Re: Python 3, was Re: ANN: Frescobaldi 2.19.0

[address@hidden]

How much python code are we talking about within the complete LilyPond project? The discussion until now seems to be a discussion about Python2/3 transitions in general. But maybe the situation isn't that bad. Many python syntax can be compatible with both Python2 and Python3 without much effort. There are in practice only a few things that are a bit harder. For example strings/unicode/binary datatypes. If it's only a limited amount of old code that requires some effort to make it compatible with both Py2 and Py3 than that might be worth considering. Writing new code using a common subset isn't that difficult. That's where the six library can help.


MT

-------- Oorspronkelijk bericht --------
Onderwerp: Re: Python 3, was Re: ANN: Frescobaldi 2.19.0
Van: David Kastrup
Aan: Werner LEMBERG
Cc: address@hidden

Werner LEMBERG writes:

>> So far we only have an offer for a hard and incompatible transition
>> to Python3-only
>
> Actually, I dislike this. Similar to you, I don't see a convincing
> reason to not write python code that is compatible with both version 2
> and version 3.

Well, #!/usr/bin/guile can mean either Guile-1 and Guile-2 whereas
#!/usr/bin/python is more or less guaranteed to mean Python-2 for quite
a bit of time, even while there may be only Python-3 available at some
point of time.

So it does look like we are in for a hard change with regard to
distributed LilyPond versions anyway. However, the configure process
very well could substitute address@hidden@ (most installed scripts) as
well as address@hidden@ (the build scripts) with either a Python-2 or a
Python-3 hashbang, depending on availability/configuration of either
option.

So we definitely have a use case for supporting both: then a choice can
be made by scripts or user at configure time.

--
David Kastrup

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