[yt-dev] Starting conversation about Py2 deprecation

Fri Apr 21 16:25:01 PDT 2017

As I mentioned during the meeting, I like the idea of having some sort of
long term support for the release prior to the switch, so that people have
the choice of continuing to use a version of yt with python 2.x support
before having the rug pulled out from under them in a few months.  I
realize that this is not a trivial thing to do, though, so I'm flexible.

Cameron

On Fri, Apr 21, 2017 at 10:40 AM, Britton Smith <brittonsmith at gmail.com>
wrote:

> Sometime in 2018 sounds like a very reasonable time for dropping python2.7
> support.  What is most important to me is giving the users enough warning
> and time to switch before this happens.  It matter less to me what type of
> release it happens on.
>
> The 4.0 release will be hugely beneficial for so many people (specifically
> for it's improved SPH support) that I think it's important that we maintain
> python2 support until then.  I think it's the kinder thing to do than to
> make 4.0 the carrot offered for switching to python3.  I'm also guessing
> that everything that's being developed for 4.0 still works with python2, so
> we might as well keep that up until the release.
>
> I think the 3.4 release will be a good opportunity to announce that there
> is a timeline for dropping python2 support, and specifically to say that
> there will only be one more release and then python2 is gone.  Then, 4.0
> comes out and we say this is it, time to switch.
>
> My two cents!  Time to board a flight!
>
> On Thu, Apr 20, 2017 at 3:03 PM, Nathan Goldbaum <nathan12343 at gmail.com>
> wrote:
>
>>
>>
>> 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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>>>>>
>>>>>
>>>>
>>>
>>
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-- 
Cameron Hummels
NSF Postdoctoral Fellow
Department of Astronomy
California Institute of Technology
http://chummels.org
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