Removing Python 3.6 Support from My Packages

2022-01-11-drop-python-3.6.sh

Below is the script I used, followed by some explanation. You can also find this script within my scripts repo, alongside other “modify repo” scripts.

#!/bin/sh
set -eu

git diff --exit-code
git checkout main
git pull

sd ' +- 3\.6\n' '' .github/workflows/main.yml
sd ' +py36.*\n' '' tox.ini
sd -s 'py{36,37' 'py{37' tox.ini
sd -s "target-version = ['py36']" "target-version = ['py37']" pyproject.toml
sd '\[--py36-plus' '[--py37-plus' .pre-commit-config.yaml
sd -s "Python 3.6 to " "Python 3.7 to " README.rst
sd ' +Programming Language :: Python :: 3\.6\n' '' setup.cfg
sd -s 'python_requires = >=3.6' 'python_requires = >=3.7' setup.cfg
sd -f m ' +subprocess\.run\((\n|.)*?python3\.6(\n|.)*?\)\n' '' requirements/compile.py
rm requirements/py36*txt
# shellcheck disable=SC2016
sd -f m '(=======
History
=======)' '$1

* Drop Python 3.6 support.' HISTORY.rst
git add .github/workflows/main.yml tox.ini pyproject.toml .pre-commit-config.yaml README.rst setup.cfg requirements/ HISTORY.rst

if [ -f docs/installation.rst ]; then
    sd -s "Python 3.6 to " "Python 3.7 to " README.rst
    git add docs/installation.rst
fi

git switch -c drop_python_3.6
git commit -m "Drop Python 3.6 support

Its EOL was 2021-12-23: https://www.python.org/dev/peps/pep-0494/#lifespan ."

git push -u origin "$(git rev-parse --abbrev-ref HEAD)"
gh pr create --fill
gh pr merge --squash --delete-branch --auto

A brief explanation:

• set -eu enables some strictness options. I always use these as they reduce surprises from shell scripts.

• The three first git commands check that the repository has no uncommitted changes, is on its its main branch, and up to date.

• sd is a find-and-replace tool. It’s a Rust-based alternative to the classic sed. I find it easier to use.

  These sd commands rewrite Python 3.6 references in known places throughout my repository files:

  • .github/workflows/main.yml - configuration for GitHub Actions, the CI system.
  • tox.ini - configuration for tox, the test runner.
  • pyproject.toml - configuration for Black, the formatter.
  • .pre-commit-config.yaml - configuration for pyupgrade, the syntax updater.
  • README.rst - installation instructions.
  • setup.cfg - classifiers and minimum Python version configuration for PyPI.
  • requirements/compile.py - a script for running pip-compile for each tox environment.
  • HISTORY.rst - the changelog.

• There’s a conditional block around rewriting docs/installation.rst, that checks for its existence. Most of my projects use only their README for documentation, so they don’t have a docs/ directory, and attempting to sd the file fails. But Django-MySQL uses Sphinx, within docs/, so I want to rewrite that.

• The remaining git commands create a branch, commit it, and push it to GitHub.

• The gh commands are the GitHub CLI, being used to create a PR and set it to auto-merge if the tests pass.

pypugrade Rewrites

Shout outs to pyupgrade, which removes old blocks guarded by outdated sys.version_info checks. This feature saved me a bunch of fiddly changes. pre-commit.ci ran pyupgrade for me, and pushed the changes back to the PR.

For example, in django-linear-migrations, pyupgrade rewrote this block:

from types import ModuleType

if sys.version_info >= (3, 7):

    def is_namespace_module(module: ModuleType) -> bool:
        return module.__file__ is None

else:

    def is_namespace_module(module: ModuleType) -> bool:
        return getattr(module, "__file__", None) is None

…to just the Python 3.7+ side:

from types import ModuleType


def is_namespace_module(module: ModuleType) -> bool:
    return module.__file__ is None

Cool.

Remaining References

A handful of repositories had extra references to Python 3.6/3.7 that needed removing. I found these with this rg (ripgrep) command:

rg --color always -g '!*.txt' '\b3\b.*\b[67]\b' | less

--color always keeps the colour when piped to less, which helped me skim through the results.

New Versions

After merging the respective PRs, I released new versions of all packages. For those still on Python 3.6, Pip will obey the python_requires field and find the older versions. If you use any packages please upgrade and check everything’s okay for you.

Fin

Bye bye Python 3.6. You were a good release.

f"F" to pay respects,

—Adam