Lib/rlcompleter.py

   1 """Word completion for GNU readline 2.0.
   2
   3 This requires the latest extension to the readline module. The completer
   4 completes keywords, built-ins and globals in a selectable namespace (which
   5 defaults to __main__); when completing NAME.NAME..., it evaluates (!) the
   6 expression up to the last dot and completes its attributes.
   7
   8 It's very cool to do "import sys" type "sys.", hit the
   9 completion key (twice), and see the list of names defined by the
  10 sys module!
  11
  12 Tip: to use the tab key as the completion key, call
  13
  14     readline.parse_and_bind("tab: complete")
  15
  16 Notes:
  17
  18 - Exceptions raised by the completer function are *ignored* (and
  19 generally cause the completion to fail).  This is a feature -- since
  20 readline sets the tty device in raw (or cbreak) mode, printing a
  21 traceback wouldn't work well without some complicated hoopla to save,
  22 reset and restore the tty state.
  23
  24 - The evaluation of the NAME.NAME... form may cause arbitrary
  25 application defined code to be executed if an object with a
  26 __getattr__ hook is found.  Since it is the responsibility of the
  27 application (or the user) to enable this feature, I consider this an
  28 acceptable risk.  More complicated expressions (e.g. function calls or
  29 indexing operations) are *not* evaluated.
  30
  31 - GNU readline is also used by the built-in functions input() and
  32 raw_input(), and thus these also benefit/suffer from the completer
  33 features.  Clearly an interactive application can benefit by
  34 specifying its own completer function and using raw_input() for all
  35 its input.
  36
  37 - When the original stdin is not a tty device, GNU readline is never
  38 used, and this module (and the readline module) are silently inactive.
  39
  40 """
  41
  42 import __builtin__
  43 import __main__
  44
  45 __all__ = ["Completer"]
  46
  47 class Completer:
  48     def __init__(self, namespace = None):
  49         """Create a new completer for the command line.
  50
  51         Completer([namespace]) -> completer instance.
  52
  53         If unspecified, the default namespace where completions are performed
  54         is __main__ (technically, __main__.__dict__). Namespaces should be
  55         given as dictionaries.
  56
  57         Completer instances should be used as the completion mechanism of
  58         readline via the set_completer() call:
  59
  60         readline.set_completer(Completer(my_namespace).complete)
  61         """
  62
  63         if namespace and not isinstance(namespace, dict):
  64             raise TypeError,'namespace must be a dictionary'
  65
  66         # Don't bind to namespace quite yet, but flag whether the user wants a
  67         # specific namespace or to use __main__.__dict__. This will allow us
  68         # to bind to __main__.__dict__ at completion time, not now.
  69         if namespace is None:
  70             self.use_main_ns = 1
  71         else:
  72             self.use_main_ns = 0
  73             self.namespace = namespace
  74
  75     def complete(self, text, state):
  76         """Return the next possible completion for 'text'.
  77
  78         This is called successively with state == 0, 1, 2, ... until it
  79         returns None.  The completion should begin with 'text'.
  80
  81         """
  82         if self.use_main_ns:
  83             self.namespace = __main__.__dict__
  84
  85         if state == 0:
  86             if "." in text:
  87                 self.matches = self.attr_matches(text)
  88             else:
  89                 self.matches = self.global_matches(text)
  90         try:
  91             return self.matches[state]
  92         except IndexError:
  93             return None
  94
  95     def _callable_postfix(self, val, word):
  96         if hasattr(val, '__call__'):
  97             word = word + "("
  98         return word
  99
 100     def global_matches(self, text):
 101         """Compute matches when text is a simple name.
 102
 103         Return a list of all keywords, built-in functions and names currently
 104         defined in self.namespace that match.
 105
 106         """
 107         import keyword
 108         matches = []
 109         n = len(text)
 110         for word in keyword.kwlist:
 111             if word[:n] == text:
 112                 matches.append(word)
 113         for nspace in [__builtin__.__dict__, self.namespace]:
 114             for word, val in nspace.items():
 115                 if word[:n] == text and word != "__builtins__":
 116                     matches.append(self._callable_postfix(val, word))
 117         return matches
 118
 119     def attr_matches(self, text):
 120         """Compute matches when text contains a dot.
 121
 122         Assuming the text is of the form NAME.NAME....[NAME], and is
 123         evaluatable in self.namespace, it will be evaluated and its attributes
 124         (as revealed by dir()) are used as possible completions.  (For class
 125         instances, class members are also considered.)
 126
 127         WARNING: this can still invoke arbitrary C code, if an object
 128         with a __getattr__ hook is evaluated.
 129
 130         """
 131         import re
 132         m = re.match(r"(\w+(\.\w+)*)\.(\w*)", text)
 133         if not m:
 134             return []
 135         expr, attr = m.group(1, 3)
 136         try:
 137             thisobject = eval(expr, self.namespace)
 138         except Exception:
 139             return []
 140
 141         # get the content of the object, except __builtins__
 142         words = dir(thisobject)
 143         if "__builtins__" in words:
 144             words.remove("__builtins__")
 145
 146         if hasattr(thisobject, '__class__'):
 147             words.append('__class__')
 148             words.extend(get_class_members(thisobject.__class__))
 149         matches = []
 150         n = len(attr)
 151         for word in words:
 152             if word[:n] == attr and hasattr(thisobject, word):
 153                 val = getattr(thisobject, word)
 154                 word = self._callable_postfix(val, "%s.%s" % (expr, word))
 155                 matches.append(word)
 156         return matches
 157
 158 def get_class_members(klass):
 159     ret = dir(klass)
 160     if hasattr(klass,'__bases__'):
 161         for base in klass.__bases__:
 162             ret = ret + get_class_members(base)
 163     return ret
 164
 165 try:
 166     import readline
 167 except ImportError:
 168     pass
 169 else:
 170     readline.set_completer(Completer().complete)