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

Guido van Rossum guido at python.org
Mon Aug 18 03:02:18 CEST 2014

On Sun, Aug 17, 2014 at 6:29 AM, Barry Warsaw <barry at python.org> wrote:

> On Aug 16, 2014, at 07:43 PM, Guido van Rossum wrote:
> >(Don't understand this to mean that we should never deprecate things.
> >Deprecations will happen, they are necessary for the evolution of any
> >programming language. But they won't ever hurt in the way that Python 3
> >hurt.)
> It would be useful to explore what causes the most pain in the 2->3
> transition?  IMHO, it's not the deprecations or changes such as print ->
> print().  It's the bytes/str split - a fundamental change to core and
> common
> data types.  The question then is whether you foresee any similar looming
> pervasive change? [*]

I'm unsure about what's the single biggest pain moving to Python 3. In the
past I would have said that it's for sure the bytes/str split (which both
the biggest pain and the biggest payoff).

But if I look carefully into the soul of teams that are still on 2.7 (I
know a few... :-), I think the real reason is that Python 3 changes so many
different things, you have to actually understand your code to port it
(unlike with minor version transitions, where the changes usually spike in
one specific area, and you can leave the rest to normal attrition and
periodic maintenance).

> [*] I was going to add a joke about mandatory static type checking, but
> sometimes jokes are blown up into apocalyptic prophesy around here. ;)

Heh. :-)

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