answer":"If you have authentication enabled, make sure you set appropriate RF for keyspace system_auth (should be equal to number of nodes).\nSecondly, make sure the user you have created has following permissions on all keyspaces. {'ALTER', 'CREATE', 'DROP', 'MODIFY', 'SELECT'}. If you have the user as a superuser make sure you add 'AUTHORIZE' as a permission along with the ones listed above for that user.  \nThirdly, you can set off a read-repair job for all the data in system_auth keyspace by running CONSISTENCY ALL;\nSELECT * from system_auth.users ;\nSELECT * from system_auth.permissions ;\nSELECT * from system_auth.credentials ;\nHope this will resolve the issue !","Q_Score":0,"Tags":"python,django,cassandra,permissions,cqlengine","A_Id":43645204,"CreationDate":"2017-04-25T22:54:00.000","Title":"Cassandra: occasional permission errors","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I use SQLite3 in python because my school computers don't allow us to install anything to python so I used the pre installed SQLite3 module.\nI'm working on a program whose back end relies on an SQLite3  database, however the databases are created and stored on their computer.\nIs it possible for me to \"Host\" an SQLite3 database on let's say a server and allow my script to access them remotely (my script could edit the database from my school computer)?\nBy the way, I'm using python 3.X\nEDIT\ni made a database api that runs in python 3, its called TaliffDb\nto install type pip3 install TaliffDB in your terminal. im working on a documentation, but please do comment if you have any questions","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1615,"Q_Id":43647227,"Users Score":1,"Answer":"Write an API on the remote server, yes. This could be hosted by a web framework of your choice. \nYou won't get a direct network connection to a file","Q_Score":1,"Tags":"python,python-3.x,sqlite","A_Id":43647246,"CreationDate":"2017-04-27T01:37:00.000","Title":"How to connect to SQLite3 database in python remotely","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am deploying a Django App using Elastic Beanstalk on AWS. The app has a function whereby user can register their details.\nThe problem is when I make small changes to my app and deploy this new version I loose the registered users since their information isn't in my local database (only the database on aws).\nIs there any way to download the modifications to the database during production so that I can keep these changes when I redeploy. \nI'm not using AWS RDS, I simply bundle the .SQLite file with my source code and deploy to Elastic Beanstalk.\nThanks in Advance.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":137,"Q_Id":43650204,"Users Score":0,"Answer":"Don't bundle the development .sqlite file with the production stuff. It needs to have its own .sqlite file and you just need to run migrations on the production one.","Q_Score":0,"Tags":"python,django,sqlite,amazon-web-services,amazon-elastic-beanstalk","A_Id":43666611,"CreationDate":"2017-04-27T06:31:00.000","Title":"Update sqlite database based on changes in production","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have written a piece of python code that scrapes the odds of horse races from a bookmaker's site. I wish to now:\n\nRun the code at prescribed increasingly frequent times as the race draws closer.\nStore the scraped data in a database fit for extraction and statistical analysis in R.\n\nApologies if the question is poorly phrased\/explained - I'm entirely self taught and so have no formal training in computer science. I don't know how to tell a piece of python code to run itself every say n-minutes and I also have no idea how to correctly approach building such a data base or what factors I should be considering. Can someone point me in the right direction for getting started on the above?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":73,"Q_Id":43670334,"Users Score":0,"Answer":"In windows, you can use Task Scheduler or in Linux crontab. You can configure these to run python with your script at set intervals of time. This way you don't have a python script continuously running preventing some hangup in a single call from impacting all subsequent attempts to scrape or store in database.\nTo store the data there are many options which could either be a flat file(write to a text file), save as a python binary(use shelf or pickle), or install an actual database like MySQL or PostgreSQL and many more. Google for info. Additionally an ORM like SQLAlchemy may make controlling, querying, and updating your database a little easier since it will handle all tables as objects and create the SQL itself so you don't need to code all queries as strings.","Q_Score":0,"Tags":"python,database-design,web-scraping","A_Id":43670482,"CreationDate":"2017-04-28T01:07:00.000","Title":"How to run python code at prescribed time and store output in database","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm using boto3 and trying to upload files. It will be helpful if anyone will explain exact difference between file_upload() and put_object() s3 bucket methods in boto3  ?   \n\nIs there any performance difference?\nDoes anyone among these handles multipart upload feature in behind the scenes?\nWhat are the best use cases for both?","AnswerCount":3,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":16616,"Q_Id":43739415,"Users Score":51,"Answer":"The upload_file method is handled by the S3 Transfer Manager, this means that it will automatically handle multipart uploads behind the scenes for you, if necessary.\nThe put_object method maps directly to the low-level S3 API request. It does not handle multipart uploads for you. It will attempt to send the entire body in one request.","Q_Score":49,"Tags":"python,amazon-web-services,amazon-s3,boto3","A_Id":43744495,"CreationDate":"2017-05-02T13:40:00.000","Title":"What is the Difference between file_upload() and put_object() when uploading files to S3 using boto3","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":1,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I process a report that consists of date fields. There are some instances wherein the date seen in the cell is not a number (how do I know? I use the isnumber() function from excel to check if a date value is really a number).\nUsing a recorded macro, for all the date columns, I do the text to columns function in excel to make these dates pass the isnumber() validation. \nAnd then I continue further processing using my python sccipt.\nBut now I need to replicate the text to column action in excel, and imitate this in Python openpyxl.\nI naively tried to do the int(cell.value) but this didn't worked.\nSo to sum up the questions, is there a way in Python to convert a date represented as text, to be changed to a date represented as a number?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":940,"Q_Id":43779887,"Users Score":0,"Answer":"Sounds like you might want to take advantage of the type guessing in openpyxl. If so, open the workbook with guess_types=True and see if that helps. NB. this feature is more suited to working with text sources like CSV and is likely to be removed in future releases.","Q_Score":0,"Tags":"python,excel,openpyxl","A_Id":43783883,"CreationDate":"2017-05-04T10:07:00.000","Title":"How to convert date formatted as string to a number in excel using openpyxl","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"When attempting to connect to a PostgreSQL database with ODBC I get the following error:\n\n('08P01', '[08P01] [unixODBC]ERROR: Unsupported startup parameter: geqo (210) (SQLDriverConnect)')\n\nI get this with two different ODBC front-ends (pyodbc for Python and ODBC.jl for Julia), so it's clearly coming from the ODBC library itself.  Is there a way to stop it from passing this \"geqo\" parameter?\nAn example in pyodbc would be very useful.\nThanks.","AnswerCount":2,"Available Count":1,"Score":-0.0996679946,"is_accepted":false,"ViewCount":913,"Q_Id":43789951,"Users Score":-1,"Answer":"Config SSL Mode: allow in ODBC Driver postgres, driver version: 9.3.400","Q_Score":1,"Tags":"python,postgresql,odbc,julia","A_Id":43872906,"CreationDate":"2017-05-04T18:08:00.000","Title":"unsupported startup parameter geqo when connecting to PostgreSQL with ODBC","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":0},{"Question":"I have some pretty big, multi level,  documents with LOTS of fields (over 1500 fields). While I want to save the whole document in mongo, Ido not want to define the whole schema. Only a handful of fields are important. I also need to index those \"important\" fields. Is this something that can be done?\nThank you","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":96,"Q_Id":43792282,"Users Score":1,"Answer":"Nevermind... found it... (ALLOW_UNKNOWN)","Q_Score":0,"Tags":"python,eve","A_Id":43792616,"CreationDate":"2017-05-04T20:31:00.000","Title":"Is it possible to define a partial schema Python-eve?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"After doing a bit of research I am finding it difficult to find out how to use mysql timestamps in matplotlib.\nMysql fields to plot\nX-axis:\nField: entered\nType: timestamp\nNull: NO\nDefault: CURRENT TIMESTAMP\nSample: 2017-05-08 18:25:10\nY-axis:\nField: value\nType: float(12,6)\nNull: NO\nSample: 123.332\nWhat date format is matplotlib looking for? How do I convert to this format? I found out how to convert from unix timestamp to a format that is acceptable with matplotlib, is unix timestamp better than the timestamp field type I am using? Should I convert my whole table to unix timestamps instead?\nWould appreciate any help!","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":202,"Q_Id":43859988,"Users Score":0,"Answer":"you can use datetime module,although i use now() function to extract datetime from mysql,but i consider the format is the same\u3002\nfor instance\npython>import datetime as dt\ni put the datetime data into a list named datelist,and now you can use  datetime.strptime function to convert the date format to what you want\npython>dates = [dt.datetime.strptime(d,'%Y-%m-%d %H:%M:%S') for d in datelist\nAt last,you can put the list named dates into plot X-axis\nI hope it helps you.","Q_Score":0,"Tags":"python,mysql,matplotlib","A_Id":43860724,"CreationDate":"2017-05-09T02:17:00.000","Title":"Python - convert mysql timestamps type to matplotlib and graph","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am trying to access a Spreadsheet on a Team Drive using gspread. It is not working.  It works if the spreadsheet is on my Google Drive. I was wondering if gspread has the new Google Drive API v3 capability available to open spreadsheets on Team Drives. If so, how do I specify the fact I want to open a spreadsheet on a Google Team Drive and not my own Google drive? If not, when will that functionality be available? Thanks!","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":426,"Q_Id":43897009,"Users Score":0,"Answer":"Make sure you're using the latest version of gspread. The one that is e.g. bundled with Google Colab is outdated:\n!pip install --upgrade gspread\nThis fixed the error in gs.csv_import for me on a team drive.","Q_Score":1,"Tags":"python,google-apps-script,gspread","A_Id":65546184,"CreationDate":"2017-05-10T15:34:00.000","Title":"Does gspread Support Accessing Spreadsheets on Team Drives?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a AWS lambda implemented using python\/pymysql with AWS rds Mysql instance as backend. It connects and works well and I can also access the lambda from my android app. \nThe problem I have is after I insert a value into rds mysql tables successfully using local machine mysql workbench and run the lambda function from AWS console its not showing the newly inserted value instantly. On the python aws lambda code I am not closing the connection or cursor. \nBut if I edit the lambda function on the AWS console, by edit I mean just insert a space and again run the lambda from AWS console it fetches the newly inserted value.\nHow do I configure\/code to make lambda fetch db values in realtime.","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":878,"Q_Id":43944404,"Users Score":0,"Answer":"AWS recommends making a global connection (before your handler function definition) in order to increase performance. Idea is that a new connection does not have to be established and the previous connection to the DB is reused, even when multiple instances of Lambda are run in close connection. But if your use case involves referencing MySQL tables through Lambda, especially if the table is regularly updated, I'd recommend initiating the connection object locally (inside the handler function) and then closing it after you run your queries. This is much in tandem to @dnevins' response and was the only way it worked for me as well. Hope this helps!","Q_Score":3,"Tags":"python,amazon-web-services,aws-lambda,amazon-rds","A_Id":56725577,"CreationDate":"2017-05-12T18:31:00.000","Title":"Python Aws lambda function not fetching the rds Mysql table value in realtime","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Ubuntu 14.04.3, PostgreSQL 9.6\nMaybe I can get the plpythonu source code from the PostgreSQL 9.6 source code or somewhere else, put it into the \/contrib directory, make it and CREATE EXTENSION after that!? Or something like that.\nDon't want to think that PostgreSQL reinstall is my only way.","AnswerCount":1,"Available Count":1,"Score":0.3799489623,"is_accepted":false,"ViewCount":2374,"Q_Id":43984705,"Users Score":2,"Answer":"you can simply run \npython 2\nsudo apt-get install postgresql-contrib postgresql-plpython-9.6\npython 3\nsudo apt-get install postgresql-contrib postgresql-plpython3-9.6\nThen check the extension is installed\nSELECT * FROM pg_available_extensions WHERE name like '%plpython%';\nTo apply the extension to the database, use\nfor python 2\nCREATE EXTENSION plpython2u;\nfor python 3\nCREATE EXTENSION plpython3u;","Q_Score":2,"Tags":"postgresql,plpython","A_Id":44186978,"CreationDate":"2017-05-15T16:36:00.000","Title":"Is there a way to install PL\/Python after the database has been compiled without \"--with-python\" parameter?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm having issues connecting to a working SQL\\Express database instance using Robot Framework's DatabaseLibrary.\nIf I use either Connect To Database with previously defined variables or Connect To Database Using Custom Params with a connection string, I get the following results:\n\npyodbc: ('08001', '[08001] [Microsoft][ODBC SQL Server Driver][DBNETLIB]SQL Server does not exist or access denied. (17) (SQLDriverConnect); [01000] [Microsoft][ODBC SQL Server Driver][DBNETLIB]ConnectionOpen (Connect()). (53)')\npymssql:: InterfaceError: Connection to the database failed for an unknown reason.\n\nThe connection string I'm using is the following: 'DRIVER={SQL Server};SERVER=localhost\\SQLExpress;UID=sa;PWD=mypass;DATABASE=MyDb'\nI copied several examples from guides and tutorials and all of them yield the same result, so my guess is that there is something wrong on my end, but I just can't figure out what. I can access the database using the Microsoft SQL Server Management Studio just fine, so the database is running.\nAny guidance will be greatly appreciated!","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1854,"Q_Id":43988892,"Users Score":2,"Answer":"I was able to connect using @Goralight approach: Connect To Database Using Custom Params pymssql ${DBConnect} where ${DBConnect} contained database, user, Password, host and port","Q_Score":2,"Tags":"python,robotframework,pyodbc,pymssql","A_Id":44121400,"CreationDate":"2017-05-15T21:11:00.000","Title":"Cannot connect to SQL\\Express with pyodbc\/pymssql and Robot Framework","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have sqlite db runing on my server. I want to access it using client side javascript in browser. Is this possible?\nAs of now, I am using python to access the db and calling python scripts for db operations.","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":158,"Q_Id":44000687,"Users Score":1,"Answer":"It's not a good idea to allow clients to access directly to the db. If you have to do it be carefull to not give to the account you use full write\/read access to the db or any malicius client can erase modify or steal information from the db.\nAn implementation with client identification server-side and rest API to return or modify DB it's safer.","Q_Score":0,"Tags":"javascript,python,sql,sqlite","A_Id":44001568,"CreationDate":"2017-05-16T11:51:00.000","Title":"Access sqlite in server through client side javascript","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am trying to install mysqlclient on mac to use mysql in a django project. I have made sure that setup tools is installed and that mysql connector c is installed as well. I keep getting the error Command \"python setup.py egg_info\" failed with error code 1 in. This is my first django project since switching from rails. Is there something I am missing? I am using python 3 and I use pip install mysqlclient.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":599,"Q_Id":44008037,"Users Score":0,"Answer":"I was able to fix this by running pip install mysql. I do not understand why this worked because I already had MySQL installed on my system and had been using it.\nI am going to assume it is because Python uses environments and MySQL wasn't installed in the environment but I would like to know for sure.","Q_Score":0,"Tags":"python,mysql,django,pip","A_Id":44036652,"CreationDate":"2017-05-16T17:32:00.000","Title":"Mysqlclient fails to install","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am looking for a method for hiding all rows in an excel sheet using python's openpyxl module. I would like, for example, to hide all rows from the 10th one to the end. Is it possible in openpyxl? For instance in xlsxwriter there is a way to hide all unused rows. So I am looking for a similar funcitonality in openpyxl, but I can not find it in docs or anywhere else, so any help will be much appreciated.\nI know it can be easily done by iterating over rows, but this approach is awfully slow, so I would like to find something faster.","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":413,"Q_Id":44028186,"Users Score":1,"Answer":"As far as I know, there is no such feature at the moment in the openpyxl. However, this can be easily done in an optimized way in the xlsxwriter module.","Q_Score":1,"Tags":"python,excel,openpyxl,xlsxwriter","A_Id":45254364,"CreationDate":"2017-05-17T14:48:00.000","Title":"python openpyxl: hide all rows from to the end","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Getting neo4j.v1.api.CypherError: Internal error - should have used fall back to execute query, but something went horribly wrong when using python neomodel client with neo4j community edition 3.2.0 server.\nAnd the neo4j server logs has the below errors:\n\n2017-05-16 12:54:24.187+0000 ERROR [o.n.b.v.r.ErrorReporter] Client\n  triggered an unexpected error [UnknownError]: Internal error - should\n  have used fall back to execute query, but something went horribly\n  wrong, reference 4c32d6e0-a66a-4db4-830c-b8d03ce6f1e3.\n2017-05-16 12:54:24.187+0000 ERROR [o.n.b.v.r.ErrorReporter] Client\n  triggered an unexpected error [UnknownError]: Internal error - should\n  have used fall back to execute query, but something went horribly\n  wrong, reference 4c32d6e0-a66a-4db4-830c-b8d03ce6f1e3. Internal error\n  - should have used fall back to execute query, but something went horribly wrong\n  org.neo4j.cypher.internal.ir.v3_2.exception.CantHandleQueryException:\n  Internal error - should have used fall back to execute query, but\n  something went horribly wrong","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":213,"Q_Id":44043171,"Users Score":2,"Answer":"This seems to be a issue with neo4j version 3.2.0. Setting cypher.default_language_version to 3.1 in neo4j.conf and restarting the server should fix this.","Q_Score":0,"Tags":"python,python-3.x,neo4j","A_Id":44043172,"CreationDate":"2017-05-18T09:00:00.000","Title":"neo4j.v1.api.CypherError: Internal error - should have used fall back to execute query, but something went horribly wrong","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am building a python 3.6 AWS Lambda deploy package and was facing an issue with SQLite. \nIn my code I am using nltk which has a import sqlite3 in one of the files.\nSteps taken till now:\n\nDeployment package has only python modules that I am using in the root. I get the error:\nUnable to import module 'my_program': No module named '_sqlite3'\nAdded the _sqlite3.so from \/home\/my_username\/anaconda2\/envs\/py3k\/lib\/python3.6\/lib-dynload\/_sqlite3.so into package root. Then my error changed to:\nUnable to import module 'my_program': dynamic module does not define module export function (PyInit__sqlite3)\nAdded the SQLite precompiled binaries from sqlite.org to the root of my package but I still get the error as point #2.\n\nMy setup: Ubuntu 16.04, python3 virtual env\nAWS lambda env: python3\nHow can I fix this problem?","AnswerCount":8,"Available Count":2,"Score":1.0,"is_accepted":false,"ViewCount":7936,"Q_Id":44058239,"Users Score":6,"Answer":"This isn't a solution, but I have an explanation why.\nPython 3 has support for sqlite in the standard library (stable to the point of pip knowing and not allowing installation of pysqlite). However, this library requires the sqlite developer tools (C libs) to be on the machine at runtime. Amazon's linux AMI does not have these installed by default, which is what AWS Lambda runs on (naked ami instances). I'm not sure if this means that sqlite support isn't installed or just won't work until the libraries are added, though, because I tested things in the wrong order.\nPython 2 does not support sqlite in the standard library, you have to use a third party lib like pysqlite to get that support. This means that the binaries can be built more easily without depending on the machine state or path variables. \nMy suggestion, which you've already done I see, is to just run that function in python 2.7 if you can (and make your unit testing just that much harder :\/).\nBecause of the limitations (it being something baked into python's base libs in 3) it is more difficult to create a lambda-friendly deployment package. The only thing I can suggest is to either petition AWS to add that support to lambda or (if you can get away without actually using the sqlite pieces in nltk) copying anaconda by putting blank libraries that have the proper methods and attributes but don't actually do anything.\nIf you're curious about the latter, check out any of the fake\/_sqlite3 files in an anaconda install. The idea is only to avoid import errors.","Q_Score":23,"Tags":"python-3.x,amazon-web-services,sqlite,aws-lambda","A_Id":44076628,"CreationDate":"2017-05-18T21:43:00.000","Title":"sqlite3 error on AWS lambda with Python 3","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am building a python 3.6 AWS Lambda deploy package and was facing an issue with SQLite. \nIn my code I am using nltk which has a import sqlite3 in one of the files.\nSteps taken till now:\n\nDeployment package has only python modules that I am using in the root. I get the error:\nUnable to import module 'my_program': No module named '_sqlite3'\nAdded the _sqlite3.so from \/home\/my_username\/anaconda2\/envs\/py3k\/lib\/python3.6\/lib-dynload\/_sqlite3.so into package root. Then my error changed to:\nUnable to import module 'my_program': dynamic module does not define module export function (PyInit__sqlite3)\nAdded the SQLite precompiled binaries from sqlite.org to the root of my package but I still get the error as point #2.\n\nMy setup: Ubuntu 16.04, python3 virtual env\nAWS lambda env: python3\nHow can I fix this problem?","AnswerCount":8,"Available Count":2,"Score":0.024994793,"is_accepted":false,"ViewCount":7936,"Q_Id":44058239,"Users Score":1,"Answer":"My solution may or may not apply to you (as it depends on Python 3.5), but hopefully it may shed some light for similar issue.\nsqlite3 comes with standard library, but is not built with the python3.6 that AWS use, with the reason explained by apathyman and other answers.\nThe quick hack is to include the share object .so into your lambda package:\nfind ~ -name _sqlite3.so\nIn my case:\n\/home\/user\/anaconda3\/pkgs\/python-3.5.2-0\/lib\/python3.5\/lib-dynload\/_sqlite3.so\nHowever, that is not totally sufficient. You will get: \nImportError: libpython3.5m.so.1.0: cannot open shared object file: No such file or directory\nBecause the _sqlite3.so is built with python3.5, it also requires python3.5 share object. You will also need that in your package deployment:\nfind ~ -name libpython3.5m.so*\nIn my case:\n\/home\/user\/anaconda3\/pkgs\/python-3.5.2-0\/lib\/libpython3.5m.so.1.0\nThis solution is likely not work if you are using _sqlite3.so that is built with python3.6, because the libpython3.6 built by AWS will likely not support this. However, this is just my educational guess. If anyone has successfully done, please let me know.","Q_Score":23,"Tags":"python-3.x,amazon-web-services,sqlite,aws-lambda","A_Id":49342276,"CreationDate":"2017-05-18T21:43:00.000","Title":"sqlite3 error on AWS lambda with Python 3","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I haven't been able to find any direct answers, so I thought I'd ask here.\nCan ETL, say for example AWS Glue, be used to perform aggregations to lower the resolution of data to AVG, MIN, MAX, etc over arbitrary time ranges?\ne.g. - Given 2000+ data points of outside temperature in the past month, use an ETL job to lower that resolution to 30 data points of daily averages over the past month. (actual use case of such data aside, just an example).\nThe idea is to perform aggregations to lower the resolution of data to make charts, graphs, etc display long time ranges of large data sets more quickly, as we don't need every individual data point that we must then dynamically aggregate on the fly for these charts and graphs.\nMy research so far only suggests that ETL be used for 1 to 1 transformations of data, not 1000 to 1. It seems ETL is used more for transforming data to appropriate structure to store in a db, and not for aggregating over large data sets.\nCould I use ETL to solve my aggregation needs? This will be on a very large scale, implemented with AWS and Python.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":588,"Q_Id":44074550,"Users Score":0,"Answer":"The 'T' in ETL stands for 'Transform', and aggregation is one of most common ones performed. Briefly speaking: yes, ETL can do this for you. The rest depends on specific needs. Do you need any drill-down? Increasing resolution on zoom perhaps? This would affect the whole design, but in general preparing your data for presentation layer is exactly what ETL is used for.","Q_Score":0,"Tags":"python,amazon-web-services,etl,aws-glue","A_Id":44107589,"CreationDate":"2017-05-19T16:09:00.000","Title":"Using ETL for Aggregations","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am building a web application that allows users to login and upload data files that would eventually be used to perform data visualisation and data mining features - Imagine a SAS EG\/Orange equivalent on the web.\nWhat are the best practices to store these files (in a database or on file) to facilitate efficient retrieval and processing of the data and the pros and cons of each method?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":299,"Q_Id":44094933,"Users Score":0,"Answer":"This depends on what functionality you can offer.\nMany very interesting data mining tools will read raw data files only, so storing the data in a database does not help you anything.\nBut then you won't want to run them \"on the web\" anyway, as they easily eat all your resources.\nEither way, first get your requirements straight and explicit, then settle on the analysis tools, then decide on the storage backend depending on what the tools can use.","Q_Score":0,"Tags":"python,django,database,data-visualization,data-mining","A_Id":44206133,"CreationDate":"2017-05-21T08:50:00.000","Title":"Storing data files on Django application","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am using Python 2.7 and SQLite3.\nWhen I starting work with DB I want to check - does my database is empty or on not. I mean does it already have any tables or not.\nMy idea is to use the simple SELECT from any table. And wrap this select in try:exception block. So if exception was raised then my DB is empty.\nMaybe someone know the better way for checking?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1822,"Q_Id":44098235,"Users Score":4,"Answer":"SELECT name FROM sqlite_master\nwhile connected to your database will give you all the tables names. you can then do a fetchall and check the size, or even contents of the list. not try\/catch necessary (the list will be empty if the database doesn't contain any tables)","Q_Score":2,"Tags":"python,sqlite","A_Id":44098371,"CreationDate":"2017-05-21T14:50:00.000","Title":"How could I check - does my SQLite3 database is empty?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I was running Django 1.11 with Python 3.5 and I decided to upgrade to Python 3.6.\nMost things worked well, but I am having issues connection to AWS S3. I know that they have a new boto version boto3 and that django-storages is a little outdated, so now there is django-storages-redux.\nI've been trying multiple combinations of boto\/boto3 and django-storages-redux\/django-storages to see if it works. But I'm getting a lot of erros, from SSL connection failing to the whole website being offline due to server errors. The newest is my website throwing a 400 Bad Request to all urls.\nMy app does run on Python 3.5, so I'm confident that the issue is around collectstatic and S3.\nIs there anybody here who made a similar update work and tell me what configuration was used?\nThanks a lot!","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":149,"Q_Id":44121989,"Users Score":-1,"Answer":"Found the issue.\nDjango-storages-redux was temporarily replacing django-storages since it's development had been interrupted.\nNow the django-storages team restarted to support it.\nThat means that the correct configuration to use is: django-storages + boto3","Q_Score":0,"Tags":"django,python-3.x,amazon-s3,boto","A_Id":44122528,"CreationDate":"2017-05-22T20:53:00.000","Title":"Django: Upgrading to python3.6 with Amazon S3","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm making a web crawler in Python that collects redirects\/links, adds them to a database, and enters them as a new row if the link doesn't already exist. I want like to use multi-threading but having trouble because I have to check in real time if there is an entry with a given URL. \nI was initially using sqlite3 but realised I can't use it simultaneously on different threads. I don't really want to use MySQL (or something similar) as it needs more disk space and runs as separate server. Is there anyway to make sqlite3 work with multiple threads?","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":7557,"Q_Id":44123678,"Users Score":0,"Answer":"One solution could be to acquire a lock to access the database directly from your program. In this way the multiple threads or processes will wait the other processes to insert the link before performing a request.","Q_Score":3,"Tags":"python,multithreading,sqlite,multiprocessing","A_Id":44123745,"CreationDate":"2017-05-22T23:47:00.000","Title":"Getting SQLite3 to work with multiple threads","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have pretty simple model. User defines url and database name for his own Postgres server. My django backend fetches some info from client DB to make some calculations, analytics and draw some graphs.\nHow to handle connections? Create new one when client opens a page, or keep connections alive all the time?(about 250-300 possible clients)\nCan I use Django ORM or smth like SQLAlchemy? Or even psycopg library?\nDoes anyone tackle such a problem before?\nThanks","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":77,"Q_Id":44139772,"Users Score":0,"Answer":"In your case, I would rather go with Django internal implementation and follow Django ORM as you will not need to worry about handling connection and different exceptions that may arise during your own implementation of DAO model in your code.\nAs per your requirement, you need to access user database, there still exists overhead for individual users to create db and setup something to connect with your codebase. So, I thinking sticking with Django will be more profound.","Q_Score":0,"Tags":"python,django,database,postgresql,orm","A_Id":44139838,"CreationDate":"2017-05-23T16:00:00.000","Title":"Handle connections to user defined DB in Django","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Trying to install cx_Oracle on Solaris11U3 but getting ld: fatal: file \/oracle\/database\/lib\/libclntsh.so: wrong ELF class: ELFCLASS64 error\npython setup.py build\nrunning build\nrunning build_ext\nbuilding 'cx_Oracle' extension\ncc -DNDEBUG -KPIC -DPIC -I\/oracle\/database\/rdbms\/demo -I\/oracle\/database\/rdbms\/public -I\/usr\/include\/python2.7 -c cx_Oracle.c -o build\/temp.solaris-2.11-sun4v.32bit-2.7-11g\/cx_Oracle.o -DBUILD_VERSION=5.2.1\n\"SessionPool.c\", line 202: warning: integer overflow detected: op \"<<\"\ncc -G build\/temp.solaris-2.11-sun4v.32bit-2.7-11g\/cx_Oracle.o -L\/oracle\/database\/lib -L\/usr\/lib -lclntsh -lpython2.7 -o build\/lib.solaris-2.11-sun4v.32bit-2.7-11g\/cx_Oracle.so\nld: fatal: file \/oracle\/database\/lib\/libclntsh.so: wrong ELF class: ELFCLASS64\nerror: command 'cc' failed with exit status 2\nTried all available information on the internet:\nInstalled gcc\nInstalled solarisstudio12.4\nInstalled instantclient-basic-solaris.sparc64-12.2.0.1.0, instantclient-odbc-solaris.sparc64-12.2.0.1.0\nSet LD_LIBRARY_PATH to oracle home directory:instantclient_12_2\/\nSame issue seen while installing DBD:Oracle perl module.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":268,"Q_Id":44155943,"Users Score":0,"Answer":"You cannot mix 32-bit and 64-bit together. Everything (Oracle client, Python, cx_Oracle) must be 32-bit or everything must be 64-bit. The error above looks like you are trying to mix a 64-bit Oracle client with a 32-bit Python.","Q_Score":0,"Tags":"python,cx-oracle","A_Id":44171743,"CreationDate":"2017-05-24T10:37:00.000","Title":"Python module cx_Oracle ld installation issue on Solaris11U3 SPARC: fatal: file \/oracle\/database\/lib\/libclntsh.so: wrong ELF class: ELFCLASS64 error","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":0},{"Question":"I recently did an inspectdb of our old database which is on MySQL. We want to move to postgre. now we want the inspection to migrate to a different schema is there a migrate command to achieve this? so different apps shall use different schemas in the same database","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":204,"Q_Id":44161614,"Users Score":0,"Answer":"so simple!