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

[Stefan van der Walt]

On Fri, Nov 17, 2017, at 13:12, Chris Barker wrote:
> On Fri, Nov 17, 2017 at 4:35 AM, Peter Cock
> <p.j.a.cock at googlemail.com> wrote:>> Since Konrad Hinsen no longer follows the NumPy discussion list
>>  for lack of time, he has not posted here - but he has commented
>>  about this on Twitter and written up a good blog post:
>> 
>> http://blog.khinsen.net/posts/2017/11/16/a-plea-for-stability-in-the-scipy-ecosystem/
I don't agree with the general gist of Konrad's post.  There are
multiple viewpoints on the issue, of course, such as that of developers
that are already invested in NumPy or SciPy's APIs, those that will rely
on it in the future, and those that are still undecided about whether to
use these tools.
For those heavily invested such as Konrad, API changes and a language
upgrade may seem like a particularly bad situation.  Heck, none of us
enjoyed having to port all of our code to Python 3, but in reality the
changes required were much fewer than commonly imagined and are
documented.
But in the same way you cause some pain by changing APIs, *not* changing
APIs carries a penalty too, more for the other groups I mentioned.  The
ability to change APIs, albeit slowly, allows cleaner and more intuitive
future code, fewer surprises, and makes the environment much more
enjoyable to use.
We can do a better job of advertising NumPy's deprecation policy.  A
quick Google search for "x deprecation policy" didn't manage to find it,
but did pick up:
- http://scikit-learn.org/stable/developers/contributing.html#deprecation
- http://scikit-image.org/docs/dev/contribute.html#deprecation-cycle
- https://docs.scipy.org/doc/scipy-1.0.0/reference/dev/deprecations.html
All the above packages, as well as NumPy, include a section on API
changes in their release notes.
We may benefit from standardizing deprecation conventions across the
community, so that there is a very clear expectation on how often to run
your code to be able to see all relevant  warnings and fix them.
Best regards
Stéfan

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