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         object = eval(expr, self.namespace)

   131         words = dir(object)

   132         if hasattr(object,'__class__'):

   133             words.append('__class__')

   134             words = words + get_class_members(object.__class__)

   135         matches = []

   136         n = len(attr)

   137         for word in words:

   138             if word[:n] == attr and word != "__builtins__":

   139                 matches.append("%s.%s" % (expr, word))

   140         return matches

   141 

   142 def get_class_members(klass):

   143     ret = dir(klass)

   144     if hasattr(klass,'__bases__'):

   145         for base in klass.__bases__:

   146             ret = ret + get_class_members(base)

   147     return ret

   148 

   149 try:

   150     import readline

   151 except ImportError:

   152     pass

   153 else:

   154     readline.set_completer(Completer().complete)