[Python-Dev] Proposed 3.0 compatiblity module

Guido van Rossum guido at python.org
Wed Jan 17 00:18:31 CET 2007


On 1/16/07, Phillip J. Eby <pje at telecommunity.com> wrote:
> At 08:52 PM 1/16/2007 +0000, Steve Holden wrote:
> >I foresee that many people would be happy restricting their 2.X source
> >slightly to ensure perfect translation into (working, no necessarily
> >optimal) 3.0. Under those circumstances the 2to3 tool wouldn't
> >necessarily have to translate all valid 2.X to 3.0.
>
> Actually, it would be several times more preferable to either have that
> restricted subset of code run on 3.0 without translation, or for translated
> code to still be usable in 2.X.
>
> I have often been in the habit of running test suites back-to-back on
> multiple versions of Python while doing test-driven development, so having
> a repeated translation step would interfere with that.  Ideally, a
> translation should be necessary one time only -- in which case requiring
> manual cleanup steps isn't as big of a problem.
>
> The idea here being that, once 2.6 is widely-enough deployed that it can be
> assumed as a base for one's users, you can simply run the translator once,
> do any cleanup, and then have 3.0-clean code that also still runs for your
> installed base.
>
> That way, there's no chasm to leap; just a code cleanup.

I understand; I would rather have that too, everything else being the
same. But everything else wouldn't be the same -- it would place many
more restrictions on 3.0, and the common subset would still be much
smaller. For me personally, the weight of the added restrictions to
3.0 is the killer.

-- 
--Guido van Rossum (home page: http://www.python.org/~guido/)


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