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)