[Python-Dev] Infix operators (original) (raw)

Greg Ewing greg.ewing at canterbury.ac.nz
Fri Jul 25 04:02:30 CEST 2008

Scott Dial wrote:

Perhaps I'm nobody, but I think this would be ridiculous. Matrices are not native objects to the language.

Why should that matter? We already have things like sum(), which operates on any sequence of numbers, without needing a special "array of numbers" data type. I don't see why one shouldn't be able to perform matrix multiplication on a plausible representation of a matrix using the existing built-in sequence types.

Until a matrix is a first-order object in Python, there is no logic to making operators for them.

If there were a dedicated matrix type, there would actually be less reason to have a new operator, since that type could just implement * as matrix multiplication.

However, there are disadvantages to that, which become apparent when numpy is considered. There are good reasons for wanting * to mean elementwise multiplication of numpy arrays. There are also good reasons for wanting to use numpy arrays as matrices, since you get the benefit of all the other powerful things that numpy can do with arrays.

You can use a matrix type that's based somehow on a numpy array, but there are problems with that too. E.g. if you add a matrix and a plain numpy array, what type should the result be? If plain numpy arrays can be used directly as matrices, that problem goes away.

-- Greg

More information about the Python-Dev mailing list