arghelper

arghelper is a Python 3.12+ module providing functions to help with argparse.

Installation

You can install arghelper either via the Python Package Index (PyPI) or from source.

To add it to a project managed with uv, which records it in your pyproject.toml and lock file:

$ uv add arghelper

Or to install it with pip:

$ pip install arghelper

Source: https://github.com/questrail/arghelper

Requirements

• argparse module from the Python Standard Library
• os module from the Python Standard Library

Usage

arghelper provides functions to determine if a file or directory exists:

• extant_file
• extant_dir

These can be used as follows:

if __name__ == "__main__":
    # Process the arguments
    import argparse
    import arghelper

    parser = argparse.ArgumentParser(description="Process the TAFFmat CET files")
    parser.add_argument(
        "config_file",
        help="CSV configuration file.",
        metavar="FILE",
        type=arghelper.extant_file,
    )
    parser.add_argument(
        "input_dir",
        help="Directory containing input files.",
        metavar="DIR",
        type=arghelper.extant_dir,
    )
    args = parser.parse_args()

A common pattern, for me at least, is to have three positional arguments consisting of:

1. config_file --- A configuration file
2. input_dir --- A directory containing input files to be read
3. output_dir --- A directory where the output files should be saved

This pattern has been abstracted to a Facade function called parse_config_input_output, which can be used as follows:

if __name__ == "__main__":
    # Process the arguments
    import sys

    import arghelper

    args = arghelper.parse_config_input_output(sys.argv)

Another common pattern is to just parse the name of a config file:

if __name__ == "__main__":
    # Process the arguments
    import sys

    import arghelper

    args = arghelper.parse_config(sys.argv)

Contributing

Contributions are welcome! To contribute please:

1. Fork the repository
2. Create a feature branch
3. Add code and tests
4. Pass lint and tests
5. Submit a pull request

Development Setup

arghelper uses uv to manage the virtualenv and dependencies, and just as the task runner.

$ brew install uv just

uv sync creates the virtualenv and installs the dependencies, including the development group, and just on its own lists the available recipes.

$ uv sync
$ just

The most common recipes are:

$ just test    # Run the tests using pytest
$ just lint    # Check lint, formatting, types, and workflows
$ just fix     # Lint and format the code using ruff, applying fixes
$ just cov     # Run the tests and report coverage
$ just add X   # Add X as a dependency
$ just out     # List the outdated dependencies

ruff and pyright are deliberately absent from that brew install line. Both are dev dependencies pinned in uv.lock and reached through uv run, so every recipe and every CI job uses the same version. A brew install ruff would put a second, unpinned copy on the path for an editor to find, and ruff releases change how code is formatted: the editor would then reformat code that ruff format --check rejects on the next run.

The suite runs on 3.12, 3.13, and 3.14 in CI, which is what requires-python and the classifiers claim.

Releasing to PyPI

just release cuts the release. It first checks that a release is possible at all, then lints, type checks, and tests, then shows the entries waiting under Unreleased and the version each kind of bump would produce, and asks which to cut. Once answered it bumps the version, closes out the CHANGELOG, updates the lock file, commits, and tags. Pushing the tag is what publishes.

$ just release
...
Which release? [1] 1

Tagged v0.6.1. Publish it with:

    git push --follow-tags

Do not tag by hand. The tag push runs the release workflow, which waits on the whole CI workflow before it does anything else. It then checks that the tagged commit is on master, since a tag is only a pointer and one placed anywhere else would otherwise publish whatever it points at, rechecks the tag against the version in pyproject.toml, and builds.

Every check to that point runs against the source tree, so the workflow then installs the wheel it just built somewhere src/ is not on the path and exercises it there, which is the only step that can catch a packaging mistake. It uploads once that passes. There is no PyPI API token anywhere: the workflow authenticates with trusted publishing, which mints a short lived credential from the GitHub OIDC identity of that run, and that same identity signs a PEP 740 attestation for each distribution.

Uploading is followed by a GitHub release for the tag, carrying the CHANGELOG section for that version as its notes.

Pushing the tag is the point of no return, since PyPI never lets a version number be reused. Everything just release does is local and amendable until then, and it refuses to start against a dirty working tree, off master, on a master behind its upstream, with a CHANGELOG whose Unreleased section is empty, or when the tag it would create already exists. just release-check runs those refusals on their own.

just build runs the same checks and produces the same distributions without releasing anything.

This depends on one piece of configuration that lives outside the repository. A trusted publisher has to be registered for arghelper on PyPI, pointing at the questrail/arghelper repository, the release.yml workflow, and the pypi environment. It is a one time setup per project.

License

arghelper is released under the MIT license. Please see the LICENSE.txt file for more information.