[Python-Dev] PEP 408 -- Standard library preview package (original) (raw)

Guido van Rossum guido at python.org
Sat Jan 28 18:15:15 CET 2012

On Sat, Jan 28, 2012 at 5:04 AM, Paul Moore <p.f.moore at gmail.com> wrote:

On 28 January 2012 09:18, Nick Coghlan <ncoghlan at gmail.com> wrote:

It's basically us saying to Python users "We're explicitly flagging this PyPI module for inclusion in the next major Python release. We've integrated it into our build process, test suite and binary releases, so you don't even have to download it from PyPI in order to try it out, you can just import it from the preview namespace (although you're still free to download it from PyPI if you prefer - in fact, if you need to support multiple Python versions, we actively recommend it!). There's still a small chance this module won't make the grade and will be dropped from the standard library entirely (that's why it's only a preview), but most likely it will move into the main part of the standard library with full backwards compatibility guarantees in the next release". +1.

Hm. You could do this just as well without a preview package. You just flag the module as experimental in the docs and get on with your life.

We have some experience with this in Google App Engine. We used to use a separate "labs" package in our namespace and when packages were deemed stable enough they were moved from labs to non-labs. But the move always turned out to be a major pain, causing more breakage than we would have had if we had simply kept the package location the same but let the API mutate. Now we just put new, experimental packages in the right place from the start, and put a loud "experimental" banner on all pages of their docs, which is removed once the API is stable.

There is much less pain now: while incompatible changes do happen for experimental package, they are not frequent, and rarely earth-shattering, and usually the final step is simply removing the banner without making any (incompatible) changes to the code. This means that the final step is painless for early adopters, thereby rewarding them for their patience instead of giving them one final kick while they sort out the import changes.

So I do not support the preview package. I think we're better off flagging experimental modules in the docs than in their name. For the specific case of the regex module, the best way to adoption may just be to include it in the stdlib as regex and keep it there. Any other solution will just cause too much anxiety.

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

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