On Sat, Apr 15, 2017 at 5:19 PM, Nathaniel Smith <njs@pobox.com> wrote:On Fri, Apr 14, 2017 at 5:19 PM, Charles R Harris
<charlesr.harris@gmail.com> wrote:
> Hi All,
>
> It may be early to discuss dropping support for Python 2.7, but there is a
> disturbance in the force that suggests that it might be worth looking
> forward to the year 2020 when Python itself will drop support for 2.7. There
> is also a website, http://www.python3statement.org , where several projects
> in the scientific python stack have pledged to be Python 2.7 free by that
> date. Given that, a preliminary discussion of the subject might be
> interesting, if only to gather information of where the community currently
> stands.
One reasonable position would that numpy releases that happen while
2.7 is supported upstream will also support 2.7, and releases after
that won't.
>From numpy's perspective, I feel like the most important reason to
continue supporting 2.7 is our ability to convince people to keep
upgrading. (Not the only reason, but the most important.) What I mean
is: if we dropped 2.7 support tomorrow then it wouldn't actually make
numpy unavailable on python 2.7; it would just mean that lots of users
stayed at 1.12 indefinitely. Which is awkward, but it wouldn't be the
end of the world – numpy is mature software and 1.12 works pretty
well. The big problem IMO would be if this then meant that lots of
downstream projects felt that they had to continue supporting 1.12
going forward, which makes it very difficult for us to effectively
ship new features or even bug fixes – I mean, we can ship them, but
no-one will use them. And if a downstream project finds a bug in numpy
and can't upgrade numpy, then the tendency is to work around it
instead of reporting it upstream. I think this is the main thing we
want to avoid.
+1
This kind of means that we're at the mercy of downstream projects,
though – if scipy/pandas/etc. decide they want to support 2.7 until
2022, it might be in our best interest to do the same. But there's a
collective action problem here: we want to keep supporting 2.7 so long
as they do, but at the same time they may feel they need to keep
supporting 2.7 as long as we do. And all of us would prefer to drop
2.7 support sooner rather than later, but we might all get stuckbecause we're waiting for someone else to move first.I don't quite agree about being stuck. These kind of upgrades should and usually do go top of stack to bottom. Something like Jupyter which is mostly an end user tool goes first (they announced 2020 quite a while ago), domain specific packages go at a similar time, then scipy & co, and only after that numpy. Cython will be even later I'm sure - it still supports Python 2.6.
So my suggestion would be that numpy make some official announcement
that our plan is to drop support for python 2 immediately after
cpython upstream does.Not quite sure CPython schedule is relevant - important bug fixes haven't been making it into 2.7 for a very long time now, so the only change is the rare security patch.
If worst comes to worst we can always decide to
extend it at the time... but if we make the announcement now, then
it's less likely that we'll need to :-).I'd be in favor of putting out a schedule in coordination with scipy/pandas/etc, but it probably should look more like- 2020: what's on http://www.python3statement.org/ now- 2021: scipy / pandas / scikit-learn / etc.- 2022: numpy