古いバージョンのPython へのサポートをやめる#

The ability to drop support for older Python versions is enabled by the standard コアとなるメタデータの仕様 1.2 specification via the "Requires-Python" attribute.

Metadata 1.2+ installers, such as Pip, will adhere to this specification by matching the current Python runtime and comparing it with the required version in the package metadata. If they do not match, it will attempt to install the last package distribution that supported that Python runtime.

This mechanism can be used to drop support for older Python versions, by amending the Requires-Python attribute in the package metadata.

要求事項#

This workflow requires that the user installing the package uses Pip [1], or another installer that supports the Metadata 1.2 specification.

universal wheelsの取り扱い#

Traditionally, Setuptools projects providing Python code that is semantically compatible with both Python 2 and Python 3, produce wheels that have a py2.py3 tag in their names. When dropping support for Python 2, it is important not to forget to change this tag to just py3. It is often configured within setup.cfg under the [bdist_wheel] section by setting universal = 1.

このメソッドを使うのであれば、このオプションないしセクションを削除するか、または、明示的に universal を 0 に設定してください。

# setup.cfg

[bdist_wheel]
universal = 0  # Make the generated wheels have "py3" tag

ヒント

Regarding deprecated direct setup.py invocations, passing the --universal flag on the command line could override this setting.

要求する Python のバージョンを定義する#

1. Install twine#

Ensure that you have twine available at its latest version. Steps:

python3 -m pip install --upgrade twine

py -m pip install --upgrade twine

2. サポートする Python 配布物のバージョンの範囲を指定する#

Set the version ranges declaring which Python distributions are supported within your project's pyproject.toml. The requires-python configuration field corresponds to the Requires-Python core metadata field:

[build-system]
...

[project]
requires-python = ">= 3.8" # At least Python 3.8

You can specify version ranges and exclusion rules (complying with the バージョン指定子 specification), such as at least Python 3.9. Or, at least Python 3.7 and beyond, skipping the 3.7.0 and 3.7.1 point releases:

requires-python = ">= 3.9"
requires-python = ">= 3.7, != 3.7.0, != 3.7.1"

If using the Setuptools build backend, consult the dependency-management documentation for more options.

注意

Avoid adding upper bounds to the version ranges, e. g. ">= 3.8, < 3.10". Doing so can cause different errors and version conflicts. See the discourse-discussion for more information.

3. 公開の前にメタデータを検証する#

Python のソースコードパッケージ (あなたがダウンロードしたzipファイルやtar.gzファイル) の中には、PKG-INFO という名前のテキストファイルがあります。

This file is generated by the build backend when it generates the source package. The file contains a set of keys and values, the list of keys is part of the PyPA standard metadata format.

生成されたファイルの内容はこのようになっています:

tar xfO dist/my-package-1.0.0.tar.gz my-package-1.0.0/PKG-INFO

パッケージを公開する前に、以下のことが適切かどうかを検証してください。

  • If you have upgraded correctly, the Metadata-Version value should be 1.2 or higher.

  • The Requires-Python field is set and matches your specification in the configuration file.

4. Publishing the package#

Proceed as suggested in プロジェクトをPyPIにアップロードする.

Dropping a Python version#

In principle, at least metadata support for Python versions should be kept as long as possible, because once that has been dropped, people still depending on a version will be forced to downgrade. If however supporting a specific version becomes a blocker for a new feature or other issues occur, the metadata Requires-Python should be amended. Of course this also depends on whether the project needs to be stable and well-covered for a wider range of users.

Each version compatibility change should have its own release.

Tip

When dropping a Python version, it might also be rewarding to upgrade the project's code syntax generally, apart from updating the versions used in visible places (like the testing environment). Tools like pyupgrade or ruff can automate some of this work.