[yt-dev] Starting conversation about Py2 deprecation

Thu Apr 20 15:03:51 PDT 2017

On Thu, Apr 20, 2017 at 4:58 PM, Nathan Goldbaum <nathan12343 at gmail.com>
wrote:

> If we do drop Python2 support, I'd prefer to do it fully and not
> intentionally leave in six and all of the code that's conditional on Python
> version. Leaving in the shim code makes the codebase harder to understand,
> so we should take the opportunity to remove it once we have the chance to
> make it more approachable and maintainable. In addition, I don't feel
> comfortable letting people install yt on a version of python that we're
> intentionally not testing. There should just eventually be a yt version
> that isn't installable on python2. We will of course need to communicate
> with out community about that, and announce the transition well ahead of
> time. Thankfully we are in good company on these announcements, and many
> other packages (notably IPython) have begun to make their own transitions
> to python3-only codebases.
>
> Up until now we've tried to avoid having too many breaking changes, and it
> just so happens that we're thinking about how to handle two of them. The
> first is the stuff that we want to go into yt 4.0 (non-spatial domains and
> the demeshening) and the second is dropping Python3. I guess we're most
> efficient in spending breaking change chits with our userbase if we group
> these two changes together. Ideally we'd do that, but several people on the
> call yesterday objected to that but at the same time seemed amenable to the
> compromise that we drop python3 support soon after releasing a version of
> yt that includes the demeshening and non-spatial domains. So that means
> dropping python3 support needs to happen after yt 4.0.
>
> I think Matt would prefer not to to a yt 5.0 release soon after yt 4.0.
> However, as Mike points out, dropping python3 support is a breaking change
> for some people, so we probably need to indicate that in the version
> number. Taken together, I think that means we need to do both a yt 4.0 and
> yt 5.0 release.
>
> So that means we need to decide now how long we want the delay between
> releasing yt 4.0 and dropping python3 support in yt 5.0 is going to be. Are
> we going to release yt 4.1 with new features but still supporting python2?
> Or are we going to move straight to yt 5.0, possibly supporting yt 4.0 with
> bugfixes for an extended period. Our messaging here I think depends on what
> the timeline should be.
>
> If we want to drop python2 support in 2018, I think there should be a yt
> 4.1.
>

Sorry, typo, I meant to write I *don't* think there should be a 4.1

> If we want to drop it in 2019 or 2020, then we have plenty of time to
> accumulate other ideas for breaking changes that we want to include in yt
> 5.0 and we might end up doing yt 4.1 and 4.2 releases.
>
> Personally, I'm leaning towards dropping Python2 support sooner, in 2018.
> Would anyone prefer a later switch?
>
> On Thu, Apr 20, 2017 at 4:31 PM, Nathan Goldbaum <nathan12343 at gmail.com>
> wrote:
>
>> I guess it doesn't matter much whether we call it 4.1 or 5.0. We could
>> commit ahead of time that the only major breaking change in 5.0 would be
>> dropping python2 support.
>>
>> On Thu, Apr 20, 2017 at 4:29 PM, John Zuhone <jzuhone at gmail.com> wrote:
>>
>>> We had a conversation about this point yesterday, in fact I was the one
>>> that brought this point up.
>>>
>>> Though in my mind I agree with you at first that it makes more sense to
>>> do this at 4.0, there are two reasons why we should wait until 4.1:
>>>
>>> 1. gives users more time to prepare
>>> 2. gives python 2 people a chance to use the new features (especially
>>> demeshening) at least for one 4.x version
>>>
>>> On Apr 20, 2017, at 5:27 PM, Michael Zingale <
>>> michael.zingale at stonybrook.edu> wrote:
>>>
>>> my thought on this is that removing python 2 support should occur on a
>>> major release, not a point release.  It seems odd that yt 4.0 supports both
>>> 2 and 3, but 4.1 drops python 2 support.  Might be confusing for users.
>>>
>>> On Thu, Apr 20, 2017 at 4:27 PM, Matthew Turk <matthewturk at gmail.com>
>>> wrote:
>>>
>>>> Hi folks,
>>>>
>>>> On the call yesterday, the topic of dropping support for Py2 came up.
>>>> This site provides some context:
>>>>
>>>> http://www.python3statement.org/
>>>>
>>>> At present, we're planning to have a 3.4 release sometime in the early
>>>> summer, and then aiming for a yt 4.0 sometime about six months later.  yt
>>>> 4.0 will have the demeshening.
>>>>
>>>> A proposal was floated to have yt 4.0 be the last release that
>>>> explicitly supports python 2, and then to "softly" drop support for python
>>>> 2 during the cycle for yt 4.1, which would be about six months later, we
>>>> anticipate.  This would mean not testing on py2 anymore and potentially
>>>> removing some of the shims and six calls to dual-support.
>>>>
>>>> Some more discussion is in the meeting notes:
>>>>
>>>> https://github.com/yt-project/meeting-notes/blob/master/note
>>>> s-20170419.md
>>>>
>>>> I don't know if this is something we should actively discuss yet, but I
>>>> wanted to put it out there.  I personally support this proposal.
>>>>
>>>> -Matt
>>>>
>>>> _______________________________________________
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>>>>
>>>>
>>>
>>>
>>> --
>>> Michael Zingale
>>> Associate Professor
>>>
>>> Dept. of Physics & Astronomy • Stony Brook University • Stony Brook, NY
>>> 11794-3800
>>> *phone*:  631-632-8225 <(631)%20632-8225>
>>> *e-mail*: Michael.Zingale at stonybrook.edu
>>> *web*: http://www.astro.sunysb.edu/mzingale
>>> github: http://github.com/zingale
>>>
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>>
>
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