[Numpy-discussion] Proposal to accept NEP-18, __array_function__ protocol

[Charles R Harris]

On Wed, Aug 15, 2018 at 10:25 AM, Matthew Brett <matthew.brett at gmail.com>
wrote:

> Hi,
>
> Thanks Nathaniel for this thoughtful response.
>
> On Mon, Aug 13, 2018 at 10:44 AM, Nathaniel Smith <njs at pobox.com> wrote:
> ...
> > The other approach would be to incrementally add clean, well-defined
> > dunder methods like __array_ufunc__, __array_concatenate__, etc. This
> > way we end up putting some thought into each interface, making sure
> > that it's something we can support, protecting downstream libraries
> > from unnecessary complexity (e.g. they can implement
> > __array_concatenate__ instead of hstack, vstack, row_stack,
> > column_stack, ...), or avoiding adding new APIs entirely (e.g., by
> > converting existing functions into ufuncs so __array_ufunc__ starts
> > automagically working). And in the end we get a clean list of dunder
> > methods that new array container implementations have to define. It's
> > plausible to imagine a generic test suite for array containers. (I
> > suspect that every library that tries to implement __array_function__
> > will end up with accidental behavioral differences, just because the
> > numpy API is so vast and contains so many corner cases.) So the
> > clean-well-defined-dunders approach has lots of upsides. The big
> > downside is that this is a much longer road to go down.
>
> Does everyone agree that, if we had infinite time and resources, this
> would be the better solution?


> If we devoted all the resources of the current Numpy grant to taking
> this track, could we complete it in a reasonable time?
>

I think it is further down the road than that. Determining a core set of
functions would depend on feedback (need), as well be dependent on
implementation details for other functions. I think a dependency list for
common NumPy functions might be interesting.

That said, I don't think the current proposal is orthogonal to this. I
don't expect every NumPy function to make call through this API, and we
should probably try to limit, and list, the functions that implement the
proposed mechanism.

Chuck
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