[Python-Dev] Language Summit Follow-Up

[Guido van Rossum]

Right. The point is that the current HOWTO gives information that is not
useful for most people who are tasked with a port.


On Fri, May 30, 2014 at 6:46 PM, Nick Coghlan <ncoghlan at gmail.com> wrote:

>
> On 31 May 2014 08:42, "Guido van Rossum" <guido at python.org> wrote:
> >
> > 2to3 is poorly named. With different fixers it is a fine tool for
> converting 2-only code to 2-and-3 straddling code. Even when using six, you
> need to do things like convert print statements to print() calls with
> future import, use 'as' in except clauses, and so on.
>
> Both modernize & futurize build on lib2to3 to do the heavy lifting - they
> don't reinvent that wheel, they just change which fixes are applied by
> default and add a few more of their own.
>
> However, even if going straight to Python 3, I suspect folks would still
> be better off doing something like:
>
> * futurize --stage1 (migrates to 2.6+, but adds no new runtime
> dependencies - the output should be fairly idiomatic Python 2.6/7 code)
> * 2to3 (wholesale migration to Python 3)
>
> The trick, though, is that the granularity of that approach is at the
> process level - the entire application must be converted at once. You also
> can't start your own migration until all your dependencies are available in
> Python 3.
>
> By contrast, migration via the common subset can be incremental and
> opportunistic:
>
> * the granularity of migration is individual modules, rather than entire
> processes, so you can make a low risk gradual transition, even without a
> comprehensive regression test suite
> * you initially stay on Python 2, so you can start whenever is convenient
> for you, rather than having to wait for all your dependencies
>
> Cheers,
> Nick.
>
> >
> >
> > On Fri, May 30, 2014 at 1:47 PM, Antoine Pitrou <solipsis at pitrou.net>
> wrote:
> >>
> >> On Wed, 28 May 2014 15:26:38 -0700
> >> Glyph Lefkowitz <glyph at twistedmatrix.com> wrote:
> >> > Backport 'yield from' to allow people to use Tulip and
> Tulip-compatible code, and to facilitate the development of Tulip-friendly
> libraries and a Tulip ecosystem.  A robust Tulip ecosystem requires the
> participation of people who are not yet using Python 3.
> >>
> >> I was wondering whether you were trolling or not on this one.
> >> From a quality assurance point of view, adding major features to a
> >> bugfix branch is extremely destructive, so I'm strongly -1 on it.
> >>
> >> > Get rid of 2to3. Particularly, of any discussion of using 2to3 in the
> documentation.  More than one very experienced, well-known Python developer
> in this discussion has told me that they thought 2to3 was the blessed way
> to port their code, and it's no surprise that they think so, given that the
> first technique <https://docs.python.org/3/howto/pyporting.html> mentions
> is still 2to3.
> >>
> >> 2to3 is certainly fine if you are porting to 3.x without looking to
> >> keep your code 2.x-compatible. Until there's a better alternative, of
> >> course.
> >> So what we should do is better explain the choice (if you want to port
> >> your code to 3.x, use 2to3; if you want to maintain dual-compatible
> >> code, use six or something similar).
> >>
> >> Regards
> >>
> >> Antoine.
> >>
> >>
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> >
> >
> >
> >
> > --
> > --Guido van Rossum (python.org/~guido)
> >
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> >
>
>


-- 
--Guido van Rossum (python.org/~guido)
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