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2009-04-29T08:28:00.000

c#,winforms,ironpython

IronRuby comes with a command line interpreter. Doesn't IronPython also have one? If so, the source code would be a good start :) Oh, and if it doesn't, be sure to look at the IronRuby interpreter, because both languages are based on the DLR and are therefore similar enough to learn from both.

I'd like to add "IDLE-like functionality" to C# WinForms application, but I don't quite have an idea how to do that and couldn't find anything useful with Google. So basically I want interactive command line interface, where user could enter some Python code and execute it (not just expressions, should be possible to define new functions). So, where to start? Are there any good tutorials or samples available?

How to create IDLE -like functionality to WinForms application

2009-04-29T11:31:00.000

python,architecture,containers,notifications

You're over-thinking this. Seriously. Python isn't C++; your concerns are non-issues in Python. Just write what makes sense in your problem domain. " Not absolutely good because of circular references." Why not? Circularity is of no relevance here at all. Bidirectional relationships are great things. Use them. Python garbage collects them just fine without any thinking on your part. What possible problem do you have with mutual (birectional) relationships? "...operate only Accounts, and within them, internally, handler operators. This one is a bit limiting because in this case I cannot pass around references to operators. " What? Your Operators are Python objects, pass all you want. All Python objects are (in effect) references, don't sweat it. What possible problem do you have with manipulating Operator objects?

I have two classes: Account and Operator. Account contains a list of Operators. Now, whenever an operator (in the list) receives a message I want to notify Account object to perform some business logic as well. I think of three alternatives on how to achieve this: 1) Hold a reference within Operator to the container [Account] object and call methods directly. Not absolutely good because of circular references. 2) Use events. As far as I know there is no built-in event handling mechanism in Python. So, this one is a bit tricky to implement. 3) Don't send messages to Operators directly. Instead, operate only Accounts, and within them, internally, handler operators. This one is a bit limiting because in this case I cannot pass around references to operators. I wonder which approach is the most advantageous from the architectural point of view. How do you usually handle this task? It would be great if you could point out snippets in Python.

Notifying container object: best practices

2009-04-29T11:31:00.000

python,architecture,containers,notifications

There is no "one-size-fits-all" solution for the Observer pattern. But usually, it's better to define an EventManager object where interested parties can register themselves for certain events and post these events whenever they happen. It simply creates less dependencies. Note that you need to use a global EventManager instance, which can be problematic during testing or from a general OO point of view (it's a global variable). I strongly advise against passing the EventManager around all the time because that will clutter your code. In my own code, the "key" for registering events is the class of the event. The EventManager uses a dictionary (event class -> list of observers) to know which event goes where. In the notification code, you can then use dict.get(event.__class__, ()) to find your listeners.

I have two classes: Account and Operator. Account contains a list of Operators. Now, whenever an operator (in the list) receives a message I want to notify Account object to perform some business logic as well. I think of three alternatives on how to achieve this: 1) Hold a reference within Operator to the container [Account] object and call methods directly. Not absolutely good because of circular references. 2) Use events. As far as I know there is no built-in event handling mechanism in Python. So, this one is a bit tricky to implement. 3) Don't send messages to Operators directly. Instead, operate only Accounts, and within them, internally, handler operators. This one is a bit limiting because in this case I cannot pass around references to operators. I wonder which approach is the most advantageous from the architectural point of view. How do you usually handle this task? It would be great if you could point out snippets in Python.

Notifying container object: best practices

2009-04-30T05:03:00.000

python,sql,django,stored-procedures,django-models

I guess the improved raw sql queryset support in Django 1.2 can make this easier as you wouldn't have to roll your own make_instance type code.

I am designing a fairly complex database, and know that some of my queries will be far outside the scope of Django's ORM. Has anyone integrated SP's with Django's ORM successfully? If so, what RDBMS and how did you do it?

What is the best way to access stored procedures in Django's ORM

2009-04-30T05:03:00.000

python,sql,django,stored-procedures,django-models

Don't. Seriously. Move the stored procedure logic into your model where it belongs. Putting some code in Django and some code in the database is a maintenance nightmare. I've spent too many of my 30+ years in IT trying to clean up this kind of mess.

I am designing a fairly complex database, and know that some of my queries will be far outside the scope of Django's ORM. Has anyone integrated SP's with Django's ORM successfully? If so, what RDBMS and how did you do it?

What is the best way to access stored procedures in Django's ORM

2009-05-01T03:24:00.000

python

Python is very powerful language, Many big and the very high ranked websites are built on python.. Some big products of python are:- Google (extensively used) Youtube (extensively used) Disqus Eventbrite Pinterest Reddit Quora Mozilla Asana (extensively used) Dropbox (started with python, stayed with python) Even Many companies are shifting their websites from PHP to Python, Because of its efficiency, fast ability, and reliability, and availability of huge support and many good frameworks such as Django.. Moreover, I am not saying that PHP is not a good server side scripting language, But truth is that, most users are adapting python instead of PHP.

What is the biggest software development team that uses Python? I am wondering how well the dynamic type system scales to large development teams. It's pretty clear that at Google they have C++ and Java codebases with thousands of developers; their use of Python is much smaller. Are there some huge companies that develop primarily in Python?

Biggest python projects

2009-05-01T03:24:00.000

python

Among many other Python-centered companies, beyond the ones already mentioned by Unknown, I'd mention big pharma firms such as Astra-Zeneca, film studios such as Lucasfilm, and research places such as NASA, Caltech, Lawrence Livermore NRL. Among the sponsors of Pycon Italia Tre (next week in Firenze, IT -- see www.pycon.it) are Qt/Trolltech (a wholly owned subsidiary of Nokia), Google of course, Statpro, ActiveState, Wingware -- besides, of course, several Italian companies. Among the sponsors of Pycon US in Chicago in March were (of course) Google, as well as Sun Microsystems, Microsoft, Slide.com, Walt Disney Animation Studios, Oracle, Canonical, VMWare -- these are all companies who thought it worthwhile to spend money in order to have visibility to experienced Pythonistas, so presumably ones making significant large-scale use of Python (and in most cases trying to hire experienced Python developers in particular).

What is the biggest software development team that uses Python? I am wondering how well the dynamic type system scales to large development teams. It's pretty clear that at Google they have C++ and Java codebases with thousands of developers; their use of Python is much smaller. Are there some huge companies that develop primarily in Python?

Biggest python projects

2009-05-01T03:24:00.000

python

Our project is over 30,000 lines of Python. That's probably small by some standards. But it's plenty big enough to fill my little brain. The application is mentioned in our annual report, so it's "strategic" in that sense. We're not a "huge" company, so we don't really qualify. A "huge company" (Fortune 1000?) doesn't develop primarily in any single language. Large companies will have lots of development teams, each using a different technology, depending on -- well -- on nothing in particular. When you get to "epic companies" (Fortune 10) you're looking at an organization that's very much like a conglomerate of several huge companies rolled together. Each huge company within an epic company is still a huge company with multiple uncoordinated IT shops doing unrelated things -- there's no "develop primarily in" any particular language or toolset. Even for "large companies" and "small companies" (like ours) you still have fragmentation. Our in-house IT is mostly Microsoft. Our other product development is mostly Java. My team, however, doesn't have much useful specification, so we use Python. We use python because of the duck typing and dynamic programming features. (I don't know what a dynamic type system is -- Python types are static -- when you create an object, its type can never change.) Since no huge company develops primarily in any particular language or toolset, the trivial answer to your question is "No" for any language or tool. And No for Python in particular.

What is the biggest software development team that uses Python? I am wondering how well the dynamic type system scales to large development teams. It's pretty clear that at Google they have C++ and Java codebases with thousands of developers; their use of Python is much smaller. Are there some huge companies that develop primarily in Python?