\npython manage.py migrate \"app_name\"","Q_Score":0,"Tags":"postgresql,python-3.5,django-migrations,django-1.8,django-postgresql","A_Id":47838958,"CreationDate":"2017-05-24T14:39:00.000","Title":"how to specify an app to migrate to a schema django","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a table which I am working on and it contains 11 million rows there abouts... I need to run a migration on this table but since Django trys to store it all in cache I run out of ram or disk space which ever comes first and it comes to abrupt halt.\nI'm curious to know if anyone has faced this issue and has come up with a solution to essentially \"paginate\" migrations maybe into blocks of 10-20k rows at a time?\nJust to give a bit of background I am using Django 1.10 and Postgres 9.4 and I want to keep this automated still if possible (which I still think it can be)\nThanks\nSam","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":995,"Q_Id":44167386,"Users Score":5,"Answer":"The issue comes from a Postgresql which rewrites each row on adding a new column (field).\nWhat you would need to do is to write your own data migration in the following way:\n\nAdd a new column with null=True. In this case data will not be\nrewritten and migration will finish pretty fast. \nMigrate it \nAdd a default value \nMigrate it again.\n\nThat is basically a simple pattern on how to deal with adding a new row in a huge postgres database.","Q_Score":5,"Tags":"python,django,postgresql,django-migrations","A_Id":44167568,"CreationDate":"2017-05-24T19:55:00.000","Title":"Django migration 11 million rows, need to break it down","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"in my app I have a mixin that defines 2 fields like start_date and end_date. I've added this mixin to all table declarations which require these fields. \nI've also defined a function that returns filters (conditions) to test a timestamp (e.g. now) to be >= start_date and < end_date. Currently I'm manually adding these filters whenever I need to query a table with these fields.\nHowever sometimes me or my colleagues forget to add the filters, and I wonder whether it is possible to automatically extend any query on such a table. Like e.g. an additional function in the mixin that is invoked by SQLalchemy whenever it \"compiles\" the statement. I'm using 'compile' only as an example here, actually I don't know when or how to best do that.\nAny idea how to achieve this?\nIn case it works for SELECT, does it also work for INSERT and UPDATE?\nthanks a lot for your help\nJuergen","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":182,"Q_Id":44207726,"Users Score":0,"Answer":"I tried extending Query but had a hard time. Eventually (and unfortunately) I moved back to my previous approach of little helper functions returning filters and applying them to queries.\nI still wish I would find an approach that automatically adds certain filters if a table (Base) has certain columns.\nJuergen","Q_Score":1,"Tags":"python,sqlalchemy","A_Id":44395701,"CreationDate":"2017-05-26T18:06:00.000","Title":"sqlalchemy automatically extend query or update or insert upon table definition","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Yesterday, I installed an apche web server and phpmyadmin on my raspberry-py. How can I connect my raspberry-pi to databases in phpmyadmin with python? Can I use MySQL? Thank, I hope you understand my question and sorry for my bad english.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":110,"Q_Id":44215404,"Users Score":0,"Answer":"Your question is quite unclear. But from my understanding, here is what you should try doing: (Note: I am assuming you want to connect your Pi to a database to collect data and store in an IoT based application)\n\nGet a server. Any Basic server would do. I recommend DigitalOcean or AWS LightSail. They have usable servers for just $5 per month. I recommend Ubuntu 16.04 for ease of use.\nSSH into the server with your terminal with the IP address you got when you created the server\nInstall Apache, MySQL, Python, PHPMyAdmin on the server. \nWrite your web application in any language\/framework you want. \nDeploy it and write a separate program to make HTTP calls to the said web server. \n\nMySQL is the Database server. Python is the language that is used to execute any instructions. PHPMyAdmin is the interface to view MySQL Databases and Tables. Apache is the webserver that serves the application you have written to deal with requests.\nI strongly recommend understanding the basics of Client-Server model of computing over HTTP. \nAlternatively, you could also use the approach of Using a DataBase-as-a-service from any popular cloud service provider(Eg., AWS RDS), to make calls directly into the DB.","Q_Score":0,"Tags":"python,mysql,apache,raspberry-pi","A_Id":44215522,"CreationDate":"2017-05-27T09:52:00.000","Title":"connect my raspbery-pi to MySQL","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm currently programming in python :\n- a graphical interface\n- my own simple client-server based on sockets (also in python).  \nThe main purpose here is to recieve a message (composed of several fields), apply any changes on it, and then send back the message to the client.   \nWhat I want to achieve is to link the modification of a field of this message with any script (I Just saw radamsa which could do the job, I still need to test it.\nFor example the message : John\/smith\/London would be John\/(request by script)\/London.  \nI don't know if it's even possible to use just a part of code of something like sqlmap (or something else, I don't mind), without the whole thing.  \nI hope I have given enough details, if not, feel free to ask for any  =)\nEdit: the use of sqlmap is not mandatory, it's just one of the few fuzzing scripts i was aware of","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":156,"Q_Id":44262826,"Users Score":0,"Answer":"Update :\nI finally managed to do what I had in mind.\nIn SQLmap, the \"dictionnary\" can be found in the \"\/xml\" directory.\nBy using several \"grep\" I have been able to follow the flow of creation. Then, to create the global payload, and then split it in real SQL payload","Q_Score":0,"Tags":"python,python-3.x,sockets,unix,sqlmap","A_Id":44585660,"CreationDate":"2017-05-30T12:51:00.000","Title":"How to link sqlmap with my own script","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm calling a database, and returning a datetime.datetime object as the 3rd item in a tuple.\nThe SQL statement is: SELECT name,name_text,time_received FROM {}.{} WHERE DATE(time_received)=CURRENT_DATE LIMIT 1\nIf I do print(mytuple[2]) it returns something like: 2017-05-31 17:21:19+00:00 but always with that \"+00:00\" at the end for every value. How do I remove that trailing \"+00:00\" from the datetime.datetime object?\nI've tried different string-stripping methods like print(mytuple[2][:-6]) but it gives me an error saying that datetime.datetime object is not subscriptable. Thanks for any help!","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":4484,"Q_Id":44292280,"Users Score":0,"Answer":"I imagine in order to use string stripping methods, you must first convert it to a string, then strip it, then convert back to whatever format you want to use. Cheers","Q_Score":2,"Tags":"sql,database,python-3.x,datetime,psycopg2","A_Id":44292411,"CreationDate":"2017-05-31T18:31:00.000","Title":"How to remove \"+00:00\" from end of datetime.datetime object. (not remove time)","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"There is a data model(sql) with a scenario where it uses one input table and it is fed into the prediction model(python) and some output variables are generated onto another table and final join is done between input table and output table to get the complete table(sql). Note: there could be chances that output table doesn't predict values for every primary key in the input table.\nIs it good approach to create one table that is fed as input to prediction model and the same table is updated with the output variables i.e. we pass those columns as complete null during input and they are updated as the values are predicted? If not, then what are the disadvantages for the same.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":123,"Q_Id":44295661,"Users Score":1,"Answer":"It's difficult to say without knowing what the database load and latency requirements are. I would typically avoid using the same table for source and output: I would worry about the cost and contention of simultaneously reading from the table and then writing back to the table but this isn't going to be a problem for low load scenarios. (If you're only running a single process that is doing both the reading and writing then this isn't a problem at all.)\nSeparating Input\/Output may also make the system more understandable, especially if something unexpected goes wrong.","Q_Score":0,"Tags":"python,sql,postgresql","A_Id":44295921,"CreationDate":"2017-05-31T22:30:00.000","Title":"Best way to use input and output tables","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have set up a database using MySQL Community Edition to log serial numbers of HDD's and file names. I am instructed to find a way to integrate Python scripting into the database so that the logs can be entered through python programming instead of manually (as manually would take a ridiculous amount of time.) Pycharm was specified as the programming tool that will be used, I have done research for the past few days and haven't found any solid way that this should be done, the python connector doesn't appear to be able to work with Pycharm. Any suggestions?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":173,"Q_Id":44331043,"Users Score":0,"Answer":"Reading between the lines here. I believe what you are being asked to do is called ETL. If somebody were to ask me to do the above my approach would be\n\nForce an agreed upon format for the incoming data (probably a .csv)\nWrite a python application to; a. Read the data from the csv, b. Condition the data if necessary, c. Write the results to the database\n\nPycharm would be the tool that I would use to write my Python code. It would have nothing to do with MySql. The ETL process should be initiated from the command line so you can automate it. So you need to research the following for python. \n\nReading files from a csv\nParsing command line arguments\nConnecting and writing to a MySql database\n\nAgain, I'm doing some guessing here as your question is vague. \nSteveJ","Q_Score":0,"Tags":"python,mysql,pycharm,mysql-python","A_Id":44332632,"CreationDate":"2017-06-02T14:12:00.000","Title":"What is the best way to integrate Pycharm Python into a MySQL CE Database?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I wonder if a good habit is to have some logic in MySQL database (triggers etc.) instead of logic in Django backend. I'm aware of fact that some functionalities may be done both in backend and in database but I would like to do it in accordance with good practices. I'm not sure I should do some things manually or maybe whole database should be generated by Django (is it possible)? What are the best rules to do it as well as possible? I would like to know the opinion of experienced people.","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":133,"Q_Id":44353532,"Users Score":1,"Answer":"It is true that if you used a database for your business logic you could get maximum possible performance and security optimizations. However, you would also risk many things such as \n\nNo separation of concerns\nBeing bound to the database vendor\netc.\n\nAlso, whatever logic you write in your database won't be version controlled with your app. Thus, whenever you change your database, you will have to create all those things once again.\nInstead, use Django ORM. It will create and manage your database based on your models by itself. As a result, whenever you recreate your database, you will just have to run migrations with one single command and you are done.\nThis will cover most of the situations. And whenever you will need those speeds of stored procedures, Django ORM has you covered as well.\nIn short, I believe that business logic should be kept out of the database as much as possible.","Q_Score":0,"Tags":"python,mysql,django,django-models,django-rest-framework","A_Id":44354531,"CreationDate":"2017-06-04T11:24:00.000","Title":"Django - backend logic vs database logic","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am writing software that manipulates Excel sheets. So far, I've been using xlrd and xlwt to do so, and everything works pretty well.\n\nIt opens a sheet (xlrd) and copies select columns to a new workbook (xlwt)\nIt then opens the newly created workbook to read data (xlrd) and does some math and formatting with the data (which couldn't be done if the file isn't saved once) - (xlwt saves once again)\n\nHowever, I am now willing to add charts in my documents, and this function is not supported by xlwt. I have found that xlsxwriter does, but this adds other complications to my code: xlsxwriter only has xlsxwriter.close(), which saves AND closes the document. \nDoes anyone know if there's any workaround for this? Whenever I use xlsxwriter.close(), my workbook object containing the document I'm writing isn't usable anymore.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1717,"Q_Id":44387732,"Users Score":4,"Answer":"Fundamentally, there is no reason you need to read twice and save twice. For your current (no charts) process, you can just read the data you need using xlrd; then do all your processing; and write once with xlwt.\nFollowing this workflow, it is a relatively simple matter to replace xlwt with XlsxWriter.","Q_Score":4,"Tags":"python,excel,xlrd,xlsxwriter","A_Id":44417110,"CreationDate":"2017-06-06T10:37:00.000","Title":"Saving XlsxWriter workbook more than once","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm running pandas read_sql_query and cx_Oracle 6.0b2 to retrieve data from an Oracle database I've inherited to a DataFrame.\nA field in many Oracle tables has data type NUMBER(15, 0) with unsigned values. When I retrieve data from this field the DataFrame reports the data as int64 but the DataFrame values have 9 or fewer digits and are all signed negative. All the values have changed - I assume an integer overflow is happening somewhere.\nIf I convert the database values using to_char in the SQL query and then use pandas to_numeric on the DataFrame the values are type int64 and correct.\nI'm using Python 3.6.1 x64 and pandas 0.20.1. _USE_BOTTLENECK is False.\nHow can I retrieve the correct values from the tables without using to_char?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":577,"Q_Id":44392676,"Users Score":1,"Answer":"Removing pandas and just using cx_Oracle still resulted in an integer overflow so in the SQL query I'm using:\nCAST(field AS NUMBER(19))\nAt this moment I can only guess that any field between NUMBER(11) and NUMBER(18) will require an explicit CAST to NUMBER(19) to avoid the overflow.","Q_Score":0,"Tags":"python,sql,oracle,pandas,dataframe","A_Id":44519380,"CreationDate":"2017-06-06T14:24:00.000","Title":"pandas read_sql_query returns negative and incorrect values for Oracle Database number field containing positive values","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a PostgreSQL database that is being used by a front-end application built with Django, but being populated by a scraping tool in Node.js. I have made a sequence that I want to use across two different tables\/entities, which can be accessed by a function (nexval(serial)) and is called on every insert. This is not the primary key for these tables, but simply a way to maintain order through some metadata. Using it in Node.js during the insertion of the data into the tables is trivial, as I am using raw SQL queries. However, I am struggling with how to represent this using Django models. There does not seem to be any way to associate this Postgres function with a model's field.\nQuestion:\nIs there a way to use a Postgres function as the default value of a Django model field?","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":2587,"Q_Id":44444385,"Users Score":1,"Answer":"My eventual solution:\nOverride the save method of the model, using a raw query to SELECT nextval('serial') inside the override, setting that as the value of the necessary field, then call save on the parent (super(PARENT, self).save()).","Q_Score":3,"Tags":"python,django,postgresql,orm","A_Id":44806040,"CreationDate":"2017-06-08T19:47:00.000","Title":"Postgres Sequences as Default Value for Django Model Field","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"In my file there are MAX and MIN formulas in a row. \nSample \nCELLS  -     |  A  |  B  |  C  | D  |  E  |  F  |   G  |   H  | \nROW: | MAX | MIN | MIN | MAX | MIN | MIN | MAX | MIN |MIN \nIf the excel sheet is opened a green triangle is displaying with a warning message \"Inconsistent Formula\".","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":523,"Q_Id":44521638,"Users Score":1,"Answer":"This is a standard Excel warning to alert users to the fact that repeated and adjacent formulas are different since that may be an error.\nIt isn't possible to turn off this warning in XlsxWriter.","Q_Score":0,"Tags":"python,excel,python-2.7,xlsxwriter","A_Id":44523601,"CreationDate":"2017-06-13T12:31:00.000","Title":"How to Ignore \"Inconsistent Formula\" warning showing in generated .xlsx file using the python xlsxwriter?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"i'm actually making ajax request that call a php file which call a python file. My main problem is with the imports in the python scripts. I actually work on local.\nI'm on linux. When i do \"$ php myScript.php\"  ( which call python script inside ) it's work but when it come from the ajax call then the import of the python files does not work. So i moved some libraries in the current folder of the php and python script. First the import will only work if the library is in a folder, impossible to call a function from my other python script. Then i can't do \" import tweepy \" even if the library is in the current folder. But for pymongo its worked because I do \" from pymongo import MongoClient \". All my script worked when call from php or when executed with python throw command line.\nThoses libraries are also in my current python folder on linux but throw ajax call it never go there. I specify this at the beginning of each python file \"#!\/usr\/bin\/env python2.7\"\nHere the path of my files \nfolder \n----- script.php \n----- script.py \n----- pymongo[FOLDER] \n----- tweepy[FOLDER] \nPs : Sorry english is not my main language","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":104,"Q_Id":44558269,"Users Score":0,"Answer":"I finally succeed. In fact tweepy use the library call \"six\" which is not in my current folder. So i import all the python library in my folder, so i get no more error. \nBut i still don't understand why python does not go search the library in his normal folder instead in the current folder.","Q_Score":0,"Tags":"php,python,ajax,import,directory","A_Id":44577194,"CreationDate":"2017-06-15T03:56:00.000","Title":"executing python throw ajax , import does not work","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have data in CSV, in which one column is for fiscal year. \neg. 2017 - 2019 .\nPlease specify how to form the CREATE TABLE query and INSERT query with the Fiscal Year as field.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":130,"Q_Id":44560315,"Users Score":0,"Answer":"since it seems like range of years for fiscal postion. I would suggest to use two Integer field to store data.\nand\n\nand years will be in 4 numbers so use Type SMALLINT   this way you use half of the storage space then INT field.","Q_Score":0,"Tags":"python,mysql,csv","A_Id":44560766,"CreationDate":"2017-06-15T06:37:00.000","Title":"How to store fiscal year (eg. 2017-2020) in mysql?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Im trying to load xml file into the google bigquery ,can any one please help me how to solve this . I know we can load JSON ,CSV and AVRO files into big query . I need suggestion\/help, Is the any way can i load xml file into bigquery","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":834,"Q_Id":44588770,"Users Score":1,"Answer":"The easiest option is probably to convert your XML file either to CSV or to JSON and then load it. Without knowing the size and shape of your data it's hard to make a recommendation, but you can find a variety of converters if you search online for them.","Q_Score":0,"Tags":"xml,python-2.7,google-bigquery","A_Id":44590333,"CreationDate":"2017-06-16T12:00:00.000","Title":"how to load xml file into big query","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":1,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Firstly, this question isn't a request for code suggestions- it's more of a question about a general approach others would take for a given problem. \nI've been given the task of writing a web application in python to allow users to check the content of media files held on a shared server. There will also likely be a postgres database from which records for each file will be gathered.\nI want the web app to:\n1) Suggest the next file to check (from files that have yet to be checked) and have a link to the next unchecked file once the result of the previous check have been submitted. \n2) Prevent the app from suggesting the same file to multiple users simultaneously. \nIf it was just one user checking the files it would be easier, but I'm having trouble conceptualising how i'm going to achieve the two points above with multiple simultaneous users.\nAs I say, this isn't a code request i'm just just interested in what approach\/tools others feel would be best suited to this type of project. \nIf there are any python libraries that could be useful i'd be interested to hear any recommendations.\nThanks","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":49,"Q_Id":44606342,"Users Score":1,"Answer":"These requirements are more or less straightforward to follow. Given that you will have a persistent database that can share the state of each file with multiple sessions - and even multiple deploys - of your system - and that is more or less a given with Python + PostgreSQL.\nI'd  suggest you to create a Python class with a few fields yuu can use for the whole process, and use an ORM like SQLAlchemy or Django's to bind those to a database. The fields you will need are more or less: filename, filpath, timestamp, check_status - and some extra like \"locked_for_checking\", and \"checker\" (which might be a foreignkey to a Users collection). On presenting a file as a sugestion for  a given user, you set the \"locked_for_checking\" flag - and for the overall listing, yu create a list that exc\u00e7uds files \"checked\" or \"locked_for_checking\". (and sort the  files by timestamp\/size or other metadata that attends your requirements). \nYou will need some logic to \"unlock for checking\" if the first user does not complete  the checking in a given time frame, but that is it.","Q_Score":0,"Tags":"python,postgresql,python-3.x,flask","A_Id":44608243,"CreationDate":"2017-06-17T15:37:00.000","Title":"Python web app ideas- incremental\/unique file suggestions for multiple users","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a table of size 15 GB in DynamoDB. Now I need to transfer some data based on timestamps ( which is in db) to another DynamoDB. What would be the most efficient option here?\na) Transfer to S3,process with pandas or someway and put in the other table (data is huge. I feel this might take a huge time)\nb) Through DataPipeLine (read a lot but don't think we can put queries over there)\nc) Through EMR and Hive (this seems to be the best option but is it possible to do everything though a python script? Would I need to create an EMR Cluster and use it or create and terminate every time? How can EMR be used efficiently and cheaply as well?)","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":831,"Q_Id":44608785,"Users Score":1,"Answer":"I would suggest going with the data pipeline into S3 approach. And then have a script to read from S3 and process your records. You can schedule this to run on regular intervals to backup all your data. I don't think that any solution that does a full scan will offer you a faster way, because it is always limited by read throughput. \nAnother possible approach is to use dynamoDB stream and lambdas to maintain second table in real time. Still you will first need to process existing 15 GB once using approach above, and then switch to lambdas for keeping them in sync","Q_Score":1,"Tags":"python,hive,amazon-emr,amazon-data-pipeline","A_Id":44612782,"CreationDate":"2017-06-17T19:48:00.000","Title":"Data transfer from DynamoDB table to another DynamoDB table","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I connect to a postgres database hosted on AWS. Is there a way to find out the number of open connections to that database using python API?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":60,"Q_Id":44621606,"Users Score":1,"Answer":"I assume this is for RDS. There is no direct way via the AWS API. You could potentially get it from CloudWatch but you'd be better off connecting to the database and getting the count that way by querying pg_stat_activity.","Q_Score":0,"Tags":"python,postgresql,amazon-web-services","A_Id":44621822,"CreationDate":"2017-06-19T02:52:00.000","Title":"Finding number of open connections to postgres database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I want to find the same words in two different excel workbooks. I have two excel workbooks (data.xls and data1.xls). If in data.xls have the same words in the data1.xls, i want it to print the row of data1.xls that contain of the same words with data.xls. I hope u can help me. Thank you.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":67,"Q_Id":44626578,"Users Score":0,"Answer":"I am assuming that both excel sheets have a list of words, with one word in each cell. \nThe best way to write this program would be something like this:\n\nOpen the first excel file, you might find it easier to open if you export it as a CSV first. \nCreate a Dictionary to store word and Cell Index Pairs\nIterate over each cell\/word, add the word to the dictionary as the Key, with the Cell Reference as the Value. \nOpen the second excel file.\nIterate over each cell\/word, check if the word is present in the Dictionary, if it is, you can print out the corresponding cells or store them however you want.","Q_Score":0,"Tags":"excel,windows,python-2.7","A_Id":44626892,"CreationDate":"2017-06-19T09:17:00.000","Title":"python- how to find same words in two different excel workbooks","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm not able anymore to change my database on arangodb.\nIf I try to create a collection I get the error: \n\nCollection error: cannot create collection: invalid database directory\n\nIf I try to delete a collection I get the error: \n\nCouldn't delete collection.\n\nBesides that some of the collections are now corrupted.\nI've been working with this db for 2 months and I'm only getting these errors now.\nThanks.","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":111,"Q_Id":44632365,"Users Score":1,"Answer":"If anyone gets the same error anytime in life, it was just a temporary error due to server overload.","Q_Score":1,"Tags":"python,arangodb","A_Id":44649139,"CreationDate":"2017-06-19T13:47:00.000","Title":"Python ArangoDB","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm using google cloudSQL for applying advance search on people data to fetch the list of users. In datastore, there are data already stored there with 2 model. First is used to track current data of users and other model is used to track historical timeline. The current data is stored on google cloudSQL are more than millions rows for all users. Now I want to implement advance search on historical data including between dates by adding all history data to cloud.  \nIf anyone can suggest the better structure for this historical model as I've gone through many of the links and articles. But cannot find proper solution as I have to take care of the performance for search (In Current search, the time is taken to fetch result is normal but when history is fetched, It'll scan all the records which causes slowdown of queries because of complex JOINs as needed). The query that is used to fetch the data from cloudSQL are made dynamically based on the users' need. For example, A user want the employees list whose manager is \"xyz.123@abc.in\" , by using python code, the query will built accordingly. Now a user want to find users whose manager WAS \"xyz.123@abc.in\" with effectiveFrom 2016-05-02 to 2017-01-01.\nAs I've find some of the usecases for structure as below:\n1) Same model as current structure with new column flag for isCurrentData (status of data whether it is history or active)\nDisadv.:\n - queries slowdown while fetching data as it will scan all records.\n   Duplication of data might increase.\nThese all disadv. will affect the performance of advance search by increasing time.\n    Solution to this problem is to partition whole table into diff tables.\n2) Partition based on year.\n   As time passes, this will generate too many tables.\n3) 2 tables might be maintained.\n   1st for current data and second one for history. But when user want to search data on both models will create complexity of build query.\nSo, need suggestions for structuring historical timeline with improved performance and effective data handling.\nThanks in advance.","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":81,"Q_Id":44654127,"Users Score":0,"Answer":"@Kevin Malachowski : Thanks for guiding me with your info and questions as It gave me new way of thinking. \nHistorical data records will be more than 0.3-0.5 million(maximum). Now I'll use BigQuery for historical advance search.\nFor live data-cloudSQL will be used as we must focus on perfomance for fetched data.\nSome of performance issue will be there for historical search, when a user wants both results from live as well as historical data. (BigQuery is taking time near about 5-6 sec[or more] for worst case) But it will be optimized as per data and structure of the model.","Q_Score":1,"Tags":"python,google-app-engine,google-cloud-sql","A_Id":44715500,"CreationDate":"2017-06-20T13:14:00.000","Title":"Google CloudSQL : structuring history data on cloudSQL","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I'm using google cloudSQL for applying advance search on people data to fetch the list of users. In datastore, there are data already stored there with 2 model. First is used to track current data of users and other model is used to track historical timeline. The current data is stored on google cloudSQL are more than millions rows for all users. Now I want to implement advance search on historical data including between dates by adding all history data to cloud.  \nIf anyone can suggest the better structure for this historical model as I've gone through many of the links and articles. But cannot find proper solution as I have to take care of the performance for search (In Current search, the time is taken to fetch result is normal but when history is fetched, It'll scan all the records which causes slowdown of queries because of complex JOINs as needed). The query that is used to fetch the data from cloudSQL are made dynamically based on the users' need. For example, A user want the employees list whose manager is \"xyz.123@abc.in\" , by using python code, the query will built accordingly. Now a user want to find users whose manager WAS \"xyz.123@abc.in\" with effectiveFrom 2016-05-02 to 2017-01-01.\nAs I've find some of the usecases for structure as below:\n1) Same model as current structure with new column flag for isCurrentData (status of data whether it is history or active)\nDisadv.:\n - queries slowdown while fetching data as it will scan all records.\n   Duplication of data might increase.\nThese all disadv. will affect the performance of advance search by increasing time.\n    Solution to this problem is to partition whole table into diff tables.\n2) Partition based on year.\n   As time passes, this will generate too many tables.\n3) 2 tables might be maintained.\n   1st for current data and second one for history. But when user want to search data on both models will create complexity of build query.\nSo, need suggestions for structuring historical timeline with improved performance and effective data handling.\nThanks in advance.","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":81,"Q_Id":44654127,"Users Score":0,"Answer":"Depending on how often you want to do live queries vs historical queries and the size of your data set, you might want to consider placing the historical data elsewhere.\nFor example, if you need quick queries for live data and do many of them, but can handle higher-latency queries and only execute them sometimes, you might consider periodically exporting data to Google BigQuery. BigQuery can be useful for searching a large corpus of data but has much higher latency and doesn't have a wire protocol that is MySQL-compatible (although it's query language will look familiar to those who know any flavor of SQL). In addition, while for Cloud SQL you pay for data storage and the amount of time your database is running, in BigQuery you mostly pay for data storage and the amount of data scanned during your query executions. Therefore, if you plan on executing many of these historical queries it may get a little expensive.\nAlso, if you don't have a very large data set, BigQuery may be a bit of an overkill. How large is your \"live\" data set and how large do you expect your \"historical\" data set to grow over time? Is it possible to just increase the size of the Cloud SQL instance as the historical data grows until the point at which it makes sense to start exporting to Big Query?","Q_Score":1,"Tags":"python,google-app-engine,google-cloud-sql","A_Id":44662852,"CreationDate":"2017-06-20T13:14:00.000","Title":"Google CloudSQL : structuring history data on cloudSQL","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"Me and my group are currently working on a school project where we need to use an online python compiler, since we are not allowed to install or download any software on their computers. The project requires me to read data from a .xlsx file.