[Python-Dev] Proposed 3.0 compatiblity module (original) (raw)

Guido van Rossum guido at python.org
Wed Jan 17 00🔞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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