Biggest python projects

2009-05-04T08:59:00.000

python,networking,ip-address,cidr

#This works properly without the weird byte by byte handling def addressInNetwork(ip,net): '''Is an address in a network''' # Convert addresses to host order, so shifts actually make sense ip = struct.unpack('>L',socket.inet_aton(ip))[0] netaddr,bits = net.split('/') netaddr = struct.unpack('>L',socket.inet_aton(netaddr))[0] # Must shift left an all ones value, /32 = zero shift, /0 = 32 shift left netmask = (0xffffffff << (32-int(bits))) & 0xffffffff # There's no need to mask the network address, as long as its a proper network address return (ip & netmask) == netaddr

Given an ip address (say 192.168.0.1), how do I check if it's in a network (say 192.168.0.0/24) in Python? Are there general tools in Python for ip address manipulation? Stuff like host lookups, ip adddress to int, network address with netmask to int and so on? Hopefully in the standard Python library for 2.5.

How can I check if an ip is in a network in Python?

2009-05-05T02:52:00.000

python,profiling

What if you monkey-patched object's class or another prototypical object? This might not be the easiest if you're not using new-style classes.

Python is so dynamic that it's not always clear what's going on in a large program, and looking at a tiny bit of source code does not always help. To make matters worse, editors tend to have poor support for navigating to the definitions of tokens or import statements in a Python file. One way to compensate might be to write a special profiler that, instead of timing the program, would record the runtime types and paths of objects of the program and expose this data to the editor. This might be implemented with sys.settrace() which sets a callback for each line of code and is how pdb is implemented, or by using the ast module and an import hook to instrument the code, or is there a better strategy? How would you write something like this without making it impossibly slow, and without runnning afoul of extreme dynamism e.g side affects on property access?

What's the best way to record the type of every variable assignment in a Python program?

2009-05-05T16:22:00.000

linux,ubuntu,wxpython

Robin Dunn himself told me that It's using the "native" GTK file dialog, just like the other apps, so there isn't anything that wx can do about it. So as a workaround I ended up installing gvfs-fuse and browsing the network through $HOME/.gvfs.. A bit klunky but it works.

I'm using wx.FileDialog in a wxPython 2.8.8.0 application, under Xubuntu 8.10.. My problem is that this dialog isn't network-aware, so I can't browse Samba shares. I see that this problem plagues other applications too (Firefox, Audacious...) so I'd like to ask where I could find informations on how to make it work. Is that dialog supposed to be already network-aware? Am I missing something? Some library maybe? Or should I write my own implementation? Many thanks!

Network-aware wx.FileDialog

2009-05-05T17:01:00.000

python,exception-handling,try-catch,runtime-error

I know that I can just check for root access before the import, but I'd like to know how to catch this spesific kind of error via a try/except statement for future reference. Is there any way to differentiate between this RuntimeError and others that might be raised? If the error is caused by a specific condition, then I think the easiest way to catch the error is to test for the condition, and you can raise a more specific error yourself. After all the 'error' exists before the error is thrown, since in this case its a problem with the environment. I agree with those above - text matching on an error is kind of a terrifying prospect.

I'm importing a module which raises the following error in some conditions: RuntimeError: pyparted requires root access I know that I can just check for root access before the import, but I'd like to know how to catch this spesific kind of error via a try/except statement for future reference. Is there any way to differentiate between this RuntimeError and others that might be raised?

Catch only some runtime errors in Python

2009-05-05T20:14:00.000

python,google-app-engine,google-cloud-datastore,custompaging

There is no efficient way to do this - in any DBMS. In every case, you have to at least read sequentially through the index records until you find the nth one, then look up the corresponding data record. This is more or less what fetch(count, offset) does in GAE, with the additional limitation of 1000 records. A better approach to this is to keep a 'bookmark', consisting of the value of the field you're ordering on for the last entity you retrieved, and the entity's key. Then, when you want to continue from where you left off, you can add the field's value as the lower bound of an inequality query, and skip records until you match or exceed the last one you saw. If you want to provide 'friendly' page offsets to users, what you can do is to use memcache to store an association between a start offset and a bookmark (order_property, key) tuple. When you generate a page, insert or update the bookmark for the entity following the last one. When you fetch a page, use the bookmark if it exists, or generate it the hard way, by doing queries with offsets - potentially multiple queries if the offset is high enough.

Suppose that I have the model Foo in GAE and this query: query = Foo.all().order('-key') I want to get the n-th record. What is the most efficient way to achieve that? Will the solution break if the ordering property is not unique, such as the one below: query = Foo.all().order('-color') edit: n > 1000 edit 2: I want to develop a friendly paging mechanism that shows pages available (such as Page 1, Page 2, ... Page 185) and requires a "?page=x" in the query string, instead of a "?bookmark=XXX". When page = x, the query is to fetch the records beginning from the first record of that page.

how to get the n-th record of a datastore query

2009-05-05T22:56:00.000

python,unit-testing,dbus,hal

If you can not mock the environment then it's probably impossible for you to write the test. If your access to HAL/D-Bus is via an object and you provide a mock instance to your test then it should be possible to emulate the necessary inputs to your test from the mock implementation.

How does one test a method that does some interactions with the local D-Bus (accessing a HAL object)? Results of tests will differ depending on the system that the test is run on, so I don't know how to provide the method reliable input. I'm working in Python, by the way.

Unit testing for D-Bus and HAL?

2009-05-07T07:45:00.000

python

Set the scheduled task to start the script as minimized.

I have a scheduled task which runs a python script every 10 min so it turns out that a script pops up on my desktop every 10 min how can i make it invincible so my script will work in the background ? I've been told that pythonw will do the work, but I cant figure out how to use it any help ? thanks

How to run a script without being in the tasktray?

2009-05-07T07:45:00.000

python

I've been told that pythonw will do the work, but I cant figure out how to use it Normally you just have to rename the file extension to .pyw. Then it will be executed by pythonw.

I have a scheduled task which runs a python script every 10 min so it turns out that a script pops up on my desktop every 10 min how can i make it invincible so my script will work in the background ? I've been told that pythonw will do the work, but I cant figure out how to use it any help ? thanks

How to run a script without being in the tasktray?

2009-05-07T20:55:00.000

python,google-app-engine,transactions,google-cloud-datastore

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.

in my google app application, whenever a user purchases a number of contracts, these events are executed (simplified for clarity): user.cash is decreased user.contracts is increased by the number contracts.current_price is updated. market.no_of_transactions is increased by 1. in 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. what is the correct approach to this issue? how can I ensure that if a write fails, all preceding writes are rolled back? edit: 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)? edit 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?

datastore transaction restrictions

2009-05-08T18:23:00.000

python,yacc,lex,ply

I typically use a separate 'command reader' to obtain a complete command - probably a line in your case - into a host variable string, and then arrange for the lexical analyzer to analyze the string, including telling me when it didn't reach the end. This is hard to set up, but make some classes of error reporting easier. One of the places I've used this technique routinely has multi-line commands with 3 comment conventions, two sets of quoted strings, and some other nasties to set my teeth on edge (context sensitive tokenization - yuck!). Otherwise, Don's advice with the Yacc 'error' token is good.

Forgive me, I'm completely new to parsing and lex/yacc, and I'm probably in way over my head, but nonetheless: I'm writing a pretty basic calculator with PLY, but it's input might not always be an equation, and I need to determine if it is or not when parsing. The extremes of the input would be something that evaluates perfectly to an equation, which it parses fine and calculates, or something that is nothing like an equation, which fails parsing and is also fine. The gray area is an input that has equation-like parts, of which the parser will grab and work out. This isn't what I want - I need to be able to tell if parts of the string didn't get picked up and tokenized so I can throw back an error, but I have no idea how to do this. Does anyone know how I can define, basically, a 'catch anything that's left' token? Or is there a better way I can handle this?

