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# Release process

## Release Cadence

The pip project has a release cadence of releasing whatever is on `main` every 3 months. This gives users a predictable pattern for when releases are going to happen and prevents locking up improvements for fixes for long periods of time, while still preventing massively fracturing the user base with version numbers.

Our release months are January, April, July, October. The release date within that month will be up to the release manager for that release. If there are no changes, then that release month is skipped and the next release will be 3 months later.

The version number of pip is `YY.N`, where `YY` is the year of the release and `N` identifies the quarter of the year (0-3).

The release manager may, at their discretion, choose whether or not there will be a pre-release period for a release, and if there is may extend that period into the next month if needed.

Because releases are made direct from the `main` branch, it is essential that `main` is always in a releasable state. It is acceptable to merge PRs that partially implement a new feature, but only if the partially implemented version is usable in that state (for example, with reduced functionality or disabled by default). In the case where a merged PR is found to need extra work before being released, the release manager always has the option to back out the partial change prior to a release. The PR can then be reworked and resubmitted for the next release.

Vendoring updates will be picked up from the `main` branch, as for any other update. Ideally, vendoring updates should be merged between releases, just like any other change. If there are outstanding updates to vendored packages, the release manager may at their discretion choose to do a vendoring update before the release. However this is not a requirement and in particular, updates to vendored packages that fix issues in pip should be merged proactively, to ensure that they will be present in the next release.

## Deprecation Policy

Any change to pip that removes or significantly alters user-visible behavior that is described in the pip documentation will be deprecated for a minimum of 6 months before the change occurs.

Certain changes may be fast tracked and have a deprecation period of 3 months. This requires at least two members of the pip team to be in favor of doing so, and no pip maintainers opposing.

Deprecation will take the form of a warning being issued by pip when the feature is used. Longer deprecation periods, or deprecation warnings for behavior changes that would not normally be covered by this policy, are also possible depending on circumstances, but this is at the discretion of the pip maintainers.

Note that the documentation is the sole reference for what counts as agreed behavior. If something isn’t explicitly mentioned in the documentation, it can be changed without warning, or any deprecation period, in a pip release. However, we are aware that the documentation isn’t always complete - PRs that document existing behavior with the intention of covering that behavior with the above deprecation process are always acceptable, and will be considered on their merits.

Note

pip has a helper function for making deprecation easier for pip maintainers. The supporting documentation can be found in the source code of `pip._internal.utils.deprecation.deprecated`. The function is not a part of pip’s public API.

## Supported Versions

The latest version of the pip is the only supported version, previous versions should be considered unsupported. Users are encouraged to make regular updates to their version of pip in order to remain supported.

### Python 2 Support

pip 20.3 was the last version of pip that supported Python 2. Bugs reported with pip which only occur on Python 2.7 will likely be closed as “won’t fix” issues by pip’s maintainers.

### Python Support Policy

pip supports CPython versions that are not end-of-life. Older versions of CPython may be supported at the discretion of pip maintainers (based on criteria such as download statistics on PyPI, Python versions supported by the vendored dependencies and maintenance burden).

pip maintainers accept pull requests to support other Python implementations, but the pip CI does not test for compatibility with them.

## Feature Flags

### `--use-deprecated`

Example: `--use-deprecated=legacy-resolver`

Use for features that will be deprecated. Deprecated features should remain available behind this flag for at least six months, as per the deprecation policy.

Features moved behind this flag should always include a warning that indicates when the feature is scheduled to be removed.

Once the feature is removed, users who use the flag should be shown an error.

### `--use-feature`

Example: `--use-feature=2020-resolver`

Use for new features that users can test before they become pip’s default behaviour (e.g. alpha or beta releases).

Once the feature becomes the default behaviour, this flag can remain in place, but should issue a warning telling the user that it is no longer necessary.

## Release Process

### Creating a new release

1. Ensure you have the latest `nox` installed.

2. Create a new `release/YY.N` branch off `main` and switch to it.

3. Prepare for release using `nox -s prepare-release -- YY.N`. This will update the relevant files and tag the correct commit.

4. Submit the `release/YY.N` branch as a pull request and ensure CI passes. Merge the changes back into `main` and pull them back locally.

5. Push the tag created by `prepare-release`. This will trigger the release workflow on GitHub.

6. Go to https://github.com/pypa/pip/actions, find the latest `Publish Python 🐍 distribution 📦 to PyPI` workflow run, open it, wait for the build step to complete, then approve the PyPI environment to let the publishing step run. If you desire, you have the possibility to download and inspect the artifacts before approving.

7. Regenerate the `get-pip.py` script in the get-pip repository (as documented there) and commit the results.

8. Submit a Pull Request to CPython adding the new version of pip to `Lib/ensurepip/_bundled`, removing the existing version, and adjusting the versions listed in `Lib/ensurepip/__init__.py`.

Note

If the release dropped the support of an obsolete Python version `M.m`, a new `M.m/get-pip.py` needs to be published: update the `all` task from `tasks/generate.py` in get-pip repository and make a pull request to psf-salt repository to add the new `get-pip.py` (and its directory) to `salt/pypa/bootstrap/init.sls`.

Note

If the `get-pip.py` script needs to be updated due to changes in pip internals and if the last `M.m/get-pip.py` published still uses the default template, make sure to first duplicate `templates/default.py` as `templates/pre-YY.N.py` before updating it and specify in `tasks/generate.py` that `M.m/get-pip.py` now needs to use `templates/pre-YY.N.py`.

### Creating a bug-fix release

Sometimes we need to release a bugfix release of the form `YY.N.Z+1`. In order to create one of these the changes should already be merged into the `main` branch.

Note that this process is only needed when there are changes on the main branch that you do not want to include in the bugfix release. For a bugfix release that will include everything that is on the `main` branch, the above process for creating a new release can be used, simply changing the version number.

1. Create a new `release/YY.N.Z+1` branch off of the `YY.N` tag using the command `git checkout -b release/YY.N.Z+1 YY.N`.

2. Cherry pick the fixed commits off of the `main` branch, fixing any conflicts.

3. Run `nox -s prepare-release -- YY.N.Z+1`.

4. Merge main into your release branch and drop the news files that have been included in your release (otherwise they would also appear in the `YY.N+1` changelog)

5. Push the `release/YY.N.Z+1` branch to github and submit a PR for it against the `main` branch and wait for the tests to run.

6. Once tests run, merge the `release/YY.N.Z+1` branch into `main`, and follow the above release process starting with step 5.