# 16.9. `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.

Example:

    >>> 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:

    try:
        import readline
    except ImportError:
        print "Module readline not available."
    else:
        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.

## 16.9.1. 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__`, `__builtin__` 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.