Tokenizing left over data with lex/yacc

2009-05-08T18:23:00.000

python,yacc,lex,ply

There is a built-in error token in yacc. You would normally do something like: line: goodline | badline ; badline : error '\n' /* Error-handling action, if needed */ goodline : equation '\n' ; Any line that doesn't match equation will be handled by badline. You might want to use yyerrok in the error handling action to ensure error processing is reset for the next line.

Forgive me, I'm completely new to parsing and lex/yacc, and I'm probably in way over my head, but nonetheless: I'm writing a pretty basic calculator with PLY, but it's input might not always be an equation, and I need to determine if it is or not when parsing. The extremes of the input would be something that evaluates perfectly to an equation, which it parses fine and calculates, or something that is nothing like an equation, which fails parsing and is also fine. The gray area is an input that has equation-like parts, of which the parser will grab and work out. This isn't what I want - I need to be able to tell if parts of the string didn't get picked up and tokenized so I can throw back an error, but I have no idea how to do this. Does anyone know how I can define, basically, a 'catch anything that's left' token? Or is there a better way I can handle this?

Tokenizing left over data with lex/yacc

2009-05-08T22:41:00.000

python,windows,scripting,batch-file,io

Try subprocess.Popen(). It allows you to redirect stdout and stderr to files.

I'm trying to write a python script (in windows) that runs a batch file and will take the command line output of that batch file as input. The batch file runs processes that I don't have access to and gives output based on whether those processes are successful. I'd like to take those messages from the batch file and use them in the python script. Anyone have any ideas on how to do this ?

Piping Batch File output to a Python script

2009-05-11T12:24:00.000

c#,c++,python,c,vb.net

Compiling can be done by calling cl.exe which comes with Visual Studio. Of course you could also use GCC instead.

I'm trying to make a vb.net application that has got 2 textboxes, 7 radio buttons and 2 buttons(one named compile and the other 'run'). How can I load the content of a C/C++(or any programming language) file into the 1st textbox and on clicking the compile button, i should be able to show the errors or the C/C++ program in the 2nd textbox. On clicking Run, I should be able to show the output in the 2nd textbox. In short, I want to use the 2nd textbox as a terminal/console. The radio buttons are 4 selecting the language C or C++ or python or C# or java or perl or vb. Are the compilers of all these languages present in .net? If so how can I call them?

How to write a vb.net code to compile C/C++ programs?

2009-05-11T14:55:00.000

python,m2crypto

Possibly its looking up shared libs libssl.so and libcrypto.so and finding the old ones in /usr/lib if you add the new_path to the top of /etc/ld.so.conf so it gets searched first it would work. But this might break other OpenSSL applications expecting old OpenSSL.

M2Crypto provides EC support for ECDSA/ECDH. I have installed OpenSSL 0.9.8i which contains support for EC. However when I run "from M2Crypto import EC,BIO" I get error saying EC_init() failed. So I added debug to print m2.OPENSSL_VERSION_TEXT value. It gets printed as "OpenSSL 0.9.7 19 Feb 2003". This version of OpenSSL doesnot support EC. I tried "python setup.py build build_ext --openssl="new_path where OpenSSL 0.9.8i is installed". Though M2Crypto is built again "Python setup.py install" , I still see that it points to "Old version of OpenSSL". Any Pointers on how to successfully get M2Crypto to use 0.9.8i will be useful.

Python M2Crypto EC Support

2009-05-12T03:20:00.000

python,windows

You can compare len(os.listdir("path")) to zero to see if there are any files in the directory.

Say I want to manipulate some files on a floppy drive or a USB card reader. How do I check to see if the drive in question is ready? (That is, has a disk physically inserted.) The drive letter exists, so os.exists() will always return True in this case. Also, at this point in the process I don't yet know any file names, so checking to see if a given file exists also won't work. Some clarification: the issue here is exception handling. Most of the win32 API calls in question just throw an exception when you try to access a drive that isn't ready. Normally, this would work fine - look for something like the free space, and then catch the raised exception and assume that means there isn't a disk present. However, even when I catch any and all exceptions, I still get an angry exception dialog box from Windows telling me the floppy / card reader isn't ready. So, I guess the real question is - how do I suppress the windows error box?

How do I check if a disk is in a drive using python?

2009-05-12T23:29:00.000

python,django,macos

Unless you are planning on going to production with OS X you might not want to bother. If you must do it, go straight to mod_wsgi. Don't bother with mod_python or older solutions. I did mod_python on Apache and while it runs great now, it took countless hours to set up. Also, just to clarify something based on what you said: You're not going to find a mapping between the url path (like /polls) and a script that is being called. Django doesn't work like that. With Django your application is loaded into memory waiting for requests. Once a request comes in it gets dispatched through the url map that you created in urls.py. That boils down to a function call somewhere in your code. That's why for a webserver like Apache you need a module like mod_wsgi, which gives your app a spot in memory in which to live. Compare that with something like CGI where the webserver executes a specific script on demand at a location that is physically mapped between the url and the filesystem. I hope that's helpful and not telling you something you already knew. :)

I've just completed the very very nice django tutorial and it all went swimmingly. One of the first parts of the tutorial is that it says not to use their example server thingie in production, my first act after the tutorial was thus to try to run my app on apache. I'm running OSX 10.5 and have the standard apache (which refuses to run python) and MAMP (which begrudgingly allows it in cgi-bin). The problem is that I've no idea which script to call, in the tutorial it was always localhost:8000/polls but I've no idea how that's meant to map to a specific file. Have I missed something blatantly obvious about what to do with a .htaccess file or does the tutorial not actually explain how to use it somewhere else?

Running django on OSX

2009-05-12T23:29:00.000

python,django,macos

Yet another option is to consider using a virtual machine for your development. You can install a full version of whatever OS your production server will be running - say, Debian - and run your Apache and DB in the VM. You can connect to the virtual disk in the Finder, so you can still use TextMate (or whatever) on OSX to do your editing. I've had good experiences doing this via VMWare Fusion.

I've just completed the very very nice django tutorial and it all went swimmingly. One of the first parts of the tutorial is that it says not to use their example server thingie in production, my first act after the tutorial was thus to try to run my app on apache. I'm running OSX 10.5 and have the standard apache (which refuses to run python) and MAMP (which begrudgingly allows it in cgi-bin). The problem is that I've no idea which script to call, in the tutorial it was always localhost:8000/polls but I've no idea how that's meant to map to a specific file. Have I missed something blatantly obvious about what to do with a .htaccess file or does the tutorial not actually explain how to use it somewhere else?

Running django on OSX

2009-05-16T12:01:00.000

python,string

You're basically testing whether a member is in a set or not, right? If so, and because you said you have lots of memory, why not just load all the words as keys in memcache, and then for every word, just check if it is present in memcache or not. Or use that data structure that is used by bash to autocomplete command names - this is fast and highly efficient in memory (can't remember the name).

I have a file containing roughly all the words in English (~60k words, ~500k characters). I want to test whether a certain word I receive as input is "in English" (i.e. if this exact word is in the list). What would be the most efficient way to do this in Python? The trivial solution is to load the file into a list and check whether the word is in that list. The list can be sorted, which I believe will shrink the complexity to O(logn). However I'm not sure about how Python implements searching through lists, and whether there's a performance penalty if such a large list is in memory. Can I "abuse" the fact I can put a cap on the length of words? (e.g. say the longest one is 15 characters long). Please note I run the application on a machine with lots of memory, so I care less for memory consumption than for speed and CPU utilization. Thanks

Most Efficient Way to Find Whether a Large List Contains a Specific String (Python)

2009-05-16T12:01:00.000

python,string

Two things: The Python 'mutable set' type has an 'add' method ( s.add(item) ), so you could go right from reading (a line) from your big file straight into a set without using a list as an intermediate data structure. Python lets you 'pickle' a data structure, so you could save your big set to a file and save the time of reinitiating the set. Second, I've been looking for a list of all the single-syllable words in English for my own amusement, but the ones I've found mentioned seem to be proprietary. If it isn't being intrusive, could I ask whether your list of English words can be obtained by others?

