[Python-Dev] PEP 4000 to explicitly declare we won't be doing a Py3k style compatibility break again?

Łukasz Langa lukasz at langa.pl
Sun Aug 17 04:46:45 CEST 2014

On Aug 16, 2014, at 6:28 PM, Nick Coghlan <ncoghlan at gmail.com> wrote:

> I've seen a few people on python-ideas express the assumption that
> there will be another Py3k style compatibility break for Python 4.0.

Whenever I mention Python 4 or PEP 4000, it’s always a joke. However, saying upfront that we will never break compatibility is a bold statement. Technically even introducing new syntax breaks compatibility. Not to mention fixing long-lasting bugs. So you’d need to split hairs just defining what we mean by a “major compatibility break”.

Worse, if we ever did a change that we feel is within the bounds of the contract, you’d have someone pointing at that PEP saying that they feel we broke the contract. Splitting hairs again.

PEP 404 was necessary for some people/organizations to move on. I fail to see how PEP 4000 (or rather PEP 4004? ;-)) would be useful in that context.

Best regards,
Łukasz Langa

WWW: http://lukasz.langa.pl/
Twitter: @llanga
IRC: ambv on #python-dev
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