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]