\nIs there any online IDE with xlrd that can read the file that is on the school's computer?\nI've been looking at a few but can't seem to find any that has this support. On tutorialspoint.com it is possible to upload the excel file but not import xlrd. Other sites has xlrd but doesn't allow for uploading files to the site.","AnswerCount":3,"Available Count":2,"Score":-0.0665680765,"is_accepted":false,"ViewCount":2482,"Q_Id":44686664,"Users Score":-1,"Answer":"import tabula\nRead a PDF File\ndf = tabula.read_pdf(\"file:\/\/\/C:\/Users\/tanej\/Desktop\/salary.pdf\", pages='all')[0]\nconvert PDF into CSV\ntabula.convert_into(\"file:\/\/\/C:\/Users\/tanej\/Desktop\/salary.pdf\", \"file:\/\/\/C:\/Users\/tanej\/Desktop\/salary.csv\", output_format=\"csv\", pages='all')\nprint(df)","Q_Score":0,"Tags":"python,xlsx,xlrd,online-compilation","A_Id":72494283,"CreationDate":"2017-06-21T21:36:00.000","Title":"Read excel file with an online Python compiler with xlrd","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"Me and my group are currently working on a school project where we need to use an online python compiler, since we are not allowed to install or download any software on their computers. The project requires me to read data from a .xlsx file.\nIs there any online IDE with xlrd that can read the file that is on the school's computer?\nI've been looking at a few but can't seem to find any that has this support. On tutorialspoint.com it is possible to upload the excel file but not import xlrd. Other sites has xlrd but doesn't allow for uploading files to the site.","AnswerCount":3,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":2482,"Q_Id":44686664,"Users Score":0,"Answer":"Could the pandas package and its pandas.read_clipboard function help? You'd need to copy the content of the file manually to the clipboard before starting your script.\nAlternatively - is it considered cheating to just rent a server? Pretty cheap these days.\nFinally: you don't usually require admin rights to install Python... so assuming it's not a violation of school policy, the Anaconda distribution for instance is very happy to be installed for the local user only.","Q_Score":0,"Tags":"python,xlsx,xlrd,online-compilation","A_Id":44687122,"CreationDate":"2017-06-21T21:36:00.000","Title":"Read excel file with an online Python compiler with xlrd","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am trying to retrieve a large amount of data(more than 7 million) from database and trying to save a s flat file. The data is being retrieved using python code(python calls stored procedure). But I am having a problem here. The process is eating up so much of memory hence killing the process automatically by unix machine. I am using read_sql_query to read the data and to_csv to write into flat file. So, I wanted to ask if there is a way to solve this problem. May be reading only a few thousand rows at a time and saving them and go to next line.\nI even used chunksize parameter as well. But it does not seem to resolve the issue.\nAny help or suggestion will be greatly appreciated.","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":6717,"Q_Id":44706706,"Users Score":0,"Answer":"Rather than using the pandas library, make a database connection directly (using psycopg2, pymysql, pyodbc, or other connector library as appropriate) and use Python's db-api to read and write rows concurrently, either one-by-one or in whatever size chunks you can handle.","Q_Score":3,"Tags":"python,sql,pandas","A_Id":44707209,"CreationDate":"2017-06-22T18:15:00.000","Title":"Reading and writing large volume of data in Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a basic personal project website that I am looking to learn some web dev fundamentals with and database (SQL) fundamentals as well (If SQL is even the right technology to use??).\nI have the basic skeleton up and running but as I am new to this, I want to make sure I am doing it in the most efficient and \"correct\" way possible.\nCurrently the site has a main index (landing) page and from there the user can select one of a few subpages. For the sake of understanding, each of these sub pages represents a different surf break and they each display relevant info about that particular break i.e. wave height, wind, tide. \nAs I have already been able to successfully scrape this data, my main questions revolve around how would I go about inserting this data into a database for future use (historical graphs, trends)? How would I ensure data is added to this database in a continuous manner (once\/day)? How would I use data that was scraped from an earlier time, say at noon, to be displayed\/used at 12:05 PM rather than scraping it again?\nAny other tips, guidance, or resources you can point me to are much appreciated.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":181,"Q_Id":44714345,"Users Score":2,"Answer":"This kind of data is called time series. There are specialized database engines for time series, but with a not-extreme volume of observations - (timestamp, wave heigh, wind, tide, which break it is) tuples - a SQL database will be perfectly fine.\nTry to model your data as a table in Postgres or MySQL. Start by making a table and manually inserting some fake data in a GUI client for your database. When it looks right, you have your schema. The corresponding CREATE TABLE statement is your DDL. You should be able to write SELECT queries against your table that yield the data you want to show on your webapp. If these queries are awkward, it's a sign that your schema needs revision. Save your DDL. It's (sort of) part of your source code. I imagine two tables: a listing of surf breaks, and a listing of observations. Each row in the listing of observations would reference the listing of surf breaks. If you're on a Mac, Sequel Pro is a decent tool for playing around with a MySQL database, and playing around is probably the best way to learn to use one.\nNext, try to insert data to the table from a Python script. Starting with fake data is fine, but mold your Python script to read from your upstream source (the result of scraping) and insert into the table. What does your scraping code output? Is it a function you can call? A CSV you can read? That'll dictate how this script works.\nIt'll help if this import script is idempotent: you can run it multiple times and it won't make a mess by inserting duplicate rows. It'll also help if this is incremental: once your dataset grows large, it will be very expensive to recompute the whole thing. Try to deal with importing a specific interval at a time. A command-line tool is fine. You can specify the interval as a command-line argument, or figure out out from the current time.\nThe general problem here, loading data from one system into another on a regular schedule, is called ETL. You have a very simple case of it, and can use very simple tools, but if you want to read about it, that's what it's called. If instead you could get a continuous stream of observations - say, straight from the sensors - you would have a streaming ingestion problem.\nYou can use the Linux subsystem cron to make this script run on a schedule. You'll want to know whether it ran successfully - this opens a whole other can of worms about monitoring and alerting. There are various open-source systems that will let you emit metrics from your programs, basically a \"hey, this happened\" tick, see these metrics plotted on graphs, and ask to be emailed\/texted\/paged if something is happening too frequently or too infrequently. (These systems are, incidentally, one of the main applications of time-series databases). Don't get bogged down with this upfront, but keep it in mind. Statsd, Grafana, and Prometheus are some names to get you started Googling in this direction. You could also simply have your script send an email on success or failure, but people tend to start ignoring such emails.\nYou'll have written some functions to interact with your database engine. Extract these in a Python module. This forms the basis of your Data Access Layer. Reuse it in your Flask application. This will be easiest if you keep all this stuff in the same Git repository. You can use your chosen database engine's Python client directly, or you can use an abstraction layer like SQLAlchemy. This decision is controversial and people will have opinions, but just pick one. Whatever database API you pick, please learn what a SQL injection attack is and how to use user-supplied data in queries without opening yourself up to SQL injection. Your database API's documentation should cover the latter.\nThe \/ page of your Flask application will be based on a SQL query like SELECT * FROM surf_breaks. Render a link to the break-specific page for each one.\nYou'll have another page like \/breaks\/n where n identifies a surf break (an integer that increments as you insert surf break rows is customary). This page will be based on a query like SELECT * FROM observations WHERE surf_break_id = n. In each case, you'll call functions in your Data Access Layer for a list of rows, and then in a template, iterate through those rows and render some HTML. There are various Javascript and Python graphing libraries you can feed this list of rows into and get graphs out of (client side or server side). If you're interested in something like a week-over-week change, you should be able to express that in one SQL query and get that dataset directly from the database engine.\nFor performance, try not to get in a situation where more than one SQL query happens during a page load. By default, you'll be doing some unnecessary work by going back to the database and recomputing the page every time someone requests it. If this becomes a problem, you can add a reverse proxy cache in front of your Flask app. In your case this is easy, since nothing users do to the app cause its content to change. Simply invalidate the cache when you import new data.","Q_Score":0,"Tags":"python,sql,web,flask","A_Id":44715054,"CreationDate":"2017-06-23T06:20:00.000","Title":"Flask website backend structure guidance assistance?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a table in a PostgreSQL database.\nI'm writing data to this table (using some computation with Python and psycopg2 to write results down in a specific column in that table).    \nI need to update some existing cell of that column.\nTill now, I was able either to delete the complete row before writing this single cell because all other cells on the row were also written back as the same time, or delete the entire column for the same reason.    \nNow I can't do that anymore because that would mean long computation time to rebuild either the row or the column for only a few new values to be written in some cell.    \nI know the update command. It works well for that.\nBut, if I had existing values in some cells, and that a new computation gives me no more result for these cells, I would like to \"clear\" the existing values to keep the table up-to-date with the last computation I've done.    \nIs there a simple way to do that ? update doesn't seems to work (it seems to keep the old values).\nI precise again I'm using psycopg2 to write things to my table.","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":878,"Q_Id":44718379,"Users Score":1,"Answer":"you simple update the cell with the value NULL in SQL - psycopg2 will insert NULL into the database when you update your column with None-type from python.","Q_Score":0,"Tags":"python,sql,postgresql,psycopg2","A_Id":44718475,"CreationDate":"2017-06-23T09:50:00.000","Title":"Update field with no-value","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am trying to connect to a MySQL database using PyQt5 on Python 3.6 for 64-bit Windows. When I call QSqlDatabase.addDatabase('MYSQL') and run my utility, it shows up with this error message:\nQSqlDatabase: QMYSQL driver not loaded\nQSqlDatabase: available drivers: QSQLITE QMYSQL QMYSQL3 QODBC QODBC3 QP\nSQL QPSQL7\nThis confuses me since according to the error message, the QMYSQL driver is loaded. I installed PyQt through the default installer, so the MySQL plugin should be installed. Has anyone else experienced this problem or does someone know the cause of this?","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1820,"Q_Id":44753724,"Users Score":1,"Answer":"It said driver available but you need to rebuid a new Mysql driver base on Qt Source code and Mysql Library.","Q_Score":0,"Tags":"python,mysql,qt,pyqt","A_Id":44992670,"CreationDate":"2017-06-26T05:49:00.000","Title":"PyQt QSqlDatabase: QMYSQL driver not loaded","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"When I'm using pymysql to perform operations on MySQL database, it seems that all the operations are temporary and only visible to the pymysql connection, which means I can only see the changes through cur.execute('select * from qiushi') and once I cur.close() and conn.close() and log back in using pymysql, everything seems unchanged.\nHowever, when I'm looking at the incremental id numbers, it does increased, but I can't see the rows that were inserted from pymysql connection. It seems that they were automatically deleted?!\nSome of my code is here: \nimport pymysql\ntry:\n    conn = pymysql.connect(host='127.0.0.1',port=3306,user='pymysql',passwd='pymysql',charset='utf8')\n    cur = conn.cursor()\n    #cur.execute('CREATE TABLE qiushi (id INT NOT NULL AUTO_INCREMENT, content_id BIGINT(10) NOT NULL, content VARCHAR(1000), created TIMESTAMP DEFAULT CURRENT_TIMESTAMP, PRIMARY KEY(id));')\n    #cur.execute('DESCRIBE content')\n    #cur.fetchall()\n    cur.execute('USE qiushibaike')\n    for _ in range(0,len(content_ids)):\n        cur.execute(\"INSERT INTO qiushi (content,content_id) VALUES (\\\"%s\\\",%d)\"%(jokes[_],int(content_ids[_])))\nfinally:\n    cur.close()\n    conn.close()","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":377,"Q_Id":44756118,"Users Score":1,"Answer":"I solved the problem by myself...\nBecause the config is automatically committed, so after each SQL sentence we should commit the changes.\nApproach 1:\nadd cur.commit() after the cur.execute()\nApproach 2:\nedit the connection config, add autocommit=True","Q_Score":0,"Tags":"python,mysql,pymysql","A_Id":44758048,"CreationDate":"2017-06-26T08:56:00.000","Title":"Unable to INSERT with Pymysql (incremental id changes though)","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have some records data with \\n. When I do a SELECT query using psycopg2 the result comes with \\n escaped like this \\\\n. I want the result have literal \\n in order to use splitlines().","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":972,"Q_Id":44763758,"Users Score":0,"Answer":"The point is that values were edited with pgadmin3 (incorrectly, the correct way is shift+enter to add a new line). I asked the user to use phppgadmin (easier for him, multiline fields are edited with textarea control) and now everything is working properly.\nSo pyscopg2 WORKS fine, I'm sorry to thought it was the culprit.\nHe was putting literals \\n in order to put new lines.","Q_Score":2,"Tags":"python,python-3.x,psycopg2,psycopg","A_Id":44766725,"CreationDate":"2017-06-26T15:56:00.000","Title":"I don't want psycopg2 to escape new line character (\\n) in query result","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have some records data with \\n. When I do a SELECT query using psycopg2 the result comes with \\n escaped like this \\\\n. I want the result have literal \\n in order to use splitlines().","AnswerCount":2,"Available Count":2,"Score":-0.0996679946,"is_accepted":false,"ViewCount":972,"Q_Id":44763758,"Users Score":-1,"Answer":"Try this: object.replace(\"\\\\n\", r\"\\n\")\nHope this helped :)","Q_Score":2,"Tags":"python,python-3.x,psycopg2,psycopg","A_Id":44763994,"CreationDate":"2017-06-26T15:56:00.000","Title":"I don't want psycopg2 to escape new line character (\\n) in query result","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I wanna migrate from sqlite3 to MySQL in Django. Now I have been working in Oracle, MS Server and I know that I can make Exception to try over and over again until it is done... However this is insert in a same table where the data must be INSERTED right away because users will not be happy for waiting their turn on INSERT on the same table.\nSo I was wondering, will the deadlock happen on table if to many users make insert in same time and what should I do to bypass that, so that users don't sense it?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":397,"Q_Id":44789046,"Users Score":1,"Answer":"I don't think you can get deadlock just from rapid insertions. Deadlock occurs when you have two processes that are each waiting for the other one to do something before they can make the change that the other one is waiting for. If two processes are just inserting, the database will simply process them in the order that they're received, there's no dependency between them.\nIf you're using InnoDB, it uses row-level locking. So unless two inserts both try to insert the same unique key, they shouldn't even lock each other out, they can be done concurrently.","Q_Score":1,"Tags":"python,mysql,django","A_Id":44789450,"CreationDate":"2017-06-27T20:10:00.000","Title":"MySql: will it deadlock on to many insert - Django?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have one program that downloads time series (ts) data from a remote database and saves the data as csv files. New ts data is appended to old ts data. My local folder continues to grow and grow and grow as more data is downloaded. After downloading new ts data and saving it, I want to upload it to a Google BigQuery table. What is the best way to do this? \nMy current work-flow is to download all of the data to csv files, then to convert the csv files to gzip files on my local machine and then to use gsutil to upload those gzip files to Google Cloud Storage. Next, I delete whatever tables are in Google BigQuery and then manually create a new table by first deleting any existing table in Google BigQuery and then creating a new one by uploading data from Google Cloud Storage. I feel like there is room for significant automation\/improvement but I am a Google Cloud newbie. \nEdit: Just to clarify, the data that I am downloading can be thought of downloading time series data from Yahoo Finance. With each new day, there is fresh data that I download and save to my local machine. I have to uploading all of the data that I have to Google BigQUery so that I can do SQL analysis on it.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":642,"Q_Id":44804051,"Users Score":1,"Answer":"Consider breaking up your data into daily tables (or partitions). Then you only need to upload the CVS from the current day.\nThe script you have currently defined otherwise seems reasonable.\n\nExtract your new day of CSVs from your source of timeline data.\nGzip them for fast transfer.\nCopy them to GCS.\nLoad the new CVSs into the current daily table\/partition.\n\nThis avoids the need to delete existing tables and reduces the amount of data and processing that you need to do. As a bonus, it is easier to backfill a single day if there is an error in processing.","Q_Score":0,"Tags":"python,pandas,google-bigquery,google-cloud-platform,gsutil","A_Id":44814853,"CreationDate":"2017-06-28T13:34:00.000","Title":"Python\/Pandas\/BigQuery: How to efficiently update existing tables with a lot of new time series data?","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"i'm developing an app for my company, using Python2.7 and MariaDB. I have created a functions which backups our main database server to another database server. I use this command to do it:mysqldump -h localhost -P 3306 -u root -p mydb | mysql -h bckpIPsrv -P 3306 -u root -p mydb2 .\n  I want to know if it's posible to see some kind of verbose mode or a percentage of the job and display it on screen.\nthank you.","AnswerCount":2,"Available Count":1,"Score":-0.0996679946,"is_accepted":false,"ViewCount":6336,"Q_Id":44824517,"Users Score":-1,"Answer":"dumpcmd = \"mysqldump -h \" + DB_HOST + \" -u \" + DB_USER + \" -p\" + DB_USER_PASSWORD + \" \" + DB_NAME + \"| pv | gzip > \" + pipes.quote(\n    BACKUP_PATH) + \"\/\" + FILE_NAME + \".sql\"","Q_Score":2,"Tags":"mysql,python-2.7,mariadb","A_Id":54635754,"CreationDate":"2017-06-29T11:57:00.000","Title":"is there a way to have mysqldump progress bar which shows the users the status of their backups?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Trying to install a postgresql database which resides on Azure for my python flask application; but the installation of psycopg2 package requires the pg_config file which comes when postgresql is installed. So how do I export the pg_config file from the postgresql database which also resides on azure? Is pg_config all psycopg2 need for a successful installation?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":164,"Q_Id":44911066,"Users Score":2,"Answer":"You don't need the specific pg_config from the target database. It's only being used to compile against libpq, the client library for PostgreSQL, so you only need the matching PostgreSQL client installed on your local machine.\nIf you're on Windows I strongly advise you to install a pre-compiled PostgreSQL. You can just install the whole server, it comes with the client libraries.\nIf you're on Linux, you'll probably need the PostgreSQL -devel or -dev package that matches your PostgreSQL version.","Q_Score":0,"Tags":"python,postgresql,azure,psycopg2","A_Id":44915875,"CreationDate":"2017-07-04T16:59:00.000","Title":"How to retrieve the pg_config file from Azure postgresql Database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"What I want is execute the sql \nselect * from articles where author like \"%steven%\".\nFor the sake of safety, i used like this way :\n\ncursor.execute('select * from articles where %s like %s', ('author', '%steven%')\n\nThen the result is just empty, not get a syntax error, but just empty set.\nBut I am pretty sure there is some thing inside, I can get result use the first sql. Is there anything run with my code ?","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":221,"Q_Id":44937003,"Users Score":1,"Answer":"The problem here is fact a minor mistake. Thanks to @Asad Saeeduddin, when I try to use print cursor._last_executed to check what has happened. I found that what is in fact executed is \nSELECT * FROM articles WHERE 'title' LIKE '%steven%', look the quotation mark around the title, that's the reason why I got empty set.\nSo always remember the string after formatting will have a quotation around","Q_Score":1,"Tags":"python,mysql,pymysql","A_Id":44937097,"CreationDate":"2017-07-05T22:30:00.000","Title":"Could not format sql correctly in pymysql","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am relatively new to Django.\nI have managed to create a basic app and all that without problems and it works fine.\nThe question probably has been asked before.\nIs there a way to update existing Django models already mapped to existing databases when the underlying database is modified?\nTo be specific, I have mysql database that I use for my Django app as well as some standalone python and R scripts. Now, it is much easier to update the mysql database with, say, daily stock prices, everyday from my existing scripts outside Django models. Ideally, what I would like is to have my Django models that are already mapped to these tables to reflect the updated data.\nI know there is $ python manage.py inspectdb for creating models from existing databases. But that is not the objective.\nFrom what I have gathered so far from the docs and online searches, it is imperative to update the backend database through Django models. Not outside of it. Is it the case really? As long as the table structure doesn;t change I really don't see the why this should not be allowed. Database is meant to serve multiple customers isn't it? With Django being one of it.\nAnd I can not provide a reproducible example as it is a conceptual question.\nIf this functionality doesn't exist, imho, it really should.\nThanks,\nKaustubh","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":514,"Q_Id":44954521,"Users Score":4,"Answer":"You don't need to update models if you just added new data. Models are related to a database structure only.","Q_Score":1,"Tags":"python,django,django-models","A_Id":44954903,"CreationDate":"2017-07-06T16:33:00.000","Title":"Django models update when backend database updated","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm working with Pycharm in a project to read SQL DBs ,I'm working in a windows 10 64bits workstation and I'm trying to install the module pymssql, I have already installed VS2015 to get all requirements but now each time that i try to install i got the message:\nerror: command 'C:\\Program Files (x86)\\Microsoft Visual Studio 14.0\\VC\\BIN\\cl.exe' failed with exit status 2\nI saw on message details the error in:\n  _mssql.c(266): fatal error C1083: Cannot open include file: 'sqlfront.h': No such file or directory\nHow can i figured it out?  thanks","AnswerCount":5,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":3976,"Q_Id":44955927,"Users Score":0,"Answer":"I had a same problem but its fixed this way.\nCopied \"rc.exe\" and \"rcdll.dll\" from \"C:\\Program Files (x86)\\Windows Kits\\8.1\\bin\\x86\"\nPasted \"C:\\Program Files (x86)\\Microsoft Visual Studio 14.0\\VC\\bin\"","Q_Score":4,"Tags":"sql,python-3.x,pycharm","A_Id":50968882,"CreationDate":"2017-07-06T17:57:00.000","Title":"Install pymssql 2.1.3 in Pycharm","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm working with Pycharm in a project to read SQL DBs ,I'm working in a windows 10 64bits workstation and I'm trying to install the module pymssql, I have already installed VS2015 to get all requirements but now each time that i try to install i got the message:\nerror: command 'C:\\Program Files (x86)\\Microsoft Visual Studio 14.0\\VC\\BIN\\cl.exe' failed with exit status 2\nI saw on message details the error in:\n  _mssql.c(266): fatal error C1083: Cannot open include file: 'sqlfront.h': No such file or directory\nHow can i figured it out?  thanks","AnswerCount":5,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":3976,"Q_Id":44955927,"Users Score":0,"Answer":"In my case helped me rollback to Python 3.8. Same problem I had on 3.10 x64","Q_Score":4,"Tags":"sql,python-3.x,pycharm","A_Id":69630619,"CreationDate":"2017-07-06T17:57:00.000","Title":"Install pymssql 2.1.3 in Pycharm","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am new to pyspark. I want to plot the result using matplotlib, but not sure which function to use. I searched for a way to convert sql result to pandas and then use plot.","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":30940,"Q_Id":45003301,"Users Score":1,"Answer":"For small data, you can use .select() and .collect() on the pyspark DataFrame. collect will give a python list of pyspark.sql.types.Row, which can be indexed. From there you can plot using matplotlib without Pandas, however using Pandas dataframes with df.toPandas() is probably easier.","Q_Score":15,"Tags":"python,pandas,matplotlib,pyspark-sql","A_Id":66233233,"CreationDate":"2017-07-10T03:15:00.000","Title":"How to use matplotlib to plot pyspark sql results","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am trying to write a data migration script moving data from one database to another (Teradata to snowflake) using JDBC cursors.\nThe table I am working on has about 170 million records and I am running into the issue where when I execute the batch insert a maximum number of expressions in a list exceeded, expected at most 16,384, got 170,000,000.\nI was wondering if there was any way around this or if there was a better way to batch migrate records without exporting the records to a file and moving it to s3 to be consumed by the snowflake.","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":215,"Q_Id":45012005,"Users Score":1,"Answer":"If your table has 170M records, then using JDBC INSERT to Snowflake is not feasible.   It would perform millions of separate insert commands to the database, each requiring a round-trip to the cloud service, which would require hundreds of hours.\nYour most efficient strategy would be to export from Teradata into multiple delimited files -- say with 1 - 10 million rows each.  You can then either use the Amazon's client API to move the files to S3 using parallelism, or use Snowflake's own PUT command to upload the files to Snowflake's staging area for your target table.  Either way, you can then load the files very rapidly using Snowflake's COPY command once they are in your S3 bucket or Snowflake's staging area.","Q_Score":1,"Tags":"python,jdbc,teradata,snowflake-cloud-data-platform","A_Id":46125739,"CreationDate":"2017-07-10T12:25:00.000","Title":"JDBC limitation on lists","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Background:\nI have an application written in Python to monitor the status of tools. The tools send their data from specific runs and it all gets stored in an Oracle database as JSON files.\nMy Problem\/Solution:\nInstead of connecting to the DB and then querying it repeatedly when I want to compare the current run data to the previous run's data, I want to make a copy of the database query so that I can compare the new run data to the copy that I made instead of to the results of the query.\nThe reason I want to do this is because constantly querying the server for the previous run's data is slow and puts unwanted load\/usage on the server.\nFor the previous run's data there are multiple files associated with it (because there are multiple tools) and therefore each query has more than one file that would need to be copied. Locally storing the copies of the files in the query is what I intended to do, but I was wondering what the best way to go about this was since I am relativity new to doing something like this.\n\nSo any help and suggestions on how to efficiently store the results of a query, which are multiple JSON files, would be greatly appreciated!","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":465,"Q_Id":45036714,"Users Score":1,"Answer":"As you described querying the db too many times is not an option. OK in that case I would do this the following way :\nWhen your program starts you get the data for all tools as a set of JSON-Files per tool right? OK. I am not sure how you get the data by querying the tools directly or by querying the db .. does not matter.\nYou check if you have old data in the \"cache-dictionary\" for that tool. If yes do your compare and store the \"new data\" as \"previous data\" in the cache. Ready for the next run. Do this for all tools. This loops forever :-)\nThis \"cache dictionary\" now can be implemented in memory or on disk. For your amount of data I think memory is just fine.\nWith that approach you do not have to query the db for the old data. The case that you cannot do the compare if you do not have old data in the \"cache\" at program start could be handled that you try to get it from db (risking long query times but what to do :-)","Q_Score":1,"Tags":"python,json,database,oracle","A_Id":45044543,"CreationDate":"2017-07-11T14:00:00.000","Title":"How To Store Query Results (Using Python)","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Currently we are uploading the data retrieved from vendor APIs into Google Datastore. Wanted to know what is the best approach with data storage and querying the data. \nI will be need to query millions of rows of data and will be extracting custom engineered features from the data. So wondering whether I should load the data into BigQuery directly and query it for faster processing or store it in Datastore and then move it to BigQuery for querying?. I will be using pandas for performing statistics on stored data.","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":577,"Q_Id":45061306,"Users Score":0,"Answer":"As far as I can tell there is no support for Datastore in Pandas. This might affect your decision.","Q_Score":0,"Tags":"python,pandas,google-cloud-datastore,google-bigquery,google-cloud-platform","A_Id":45395282,"CreationDate":"2017-07-12T15:00:00.000","Title":"Is Google Cloud Datastore or Google BigQuery better suited for analytical queries?","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am trying to export data from Aurora into S3, I have created a stored procedure to perform this action. I can schedule this on the Aurora Scheduler to run at a particular point in time.\nHowever, I have multiple tables - could go up to 100; so I want my process controller which is a python script sitting in Lambda to send a Queue Message - Based on this Queue message the stored procedure in Aurora will be started\nI am looking at this for the following reasons\n\nI do not want too much time lag between starting two exports\nI also do not want two exports overlapping in execution time","AnswerCount":3,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":679,"Q_Id":45098004,"Users Score":0,"Answer":"There isn't any built-in integration that allows SQS to interact with Aurora.\nObviously you can do this externally, with a queue consumer that reads from the queue and invokes the procedures, but that doesn't appear to be relevant, here.","Q_Score":0,"Tags":"python,amazon-web-services,amazon-sqs,amazon-aurora","A_Id":45124304,"CreationDate":"2017-07-14T08:14:00.000","Title":"Does anyone know if we can start a storedprocedure in Aurora based on SQS","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am trying to export data from Aurora into S3, I have created a stored procedure to perform this action. I can schedule this on the Aurora Scheduler to run at a particular point in time.\nHowever, I have multiple tables - could go up to 100; so I want my process controller which is a python script sitting in Lambda to send a Queue Message - Based on this Queue message the stored procedure in Aurora will be started\nI am looking at this for the following reasons\n\nI do not want too much time lag between starting two exports\nI also do not want two exports overlapping in execution time","AnswerCount":3,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":679,"Q_Id":45098004,"Users Score":0,"Answer":"I have used lambda with alembic package to create schema and structures. I know we could create users and execute other database commands - the same way execute a stored procedure \nLambda could prove to be expensive - we probably could have an container to do it","Q_Score":0,"Tags":"python,amazon-web-services,amazon-sqs,amazon-aurora","A_Id":55167030,"CreationDate":"2017-07-14T08:14:00.000","Title":"Does anyone know if we can start a storedprocedure in Aurora based on SQS","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"In my pyramid app it's useful to be able to log in as any user (for test\/debug, not in production). My normal login process is just a simple bcrypt check against the hashed password.