Pip’s internals#

We have an in-progress guide to the Architecture of pip’s internals. It might be helpful as you dive in.

Submitting Pull Requests#

Submit pull requests against the main branch, providing a good description of what you’re doing and why. You must have legal permission to distribute any code you contribute to pip and it must be available under the MIT License.

Provide tests that cover your changes and run the tests locally first. pip supports multiple Python versions and operating systems. Any pull request must consider and work on all these platforms.

Pull requests should be small to facilitate easier review. Keep them self-contained, and limited in scope. Studies have shown that review quality falls off as patch size grows. Sometimes this will result in many small PRs to land a single large feature. In particular, pull requests must not be treated as “feature branches”, with ongoing development work happening within the PR. Instead, the feature should be broken up into smaller, independent parts which can be reviewed and merged individually.

Additionally, avoid including “cosmetic” changes to code that is unrelated to your change, as these make reviewing the PR more difficult. Examples include re-flowing text in comments or documentation, or adding or removing blank lines or whitespace within lines. Such changes can be made separately, as a “formatting cleanup” PR, if needed.

Automated Testing#

All pull requests and merges to ‘main’ branch are tested using GitHub Actions based on our .github/workflows files. More details about pip’s Continuous Integration can be found in the CI Documentation

You can find the status and results to the CI runs for your PR on GitHub’s web UI for the pull request. You can also find links to the CI services’ pages for the specific builds in the form of “Details” links, in case the CI run fails and you wish to view the output.

To trigger CI to run again for a pull request, you can close and open the pull request or submit another change to the pull request. If needed, project maintainers can manually trigger a restart of a job/build.

To understand the broader software architecture around dependency resolution in pip, and how we automatically test this functionality, see Testing the next-gen pip dependency resolver.

NEWS Entries#

The NEWS.rst file is managed using towncrier and all non trivial changes must be accompanied by a news entry.

To add an entry to the news file, first you need to have created an issue describing the change you want to make. A Pull Request itself may function as such, but it is preferred to have a dedicated issue (for example, in case the PR ends up rejected due to code quality reasons).

Once you have an issue or pull request, you take the number and you create a file inside of the news/ directory, named after that issue number with a “type” of removal, feature, bugfix, or doc associated with it.

If your issue or PR number is 1234 and this change is fixing a bug, then you would create a file news/1234.bugfix.rst. PRs can span multiple categories by creating multiple files (for instance, if you added a feature and deprecated/removed the old feature at the same time, you would create news/NNNN.feature.rst and news/NNNN.removal.rst).

If a PR touches multiple issues/PRs, you may create a file for each of them with the exact same contents and Towncrier will deduplicate them.

Contents of a NEWS entry#

The contents of this file are reStructuredText formatted text that will be used as the content of the news file entry. You do not need to reference the issue or PR numbers in the entry, since towncrier will automatically add a reference to all of the affected issues when rendering the NEWS file. There must be a newline at the end of the file.

In order to maintain a consistent style in the NEWS.rst file, it is preferred to keep the news entry to the point, in sentence case, shorter than 80 characters and in an imperative tone -- an entry should complete the sentence “This change will …”. In rare cases, where one line is not enough, use a summary line in an imperative tone followed by a blank line separating it from a description of the feature/change in one or more paragraphs, each wrapped at 80 characters. Remember that a news entry is meant for end users and should only contain details relevant to an end user.

Choosing the type of NEWS entry#

A trivial change is anything that does not warrant an entry in the news file. Some examples are: Code refactors that don’t change anything as far as the public is concerned, typo fixes, white space modification, etc. To mark a PR as trivial a contributor simply needs to add a randomly named, empty file to the news/ directory with the extension of .trivial.rst. If you are on a POSIX like operating system, one can be added by running touch news/$(uuidgen).trivial.rst. On Windows, the same result can be achieved in Powershell using New-Item "news/$([guid]::NewGuid()).trivial.rst". Core committers may also add a “skip news” label to the PR which will accomplish the same thing.

Upgrading, removing, or adding a new vendored library gets a special mention using a news/<library>.vendor.rst file. This is in addition to any features, bugfixes, or other kinds of news that pulling in this library may have. This uses the library name as the key so that updating the same library twice doesn’t produce two news file entries.

Changes to the processes, policies, or other non code related changed that are otherwise notable can be done using a news/<name>.process.rst file. This is not typically used, but can be used for things like changing version schemes, updating deprecation policy, etc.

Updating your branch#

As you work, you might need to update your local main branch up-to-date with the main branch in the main pip repository, which moves forward as the maintainers merge pull requests. Most people working on the project use the following workflow.

This assumes that you have Git configured so that when you run the following command:

git remote -v

Your output looks like this:

origin (fetch)
origin (push)
upstream (fetch)
upstream (push)

In the example above, USERNAME is your username on GitHub.

First, fetch the latest changes from the main pip repository, upstream:

git fetch upstream

Then, check out your local main branch, and rebase the changes on top of it:

git checkout main
git rebase upstream/main

At this point, you might have to resolve merge conflicts. Once this is done, push the updates you have just made to your local main branch to your origin repository on GitHub:

git checkout main
git push origin main

Now your local main branch and the main branch in your origin repo have been updated with the most recent changes from the main pip repository.

To keep your branches updated, the process is similar:

git checkout awesome-feature
git fetch upstream
git rebase upstream/main

Now your branch has been updated with the latest changes from the main branch on the upstream pip repository.

It’s good practice to back up your branches by pushing them to your origin on GitHub as you are working on them. To push a branch, run this command:

git push origin awesome-feature

In this example, <awesome-feature> is the name of your branch. This will push the branch you are working on to GitHub, but will not create a PR.

Once you have pushed your branch to your origin, if you need to update it again, you will have to force push your changes by running the following command:

git push -f origin awesome-feature

The -f (or --force) flag after push forces updates from your local branch to update your origin branch. If you have a PR open on your branch, force pushing will update your PR. (This is a useful command when someone requests changes on a PR.)

If you get an error message like this:

! [rejected]        awesome-feature -> awesome-feature (non-fast-forward)
error: failed to push some refs to ''
hint: Updates were rejected because the tip of your current branch is behind
hint: its remote counterpart. Integrate the remote changes (e.g.
hint: 'git pull ...') before pushing again.
hint: See the 'Note about fast-forwards' in 'git push --help' for details.

Try force-pushing your branch with push -f.

The main branch in the main pip repository gets updated frequently, so you might have to update your branch at least once while you are working on it.

Thank you for your contribution!

Becoming a maintainer#

If you want to become an official maintainer, start by helping out.

As a first step, we welcome you to triage issues on pip’s issue tracker. pip maintainers provide triage abilities to contributors once they have been around for some time (probably at least 2-3 months) and contributed positively to the project. This is optional and highly recommended for becoming a pip maintainer.

Later, when you think you’re ready (probably at least 5 months after starting to triage), get in touch with one of the maintainers and they will initiate a vote among the existing maintainers.


Upon becoming a maintainer, a person should be given access to various pip-related tooling across multiple platforms. These are noted here for future reference by the maintainers:

  • GitHub Push Access

  • PyPI Publishing Access

  • CI Administration capabilities

  • ReadTheDocs Administration capabilities