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https://github.com/kislyuk/argcomplete

Python and tab completion, better together.
https://github.com/kislyuk/argcomplete

argparse bash bash-completion python tab-completion zsh zsh-completion

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Python and tab completion, better together.

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argcomplete - Bash/zsh tab completion for argparse

==================================================

*Tab complete all the things!*



Argcomplete provides easy, extensible command line tab completion of arguments for your Python application.



It makes two assumptions:



* You're using bash or zsh as your shell

* You're using `argparse `_ to manage your command line arguments/options



Argcomplete is particularly useful if your program has lots of options or subparsers, and if your program can

dynamically suggest completions for your argument/option values (for example, if the user is browsing resources over

the network).



Installation

------------

::



    pip install argcomplete

    activate-global-python-argcomplete



See `Activating global completion`_ below for details about the second step.



Refresh your shell environment (start a new shell).



Synopsis

--------

Add the ``PYTHON_ARGCOMPLETE_OK`` marker and a call to ``argcomplete.autocomplete()`` to your Python application as

follows:



.. code-block:: python



    #!/usr/bin/env python

    # PYTHON_ARGCOMPLETE_OK

    import argcomplete, argparse

    parser = argparse.ArgumentParser()

    ...

    argcomplete.autocomplete(parser)

    args = parser.parse_args()

    ...



Register your Python application with your shell's completion framework by running ``register-python-argcomplete``::



    eval "$(register-python-argcomplete my-python-app)"



Quotes are significant; the registration will fail without them. See `Global completion`_ below for a way to enable

argcomplete generally without registering each application individually.



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_args()`` 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 the output stream (fd 8 by

default), and exits. Otherwise, it returns to the caller immediately.



.. admonition:: Side effects



 Argcomplete gets completions by running your program. It intercepts the execution flow at the moment

 ``argcomplete.autocomplete()`` is called. After sending completions, it exits using ``exit_method`` (``os._exit``

 by default). This means if your program has any side effects that happen before ``argcomplete`` is called, those

 side effects will happen every time the user presses ```` (although anything your program prints to stdout or

 stderr will be suppressed). For this reason it's best to construct the argument parser and call

 ``argcomplete.autocomplete()`` as early as possible in your execution flow.



.. admonition:: Performance



 If the program takes a long time to get to the point where ``argcomplete.autocomplete()`` is called, the tab completion

 process will feel sluggish, and the user may lose confidence in it. So it's also important to minimize the startup time

 of the program up to that point (for example, by deferring initialization or importing of large modules until after

 parsing options).



Specifying completers

---------------------

You can specify custom completion functions for your options and arguments. Two styles are supported: callable and

readline-style. Callable completers are simpler. They are called with the following keyword arguments:



* ``prefix``: The prefix text of the last word before the cursor on the command line.

  For dynamic completers, this can be used to reduce the work required to generate possible completions.

* ``action``: The ``argparse.Action`` instance that this completer was called for.

* ``parser``: The ``argparse.ArgumentParser`` instance that the action was taken by.

* ``parsed_args``: The result of argument parsing so far (the ``argparse.Namespace`` args object normally returned by

  ``ArgumentParser.parse_args()``).



Completers can return their completions as an iterable of strings or a mapping (dict) of strings to their

descriptions (zsh will display the descriptions as context help alongside completions). An example completer for names

of environment variables might look like this:



.. code-block:: python



    def EnvironCompleter(**kwargs):

        return os.environ



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:



.. code-block:: python



    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)



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:



.. code-block:: python



    class ChoicesCompleter(object):

        def __init__(self, choices):

            self.choices = choices



        def __call__(self, **kwargs):

            return self.choices



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



.. code-block:: python



    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'))



Note that if you use the ``choices=`` option, argparse will show

all these choices in the ``--help`` output by default. To prevent this, set

``metavar`` (like ``parser.add_argument("--protocol", metavar="PROTOCOL",

choices=('http', 'https', 'ssh', 'rsync', 'wss'))``).



The following `script `_ uses

``parsed_args`` and `Requests `_ to query GitHub for publicly known members of an

organization and complete their names, then prints the member description:



.. code-block:: python



    #!/usr/bin/env python

    # PYTHON_ARGCOMPLETE_OK

    import argcomplete, argparse, requests, pprint



    def github_org_members(prefix, parsed_args, **kwargs):

        resource = "https://api.github.com/orgs/{org}/members".format(org=parsed_args.organization)

        return (member['login'] for member in requests.get(resource).json() if member['login'].startswith(prefix))



    parser = argparse.ArgumentParser()

    parser.add_argument("--organization", help="GitHub organization")

    parser.add_argument("--member", help="GitHub member").completer = github_org_members



    argcomplete.autocomplete(parser)

    args = parser.parse_args()



    pprint.pprint(requests.get("https://api.github.com/users/{m}".format(m=args.member)).json())



`Try it `_ like this::



    ./describe_github_user.py --organization heroku --member 



If you have a useful completer to add to the `completer library

`_, send a pull request!