I have a file containing roughly all the words in English (~60k words, ~500k characters). I want to test whether a certain word I receive as input is "in English" (i.e. if this exact word is in the list). What would be the most efficient way to do this in Python? The trivial solution is to load the file into a list and check whether the word is in that list. The list can be sorted, which I believe will shrink the complexity to O(logn). However I'm not sure about how Python implements searching through lists, and whether there's a performance penalty if such a large list is in memory. Can I "abuse" the fact I can put a cap on the length of words? (e.g. say the longest one is 15 characters long). Please note I run the application on a machine with lots of memory, so I care less for memory consumption than for speed and CPU utilization. Thanks

Most Efficient Way to Find Whether a Large List Contains a Specific String (Python)

2009-05-16T16:19:00.000

python,ruby,user-interface

I would recommend PyGame.

using Ruby or Python, does someone know how to draw on the screen, covering up any other window? Kind of like, press a key, and the program will show current weather or stock quote on the screen (using the whole screen as the canvas), and then press the key again, and everything restores to the same as before? (like Mac OS X's dash board).

does someone know how to show content on screen (covering up any window) using Ruby or Python?

2009-05-16T16:19:00.000

python,ruby,user-interface

You could use the systems dashboard (desktop widgets, or whatever it's called) API. In order to do that you need bindings to it for Python or Ruby. Alternatively you could use some generic gui toolkit or application framework and just create a frameless window with transparent background. Then you need to be sure that the chosen toolkit supports 'always-on-top' options on your desired platform(s).

using Ruby or Python, does someone know how to draw on the screen, covering up any other window? Kind of like, press a key, and the program will show current weather or stock quote on the screen (using the whole screen as the canvas), and then press the key again, and everything restores to the same as before? (like Mac OS X's dash board).

does someone know how to show content on screen (covering up any window) using Ruby or Python?

2009-05-17T12:09:00.000

python,unix,root,sudo

The concept of "admin-privileges" in our day of fine grained privilege control is becoming hard to define. If you are running on unix with "traditional" access control model, getting the effective user id (available in os module) and checking that against root (0) could be what you are looking for. If you know accessing a file on the system requires the privileges you want your script to have, you can use the os.access() to check if you are privileged enough. Unfortunately there is no easy nor portable method to give. You need to find out or define the security model used, what system provided APIs are available to query and set privileges and try to locate (or possibly implement yourself) the appropriate python modules that can be used to access the API. The classic question, why do you need to find out? What if your script tries to do what it needs to do and "just" catches and properly handles failures?

how can i check admin-privileges for my script during running?

Admin privileges for script

2009-05-17T19:00:00.000

python,file-io,csv,multidimensional-array,fileparsing

I'm looking for a simple solution using Python to store data as a flat file, such that each line is a string representation of an array that can be easily parsed. Is the data only ever going to be parsed by Python programs? If not, then I'd avoid pickle et al (shelve and marshal) since they're very Python specific. JSON and YAML have the important advantage that parsers are easily available for most any language.

I'm looking for a simple solution using Python to store data as a flat file, such that each line is a string representation of an array that can be easily parsed. I'm sure python has library for doing such a task easily but so far all the approaches I have found seemed like it would have been sloppy to get it to work and I'm sure there is a better approach. So far I've tried: the array.toFile() method but couldn't figure out how to get it to work with nested arrays of strings, it seemed geared towards integer data. Lists and sets do not have a toFile method built in, so I would have had to parse and encode it manually. CSV seemed like a good approach but this would also require manually parsing it, and did not allow me to simply append new lines at the end - so any new calls the the CSVWriter would overwrite the file existing data. I'm really trying to avoid using databases (maybe SQLite but it seems a bit overkill) because I'm trying to develop this to have no software prerequisites besides Python.

Simple data storing in Python

2009-05-18T03:15:00.000

python,performance,matplotlib,pyqt

Yes, loading the module takes place at the line where the import statement is. If you create your QApplication and show your splash screen before that, you should be able to do what you want -- also you need to call QApplication.processEvents() whenever you need the splash screen to update with a new message.

My PyQt application that uses matplotlib takes several seconds to load for the first time, even on a fast machine (the second load time is much shorter as the DLLs are kept in memory by Windows). I'm wondering whether it's feasible to show a splash screen while the matplotlib library is being loaded. Where does the actual loading take place - is it when the from line is executed? If so, how can I make this line execute during the splash screen and still be able to use the module throughout the code? A related dilemma is how to test this - can I ask Windows to load the DLLs for every execution and not cache them?

PyQt: splash screen while loading "heavy" libraries

2009-05-20T01:22:00.000

php,python,mysql,ruby,migration

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.

MySQL has a RENAME TABLE statemnt that will allow you to change the name of a table. The manual mentions The rename operation is done atomically, which means that no other session can access any of the tables while the rename is running The 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? In 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?

How does MySQL's RENAME TABLE statment work/perform?

2009-05-25T12:16:00.000

python,plugins,gnome,rhythmbox

You can't import rhythmbox "built-in" modules from a standard python console. As far as I know they aren't real modules, they are just objects from the rhythmbox process exposed to plugins. So you can access them only if you are running your script from the rhythmbox process.

I'm writing a little script for Ubuntu. My intention is to call rhythmbox lyrics plug-in with a global short-cut (configuring gnome) . I can call it from rhythmbox python console, but I don't know how to import rhythmbox built-in modules (eg. rhythmdb). Any ideas?

show lyrics on ubuntu

2009-05-25T12:16:00.000

python,plugins,gnome,rhythmbox

in this case i guess you'll have to write the whole plugin yourself and , then listen to dbus for change of songs in rhythmbox , to detect which song is being played .

I'm writing a little script for Ubuntu. My intention is to call rhythmbox lyrics plug-in with a global short-cut (configuring gnome) . I can call it from rhythmbox python console, but I don't know how to import rhythmbox built-in modules (eg. rhythmdb). Any ideas?

show lyrics on ubuntu

2009-05-25T18:05:00.000

python,hosting

In addition to the other fine answers here, you should be aware that most FTP clients have a chmod command to allow you to set permissions on files at the server. You may not need this if permissions come across properly, but there's a good chance they do not.

My hosting provider says my python script must be made to be executable(chmod755). What does this mean & how do I do it? Cheers!

Making a Python script executable chmod755?

2009-05-28T14:55:00.000

.net,ssis,ironpython

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.

A table has been ETLed to another table. My task is to verify the data between two tables programmatically. One of the difficulties I m facing rite now is: how to use the expression that I can get from, let s say, derived column task and verify with the source and destination. or in other words, how can I use the expression to work in the code. Any ideas....highly appreciated Sagar

How to compare data of two tables transformed in SSIS package

2009-06-01T07:14:00.000

c#,python,ruby,ironpython,ironruby

IronPython 2.0 has a sample compiler called PYC on Codeplex.com/ironpython which can create DLL's (and applications if you need them too). IronPython 2.6 has a newer version of PYC under Tools\script. Cheers, Davy

Does anyone know how to add python and ruby libs as a resource in a dll for deployment? I want to host a script engine in my app, but dont want to have to deploy the entire standard libraries of the respective languages in source files. Is there a simple way to do this so that a require or import statement will find the embedded resources?

