Hi All, I wondered if the move to python3-only starting with numpy 1.17 would be a good reason to act on what we all seem to agree: that the matrix class was a bad idea, with its overriding of multiplication and lack of support for stacks of matrices. For 1.17, minimum python supposedly is >=3.5, so we will be guaranteed to have the matrix multiply operator @ available, and hence there is arguably even less of a case for keeping the matrix class; removing it would allow taking out quite a bit of accumulated special-casing (the immediate reasons for writing this were gh-10123 and 10132). What do people think? If we do go in this direction, we might want to add PendingDeprecationWarning for 1.15 (maybe DeprecationWarning for python3; for python2 matrix would never disappear). All the best, Marten