We want to make contributing to this project as easy and transparent as possible.

Getting Started

µsort requires Python 3.6 or newer. pyenv can help install and manage multiple versions of Python.

Clone the repository and set up your local workspace:

$ make venv

$ source .venv/bin/activate
(usort) $

This will create a virtualenv, install dependencies, and set up µsort as an editable package in the virtualenv. This enables running the usort command from your workspace while activated.


You can run tests and linters manually against your virtualenv:

(usort) $ make test lint

You can also run the test suite against all supported versions of Python at once using Tox:

$ tox -p all


µsort uses Sphinx for building documentation, and all documentation is stored in the docs/ directory at the root of the repository. If you are not familiar with writing reStructuredText, there is a good reStructuredText primer in the Sphinx documentation.

After making changes, build the documentation and open the resulting HTML in your browser of choice to make sure your changes have rendered correctly:

(usort) $ make html

(usort) $ python -m webbrowser "file://$PWD/html/index.html"

Pull Requests

We actively welcome your pull requests.

  1. Fork the repo and push your changes to a separate branch.

  2. If you’ve added code that should be tested, add tests.

  3. If you’ve changed APIs, update the documentation.

  4. Ensure the test suite passes.

  5. Make sure your code lints.

  6. If you haven’t already, complete the Contributor License Agreement (“CLA”).

Contributor License Agreement (“CLA”)

In order to accept your pull request, we need you to submit a CLA. You only need to do this once to work on any of Facebook’s open source projects.

Complete your CLA here:


We use GitHub issues to track public bugs. Please ensure your description is clear and has sufficient instructions to be able to reproduce the issue.

Facebook has a bounty program for the safe disclosure of security bugs. In those cases, please go through the process outlined on that page and do not file a public issue.


By contributing to µsort, you agree that your contributions will be licensed under the LICENSE file in the root directory of this source tree.