drop support for python 2.7

[samuelcolvin]

It looks like cibuildwheel has a significant amount of logic dedicated to python 2.7.

Isn't it time to drop support for 2.7 and simplify the library?

[Czaki]

Being the last of the 2.x series, 2.7 will receive bugfix support until 2020. Support officially stops January 1 2020, but the final release will occur after that date.

Planned future release dates:

2.7.18 code freeze January, 2020
2.7.18 release candidate early April, 2020
2.7.18 mid-April, 2020

from https://www.python.org/dev/peps/pep-0373/

[samuelcolvin]

humm, so when would you suggest cibuildwheel can drop 2.7 support?

Many other libraries have already dropped python 2 and rely on prior releases for those still (inexplicably) using python 2.7.

[YannickJadoul]

Personally, I think it would be nice to have one final Python 2.7 compatible release with the current merged PRs and some of the pending ones.

Note also that PyPy (which we'll support soon: #185) won't drop 2.7 support (since large parts of their toolchain are built upon the 2.7 version of the language), so I'm not sure we can remove all the code that relates to 2.7.

[Czaki]

I agree. Also there is Tauthon which may be supported in future.

[YannickJadoul]

Urgh, "Tauthon"; what a silly pun :-D

EDIT: It might depend a bit on how widely it will be used. I'm not a big fan of adding a compilation step for Tauthon in cibuildwheel.

[Czaki]

Adding Thauton is an option only if they provide bundled version for all systems. Not when it need to be compiled from source.

[joerick]

Thanks for raising this @samuelcolvin!

I'd be open to supporting Python 2 wheels for a little while longer, but curious to opinions.

I had thought that we'd get a good, stable release of cibuildwheel out, and then would refer anyone who needs Python 2 support to that version. But... now that I think about it, it would be good to get deterministic builds #239 in before this! At some point, that pinned version of cibuildwheel will be pulling in dependencies that don't support or are buggy on Python 2, for example, the manylinux images, setuptools, or virtualenv.

However we could definitely remove Python 2 support for running cibuildwheel itself now, I think it's totally fine to require it on the build machine.

edit: @YannickJadoul's point on PyPy 2.7 is a good one - we won't be dropping support for that Python 2.7 - it's still actively maintained.

[jtrmal]

For what it is worth coming from someone just passing by, Py 2.7 won't disappear in two weeks. There will still be (IMO) maintainers, especially in the LTS distributions. So my opinion is to support Py2.7 as long as (reasonably) feasible.

[YannickJadoul]

I'd very happily drop the support for running cibuildwheel with Python 2, though; any thoughts on that?

It would reduce the amount of tests to run, and avoid annoyances like this: https://circleci.com/gh/joerick/cibuildwheel/3212

[jtrmal]

yeah, that makes sense to me. In our projects, we stopped accepting py2 code and enforce py3 for new addition.

[joerick]

I'd very happily drop the support for running cibuildwheel with Python 2, though; any thoughts on that?

Agreed. Will reduce code clutter, and reduce CI load. Let's do it.

[YannickJadoul]

Agreed. Will reduce code clutter, and reduce CI load. Let's do it.

Yesssss; working on it!

[joerick]

Wishlist for the Python 3 modernisation:

• remove run_docker in linux.py (replace with subprocess.run)
• removing these:

  try:
      from urllib.request import urlopen
  except ImportError:
      from urllib2 import urlopen

• consider using f-strings for the bash script in linux.py (?)

[Czaki]

add type annotation?

consider using f-strings for the bash script in linux.py (?)

It means also drop for running on python 3.5?

[samuelcolvin]

surely everyone running cibuildwheel has access to python 3.6 or above?

[YannickJadoul]

Wishlist for the Python 3 modernisation:

Great, thanks! I'll try to get that first PR ready soon, so we can all have a further look at what can be better.

surely everyone running cibuildwheel has access to python 3.6 or above?

Python 3.5 is still officially supported, so I don't want to blame people for still using it.

[samuelcolvin]

perhaps.

Another big gain would be using pathlib instead of all the os.path.*. I think this was why I originally suggested dropping python 2.

