word completion for gnu readline the completer completes keywords builtins and globals in a selectable namespace which defaults to main when completing name name it evaluates the expression up to the last dot and completes its attributes it s very cool to do import sys type sys hit the completion key twice and see the list of names defined by the sys module tip to use the tab key as the completion key call readline parseandbindtab complete notes exceptions raised by the completer function are ignored and generally cause the completion to fail this is a feature since readline sets the tty device in raw or cbreak mode printing a traceback wouldn t work well without some complicated hoopla to save reset and restore the tty state the evaluation of the name name form may cause arbitrary application defined code to be executed if an object with a getattr hook is found since it is the responsibility of the application or the user to enable this feature i consider this an acceptable risk more complicated expressions e g function calls or indexing operations are not evaluated when the original stdin is not a tty device gnu readline is never used and this module and the readline module are silently inactive create a new completer for the command line completernamespace completer instance if unspecified the default namespace where completions are performed is main technically main dict namespaces should be given as dictionaries completer instances should be used as the completion mechanism of readline via the setcompleter call readline setcompletercompletermynamespace complete don t bind to namespace quite yet but flag whether the user wants a specific namespace or to use main dict this will allow us to bind to main dict at completion time not now return the next possible completion for text this is called successively with state 0 1 2 until it returns none the completion should begin with text compute matches when text is a simple name return a list of all keywords builtin functions and names currently defined in self namespace that match compute matches when text contains a dot assuming the text is of the form name name name and is evaluable in self namespace it will be evaluated and its attributes as revealed by dir are used as possible completions for class instances class members are also considered warning this can still invoke arbitrary c code if an object with a getattr hook is evaluated get the content of the object except builtins bpo44752 thisobject word is a method decorated by property what follows applies a postfix if thisobject word is callable but know we know that this is not callable because it is a property also getattrthisobject word will evaluate the property method which is not desirable release references early at shutdown the readline module s contents are quasiimmortal and the completer function holds a reference to globals create a new completer for the command line completer namespace completer instance if unspecified the default namespace where completions are performed is __main__ technically __main__ __dict__ namespaces should be given as dictionaries completer instances should be used as the completion mechanism of readline via the set_completer call readline set_completer completer my_namespace complete don t bind to namespace quite yet but flag whether the user wants a specific namespace or to use __main__ __dict__ this will allow us to bind to __main__ __dict__ at completion time not now return the next possible completion for text this is called successively with state 0 1 2 until it returns none the completion should begin with text compute matches when text is a simple name return a list of all keywords built in functions and names currently defined in self namespace that match compute matches when text contains a dot assuming the text is of the form name name name and is evaluable in self namespace it will be evaluated and its attributes as revealed by dir are used as possible completions for class instances class members are also considered warning this can still invoke arbitrary c code if an object with a __getattr__ hook is evaluated get the content of the object except __builtins__ bpo 44752 thisobject word is a method decorated by property what follows applies a postfix if thisobject word is callable but know we know that this is not callable because it is a property also getattr thisobject word will evaluate the property method which is not desirable release references early at shutdown the readline module s contents are quasi immortal and the completer function holds a reference to globals
import atexit
import builtins
import inspect
import keyword
import re
import __main__

__all__ = ["Completer"]

class Completer:
    def __init__(self, namespace = None):
        

        if namespace and not isinstance(namespace, dict):
            raise TypeError('namespace must be a dictionary')

        
        
        
        if namespace is None:
            self.use_main_ns = 1
        else:
            self.use_main_ns = 0
            self.namespace = namespace

    def complete(self, text, state):
        
        if self.use_main_ns:
            self.namespace = __main__.__dict__

        if not text.strip():
            if state == 0:
                if _readline_available:
                    readline.insert_text('\t')
                    readline.redisplay()
                    return ''
                else:
                    return '\t'
            else:
                return None

        if state == 0:
            if "." in text:
                self.matches = self.attr_matches(text)
            else:
                self.matches = self.global_matches(text)
        try:
            return self.matches[state]
        except IndexError:
            return None

    def _callable_postfix(self, val, word):
        if callable(val):
            word += "("
            try:
                if not inspect.signature(val).parameters:
                    word += ")"
            except ValueError:
                pass

        return word

    def global_matches(self, text):
        
        matches = []
        seen = {"__builtins__"}
        n = len(text)
        for word in keyword.kwlist + keyword.softkwlist:
            if word[:n] == text:
                seen.add(word)
                if word in {'finally', 'try'}:
                    word = word + ':'
                elif word not in {'False', 'None', 'True',
                                  'break', 'continue', 'pass',
                                  'else', '_'}:
                    word = word + ' '
                matches.append(word)
        for nspace in [self.namespace, builtins.__dict__]:
            for word, val in nspace.items():
                if word[:n] == text and word not in seen:
                    seen.add(word)
                    matches.append(self._callable_postfix(val, word))
        return matches

    def attr_matches(self, text):
        
        m = re.match(r"(\w+(\.\w+)*)\.(\w*)", text)
        if not m:
            return []
        expr, attr = m.group(1, 3)
        try:
            thisobject = eval(expr, self.namespace)
        except Exception:
            return []

        
        words = set(dir(thisobject))
        words.discard("__builtins__")

        if hasattr(thisobject, '__class__'):
            words.add('__class__')
            words.update(get_class_members(thisobject.__class__))
        matches = []
        n = len(attr)
        if attr == '':
            noprefix = '_'
        elif attr == '_':
            noprefix = '__'
        else:
            noprefix = None
        while True:
            for word in words:
                if (word[:n] == attr and
                    not (noprefix and word[:n+1] == noprefix)):
                    match = "%s.%s" % (expr, word)
                    if isinstance(getattr(type(thisobject), word, None),
                                  property):
                        
                        
                        
                        
                        
                        
                        matches.append(match)
                        continue
                    if (value := getattr(thisobject, word, None)) is not None:
                        matches.append(self._callable_postfix(value, match))
                    else:
                        matches.append(match)
            if matches or not noprefix:
                break
            if noprefix == '_':
                noprefix = '__'
            else:
                noprefix = None
        matches.sort()
        return matches

def get_class_members(klass):
    ret = dir(klass)
    if hasattr(klass,'__bases__'):
        for base in klass.__bases__:
            ret = ret + get_class_members(base)
    return ret

try:
    import readline
except ImportError:
    _readline_available = False
else:
    readline.set_completer(Completer().complete)
    
    
    
    atexit.register(lambda: readline.set_completer(None))
    _readline_available = True