[Python-Dev] Re: the "3*x works w/o __rmul__" bug

[Fernando Perez]

Hi all,

I just wanted to add a small comment on this discussion, which I'd been
following via the newsgroup mirror.

Python is picking up a lot of steam in the scientific computing community, and
in science it is quite common to encounter non-commutative multiplication.
Just to remind Guido from his old math days :), even for square matrices,
AB!=BA in most cases.  The Matrix class supplied with Numpy is one example of
a widely used library which implements '*' as a non-commutative multiplication
operator.

 From what I've read, I realize that this is quite a subtle and difficult bug
to treat.  I just wanted to add a data point for you folks to consider.
Please don't dismiss non-commutative multiplication as too much of an obscure
corner case, it is a daily occurrence for a growing number of python users
(scientists).

Thanks,

Fernando.