\nWhen replicating user-submitted bug reports I found it useful to just clone the sqlite database and run a simple script which would change everyone's password to a fixed string (just for local testing). Now that I'm switching over to postgresql that's less convenient to do, and I'm thinking of installing a backdoor to my login function.\nBasically I wish to check os.environ (set from the debug.wsgi file which is loaded by apache through mod_wsgi) for a particular variable 'debug'. If it exists then I will allow login using any password (for any user), bypassing the password check.\nWhat are the security implications of this? As I understand it, the wsgi file is sourced once when apache loads up, so if the production.wsgi file does not set that particular variable, what's the likelihood of an attacker (or incompetent user) spoofing it?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":64,"Q_Id":45112983,"Users Score":1,"Answer":"In order to instantiate the server application with that debug feature in environment, the attacker would have to have the hand over your webserver, most probably with administrative privileges.\nFrom an outside process, an attacker cannot modify the environment of the running server, which is loaded into memory, without at least debug capabilities and a good payload for rewriting memory. It would be easier to just reload the server or try executing a script within it.\nI think you are safe the way you go. If you are paranoid, ensure to isolate (delete) the backdoor from the builds to production.","Q_Score":2,"Tags":"python,security,pyramid,environment,dev-to-production","A_Id":45113051,"CreationDate":"2017-07-14T23:42:00.000","Title":"Security implications of a pyramid\/wsgi os.environ backdoor?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm sending data back and forth Python and Cassandra. I'm using both builtin  float types in my python program and the data type for my Cassandra table. If I send a number 955.99 from python to Cassandra, in the database it shows 955.989999. When I send a query in python to return the value I just sent, it is now 955.989990234375.\nI understand the issue with precision loss in python, I just wanted to know if there's any built-in mechanisms in Cassandra that could prevent this issue.","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":639,"Q_Id":45139240,"Users Score":1,"Answer":"Also if you cannot change your column definition for some reason, converting your float value to string and passing str to the cassandra-driver will also solve your problem. \nIt will be able to generate the precise decimal values form str.","Q_Score":4,"Tags":"python,cassandra,floating-point,precision,cassandra-python-driver","A_Id":50065729,"CreationDate":"2017-07-17T08:23:00.000","Title":"Python Cassandra floating precision loss","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a python script that execute a gbq job to import a csv file from Google cloud storage to an existing table on BigQuery.\nHow can I set the job properties to import to the right columns provided in the first row of the csv file? \nI set parameter 'allowJaggedRows' to TRUE, but it import columns in order regardless of column names in the header of csv file.","AnswerCount":1,"Available Count":1,"Score":0.3799489623,"is_accepted":false,"ViewCount":3297,"Q_Id":45155117,"Users Score":2,"Answer":"When you import a CSV into BigQuery the columns will be mapped in the order the CSV presents them - the first row (titles) won't have any effect in the order the subsequent rows are read. \nTo be noted, if you were importing JSON files, then BigQuery would use the name of each column, ignoring the order.","Q_Score":0,"Tags":"python,google-bigquery,import-from-csv","A_Id":45156763,"CreationDate":"2017-07-17T23:23:00.000","Title":"How to import CSV to an existing table on BigQuery using columns names from first row?","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I need to store json objects on the google cloud platform.  I have considered a number of options:\n\nStore them in a bucket as a text (.json) file.\nStore them as text in datastore using json.dumps(obj).\nUnpack it into a hierarchy of objects in datastore.\n\nOption 1: Rejected because it has no organising principles other than the filename and cannot be searched across.\nOption 2: Is easy to implement, but you cannot search using dql.\nOption 3: Got it to work after a lot of wrangling with the key and parent key structures.  While it is searchable, the resulting objects have been split up and held together by the parent key relationships.  It is really ugly!\nIs there any way to store and search across a deeply structured json object on the google cloud platform - other than to set up mongodb in a compute instance?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1421,"Q_Id":45184482,"Users Score":0,"Answer":"I don't know what your exact searching needs are, but the datastore API allows for querying that is decently good, provided you give the datastore the correct indexes. Plus it's very easy to go take the entities in the datastore and pull them back out as .json files.","Q_Score":1,"Tags":"json,python-2.7,google-app-engine,google-cloud-datastore","A_Id":45204510,"CreationDate":"2017-07-19T08:05:00.000","Title":"Storing json objects in google datastore","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":1,"Web Development":1},{"Question":"I encountered the following irregularities and wanted to share my solution.\nI'm reading a sql table from Microsoft SQL Server in Python using Pandas and SQLALCHEMY. There is a column called \"occurtime\" with the following format: \"2017-01-01 01:01:11.000\". Using SQLAlchemy to read the \"occurtime\" column, everything was returned as NaN. I tried to set the parse_date parameter in the pandas.read_sql() method but with no success. \nIs anyone else encountering issue reading a datetime column from a SQL table using SQLAlchemy\/Pandas?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":752,"Q_Id":45197851,"Users Score":0,"Answer":"I had to work around the datetime column from my SQL query itself just so SQLAlchemy\/Pandas can stop reading it as a NaN value. \nIn my SQL query, I used CONVERT() to convert the datetime column to a string. This was ready with no issue, and then I used pandas.to_datetime() to convert it back into datetime. \nAnyone else with a better solution or know what's really going on, please share your answer, I'd really appreciate it!!!","Q_Score":0,"Tags":"python,sql-server,pandas,sqlalchemy","A_Id":45197852,"CreationDate":"2017-07-19T17:59:00.000","Title":"Pandas read_sql","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"As a user of the database, are there any quicker ways of exporting data from Filemaker using languages like python or java? Perhaps to an Excel.\nMy job involves exporting selected data constantly from our company's Filemaker database. However, the software is super slow, and the design of our app is bad which makes selecting which data to export a pain. (I have to manually select data one by one by opening the full record of each data. There's no batch export function.)\nPlease provide me with alternative methods. I feel very stupid in doing this.","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1900,"Q_Id":45205162,"Users Score":0,"Answer":"You can also save records as a spreadsheet for use in Microsoft Excel. For more information, see Saving and sending records as an Excel file in the FileMaker Help file. Use export when you want to export records in the current found set or export in a format other than an Excel spreadsheet. Use Save as Excel when you want to create an Excel spreadsheet that contains all the fields you have access to on the current layout.\nIf your FileMaker Pro source file contains summary fields, you can group by a sorted field in order to export subsummary values, such as subtotals generated by a report with grouped data. This process exports one record for each group. For example, if you have a report that totals sales by region, you can export one summary value for each region.","Q_Score":1,"Tags":"python,database,excel,filemaker,data-extraction","A_Id":45215938,"CreationDate":"2017-07-20T04:25:00.000","Title":"Any quick way to export data from Filemaker?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I need to send keys to excel to refresh formulas.\nWhat are my best options?\nI am already using Openpyxl but it does not satisfy all my needs.","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":1564,"Q_Id":45225010,"Users Score":1,"Answer":"If this still helps, you can use from pywin32 (which should be a default package) to use win32com.client.\nSample code:\nimport win32com.client\nxl = win32com.client.Dispatch(\"Excel.Application\")\nxl.sendkeys(\"^+s\")  # saves file\n\nUse \"%\" to access alt so you can get hotkeys.","Q_Score":1,"Tags":"python,excel,keyboard","A_Id":55856869,"CreationDate":"2017-07-20T20:56:00.000","Title":"Using python to send keys to active Excel Window","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am developing a skill for Amazon Alexa and I'm using DynamoDB for storing information about the users favorite objects. I would like 3 columns in the database:\n\nAlexa userId\nObject\nColor\n\nI currently have the Alexa userId as the primary key. The problem that I am running into is that if I try to add an entry into the db with the same userId, it overwrites the entry already in there. How can I allow a user to have multiple objects associated with them in the db by having multiple rows? I want to be able to query the db by the userId and receive all the objects that they have specified. \nIf I create a unique id for every entry, and there are multiple users, I can't possibly know the id to query by to get the active users' objects.","AnswerCount":5,"Available Count":2,"Score":0.0399786803,"is_accepted":false,"ViewCount":10290,"Q_Id":45227546,"Users Score":1,"Answer":"DynamoDB is a NoSQL-like, document database, or key-value store; that means, you may need to think about your tables differently from RDBMS. From what I understand from your question, for each user, you want to store information about their preferences on a list of objects; therefore, keep your primary key simple, that is, the user ID. Then, have a singe \"column\" where you store all the preferences. That can either be a list of of tuples (object,color) OR a dictionary of unique {object:color}.\nWhen you explore the items in the web UI, it will show these complex data structures as json-like documents which you can expand as you will.","Q_Score":9,"Tags":"python,amazon-web-services,amazon-dynamodb,alexa-skills-kit","A_Id":45266031,"CreationDate":"2017-07-21T01:26:00.000","Title":"How to create multiple DynamoDB entries under the same primary key?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am developing a skill for Amazon Alexa and I'm using DynamoDB for storing information about the users favorite objects. I would like 3 columns in the database:\n\nAlexa userId\nObject\nColor\n\nI currently have the Alexa userId as the primary key. The problem that I am running into is that if I try to add an entry into the db with the same userId, it overwrites the entry already in there. How can I allow a user to have multiple objects associated with them in the db by having multiple rows? I want to be able to query the db by the userId and receive all the objects that they have specified. \nIf I create a unique id for every entry, and there are multiple users, I can't possibly know the id to query by to get the active users' objects.","AnswerCount":5,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":10290,"Q_Id":45227546,"Users Score":0,"Answer":"you cannot create multiple entries with same primary key. Please create composite keys (multiple keys together as primary key). Please note you cannot have multiple records of same combination","Q_Score":9,"Tags":"python,amazon-web-services,amazon-dynamodb,alexa-skills-kit","A_Id":45693902,"CreationDate":"2017-07-21T01:26:00.000","Title":"How to create multiple DynamoDB entries under the same primary key?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"As far as I know Django apps can't start if any of the databases set in the settings.py are down at the start of the application. Is there anyway to make Django \"lazyload\" the initial database connection? \nI have two databases configured and one of them is a little unstable and sometimes it can be down for some seconds, but it's only used for some specific use cases of the application. As you can imagine I don't want that all the application can't start because of that. Is there any solution for that?\nI'm using Django 1.6.11, and we also use Django South for database migrations (in case that it's related somehow).","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":2860,"Q_Id":45240311,"Users Score":1,"Answer":"I did some more tests and problem only happens when you are using de development server python manage.py runserver. In that case, it forces a connection with the database.\nUsing an actual WSGI server it doesn't happen as @Alasdair informed.\n@JohnMoutafis in the end I didn't test your solution, but that could work.","Q_Score":6,"Tags":"python,mysql,django,django-models,django-south","A_Id":45638008,"CreationDate":"2017-07-21T14:32:00.000","Title":"Django: How to disable Database status check at startup?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I use Django 1.11, PostgreSQL 9.6 and Django migration tool. I couldn't have found a way to specify the column orders. In the initial migration, changing the ordering of the fields is fine but what about migrations.AddField() calls? AddField calls can also happen for the foreign key additions for the initial migration. Is there any way to specify the ordering or am I just obsessed with the order but I shouldn't be? \nUpdate after the discussion\nPostgreSQL DBMS doesn't support positional column addition. So it is practically meaningless to expect this facility from the migration tool for column addition.","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":5299,"Q_Id":45261303,"Users Score":11,"Answer":"AFAIK, there's no officially supported way to do this, because fields are supposed to be atomic and it shouldn't be relevant. However, it messes with my obsessive-compulsive side as well, and I like my columns to be ordered for when I need to debug things in dbshell, for example. Here's what I've found you can do:\n\nMake a migration with python manage.py makemigrations\nEdit the migration file and reorder the fields in migrations.createModel\n\nGood luck!","Q_Score":5,"Tags":"python,django,postgresql,django-models,migration","A_Id":45261424,"CreationDate":"2017-07-23T03:45:00.000","Title":"Django Migration Database Column Order","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I use Django 1.11, PostgreSQL 9.6 and Django migration tool. I couldn't have found a way to specify the column orders. In the initial migration, changing the ordering of the fields is fine but what about migrations.AddField() calls? AddField calls can also happen for the foreign key additions for the initial migration. Is there any way to specify the ordering or am I just obsessed with the order but I shouldn't be? \nUpdate after the discussion\nPostgreSQL DBMS doesn't support positional column addition. So it is practically meaningless to expect this facility from the migration tool for column addition.","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":5299,"Q_Id":45261303,"Users Score":0,"Answer":"I am not 100% sure about the PostgreSQL syntax but this is what it looks like in SQL after you have created the database. I'm sure PostgreSQL would have an equivalent:\nALTER TABLE yourtable.yourmodel \nCHANGE COLUMN columntochange columntochange INT(11) NOT NULL AFTER columntoplaceunder;\nOr if you have a GUI (mysql workbench in my case) you can go to the table settings and simply drag and drop colums as you wish and click APPLY.","Q_Score":5,"Tags":"python,django,postgresql,django-models,migration","A_Id":59406349,"CreationDate":"2017-07-23T03:45:00.000","Title":"Django Migration Database Column Order","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a django sql explorer which is running with 5 queries and 3 users.\n\nQuery1\nQuery2 \nQuery3 \nQuery4 \nQuery5\n\nI want to give access of Query1 and Query5 to user1 \nand Query4 and Query2 to user2 and likewise.\nmy default url after somebody logins is url\/explorer\nbased on users permission he should see only those queries but as of now all users can see all queries,\nI tried to search stackoverflow and also other places through google but there is no direct answer. Can someone point me to right resource or help me with doing this.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":233,"Q_Id":45320643,"Users Score":0,"Answer":"It's not possible to do with default implementation. You need to download the source code and customize as per your needs.","Q_Score":1,"Tags":"mysql,django,python-2.7","A_Id":47134025,"CreationDate":"2017-07-26T07:50:00.000","Title":"django sql explorer - user based query access","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am writing a small program in python with pywin32 that manipulates some data in excel and I want to hide a row in order to obscure a label on one of my pivot tables.\nAccording to MSDN the proper syntax is\n\nWorksheet.Rows ('Row#').EntireRow.Hidden = True\n\nWhen I try this in my code nothing happens - no error, nor hidden row. I have tried every combination I can think of of ranges to try and feed it but it will not hide the row in the output files.\nAnyone know of a solution to this or if it is not handled by pywin?\nEDIT:\nUpon further debugging, I am finding that when I immediately check, the row's Hidden value is True but when I reach the save point the row is no longer hidden (another print reveals Hidden = False)","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":1117,"Q_Id":45334926,"Users Score":0,"Answer":"I'm not familiar with python syntax, but in VBA you dont put quotes around the row number... Ex: myWorksheet.Rows(10).EntireRow.Hidden = True","Q_Score":3,"Tags":"python,excel,vba,winapi,pywin32","A_Id":45335421,"CreationDate":"2017-07-26T18:33:00.000","Title":"Hide row in excel not working - pywin32","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am writing a small program in python with pywin32 that manipulates some data in excel and I want to hide a row in order to obscure a label on one of my pivot tables.\nAccording to MSDN the proper syntax is\n\nWorksheet.Rows ('Row#').EntireRow.Hidden = True\n\nWhen I try this in my code nothing happens - no error, nor hidden row. I have tried every combination I can think of of ranges to try and feed it but it will not hide the row in the output files.\nAnyone know of a solution to this or if it is not handled by pywin?\nEDIT:\nUpon further debugging, I am finding that when I immediately check, the row's Hidden value is True but when I reach the save point the row is no longer hidden (another print reveals Hidden = False)","AnswerCount":2,"Available Count":2,"Score":0.0996679946,"is_accepted":false,"ViewCount":1117,"Q_Id":45334926,"Users Score":1,"Answer":"Turns out that a cell merge later in my program was undoing the hidden row - despite the fact that the merged cells were not in the hidden row.","Q_Score":3,"Tags":"python,excel,vba,winapi,pywin32","A_Id":45335753,"CreationDate":"2017-07-26T18:33:00.000","Title":"Hide row in excel not working - pywin32","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"What I can observe:\n\nI am using windows 7 64bit My code (establish an odbc connection with\na SQL server on the network, simple reading operations only) is\nwritten in python 3.6.2 32bit \nI pip installed pyodbc, so I assume that was 32bit as well. \nI downloaded and installed the 64bit \"Microsoft\u00ae ODBC Driver 13.1 for SQL Server\u00ae\" from microsoft website.\nMy python code connects to\nother computers on the network, which run server2003 32bit and either SQL Server 2005(32bit) or sql2008(32bit).\n\nThe setup works.\nMoreover: cursory test shows that, the above setup can successfully connect to a computer with Microsoft server2008(64bit) running sql2012(64bit) with the configuration under \"SQL Server Network Connection (32bit)\" being empty (meaing, the 32bit dll is missing), while the default 64 bit network connection configuration contains the usual config options like ip adress and listening port info.\nMy own explanation: \n[1] the client and the server's OS and ODBC interfaces can be of any 32\/64 bit combination, but the protocol that travels thru the network between my computer and the sql computer will be identical.\n[2] 32 bit python+pyodbc can talk to microsoft's 64bit odbc driver, because... 32 bit python knows how to use a 64 bit DLL...?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1620,"Q_Id":45362440,"Users Score":1,"Answer":"A 32bit application can NOT invoke a 64bit dll, so python 32bit can not talk to a 64bit driver for sure.\nmsodbc driver for sql server is in essence a dll file: msodbcsql13.dll\nI just found out (which is not even mentioned by microsoft) that \"odbc for sql server 13.1 x64\" will install a 64bit msodbcsql13.dll in system32 and a 32bit msodbcsql13.dll in SysWOW64 ( 32bit version of \"system32\" on a 64bit windows system)\nI can not however be certain that the network protocol between a 32bit client talking to 64bit sql server will be the same as a 64bit client talking to a 64bit sql server. But, I believe that, once a request is put on the network by the client to the server, 32bit or 64bit doesn't matter anymore. Someone please comment on this","Q_Score":0,"Tags":"python-3.x,odbc,driver,32bit-64bit,pyodbc","A_Id":45365583,"CreationDate":"2017-07-27T23:12:00.000","Title":"32bit pyodbc for 32bit python (3.6) works with microsoft's 64 bit odbc driver. Why?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have web application which made by symfony2(php framework)\nSo there is mysql database handled by doctrine2 php source code.\nNow I want to control this DB from python script.\nOf course I can access directly to DB from python.\nHowever, it is complex and might break the doctrine2 rule.\nIs there a good way to access database via php doctrine from python??","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":153,"Q_Id":45371167,"Users Score":0,"Answer":"You can try the Django ORM or SQL Alchemy but the configuration of the models have to be done very carefully. Maybe you can write a parser from Doctrine2 config files to Django models. If you do, open source it please.","Q_Score":0,"Tags":"php,python,symfony,frameworks","A_Id":45375722,"CreationDate":"2017-07-28T10:31:00.000","Title":"How to access doctrine database made by php from python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"AFAIU and from docs, RealDictCursor is a specialized DictCursor that enables to access columns only from keys (aka columns name), whereas DictCursor enables to access data both from keys or index number.\nI was wondering why RealDictCursor has been implemented if DictCursor offers more flexibility? Is it performance-wise (or memory-wise) so different (in favor of RealDictCursor I imagine...)?\nIn other words, what are RealDictCursor use cases vs DictCursor?","AnswerCount":2,"Available Count":1,"Score":-0.0996679946,"is_accepted":false,"ViewCount":14075,"Q_Id":45399347,"Users Score":-1,"Answer":"class psycopg2.extras.RealDictCursor(*args, **kwargs)\nA cursor that uses a real dict as the base type for rows. Note that this cursor is extremely specialized and does not allow the normal access (using integer indices) to fetched data. If you need to access database rows both as a dictionary and a list, then use the generic DictCursor instead of RealDictCursor. class psycopg2.extras.RealDictConnection A connection that uses RealDictCursor automatically. \nNote\nNot very useful since Psycopg2.5: you can use psycopg2.connect(dsn, cursor_factory=RealDictCursor) instead of RealDictConnection. class\n   psycopg2.extras.RealDictRow(cursor) A dict subclass representing a\n   data record.","Q_Score":15,"Tags":"python,python-3.x,postgresql,psycopg2","A_Id":54212351,"CreationDate":"2017-07-30T11:32:00.000","Title":"psycopg2: DictCursor vs RealDictCursor","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a project that :\n\nfetches data from active directory\nfetches data from different services based on active directory data\naggregates data \nabout 50000 row have to be added to database in every 15 min \n\nI'm using Postgresql as database and django as ORM tool. But I'm not sure that django is the right tools for such projects. I have to drop and add 50000 rows data and I'm worry about performance.\nIs there another way to do such process?","AnswerCount":3,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":81,"Q_Id":45404241,"Users Score":0,"Answer":"For sure there are other ways, if that's what you're asking. But Django ORM is quite flexible overall, and if you write your queries carefully there will be no significant overhead. 50000 rows in 15 minutes is not really big enough. I am using Django ORM with PostgreSQL to process millions of records a day.","Q_Score":0,"Tags":"django,python-2.7,postgresql,orm","A_Id":45404605,"CreationDate":"2017-07-30T20:12:00.000","Title":"Collecting Relational Data and Adding to a Database Periodically with Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am trying to generate a report in excel using win32com. I can get the information into the correct cells. However, one of my columns contains an ID number, and excel is formatting it as a number (displaying it in scientific notation). I have tried formatting the cell as text using sheet.Range(cell).NumberFormat = '@', which works, but will only update after the cell has been selected in the actual excel file. The same thing happens whether I format the cell before or after entering the data. Is there a way to refresh the cell formatting using win32com? I want the ID numbers to display correctly as soon as the com instance is made visible.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":328,"Q_Id":45443395,"Users Score":2,"Answer":"Pass a single leading quote to Excel ahead of the number, for example \"'5307245040001\" instead of \"5307245040001\"","Q_Score":0,"Tags":"python,excel,number-formatting,win32com","A_Id":45443851,"CreationDate":"2017-08-01T16:43:00.000","Title":"Formatting does not automatically update when using excel with win32com","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I would like to use xlwings wit the OPTIMIZED_CONNECTION set to TRUE. I would like to modify the setting but somehow cannot find where to do it. I change the _xlwings.conf sheet name in my workbook but this seems to have no effect. Also I cannot find these settings in VBA as I think I am supposed to under what is called \"Functions settings in VBA module\" in the xlwings documentation. I tried to re-import the VBA module but cannot find xlwings.bas on my computer.(only xlwings.xlam that I cannot access in VBA)\nI am using the 0.11.4 version of xlwings.\nSorry for this boring question and thanks in advance for any help.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":702,"Q_Id":45455892,"Users Score":0,"Answer":"The add-in replaces the need for the settings in VBA in newer versions.\nOne can debug the xlam module using \"xlwings\" as a password.\nThis enabled me to realize that the OPTIMIZED_CONNECTION parameter is now set through \"USE UDF SERVER\" keyword in the xlwings.conf sheet (which does work)","Q_Score":0,"Tags":"python,windows,xlwings","A_Id":45456886,"CreationDate":"2017-08-02T08:47:00.000","Title":"xlwings VBA function settings edit","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"So i am writing a python3 app with kivy and i want to have some data stored in a database using sqlite.\nThe user needs to have access to that data from the first time he opens the app\nIs there a way to possibly make it so that when i launch the app, the user that downloads it, will already have the data i stored, like distribute the database along with the app? so that i don't have to create it for every user.\nI have searched here and there but haven't found an answer yet\nThank you in advance","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":310,"Q_Id":45483128,"Users Score":1,"Answer":"Just include the database file in the apk, as you would any other file.","Q_Score":1,"Tags":"android,python-3.x,sqlite,kivy","A_Id":45489681,"CreationDate":"2017-08-03T11:39:00.000","Title":"Android-How can i attach SQLite database in python app","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":1,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"So I was trying learn sqlite and how to use it from Ipython notebook, and I have a sqlite object named db.\nI am executing this command:\n\nsel=\" \" \" SELECT * FROM candidates;\" \" \"\nc=db.cursor().execute(sel)\n\nand when I do this in the next cell:\n\nc.fetchall()\n\nit does print out all the rows but when I run this same command again i.e. I run\nc.fetchall() again it doesn't print out anything, it just displays a two square brackets with nothing inside them. But when I run the above first command ie, c=db.cursor().execute(sel) and then run db.fetchall() it again prints out the table.\nThis is very weird and I don't understand it, what does this mean?","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":189,"Q_Id":45498188,"Users Score":1,"Answer":"That is because .fetchall() makes your cursor(c) pointing the last row.\nif you want to select your DB again, you should .execute again.\nOr, if you just want to use your fetched data again, you can store c.fetchall() into your variable.","Q_Score":0,"Tags":"python,sqlite,ipython","A_Id":45498306,"CreationDate":"2017-08-04T04:16:00.000","Title":"Weird behavior by db.cursor.execute()","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am using django 1.10 and python 3.6.1\nwhen executing \nget_or_none(models.Character, pk=0), with SQL's get method, the query returns a hashmap i.e.: <Character: example>\nHow can I extract the value example?\nI tried .values(), I tried iterating, I tried .Character\nnothing seems to work, and I can't find a solution in the documentation.\nThank you,","AnswerCount":3,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":414,"Q_Id":45500972,"Users Score":0,"Answer":"@Daniel Roseman helped me understand the answer.\nSOLVED:\nWhat I was getting from the query was the model of character, so I couldn't have accessed it thru result.Character but thru result.Field_Inside_Of_Character","Q_Score":0,"Tags":"python,mysql,sql,django","A_Id":45501557,"CreationDate":"2017-08-04T07:43:00.000","Title":"Django SQL get query returns a  hashmap, how to access the value?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have to SSH into 120 machines and make a dump of a table in databases and export this back on to my local machine every day, (same database structure for all 120 databases).\nThere isn't a field in the database that I can extract the name from to be able to identify which one it comes from, it's vital that it can be identified, as it's for data analysis.\nI'm using the Python tool Fabric to automate the process and export the CSV on to my machine..\n\nfab -u PAI -H 10.0.0.35,10.0.0.XX,10.0.0.0.XX,10.0.0.XX -z 1\n  cmdrun:\"cd \/usr\/local\/mysql\/bin && .\/mysql -u root -p -e 'SELECT *\n  FROM dfs_va2.artikel_trigger;' >\n  \/Users\/admin\/Documents\/dbdump\/dump.csv\"\n  download:\"\/Users\/johnc\/Documents\/Imports\/dump.csv\"\n\nAbove is what I've got working so far but clearly, they'll all be named \"dump.csv\" is there any awesome people out there can give me a good idea on how to approach this?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":62,"Q_Id":45508137,"Users Score":0,"Answer":"You can try to modify your command as follow:\n\nmysql -uroot -p{your_password} -e 'SELECT * FROM dfs_va2.artikel_trigger;' > \/Users\/admin\/Documents\/dbdump\/$(hostname)_dump.csv\" download:\"\/Users\/johnc\/Documents\/Imports\/$(hostname)_dump.csv\"\n\nhostname returns current machine name so all your files should be unique (of course if machines have unique names)\nAlso you don't need to navigate to \/bin\/mysql every time, you can use simply mysql or absolute path \/usr\/local\/mysql\/bin\/mysql","Q_Score":0,"Tags":"python,automation,fabric,devops","A_Id":45508534,"CreationDate":"2017-08-04T13:28:00.000","Title":"Best way to automate file names of multiple databases","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":0},{"Question":"I am trying to include sqlite3 in an electron project I am getting my hands dirty with. I have never used electron, nor Node before, excuse my ignorance. I understand that to do this on Windows, I need Python installed, I need to download sqlite3, and I need to install it. \nAs per the NPM sqlite3 page, I am trying to install it using npm install --build-from-source\nIt always fails with \n\nunpack_sqlite_dep\n    'python' is not recognized as an internal or external command,\n    operable program or batch file.\n\nI have Python 2.7 installed and the path has been added to environment variable PATH. I can verify that if I type 'python' in cmd, I get the same response. BUT, if I type 'py', it works....\nSo, my question is: how can I make node-gyp use the 'py' command instead of 'python' when trying to unpack sqlite3?\nIf this is not possible, how can I make 'python' an acceptable command to use?\nI am using Windows 10 if this helps. Also, please let me know if I can do this whole procedure in a different way.\nThanks for any help!","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":259,"Q_Id":45527497,"Users Score":0,"Answer":"This has been resolved....\nUninstalled Python 2.7.13. Reinstalled, added path to PATH variable again, now command 'python' works just fine...","Q_Score":0,"Tags":"python-2.7,sqlite,electron,node-gyp","A_Id":45533423,"CreationDate":"2017-08-06T00:18:00.000","Title":"Failing to install sqlite3 plugin for electron project on windows","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have two database in mysql that have tables built from another program I have wrote to get data, etc. However I would like to use django and having trouble understanding the model\/view after going through the tutorial and countless hours of googling. My problem is I just want to access the data and displaying the data. I tried to create routers and done inspectdb to create models. Only to get 1146 (table doesn't exist issues). I have a unique key.. Lets say (a, b) and have 6 other columns in the table. I just need to access those 6 columns row by row. I'm getting so many issues. If you need more details please let me know. Thank you.