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 - When the original stdin is not a tty device, GNU readline is never
  32 used, and this module (and the readline module) are silently inactive.
  33
  34 """
  35
  36 import builtins
  37 import __main__
  38
  39 __all__ = ["Completer"]
  40
  41 class Completer:
  42     def __init__(self, namespace = None):
  43         """Create a new completer for the command line.
  44
  45         Completer([namespace]) -> completer instance.
  46
  47         If unspecified, the default namespace where completions are performed
  48         is __main__ (technically, __main__.__dict__). Namespaces should be
  49         given as dictionaries.
  50
  51         Completer instances should be used as the completion mechanism of
  52         readline via the set_completer() call:
  53
  54         readline.set_completer(Completer(my_namespace).complete)
  55         """
  56
  57         if namespace and not isinstance(namespace, dict):
  58             raise TypeError('namespace must be a dictionary')
  59
  60         # Don't bind to namespace quite yet, but flag whether the user wants a
  61         # specific namespace or to use __main__.__dict__. This will allow us
  62         # to bind to __main__.__dict__ at completion time, not now.
  63         if namespace is None:
  64             self.use_main_ns = 1
  65         else:
  66             self.use_main_ns = 0
  67             self.namespace = namespace
  68
  69     def complete(self, text, state):
  70         """Return the next possible completion for 'text'.
  71
  72         This is called successively with state == 0, 1, 2, ... until it
  73         returns None.  The completion should begin with 'text'.
  74
  75         """
  76         if self.use_main_ns:
  77             self.namespace = __main__.__dict__
  78
  79         if state == 0:
  80             if "." in text:
  81                 self.matches = self.attr_matches(text)
  82             else:
  83                 self.matches = self.global_matches(text)
  84         try:
  85             return self.matches[state]
  86         except IndexError:
  87             return None
  88
  89     def global_matches(self, text):
  90         """Compute matches when text is a simple name.
  91
  92         Return a list of all keywords, built-in functions and names currently
  93         defined in self.namespace that match.
  94
  95         """
  96         import keyword
  97         matches = []
  98         n = len(text)
  99         for list in [keyword.kwlist,
 100                      builtins.__dict__,
 101                      self.namespace]:
 102             for word in list:
 103                 if word[:n] == text and word != "__builtins__":
 104                     matches.append(word)
 105         return matches
 106
 107     def attr_matches(self, text):
 108         """Compute matches when text contains a dot.
 109
 110         Assuming the text is of the form NAME.NAME....[NAME], and is
 111         evaluatable in self.namespace, it will be evaluated and its attributes
 112         (as revealed by dir()) are used as possible completions.  (For class
 113         instances, class members are also considered.)
 114
 115         WARNING: this can still invoke arbitrary C code, if an object
 116         with a __getattr__ hook is evaluated.
 117
 118         """
 119         import re
 120         m = re.match(r"(\w+(\.\w+)*)\.(\w*)", text)
 121         if not m:
 122             return []
 123         expr, attr = m.group(1, 3)
 124         object = eval(expr, self.namespace)
 125         words = dir(object)
 126         if hasattr(object,'__class__'):
 127             words.append('__class__')
 128             words = words + get_class_members(object.__class__)
 129         matches = []
 130         n = len(attr)
 131         for word in words:
 132             if word[:n] == attr and word != "__builtins__":
 133                 matches.append("%s.%s" % (expr, word))
 134         return matches
 135
 136 def get_class_members(klass):
 137     ret = dir(klass)
 138     if hasattr(klass,'__bases__'):
 139         for base in klass.__bases__:
 140             ret = ret + get_class_members(base)
 141     return ret
 142
 143 try:
 144     import readline
 145 except ImportError:
 146     pass
 147 else:
 148     readline.set_completer(Completer().complete)