Readline-style completers

~~~~~~~~~~~~~~~~~~~~~~~~~

The readline_ module defines a completer protocol in rlcompleter_. Readline-style completers are also supported by

argcomplete, so you can use the same completer object both in an interactive readline-powered shell and on the command

line. For example, you can use the readline-style completer provided by IPython_ to get introspective completions like

you would get in the IPython shell:



.. _readline: http://docs.python.org/3/library/readline.html

.. _rlcompleter: http://docs.python.org/3/library/rlcompleter.html#completer-objects

.. _IPython: http://ipython.org/



.. code-block:: python



    import IPython

    parser.add_argument("--python-name").completer = IPython.core.completer.Completer()



``argcomplete.CompletionFinder.rl_complete`` can also be used to plug in an argparse parser as a readline completer.



Printing warnings in completers

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Normal stdout/stderr output is suspended when argcomplete runs. Sometimes, though, when the user presses ````, it's

appropriate to print information about why completions generation failed. To do this, use ``warn``:



.. code-block:: python



    from argcomplete import warn



    def AwesomeWebServiceCompleter(prefix, **kwargs):

        if login_failed:

            warn("Please log in to Awesome Web Service to use autocompletion")

        return completions



Using a custom completion validator

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

By default, argcomplete validates your completions by checking if they start with the prefix given to the completer. You

can override this validation check by supplying the ``validator`` keyword to ``argcomplete.autocomplete()``:



.. code-block:: python



    def my_validator(completion_candidate, current_input):

        """Complete non-prefix substring matches."""

        return current_input in completion_candidate



    argcomplete.autocomplete(parser, validator=my_validator)



Global completion

-----------------

In global completion mode, you don't have to register each argcomplete-capable executable separately. Instead, the shell

will look for the string **PYTHON_ARGCOMPLETE_OK** in the first 1024 bytes of any executable that it's running

completion for, and if it's found, follow the rest of the argcomplete protocol as described above.



Additionally, completion is activated for scripts run as ``python `` and ``python -m <module>``. If you're using

multiple Python versions on the same system, the version being used to run the script must have argcomplete installed.



.. admonition:: Bash version compatibility



 When using bash, global completion requires bash support for ``complete -D``, which was introduced in bash 4.2. Since

 Mac OS ships with an outdated version of Bash (3.2), you can either use zsh or install a newer version of bash using

 `Homebrew <http://brew.sh/>`_ (``brew install bash`` - you will also need to add ``/opt/homebrew/bin/bash`` to

 ``/etc/shells``, and run ``chsh`` to change your shell). You can check the version of the running copy of bash with

 ``echo $BASH_VERSION``.



.. note:: If you use setuptools/distribute ``scripts`` or ``entry_points`` directives to package your module,

 argcomplete will follow the wrapper scripts to their destination and look for ``PYTHON_ARGCOMPLETE_OK`` in the

 destination code.



If you choose not to use global completion, or ship a completion module that depends on argcomplete, you must register

your script explicitly using ``eval "$(register-python-argcomplete my-python-app)"``. Standard completion module

registration rules apply: namely, the script name is passed directly to ``complete``, meaning it is only tab completed

when invoked exactly as it was registered. In the above example, ``my-python-app`` must be on the path, and the user

must be attempting to complete it by that name. The above line alone would **not** allow you to complete

``./my-python-app``, or ``/path/to/my-python-app``.



Activating global completion

~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The script ``activate-global-python-argcomplete`` installs the global completion script

`bash_completion.d/_python-argcomplete <https://github.com/kislyuk/argcomplete/blob/master/argcomplete/bash_completion.d/_python-argcomplete>`_

into an appropriate location on your system for both bash and zsh. The specific location depends on your platform and

whether you installed argcomplete system-wide using ``sudo`` or locally (into your user's home directory).



Zsh Support

-----------

Argcomplete supports zsh. On top of plain completions like in bash, zsh allows you to see argparse help strings as

completion descriptions. All shellcode included with argcomplete is compatible with both bash and zsh, so the same

completer commands ``activate-global-python-argcomplete`` and ``eval "$(register-python-argcomplete my-python-app)"``

work for zsh as well.



Python Support

--------------

Argcomplete requires Python 3.7+.



Support for other shells

------------------------

Argcomplete maintainers provide support only for the bash and zsh shells on Linux and MacOS. For resources related to

other shells and platforms, including fish, tcsh, xonsh, powershell, and Windows, please see the

`contrib <https://github.com/kislyuk/argcomplete/tree/develop/contrib>`_ directory.



Common Problems

---------------

If global completion is not completing your script, bash may have registered a default completion function::



    $ complete | grep my-python-app

    complete -F _minimal my-python-app



You can fix this by restarting your shell, or by running ``complete -r my-python-app``.



Debugging

---------

Set the ``_ARC_DEBUG`` variable in your shell to enable verbose debug output every time argcomplete runs. This will

disrupt the command line composition state of your terminal, but make it possible to see the internal state of the

completer if it encounters problems.



Acknowledgments

---------------

Inspired and informed by the optcomplete_ module by Martin Blais.



.. _optcomplete: http://pypi.python.org/pypi/optcomplete



Links

-----

* `Project home page (GitHub) <https://github.com/kislyuk/argcomplete>`_

* `Documentation <https://kislyuk.github.io/argcomplete/>`_

* `Package distribution (PyPI) <https://pypi.python.org/pypi/argcomplete>`_

* `Change log <https://github.com/kislyuk/argcomplete/blob/master/Changes.rst>`_



Bugs

~~~~

Please report bugs, issues, feature requests, etc. on `GitHub <https://github.com/kislyuk/argcomplete/issues>`_.



License

-------

Copyright 2012-2023, Andrey Kislyuk and argcomplete contributors. Licensed under the terms of the

`Apache License, Version 2.0 <http://www.apache.org/licenses/LICENSE-2.0>`_. Distribution of the LICENSE and NOTICE

files with source copies of this package and derivative works is **REQUIRED** as specified by the Apache License.



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