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":104,"Q_Id":45529142,"Users Score":0,"Answer":"inspectdb is far from being perfect. If you have an existing db with a bit of complexity you will end up probably changing a lot of code generated by this command. One you're done btw it should work fine. What's your exact issue? If you run inspectdb and it creates a model of your table you should be able to import it and use it like a normal model, can you share more details or errors you are getting while querying the table you're interested in?","Q_Score":0,"Tags":"python,mysql,django","A_Id":45529591,"CreationDate":"2017-08-06T06:14:00.000","Title":"Django and Premade mysql databases","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a task which would really benefit from implementing partitioned tables, but I am torn because Postgres 10 will be coming out relatively soon. \n\nIf I just build normal tables and handle the logic with Python format strings to ensure that my data is loaded to the correct tables, can I turn this into a partition easily later?\nCan I upgrade Postgres 9.6 to 10 right now? Or is that not advisable? \nShould I install an extension like pg_partman?\n\nMy format string approach would just create separate tables (f{server}{source}{%Y%m}) and then I would union them together I suppose. Hopefully, I could eventually create a master table though without tearing anything down.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":130,"Q_Id":45535616,"Users Score":1,"Answer":"Pg 10 partitioning right now is functionally the same as 9.6, just with prettier notation. Pretty much anything you can do in Pg 10, you can also do in 9.6 with table-inheritance based partitioning, it's just not as convenient.\nIt looks like you may not have understood that table inheritance is used for partitioning in 9.6, since you refer to doing big UNIONs. This is unnecessary, PostgreSQL does it for you if you do inheritance-based partitioning. You can also have triggers that route inserts into the parent table into child tables, though it's more efficient for the application to route tuples like you suggest, by inserting directly into partitions. This will also work in PostgreSQL 10.\nPg's new built-in partitioning doesn't yet offer any new features you can't get with inheritance, like support for unique constraints across partitions, FKs referencing partitioned tables, etc. So there's really no reason to wait.\nJust study up on how to do partitioning on 9.6.\nI don't know if you can convert 9.6-style manual partitioning into PostgreSQL 10 native partitioning without copying the data. Ask on the mailing list or post a new specific question.\nThat said... often when people think they need partitioning, they don't. How sure are you that it's worth it?","Q_Score":1,"Tags":"python,postgresql","A_Id":45537959,"CreationDate":"2017-08-06T19:09:00.000","Title":"Postgres partitioning options right now?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I've been making this python script with openpyxl on a MAC. I was able to have an open excel workbook, modify something on it, save it, keep it open and run the script.\nWhen I switched to windows 10, it seems that I can't modify it, save it, keep it open,  and run the script. I keep getting an [ERRNO 13] Permission denied error. \nI tried to remove the read only mode on the folder I'm working on, I have all permissions on the computer, I clearly specified the save directory of my excel workbooks.\nAny idea on what could be the issue?","AnswerCount":4,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":2830,"Q_Id":45539241,"Users Score":0,"Answer":"make sure you have write permission in order to create a excel temporary lock file in said directory...","Q_Score":0,"Tags":"python,excel,openpyxl","A_Id":45539442,"CreationDate":"2017-08-07T04:01:00.000","Title":"openpyxl - Unable to access excel file with openpyxl when it is open but works fine when it is closed","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I've been making this python script with openpyxl on a MAC. I was able to have an open excel workbook, modify something on it, save it, keep it open and run the script.\nWhen I switched to windows 10, it seems that I can't modify it, save it, keep it open,  and run the script. I keep getting an [ERRNO 13] Permission denied error. \nI tried to remove the read only mode on the folder I'm working on, I have all permissions on the computer, I clearly specified the save directory of my excel workbooks.\nAny idea on what could be the issue?","AnswerCount":4,"Available Count":3,"Score":1.0,"is_accepted":false,"ViewCount":2830,"Q_Id":45539241,"Users Score":6,"Answer":"Windows does not let you modify open Excel files in another program -- only Excel may modify open Excel files. You must close the file before modifying it with the script. (This is one nice thing about *nix systems.)","Q_Score":0,"Tags":"python,excel,openpyxl","A_Id":50027342,"CreationDate":"2017-08-07T04:01:00.000","Title":"openpyxl - Unable to access excel file with openpyxl when it is open but works fine when it is closed","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I've been making this python script with openpyxl on a MAC. I was able to have an open excel workbook, modify something on it, save it, keep it open and run the script.\nWhen I switched to windows 10, it seems that I can't modify it, save it, keep it open,  and run the script. I keep getting an [ERRNO 13] Permission denied error. \nI tried to remove the read only mode on the folder I'm working on, I have all permissions on the computer, I clearly specified the save directory of my excel workbooks.\nAny idea on what could be the issue?","AnswerCount":4,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":2830,"Q_Id":45539241,"Users Score":0,"Answer":"I've had this issue with Excel files that are located in synced OneDrive folders. If I copy the file to a unsynced directory, openpyxl no longer has problems reading the .xlsx file while it is open in Excel.","Q_Score":0,"Tags":"python,excel,openpyxl","A_Id":50026988,"CreationDate":"2017-08-07T04:01:00.000","Title":"openpyxl - Unable to access excel file with openpyxl when it is open but works fine when it is closed","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I would like to host a database on my raspberry pi to which I can access from any device. I would like to access the contents of the database using python. \nWhat I've done so far:\n\nI installed the necessary mysql packages, including apache 2.   \nI created my first database which I named test.\nI wrote a simple php\n    script that connects and displays all the contents of my simple\n    database. The script is located on the raspberry pi at \/var\/www\/html\n    and is executed when I enter the following from my laptop\n    (192.168.3.14\/select.php)\n\nNow my goal is to be able to connect to the database using python from my laptop. But I seem to have an error connecting to it, this is what I wrote to connect to it.\ndb = MySQLdb.connect(\"192.168.3.14\",\"root\",\"12345\",\"test\" ) \nAny help or direction is appreciated.","AnswerCount":3,"Available Count":1,"Score":0.0665680765,"is_accepted":false,"ViewCount":104,"Q_Id":45593608,"Users Score":1,"Answer":"on the terminal of your raspi use the following command:\nmysql -u -p -h --port\nwhere you switch out your hostname with your ip address. since currently you can only connect via local host","Q_Score":0,"Tags":"php,python,mysql","A_Id":45593914,"CreationDate":"2017-08-09T14:31:00.000","Title":"Raspberry Pi Database Server","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I want to export data from Cassandra to Json file, because Pentaho didn't support my version of Cassandra 3.10","AnswerCount":4,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":3302,"Q_Id":45607301,"Users Score":0,"Answer":"You can use bash redirction to get json file.\ncqlsh -e \"select JSON * from ${keyspace}.${table}\" | awk 'NR>3 {print $0}' | head -n -2 > table.json","Q_Score":1,"Tags":"python,json,cassandra,cqlsh","A_Id":60649389,"CreationDate":"2017-08-10T07:35:00.000","Title":"How to export data from cassandra to Json file using Python or other language?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a task to import multiple Excel files in their respective sql server tables. The Excel files are of different schema and I need a mechanism to create a table dynamically; so that I don't have to write a Create Table query. I use SSIS, and I have seen some SSIS articles on the same. However, it looks I have to define the table anyhow. OpenRowSet doesn't work well in case of large excel files.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":59,"Q_Id":45610737,"Users Score":0,"Answer":"You can try using BiML, which dynamically creates packages based on meta data.\nThe only other possible solution is to write a script task.","Q_Score":0,"Tags":"python,sql,sql-server,excel,ssis","A_Id":45614658,"CreationDate":"2017-08-10T10:09:00.000","Title":"Multiple Excel with different schema Upload in SQL","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have python programs that use python's xlwings module to communicate with excel. They work great, but I would like to run them using a button from excel. I imported xlwings to VBA and use the RunPython command to do so. That also works great, however the code I use with RunPython is something like:\n\"from filename import function;function()\"\nwhich requires me to make the entire python program a function. This is annoying when I go back to make edits to the python program because every variable is local. Any tips on running the file from RunPython without having to create a function out of it?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":873,"Q_Id":45621637,"Users Score":2,"Answer":"RunPython basically just does what it says: run python code. So to run a module rather than a single function, you could do: RunPython(\"import filename\").","Q_Score":0,"Tags":"python,vba,excel,xlwings","A_Id":45622510,"CreationDate":"2017-08-10T19:01:00.000","Title":"Running Python from VBA using xlwings without defining function","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a Python Scraper that I run periodically in my free tier AWS EC2 instance using Cron that outputs a csv file every day containing around 4-5000 rows with 8 columns. I have been ssh-ing into it from my home Ubuntu OS and adding the new data to a SQLite database which I can then use to extract the data I want.\nNow I would like to try the free tier AWS MySQL database so I can have the database in the Cloud and pull data from it from my terminal on my home PC. I have searched around and found no direct tutorial on how this could be done. It would be great if anyone that has done this could give me a conceptual idea of the steps I would need to take. Ideally I would like to automate the updating of the database as soon as my EC2 instance updates with a new csv table. I can do all the de-duping once the table is in the aws MySQL database.\nAny advice or link to tutorials on this most welcome. As I stated, I have searched quite a bit for guides but haven't found anything on this. Perhaps the concept is completely wrong and there is an entirely different way of doing it that I am not seeing?","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":158,"Q_Id":45630562,"Users Score":1,"Answer":"The problem is you don't have access to RDS filesystem, therefore cannot upload csv there (and import too).\nModify your Python Scraper to connect to DB directly and insert data there.","Q_Score":0,"Tags":"python,mysql,database,database-design,amazon-ec2","A_Id":45643778,"CreationDate":"2017-08-11T08:36:00.000","Title":"Exported scraped .csv file from AWS EC2 to AWS MYSQL database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am looking for a solution to build an application with the following features:\n\nA database compound of -potentially- millions of rows in a table, that might be related with a few small ones.\nFast single queries, such as \"SELECT * FROM table WHERE field LIKE %value\"\nIt will run on a Linux Server: Single node, but maybe multiple nodes in the future.\n\nDo you think Python and Hadoop is a good choice?\nWhere could I find a quick example written in Python to add\/retrieve information to Hadoop in order to see a proof of concept running with my one eyes and take a decision?\nThanks in advance!","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":43,"Q_Id":45631450,"Users Score":1,"Answer":"Not sure whether these questions are on topic here, but fortunately the answer is simple enough:\nIn these days a million rows is simply not that large anymore, even Excel can hold more than a million.\nIf you have a few million rows in a large table, and want to run quick small select statements, the answer is that you are probably better off without Hadoop.\nHadoop is great for sets of 100 million rows, but does not scale down too wel (in performance and required maintenance). \nTherefore, I would recommend you to try using a 'normal' database solution, like MySQL. At least untill your data starts growing significantly.\n\nYou can use python for advanced analytical processing, but for simple queries I would recommend using SQL.","Q_Score":1,"Tags":"python,hadoop,hadoop-streaming","A_Id":45631639,"CreationDate":"2017-08-11T09:20:00.000","Title":"is the choice of Python and Hadoop a good one for this scenario?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm working on a little python3 server and I want to download a sqlite database from this server. But when I tried that, I discovered that the downloaded file is larger than the original : the original file size is 108K, the downloaded file size is 247K. I've tried this many times, and each time I had the same result. I also checked the sum with sha256, which have different results.\nHere is my downloader.py file :\nimport cgi\nimport os\n\nprint('Content-Type: application\/octet-stream')\nprint('Content-Disposition: attachment; filename=\"Library.db\"\\n')\n\ndb = os.path.realpath('..') + '\/Library.db'\nwith open(db,'rb') as file:\n    print(file.read())\nThanks in advance !\nEDIT :\nI tried that :\n$ .\/downloader > file\nfile's size is also 247K.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":445,"Q_Id":45646249,"Users Score":0,"Answer":"Well, I've finally found the solution. The problem (which I didn't see first) was that the server sent plain text to client. Here is one way to send binary data :\nimport cgi\nimport os\nimport shutil\nimport sys\n\nprint('Content-Type: application\/octet-stream; file=\"Library.db\"')\nprint('Content-Disposition: attachment; filename=\"Library.db\"\\n')\n\nsys.stdout.flush()\ndb = os.path.realpath('..') + '\/Library.db'\nwith open(db,'rb') as file:\n    shutil.copyfileobj(file, sys.stdout.buffer)\n\nBut if someone has a better syntax, I would be glad to see it ! Thank you !","Q_Score":0,"Tags":"python-3.x,cgi","A_Id":45646512,"CreationDate":"2017-08-12T03:33:00.000","Title":"File downloaded larger than original","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm working a lot with Excel xlsx files which I convert using Python 3 into Pandas dataframes, wrangle the data using Pandas and finally write the modified data into xlsx files again. \nThe files contain also text data which may be formatted. While most modifications (which I have done) have been pretty straight forward, I experience problems when it comes to partly formatted text within a single cell:\nExample of cell content: \"Medical device whith remote control and a Bluetooth module for communication\"\nThe formatting in the example is bold and italic but may also be a color. \nSo, I have two questions:\n\nIs there a way of preserving such formatting in xlsx files when importing the file into a Python environment?\nIs there a way of creating\/modifying such formatting using a specific python library?\n\nSo far I have been using Pandas, OpenPyxl, and XlsxWriter but have not succeeded yet. So I shall appreciate your help!\nAs pointed out below in a comment and the linked question OpenPyxl does not allow for this kind of formatting:\nAny other ideas on how to tackle my task?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":190,"Q_Id":45688168,"Users Score":0,"Answer":"i have been recently working with openpyxl. Generally if one cell has the same style(font\/color), you can get the style from cell.font:    cell.font.bmeans bold andcell.font.i means italic, cell.font.color contains color object.\nbut if the style is different within one cell, this cannot help. only some minor indication on cell.value","Q_Score":0,"Tags":"python,excel,pandas,openpyxl,xlsxwriter","A_Id":45689273,"CreationDate":"2017-08-15T07:22:00.000","Title":"Modifying and creating xlsx files with Python, specifically formatting single words of a e.g. sentence in a cell","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I've been pouring over everywhere I can to find an answer to this, but can't seem to find anything:\nI've got a batch update to a MySQL database that happens every few minutes, with Python handling the ETL work (I'm pulling data from web API's into the MySQL system).\nI'm trying to get a sense of what kinds of potential impact (be it positive or negative) I'd see by using either multithreading or multiprocessing to do multiple connections & inserts of the data simultaneously. Each worker (be it thread or process) would be updating a different table from any other worker.\nAt the moment I'm only updating a half-dozen tables with a few thousand records each, but this needs to be scalable to dozens of tables and hundreds of thousands of records each.\nEvery other resource I can find out there addresses doing multithreading\/processing to the same table, not a distinct table per worker. I get the impression I would definitely want to use multithreading\/processing, but it seems everyone's addressing the one-table use case.\nThoughts?","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":325,"Q_Id":45702192,"Users Score":0,"Answer":"For one I wrote in C#, I decided the best work partitioning was each \"source\" having a thread for extraction, one for each transform \"type\", and one to load the transformed data to each target. \nIn my case, I found multiple threads per source just ended up saturating the source server too much; it became less responsive overall (to even non-ETL queries) and the extractions didn't really finish any faster since they ended up competing with each other on the source. Since retrieving the remote extract was more time consuming than the local (in memory) transform, I was able to pipeline the extract results from all sources through one transformer thread\/queue (per transform \"type\"). Similarly, I only had a single target to load the data to, so having multiple threads there would have just monopolized the target.\n(Some details omitted\/simplified for brevity, and due to poor memory.)\n...but I'd think we'd need more details about what your ETL process does.","Q_Score":0,"Tags":"python,mysql,python-multiprocessing,python-multithreading","A_Id":45702416,"CreationDate":"2017-08-15T21:59:00.000","Title":"Python Multithreading\/processing gains for inserts to different tables in MySQL?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm trying to create app using the command python3 manage.py startapp webapp but i'm getting an error that says:\n\ndjango.core.exceptions.ImproperlyConfigured: Error loading either\n  pysqlite2 or sqlite3 modules (tried in that order): No module named\n  '_sqlite3'\n\nSo I tried installing sqlite3 using pip install sqlite3 but I got this error:\n\nUsing cached sqlite3-99.0.tar.gz\nComplete output from command python setup.py egg_info:\nTraceback (most recent call last):\nFile \"\", line 1, in \nFile \"\/tmp\/pip-build-dbz_f1ia\/sqlite3\/setup.py\", line 2, in \n          raise RuntimeError(\"Package 'sqlite3' must not be downloaded from pypi\")\nRuntimeError: Package 'sqlite3' must not be downloaded from pypi\nCommand \"python setup.py egg_info\" failed with error code 1 in \/tmp\/pip-build-dbz_f1ia\/sqlite3\/\n\nI tried running this command: sudo apt install sqlite3 but it says sudo is not a valid command, even apt isn't for some reason. I'm running Python3.6.2. I installed Python on my Godaddy hosting and i'm using SSH to install everything. I installed Python and setup a virtualenv. Afterwards, I installed Django and created a Django project. How can I fix these errors to successfully create a Django app?","AnswerCount":1,"Available Count":1,"Score":0.3799489623,"is_accepted":false,"ViewCount":5897,"Q_Id":45704177,"Users Score":2,"Answer":"sqlite3 is part of the standard library. You don't have to install it.\nIf it's giving you an error, you probably need to install your distribution's python-dev packages, eg with sudo apt-get install python-dev.","Q_Score":3,"Tags":"python,django,sqlite","A_Id":45706624,"CreationDate":"2017-08-16T02:25:00.000","Title":"Downloading sqlite3 in virtualenv","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Working with Python 2.7 and I'd like to add new sheets to a current Excel workbook indexed to a specific position. I know Openpyxl's create_sheet command will allow me to specify an index for a new sheet within an existing workbook, but there's a catch: Openpyxl will delete charts from an existing Excel workbook if opened & saved. And my workbook has charts that I don't wish to be deleted. \nIs there another way I can open this workbook, create a a few blank sheets that are located precisely after the existing first sheet, all without deleting any of the workbook's charts?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":70,"Q_Id":45724575,"Users Score":0,"Answer":"openpyxl 2.5 includes read support for charts","Q_Score":0,"Tags":"excel,python-2.7,openpyxl","A_Id":45729433,"CreationDate":"2017-08-16T23:45:00.000","Title":"Add indexed sheets to Excel workbook w\/out Openpyxl?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have configured the server to use MySQL Cluster. The Cluster architecture is as follows:\nOne Cluster Manager(ip1)\nTwo Data Nodes (ip2,ip3)\nTwo SQL Nodes(ip4,ip5)\nMy Question: Which node should I use to connect from Python application?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":915,"Q_Id":45728111,"Users Score":3,"Answer":"You have to call SQL nodes from your application. Use comma separated ip addresses for this. In your code use\nDB_HOST = \"ip4, ip5\"","Q_Score":0,"Tags":"python,mysql,mysql-cluster","A_Id":45729005,"CreationDate":"2017-08-17T06:35:00.000","Title":"Connecting to mysql cluster from python application","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I would like to know how to insert into same MongoDb collection from different python scripts running at the same time using pymongo\nany help redirecting guidance would be very appreciated because I couldn't find any clear documentation in pymongo or mongdb about it yet\nthank in advance","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":754,"Q_Id":45737486,"Users Score":1,"Answer":"You should be able to just insert into the collection in parallel without needing to do anything special.  If you are updating documents then you might find there are issues with locking, and depending on the storage engine which your MongoDB is using there may be collection locking, but this should not affect how you write your python script.","Q_Score":1,"Tags":"python,mongodb,python-3.x,pymongo,pymongo-3.x","A_Id":45737589,"CreationDate":"2017-08-17T14:11:00.000","Title":"Writing in parallel to MongoDb collection from python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"Let me explain the problem\n\nWe get real time data which is as big as 0.2Million per day. \nSome of these records are of special significance. The attributes\nthat shall mark them as significant are pushed in a reference collection.   Let us say each row in Master Database has the following attributes  \n\na. ID b. Type c. Event 1 d. Event 2 e. Event 3 f. Event 4\nFor the special markers, we identify them as  \n\n\nMarker1 -- Event 1 -- Value1  \n    Marker2 -- Event 3 -- Value1  \n    Marker3 -- Event 1 -- Value2  \n    and so on. We can add 10000 such markers. \n\n\n\nFurther, the attribute Type can be Image, Video, Text, Others. Hence the idea is to segregate Data based on Type, which means that we create 4 collections out of Master Collection. This is because we have to run search on collections based on Type and also run some processing.The marker data should show in a different tab on the search screen.  \nWe shall also be running a search on Master Collection through a wild search.  \nWe are running Crons to do these processes as \n\nI. Dumping Data in Master Collection - Cron 1  \nII. Assigning Markers - Cron 2  \nIII. Segregating Data based on Type - Cron 3  \nWhich runs as a module. Cron 1 - Cron 2 - Cron 3.  \nBut assigning targets and segregation takes a very long time. We are using Python as scripting language.  \nIn fact, the crons don't seem to work at all. The cron works from the command prompt. But scheduling these in crontab does not work. We are giving absolute path to the files. The crons are scheduled at 3 minutes apart.  \nCan someone help?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":143,"Q_Id":45769111,"Users Score":0,"Answer":"Yes, I also faced this problem but then I tried by moving small chunks of the data. Sharding is not the better way as per my experience regarding this kind of problem. Same thing for the replica set.","Q_Score":0,"Tags":"mongodb,python-3.x,cron","A_Id":45797856,"CreationDate":"2017-08-19T07:51:00.000","Title":"How to segregate large real time data in MongoDB","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I just want to set a password to my file \"file.db\" (SQLite3 database), if someone trying to open this DB it has to ask password for authentication.\nis there any way to do this Using python.\nThanks in Advance.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":52,"Q_Id":45811440,"Users Score":0,"Answer":"Asking a password when opening a file doesn't make much sense, it will take another program to do that, watching the file and intercepting the request at os level..\nWhat you need to do is protect the file using ACL, setting the proper access rights to only desired users&groups.","Q_Score":0,"Tags":"python,sqlite","A_Id":45811504,"CreationDate":"2017-08-22T07:28:00.000","Title":"protecting DB using Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"When selecting a data source for a graph in Excel, you can specify how the graph should treat empty cells in your data set (treat as zero, connect with next data point, leave gap). \nThe option to set this behavior is available in xlsxwriter with chart.show_blanks_as(), but I can't find it in openpyxl. If anyone knows where to find it or can confirm that it's not present, I'd appreciate it.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":101,"Q_Id":45825401,"Users Score":0,"Answer":"Asked the dev about it - \n\nThere is a dispBlanksAs property of the ChartContainer but this currently isn't accessible to client code.\n\nI looked through the source some more using that answer to guide me. The option is definitely in there, but you'd have to modify source and build locally to get at it.\nSo no, it's not accessible at this time.","Q_Score":0,"Tags":"python,excel,openpyxl","A_Id":45868428,"CreationDate":"2017-08-22T19:20:00.000","Title":"How to replicate the \"Show empty cells as\" functionality of Excel graphs","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I would like to store a \"set\" in a database (specifically PostgreSQL) efficiently, but I'm not sure how to do that efficiently.\nThere are a few options that pop to mind:\n\nstore as a list ({'first item', 2, 3.14}) in a text or binary column.  This has the downside of requiring parsing when inserting into the database and pulling out.  For sets of text strings only, this seems to work pretty well, and the parsing is minimal.  For anything more complicated, parsing becomes difficult.\nstore as a pickle in a binary column.  This seems like it should be quick, and it is complete (anything picklable works), but isn't portable across languages.\nstore as json (either as a binary object or a text stream).  Larger problems than just plain text, but better defined parsing.\n\nAre there any other options?  Does anyone have any experience with these?","AnswerCount":2,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":76,"Q_Id":45848956,"Users Score":2,"Answer":"What you want to do is store a one-to-many relationship between a row in your table and the members of the set.\nNone of your solutions allow the members of the set to be queried by SQL. You can't do something like select * from mytable where 'first item' in myset. Instead you have to retrieve the text\/blob and use another programming language to decode or parse it. That means if you want to do a query on the elements of the set you have to do a full table scan every time.\nI would be very reluctant to let you do something like that in one of my databases. \nI think you should break out your set into a separate table. By which I mean (since that is clearly not as obvious as I thought), one row per set element, indexed over primary key of the table you are referring from or, if you want to enforce no duplicates at the cost of a little extra space, primary key of the table you are referring from + set element value. \nSince your set elements appear to be of heterogeneous types I see no harm in storing them as strings, as long as you normalize the numbers somehow.","Q_Score":0,"Tags":"python,sql,json,postgresql,pickle","A_Id":45850429,"CreationDate":"2017-08-23T20:42:00.000","Title":"How to store a \"set\" (the python type) in a database efficiently?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have an excel xlsx file that I want to edit using python script.\nI know that openpyxl is not able to treat data-validation but I want just to edit the value of some cells containing data-validation and then save the workbook without editing those data-validation.\nFor now, when I try to do that, I get an error : \n\nUserWarning: Data Validation extension is not supported and will be\n  removed\n\nand then my saved file doesn't contain anymore the data-validation.\nIs there a way to tell openpyxl not to remove the data-validation when saving a workbook even if it can't read it?","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":2941,"Q_Id":45862917,"Users Score":1,"Answer":"To be clear: openpyxl does support data validation as covered by the original OOXML specification. However, since then Microsoft has extended the options for data validation and it these that are not supported. You might be able to adjust the data validation so that it is supported.","Q_Score":2,"Tags":"python,excel,openpyxl","A_Id":45863816,"CreationDate":"2017-08-24T13:26:00.000","Title":"openpyxl : data-validation read\/write without treatment","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I just switched from django 1.3.7 to 1.4.22 (on my way to updating to a higher version of django). I am using USE_TZ=True and TIME_ZONE = 'Europe\/Bucharest'. The problem that I am encountering is a DateTimeField from DB (postgres) that holds the value 2015-01-08 10:02:03.076+02 (with timezone) is read by my django as 2015-01-08 10:02:03.076000 (without timezone) even thou USE_TZ is True.\nAny ideea why this might happen? I am using python 2.7.12 AMD64.\nThanks,\nVirgil","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":32,"Q_Id":45878039,"Users Score":0,"Answer":"Seems I needed to logout once and log in again in the app for it to work. Thanks.","Q_Score":1,"Tags":"python,django","A_Id":45879886,"CreationDate":"2017-08-25T09:09:00.000","Title":"Django offset-naive date from DB","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am using 64-bit python anaconda v4.4 which runs python v3. I have MS Access 2016 32-bit version. I would like to use pyodbc to get python to talk to Access. Is it possible to use 64-bit pyodbc to talk to a MS Access 2016 32-bit database? \nI already have a number of python applications running with the 64-bit python anaconda. It will be a chore to downgrade to 32-bit python.","AnswerCount":3,"Available Count":1,"Score":0.2605204458,"is_accepted":false,"ViewCount":15479,"Q_Id":45928987,"Users Score":4,"Answer":"Unfortunately, you need 32-bit Python to talk to 32-bit MS Access. However, you should be able to install a 32-bit version of Python alongside 64-bit Python. Assuming you are using Windows, during a custom install you can pick the destination path. Then use a virtualenv. For example, if you install to C:\\Python36-32:\nvirtualenv --python=C:\\Python36-32\\bin\\python.exe\nGood luck!","Q_Score":10,"Tags":"python,ms-access,odbc,32bit-64bit,pyodbc","A_Id":45929130,"CreationDate":"2017-08-29T00:20:00.000","Title":"Is it possible for 64-bit pyodbc to talk to 32-bit MS access database?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"Hope you have a great day. I have a table with 470 columns to be exact. I am working on Django unit testing and the tests won't execute giving the error when I run command python manage.py test: \n\nRow size too large (> 8126). Changing some columns to TEXT or BLOB or using ROW_FORMAT=DYNAMIC or ROW_FORMAT=COMPRESSED may help. In\n  current row format, BLOB prefix of 768 bytes is stored inline\n\nTo resolve this issue I am trying to increase the innodb_page_size in MySQL my.cnf file. When I restart MySQL server after changing value in my.cnf file, MySQL won't restart.\nI have tried almost every available solution on stackoverflow but no success.\nMYSQL version=5.5.57\nUbuntu version = 16.04\nAny help would be greatly appreciated. Thank you","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":978,"Q_Id":45964972,"Users Score":0,"Answer":"Since I have never seen anyone use the feature of having bigger block size, I have no experience with making it work.  And I recommend you not be the first to try.\nInstead I offer several likely workarounds.\nDon't use VARCHAR(255) blindly; make the lengths realistic for the data involved.\nDon't use uf8 (or utf8mb4) for columns that can only have ascii.  Examples: postcode, hex strings, UUIDs, country_code, etc.  Use CHARACTER SET ascii.\nVertically partition the table.  That is spit it into two tables with the same PRIMARY KEY.\nDon't splay arrays across columns; use another table and have multiple rows in it.  