Python 3.10 / 4 checker?

[hugovk]

We don't yet know if 3.10 or 4.0 will follow Python 3.9, but great to see your tests with https://github.com/asottile/python3.10 and the related fixes!

• Fixes for python3.10 pypa/setuptools#1824
• Fix PythonSpec detection of python3.10 tox-dev/tox#1398
• future-proof .travis.yml for python 3.10 python/cpython#14831
• Fix PythonSpec detection of python3.10 tox-dev/tox#1398

How about a pre-commit hook to detect, and possibly fix, some potential 3.10 errors?

-sys.version[:3]
+'{}.{}'.format(*sys.version_info)

And also any possible Python 4 errors?

-if sys.version_info.major == 3:
+if sys.version_info.major >= 3:
    # Python 3+ stuff
else:
    # Python 2 stuff

Maybe this might not be something for pre-commit, but I think it could be a useful tool of some sort.

Thanks!

[asottile]

probably makes the most sense as a flake8 plugin? should be pretty easy to detect the various cases that are problematic:

• slice / index of sys.version
• usage of six.PY3
• usage of sys.version_info[0] ==
• etc.

[asottile]

I made flake8-2020 on stream today 🎉

[hugovk]

Brilliant, thanks!