Packaging script source files in IronPython and IronRuby

2009-06-01T07:14:00.000

c#,python,ruby,ironpython,ironruby

You could add custom import hook that looks for embedded resources when an import is executed. This is slightly complex and probably not worth the trouble. A better technique would be to fetch all of the embedded modules at startup time, execute them with the ScriptEngine and put the modules you have created into the sys.modules dictionary associated with the engine. This automatically makes them available for import by Python code executed by the engine.

Does anyone know how to add python and ruby libs as a resource in a dll for deployment? I want to host a script engine in my app, but dont want to have to deploy the entire standard libraries of the respective languages in source files. Is there a simple way to do this so that a require or import statement will find the embedded resources?

Packaging script source files in IronPython and IronRuby

2009-06-03T13:19:00.000

python,math

numpy.isnan(number) tells you if it's NaN or not.

float('nan') represents NaN (not a number). But how do I check for it?

How can I check for NaN values?

2009-06-04T17:51:00.000

python,recursion,palindrome

Here's another viewpoint A palindromic string is Some letter, x. Some palindromic substrinng. The same letter, x, repeated. Also, note that you may be given a proper English sentence "Able was I ere I saw Elba." with punctuation. Your palindrome checker may have to quietly skip punctuation. Also, you may have to quietly match without considering case. This is slightly more complex. Some leading punctuation. Some letter, x. Some palindromic substring. Some letter, x, repeated without regard to case. Some trailing punctuation. And, by definition, a zero-length string is a palindrome. Also a single-letter string (after removing punctuation) is a palindrome.

I need help writing a recursive function which detects whether a string is a palindrome. But i can't use any loops it must be recursive. Can anyone help show me how this is done . Im using Python.

Recursive Function palindrome in Python

2009-06-04T17:51:00.000

python,recursion,palindrome

If a string is zero or one letters long, it's a palindrome. If a string has the first and last letters the same, and the remaining letters (I think it's a [1: -1] slice in Python, but my Python is a bit rusty) are a palindrome, it's a palindrome. Now, write that as a palindrome function that takes a string. It will call itself.

I need help writing a recursive function which detects whether a string is a palindrome. But i can't use any loops it must be recursive. Can anyone help show me how this is done . Im using Python.

Recursive Function palindrome in Python

2009-06-06T20:33:00.000

python,qt,widget,designer

I have a single main window with a QGraphicsView and lots of QGraphicsItem objects. Each type of the Items have a different context menu. I find that not being able to create the contextMenu's, or at least the actions that are in them a serious limitation of QtDesigner. It means that I can create about 10% or so of the actions using the designer, and I have to create 90% programaticaly. Compare that with the Microsoft resource editor which allows all of these things to be created, and maintained effortlessly. I hope this will be addressed at some point.

Is there any reason why a QMenu cannot be added from the Qt Designer? I find it weird that you can add other widget types but not this.

how can I add a QMenu and QMenuItems to a window from Qt Designer

2009-06-06T20:33:00.000

python,qt,widget,designer

When you edit a QMainWindow you can right click the window and then choose "create menu bar". Or are you talking about a "context menu" aka "right click menu"?

Is there any reason why a QMenu cannot be added from the Qt Designer? I find it weird that you can add other widget types but not this.

how can I add a QMenu and QMenuItems to a window from Qt Designer

2009-06-06T20:33:00.000

python,qt,widget,designer

Adding menu editing for every widget in the designer would probably make a very awkward and inconvenient UI. There's really no place you can visualize it on. If you're editing a QMainWindow you can edit the menu bar and its popups because there's a proper place for them to be displayed in.

Is there any reason why a QMenu cannot be added from the Qt Designer? I find it weird that you can add other widget types but not this.

how can I add a QMenu and QMenuItems to a window from Qt Designer

2009-06-08T11:30:00.000

javascript,python

I don't know Python good enough to tell you a solution. But if you want to use that to sanitize the user input you have to be very, very careful. Removing stuff between and just doesn't catch everything. Maybe you can have a look at existing solutions (I assume Django includes something like this).

how to remove text between <script> and </script> using python?

how to remove text between using python?

2009-06-08T11:30:00.000

javascript,python

If you're removing everything between <script> and </script> why not just remove the entire node? Are you expecting a resig-style src and body?

how to remove text between <script> and </script> using python?

how to remove text between using python?

2009-06-09T00:29:00.000

python,truncate

You have several options - you can round the number using round(), however this can introduce some inaccuracies (315.15 might round to 315.150000003 for example). If you're just looking to truncate the value of the float when you're displaying it, you can specify the width of the output using printf("%.2f", mynumber). This is probably a better solution, since without knowing more about your specific application it's a good idea in general to keep the entire length of the number for calculation.

How can truncate an input like 315.15321531321 I want to truncate all the values after the hundredths position so it becomes 315.15 how do i do that?

python truncate after a hundreds?

2009-06-09T19:18:00.000

python,django

There's no real rule for this, But one thing I like to do is actually arrange for the index access to redirect to another spot. If you prefer, though, you can just give the index page a plain view. That said, It's probably a good idea to keep all your code in an actual app, so that you can refactor it more easily, and so that it appears on the python path as a normal module. Putting views in the project rather than an app seems to cause more headaches than it solves.

I've been having a look at Django and, from what I've seen, it's pretty darn fantastic. I'm a little confused, however, how I go about implementing a "home page" for my website? Would it be a separate app, or just a view within the project, or what?

Django - Website Home Page

2009-06-10T03:11:00.000

python,shell,zsh,ipython

I asked this question on the zsh list and this answer worked for me. YMMV. In genutils.py after the line if not debug: Remove the line: stat = os.system(cmd) Replace it with: stat = subprocess.call(cmd,shell=True,executable='/bin/zsh') you see, the problem is that that "!" call uses os.system to run it, which defaults to manky old /bin/sh . Like I said, it worked for me, although I'm not sure what got borked behind the scenes.

I have been in love with zsh for a long time, and more recently I have been discovering the advantages of the ipython interactive interpreter over python itself. Being able to cd, to ls, to run or to ! is indeed very handy. But now it feels weird to have such a clumsy shell when in ipython, and I wonder how I could integrate my zsh and my ipython better. Of course, I could rewrite my .zshrc and all my scripts in python, and emulate most of my shell world from ipython, but it doesn't feel right. And I am obviously not ready to use ipython as a main shell anyway. So, here comes my question: how do you work efficiently between your shell and your python command-loop ? Am I missing some obvious integration strategy ? Should I do all that in emacs ?

how to integrate ZSH and (i)python?

2009-06-10T10:42:00.000

python,windows,django-admin

you can't run a command that isn't in your path. it should be set globally when you installed python. type 'set' at a dos prompt and look at the PATH variable. c:\python25 (or whever you installed python) has to be in that variable ie PATH=c:\windows;c:\python25;... etc if it isn't in PATH then you or the installer missed the part where you needed to set it. It can be done from the 'Environment Variables' button in the 'System' control panel.

I have installed python and django in my system that uses win vista. Now when I go to command prompt and type python or django-admin.py both are not working. Every time I need to set the path to the python folder manually. But i have seen these commands running even without setting path. So how do i make it to run properly?

python not starting properly

2009-06-10T10:42:00.000

python,windows,django-admin

Either use the system control panel to set the PATH environment variable that applies permanently or Reinstall Python as a system administrator so that the installer can set the registry and environment variables for you. If you install the "just for me" option, then you have to set the PATH variable in the control panel.

I have installed python and django in my system that uses win vista. Now when I go to command prompt and type python or django-admin.py both are not working. Every time I need to set the path to the python folder manually. But i have seen these commands running even without setting path. So how do i make it to run properly?

python not starting properly

2009-06-10T10:42:00.000

python,windows,django-admin

In your path, I think you need to have both the location of the Python install and the Python\Scripts folder. For example, on XP, I have C:\Python25;C:\Python25\Scripts. Can you verify that you have both?

