# optcomplete: Shell Completion Self-Generator for Python

## Description

This Python module aims at providing almost automatically shell completion for any Python program that already uses the optparse module.

### Motivation

This module aims at placing the shell completion routine and the option parsing code in a single location: in the program itself.

The logic is that since a program already knows about its options, and in Python we have a standard module to specify them programmatically since Python-2.3 (optparse), the program itself is in the best position to suggest completions for an incomplete command-line to a shell that invokes it.

Traditionally, this has been done by writing shell-specific descriptions separate from the programs themselves, such as the Bash Programmable Completion project. This approach requires maintaining the shell completion functions up-to-date with the programs.

During development of this proof-of-concept, we were interested in finding if the programs could not describe their completion routines themselves, using the well-specified completion protocol in bash. Similar completion routines could be easily written for other shells and we could extend this module to them.

This code comes with support for automatic completions for Bash and Zsh.

## Documentation

optcomplete consists of a simple module optcomplete.py which you should install somewhere in your PYTHONPATH.

To add simple support to a program which already uses optparse, simply add the following code after the optparse declarations, before calling the parse_args() function on your options parser:

import optcomplete
optcomplete.autocomplete(parser)


Optionally, you can pass a completer as a second argument (see module code).

You also need to source a Bash function and then to tell Bash to trigger optcomplete completion for the specific programs that use it:

complete -F _optcomplete <program>


More examples: