[Numpy-discussion] Sparse matrices in NumPy?

I have a problem where I need to do matrix multiplication of a 7731x7731 matrix; storing this thing would take over 250 MB of memory, which is more than my machine has. :( However, the matrix is empty except for the main diagonal. Ideally, all that needs to be stored is a single vector 7731 elements long, and then tweak matrix multiplication algorithms to account for this. Are there any facilities in NumPy to do this sort of thing, or do I have to roll my own? Is there a way to effeciently store a very sparse matrix and do standard matrix multiplies? Thanks. -Paul Gettings Dep't of Geology & Geophysics University of Utah -- But Your Honor, they needed killin'.