[Czaki]

@YannickJadoul Maybe wait with this PR since #185 is merged. These changes will be big.

[joerick]

Another big gain would be using pathlib instead of all the os.path.*. I think this was why I originally suggested dropping python 2.

Interesting suggestion - I've not had much experience with these path objects. How do they work when using them with subprocess.run() for example? My experience has been the need to throw str(path) all over the place, but I might have been using it wrong.

[YannickJadoul]

Another big gain would be using pathlib instead of all the os.path.*. I think this was why I originally suggested dropping python 2.

Ah, yes, thanks for the suggestion!

@YannickJadoul Maybe wait with this PR since #185 is merged. These changes will be big.

Ugh, it's true, yes :-/ Would you have some time to look at #185, maybe, @Czaki, just to check if the rebase on top of #156 and #220 (which caused lots of merge conflicts) are not too bad?

[samuelcolvin]

How do they work when using them with subprocess.run() for example?

Unfortunately not perfectly, i think here and elsewhere you do need str()

However that's more than made up for with .isfile() etc. and join using the / operator.

[Czaki]

@YannickJadoul I do not understand your request. Can you wrote it another way?

[YannickJadoul]

@YannickJadoul I do not understand your request. Can you wrote it another way?

I meant to ask if you have time to review #185, maybe. I needed to rebase it two times, after #156 and #220. And it was a big rebase, these two times, with lots of merge conflicts. So maybe I you would still find some mistakes?

[Czaki]

I left some comments. I do not see any important problem.

[YannickJadoul]

if anyone else here wants to have a look and find things @joerick, @Czaki, and I haven't thought of yet in #265, feel free to let us know! Except for f-strings (I'd love them, but I'd argue that's only in after 3.5 gets dropped) and type annotations (that's another discussion, #258), that is.

[YannickJadoul]

Oh, pathlib. I should still have a look at that, yes!

[Czaki]

Due to pathlib i would rather modify shell/call function to check arguments and convert to string than use str everywhere.

[YannickJadoul]

See #265 (comment)

I argue against pathlib until we can drop 3.5.

[Czaki]

This what I think is to change ex.:

    def call(args, env=None, cwd=None, shell=False):
        # print the command executing for the logs
        if shell:
            print('+ %s' % args)
        else:
            print('+ ' + ' '.join(shlex.quote(a) for a in args))

        return subprocess.check_call(args, env=env, cwd=cwd, shell=shell)

to

    def call(args, env=None, cwd=None, shell=False):
        # print the command executing for the logs
        args = [str(x) if isinstance(x, pathlib.Path) else x for x in args]
        if shell:
            print('+ %s' % args)
        else:
            print('+ ' + ' '.join(shlex.quote(a) for a in args))

        return subprocess.check_call(args, env=env, cwd=cwd, shell=shell)

[YannickJadoul]

This what I think is to change ex.:

I know. But it is not enough. shutil.rmtree, os.chdir, ... also all cannot take pathlib.Path arguments in Python 3.5, because PEP 519 is only implemented from Python 3.6 onwards. Believe me, I tried for half an hour, yesterday; it's really more than just that function.

[joerick]

We have dropped support for Python 2.7 on the host side. For the moment, we'll continue to support building CPython 2.7 wheels, though I expect we'll stop supporting that in a future release at some point this year.

[Czaki]

There is any reason to drop support to build cPython 2.7 build if there is plan to support pypy 2.7?

[EricCousineau-TRI]

Note also that PyPy [...] won't drop 2.7 support (since large parts of their toolchain are built upon the 2.7 version of the language) [...]

Reference contributed by the peanut gallery (me): https://doc.pypy.org/en/latest/faq.html#how-long-will-pypy-support-python2

[YannickJadoul]

Note also that PyPy [...] won't drop 2.7 support (since large parts of their toolchain are built upon the 2.7 version of the language) [...]

Reference contributed by the peanut gallery (me): https://doc.pypy.org/en/latest/faq.html#how-long-will-pypy-support-python2

Yeah. There might be a point at which PyPy 2.7 itself is not really used anymore by users (if most code has become Python 3-targeted, because CPython 2 is dead), and when building library wheels for PyPy 2.7 becomes useless?