I have installed python and django in my system that uses win vista. Now when I go to command prompt and type python or django-admin.py both are not working. Every time I need to set the path to the python folder manually. But i have seen these commands running even without setting path. So how do i make it to run properly?

python not starting properly

2009-06-10T23:35:00.000

python,django,vim

Today, you not need special extentions for django autocomplete in vim. Make sure that you have vim with python support. To check it, type in xterm: vim --version|grep python output: +python -python3 +quickfix +reltime +rightleft -ruby +scrollbind +signs ... ... To make work autocomplete, add this lines in your .vimrc: autocmd FileType python set omnifunc=pythoncomplete#Complete if has("python") python import sys,os python sys.path.append('/home/sergey/workspace/django') python os.environ['DJANGO_SETTINGS_MODULE'] = 'djangoProject.settings' endif where: sys.path.append is path to your django workspace directory djangoProject is name of your django project, which is going just after '/home/sergey/workspace/django' Finally, save it and restart vim. Now, after '.', you press default ctrl-x ctrl-o to get your autocomplete.

Does anyone know how to set up auto completion to work nicely with python, django, and vim? I've been trying to use pysmell, but I can't seem to get it set up correctly (or maybe I don't know how it works). Right now, I run pysmell in the django directory (I'm using the trunk) and move the resulting tags to my project directory, then I also run pysmell in the project directory. Vim doesn't pick up the django tags, though, and they don't get auto completed. Does anyone know how to set up auto completion in vim so that it will complete the long django functions (like get_object_or_404) as well as classes/functions in my own code? I have poked around on google but haven't found any good resources. Thanks.

Vim, Python, and Django autocompletion (pysmell?)

2009-06-10T23:35:00.000

python,django,vim

I've had good luck with exuberant-ctags for this. I use this macro in my vimrc: execute 'map :!/usr/bin/exuberant-ctags -f '.&tags.' --recurse '.$_P4ROOT.' ' You'll want to modify that slightly, so that it includes your python /site-packages/django/ directory as well as your own code. Then, hit F2 inside vim to update the tags, and use the regular vim tag bindings to navigate.

Does anyone know how to set up auto completion to work nicely with python, django, and vim? I've been trying to use pysmell, but I can't seem to get it set up correctly (or maybe I don't know how it works). Right now, I run pysmell in the django directory (I'm using the trunk) and move the resulting tags to my project directory, then I also run pysmell in the project directory. Vim doesn't pick up the django tags, though, and they don't get auto completed. Does anyone know how to set up auto completion in vim so that it will complete the long django functions (like get_object_or_404) as well as classes/functions in my own code? I have poked around on google but haven't found any good resources. Thanks.

Vim, Python, and Django autocompletion (pysmell?)

2009-06-12T05:28:00.000

python

Assuming you're talking about a .so file, it's not up to Python to find it -- it's up to the operating system's dynamic library loaded. For Linux, for example, LD_LIBRARY_PATH is the environment variable you need to set.

I have installed lxml which was built using a standalone version of libxml2. Reason for this was that the lxml needed a later version of libxml2 than what was currently installed. When I use the lxml module how do I tell it (python) where to find the correct version of the libxml2 shared library?

How to specify native library search path for python

2009-06-15T09:15:00.000

c++,python,regex,namespaces

That is what I did earlier today: Extract the comment out of the C++ files Use regex to extract the namespace definition Use a simple string search to get the open & close braces positions The various sanity check added show that I am successfully processing 99.925% of my files (5 failures ouf of 6678 files). The issues are due to mismatches in numbers of { and } cause by few '{' or '}' in strings, and unclean usage of the preprocessor instruction. However, I am only dealing with header files, and I own the code. That limits the number of scenari that could cause some issues and I can manually modify the ones I don't cover. Of course I know there are plenty of cases where it would fail but it is probably enough for what I want to achieve. Thanks for your answers.

I am trying to extract the namespaces defined in C++ files. Basically, if my C++ file contains: namespace n1 { ... namespace n2 { ... } // end namespace n2 ... namespace n3 { ...} //end namespace n3 ... } //end namespace n1 I want to be able to retrieve: n1, n1::n2, n1::n3. Does someone have any suggestion of how I could do that using python-regex? Thanks.

Using python regex to extract namespaces from C++ sources

2009-06-15T09:15:00.000

c++,python,regex,namespaces

You could write a basic lexer for it. It's not that hard.

I am trying to extract the namespaces defined in C++ files. Basically, if my C++ file contains: namespace n1 { ... namespace n2 { ... } // end namespace n2 ... namespace n3 { ...} //end namespace n3 ... } //end namespace n1 I want to be able to retrieve: n1, n1::n2, n1::n3. Does someone have any suggestion of how I could do that using python-regex? Thanks.

Using python regex to extract namespaces from C++ sources

2009-06-15T09:15:00.000

c++,python,regex,namespaces

The need is simple enough that you may not need a complex parser. You need to: extract the namespace names count the open/close braces to keep track of where your namespace is defined. This simple approach works if the other conditions are met: you don't get spurious namespace like strings inside comments or inside strings you don't get unmatched open/closeing braces inside comments or strings I don't think this is too much asking from your source.

I am trying to extract the namespaces defined in C++ files. Basically, if my C++ file contains: namespace n1 { ... namespace n2 { ... } // end namespace n2 ... namespace n3 { ...} //end namespace n3 ... } //end namespace n1 I want to be able to retrieve: n1, n1::n2, n1::n3. Does someone have any suggestion of how I could do that using python-regex? Thanks.

Using python regex to extract namespaces from C++ sources

2009-06-15T09:15:00.000

c++,python,regex,namespaces

Searching for the namespace names is pretty easy with a regular expression. However, to determine the nesting level you will have to keep track of the curly bracket nesting level in the source file. This is a parsing problem, one that cannot be solved (sanely) with regular expressions. Also, you may have to deal with any C preprocessor directives in the file which can definitely affect parsing. C++ is a notoriously tricky language to parse completely, but you may be able to get by with a tokeniser and a curly bracket counter.

I am trying to extract the namespaces defined in C++ files. Basically, if my C++ file contains: namespace n1 { ... namespace n2 { ... } // end namespace n2 ... namespace n3 { ...} //end namespace n3 ... } //end namespace n1 I want to be able to retrieve: n1, n1::n2, n1::n3. Does someone have any suggestion of how I could do that using python-regex? Thanks.

Using python regex to extract namespaces from C++ sources

2009-06-15T09:15:00.000

c++,python,regex,namespaces

Most of the time when someone asks how to do something with regex, they're doing something very wrong. I don't think this case is different. If you want to parse c++, you need to use a c++ parser. There are many things that can be done that will defeat a regex but still be valid c++.

I am trying to extract the namespaces defined in C++ files. Basically, if my C++ file contains: namespace n1 { ... namespace n2 { ... } // end namespace n2 ... namespace n3 { ...} //end namespace n3 ... } //end namespace n1 I want to be able to retrieve: n1, n1::n2, n1::n3. Does someone have any suggestion of how I could do that using python-regex? Thanks.

Using python regex to extract namespaces from C++ sources

2009-06-15T19:25:00.000

python,icons,pyqt4

I spent a decent amount of researching this myself not long ago, and my conclusion was that, unfortunately, Qt doesn't provide this functionality in a cross-platform fashion. Ideally the QIcon class would have defaults for file open, save, '+', '-', preferences, etc, but considering it doesn't you'll have to grab the appropriate icon for your desktop environment.

I'm writing a basic program in python using the PyQt4 module. I'd like to be able to use my system theme's icons for things like the preference dialog's icon, but i have no idea how to do this. So my question is, how do you get the location of an icon, but make sure it changes with the system's icon theme? If it matters, i'm developing this under ubuntu 9.04, so i am using the gnome desktop.

