[Cython] Should Cython 3.0 still have Python 2.x support?

[Stefan Behnel]

[CC-ing cython-devel, but please keep the discussion on cython-users]

Hi all,

we were recently asked on the bug tracker [1] when Cython is planning to
end its support for Python 2.x, so I'd like to get some more user opinions
on this.

We are planning to release Cython 3.0 this year [2], with some well
selected backwards incompatible changes and a tiny bit of feature
reduction, so … wouldn't that be a good time to cut off even more of the
old cruft? Should we really have a release that supports the CPython
versions 3.8 (~October) all the way back to 2.7? Or would Python 2.7-3.7 be
enough in 0.29, and only Python 3.[345]-3.8+ for Cython 3.0? (*)

Remember, removing legacy support as part of a new release doesn't change
anything about the old releases, so they will still keep working for
everyone who wants Python 2.x support, even long after January 1st, 2020.
As I wrote in the ticket, I would not object to anyone backporting fixes to
0.29 that we implement for newer releases, and continuing with point
releases for it whenever there is something to release in the legacy
maintenance branch. (And as long as there aren't any breaking changes in
Py3.8, 0.29.x might also work there.)

What do you think?

Stefan



[1] https://github.com/cython/cython/issues/2800

[2] https://github.com/cython/cython/milestone/58

(*) We currently support Py3.3+ for Py3. Py3.4 is expected to reach its EOL
in March, but still seems worth supporting for another while. Not sure
about 3.3, probably an "as long as it doesn't hurt" case.