matrix Multiplication

Fredrik Lundh fredrik at pythonware.com
Wed Oct 18 13:30:11 CEST 2006


"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> 






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