matrix Multiplication

Gerrit Holl gerrit at nl.linux.org
Wed Oct 18 14:31:27 CEST 2006


On 2006-10-18 14:15:17 +0200, Sssasss wrote:
> Fredrik Lundh wrote:
> > "Sssasss" wrote:
> >
> > > I wan't to multiply two square matrixes, and i don't understand why it
> > > doesn't work.
> > >
> > > def multmat(A,B):
> > >    "A*B"
> > >    if len(A)!=len(B): return "error"
> > >    D=[]
> > >    C=[]
> > >    for i in range(len(A)): D.append(0)
> > >    for i in range(len(A)): C.append(D)
> >
> > append doesn't copy data, so you're basically adding len(A) references to
> > the same D list to C.  for more on this, see:
> >
> >     http://pyfaq.infogami.com/how-do-i-create-a-multidimensional-list
> > 
> > </F>
> 
> Ok!! Tank you very much, i understand now.

You might also want to look at numpy/numarray.

Gerrit.



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