Python package maintenance

Support for Python 2

Since Python 2.7 reached EOL, Gentoo is currently phasing out support for Python 2. Unless your package or its reverse dependencies really need it, you should omit it from PYTHON_COMPAT. If you’re adding a new package and it does not support Python 3, do not add it.

Many upstreams are removing Python 2 support from new releases of their software. We remove it proactively whenever reverse dependencies permit in order to anticipate this and avoid having to deal with lots of reverse dependencies afterwards.

Packages that do not support Python 3 and are unlikely to start supporting it soon are being slowly removed.

Which implementations to test new packages for?

The absolute minimum set of targets are the current default targets found in profiles/base/make.defaults. However, developers are strongly encouraged to test at least the next Python 3 version in order to ease future transition, and preferably all future versions.

Marking for PyPy3 is optional. At this moment, we do not aim for wide coverage of PyPy3 support.

Adding new Python implementations to existing packages

New Python implementations can generally be added to existing packages without a revision bump. This is because the new dependencies are added conditionally to new USE flags. Since the existing users can not have the new flags enabled, the dependencies do not need to be proactively added to existing installations.

This usually applies to stable packages as well as new Python targets are generally use.stable.mask-ed. This means that stable users will not be able to enable newly added flags and therefore the risk of the change breaking stable systems is minimal.

Which packages can be (co-)maintained by the Python project?

A large part of the Python ecosystem is fairly consistent, making it feasible for (co-)maintenance by the Gentoo Python team.

As a rule of thumb, Python team is ready to maintain packages specific to the Python ecosystem and useful for the general population of Python programmers. This includes Python interpreters and tooling, packages purely providing Python modules and extensions and utilities specific to the Python language.

However, the Python team has limited manpower, therefore it may reject packages that have high maintenance requirements. As a rule, Python team does not accept packages without working tests.

If your package matches the above profile, feel free to ask a member of the Python project whether they would like to (co-)maintain the package. However, if you are not a member of the project, please do not add us without asking first.

Porting packages to a new EAPI

When porting packages to a new EAPI, please take care not to port the dependencies of Portage prematurely. This generally includes app-portage/gemato, dev-python/setuptools and their recursive dependencies.

Ideally, these ebuilds carry an appropriate note above their EAPI line, e.g.:

# please keep this ebuild at EAPI 7 -- sys-apps/portage dep
EAPI=7

This does not apply to test dependencies — they are not strictly necessary to install a new Portage version.

Monitoring new package versions

PyPI release feeds

The most efficient way to follow new Python package releases are the feeds found on PyPI. These can be found in the package’s “Release history” tab, as “RSS feed”.

The Gentoo Python project maintains a comprehensive list of PyPI feeds for packages in dev-python/ category (as well as other important packages maintained by the Python team) in OPML format.

Checking via pip

The pip list --outdated command described in a followup section can also be used to verify installed packages against their latest PyPI releases. However, this is naturally limited to packages installed on the particular system, and does not account for newer versions being already available in the Gentoo repository.

Repology

Repology provides a comprehensive service for tracking distribution package versions and upstream releases. The easiest ways to find Python packages present in the Gentoo repository is to search by their maintainer’s e-mail or category (e.g. dev-python). When searching by name, the majority of Python-specific package use python: prefix in their Repology names.

Unfortunately, Repology is very susceptible to false positives. Examples of false positives include other distributions using custom version numbers, replacing packages with forks or simply Repology confusing different packages with the same name. If you find false positives, please use the ‘Report’ option to request a correction.

Please also note that Repology is unable to handle the less common version numbers that do not have a clear mapping to Gentoo version syntax (e.g. .post releases).

