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

[Jim Jewett]

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.

-jJ