Re: Python 3

[David Kastrup]

Jonas Hahnfeld <address@hidden> writes:

> Am Samstag, den 21.09.2019, 11:25 +0200 schrieb David Kastrup:
>
>> I haven't checked yet, but at the current point of time, the best
>> patches will be those running under both Python 2 and Python 3 without
>> having to special-case code.  Those can be applied to master and thus
>> minimize the actual amount of code switching we ultimately need to do.
>
> I agree that this would be ideal, but pretty hard: Already the result
> of running 2to3 can't be executed under Python 2 in some cases or may
> start to give different results. Examples include
>  * "isinstance(s, unicode)" -> "isinstance(s, str)", which is something
> different in Python 2, and
>  * "import StringIO" -> "import io", which didn't have all functions in
> Python 2.
>
> If that is the way required to get Lilypond ported to Python 3, I can
> try to work into that direction. But finally, I guess there will need
> to be a hard switch to Python 3...

I think the principal problem is that I don't see us providing a GUB
installer with both Python2 and Python3 in it.  So code that does not
run in both will need to get switched over at the time we switch GUB
from Python2 to Python3.  If I remember correctly, this will be the time
that we definitely have to retire the PowerPC MacOSX version (it's not
clear anybody is actually using it, though).

-- 
David Kastrup