negargparse 0.2.0

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negargparse

An ArgumentParser which understands negative numbers.

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Getting negargparse

The preferred way to use negargparse is to copy the module negargparse.py into your project. This is because currently one can expect frequent API changes. We do use semantic versioning to help you guard against it.

negargparse can also be installed from PyPI:

pip install negargparse

Usage

The argparse module in python provides tools to parse command line arguments. However, sometimes it doesn't interpret arguments correctly when dealing with negative numbers. Currently argparse correctly interprets negative numbers if they are strictly numbers and there are no numeral options like -1. However it doesn't work when working with non standard numeral formats. e.g. declination is usually written in the (+|-)(degree):(arcminute):(arcsecond) format like -16:32:45.46. argparse would interpret this as an option, rather than an argument and quit (because of finding an unknown argument) before we have a chance to examine it. Any way to solve this issue requires doing some hacky gymnastics, negargparse is here to do that for you.

negargparse provides a subclass of ArgumentParser called NegativeArgumentParser, which escapes all arguments which begin with a '-' followed by a digit. Now declare the type of arguments that you expect to be negative as one of the provided types NegString, NegInt, NegFloat to unescape them.

>>> parser = negargparse.NegativeArgumentParser()
>>> parser.add_argument("eggs", type=NegString)
>>> parser.parse_args(["-23h15m04s"])
Namespace(eggs='-23h15m04s')

License

This repository is distributed under the MIT License, though the module is available under the more permissive MIT-0 license. See the LICENSE or at the top of the module for the license text.

Known issues

Right now this project is more or less a framework to develop the module. Except for some narrow cases, it breaks more pre-existing functionality of argparse than provide new ones. Right now you are better off not using this if that bothers you.

• If the user types a negative number in an unexpected (not of the provided NegString etc. types) argument, this would escape the said field, but since it is not declared as a NegString/NegInt/NegFloat, it wouldn't be unescaped.

• This module doesn't respect the POSIX convention of leaving the arguments after --.

• Currently single digit options are unusable.

• This project currently lacks support for versions earlier than python 3.7. This is not because of lack of any features in python 3.6, but because of lack of support for annotations used in this module. At the release of v1, a special untyped release for python 3.6 shall be made.

Development

This section tells you how to set up the development environment and run tests, which can be used to either modify the module for their own purpose of for potential contributors.

Setup development environment

Ensure python >= 3.8

Ensure you have poetry installed. You can get it from https://github.com/python-poetry/poetry. This requires poetry >=1.2 which is currently only released as alpha.

1. Clone the repository
2. Install the package

poetry install --with dev

3. Install pre-commit hooks

poetry run pre-commit install

Now whenever developing, enter virtual environment using

poetry shell

From now on this document assumes that you are within a virtual environment. Otherwise prepend you commands with poetry run.

Testing

Tests are written in the pytest framework, to run them use:

pytest

To run extensive tests within isolated environments use tox:

tox

Links

• Change log
• Contributing