check-python-versions

This is a tool for Python package maintainers who want to explicitly state which Python versions they support.

The problem: to properly support e.g. Python 2.7 and 3.6+ you have to run tests with these Pythons. This means

• you need a tox.ini with envlist = py27, py36, py37, py38, py39
• you need a .travis.yml with python: [ 2.7, 3.6, 3.7, 3.8, 3.9 ]
• if you support Windows, you need an appveyor.yml with %PYTHON% set to C:\Python2.7, C:\Python3.5, and so on
• if you're building manylinux wheels you need to ... you get the idea
• you have to tell the users which Python versions you support by specifying trove classifiers like "Programming Language :: Python :: 2.7"
• you probably also want to tell pip which versions you support by specifying python_requires=">= 2.7, !=3.0.* ..." because AFAIU PyPI classifiers are not fine-grained enough

Keeping all these lists consistent is a pain.

The solution: check-python-versions will compare these lists and warn you if they don't match

$ check-python-versions ~/projects/*
/home/mg/projects/check-manifest:

setup.py says:              2.7, 3.6, 3.7, 3.8, 3.9, PyPy
- python_requires says:     2.7, 3.6, 3.7, 3.8, 3.9
tox.ini says:               2.7, 3.6, 3.7, 3.8, 3.9, PyPy, PyPy3
.travis.yml says:           2.7, 3.6, 3.7, 3.8, 3.9, PyPy, PyPy3
appveyor.yml says:          2.7, 3.6, 3.7, 3.8, 3.9


/home/mg/projects/dozer:

setup.py says:              2.7, 3.6, 3.7, 3.8, 3.9
tox.ini says:               2.7, 3.6, 3.7, 3.8, 3.9
.travis.yml says:           2.7, 3.6, 3.7, 3.8, 3.9
appveyor.yml says:          2.7, 3.6, 3.7, 3.8, 3.9


/home/mg/projects/eazysvn:

setup.py says:              2.7, 3.6, 3.7, 3.8, 3.9, PyPy
tox.ini says:               2.7, 3.6, 3.7, 3.8, 3.9, PyPy, PyPy3
.travis.yml says:           2.7, 3.6, 3.7, 3.8, 3.9, PyPy, PyPy3
appveyor.yml says:          2.7, 3.6, 3.7, 3.8, 3.9

...

all ok!

Installation

You need Python 3.6 or newer (f-strings!) to run check-python-versions. Install it with

python3 -m pip install check-python-versions

Usage

$ check-python-versions --help
usage: check-python-versions [-h] [--version] [--expect VERSIONS]
                             [--skip-non-packages] [--only FILES]
                             [--add VERSIONS] [--drop VERSIONS]
                             [--update VERSIONS] [--diff] [--dry-run]
                             [where [where ...]]

verify that supported Python versions are the same in setup.py, tox.ini,
.travis.yml and appveyor.yml

positional arguments:
  where                directory where a Python package with a setup.py and
                       other files is located

optional arguments:
  -h, --help           show this help message and exit
  --version            show program's version number and exit
  --expect VERSIONS    expect these versions to be supported, e.g. --expect
                       2.7,3.5-3.8
  --skip-non-packages  skip arguments that are not Python packages without
                       warning about them
  --only FILES         check only the specified files (comma-separated list,
                       e.g. --only tox.ini,appveyor.yml)

updating supported version lists (EXPERIMENTAL):
  --add VERSIONS       add these versions to supported ones, e.g --add 3.9
  --drop VERSIONS      drop these versions from supported ones, e.g --drop
                       2.6,3.4
  --update VERSIONS    update the set of supported versions, e.g. --update
                       2.7,3.5-3.9
  --diff               show a diff of proposed changes
  --dry-run            verify proposed changes without writing them to disk

If run without any arguments, check-python-versions will look for a setup.py in the current working directory.

Exit status is 0 if all Python packages had consistent version numbers (and, if --expect is specified, those numbers match your stated expectations).

If you specify multiple directories on the command line, then all packages that failed a check will be listed at the end of the run, separated with spaces, for easier copying and pasting onto shell command lines. This is helpful when, e.g. you want to run

check-python-versions ~/src/zopefoundation/*

to check all 380+ packages, and then want re-run the checks only on the failed ones, for a faster turnabout.

There's also experimental support for updating supported Python versions so you can do things like

check-python-versions ~/projects/* --add 3.9 --dry-run --expect 2.7,3.6-3.9
check-python-versions ~/projects/* --drop 3.4 --diff
check-python-versions ~/projects/* --update 2.7,3.6- --dry-run --diff
check-python-versions ~/projects/* --add 3.9 --drop=-2.6,-3.5

(the last one will show a diff for each file and ask for interactive confirmation before making any changes.)

Programmatically updating human-writable files is difficult, so expect bugs (and please file issues).

Files

setup.py is the only required file; if any of the others are missing, they'll be ignored (and this will not be considered a failure).

• setup.py: the classifiers argument passed to setup() is expected to have classifiers of the form:

  classifiers=[
      ...
      "Programming Language :: Python :: x.y",
      ...
  ],
  

  check-python-versions will attempt to parse the file and walk the AST to extract classifiers, but if that fails, it'll execute python setup.py --classifiers and parse the output.

