[Python-Dev] Proposed 3.0 compatiblity module

[Steve Holden]

Guido van Rossum wrote:
> On 1/12/07, Raymond Hettinger <raymond.hettinger at verizon.net> wrote:
[...]
>> Outside of a compatibility module, we can decide to leave Py2.6 unmolested by
>> Py3.0, so I can stop being cranky.
> 
> If you're feeling cranky this early in the new year, maybe you should
> look for reasons outside this list. :-)
> 
What, we're supposed to reset our crankometers on January 1? Nobody told 
me that.

> I'm all for striving for minimal impact. I don't think we can attain
> zero impact.
> 
> BTW, a possible alternative would be to strive for code that runs
> under 2.x, and *after automatic transformation using the 2to3 tool*
> runs under 3.x, *without mannual patch-up*. That's probably a much
> lower bar, and it would still mean that developers wishing to maintain
> code that works with both 2.x/3.x only need to maintain a single
> version -- the other version could be automatically generated.
> 
> Since you need to do a lot of testing anyways to make sure you haven't
> accidentally broken compatibility, the effort would be roughly
> equivalent to the "identical source" approach that people are
> advocating so far, and it would probably lift some restrictions.
> 
> For example, working around print becoming a function would mean no
> use of print at all when using "identical source"; but that's a
> transformation that the 2to3 tool can do trivially and perfectly, so
> the "automatic conversion" approach would enable freely using print
> statements.
> 
> A mixture of the two approaches would perhaps work best.
> 
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.

cranki-ly y'rs  - steve
-- 
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