Contributions are welcome, and they are greatly appreciated! Every little bit helps, and credit will always be given.

Code of Conduct

The development of unyt happens in the context of the yt community code of conduct. If for any reason you feel that the code of conduct has been violated in the context of unyt development, please send an e-mail to with details describing the incident. All emails sent to this address will be treated with the strictest confidence by an individual who does not normally participate in yt development.

Types of Contributions

You can contribute in many ways:

Report Bugs

Report bugs at

If you are reporting a bug, please include:

  • Your operating system name and version.

  • Any details about your local setup that might be helpful in troubleshooting. This includes things like Python version and versions of any libraries being used, including unyt.

  • If possible, detailed steps to reproduce the bug.

Fix Bugs

Look through the GitHub issues for bugs. Anything tagged with “bug” and “help wanted” is open to whoever wants to implement it.

Implement Features

Look through the GitHub issues for features. Anything tagged with “enhancement” and “help wanted” is open to whoever wants to implement it.

Write Documentation

unyt could always use more documentation, whether as part of the official unyt docs, in docstrings, or even on the web in blog posts, articles, and such.

Submit Feedback

The best way to send feedback is to file an issue at

If you are proposing a feature:

  • Explain in detail how it would work.

  • Keep the scope as narrow as possible, to make it easier to implement.

  • Remember that this is a volunteer-driven project, and that contributions are welcome :)

Get Started!

Ready to contribute? Here’s how to set up unyt for local development.

The unyt test suite makes use of the tox test runner, which makes it easy to run tests on multiple python versions. However, this means that if all of the python versions needed by tox are not available, many of the tox tests will fail with errors about missing python executables.

This guide makes use of pyenv to set up all of the Python versions used in the unyt test suite. You do not have to use pyenv if you have other ways of managing your python evironment using your operating system’s package manager or conda.

  1. Fork the unyt repo on GitHub.

  2. Clone your fork locally:

    $ git clone
  3. Install pyenv:

    $ git clone $HOME/.pyenv
    $ export PYENV_ROOT="$HOME/.pyenv"
    $ export PATH="$HOME/.pyenv/bin:$PATH
    $ eval "$(pyenv init -)"
    $ pyenv install -s 3.9
    $ pyenv install -s 3.10
    $ pyenv install -s 3.11
    $ pyenv install -s 3.12
    $ pip install tox
  4. Install your local copy into a virtualenv or conda environment. You can also use one of the python interpreters we installed using pyenv:

    $ cd unyt/
    $ pyenv local 3.10
    $ python develop
  5. Create a branch for local development:

    $ git checkout -b name-of-your-bugfix-or-feature
  6. Edit files in the unyt repository, using your local python installation to test your edits.

  7. When you’re done making changes, check that your changes pass linting, and run the tests, including testing several Python versions with tox:

    $ pre-commit run --all-files
    $ pytest --doctest-modules --doctest-rst --doctest-plus
    $ pyenv local 3.9 3.10 3.11 3.12
    $ tox
    $ pyenv local 3.10

    To get pre-commit, pytest, pytest-doctestplus, and tox, just pip or conda install them into your python environment, as appropriate. For a pyenv environment you would use pip.

  8. Commit your changes and push your branch to GitHub:

    $ git add .
    $ git commit -m "Your detailed description of your changes."
    $ git push origin name-of-your-bugfix-or-feature
  9. Submit a pull request through the GitHub website.

Testing unyt

We use the pytest test runner as well as the tox test wrapper to manage running tests on various versions of python.

To run the tests on your copy of the unyt repository using your current python evironment, run pytest in the root of the repository using the following arguments:

$ cd unyt/
$ pytest --doctest-modules --doctest-rst --doctest-plus

These enable testing the docstrings and doctest examples scattered throughout the unyt and its documentation.

You will need to install pytest and pytest-doctestplus to run this command. Some tests depend on h5py, Pint, astropy, matplotlib and dask being installed.

If you would like to run the tests on multiple python versions, first ensure that you have multiple python versions visible on your $PATH, then simply execute tox in the root of the unyt repository. For example, using the pyenv environment we set up above:

$ cd unyt
$ pyenv local 3.9 3.10 3.11 3.12
$ tox

The tox package itself can be installed using the pip associated with one of the python installations. See the tox.ini file in the root of the repository for more details about our tox setup. Note that you do not need to install anything besides tox and the python versions needed by tox for this to work, tox will handle setting up the test environment, including installing any necessary dependencies via pip.

Pull Request Guidelines

Before you submit a pull request, check that it meets these guidelines:

  1. The pull request should include tests for functionality that is not already tested. We strive for 100% test coverage and pull requests should not add any new untested code. You can generate coverage reports locally by running the tox tests.

  2. If the pull request adds functionality the docs should be updated. If your new functionality adds new functions or classes to the public API, please add docstrings. If you modified an existing function or class in the public API, please update the existing docstrings. If you modify private implementation details, please use your judgment on documenting it with comments or docstrings.

  3. The pull request should work for Python 3.8, 3.9 and 3.10. Check in the GitHub interface for your pull request and make sure that the tests pass for all supported Python versions.


A reminder for the maintainers on how to deploy. Make sure all your changes are committed (including an entry in HISTORY.rst and adding any new contributors to AUTHORS.rst).

If doing a bugfix release, you may need to create a - or checkout an existing - backport branch named vX.Y.x where X and Y represent the relevant major and minor version numbers, and the lowercase x is literal. Otherwise you may just release from the development branch. Once you are ready, create a tag and push it to the upstream repository:

$ git tag vX.Y.Z            # where X, Y and Z should be meaningful major, minor and micro version numbers
$ git push upstream --tag   # assuming the mother repo yt-project/unyt is set as a remote under the name "upstream"

If the tests pass you can then subsequently manually upload to PyPI:

$ python -m pip install --upgrade pip
$ python -m pip install --upgrade build twine
$ rm -r build dist
$ python -m build

Do a test publication:

$ twine check dist/*
$ twine upload dist/* --repository-url

Test the result (best using a fresh environment here):

$ python -m pip install pytest
$ python -m pip install --index-url unyt --extra-index-url --force
$ python -c "import unyt; unyt.test()"
$ python -m pip install --index-url unyt --extra-index-url --no-binary unyt --force
$ python -c "import unyt; unyt.test()"

Finally, if everything works well, push the release to the normal PyPI index as:

$ twine upload dist/*