"rlcompleter" --- GNU readline 的補全函式
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**原始碼：**Lib/rlcompleter.py

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The "rlcompleter" module defines a completion function suitable to be
passed to "set_completer()" in the "readline" module.

When this module is imported on a Unix platform with the "readline"
module available, an instance of the "Completer" class is
automatically created and its "complete()" method is set as the
readline completer. The method provides completion of valid Python
identifiers and keywords.

範例：

   >>> import rlcompleter
   >>> import readline
   >>> readline.parse_and_bind("tab: complete")
   >>> readline. <TAB PRESSED>
   readline.__doc__          readline.get_line_buffer(  readline.read_init_file(
   readline.__file__         readline.insert_text(      readline.set_completer(
   readline.__name__         readline.parse_and_bind(
   >>> readline.

The "rlcompleter" module is designed for use with Python's interactive
mode.  Unless Python is run with the "-S" option, the module is
automatically imported and configured (see Readline configuration).

On platforms without "readline", the "Completer" class defined by this
module can still be used for custom purposes.

class rlcompleter.Completer

   Completer objects have the following method:

   complete(text, state)

      Return the next possible completion for *text*.

      When called by the "readline" module, this method is called
      successively with "state == 0, 1, 2, ..." until the method
      returns "None".

      If called for *text* that doesn't include a period character
      ("'.'"), it will complete from names currently defined in
      "__main__", "builtins" and keywords (as defined by the "keyword"
      module).

      If called for a dotted name, it will try to evaluate anything
      without obvious side-effects (functions will not be evaluated,
      but it can generate calls to "__getattr__()") up to the last
      part, and find matches for the rest via the "dir()" function.
      Any exception raised during the evaluation of the expression is
      caught, silenced and "None" is returned.
