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 readline
  43 import __builtin__
  44 import __main__
  45
  46 __all__ = ["Completer"]
  47
  48 class Completer:
  49     def __init__(self, namespace = None):
  50         """Create a new completer for the command line.
  51
  52         Completer([namespace]) -> completer instance.
  53
  54         If unspecified, the default namespace where completions are performed
  55         is __main__ (technically, __main__.__dict__). Namespaces should be
  56         given as dictionaries.
  57
  58         Completer instances should be used as the completion mechanism of
  59         readline via the set_completer() call:
  60
  61         readline.set_completer(Completer(my_namespace).complete)
  62         """
  63
  64         if namespace and not isinstance(namespace, dict):
  65             raise TypeError,'namespace must be a dictionary'
  66
  67         # Don't bind to namespace quite yet, but flag whether the user wants a
  68         # specific namespace or to use __main__.__dict__. This will allow us
  69         # to bind to __main__.__dict__ at completion time, not now.
  70         if namespace is None:
  71             self.use_main_ns = 1
  72         else:
  73             self.use_main_ns = 0
  74             self.namespace = namespace
  75
  76     def complete(self, text, state):
  77         """Return the next possible completion for 'text'.
  78
  79         This is called successively with state == 0, 1, 2, ... until it
  80         returns None.  The completion should begin with 'text'.
  81
  82         """
  83         if self.use_main_ns:
  84             self.namespace = __main__.__dict__
  85
  86         if state == 0:
  87             if "." in text:
  88                 self.matches = self.attr_matches(text)
  89             else:
  90                 self.matches = self.global_matches(text)
  91         try:
  92             return self.matches[state]
  93         except IndexError:
  94             return None
  95
  96     def global_matches(self, text):
  97         """Compute matches when text is a simple name.
  98
  99         Return a list of all keywords, built-in functions and names currently
 100         defined in self.namespace that match.
 101
 102         """
 103         import keyword
 104         matches = []
 105         n = len(text)
 106         for list in [keyword.kwlist,
 107                      __builtin__.__dict__,
 108                      self.namespace]:
 109             for word in list:
 110                 if word[:n] == text and word != "__builtins__":
 111                     matches.append(word)
 112         return matches
 113
 114     def attr_matches(self, text):
 115         """Compute matches when text contains a dot.
 116
 117         Assuming the text is of the form NAME.NAME....[NAME], and is
 118         evaluatable in self.namespace, it will be evaluated and its attributes
 119         (as revealed by dir()) are used as possible completions.  (For class
 120         instances, class members are also considered.)
 121
 122         WARNING: this can still invoke arbitrary C code, if an object
 123         with a __getattr__ hook is evaluated.
 124
 125         """
 126         import re
 127         m = re.match(r"(\w+(\.\w+)*)\.(\w*)", text)
 128         if not m:
 129             return
 130         expr, attr = m.group(1, 3)
 131         object = eval(expr, self.namespace)
 132         words = dir(object)
 133         if hasattr(object,'__class__'):
 134             words.append('__class__')
 135             words = words + get_class_members(object.__class__)
 136         matches = []
 137         n = len(attr)
 138         for word in words:
 139             if word[:n] == attr and word != "__builtins__":
 140                 matches.append("%s.%s" % (expr, word))
 141         return matches
 142
 143 def get_class_members(klass):
 144     ret = dir(klass)
 145     if hasattr(klass,'__bases__'):
 146         for base in klass.__bases__:
 147             ret = ret + get_class_members(base)
 148     return ret
 149
 150 readline.set_completer(Completer().complete)