System theme icons and PyQt4

2009-06-16T14:09:00.000

python,linux,encryption,passwords

Encrypting the passwords doesn't really buy you a whole lot more protection than storing in plaintext. Anyone capable of accessing the database probably also has full access to your webserver machines. However, if the loss of security is acceptable, and you really need this, I'd generate a new keyfile (from a good source of random data) as part of the installation process and use this. Obviously store this key as securely as possible (locked down file permissions etc). Using a single key embedded in the source is not a good idea - there's no reason why seperate installations should have the same keys.

First, my question is not about password hashing, but password encryption. I'm building a desktop application that needs to authentificate the user to a third party service. To speed up the login process, I want to give the user the option to save his credentials. Since I need the password to authentificate him to the service, it can't be hashed. I thought of using the pyCrypto module and its Blowfish or AES implementation to encrypt the credentials. The problem is where to store the key. I know some applications store the key directly in the source code, but since I am coding an open source application, this doesn't seem like a very efficient solution. So I was wondering how, on Linux, you would implement user specific or system specific keys to increase password storing security. If you have a better solution to this problem than using pyCrypto and system/user specific keys, don't hesitate to share it. As I said before, hashing is not a solution and I know password encryption is vulnerable, but I want to give the option to the user. Using Gnome-Keyring is not an option either, since a lot of people (including myself) don't use it.

How To Reversibly Store Password With Python On Linux?

2009-06-16T18:50:00.000

python,django

Edit: Added some more information about why I present this answer here. I found chartbeat when I tried to answer this same question for my django based site. I don't work for them. Not specifically Django, but chartbeat.com is very interesting to add to a website as well. django-tracking is great, +1 for that answer, etc. Couple of things I could not do with django-tracking, that chartbeat helped with; tracked interactions with completely cached pages which never hit the django tracking code and pages not delivered through django (e.g. wordpress, etc.)

In Django, how can I see the number of current visitors? Or how do I determine the number of active sessions? Is this a good method? use django.contrib.sessions.models.Session, set the expiry time short. Every time when somebody does something on the site, update expiry time. Then count the number of sessions that are not expired.

Number of visitors in Django

2009-06-18T17:57:00.000

wxpython,wxwidgets

from wxPython docs """ longHelpString This string is shown in the statusbar (if any) of the parent frame when the mouse pointer is inside the tool """ so toolbar in notebook doesn't get any statusbar to display long help, so either thru src we should invertigate how it inquires abt status bar and supply a ref to main frame status bar else i think better way is to just override wxToolBar::OnMouseEnter and display help directly on status bar

I have an interface that has two toolbars, one attached to the frame and one embedded in a notebook tab. The one in the frame dutifully shows longHelp strings in the statusbar, the one in the notebook tab does not. How do I tell the one on the notebook tab where to display its help, or do I have to manage enter and leave bindings myself?

wxPython: how to make two toolbars use one statusbar for tooltips?

2009-06-19T04:04:00.000

python,chuck,puredata

I would say learn them all. While it's true that many languages can do many things, specialised languages are usually more expressive and easier to use for a particular task. Case-in-point is while most languages allow shell interaction and process control very few are as well suited to the task as bash scripts. Plugins and libraries can bridge the gap between general and specialised languages but in my experience this is not always without drawbacks - be they speed, stability or complexity. It isn't uncommon to have to compile additional libraries or apply patches or use untrusted and poorly supported modules. It also isn't uncommon that the resulting interface is still harder to use than the original language. I know about 15 languages well and a few of those very well. I do not use my prefered languages when another is more suitable.

I am learning Python because it appeals to me as a mathematician but also has many useful libraries for scientific computing, image processing, web apps, etc etc. It is frustrating to me that for certain of my interests (eletronic music or installation art) there are very specific programming languages which seem better suited to these purposes, such as Max/MSP, PureData, and ChucK -- all quite fascinating. My question is, how should one approach these different languages? Should I simply learn Python and manage the others by using plugins and Python interpreters in them? Are there good tools for integrating the languages, or is the proper way simply to learn all of them?

Synthesis of general programming language (Python) with tailored language (PureData/MaxMSP/ChucK)

2009-06-19T04:04:00.000

python,chuck,puredata

This thread is a little old, but I wanted to point out that the majority of the mature audio development environments e.g. supercollider/max-msp/pure data can be controlled via open sound control. You can google up a better description of OSC, but suffice it to say that it allows you to send control data to synths built in these environments similar to how MIDI works, but way more extensive. This does not solve the problem of actually building synths in python per se but it allows you to "drive" these other environments without having to know the ins and outs of the language.

I am learning Python because it appeals to me as a mathematician but also has many useful libraries for scientific computing, image processing, web apps, etc etc. It is frustrating to me that for certain of my interests (eletronic music or installation art) there are very specific programming languages which seem better suited to these purposes, such as Max/MSP, PureData, and ChucK -- all quite fascinating. My question is, how should one approach these different languages? Should I simply learn Python and manage the others by using plugins and Python interpreters in them? Are there good tools for integrating the languages, or is the proper way simply to learn all of them?

Synthesis of general programming language (Python) with tailored language (PureData/MaxMSP/ChucK)

2009-06-19T19:35:00.000

python,c,linux,security,sandbox

I think your solutions must concentrate on analyzing the source code. I don't know any tools, and I think this would be pretty hard with C, but, for example, a Pascal program which doesn't include any modules would be pretty harmless in my opinion.

I want to create a Web app which would allow the user to upload some C code, and see the results of its execution (the code would be compiled on the server). The users are untrusted, which obviously has some huge security implications. So I need to create some kind of sandbox for the apps. At the most basic level, I'd like to restrict access to the file system to some specified directories. I cannot use chroot jails directly, since the web app is not running as a privileged user. I guess a suid executable which sets up the jail would be an option. The uploaded programs would be rather small, so they should execute quickly (a couple of seconds at most). Hence, I can kill the process after a preset timeout, but how do I ensure that it doesn't spawn new processes? Or if I can't, is killing the entire pgid a reliable method? What would be the best way to go about this - other than "don't do it at all"? :) What other glaring security problems have I missed? FWIW, the web app will be written in Python.

Sandboxing in Linux

2009-06-19T19:35:00.000

python,c,linux,security,sandbox

About the only chance you have is running a VirtualMachine and those can have vulnerabilities. If you want your machine hacked in the short term just use permissions and make a special user with access to maybe one directory. If you want to postpone the hacking to some point in the future then run a webserver inside a virtual machine and port forward to that. You'll want to keep a backup of that because you'll probably have that hacked in under an hour and want to restart a fresh copy every few hours. You'll also want to keep an image of the whole machine to just reimage the whole thing once a week or so in order to overcome the weekly hackings. Don't let that machine talk to any other machine on your network. Blacklist it everywhere. I'm talking about the virtual machine and the physical machine IP addresses. Do regular security audits on any other machines on your other machines on the network. Please rename the machines IHaveBeenHacked1 and IHaveBeenHacked2 and prevent access to those in your hosts lists and firewalls. This way you might stave off your level of hackage for a while.

I want to create a Web app which would allow the user to upload some C code, and see the results of its execution (the code would be compiled on the server). The users are untrusted, which obviously has some huge security implications. So I need to create some kind of sandbox for the apps. At the most basic level, I'd like to restrict access to the file system to some specified directories. I cannot use chroot jails directly, since the web app is not running as a privileged user. I guess a suid executable which sets up the jail would be an option. The uploaded programs would be rather small, so they should execute quickly (a couple of seconds at most). Hence, I can kill the process after a preset timeout, but how do I ensure that it doesn't spawn new processes? Or if I can't, is killing the entire pgid a reliable method? What would be the best way to go about this - other than "don't do it at all"? :) What other glaring security problems have I missed? FWIW, the web app will be written in Python.

