[Numpy-discussion] Proposal of timeline for dropping Python 2.7 support

[Nathaniel Smith]

On Nov 8, 2017 16:51, "Matthew Brett" <matthew.brett at gmail.com> wrote:

Hi,

On Wed, Nov 8, 2017 at 7:08 PM, Julian Taylor
<jtaylor.debian at googlemail.com> wrote:
> On 06.11.2017 11:10, Ralf Gommers wrote:
>>
>>
>> On Mon, Nov 6, 2017 at 7:25 AM, Charles R Harris
>> <charlesr.harris at gmail.com <mailto:charlesr.harris at gmail.com>> wrote:
>>
>>     Hi All,
>>
>>     Thought I'd toss this out there. I'm tending towards better sooner
>>     than later in dropping Python 2.7 support as we are starting to run
>>     up against places where we would like to use Python 3 features. That
>>     is particularly true on Windows where the 2.7 compiler is really old
>>     and lacks C99 compatibility.
>>
>>
>> This is probably the most pressing reason to drop 2.7 support. We seem
>> to be expending a lot of effort lately on this stuff. I was previously
>> advocating being more conservative than the timeline you now propose,
>> but this is the pain point that I think gets me over the line.
>
>
> Would dropping python2 support for windows earlier than the other
> platforms a reasonable approach?
> I am not a big fan of to dropping python2 support before 2020, but I
> have no issue with dropping python2 support on windows earlier as it is
> our largest pain point.

I wonder about this too.  I can imagine there are a reasonable number
of people using older Linux distributions on which they cannot upgrade
to a recent Python 3,


My impression is that this is increasingly rare, actually. I believe RHEL
is still shipping 2.6 by default, which we've already dropped support for,
and if you want RH python then they provide supported 2.7 and 3.latest
through exactly the same channels. Ubuntu 14.04 is end-of-life in April
2019, so pretty irrelevant if we're talking about 2019 for dropping
support, and 16.04 ships with 3.5. Plus with docker, conda, PPAs, etc.,
getting a recent python is easier than its ever been.

> but

is that likely to be true for Windows?

We'd have to make sure we could persuade pypi to give the older
version for Windows, by default - I don't know if that is possible.


Currently it's not – if pip doesn't see a Windows wheel, it'll try
downloading and building an sdist. There's a mechanism for sdists to
declare what version of python they support but (thanks to the jupyter
folks for implementing this), but that's all. The effect is that if we
release a version that drops support for py2 entirely, then 'pip install'
on py2 will continue to work and give the last supported version, but if we
release a version that drops py2 on Windows but keeps it on other platforms
then 'pip install' on py2 on Windows will just stop working entirely.

This is possible to fix – it's just software – but I'm not volunteering...

-n
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