"""Word completion for GNU readline.

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The completer completes keywords, built-ins and globals in a selectable

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namespace (which defaults to __main__); when completing NAME.NAME..., it

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evaluates (!) the expression up to the last dot and completes its attributes.

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It's very cool to do "import sys" type "sys.", hit the completion key (twice),

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and see the list of names defined by the sys module!

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Tip: to use the tab key as the completion key, call

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readline.parse_and_bind("tab: complete")

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Notes:

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- Exceptions raised by the completer function are *ignored* (and generally cause

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the completion to fail). This is a feature -- since readline sets the tty

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device in raw (or cbreak) mode, printing a traceback wouldn't work well

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without some complicated hoopla to save, reset and restore the tty state.

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- The evaluation of the NAME.NAME... form may cause arbitrary application

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defined code to be executed if an object with a __getattr__ hook is found.

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Since it is the responsibility of the application (or the user) to enable this

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feature, I consider this an acceptable risk. More complicated expressions

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(e.g. function calls or indexing operations) are *not* evaluated.

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- When the original stdin is not a tty device, GNU readline is never

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used, and this module (and the readline module) are silently inactive.

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"""

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import atexit

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import builtins

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import __main__

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__all__ = ["Completer"]

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class Completer:

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def __init__(self, namespace = None):

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"""Create a new completer for the command line.

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Completer([namespace]) -> completer instance.

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If unspecified, the default namespace where completions are performed

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is __main__ (technically, __main__.__dict__). Namespaces should be

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given as dictionaries.

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Completer instances should be used as the completion mechanism of

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readline via the set_completer() call:

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readline.set_completer(Completer(my_namespace).complete)

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"""

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if namespace and not isinstance(namespace, dict):

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raise TypeError('namespace must be a dictionary')

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# Don't bind to namespace quite yet, but flag whether the user wants a

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# specific namespace or to use __main__.__dict__. This will allow us

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# to bind to __main__.__dict__ at completion time, not now.

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if namespace is None:

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self.use_main_ns = 1

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else:

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self.use_main_ns = 0

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self.namespace = namespace

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def complete(self, text, state):

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"""Return the next possible completion for 'text'.

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This is called successively with state == 0, 1, 2, ... until it

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returns None. The completion should begin with 'text'.

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"""

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if self.use_main_ns:

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self.namespace = __main__.__dict__

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if not text.strip():

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if state == 0:

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if _readline_available:

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readline.insert_text('\t')

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readline.redisplay()

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return ''

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else:

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return '\t'

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else:

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return None

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if state == 0:

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if "." in text:

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self.matches = self.attr_matches(text)

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else:

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self.matches = self.global_matches(text)

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try:

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return self.matches[state]

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except IndexError:

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return None

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def _callable_postfix(self, val, word):

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if callable(val):

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word = word + "("

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return word

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def global_matches(self, text):

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"""Compute matches when text is a simple name.

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Return a list of all keywords, built-in functions and names currently

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defined in self.namespace that match.

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"""

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import keyword

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matches = []

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seen = {"__builtins__"}

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n = len(text)

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for word in keyword.kwlist:

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if word[:n] == text:

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seen.add(word)

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if word in {'finally', 'try'}:

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word = word + ':'

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elif word not in {'False', 'None', 'True',

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'break', 'continue', 'pass',

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'else'}:

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word = word + ' '

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matches.append(word)

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for nspace in [self.namespace, builtins.__dict__]:

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for word, val in nspace.items():

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if word[:n] == text and word not in seen:

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seen.add(word)

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matches.append(self._callable_postfix(val, word))

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return matches

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def attr_matches(self, text):

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"""Compute matches when text contains a dot.

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Assuming the text is of the form NAME.NAME....[NAME], and is

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evaluable in self.namespace, it will be evaluated and its attributes

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(as revealed by dir()) are used as possible completions. (For class

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instances, class members are also considered.)

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WARNING: this can still invoke arbitrary C code, if an object

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with a __getattr__ hook is evaluated.

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"""

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import re

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m = re.match(r"(\w+(\.\w+)*)\.(\w*)", text)

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if not m:

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return []

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expr, attr = m.group(1, 3)

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try:

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thisobject = eval(expr, self.namespace)

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except Exception:

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return []

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# get the content of the object, except __builtins__

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words = set(dir(thisobject))

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words.discard("__builtins__")

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if hasattr(thisobject, '__class__'):

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words.add('__class__')

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words.update(get_class_members(thisobject.__class__))

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matches = []

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n = len(attr)

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if attr == '':

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noprefix = '_'

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elif attr == '_':

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noprefix = '__'

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else:

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noprefix = None

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while True:

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for word in words:

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if (word[:n] == attr and

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not (noprefix and word[:n+1] == noprefix)):

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match = "%s.%s" % (expr, word)

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try:

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val = getattr(thisobject, word)

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except Exception:

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pass # Include even if attribute not set

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else:

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match = self._callable_postfix(val, match)

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matches.append(match)

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if matches or not noprefix:

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break

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if noprefix == '_':

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noprefix = '__'

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else:

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noprefix = None

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matches.sort()

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return matches

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def get_class_members(klass):

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ret = dir(klass)

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if hasattr(klass,'__bases__'):

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for base in klass.__bases__:

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ret = ret + get_class_members(base)

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return ret

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try:

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import readline

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except ImportError:

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_readline_available = False

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else:

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readline.set_completer(Completer().complete)

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# Release references early at shutdown (the readline module's

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# contents are quasi-immortal, and the completer function holds a

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# reference to globals).

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atexit.register(lambda: readline.set_completer(None))

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_readline_available = True

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