Routine checks on installed Python packages

The following actions are recommended to be run periodically on systems used to test Python packages. They could be run e.g. via post-sync actions.

pip check

pip check (provided by dev-python/pip) can be used to check installed packages for missing dependencies and version conflicts:

$ python3.10 -m pip check
meson-python 0.6.0 requires ninja, which is not installed.
cx-freeze 6.11.1 requires patchelf, which is not installed.
openapi-spec-validator 0.4.0 has requirement openapi-schema-validator<0.3.0,>=0.2.0, but you have openapi-schema-validator 0.3.0.
cx-freeze 6.11.1 has requirement setuptools<=60.10.0,>=59.0.1, but you have setuptools 62.6.0.

This tool checks the installed packages for a single Python implementation only, so you need to run it for every installed interpreter separately.

In some cases the issues are caused by unnecessary version pins or upstream packages listing optional dependencies as obligatory. The preferred fix is to fix the package metadata rather than modifying the dependencies in ebuild.

Warning

pip does not support the Provides metadata, so it can produce false positives about certifi dependency. Please ignore these:

httpcore 0.15.0 requires certifi, which is not installed.
httpx 0.23.0 requires certifi, which is not installed.
sphobjinv 2.2.2 requires certifi, which is not installed.
requests 2.28.0 requires certifi, which is not installed.

pip list --outdated

pip list --outdated (provided by dev-python/pip) can be used to check whether installed packages are up-to-date. This can help checking for pending version bumps, as well as to detect wrong versions in installed metadata:

$ pip3.11 list --outdated
Package                  Version           Latest  Type
------------------------ ----------------- ------- -----
dirty-equals             0                 0.4     wheel
filetype                 1.0.10            1.0.13  wheel
mercurial                6.1.3             6.1.4   sdist
node-semver              0.8.0             0.8.1   wheel
PyQt-builder             1.12.2            1.13.0  wheel
PyQt5                    5.15.6            5.15.7  wheel
PyQt5-sip                12.10.1           12.11.0 sdist
PyQtWebEngine            5.15.5            5.15.6  wheel
Routes                   2.5.1.dev20220522 2.5.1   wheel
selenium                 3.141.0           4.3.0   wheel
sip                      6.6.1             6.6.2   wheel
sphinxcontrib-websupport 1.2.4.dev20220515 1.2.4   wheel
uri-template             0.0.0             1.2.0   wheel
watchfiles               0.0.0             0.15.0  wheel
watchgod                 0.0.dev0          0.8.2   wheel

Again, the action applies to a single Python implementation only and needs to be repeated for all of them.

Particularly note the packages with versions containing only zeroes in the above list — this is usually a sign that the build system does not recognize the version correctly. In some cases, the only working solution would be to sed the correct version in.

The additional dev suffix is usually appended via tag_build option in setup.cfg. This causes the version to be considered older than the actual release, and therefore the respective options need to be stripped.

gpy-verify-deps

gpy-verify-deps (provided by app-portage/gpyutils) compares the ebuild dependencies of all installed Python packages against their metadata. It reports the dependencies that are potentially missing in ebuilds, as well as dependencies potentially missing [${PYTHON_USEDEP}]. For the latter, it assumes that all dependencies listed in package metadata are used as Python modules.

$ gpy-verify-deps
[...]
=dev-python/tempest-31.0.0: missing dependency: dev-python/oslo-serialization [*]
=dev-python/tempest-31.0.0: missing dependency: dev-python/cryptography [*]
=dev-python/tempest-31.0.0: missing dependency: dev-python/stestr [*]
=dev-python/versioningit-2.0.0: missing dependency: dev-python/tomli [*]
=dev-python/versioningit-2.0.0: missing dependency: dev-python/importlib_metadata [python3.8 python3.9]
=dev-python/wstools-0.4.10-r1: missing dependency: dev-python/setuptools [*]

The check is done for all installed interpreters. The report indicates whether the dependency upstream is unconditional ([*]) or specific to a subset of Python implementations.

Similarly to pip check results, every dependency needs to be verified. In many cases, upstream metadata lists optional or build-time dependencies as runtime dependencies, and it is preferable to strip them than to copy the mistakes into the ebuild.