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

[Antoine Pitrou]

> >You're proposing that new experimental modules spit warnings when you
> >use them?
> 
> To be explicit, when the system loada them.

There are many reasons to import a module, such as viewing its
documentation. And the warning will trigger if the import happens in
non-user code, such as a library; or when there is a fallback for the
module not being present. People usually get annoyed by intempestive
warnings which don't warn about an actual problem.

> >(something we do want to do even though we also want to convey the idea
> >that they're not yet "stable" or "fully approved")
> 
> Doing it with a message pointing at the page describing the status
> makes sure users read the docs before using them.

Sure, it's just much less user-friendly than conveying that idea in the
module's namespace. Besides, it only works if warnings are not silenced.

People are used to __future__ (and I've seen no indication that they
don't like it). __preview__ is another application of the same pattern
(using a special namespace to indicate the status of a feature).

Regards

Antoine.