Example:  phone1, phone2, phone3.","Q_Score":0,"Tags":"python,mysql,django,unit-testing,innodb","A_Id":46018456,"CreationDate":"2017-08-30T15:58:00.000","Title":"Changing innodb_page_size in my.cnf file does not restart mysql database","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"when I try to connect to my application deploy at Pythonanywhere database does not working, its seems that he can't reach to him.\nwhen I am using my computer and run the app all seems to be perfect.\nany one any ideas? \nThanks very much.","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":197,"Q_Id":46013567,"Users Score":1,"Answer":"Hey after checking out I found that pythonanywhere required paid plan in order to use mlab services, or others services.","Q_Score":0,"Tags":"mongodb,pythonanywhere,mlab","A_Id":46028070,"CreationDate":"2017-09-02T12:03:00.000","Title":"pythonanywhere with mlab(mongoDB)","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm trying to connect to a PostgreSQL database on Google Cloud using SQLAlchemy. Making a connection to the database requires specifying a database URL of the form:  dialect+driver:\/\/username:password@host:port\/database\nI know what the dialect + driver is (postgresql), I know my username and password, and I know the database name. But I don't know how to find the host and port on the Google Cloud console. I've tried using the instance connection name, but that doesn't seem to work. Anyone know where I can find this info on Google Cloud?","AnswerCount":3,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":6507,"Q_Id":46178062,"Users Score":3,"Answer":"Hostname is the Public IP address.","Q_Score":3,"Tags":"python,postgresql,google-cloud-platform,google-cloud-storage,google-cloud-sql","A_Id":64040093,"CreationDate":"2017-09-12T13:42:00.000","Title":"What is the hostname for a Google Cloud PostgreSQL instance?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I have two data files which is some weird format. Need to parse it to some descent format to use that for future purposes. after parsing i end up having two formats on which one has an id and respective information pertaining to that id will be from another file.\nEx : \nFrom file 1 i get\nName, Position, PropertyID\nfrom file 2\nPropertyId, Property1,Property2\nlike this i have more columns from both the file.\nwhat is the idle way to store these information in a flat file to server as a database. i don't want to use database(Mysql,MsSql) for some reason.\ninitially i thought of using single Coma separated file. but ill end up using so many columns which will create problem when i update these information.\nI ll be using the parsed data in some other application using java and python\ncan anyone suggest better way to handle this\nThanks","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1067,"Q_Id":46180651,"Users Score":0,"Answer":"Ensure that you normalize your data with an ID to avoid touching so many different data columns with even a single change. Like the file2 you mentioned above, you can reduce the columns to two by having just the propertyId and the property columns. Rather than having 1 propertyId associated with 2 property in a single row you'd have 1 propertyId associated with 1 property per your example above. You need another file to correlate your two main data table. Normalizing your data like this can make your updates to them very minimal when change occurs.\nfile1:\nowner_id   |  name      |  position    |\n1          |  Jack Ma    |  CEO        |\nfile2:\nproperty_id  |  property             |\n101            |  Hollywood Mansion    |\n102            |  Miami Beach House    |\nfile3:\nOwnerId   |  PropertyId  |\n1         |  101\n1         |  102","Q_Score":0,"Tags":"java,python,flat-file","A_Id":46181307,"CreationDate":"2017-09-12T15:44:00.000","Title":"Storing data in flat files","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am running my Python script in which I write excel files to put them into my EC2 instance. However, I have noticed that these excel files, although they are created, are only put into the server once the code stops.\nI guess they are kept in cache but I would like them to be added to the server straight away. Is there a \"commit()\" to add to the code?\nMany thanks","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":116,"Q_Id":46300696,"Users Score":1,"Answer":"I guess they are kept in cache but I would like them to be added to the server straight away. Is there a \"commit()\" to add to the code?\n\nNo. It isn't possible to stream or write a partial xlsx file like a CSV or Html file since the file format is a collection of XML files in a Zip container and it can't be generated until the file is closed.","Q_Score":1,"Tags":"python,excel,amazon-web-services,amazon-ec2,xlsxwriter","A_Id":46301367,"CreationDate":"2017-09-19T12:40:00.000","Title":"xlswriter on a EC2 instance","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Django-Storages provides an S3 file storage backend for Django.  It lists\nAWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY as required settings.  If I am using an AWS Instance Profile to provide S3 access instead of a key pair, how do I configure Django-Storages?","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":1069,"Q_Id":46307447,"Users Score":1,"Answer":"The docs now explain this:\n\nIf AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY are not set, boto3 internally looks up IAM credentials.","Q_Score":3,"Tags":"django,amazon-s3,boto3,python-django-storages","A_Id":61942402,"CreationDate":"2017-09-19T18:28:00.000","Title":"Use Django-Storages with IAM Instance Profiles","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am getting the below error while running the cqlsh in cassandra 2.2.10 ?? Can somebody help me to pass this hurdle:\n\n[root@rac1 site-packages]# $CASSANDRA_PATH\/bin\/cqlsh\nPython Cassandra driver not installed, or not on PYTHONPATH. You might\n  try \u201cpip install cassandra-driver\u201d.\nPython: \/usr\/local\/bin\/python Module load path:\n  [\u2018\/opt\/cassandra\/apache-cassandra-2.2.10\/bin\/..\/lib\/six-1.7.3-py2.py3-none-any.zip\u2019,\n  \u2018\/opt\/cassandra\/apache-cassandra-2.2.10\/bin\/..\/lib\/futures-2.1.6-py2.py3-none-any.zip\u2019,\n  \u2018\/opt\/cassandra\/apache-cassandra-2.2.10\/bin\/..\/lib\/cassandra-driver-internal-only-3.5.0.post0-d8d0456.zip\/cassandra-driver-3.5.0.post0-d8d0456\u2019,\n  \u2018\/opt\/cassandra\/apache-cassandra-2.2.10\/bin\u2019,\n  \u2018\/usr\/local\/lib\/python2.7\/site-packages\u2019,\n  \u2018\/usr\/local\/lib\/python27.zip\u2019, \u2018\/usr\/local\/lib\/python2.7\u2019,\n  \u2018\/usr\/local\/lib\/python2.7\/plat-linux2\u2019,\n  \u2018\/usr\/local\/lib\/python2.7\/lib-tk\u2019, \u2018\/usr\/local\/lib\/python2.7\/lib-old\u2019,\n  \u2018\/usr\/local\/lib\/python2.7\/lib-dynload\u2019]\nError: can\u2019t decompress data; zlib not available","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":2223,"Q_Id":46314983,"Users Score":0,"Answer":"Cassandra uses the python driver bundled in-tree in a zip file. If your Python runtime was not built with zlib support, it cannot use the zip archive in the PYTHONPATH. Either install the driver directly (pip install) as suggested, or put a correctly configured Python runtime in your path.","Q_Score":1,"Tags":"python,linux,cassandra","A_Id":47167910,"CreationDate":"2017-09-20T06:42:00.000","Title":"Python Cassandra driver not installed, or not on PYTHONPATH","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":0},{"Question":"My team uses .rst\/sphinx for tech doc. We've decided to do tables in csv files, using the .. csv-table:: directive. We are beginning to using sphinx-intl module for translation. Everything seems to work fine, except that I don't see any our tables int he extracted .po files. Has anyone had this experience? What are best practices for doing csv tables and using sphinx-intl?","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":89,"Q_Id":46351068,"Users Score":1,"Answer":"We tested and verified that the csv content is automatically extracted into PO files, and building a localized version places the translated strings in MO files back into the table.","Q_Score":0,"Tags":"internationalization,python-sphinx,restructuredtext","A_Id":46535864,"CreationDate":"2017-09-21T18:40:00.000","Title":"How do I use sphinx-intl if I am using the .. csv-table:: directives for my tables?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"can I get some advice, how to make mechanism for inserts, that will check if the values of PK is used? \nIf it is not used in the table, it will insert row with number. If it is used, it will increment value and check next value if it's used. So on...","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":26,"Q_Id":46380101,"Users Score":0,"Answer":"This is too long for a comment.\nYou would need a trigger in the database to correctly implement this functionality.  If you try to do it in the application layer, then you will be subject to race conditions in a multi-client environment.\nWithin Oracle, I would recommend just using an auto-generated column for the primary key.  Don't try inserting it yourself.  In Oracle 12C, you can define this directly using generated always as.  In earlier versions, you need to use a sequence to define the numbers and a trigger to assign them.","Q_Score":0,"Tags":"python,oracle,cx-oracle","A_Id":46380171,"CreationDate":"2017-09-23T13:31:00.000","Title":"cx_oracle PK autoincrementarion","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"We've had a Flask application using pymssql running for 1.5 years under Python 2.7 and SQL Server 2012. We moved the application to a new set of servers and upgraded the Flask app to Python 3.6 and a new database server to SQL Server 2016. They're both Windows servers.\nSince then, we've been getting intermittent 20017 errors:\npymssql.OperationalError(20017, b'DB-Lib error message 20017, severity 9:\\nUnexpected EOF from the server (xx.xx.xx.xx:1433)\\nDB-Lib error message 20002, severity 9:\\nAdaptive Server connection failed (xx.xx.xx.xx:1433)\\n')\nOnly a small percentage of the calls return this, but enough to be causing problems. I can provide specific versions of everything we're running.\nOne solution proposed is to switch to pyodbc, but we have hundreds of queries and stored procedure calls, many with UUIDs, which pyodbc doesn't handle nearly as cleanly as pymssql.\nI've installed pymssql via a precompiled wheel (pymssql-2.1.3-cp36-cp36m-win_amd64) because pip can't build it without an older version.\nAny ideas on debugging or fixing this would be helpful.","AnswerCount":1,"Available Count":1,"Score":0.3799489623,"is_accepted":false,"ViewCount":933,"Q_Id":46410009,"Users Score":2,"Answer":"Well, our answer was to switch to pyodbc. A few utility functions made it more or less a cut-and-paste with a few gotchas here and there, but pymssql has been increasingly difficult to build, upgrade, and use for the last few years.","Q_Score":2,"Tags":"sql-server,python-3.x,flask,pymssql","A_Id":46436613,"CreationDate":"2017-09-25T16:32:00.000","Title":"Pymssql Error 20017 after upgrading to Python 3.6 and SQL Server 2016","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm using openpyxl for Python 2.7 to open and then modify a existing .xlsx file. This excel file has about 2500 columns and just 10 rows. The problem is openpyxl took to long to load the file (almost 1 Minute). Is there anyway to speed up the loading process of openpyxl. From other Threads I found some tips with read_only and write_only. But i have to read and write excel at the same time, so i can't apply this tips for me. Does anyone have any Suggestion. Thanks you very much","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1358,"Q_Id":46428168,"Users Score":0,"Answer":"I had the same issue and found that while i was getting reasonable times initially (opening and closing was taking maybe 2-3 seconds), this suddenly increased to over a minute. I had introduced logging, so thought that may have been the cause, but after commenting this out, there was still a long delay\nI copied the data from the Excel spreadsheet and just saved to a new excel spreadsheet which fixed it for me.  Seems like it must have got corrupted somehow.  \nNote - saving the same filename as another filename didn't work, neither did saving the same filename on a local drive.","Q_Score":0,"Tags":"python,excel,openpyxl","A_Id":55336278,"CreationDate":"2017-09-26T13:42:00.000","Title":"Openpyxl loading existing excel takes too long","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I've noticed that many SQLAlchemy tutorials would use relationship() in \"connecting\" multiple tables together, may their relationship be one-to-one, one-to-many, or many-to-many. However, when using raw SQL, you are not able to define the relationships between tables explicitly, as far as I know.\nIn what cases is relationship() required and not required? Why do we have to explicitly define the relationship between tables in SQLAlchemy?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1079,"Q_Id":46462152,"Users Score":10,"Answer":"In SQL, tables are related to each other via foreign keys. In an ORM, models are related to each other via relationships. You're not required to use relationships, just as you are not required to use models (i.e. the ORM). Mapped classes give you the ability to work with tables as if they are objects in memory; along the same lines, relationships give you the ability to work with foreign keys as if they are references in memory.\nYou want to set up relationships for the same purpose as wanting to set up models: convenience. For this reason, the two go hand-in-hand. It is uncommon to see models with raw foreign keys but no relationships.","Q_Score":9,"Tags":"python,sqlalchemy","A_Id":46462502,"CreationDate":"2017-09-28T06:14:00.000","Title":"Is it necessary to use `relationship()` in SQLAlchemy?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a question about sqlite3. If I were to host a database online, how would I access it through python's sqlite3 module? \nE.g. Assume I had a database hosted at \"www.example.com\/database.db\". Would it be as simple as just forming a connection with sqlite3.connect (\"www.example.com\/database.db\") or is there more I need to add so that the string is interpreted as a url and not a filename?","AnswerCount":2,"Available Count":1,"Score":0.2913126125,"is_accepted":false,"ViewCount":1622,"Q_Id":46492388,"Users Score":3,"Answer":"SQLite3 is embedded-only database so it does not have network connection capabilities. You will need to somehow mount the remote filesystem.\nWith that being said, SQLite3 is not meant for this. Use PostgreSQL or MySQL (or anything else) for such purposes.","Q_Score":4,"Tags":"python,database,sqlite","A_Id":46492537,"CreationDate":"2017-09-29T15:39:00.000","Title":"Connecting to an online database through python sqlite3","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have two databases in odoo DB1 and DB2. I made some changes to existing modules(say module1 and module2) in DB1 through GUI(web client). All those changes were stored to DB1 and were working correctly when I am logged in through DB1.\nNow, I made some changes in few files(in same two modules module1 and module2). These modules need to be upgraded in order to load those changes. So, i logged in from DB2 and upgraded those modules. My changes in file loaded correctly and were working correctly when I am logged in through DB2.\nBut those file changes were loaded only for DB2 and not for DB1.\nSo, I wanted to know:\n\nHow upgrading of a module works?? Does it upgrades only for the database through which the user is logged in and upgraded the module?\nAnd if it is so. Then, is there a way that I can Upgrade my module while retaining all the previous changes that i made through the GUI in that same module?\nWhat are the things that are changed when a module is upgraded?","AnswerCount":2,"Available Count":2,"Score":0.2913126125,"is_accepted":false,"ViewCount":1295,"Q_Id":46500405,"Users Score":3,"Answer":"you can restart the server and start the server by python odoo-bin -d database_name -u module_name\nor -u all to update all module","Q_Score":4,"Tags":"python,openerp,odoo-9,odoo-10","A_Id":46501313,"CreationDate":"2017-09-30T07:04:00.000","Title":"How upgrading of a Odoo module works?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have two databases in odoo DB1 and DB2. I made some changes to existing modules(say module1 and module2) in DB1 through GUI(web client). All those changes were stored to DB1 and were working correctly when I am logged in through DB1.\nNow, I made some changes in few files(in same two modules module1 and module2). These modules need to be upgraded in order to load those changes. So, i logged in from DB2 and upgraded those modules. My changes in file loaded correctly and were working correctly when I am logged in through DB2.\nBut those file changes were loaded only for DB2 and not for DB1.\nSo, I wanted to know:\n\nHow upgrading of a module works?? Does it upgrades only for the database through which the user is logged in and upgraded the module?\nAnd if it is so. Then, is there a way that I can Upgrade my module while retaining all the previous changes that i made through the GUI in that same module?\nWhat are the things that are changed when a module is upgraded?","AnswerCount":2,"Available Count":2,"Score":0.3799489623,"is_accepted":false,"ViewCount":1295,"Q_Id":46500405,"Users Score":4,"Answer":"There is 2 step for upgrading an addons in Odoo,\nFirst, restarting the service. it will upgrade your .py files.\nSecond, click upgrade button in Apps>youraddonsname. it will upgrade your .xml files.\ni create a script for upgrading the XML files. the name is upgrade.sh\n#!\/bin\/sh\nfor db in $(cat \/opt\/odoo\/scripts\/yourlistdbfiles);\ndo\nodoo --addons-path=\/opt\/odoo\/youraddonspath -d $db -u youraddonsname --no-xmlrpc > \/opt\/odoo\/logs\/yourlogfiles.log 2>&1 &\nsleep 20s && exit &\ndone\nso you just run sh \/opt\/odoo\/script\/upgrade.sh after editing your addons and no need to click the upgrade button anymore.\nhope this help","Q_Score":4,"Tags":"python,openerp,odoo-9,odoo-10","A_Id":46513745,"CreationDate":"2017-09-30T07:04:00.000","Title":"How upgrading of a Odoo module works?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm updating from an ancient language to Django. I want to keep the data from the old project into the new.\nBut old project is mySQL. And I'm currently using SQLite3 in dev mode. But read that postgreSQL is most capable. So first question is: Is it better to set up postgreSQL while in development. Or is it an easy transition to postgreSQL from SQLite3?\nAnd for the data in the old project. I am bumping up the table structure from the old mySQL structure. Since it got many relation db's. And this is handled internally with foreignkey and manytomany in SQLite3 (same in postgreSQL I guess).\nSo I'm thinking about how to transfer the data. It's not really much data. Maybe 3-5.000 rows.\nProblem is that I don't want to have same table structure. So a import would be a terrible idea. I want to have the sweet functionality provided by SQLite3\/postgreSQL.\nOne idea I had was to join all the data and create a nested json for each post. And then define into what table so the relations are kept.\nBut this is just my guessing. So I'm asking you if there is a proper way to do this?\nThanks!","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":31,"Q_Id":46544518,"Users Score":0,"Answer":"better create the postgres database. write down the python script which take the data from the mysql database and import in postgres database.","Q_Score":0,"Tags":"python,django,database,postgresql,sqlite","A_Id":46544581,"CreationDate":"2017-10-03T12:22:00.000","Title":"Importing data from multiple related tables in mySQL to SQLite3 or postgreSQL","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am trying to upload data from certain fields in a CSV file to an already existing table.\nFrom my understanding, the way to do this is to create a new table and then append the relevant columns of the newly created table to the corresponding columns of the main table.\nHow exactly do I append certain columns of data from one table to another?\nAs in, what specific commands?\nI am using the bigquery api and the python-client-library.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":4039,"Q_Id":46546388,"Users Score":0,"Answer":"You can use pandas library for that.\n\nimport pandas as pd \ndata = pd.read_csv('input_data.csv')\nuseful_columns = [col1, col2, ... ] # List the columns you need data[useful_columns].to_csv('result_data.csv', index=False) # index=False is to prevent creating extra column","Q_Score":1,"Tags":"python,csv,google-api,google-bigquery,google-python-api","A_Id":46546554,"CreationDate":"2017-10-03T13:57:00.000","Title":"How to Skip Columns of CSV file","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I\u2019m building a web app (python\/Django) where customers create an account, each customer creates\/adds as many locations as they want and a separate server generates large amounts of data for each location several times a day. \nFor example:\nUser A -> [locationA, locationB]\nUser B -> [locationC, locationD, locationE]\nWhere each location is an object that includes name, address, etc. \nEvery 3 hours a separate server gathers data from various sources like weather, check-ins etc for each location and I need to store each item from each iteration so I can then perform per-user-per-location queries. \nE.g. \u201call the checkins in the last week group by location for User A\u201d\nRight now I am using MongoDB and storing a collection of venues with a field of ownerId which is the ObjectID of the owning user. \nWhat is the best strategy to store the records of data? The na\u00efve approach seems to be a collection for checkins, a collection for weather records etc and each document would have a \u201clocation\u201d field. But this seems to have both performance and security problems (all the access logic would be in web app code). \nWould it be better to have a completely separate DB for each user? Are there better ways?\nIs a different strategy better if we switch to Postgres\/SQL database?","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":81,"Q_Id":46553070,"Users Score":1,"Answer":"[GENERAL ADVICE]: I always use Postgres or MySQL as the django ORM connection and then Mongo or DynamoDB for analytics.  You can say that it creates unnecessary complexity because that is true, but for us that abstraction makes it easier to separate out teams too.  You have your front end devs, backend\/ full stacks, and true backend devs.  Not all of them need to be Django experts.\n[SPECIFIC ADVICE]: This sounds to me like you should just get started with mongo.  Unless you are a B2B SaaS app selling to enterprise companies who won't like a multi-tenet data model then it shouldn't be tough to map this out in mongo.  The main reason I say mongo is nice is because it sounds like you don't fully know the schema of what you'll collect ahead of time.  Later you can refactor once you get a better handle of what data you collect.  Expect to refactor and just get the thing working.","Q_Score":1,"Tags":"python,sql,django,mongodb,postgresql","A_Id":46553762,"CreationDate":"2017-10-03T20:41:00.000","Title":"Right strategy for segmenting Mongo\/Postgres database by customer?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a large amount of data around 50GB worth in a csv which i want to analyse purposes of ML. It is however way to large to fit in Python. I ideally want to use mySQL because querying is easier. Can anyone offer a host of tips for me to look into. This can be anything from: \n\nHow to store it in the first place, i realise i probably can't load it in all at once, would i do it iteratively? If so what things can i look into for this? In addition i've heard about indexing, would that really speed up queries on such a massive data set?\nAre there better technologies out there to handle this amount of data and still be able to query and do feature engineering quickly. What i eventually feed into my algorithm should be able to be done in Python but i need query and do some feature engineering before i get my data set that is ready to be analysed.\n\nI'd really appreciate any advice this all needs to be done on personal computer! Thanks!!","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":589,"Q_Id":46574694,"Users Score":0,"Answer":"That's depend on what you have, you can use Apache spark and then use their SQL feature, spark SQL gives you the possibility to write SQL queries in your dataset, but for best performance you need a distributed mode(you can use it in a local machine but the result is limited) and high machine performance. you can use python, scala, java to write your code.","Q_Score":0,"Tags":"python,mysql,bigdata,mysql-python","A_Id":46607645,"CreationDate":"2017-10-04T21:45:00.000","Title":"Storing and querying a large amount of data","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I want to create a program, which automates excel reporting including various graphs in colours. The program needs to be able to read an excel dataset. Based on this dataset, the program then has to create report pages and graphs and then export to an excel file as well as pdf file.\nI have done some research and it seems this is possible using python with pandas - xlsxWriter or xlswings as well as Ruby gems - axlsx or win32ole. \nWhich is the user-friendlier and easy to learn alternative? What are the advantages and disadvantages? Are there other options I should consider (I would like to avoid VBA - as this is how the reports are currently produced)?\nAny responses and comments are appreciated. Thank you!","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":388,"Q_Id":46575847,"Users Score":0,"Answer":"If you already have VBA that works for your project, then translating it to Ruby + WIN32OLE is probably your quickest path to working code. Anything you can do in VBA is doable in Ruby (if you find something you can't do, post here to ask for help).\nI prefer working with Excel via OLE since I know the file produced by Excel will work anywhere I open it. I haven't used axlsx but I'm sure it's a fine project; I just wouldn't trust that it would produce working Excel files every time.","Q_Score":0,"Tags":"python,ruby,excel,xlsxwriter,axlsx","A_Id":46669389,"CreationDate":"2017-10-04T23:52:00.000","Title":"Automating excel reporting and graphs - Python xlsxWriter\/xlswings or Ruby axlsx\/win32ole","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"So I have two table in a one-to-many relationship. When I make a new row of Table1, I want to populate Table2 with the related rows. However, this population actually involves computing the Table2 rows, using data in other related tables. \nWhat's a good way to do that using the ORM layer? That is, assuming that that the Table1 mappings are created through the ORM, where\/how should I call the code to populate Table2?\nI thought about using the after_insert hook, but i want to have a session to pass to the population method.\nThanks.","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":601,"Q_Id":46594866,"Users Score":1,"Answer":"After asking around in #sqlalchemy IRC, it was pointed out that this could be done using ORM-level relationships in an before_flush event listener.\nIt was explained that when you add a mapping through a relationship, the foreign key is automatically filled on flush, and the appropriate insert statement generated by the ORM.","Q_Score":1,"Tags":"python,sql,database,orm,sqlalchemy","A_Id":46777010,"CreationDate":"2017-10-05T21:11:00.000","Title":"Populating related table in SqlAlchemy ORM","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I've built some tools that create front-end list boxes for users that reference dynamic Redshift tables. New items in the table, they appear automatically in the list.\nI want to put the list in alphabetical order in the database so the dynamic list boxes will show the data in that order. \nAfter downloading the list from an API, I attempt to sort the list alphabetically in a Pandas dataframe before uploading. This works perfectly:\ndf.sort_values(['name'], inplace=True, ascending=True, kind='heapsort')\nBut then when I try to upload to Redshift in that order, it loses the order while it uploads. The data appears in chunks of alphabetically ordered segments.\ndb_conn = create_engine('<redshift connection>')\nobj.to_sql('table_name', db_conn, index = False, if_exists = 'replace')\nBecause of the way the third party tool (Alteryx) works, I need to have this data in alphabetical order in the database. \nHow can I modify to_sql to properly upload the data in order?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":725,"Q_Id":46608223,"Users Score":0,"Answer":"While ingesting data into redshift, data gets distributed between slices on each node in your redshift cluster. \nMy suggestion would be to create a sort key on a column which you need to be sorted. Once you have sort key on that column, you can run Vacuum command to get your data sorted.\nSorry! I cannot be of much help on Python\/Pandas\nIf I\u2019ve made a bad assumption please comment and I\u2019ll refocus my answer.","Q_Score":0,"Tags":"python,sorting,amazon-redshift,pandas-to-sql","A_Id":46610485,"CreationDate":"2017-10-06T14:36:00.000","Title":"Sorting and loading data from Pandas to Redshift using to_sql","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm working with a small company currently that stores all of their app data in an AWS Redshift cluster. I have been tasked with doing some data processing and machine learning on the data in that Redshift cluster.\nThe first task I need to do requires some basic transforming of existing data in that cluster into some new tables based on some fairly simple SQL logic. In an MSSQL environment, I would simply put all the logic into a parameterized stored procedure and schedule it via SQL Server Agent Jobs. However, sprocs don't appear to be a thing in Redshift. How would I go about creating a SQL job and scheduling it to run nightly (for example) in an AWS environment? \nThe other task I have involves developing a machine learning model (in Python) and scoring records in that Redshift database. What's the best way to host my python logic and do the data processing if the plan is to pull data from that Redshift cluster, score it, and then insert it into a new table on the same cluster? It seems like I could spin up an EC2 instance, host my python scripts on there, do the processing on there as well, and schedule the scripts to run via cron?\nI see tons of AWS (and non-AWS) products that look like they might be relevant (AWS Glue\/Data Pipeline\/EMR), but there's so many that I'm a little overwhelmed. Thanks in advance for the assistance!","AnswerCount":3,"Available Count":1,"Score":0.0665680765,"is_accepted":false,"ViewCount":2154,"Q_Id":46618762,"Users Score":1,"Answer":"The 2 options for running ETL on Redshift\n\nCreate some \"create table as\" type SQL, which will take your source\ntables as input and generate your target (transformed table)\nDo the transformation outside of the database using an ETL tool. For\nexample EMR or Glue.\n\nGenerally, in an MPP environment such as Redshift, the best practice is to push the ETL to the powerful database (i.e. option 1). \nOnly consider taking the ETL outside of Redshift (option 2) where SQL is not the ideal tool for the transformation, or the transformation is likely to take a huge amount of compute resource.\nThere is no inbuilt scheduling or orchestration tool. Apache Airflow is a good option if you need something more full featured than cron jobs.","Q_Score":1,"Tags":"python,database,amazon-web-services,amazon-redshift","A_Id":46640656,"CreationDate":"2017-10-07T09:41:00.000","Title":"AWS Redshift Data Processing","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I successfully installed mod_wsgi via pip install mod_wsgi on Windows. However, when I copy the output of mod_wsgi-express module-config into my httpd.conf and try to start the httpd, I get the following error:\nhttpd.exe: Syntax error on line 185 of C:\/path\/to\/httpd.conf: Cannot load c:\/path\/to\/venv\/Lib\/site-packages\/mod_wsgi\/server\/mod_wsgi.pyd into server\nThis is already after correcting the pasted output of module-config, as it was ...\/venv\/lib\/site-packages\/mod_wsgi\/server\/mod_wsgiNone (note the \"None\"). I changed the \"None\" to \".pyd\" as this is the correct path.\nI already tried to install it outside the virtual env (Python being at C:\\Python27), but it didn't make a difference -> same error.\nI also tried to uninstall\/re-install mod_wsgi. I had one failed install as Microsoft Visual C++ Compiler for Python 2.7 (Version 9.0.0.30729) was not present. After that installation, the mod_wsgi always installed OK.\nThe apache (Apache\/2.4.27 (Win32)) comes from the xampp package and starts without issues when I remove the added lines for wsgi. \nI need to use Python 2.7 because of a third-party module. So going for 3.x is unfortunately not an option at the moment.\nExact Python version is 2.7.13 (32-bit).\nFor completeness, the output of module-config is:\nLoadModule wsgi_module \"c:\/www\/my_project\/venv\/lib\/site-packages\/mod_wsgi\/server\/mod_wsgiNone\"\nWSGIPythonHome \"c:\/www\/my_project\/venv\"\nUpdate: tried one more thing:\n\nUninstalled mod_wsgi (with pip)\nset \"MOD_WSGI_APACHE_ROOTDIR=C:\/WWW\/apache\"\nAnd pip install mod_wsgi again\n\nStill the same error...","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1202,"Q_Id":46622112,"Users Score":0,"Answer":"The issue was that the Apache was built with VC14, but Python 2.7 naturally with VC9. Installing an Apache built with VC9 solved my issue.","Q_Score":0,"Tags":"python,apache,mod-wsgi,windows-server-2008-r2","A_Id":46645404,"CreationDate":"2017-10-07T15:46:00.000","Title":"Getting mod_wsgi to work with Python 2.7\/Apache on Windows Server 2012; cannot load module","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"Im going to run query that returns a huge table (about 700Mb) from Redshift and save it to CSV using SQLAlchemy and python 2.7 on my local machine (mac pro).\nI've never done this with such a huge queries before and obviously there could be some memory and other issues. \nMy question is what i shall take into account and how to use sql alchemy in order to make the process work?\nThanks,\nAlex","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1752,"Q_Id":46714971,"Users Score":0,"Answer":"If you don't run much else on that machine then memory should not be an issue. Give it a try. Monitor memory use during the execution. Also use \"load\" to see what pressure on the system is.","Q_Score":0,"Tags":"python,sql,sqlalchemy,amazon-redshift","A_Id":46715732,"CreationDate":"2017-10-12T16:48:00.000","Title":"Python\/SQLAlchemy: How to save huge redshift table to CSV?