[Python-ideas] Smoothing transition to Python 3

[Nikolaus Rath]

On Jun 09 2016, Carl Meyer <carl-faUO1KlGllLR7s880joybQ at public.gmane.org> wrote:
> On 06/09/2016 04:20 PM, Nick Coghlan wrote:
>> On 8 June 2016 at 00:34, Pavol Lisy <pavol.lisy-Re5JQEeQqe8AvxtiuMwx3w at public.gmane.org> wrote:
>>> 2016-06-05 7:14 GMT+02:00, Nick Coghlan <ncoghlan-Re5JQEeQqe8AvxtiuMwx3w at public.gmane.org>:
>>>
>>>> Red Hat's Python maintenance team are working on a more explicitly
>>>> minimalistic porting guide based on their experiences porting Fedora
>>>> components, sometimes in the context of upstream projects that are more
>>>> interested in keeping Python 2.4 support than they are in Python 3:
>>>> http://portingguide.readthedocs.io/en/latest/
>>>
>>> do you have some drafts how to write (new) code supporting python from
>>> 2.4 - 2.7 with intention to port it to python3 in future?
>> 
>> Unfortunately, the only practical solution we've found for that case
>> is to fork the code base until the maintainers of the original project
>> are willing to raise the minimum version requirement to Python 2.6:
>> http://portingguide.readthedocs.io/en/latest/process.html#drop-python-2-5-and-lower
>> 
>> While it's theoretically possible to support 2.4+ and 3.x in the same
>> code base, it's painful in practice due to the lack of the forward
>> compatibility features added in Python 2.6 (such as the Python 3 style
>> syntax for name binding in except clauses)
>
> While I agree that it's by far the best option to raise the minimum
> supported version to 2.6 (or even 2.7) before trying to straddle to 3,
> we shouldn't make it sound impossible to straddle all the way back to
> 2.4. It's painful, for sure, but every issue is surmountable if you're
> dedicated enough.

Sure, e.g. you could implement a Python 3 runtime in Python 2.4. It's
Turing-complete after all.

SCNR.

Best,
-Nikolaus
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