16.7. rlcompleter — Completion function for GNU readline

Source code: Lib/rlcompleter.py

The rlcompleter module defines a completion function suitable for the readline module by completing valid Python identifiers and keywords.

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.


>>> 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. A user can add the following lines to his or her initialization file (identified by the PYTHONSTARTUP environment variable) to get automatic Tab completion:

    import readline
except ImportError:
    print("Module readline not available.")
    import rlcompleter
    readline.parse_and_bind("tab: complete")

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

16.7.1. Completer Objects

Completer objects have the following method:

Completer.complete(text, state)

Return the stateth completion for text.

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.