argcomplete - Bash completion for argparse

Argcomplete provides easy and extensible automatic tab completion of arguments and options for your Python script.

It makes two assumptions:

• You're using bash as your shell
• You're using argparse to manage your command line options

Argcomplete is particularly useful if your program has lots of options or subparsers, and if you can suggest completions for your argument/option values (for example, if the user is browsing resources over the network).

Installation

pip install argcomplete

Synopsis

Python code (e.g. my-awesome-script.py):

import argcomplete, argparse
parser = argparse.ArgumentParser()
...
argcomplete.autocomplete(parser)
parser.parse()
...

Shellcode (to be put in e.g. .bashrc):

eval "$(register-python-argcomplete my-awesome-script.py)"

argcomplete.autocomplete(parser)

This method is the entry point to the module. It must be called after ArgumentParser construction is complete, but before the ArgumentParser.parse() method is called. The method looks for an environment variable that the completion hook shellcode sets, and if it's there, collects completions, prints them to standard output, and exits. Otherwise, it returns to the caller immediately.

Specifying completers

You can specify custom completion functions for your options and arguments. Completers are called with the following keyword arguments:

• prefix: The prefix text of the last word before the cursor on the command line. All returned completions should begin with this prefix.
• action: The argparse.Action instance that this completer was called for.
• parser: The argparse.ArgumentParser instance that the action was taken by.

Completers should return their completions as a list of strings. An example completer for names of environment variables might look like this:

def EnvironCompleter(prefix, **kwargs):
    return (v for v in os.environ if v.startswith(prefix))

If you specify the choices keyword for an argparse option or argument (and don't specify a completer), it will be used for completions.

A completer that is initialized with a set of all possible choices of values for its action might look like this:

class ChoicesCompleter(object):
    def __init__(self, choices=[]):
        self.choices = choices

    def __call__(self, prefix, **kwargs):
    return (c for c in self.choices if c.startswith(prefix))

To specify a completer for an argument or option, set the completer attribute of its associated action. An easy way to do this at definition time is:

from argcomplete.completers import EnvironCompleter

parser = argparse.ArgumentParser()
parser.add_argument("--env-var1").completer = EnvironCompleter
parser.add_argument("--env-var2").completer = EnvironCompleter
argcomplete.autocomplete(parser)

The following two ways to specify a static set of choices are equivalent for completion purposes:

from argcomplete.completers import ChoicesCompleter

parser.add_argument("--protocol", choices=('http', 'https', 'ssh', 'rsync', 'wss'))
parser.add_argument("--proto").completer=ChoicesCompleter(('http', 'https', 'ssh', 'rsync', 'wss'))

Acknowledgments

Inspired and informed by the optcomplete module by Martin Blais.

Links

• Home page
• Docs
• On pypi