[Python-Dev] clarification: subset vs equality Re: [Python-checkins] peps: Draft of PEP 399: Pure Python/C Accelerator Module Compatibiilty Requirements

[Brett Cannon]

On Tue, Apr 5, 2011 at 06:10, Jim Jewett <jimjjewett at gmail.com> wrote:

> On 4/4/11, brett.cannon <python-checkins at python.org> wrote:
> >   Draft of PEP 399: Pure Python/C Accelerator Module Compatibiilty
> > Requirements
>
> > +Abstract
> > +========
> > +
> > +The Python standard library under CPython contains various instances
> > +of modules implemented in both pure Python and C. This PEP requires
> > +that in these instances that both the Python and C code *must* be
> > +semantically identical (except in cases where implementation details
> > +of a VM prevents it entirely). It is also required that new C-based
> > +modules lacking a pure Python equivalent implementation get special
> > +permissions to be added to the standard library.
>
> I think it is worth stating explicitly that the C version can be even
> a strict subset.  It is OK for the accelerated C code to rely on the
> common python version; it is just the reverse that is not OK.
>

I thought that was obvious, but I went ahead and tweaked the abstract and
rationale to make this more explicit.
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