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 global_matches(self, text):
  96         """Compute matches when text is a simple name.
  97
  98         Return a list of all keywords, built-in functions and names currently
  99         defined in self.namespace that match.
 100
 101         """
 102         import keyword
 103         matches = []
 104         n = len(text)
 105         for list in [keyword.kwlist,
 106                      __builtin__.__dict__,
 107                      self.namespace]:
 108             for word in list:
 109                 if word[:n] == text and word != "__builtins__":
 110                     matches.append(word)
 111         return matches
 112
 113     def attr_matches(self, text):
 114         """Compute matches when text contains a dot.
 115
 116         Assuming the text is of the form NAME.NAME....[NAME], and is
 117         evaluatable in self.namespace, it will be evaluated and its attributes
 118         (as revealed by dir()) are used as possible completions.  (For class
 119         instances, class members are also considered.)
 120
 121         WARNING: this can still invoke arbitrary C code, if an object
 122         with a __getattr__ hook is evaluated.
 123
 124         """
 125         import re
 126         m = re.match(r"(\w+(\.\w+)*)\.(\w*)", text)
 127         if not m:
 128             return []
 129         expr, attr = m.group(1, 3)
 130         try:
 131             object = eval(expr, self.namespace)
 132         except Exception:
 133             return []
 134         words = dir(object)
 135         if hasattr(object,'__class__'):
 136             words.append('__class__')
 137             words = words + get_class_members(object.__class__)
 138         matches = []
 139         n = len(attr)
 140         for word in words:
 141             if word[:n] == attr and word != "__builtins__":
 142                 matches.append("%s.%s" % (expr, word))
 143         return matches
 144
 145 def get_class_members(klass):
 146     ret = dir(klass)
 147     if hasattr(klass,'__bases__'):
 148         for base in klass.__bases__:
 149             ret = ret + get_class_members(base)
 150     return ret
 151
 152 try:
 153     import readline
 154 except ImportError:
 155     pass
 156 else:
 157     readline.set_completer(Completer().complete)