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"On the face of it, it seems that bindparam should generally be used to eliminate SQL injection. However, in what situations would it necessitate using literal_column instead of bindparam - and what measures should be taken to prevent SQL injection?","AnswerCount":1,"Available Count":1,"Score":0.3799489623,"is_accepted":false,"ViewCount":918,"Q_Id":46719568,"Users Score":2,"Answer":"literal_column is intended to be used as, well, a literal name for a column, not as a parameter (which is a value), because column names cannot be parameterized (it's part of the query itself). You should generally not be using literal_column to put a value in a query, only column names. If you are accepting user input for column names, you should whitelist what those names are.\nOne exception is that sometimes you want to output some really complex expression not directly supported by SQLAlchemy, and literal_column basically allows you to put freeform text in a query. In these cases, you should ensure that user-supplied parts of the expression (i.e. values) are still passed via bind params.","Q_Score":0,"Tags":"python,python-2.7,sqlalchemy","A_Id":46736027,"CreationDate":"2017-10-12T22:02:00.000","Title":"Sqlalchemy When should literal_column or be used instead of bindparam?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Is it possible to query data from InfoPlus 21 (IP21) AspenTech using php?\nI am willing to create a php application that can access tags and historical data from AspenTech Historian.\nIs ODBC my answer? Even thinking that is, I am not quite sure how to proceed.\nUPDATE:\nI ended up using python and pyODBC.\nThis worked like a charm!\nThank you all for supporting.","AnswerCount":3,"Available Count":2,"Score":0.1973753202,"is_accepted":false,"ViewCount":7310,"Q_Id":46730944,"Users Score":3,"Answer":"I am unaware of a method to access IP21 data directly via PHP, however, if you're happy to access data via a web service, there are both REST and a SOAP options.\nBoth methods are extremely fast and responsive.\nAFW Security still applies to clients accessing the Web Services. Clients will require SQL Plus read (at lesast) access.\nSOAP\n\nRequires the \"Aspen SQL plus Web Server\/Service and Health Monitor\" component to be installed on IP21 server (Selected during install of IP21).\nRecent versions of IP21 require a slight modification to the web.config file to allow remote access. If you cannot execute the web service remotely, try doing it locally (i.e. on the same machine as the IP21 server) and see if this is an issue. \n\nExample: http:\/\/IP21ServerHostName\/SQLPlusWebService\/SQLplusWebService.asmx\/ExecuteSQL?command=select%20*%20from%20compquerydef;\n\n\nREST\n\nMy preference (over SOAP), as it is super easy to access using JQuery (JavaScript) - a couple of lines of code!\nUnsure of exactly what IP21 component is required on install for this, but it appears to be on most of my IP21 servers already.\nArguments in the URL can control the number of rows returned (handy).\nIf using within Jquery \/ JavaScript, web page must be hosted on the AspenOneServerHostName machine, else you'll run into Cross-Origin Resource Sharing (CORS) issues.\n\nExample: \nhttp:\/\/AspenOneServerHostName\/ProcessData\/AtProcessDataREST.dll\/SQL?%3CSQL%20c=%22DRIVER={AspenTech%20SQLplus};HOST=IP21ServerHostName;Port=10014;CHARINT=N;CHARFLOAT=N;CHARTIME=N;CONVERTERRORS=N%22%20m=%22DesiredMaxNumberOfRowsReturned%22%20s=%221%22%3E%3C![CDATA[select%20*%20from%20compquerydef]]%3E%3C\/SQL%3E\n\nNotes:\n\n\nAspenOneServerHostName can be the same as IP21ServerHostName\nAspenOneServerHostName must have ADSA configured to view IP21ServerHostName\nReplace DesiredMaxNumberOfRowsReturned with a number","Q_Score":2,"Tags":"php,python,odbc,aspen","A_Id":46762657,"CreationDate":"2017-10-13T13:18:00.000","Title":"How to query data from an AspenTech IP21 Historian using PHP?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Is it possible to query data from InfoPlus 21 (IP21) AspenTech using php?\nI am willing to create a php application that can access tags and historical data from AspenTech Historian.\nIs ODBC my answer? Even thinking that is, I am not quite sure how to proceed.\nUPDATE:\nI ended up using python and pyODBC.\nThis worked like a charm!\nThank you all for supporting.","AnswerCount":3,"Available Count":2,"Score":0.1325487884,"is_accepted":false,"ViewCount":7310,"Q_Id":46730944,"Users Score":2,"Answer":"Yes ODBC driver should be applicable to meet your requirement. We have already developed an application to insert the data into IP21 historian which uses same protocol. Similarly some analytical tools (e.g. Seeq Cooperation) also uses ODBC to fetch the data from IP21 historian. Therefore it should be possible in your case as well.","Q_Score":2,"Tags":"php,python,odbc,aspen","A_Id":50016010,"CreationDate":"2017-10-13T13:18:00.000","Title":"How to query data from an AspenTech IP21 Historian using PHP?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm running into a performance issue with Google Cloud Bigtable Python Client. I'm working on a flask API that writes to and reads from a GCP Bigtable instance. The API uses the python client to communicate with Bigtable, and was deployed to GCP App Engine flexible environment.\nUnder low traffic, the API works fine. However during a load test, the endpoints that reads and writes to Bigtable suffers a huge performance decrease compare to a similar endpoint that doesn't communicate with Bigtable. Also, a large percentage of requests went to the endpoint receives a 502 Bad Gateway, even when health check was turned off in App Engine.\nI'm aware of that the client is currently in Alpha. I wonder if the performance issue is known, or if anyone also ran into the same issue\nUpdate\nI found a documentation from Google stating:\n\nThere are issues with the network connection. Network issues can\n  reduce throughput and cause reads and writes to take longer than\n  usual. In particular, you'll see issues if your clients are not\n  running in the same zone as your Cloud Bigtable cluster.\n\nIn my case, my client is in a different region, by moving it to the same region had a huge increase in performance. However the performance issue still exist, and the recommendation from the documentation is to put client in the same zone as Bigtable.\nI also considered using Container engine or Compute Engine where it is easier to specify the zone, but I want stay with App Engine for its autoscale functionality and managed services.","AnswerCount":1,"Available Count":1,"Score":0.537049567,"is_accepted":false,"ViewCount":503,"Q_Id":46740127,"Users Score":3,"Answer":"Bigtable client take somewhere between 3 ms to 20 ms to complete each request, and because python is single threaded, during that period of time it will just wait until the response comes back. The best solution we found was for any writes, publish the request to Pubsub, then use Dataflow to write to Bigtable. It is significantly faster because publishing a message in Python would take way below 1 ms to complete, and because Dataflow can be set to exactly the same region as Bigtable, and it is easy to parallel, it can write much faster.\nThough it doesn't solve the scenario where you need frequent read or write need to be instantaneous","Q_Score":1,"Tags":"google-app-engine,google-cloud-platform,bigtable,google-cloud-bigtable,google-cloud-python","A_Id":47776406,"CreationDate":"2017-10-14T02:03:00.000","Title":"Google Cloud Bigtable Python Client Performance Issue","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I have MySQL database where I'm loading big files which insert more than 190 000 rows. I'm using python script which is doing some stuff and then load data from csv file into mysql execute query and commit.\nMy question is if I'm sending such a big file, is database ready after commit command or how to trigger when all datas are inserted in database?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":54,"Q_Id":46742682,"Users Score":1,"Answer":"The COMMIT does not actually return until the data has been... committed... so, yes, once you have committed any transaction, the work from that transaction is entirely done, as far as your application is concerned.","Q_Score":0,"Tags":"python,mysql","A_Id":46745333,"CreationDate":"2017-10-14T08:53:00.000","Title":"MySQL commit trigger done","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Im creating Excel file from pandas and I'm using worksheet.hide_gridlines(2)\nthe problem that all gridlines are hide in my current worksheet.I need to hide a range of cells, for example A1:I80.How can I do that?","AnswerCount":2,"Available Count":1,"Score":0.0996679946,"is_accepted":false,"ViewCount":2139,"Q_Id":46745120,"Users Score":1,"Answer":"As far as I know that isn't possible in Excel to hide gridlines for a range. Gridlines are either on or off for the entire worksheet.\nAs a workaround you could turn the gridlines off and then add a border to each cell where you want them displayed.\nAs a first step you should figure out how you would do what you want to do in Excel and then apply that to an XlsxWriter program.","Q_Score":3,"Tags":"excel,python-2.7,xlsxwriter","A_Id":46747332,"CreationDate":"2017-10-14T13:29:00.000","Title":"Set worksheet.hide_gridlines(2) to certain range of cells","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a website which has been built using HTML and PHP.\nI have a Microsoft SQL Server database. I have connected to this database and created several charts using Python.\nI want to be able to publish these graphs on my website and make the graphs live (so that they are refreshed every 5 minutes or so with latest data). How do I do this?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":161,"Q_Id":46752760,"Users Score":0,"Answer":"You could add a process to crontab to run the Python program every 5 minutes (assuming Linux). You could, alternatively, have the PHP call Python and await the refreshed file before responding with the page.","Q_Score":0,"Tags":"python,html,graph","A_Id":46752813,"CreationDate":"2017-10-15T07:33:00.000","Title":"Live graphs using python on website","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I'm trying to find a way to log all queries done on a Cassandra from a python code. Specifically logging as they're done executing using a  BatchStatement\nAre there any hooks or callbacks I can use to log this?","AnswerCount":3,"Available Count":1,"Score":0.0665680765,"is_accepted":false,"ViewCount":2113,"Q_Id":46773522,"Users Score":1,"Answer":"Have you considered creating a decorator for your execute or equivalent (e.g. execute_concurrent) that logs the CQL query used for your statement or prepared statement?\nYou can write this in a manner that the CQL query is only logged if the query was executed successfully.","Q_Score":10,"Tags":"python,cassandra,cassandra-python-driver","A_Id":46839220,"CreationDate":"2017-10-16T15:12:00.000","Title":"Logging all queries with cassandra-python-driver","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":0},{"Question":"The program would follow the below steps:\n\nClick on executable program made through python \nFile explorer pops up for user to choose excel file to alter\nChoose excel file for executable program to alter \nSpits out txt file OR excel spreadsheet with newly altered data to same folder location as the original spreadsheet","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":123,"Q_Id":46803803,"Users Score":0,"Answer":"Yes this is perfectly doable. I suggest you look at PyQT5 or TkInter for the user interface, pyexcel for the excel interface and pyinstaller for packaging up an executable as you asked. There are many great tutorials on all of these modules.","Q_Score":0,"Tags":"python,excel,file,exe,explorer","A_Id":46803941,"CreationDate":"2017-10-18T06:09:00.000","Title":"Python - how to get executable program to get the windows file browser to pop up for user to choose an excel file or any other document?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"After running some tests (casting a PyMongo set to a list vs iterating over the cursor and saving to a list) I've noticed that the step from cursor to data in memory is negligible. For a db cursor of about 160k records, it averages about 2.3s.\nIs there anyway to make this conversion from document to object faster? Or will I have to choose between casting to a list and iterating over the cursor?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":871,"Q_Id":46817939,"Users Score":0,"Answer":"After some A\/B testing, it seems like there isn't really a way to speed this up, unless you change your Python interpreter. Alternatively, bulk pulling from the DB could speed this up.","Q_Score":3,"Tags":"python,database,python-3.x,mongodb,pymongo","A_Id":53745939,"CreationDate":"2017-10-18T19:37:00.000","Title":"PyMongo Cursor to List Fastest Way Possible","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have different threads running which all write to the same database (though not the same table).\nCurrently I have it setup that I create a connection, and pass that to each thread, which then creates it own cursor for writing.\nI haven't implementing the writing to db part yet, but am wondering if not every thread needs it's own connection?\nThanks!","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":2665,"Q_Id":46869761,"Users Score":0,"Answer":"Each thread should use a distinct connection to avoid problems with inconsistent states and to make debugging easier. On web servers, this is typically achieved by using a pooled connection. Each thread (http request processor) picks up a connection from the pool when it needs it and then returns it back to the pool when done. In your case, you can just create a new connection for each thread and pass it to the thread which can close it when done.","Q_Score":3,"Tags":"multithreading,psycopg2,python-3.6","A_Id":46941465,"CreationDate":"2017-10-22T01:46:00.000","Title":"using python psycopg2: multiple cursors (1 per thread) on same connection","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a PostgreSQL database in which I am collecting reports from 4 different producers. Back when I wrote this I defined 4 different schemas (one per producer) and since the reports are similar in structure each schema has exactly the same tables inside. I'd like to combine the schemas into one and add an extra column with the producer id to the tables.\nAt the moment I have 4 python processes running - one per producer. A process collects a report and inserts it in the DB.\nMy very simple code has been running without crashing for the past few months. The current design makes it impossible for 2 processes to want to insert data into the DB at the same time. If I made the DB changes (single schema with single table) several processes might want to insert data simultaneously. For the moment, I will exclude combining the processes into a single one, please assume I don't do this.\nI am unsure if I need to worry about any special code to handle the case of more than one process inserting data into the DB? I am using python3 + SQLAlchemy + Flask. I would imagine the ACID properties of a DB should automatically handle the case of 2 or more processes wanting to insert data simultaneously (data in report is small and insertion will take less than 1s). Can I combine the schemas without worrying about processes insert collisions?","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":80,"Q_Id":46879611,"Users Score":0,"Answer":"For simple INSERTs, yes, you can safely have four producers adding rows. I'm assuming you don't have long running queries, as consistent reads can require allocating an interesting amount of log space if inserts keep happening during an hour-long JOIN.\n\nif I am inserting large amounts of data and one insert causes another to timeout?\n\nYou suggest that a timeout could arise from multiple competing INSERTs, but I don't understand what might produce that. I don't believe that is a problem you have thus far observed. Readers and writers can contend for locks, but independent INSERTing processes are quite safe. If four processes were doing BEGIN, UPDATE 1, ... UPDATE N, COMMIT, then respecting a global order would matter, but your use case has the advantage of being very simple.","Q_Score":2,"Tags":"python,postgresql,sqlalchemy,flask-sqlalchemy","A_Id":46879648,"CreationDate":"2017-10-22T22:06:00.000","Title":"Can I safely combine my schemas","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a PostgreSQL database in which I am collecting reports from 4 different producers. Back when I wrote this I defined 4 different schemas (one per producer) and since the reports are similar in structure each schema has exactly the same tables inside. I'd like to combine the schemas into one and add an extra column with the producer id to the tables.\nAt the moment I have 4 python processes running - one per producer. A process collects a report and inserts it in the DB.\nMy very simple code has been running without crashing for the past few months. The current design makes it impossible for 2 processes to want to insert data into the DB at the same time. If I made the DB changes (single schema with single table) several processes might want to insert data simultaneously. For the moment, I will exclude combining the processes into a single one, please assume I don't do this.\nI am unsure if I need to worry about any special code to handle the case of more than one process inserting data into the DB? I am using python3 + SQLAlchemy + Flask. I would imagine the ACID properties of a DB should automatically handle the case of 2 or more processes wanting to insert data simultaneously (data in report is small and insertion will take less than 1s). Can I combine the schemas without worrying about processes insert collisions?","AnswerCount":2,"Available Count":2,"Score":1.2,"is_accepted":true,"ViewCount":80,"Q_Id":46879611,"Users Score":1,"Answer":"This won't be a problem if you are using a proper db such as Postgres or MySQL. They are designed to handle this. \nIf you are using sqlite then it could break.","Q_Score":2,"Tags":"python,postgresql,sqlalchemy,flask-sqlalchemy","A_Id":46879647,"CreationDate":"2017-10-22T22:06:00.000","Title":"Can I safely combine my schemas","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I want to add docx.table.Table and docx.text.paragraph.Paragraph objects to documents. \nCurrently\n\ntable = document.add_table(rows=2, cols=2)\n\nWould create a new table inside the document, and table would hold the docx.table.Table object with all its properties.\nWhat I want to do instead is add a table OBJECT to the document that I previously read from another document for example.\nI'm guessing the iterating through every property of the newly added table and the table object I read earlier and setting the values would be enough, but is there an alternative method?\nThank you!","AnswerCount":1,"Available Count":1,"Score":0.3799489623,"is_accepted":false,"ViewCount":1713,"Q_Id":46897003,"Users Score":2,"Answer":"There are a few different possibilities your description would admit, but none of them have direct API support in python-docx.\nThe simplest case is copying a table from one part of a python-docx Document object to another location in the same document. This can probably be accomplished by doing a deep copy of the XML for the table. The details of how to do this are beyond the scope of this question, but there are some examples out there if you search on \"python-docx\" OR \"python-pptx\" deepcopy.\nMore complex is copying a table between one Document object and another. A table may contain external references that are available in the source document but not the target document. Consequently, a deepcopy approach will not always work in this case without locating and resolving any dependencies.\nFinally, there is copying\/embedding a table OLE object, such as might be found in a PowerPoint presentation or formed from a range in an Excel document. Embedding OLE objects is not supported and is not likely to be added anytime soon, mostly because of the obscurity of the OLE format embedding format (not well documented).","Q_Score":0,"Tags":"python,python-docx","A_Id":46897992,"CreationDate":"2017-10-23T19:22:00.000","Title":"python-docx add table object to document","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am building a warehouse consisting of data that's found from a public facing API.  In order to store & analyze the data, I'd like to save the JSON files I'm receiving into a structured SQL database.  Meaning, all the JSON contents shouldn't be contained in 1 column.  The contents should be parsed out and stored in various other tables in a relational database.\nFrom a process standpoint, I need to do the following:\n\nCall API\nReceive JSON\nParse JSON file\nInsert\/Update table(s) in a SQL database\n\n(This process will be repeated hundreds and hundreds of times)\nIs there a best practice to accomplish this - from either a process or resource standpoint?  I'd like to do this in Python if possible.  \nThanks.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1594,"Q_Id":46898834,"Users Score":0,"Answer":"You should be able to use json.dumps(json_value) to convert your JSON object into a JSON string that can be put into an sql database.","Q_Score":1,"Tags":"python,sql,json,database,data-warehouse","A_Id":46899529,"CreationDate":"2017-10-23T21:28:00.000","Title":"Save JSON file into structured database with Python","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am running a uwsgi application on my linux mint. it has does work with a database and shows it on my localhost. i run it on 127.0.0.1 IP and 8080 port. after that i want to test its performance by ab(apache benchmark).\nwhen i run the app by command uwsgi --socket 0.0.0.0:8080 --protocol=http -w wsgi and get test of it, it works correctly but slowly.\nso i want to run the app with more than one thread to speed up. so i use --threads option and command is uwsgi --socket 0.0.0.0:8080 --protocol=http -w wsgi --threads 8 for example. \nbut when i run ab to test it, after 2 or 3 request, my application stops with some errors and i don't know how to fix it. every time i run it, type of errors are different. some of errors are like these:\n\n(Traceback (most recent call last): 2014, 'Command Out of Sync')\n\nor \n\n(Traceback (most recent call last):   File \".\/wsgi.py\", line 13, in\n  application\n      return show_description(id)   File \".\/wsgi.py\", line 53, in show_description\n      cursor.execute(\"select * from info where id = %s;\" %id)   File \"\/home\/mohammadhossein\/myFirstApp\/myappenv\/local\/lib\/python2.7\/site-packages\/pymysql\/cursors.py\",\n  line 166, in execute\n      result = self._query(query)   File \"\/home\/mohammadhossein\/myFirstApp\/myappenv\/local\/lib\/python2.7\/site-packages\/pymysql\/cursors.py\",\n  line 322, in _query\n      conn.query(q)   File \"\/home\/mohammadhossein\/myFirstApp\/myappenv\/local\/lib\/python2.7\/site-packages\/pymysql\/connections.py\",\n  line 856, in query\n      self._affected_rows = self._read_query_result(unbuffered=unbuffered) 'Packet sequence number\n  wrong - got 1 expected 2',)   File\n  \"\/home\/mohammadhossein\/myFirstApp\/myappenv\/local\/lib\/python2.7\/site-packages\/pymysql\/connections.py\",\n  line 1057, in _read_query_result\n\nor \n\n('Packet sequence number wrong - got 1 expected 2',) Traceback (most\n  recent call last):\n\nor \n\n('Packet sequence number wrong - got 1 expected 2',) Traceback (most\n  recent call last):   File \".\/wsgi.py\", line 13, in application\n      return show_description(id)   File \".\/wsgi.py\", line 52, in show_description\n      cursor.execute('UPDATE info SET  views = views+1 WHERE id = %s;', id)   File\n  \"\/home\/mohammadhossein\/myFirstApp\/myappenv\/local\/lib\/python2.7\/site-packages\/pymysql\/cursors.py\",\n  line 166, in execute\n      result = self._query(query)\n\nPlease help me how to run my uwsgi application wiht more than one thread safety. any help will be welcome","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":238,"Q_Id":46927517,"Users Score":0,"Answer":"it has solved.\nthe point is that you should create separate connection for each completely separate query to avoid missing data during each query execution","Q_Score":0,"Tags":"python,multithreading,server,uwsgi","A_Id":47568008,"CreationDate":"2017-10-25T08:26:00.000","Title":"uwsgi application stops with error when running it with multi thread","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I am trying to get the current user of the db I have. But I couldn't find a way to do that and there are no questions on stackoverflow similar to this. In postgresql there is a method current_user. For example I coudl just say SELECT current_user and I would get a table with the current user's name. Is there something similar in Sqlalchemy?","AnswerCount":3,"Available Count":1,"Score":0.0665680765,"is_accepted":false,"ViewCount":2399,"Q_Id":47038961,"Users Score":1,"Answer":"If you use flask-login module of Flask you could just import a function current_user with from flask_login import current_user.\nThen you could just get it from the database and db model (for instance Sqlite\/SqlAlchemy) if you save it in a database:\nu_id = current_user.id\nu_email = current_user.email\nu_name = current_user.name\netc.","Q_Score":1,"Tags":"python,python-2.7,sqlalchemy","A_Id":65727720,"CreationDate":"2017-10-31T15:24:00.000","Title":"SqlAlchemy current db user","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I use Pandas with Jupyter notebook a lot. After I ingest a table in from using pandas.read_sql, I would preview it by doing the following:\ndata = pandas.read_sql(\"\"\"blah\"\"\")\n data\nOne problem that I have been running into is that all my preview tables will disappear if I reopen my .ipynb\nIs there a way to prevent that from happening?\nThanks!","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":71,"Q_Id":47042689,"Users Score":0,"Answer":"Are you explicitly saving your notebook before you re-open it? A Jupyter notebook is really just a large json object, eventually rendered as a fancy html object. If you save the notebook, illustrations and diagrams should be saved as well. If that doesn't do the trick, try putting the one-liner \"data\" in a different cell than read_sql().","Q_Score":0,"Tags":"python,ipython,jupyter-notebook,ipython-notebook","A_Id":47042891,"CreationDate":"2017-10-31T18:53:00.000","Title":"How to prevent charts or tables to disappear when I re-open Jupyter Notebook?","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I need to read the whole geoip2 database and insert that data into SQL lite database. I tried to read the .mmdb file in the normal way but it prints random characters.","AnswerCount":1,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":845,"Q_Id":47047727,"Users Score":1,"Answer":"You should be able to download CSV file and import it into SQL lite.","Q_Score":0,"Tags":"python,maxmind,geoip2","A_Id":47048122,"CreationDate":"2017-11-01T03:21:00.000","Title":"Can we read the geoip2 database file with .mmdb format like normal file in Python?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"When I run from flask.ext.mysql import MySQL I get the warning Importing flask.ext.mysql is deprecated, use flask_mysql instead. \nSo I installed flask_mysql using pip install flask_mysql,installed it successfully but then when I run from flask_mysql import MySQL I get the error No module named flask_mysql. In the first warning I also get  Detected extension named flaskext.mysql, please rename it to flask_mysql. The old form is deprecated.\n  .format(x=modname), ExtDeprecationWarning. Could you please tell me how exactly should I rename it to flask_mysql? \nThanks in advance.","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":3318,"Q_Id":47116912,"Users Score":3,"Answer":"flask.ext. is a deprecated pattern which was used prevalently in older extensions and tutorials. The warning is telling you to replace it with the direct import, which it guesses to be flask_mysql. However, Flask-MySQL is using an even more outdated pattern, flaskext.. There is nothing you can do about that besides convincing the maintainer to release a new version that fixes it. from flaskext.mysql import MySQL should work and avoid the warning, although preferably the package would be updated to use flask_mysql instead.","Q_Score":4,"Tags":"python,mysql,flask","A_Id":47117043,"CreationDate":"2017-11-05T00:06:00.000","Title":"Python flask.ext.mysql is deprecated?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm trying to use wb = load_workbook(filename) but either I work in Python console or call it from a script, it hangs for a while, then my laptop completely freezes. I can't switch to console to reboot, can't restart X etc. (UPD: CPU consumption is 100% in this moment, memory consump. is 5% only). Has anybody met such issue?\nPython 2.7, openpyxl 2.4.9","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":1046,"Q_Id":47123188,"Users Score":0,"Answer":"The warning is exactly that, a warning about some aspect of the file being removed. But it has nothing to do with the rest of the question. I suspect you are running out of memory. How much memory is openpyxl using when the laptop freezes?","Q_Score":1,"Tags":"python,openpyxl","A_Id":47125299,"CreationDate":"2017-11-05T15:19:00.000","Title":"openpyxl load_workbook() freezes","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I'm trying to use wb = load_workbook(filename) but either I work in Python console or call it from a script, it hangs for a while, then my laptop completely freezes. I can't switch to console to reboot, can't restart X etc. (UPD: CPU consumption is 100% in this moment, memory consump. is 5% only). Has anybody met such issue?\nPython 2.7, openpyxl 2.4.9","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":1046,"Q_Id":47123188,"Users Score":0,"Answer":"I had this issue kinda.... I had been editing my excel workbook. I ended up accidentally pasting a space  into an almost infinite amount of rows. ya know... like a lot. I selected all empty cells and hit delete, saved workbook, problem gone.","Q_Score":1,"Tags":"python,openpyxl","A_Id":64410841,"CreationDate":"2017-11-05T15:19:00.000","Title":"openpyxl load_workbook() freezes","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I want to insert date and time into mongo ,using pymongo.\nHowever, I can insert datetime but not just date or time .\nhere is the example code :\nnow = datetime.datetime.now()\nlog_date = now.date()\nlog_time = now.time()\nself.logs['test'].insert({'log_date_time': now, 'log_date':log_date, 'log_time':log_time})\nit show errors :\nbson.errors.InvalidDocument: Cannot encode object: datetime.time(9, 12, 39, 535769)\nin fact , i don't know how to insert just date or time in mongo shell  too.\ni  know insert datetime is new Date(), but I just want the date or time filed.","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":515,"Q_Id":47148516,"Users Score":0,"Answer":"You are experiencing the defined behavior.  MongoDB has a single datetime type (datetime).   There are no separate, discrete types of just date or just time.\nWorkarounds:  Plenty, but food for thought:\nStoring just date is straightforward:  assume Z time, use a time component of 00:00:00, and ignore the time offset upon retrieval.\nStoring just time is trickier but doable:  establish a base date like the epoch and only vary the time component, and ignore the date component upon retrieval.","Q_Score":0,"Tags":"python,mongodb,datetime,pymongo","A_Id":47148634,"CreationDate":"2017-11-07T01:23:00.000","Title":"questions about using pymongo to insert date and time into mongo","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I wonder how does Postgres sever determine to close a DB connection, if I forgot at the Python source code side. \nDoes the Postgres server send a ping to the source code? From my understanding, this is not possible.","AnswerCount":2,"Available Count":1,"Score":0.1973753202,"is_accepted":false,"ViewCount":41,"Q_Id":47166301,"Users Score":2,"Answer":"When your script quits your connection will close and the server will clean it up accordingly. Likewise, it's often the case in garbage collected languages like Python that when you stop using the connection and it falls out of scope it will be closed and cleaned up.\nIt is possible to write code that never releases these resources properly, that just perpetually creates new handles, something that can be problematic if you don't have something server-side that handles killing these after some period of idle time. Postgres doesn't do this by default, though it can be configured to, but MySQL does.\nIn short Postgres will keep a database connection open until you kill it either explicitly, such as via a close call, or implicitly, such as the handle falling out of scope and being deleted by the garbage collector.","Q_Score":0,"Tags":"python,database,postgresql","A_Id":47166411,"CreationDate":"2017-11-07T19:49:00.000","Title":"How does Postges Server know to keep a database connection open","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am deploying a Jupyter notebook(using python 2.7 kernel) on client side which accesses data on a remote and does processing in a remote Spark standalone cluster (using pyspark library). I am deploying spark cluster in Client mode. The client machine does not have any Spark worker nodes.\nThe client does not have enough memory(RAM). I wanted to know that if I perform a Spark action operation on dataframe like df.count()on client machine, will the dataframe be stored in Client's RAM or will it stored on Spark worker's memory?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":187,"Q_Id":47173286,"Users Score":0,"Answer":"If i understand correctly, then what you will get on the client side is an int. At least should be, if setup correctly. So the answer is no, the DF is not going to hit your local RAM.\nYou are interacting with the cluster via SparkSession (SparkContext for earlier versions). Even though you are developing -i.e. writing code- on the client machine, the actual computation of spark operations -i.e. running pyspark code-  will not be performed on your local machine.","Q_Score":0,"Tags":"python,pyspark,apache-spark-sql,spark-dataframe","A_Id":47173911,"CreationDate":"2017-11-08T06:50:00.000","Title":"Where is RDD or Spark SQL dataframe stored or persisted in client deploy mode on a Spark 2.1 Standalone cluster?","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have made several tables in a Postgres database in order to acquire data with time values and do automatic calculation in order to have directly compiled values. Everything is done using triggers that will update the right table in case of modification of values.