[Python-Dev] Matrix product

Greg Ewing greg.ewing at canterbury.ac.nz
Sat Jul 26 03:50:58 CEST 2008

Sebastien Loisel wrote:

> What are the odds of this thing going in?

I don't know. Guido has said nothing about it so far this
time round, and his is the only opinion that matters in the

I may write a PEP about this. However, since yesterday I've
realised that there's a rather serious problem with part
of my proposal.

The problem is that being able to multiply matrices isn't
much use without also being able to add them and multiply
them by numbers, which obviously can't work with the
built-in sequence types, since they already have other
meanings for + and *.

However, I still think that adding an @ operator for numpy
to use is a good idea. So I'm now suggesting that the
operator be added, with the intended meaning of matrix
multiplication, but that no implementation of it be
provided in core Python.

There is a precedent for this -- the ellipsis notation was
added purely for use by Numeric and its successors, and
nothing in core Python attaches any meaning to it.

> How do the PEPs work?

Someone writes a PEP. People talk about it. Eventually, Guido
either accepts it or rejects it (although in some cases it
is an infinitely long time before that happens:-).


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