Contributing to Black

Welcome! Happy to see you willing to make the project better. Have you read the entire user documentation yet?

Bird’s eye view

In terms of inspiration, Black is about as configurable as gofmt. This is deliberate.

Bug reports and fixes are always welcome! Please follow the issue template on GitHub for best results.

Before you suggest a new feature or configuration knob, ask yourself why you want it. If it enables better integration with some workflow, fixes an inconsistency, speeds things up, and so on - go for it! On the other hand, if your answer is “because I don’t like a particular formatting” then you’re not ready to embrace Black yet. Such changes are unlikely to get accepted. You can still try but prepare to be disappointed.


Development on the latest version of Python is preferred. As of this writing it’s 3.8. You can use any operating system. I am using macOS myself and CentOS at work.

Install all development dependencies using:

$ pipenv install --dev
$ pipenv shell
$ pre-commit install

If you haven’t used pipenv before but are comfortable with virtualenvs, just run pip install pipenv in the virtualenv you’re already using and invoke the command above from the cloned Black repo. It will do the correct thing.

Before submitting pull requests, run tests with:

$ python -m unittest


If you’re fixing a bug, add a test. Run it first to confirm it fails, then fix the bug, run it again to confirm it’s really fixed.

If adding a new feature, add a test. In fact, always add a test. But wait, before adding any large feature, first open an issue for us to discuss the idea first.


Thanks again for your interest in improving the project! You’re taking action when most people decide to sit and watch.