[Python-Dev] PEP 408 -- Standard library __preview__ package

Ethan Furman ethan at stoneleaf.us
Sat Jan 28 19:48:31 CET 2012

Michael Foord wrote:
> On 28/01/2012 04:44, Stephen J. Turnbull wrote:
>> I think it's a bad idea to introduce a feature that's *supposed* to
>> break (in the sense of "make a break", ie, change the normal pattern)
>> with every release and then try to avoid breaking (in the sense of
>> "causing an unexpected failure") code written by people who don't want
>> to follow the discipline of keeping up with changing APIs.  If they
>> want that stability, they should wait for the stable release.
>> Modules should become unavailable from __preview__ as soon as they
>> have a stable home.
> I like not breaking people's code where *possible*.

__preview__ is not about stability.  It's about making code easily 
available for testing before the API freezes.

If nothing has changed once it graduates, how hard is it to change a few 
lines of code from

     from __preview__ import blahblahblah


     import blahblahblah


It seems to me that including a __preview__ package in production 
software is a mistake, and not its intention.


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