On 09.09.19 03:26, Nathaniel Smith wrote:
[snip]
Generic in the sense that you can write __array_ufunc__ once and have
it work for all ufuncs.
You can do that too with __ua_function__, you get np.ufunc.__call__,
with self=<any-ufunc>. The same holds for say, RandomState objects, once
implemented.
Most duck array libraries can write a single
implementation of __array_ufunc__ that works for *all* ufuncs, even
new third-party ufuncs that the duck array library has never heard of,
I see where you're going with this. You are thinking of reusing the ufunc
implementation to do a computation. That's a minor use case (imho), and I can't
remember seeing it used.
I mean, I just looked at dask and xarray, and they're both doing
exactly what I said, right now in shipping code. What use cases are
you targeting here if you consider dask and xarray out-of-scope? :-)
this is case where knowing if something is a ufunc helps use a property of it.
so there the more specialized nature of __array_ufunc__ helps. Seems niche
though, and could probably also be done by checking if a function is an
instance of np.ufunc via __array_function__
Sparse arrays aren't very niche... and the isinstance trick is
possible in some cases, but (a) it's relying on an undocumented
implementation detail of __array_function__; according to
__array_function__'s API contract, you could just as easily get passed
the ufunc's __call__ method instead of the object itself, and (b) it
doesn't work at all for ufunc methods like reduce, outer, accumulate.
These are both show-stoppers IMO.
It does work for all ufunc methods. You just get passed in the
appropriate method (ufunc.reduce, ufunc.accumulate, ...), with
self=<any-ufunc>.
[snip]
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