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

Guido van Rossum guido at python.org
Sun Jan 29 04:29:05 CET 2012

On Sat, Jan 28, 2012 at 5:33 PM, Nick Coghlan <ncoghlan at gmail.com> wrote:
> I'm willing to go along with that (especially given your report of
> AppEngine's experience with the "labs" namespace).
> Can we class this as a pronouncement on PEP 408? That is, "No to
> adding a __preview__ namespace, but yes to adding regex directly for
> 3.3"?

Yup. We seem to have a tendency to over-analyze decisions a bit lately
(witness the hand-wringing about the hash collision DoS attack).

For those who worry about people who copy recipes that stop working, I
think they're worrying too much. If people want to take a shortcut
without reading the documentation or understanding the code they are
copying, fine, but they should realize the limitations of free advice.

I don't mean to put down the many great recipes that exist or the
value of copying code to get started quickly. But I think our
liability as maintainers of the library is sufficiently delineated
when we clearly mark a module as experimental in the documentation.
(Recipe authors should ideally also add this warning to their recipe
if it depends on an experimental API.)

Finally, if you really want to put warnings in whenever an
experimental module is being used, make it a silent warning, like
SilentDeprecationWarning. That allows people to request more strict
warnings without unduly alarming the users of an app.

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

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