On Fri, May 30, 2014 at 9:38 PM, Josh English
<joshua.r.engl...@gmail.com> wrote:
> I am trying to whip up a quick matrix class that can handle multiplication.
> Should be no problem, except when it fails.
> [SNIP]
> def zero_matrix(rows, cols):
>     row = [0] * cols
>     data = []
>     for r in range(rows):
>         data.append(row)

Each row of the matrix that you create here is the *same* list, not
different lists that happen to be equal.  So when you mutate one row,
you mutate all of them.  See:

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