  There's rudimentary support for dynamically-computed classifiers if at least one part is a list literal, e.g. this can work and can even be updated

  classifiers=[
      ...
      "Programming Language :: Python :: x.y",
      ...
  ] + ... expression that computes extra classifiers ...,
  

• setup.py: the python_requires argument passed to setup(), if present:

  python_requires=">=2.7, !=3.0.*, !=3.1.*",
  

  check-python-versions will attempt to parse the file and walk the AST to extract the python_requires value. It expects to find a string literal or a simple expression of the form "literal".join(["...", "..."]).

• tox.ini: if present, it's expected to have

  [tox]
  envlist = pyXY, ...
  

  Environment names like pyXY-ZZZ are also accepted; the suffix is ignored.

• .travis.yml: if present, it's expected to have

  python:
    - X.Y
    - ...
  

  and/or

  matrix:
    include:
      - python: X.Y
        ...
      - ...
  

  and/or

  jobs:
    include:
      - python: X.Y
        ...
      - ...
  

  and/or

  env:
    - TOXENV=...
  

  (but not all of these forms are supported for updates)

• appveyor.yml: if present, it's expected to have

  environment:
    matrix:
      - PYTHON: C:\\PythonX.Y
      - ...
  

  The environment variable name is assumed to be PYTHON (case-insensitive). The values should be one of

  • X.Y
  • C:\\PythonX.Y (case-insensitive)
  • C:\\PythonX.Y-x64 (case-insensitive)

  Alternatively, you can use TOXENV with the usual values (pyXY).

  (TOXENV is currently not supported for updates.)

• .manylinux-install.sh: if present, it's expected to contain a loop like

  for PYBIN in /opt/python/*/bin; do
      if [[ "${PYBIN}" == *"cp27"* ]] || \
         [[ "${PYBIN}" == *"cp35"* ]] || \
         [[ "${PYBIN}" == *"cp36"* ]] || \
         [[ "${PYBIN}" == *"cp37"* ]] || \
         [[ "${PYBIN}" == *"cp38"* ]]; then
          "${PYBIN}/pip" install -e /io/
          "${PYBIN}/pip" wheel /io/ -w wheelhouse/
             rm -rf /io/build /io/*.egg-info
      fi
  done
  

  check-python-versions will look for $PYBIN tests of the form

  [[ "${PYBIN}" == *"cpXY"* ]]
  

  where X and Y are arbitrary digits.

  These scripts are used in several zopefoundation repositories like zopefoundation/zope.interface. It's the least standartized format.

• .github/workflows/*.yml: if present, it's expected to have

  jobs:
    (anything):
      strategy:
        matrix:
          python-version:
            - X.Y
            - ...
  

  or

  jobs:
    (anything):
      strategy:
        matrix:
          config
            - [ X.Y, "pyXY" ]
            - ...
  

Python versions

In addition to CPython X.Y, check-python-versions will recognize PyPy and PyPy3 in some of the files:

• setup.py may have a

  'Programming Language :: Python :: Implementation :: PyPy',
  

  classifier

• tox.ini may have pypy[-suffix] and pypy3[-suffix] environments

• .travis.yml may have pypy and pypy3 jobs with optional version suffixes (e.g. pypy2.7-6.0.0, pypy3.5-6.0.0)

• .github/workflows/*.yml: may have pypy/pypy3/pypy-N.M/pypy-N.M-vX.Y.Z jobs.

• appveyor.yml and .manylinux-install.sh do not usually have pypy tests, so check-python-versions cannot recognize them, and these files are excluded from PyPy support consistency checks.

Upcoming Python releases (such as 3.10 in setup.py or 3.10-dev in a .travis.yml) are also shown but do not cause mismatch errors.

In addition, python_requires in setup.py usually has a lower limit, but no upper limit. check-python-versions will assume this means support up to whatever's the latest Python 3.x release mentioned in other data sources, or the current 3.x release (3.10 at the moment), whichever is lower. This means that new Python 3 releases don't suddenly cause all your lint checks to fail if you use python_requires '>= 3.6' and such.

When you're specifying Python version ranges for --expect, --add, --drop or --update, you can use

• X.Y (e.g. --add 3.8)
• X.Y-U.V for an inclusive range (e.g. --add 3.5-3.8)
• X.Y-, which means from X.Y until the latest known release from the X series (e.g. --add 3.5- is equivalent to --add 3.5-3.7)
• -X.Y, which is the same as X.0-X.Y (e.g. --drop -3.4 is equivalent to --drop 3.0-3.4)

or a comma-separated list of the above (e.g. --expect 2.7,3.5-, --drop -2.6,-3.4).

--expect/--add/--drop/--update currently do not allow specifying alternative implementations (such as pypy).

pre-commit integration

With pre-commit, check-python-versions can be part of your git-workflow. Add the following snippet to your .pre-commit-config.yaml.

repos:
-   repo: https://github.com/mgedmin/check-python-versions
    rev: "0.20.0"
    hooks:
    -   id: check-python-versions