On Fri, Nov 9, 2018 at 4:59 PM, Stephan Hoyer <sho...@gmail.com> wrote: > On Fri, Nov 9, 2018 at 6:46 PM Nathaniel Smith <n...@pobox.com> wrote: >> >> But matrix isn't the only problem with asanyarray. np.ma also violates >> Liskov. No doubt there are other problematic ndarray subclasses out >> there too... > > > Please forgive my ignorance (I don't really use mask arrays), but how > specifically do masked arrays violate Liskov? In most cases shouldn't they > work the same as base numpy arrays, except with operations keeping track of > masks?
Since many operations silently skip over masked values, the computation semantics are different. For example, in a regular array, sum()/size() == mean(), but with a masked array these are totally different operations. So if you have code that was written for regular arrays, but pass in a masked array, there's a solid chance that it will silently return nonsensical results. (This is why it's better for NAs to propagate by default.) -n -- Nathaniel J. Smith -- https://vorpus.org _______________________________________________ NumPy-Discussion mailing list NumPy-Discussion@python.org https://mail.python.org/mailman/listinfo/numpy-discussion
