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

[Michael Foord]

On 28/01/2012 04:44, Stephen J. Turnbull wrote:
> Michael Foord writes:
>
>   >  >>  Assuming the module is then promoted to the the standard library proper in
>   >  >>  release ``3.X+1``, it will be moved to a permanent location in the library::
>   >  >>
>   >  >>       import example
>   >  >>
>   >  >>  And importing it from ``__preview__`` will no longer work.
>   >  >  Why not leave it accessible through __preview__ too?
>   >
>   >  +1
>
> Er, doesn't this contradict your point about using
>
> try:
>      from __preview__ import spam
> except ImportError:
>      import spam
>
> ?
>
> 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*.

Michael

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