Sandboxing in Linux

2009-06-19T19:35:00.000

python,c,linux,security,sandbox

Spawning a new VM under KVM or qemu to compile and run the code looks like the way to go. Running the code under jail/LXC can compromise the machine if it exploits the unsecured parts of the OS like networking code. Advantage of running under a VM are obvious. One can only hack the VM but not the machine itself. But the side effect is you need lots of resources (CPU and Memory) to spawn a VM for each request.

I want to create a Web app which would allow the user to upload some C code, and see the results of its execution (the code would be compiled on the server). The users are untrusted, which obviously has some huge security implications. So I need to create some kind of sandbox for the apps. At the most basic level, I'd like to restrict access to the file system to some specified directories. I cannot use chroot jails directly, since the web app is not running as a privileged user. I guess a suid executable which sets up the jail would be an option. The uploaded programs would be rather small, so they should execute quickly (a couple of seconds at most). Hence, I can kill the process after a preset timeout, but how do I ensure that it doesn't spawn new processes? Or if I can't, is killing the entire pgid a reliable method? What would be the best way to go about this - other than "don't do it at all"? :) What other glaring security problems have I missed? FWIW, the web app will be written in Python.

Sandboxing in Linux

2009-06-21T23:31:00.000

python,ajax,autocomplete,trie

I would use the first option. 'KISS' - (Keep It Simple Stupid). For small amounts of data there shouldn't be much latency. We run the same kind of thing for a name search and results appear pretty quickly on a few thousand rows. Hope that helps, Josh

I'm implementing a "Google Suggest" like autocomplete feature for tag searching using jQuery's autocomplete. I need to provide a web service to jQuery giving it a list of suggestions based on what the user has typed. I see 2 ways of implementing the web service: 1) just store all the tags in a database and search the DB using user input as prefix. This is simple, but I'm concerned about latency. 2) Use an in-process trie to store all the tags and search it for matching results. As everything will be in-process, I expect this to have much lower latency. But there are several difficulties: -What's a good way to initialize the trie on process start up? Presumable I'll store the tag data in a DB and retrieve them and turn them into a trie when I frist start up the process. But I'm not sure how. I'm using Python/Django. -When a new tag is created by a user, I need to insert the new tag into the trie. But let's say I have 5 Django processes and hence 5 tries, how do I tell the other 4 tries that they need to insert a new tag too? -How to make sure the trie is threadsafe as my Django processes will be threaded (I'm using mod_wsgi). Or do I not have to worry about threadsafty because of Python's GIL? -Any way I can store the tag's frequency of use within the trie as well? How do I tell when does the tag's string end and when does the frequency start - eg. if I store apple213 into the trie, is it "apple" with frequency 213 or is it "apple2" with frequency 13?? Any help on the issues above or any suggestions on a different approach would be really appreciated.

What's the best way to implement web service for ajax autocomplete

2009-06-23T14:24:00.000

c#,ironpython

Jonathan helped me to figure out that I had not copied the dll file to the location where IronPython can find it. After copying the dll file to the location, usually it s "c:\Program Files\IronPython 2.0\" unless stated otherwise, I did: import clr clr.AddReference('System.Data') clr.AddReferenceToFile('Sql400.dll') from System.Data import Sql400 from System.Data.Sql400 import *

I was just wondering if anybody knows how to add reference to "Ritmo for iSeries" in IronPython. I did it successfully in C# and get it to work (since it is just click click click) And I was trying to do the same in IronPython but it says, "could not add reference to assembly Ritmo for iSeries". I was doing import clr clr.AddReference('Ritmo for iSeries') from Ritmo........ IOError: Could not add reference to assembly Ritmo for iSeries

how to addreference to Ritmo for iSeries in ironpython

2009-06-23T14:24:00.000

c#,ironpython

You need to use the actual name of the assembly (it won't have spaces). In your C# project, what does it list under the 'references' folder once you've added it as a reference? Try putting that. Also, make sure you've copied the dll for the library to where your IronPython script can find it (if it's not in the GAC).

I was just wondering if anybody knows how to add reference to "Ritmo for iSeries" in IronPython. I did it successfully in C# and get it to work (since it is just click click click) And I was trying to do the same in IronPython but it says, "could not add reference to assembly Ritmo for iSeries". I was doing import clr clr.AddReference('Ritmo for iSeries') from Ritmo........ IOError: Could not add reference to assembly Ritmo for iSeries

how to addreference to Ritmo for iSeries in ironpython

2009-06-24T12:54:00.000

wxpython

stylesheet, not slidesheet. f = open('NAMEOFSTYLESHEET.css','w') f.write('#ID{}\n.class{}')

How to convert HTML CSS file to wxPython files? That is, how to create slidsheet in wxPython like HTML CSS files?

HTML conversion

2009-06-25T11:19:00.000

python,encryption

I looked at the ezPyCrypto library that was recommended in another answer. Please don't use this library. It is very incomplete and in some cases incorrect and highly insecure. Public key algorithms have many pitfalls and need to be implemented carefully. For example, RSA message should use a padding scheme such as PKCS #1, OAEP etc to be secure. This library doesn't pad. DSA signatures should use the SHA1 hash function. This library uses the broken MD5 hash and there is even a bigger bug in the random number generation. Hence the DSA implementation is neither standards conform nor secure. ElGamal is also implemented incorrectly. Following standards does make implementations somewhat more complex. But not following any is not an option. At least not if you care about security.

I need to take a string in Python and encrypt it using a public key. Can anyone give me an example or recommendation about how to go about doing this?

Encrypt a string using a public key

2009-06-25T11:59:00.000

python,web-services,database-design

Server 1: Convert rows to JSON, call the RESTful api of second with JSON data Server 2: listens on a URI e.g. POST /data , get json data convert back to dictionary or ORM objects, insert into db sqlalchemy/sqlobject and simplejson is what you need.

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. Both servers have a MySQL Server and an Apache running. I would like an easy-to-use solution for this. Currently I'm looking into: XMLRPC RestFul Services a simple POST to a processing script socket transfers The 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. Can anyone describe shortly how you would do this the "best-practise" way? This 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. Thanks, Tom

Best Practise for transferring a MySQL table to another server?

2009-06-25T11:59:00.000

python,web-services,database-design

Assuming your situation allows this security-wise, you forgot one transport mechanism: simply opening a mysql connection from one server to another. Me, 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. How 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. Also, would mysql server replication work or would it be to over-blown as a solution?

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. Both servers have a MySQL Server and an Apache running. I would like an easy-to-use solution for this. Currently I'm looking into: XMLRPC RestFul Services a simple POST to a processing script socket transfers The 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. Can anyone describe shortly how you would do this the "best-practise" way? This 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. Thanks, Tom

Best Practise for transferring a MySQL table to another server?

2009-06-26T10:44:00.000

wxpython

You need to give your text control the TE_PASSWORD style. (As Jørn's comment points out, this isn't "encryption" - I'm assuming you're only talking about the visual presentation of the password.)

I am developing an student attendance application in wxpython and I need to know how to ensure that password field doesn't echo characters to the screen. Forexample :if I give the name as moni means then it should be displayed as in format of ****

Hiding characters typed into password field

2009-06-26T16:39:00.000

php,python,perl,parsing,feed

Most modern languages scripting languages allow you to do all of these things. Because of that, I think your choice of language should be based on what you and the people who read your code know. In Perl I'd make use of the following modules: Net::FTP to access the ftp sites. DBI to insert data into your database. Modules like that are nice reusable pieces of code that you don't have to write, and interaction with ftp sites and databases are so common that every modern scripting language should have similar modules. I don't think that PHP is a great language so I'd avoid it if possible, but it might make sense for you if you have a lot of experience in it.