[Numpy-discussion] is __array_ufunc__ ready for prime-time?

William Sheffler willsheffler at gmail.com
Tue Oct 31 15:15:24 EDT 2017

Thank you all kindly for your responses! Based on your encouragement, I
will pursue an ndarray subclass / __array_ufunc__ implementation. I had
been toying with np.set_numeric_ops, which is less than ideal (for example,
np.ndarray.around segfaults if I use set_numeric_ops in any way).

A second question: very broadly speaking, how much 'pain' can I expect
trying to use an np.ndarray subclass in the broader python scientific
computing ecosystem, and is there general consensus that projects 'should'
support ndarray subclasses?


> We spent a *long time* sorting out the messy details of __array_ufunc__
[1], especially for handling interactions between different types, e.g.,
between numpy arrays, non-numpy array-like objects, builtin Python objects,
objects that override arithmetic to act in non-numpy-like ways, and of
course subclasses of all the above.

> We hope that we have it right this time, but as we wrote in the NumPy
1.13 release notes "The API is provisional, we do not yet guarantee
backward compatibility as modifications may be made pending feedback." That
said, let's give it a try!

> If any changes are necessary, I expect it would likely relate to how we
handle interactions between different types. That's where we spent the
majority of the design effort, but debate is a poor substitute for
experience. I would be very surprised if the basic cases (one argument or
two arguments of the same type) need any changes.

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