[Pulp-dev] Proposal to drop support of Python 3.5 for Pulp 3

[Brian Bouterse]

I'm also +1 on this for the various reasons. Even with the portability
downsides. Also, practically speaking, the batch code is legit, and it will
benfit the stages code a lot.

On Fri, Sep 7, 2018 at 8:17 AM, Daniel Alley <dalley at redhat.com> wrote:

> Personally, +1.  I ran into this issue myself and it was infuriating to
> deal with.
>
> dict objects preserve insertion-order (officially declared part of
>>   the language with Python 3.7). Eliminates a source of subtle
>>   "works on 3.6, sometimes works on 3.5" bugs.
>>
>
> Just to expand on this though:
>
> For Ubuntu, it is part of 18.04 LTS. Debian does not have Python 3.6 in
>> stable yet.
>>
>
> It does mean that we won't be able to support Ubuntu 16.04 (or previous)
> or Debian at all until the next release (~May 2019), unless they install a
> newer Python themselves.
>
> On Fri, Sep 7, 2018 at 2:09 AM, Simon Baatz <gmbnomis at gmail.com> wrote:
>
>> I had a discussion on IRC with Brian yesterday which led to the
>> question whether we can drop support for Python 3.5. I think there are
>> good reasons for this, see the rationale below.
>>
>> Brian proposed to initiate a vote on this topic (and find out whether
>> this "community thing" works :-) ).
>>
>> Please send feedback by Friday Sept 14th. Especially, let me know if
>> there are specific reasons for depending on Python 3.5. The
>> corresponding issue is 3984 [7].
>>
>> Cheers,
>> Simon
>>
>>
>> Rationale:
>>
>> The trigger for the discussion was to get rid of boilerplate code like
>> this [0], [1] to handle batches in the stages API. This becomes a
>> single line [2] when using an asynchronous generator [3]. Adding the
>> `batches()` async generator to Pulp core would simplify existing
>> stages and ease implementation of stages in plugins.
>>
>> Async generators have been introduced in Python 3.6. Thus, to make the
>> `batches` generator available in the Pulp core plugin API, we either
>>
>> - have to drop support for Python 3.5 or
>>
>> - reimplement the async generator as an async iterator (which would be
>>   more convoluted but looks doable)
>>
>>
>> I prefer to drop 3.5, since this will allow to use additional language
>> features[4]. Among them:
>>
>> - As said, async generators/async comprehensions. Async generators are
>>   simpler to write and understand than async iterators.
>>
>> - String interpolation "f-Strings" [5]
>>
>> - dict objects preserve insertion-order (officially declared part of
>>   the language with Python 3.7). Eliminates a source of subtle
>>   "works on 3.6, sometimes works on 3.5" bugs.
>>
>> - One version less to support is always a good thing (provided nobody
>>   really requires it)
>>
>> - Type annotations are currently not used by the Pulp project, but if
>>   the project decides to use them in the future: IMHO type annotations
>>   (which are great btw.) began to feel “right† with 3.6. Working with
>>   them in 3.5 can be clumsy at times.
>>
>> - And of course: [6]
>>
>>
>> Python 3.6 has the OS/distribution support we need:
>>
>> - Python 3.6 SCL is available for RHEL 7 / CentOS 7
>> - It is part of Fedora as of Fedora 26
>>
>> For Ubuntu, it is part of 18.04 LTS. Debian does not have Python 3.6 in
>> stable yet.
>>
>>
>>
>> [0] https://github.com/pulp/pulp/blob/631031e38270c5c7c2b2289ff4
>> ab87a058447c5e/plugin/pulpcore/plugin/stages/
>> content_unit_stages.py#L47-L59
>> [1] https://github.com/pulp/pulp/blob/631031e38270c5c7c2b2289ff4
>> ab87a058447c5e/plugin/pulpcore/plugin/stages/artifact_stages.py#L48-L60
>> [2] https://github.com/gmbnomis/pulp_cookbook/blob/ca4882cecab16
>> 995c5713d27131da8112a5f5a0c/pulp_cookbook/app/tasks/synchronizing.py#L98
>> [3] https://github.com/gmbnomis/pulp_cookbook/blob/d44ed593925b7
>> 8c046e1b568810b15acbdad5ac4/pulp_cookbook/app/tasks/synchronizing.py#L26
>> [4] https://docs.python.org/3/whatsnew/3.6.html
>> [5] https://docs.python.org/3/whatsnew/3.6.html#pep-498-formatte
>> d-string-literals
>> [6] https://twitter.com/raymondh/status/844955415259463681
>> [7] https://pulp.plan.io/issues/3984
>>
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>
>
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