\nFor example, if I update or insert a value measured @ 2017-11-06 08:00, the trigger will detect this and do the update for daily calculations; another one will do the update for monthly calculations, and so...\nRight now, everything is working well. Data acquisition is done in python\/Qt to update the measured values using pure SQL instruction (INSERT\/UPDATE\/DELETE) and automatic calculation are working. \nEverything is working well too when I use an interface like pgAdmin III to change values.\nMy problem comes with development in django to display and modify the data. Up to now, I did not have any problem as I just displayed data without trying to modify them. But now I don't understand what's going on...\nIf I insert a new value using model.save(), eveything is working: the hourly measure is written, the daily, monthly and yearly calculation are done.\nBut if I update an existing value, the triggers seem to not see the modification: the hourly measure is updated (so model.save() do the job), but the daily calculation trigger seems not to be launched as the corresponding table is not updated. As said previously, manually updating the same value with pgAdmin III works: the hourly value is updated, the daily calculation is done.\nI do not understand why the update process of django seems to disable my triggers...\nI have tried to use the old save algorithm (select_on_save = True), but without success.\nThe django account of the database is owning all the tables, triggers and functions. He has execute permission on all triggers and functions. And again, inserting an item with django is working using the same triggers and functions.\nMy solution for the moment is to use direct SQL instruction with python\/Qt to do the job, but I feel a bit frustrating not to be able to use only django API...\nDoes anybody have some idea to debug or solve this issue?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1413,"Q_Id":47209114,"Users Score":0,"Answer":"Problem was resulting from an error of time zone management.","Q_Score":0,"Tags":"python,django,postgresql,database-trigger","A_Id":47226539,"CreationDate":"2017-11-09T18:29:00.000","Title":"Issues with django and postgresql triggers","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am looking for another method to convert .accdb to .db without using csv exporting and separator method to create the new database. Do Access has built-in option to export files into .db?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":1624,"Q_Id":47247790,"Users Score":2,"Answer":"Access has built-in ODBC support.\nYou can use ODBC to export tables to SQLite. You do need to create the database first.","Q_Score":0,"Tags":"python,sqlite,ms-access","A_Id":47248148,"CreationDate":"2017-11-12T10:35:00.000","Title":"How to convert .accdb to db","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I've got a google app engine application that loads time series data real-time into a google datastore nosql style table. I was hoping to get some feedback around the right type of architecture to pull this data into a web application style chart (and ideally something I could also plug into a content management system like Word Press).\nMost of my server-side code is python. What's a reasonable client-server setup to pull the data from the datastore database and display into my webpage? Ideally I'd have something that scales and doesn't cause an unnecessary number of reads on my database (potentially using google-app-engine's built in caching\/etc).\nI'm guessing this is a common use-case but I'd like to get an idea of what might be some best practices around this. I've seen some examples using client web side javascript\/ajax with server side php to read the DB- is this really the best way?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":70,"Q_Id":47254930,"Users Score":0,"Answer":"Welcome to \"it depends\".\nYou have some choices. Imagine the classic four-quadrant chart. Along one axis is data size, along the other is staleness\/freshness.\nIf your time-series data changes rapidly but is small enough to safely be retrieved within a request, you can query for it on demand, convert it to JSON, and squirt it to the browser to be rendered by the JavaScript charting package of your choice. If the data is large, your app will need to do some sort of server-side pre-processing so that when the data is needed, it can be retrieved in sufficiently fewer requests that that the request won't time out. This might involve something data dependent like pre-bucketing the time series.  \nIf the data changes slowly, you have the option of generating your chart on the server side, perhaps using matplotlib. When new data is ingested, or perhaps at intervals, spawn off a task to generate and cache the chart (or JSON to hand to the front-end) as a blob in the datastore. If the data is sufficiently large that a task will timeout, you might need to use a backend process. If the data is sufficiently large and you don't pre-process, you're in the quadrant of unhappiness.\nIn my experience, GAE memcache is best for caching data between requests where the time between requests is very short. Don't rely on generating artifacts, stuff them in memcache and hoping that they'll be there a few minutes later. I've rarely seen that work.","Q_Score":0,"Tags":"python,wordpress,google-app-engine,charts,google-cloud-datastore","A_Id":47257054,"CreationDate":"2017-11-12T22:55:00.000","Title":"Load chart data into a webapp from google datastore","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":1,"Web Development":1},{"Question":"I've used Excel in the past to fetch daily price data on more than 1000 equity securities over a period of a month and it was a really slow experience (1 hour wait in some circumstances) since I was making a large amount of calls using the Bloomberg Excel Plugin. \nI've always wondered if there was a substantial performance improvement to do the same task if I was using Python or Java to pull data from Bloomberg's API instead.\nWould like to know from those who have had experience with both Excel and a programming language before I dive head first into trying to implement a Python or Java solution.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":418,"Q_Id":47319322,"Users Score":1,"Answer":"I have only used the Python API, and via wrappers. As such I imagine there are ways to get data faster than what I currently do.\nBut for what I do, I'd say I can get a few years of daily data for roughly 50 securities in a matter of seconds.\nSo I imagine it could improve your workflow to move to a more robust API.\nRegarding intraday data on the other hand I don't find much improvement. But I am not using concurrent calls (which I'm sure would help my speed on that front).","Q_Score":0,"Tags":"java,python,excel,api,bloomberg","A_Id":47331288,"CreationDate":"2017-11-15T23:54:00.000","Title":"Accessing Bloomberg's API through Excel vs. Python \/ Java \/ other programming languages","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am using the Python3, Django and database as Postgresql, and I wanted to use the Thingsboard dashboard in my web application. can anyone pls guide me how can I use this","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":304,"Q_Id":47454686,"Users Score":0,"Answer":"ThingsBoard has APIs which you can use. You may also customise it based on your requirements.","Q_Score":0,"Tags":"django,python-3.x,postgresql,mqtt,thingsboard","A_Id":47798648,"CreationDate":"2017-11-23T11:41:00.000","Title":"I am using the python django, and i wanted to know to get use thingsboard dashboard, and database as postgresql","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"OS: Ubuntu 17.10\nPython: 2.7\nSUBLIME TEXT 3:\nI am trying to import mysql.connector,\nImportError: No module named connector\nAlthough, when i try import mysql.connector in python shell, it works.\nEarlier it was working fine, I just upgraded Ubuntu and somehow mysql connector is not working.\nI have tried reinstalling mysql connector using pip and git both.\nStill no luck.\nPlease help!","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":722,"Q_Id":47588910,"Users Score":0,"Answer":"I am now using Python 3.6, mysql.connector is working for me best.\nOS: Ubuntu 18.04","Q_Score":2,"Tags":"python,mysql,ubuntu,sublimetext3,mysql-connector","A_Id":52473839,"CreationDate":"2017-12-01T07:55:00.000","Title":"MySQL Connector not Working: NO module named Connector","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"everyone!  I have been using the win32com.client module in Python to access cells of an Excel file containing VBA Macros.  A statement in the code  xl = win32com.client.gencache.EnsureDispatch(\"Excel.Application\")  has been throwing an error:   AttributeError: module 'win32com.gen_py.00020813-0000-0000-C000-000000000046x0x1x6' has no attribute 'MinorVersion'  Has anyone faced a similar situation and, if yes, what can a possible remedy for this? (I've had a look at the source code for win32com on GitHub, but haven't been able to make much sense from it.)","AnswerCount":6,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":17855,"Q_Id":47608506,"Users Score":0,"Answer":"Deletion of the folder as mentioned previously did not work for me.\nI solved this problem by installing a new version of pywin32 using conda. \nconda install -c anaconda pywin32","Q_Score":14,"Tags":"python,excel,win32com","A_Id":61532508,"CreationDate":"2017-12-02T13:41:00.000","Title":"Issue in using win32com to access Excel file","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"everyone!  I have been using the win32com.client module in Python to access cells of an Excel file containing VBA Macros.  A statement in the code  xl = win32com.client.gencache.EnsureDispatch(\"Excel.Application\")  has been throwing an error:   AttributeError: module 'win32com.gen_py.00020813-0000-0000-C000-000000000046x0x1x6' has no attribute 'MinorVersion'  Has anyone faced a similar situation and, if yes, what can a possible remedy for this? (I've had a look at the source code for win32com on GitHub, but haven't been able to make much sense from it.)","AnswerCount":6,"Available Count":3,"Score":0.1651404129,"is_accepted":false,"ViewCount":17855,"Q_Id":47608506,"Users Score":5,"Answer":"A solution is to locate the gen_py folder (C:\\Users\\\\AppData\\Local\\Temp\\gen_py) and delete its content. It works for me when using the COM with another program.","Q_Score":14,"Tags":"python,excel,win32com","A_Id":61842925,"CreationDate":"2017-12-02T13:41:00.000","Title":"Issue in using win32com to access Excel file","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"everyone!  I have been using the win32com.client module in Python to access cells of an Excel file containing VBA Macros.  A statement in the code  xl = win32com.client.gencache.EnsureDispatch(\"Excel.Application\")  has been throwing an error:   AttributeError: module 'win32com.gen_py.00020813-0000-0000-C000-000000000046x0x1x6' has no attribute 'MinorVersion'  Has anyone faced a similar situation and, if yes, what can a possible remedy for this? (I've had a look at the source code for win32com on GitHub, but haven't been able to make much sense from it.)","AnswerCount":6,"Available Count":3,"Score":1.0,"is_accepted":false,"ViewCount":17855,"Q_Id":47608506,"Users Score":6,"Answer":"Renaming the GenPy folder should work.\nIt's present at: C:\\Users\\ _insert_username_ \\AppData\\Local\\Temp\\gen_py\nRenaming it will create a new Gen_py folder and will let you dispatch Excel properly.","Q_Score":14,"Tags":"python,excel,win32com","A_Id":55256887,"CreationDate":"2017-12-02T13:41:00.000","Title":"Issue in using win32com to access Excel file","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have an existing sqlite db file, on which I need to make some extensive calculations. Doing the calculations from the file is painfully slow, and as the file is not large (~10 MB), so there should be no problem to load it into memory.\nIs there a way in Python to load the existing file into memory in order to speed up the calculations?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":231,"Q_Id":47702450,"Users Score":-2,"Answer":"You could read all the tables into DataFrames with Pandas, though I'm surprised it's slow. sqlite has always been really fast for me.","Q_Score":0,"Tags":"python,sqlite","A_Id":47702482,"CreationDate":"2017-12-07T19:31:00.000","Title":"Load existing db file to memory Python sqlite?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"If I have two backends, one NodeJS and one Python both of them are accessing the same database. Is it possible to use an ORM for both or is that really bad practice? It seems like that would lead to a maintenance nightmare.","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":184,"Q_Id":47707608,"Users Score":0,"Answer":"It is possible, but it may cause conflicts with table names, constraint names, sequence names and other names which are depend on ORM naming strategy.","Q_Score":0,"Tags":"python,node.js,postgresql,orm","A_Id":47708755,"CreationDate":"2017-12-08T04:13:00.000","Title":"Node ORM and Python ORM for same DB?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"If I have two backends, one NodeJS and one Python both of them are accessing the same database. Is it possible to use an ORM for both or is that really bad practice? It seems like that would lead to a maintenance nightmare.","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":184,"Q_Id":47707608,"Users Score":0,"Answer":"so long as both ORMs put few constraints on the database structure it should be fine.","Q_Score":0,"Tags":"python,node.js,postgresql,orm","A_Id":47708025,"CreationDate":"2017-12-08T04:13:00.000","Title":"Node ORM and Python ORM for same DB?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have MySQL DB\/table with column \"name\" containing one value. Multiple python scripts are accessing the same DB\/table and the same column. There are also two more columns called \"locked\" and \"locked_by\", each script is reading the table and selects 10 entries from \"name\" where \"locked\" is false and update the locked value to True so other script can't take them and do the same work again. At least that is the solution I have for multiple script accessing one column and not tripping all over each other.. BUT!\nI'm worried that between time when one script is updating the \"locked\" status other script takes that value and try to update it and so on.. ending in mess \nIs there some solution to this or am I just worried about non exitant issue ?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":79,"Q_Id":47728923,"Users Score":0,"Answer":"Looks like SQLs: SELECT ... FOR UPDATE would lock the selected row and other processes can't read\/update it until I commit changes.. if I understand correctly","Q_Score":1,"Tags":"python,mysql","A_Id":47729223,"CreationDate":"2017-12-09T13:11:00.000","Title":"How to prevent conflicts while multiple python scripts accessing MySQL DB at once ?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":1,"System Administration and DevOps":0,"Web Development":0},{"Question":"I want to store a list within another list in a database (SQL) without previous data being lost.This is one example of values i have in my database (1, 'Haned', 15, 11, 'Han15', 'password', \"['easymaths', 6]\"). What i want to do is store another piece of information\/data within the list [] without it getting rid of  \"['easymaths', 6]\" so it would look something like  \"['easymaths', 6,'mediummaths', 6]\" and so on.Thank you","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":20,"Q_Id":47730994,"Users Score":0,"Answer":"Though not intended you could join the list by a specific seperator. In turn when you query the selected field you have to convert it into a list again.","Q_Score":0,"Tags":"python,sql,database,list,append","A_Id":47731116,"CreationDate":"2017-12-09T17:06:00.000","Title":"Storing a list within another list in a database without previous information in that list getting lost","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"In the book grokking algorithms, the author said that\n\nIn the worst case, a hash table takes O(n)\u2014linear time\u2014for everything, which is really slow.\n\nIn worst case, I understand that hash function will map all the keys in the same slots, the hash table start a linked list at that slot to store all the items. So for search it will take linear time because you have to scan all the items one by one.\nWhat I don't understand is that for insert and delete, that hash table take linear time to perform. In worst case, all the items are stored in the same slot which points to a linked list. And for linked list, delete and insert take constant time. Why hash table take linear time? \nFor insert, can hash table just append the item at the end of linked list? It will take constant time.","AnswerCount":3,"Available Count":3,"Score":0.0,"is_accepted":false,"ViewCount":2136,"Q_Id":47738554,"Users Score":0,"Answer":"Because in order to insert and delete, you need to make search and search takes O(n) in worst case. Therefore, it should also takes at least O(n) in worst case as well.","Q_Score":3,"Tags":"python,algorithm,data-structures,hash","A_Id":47738572,"CreationDate":"2017-12-10T11:52:00.000","Title":"Why in worst case insert and delete take linear time for hash table?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"In the book grokking algorithms, the author said that\n\nIn the worst case, a hash table takes O(n)\u2014linear time\u2014for everything, which is really slow.\n\nIn worst case, I understand that hash function will map all the keys in the same slots, the hash table start a linked list at that slot to store all the items. So for search it will take linear time because you have to scan all the items one by one.\nWhat I don't understand is that for insert and delete, that hash table take linear time to perform. In worst case, all the items are stored in the same slot which points to a linked list. And for linked list, delete and insert take constant time. Why hash table take linear time? \nFor insert, can hash table just append the item at the end of linked list? It will take constant time.","AnswerCount":3,"Available Count":3,"Score":1.2,"is_accepted":true,"ViewCount":2136,"Q_Id":47738554,"Users Score":0,"Answer":"And for linked list, delete and insert take constant time.\n\nThey don't. They take linear time, because you have to find the item to delete (or the place to insert) first.","Q_Score":3,"Tags":"python,algorithm,data-structures,hash","A_Id":47738575,"CreationDate":"2017-12-10T11:52:00.000","Title":"Why in worst case insert and delete take linear time for hash table?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"In the book grokking algorithms, the author said that\n\nIn the worst case, a hash table takes O(n)\u2014linear time\u2014for everything, which is really slow.\n\nIn worst case, I understand that hash function will map all the keys in the same slots, the hash table start a linked list at that slot to store all the items. So for search it will take linear time because you have to scan all the items one by one.\nWhat I don't understand is that for insert and delete, that hash table take linear time to perform. In worst case, all the items are stored in the same slot which points to a linked list. And for linked list, delete and insert take constant time. Why hash table take linear time? \nFor insert, can hash table just append the item at the end of linked list? It will take constant time.","AnswerCount":3,"Available Count":3,"Score":0.1973753202,"is_accepted":false,"ViewCount":2136,"Q_Id":47738554,"Users Score":3,"Answer":"Delete will not be constant: you will have to visit the whole worst case linked-list to find the object you want to delete. So this would also be a O(n) complexity.\nYou will have the same problem to insert: you don't want any duplicates, therefore, to be sure not to create some of them ,you will have to check the whole linked list.","Q_Score":3,"Tags":"python,algorithm,data-structures,hash","A_Id":47738580,"CreationDate":"2017-12-10T11:52:00.000","Title":"Why in worst case insert and delete take linear time for hash table?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I want to have a checkboxcolumn in my returned table via Django-filter, then select certain rows via checkbox, and then do something with these rows.\nThis is Django-filter: django-filter.readthedocs.io\/en\/1.1.0 This is an example of checkboxcolumn being used in Django-tables2: stackoverflow.com\/questions\/10850316\/\u2026\nMy question is: can I use the checkboxcolumn for a table returned via Django-filter?\nThanks","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1965,"Q_Id":47783328,"Users Score":0,"Answer":"What django-filter does from the perspective of django-tables2 is supplying a different (filtered) queryset. django-tables2 does not care about who composed the queryset, it will just iterate over it and render rows using the models form the queryset.\nSo if you a checkbox column to the table or not, or use django-filter or not, django-tables2 will just render any queryset it gets.\nIf you want to use the checked records for some custom filter, you'll have to do some manual coding, it's not supported out of the box.\nShort answer: yes, you can use django-tables2 with a CheckboxColumn together with django-filter.","Q_Score":1,"Tags":"python,mysql,django,django-filter,django-tables2","A_Id":47835665,"CreationDate":"2017-12-12T23:40:00.000","Title":"Django-filter AND Django-tables2 CheckBoxColumn compatibility","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am looking for a way to require users of a SQL query system to include certain columns in the SELECT query for example require select to have transaction_id column else return error. This is to insure compatibility with other functions.\nI'm using EXPLAIN (FORMAT JSON) to parse query plan as a dictionary but it doesn't provide information about the column names.","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":32,"Q_Id":47789320,"Users Score":0,"Answer":"Have you tried EXPLAIN (VERBOSE)? That shows the column names.\nBut I think it will be complicated \u2013 you'd have to track table aliases to figure out which column belongs to which table.","Q_Score":0,"Tags":"python,postgresql,sqlalchemy","A_Id":47789777,"CreationDate":"2017-12-13T09:13:00.000","Title":"Requiring certain columns in SELECT SQL query for it to go through?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"So I'm trying to store a LOT of numbers, and I want to optimize storage space.\nA lot of the numbers generated have pretty high precision floating points, so:\n0.000000213213 or 323224.23125523 - long, high memory floats.\nI want to figure out the best way, either in Python with MySQL(MariaDB) - to store the number with smallest data size.\nSo 2.132e-7 or 3.232e5, just to basically store it as with as little footprint as possible, with a decimal range that I can specify - but removing the information after n decimals. \nI assume storing as a DOUBLE is the way to go, but can I truncate the precision and save on space too?\nI'm thinking some number formating \/ truncating in Python followed by just normal storage as a DOUBLE would work - but would that actually save any space as opposed to just immediately storing the double with N decimals attached.\nThanks!","AnswerCount":2,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":317,"Q_Id":47842966,"Users Score":1,"Answer":"All python floats have the same precision and take the same amount of storage.  If you want to reduce overall storage numpy arrays should do the trick.","Q_Score":2,"Tags":"python,mysql,types,double,storage","A_Id":47843118,"CreationDate":"2017-12-16T05:53:00.000","Title":"Most efficient way to store scientific notation in Python and MySQL","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Pandas .to_sql is not inserting any records for a dataframe I want to send to sql. Are there any generic reasons why this might be the case? \n\nI am not getting any error messages. The column names appear fine, but the table is entirely empty. \nWhen I try to send over a single column (i.e. data.ix[2]), it actually works. \nHowever, if I try to send over more than one column (data.ix[1:3]), I again get a completely blank table in sql. \n\nI have been using this code for other dataframes and have never encountered this problem. It still runs for other dataframes in my set.","AnswerCount":2,"Available Count":2,"Score":-0.0996679946,"is_accepted":false,"ViewCount":2183,"Q_Id":47878076,"Users Score":-1,"Answer":"I was also facing same issue because dot was added in header. remove dot then it will work.","Q_Score":1,"Tags":"python,sql,python-3.x,postgresql,pandas","A_Id":55399149,"CreationDate":"2017-12-18T23:46:00.000","Title":"Pandas .to_sql is not inserting any records for a dataframe I want to send to sql. Are there any generic reasons why this might be the case?","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"Pandas .to_sql is not inserting any records for a dataframe I want to send to sql. Are there any generic reasons why this might be the case? \n\nI am not getting any error messages. The column names appear fine, but the table is entirely empty. \nWhen I try to send over a single column (i.e. data.ix[2]), it actually works. \nHowever, if I try to send over more than one column (data.ix[1:3]), I again get a completely blank table in sql. \n\nI have been using this code for other dataframes and have never encountered this problem. It still runs for other dataframes in my set.","AnswerCount":2,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":2183,"Q_Id":47878076,"Users Score":0,"Answer":"I fixed this problem - it was becomes some of the column headers had '%' in it. \nI accidentally discovered this reason for the empty tables when I tried to use io and copy_from a temporary csv, instead of to_sql. I got a transaction error based on a % placeholder error. \nAgain, this is specific to passing to PSQL; it went through to SQL Server without a hitch.","Q_Score":1,"Tags":"python,sql,python-3.x,postgresql,pandas","A_Id":47896038,"CreationDate":"2017-12-18T23:46:00.000","Title":"Pandas .to_sql is not inserting any records for a dataframe I want to send to sql. Are there any generic reasons why this might be the case?","Data Science and Machine Learning":1,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have two projects under the same account: \n\nprojectA with BQ and projectB with cloud storage\nprojectA has BQ with dataset and table - testDataset.testTable\nprjectB has cloud storage and bucket - testBucket\nI use python, google cloud rest api\naccount key credentials for every project, with different permissions: projectA key has permissions only for BQ; projectB has permissions only for cloud storage\n\nWhat I need:\nimport data from projectA testDataset.testTable to projectB testBucket\nProblems\n\nof course, I'm running into error Permission denied while I'm trying to do it, because apparently, projectA key does not have permissions for projectB storage and etc\nanother strange issue as I have testBucket in projetB I can't create a bucket with the same name in projectA and getting \n\n\nThis bucket name is already in use. Bucket names must be globally\n  unique. Try another name.\n\nSo, looks like all accounts are connected I guess it means should be possible to import data from one account to another one via API\nWhat can I do in this case?","AnswerCount":1,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":716,"Q_Id":47884227,"Users Score":0,"Answer":"You put this wrong. You need to provide access to the user account on both projects to have accessible across projects. So there needs to be a user authorized to do the BQ thing and also the GCP thing on the different project. \nAlso Bucket names must be globally unique it means I can't create the name as well, it's global (for the entire planet you reserved that name, not just for project)","Q_Score":1,"Tags":"google-bigquery,google-cloud-platform,google-cloud-storage,google-python-api","A_Id":47884399,"CreationDate":"2017-12-19T09:53:00.000","Title":"Import data from BigQuery to Cloud Storage in different project","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a problem figuring out how I can create a table using psycopg2, with IF NOT EXISTS statement, and getting the NOT EXISTS result\nThe issue is that I'm creating a table, and running some CREATE INDEX \/ UNIQUE CONSTRAINT after it was created. If the table already exists - there is no need to create the indexes or constraints","AnswerCount":2,"Available Count":1,"Score":0.0,"is_accepted":false,"ViewCount":1166,"Q_Id":47912529,"Users Score":0,"Answer":"Eventually I ended up adding AUTOCOMMIT = true\nThis is the only way I can make sure all workers see when a table is created","Q_Score":2,"Tags":"python,postgresql,psycopg2","A_Id":48137413,"CreationDate":"2017-12-20T18:47:00.000","Title":"psycopg2 create table if not exists and return exists result","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am using pymysql to connect to a database. I am new to database operations. Is there a status code that I can use to check if the database is open\/alive, something like db.status.","AnswerCount":3,"Available Count":1,"Score":-1.0,"is_accepted":false,"ViewCount":13383,"Q_Id":47973320,"Users Score":-4,"Answer":"It looks like you can create the database object and check if it has been created if it isn't created you can raise an exception \nTry connecting to an obviously wrong db and see what error it throws and you can use that in a try and except block \nI'm new to this as well so anyone with a better answer please feel free to chime in","Q_Score":7,"Tags":"python,pymysql","A_Id":47973362,"CreationDate":"2017-12-26T02:11:00.000","Title":"How to check the status of a mysql connection in python?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I am working with alembic and it automatically creates a table called alembic_revision on your database.  How, do I specify the name of this table instead of using the default name?","AnswerCount":1,"Available Count":1,"Score":1.2,"is_accepted":true,"ViewCount":874,"Q_Id":47979390,"Users Score":8,"Answer":"After you run your init. Open the env.py file and update context.configure, add version_table='alembic_version_your_name as a kwarg.","Q_Score":4,"Tags":"python,sqlalchemy,alembic","A_Id":47979603,"CreationDate":"2017-12-26T13:36:00.000","Title":"Alembic, how do you change the name of the revision database?","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I am trying to build a AWS Lambda function using APi Gateway which utlizes pyodbc python package. I have followed the steps as mentioned in the documentation. I keep getting the following error Unable to import module 'app': libodbc.so.2: cannot open shared object file: No such file or directory when I test run the Lambda function. \nAny help appreciated. I am getting the same error when I deployed my package using Chalice. It seems it could be that I need to install unixodbc-dev. Any idea how to do that through AWS Lambda?","AnswerCount":6,"Available Count":1,"Score":0.0333209931,"is_accepted":false,"ViewCount":6014,"Q_Id":48016091,"Users Score":1,"Answer":"Fisrt, install unixODBC and unixODBC-devel packages using yum install unixODBC unixODBC-devel. This step will install everything required for pyodbc module. \nThe library you're missing is located in \/usr\/lib64 folder on you Amazon Linux instance.\nCopy the library to your python project's root folder (libodbc.so.2 is just a symbolic link, make sure you copy symbolic link and library itself as listed): libodbc.so, libodbc.so.2 and libodbc.so.2.0.0","Q_Score":3,"Tags":"python,amazon-web-services,aws-lambda,chalice","A_Id":50925535,"CreationDate":"2017-12-29T00:40:00.000","Title":"Unable to use pyodbc with aws lambda and API Gateway","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":1,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":1},{"Question":"I have a file that has several tabs that have pivot tables that are based on one data tab. I am able to write the data to the data tab without issue, but I can't figure out how to get all of the tabs with pivot tables to refresh.\nIf this can be accomplished with openpyxl that would be ideal.","AnswerCount":4,"Available Count":2,"Score":0.0,"is_accepted":false,"ViewCount":7810,"Q_Id":48016206,"Users Score":0,"Answer":"Currently what I do is in my template I create a dynamic data range that gets the data from the raw data sheet and then I set that named range to the tables data source.  Then in the pivot table options there is a \"refresh on open\" parameter and I enable that.  When the excel file opens it refreshes and you can see it refresh.  Currently looking for a way to do it in openpyxl but this is where im at","Q_Score":6,"Tags":"python,excel,openpyxl","A_Id":49428497,"CreationDate":"2017-12-29T01:00:00.000","Title":"Using openpyxl to refresh pivot tables in Excle","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0},{"Question":"I have a file that has several tabs that have pivot tables that are based on one data tab. I am able to write the data to the data tab without issue, but I can't figure out how to get all of the tabs with pivot tables to refresh.\nIf this can be accomplished with openpyxl that would be ideal.","AnswerCount":4,"Available Count":2,"Score":0.049958375,"is_accepted":false,"ViewCount":7810,"Q_Id":48016206,"Users Score":1,"Answer":"If the data source range is always the same, you can set each pivot table as \"refresh when open\". To do that, just go to the pivot table tab, click on the pivot table, under \"Analyze\" - > Options -> Options -> Data -> select \"Refresh data when opening the file\". \nIf the data source range is dynamic, you can set a named range, and in the pivot table tab, Change Data Source to the named range. And again set \"refresh when open\". \nSo the above is achieved without using any python package, alternatively you can use openpyxl to refresh. However make sure that you're using the 2.5 release or above, because otherwise the pivot table format will be lost.","Q_Score":6,"Tags":"python,excel,openpyxl","A_Id":52547674,"CreationDate":"2017-12-29T01:00:00.000","Title":"Using openpyxl to refresh pivot tables in Excle","Data Science and Machine Learning":0,"Database and SQL":1,"GUI and Desktop Applications":0,"Networking and APIs":0,"Other":0,"Python Basics and Environment":0,"System Administration and DevOps":0,"Web Development":0}]