python sparse matrix

[christine]

hi i'm new to python and i have to create a dictionary based sparse matrix. This is my code so far; but unfortunately my output are all zeros and i have no columns. I really need to get this error fixed since i need to add and multiply matrices. Is there anyone that could please help.

class GeneralSparse1:
    def __init__(self, mtx={}, m=3, n=3):
        self.matrix = {}
        self.m = m
        self.n = n
        self.matrix.update(mtx)
      
    def __getitem__(self, ij):
        return self.matrix.get(ij,0)  
    def __setitem__(self, ij, val):
        self.matrix[i,j] = val
    def __str__(self):
        s = "["
        if self.m> 0:
            for i in range(self.m):
                s += str(self[i])
                if i < self.m:
                    s += ", "
        for j in range(self.n):
                    s += str(self[j])
        s += "]"
        return s

My output :

from GeneralSparse1 import *
>>> if __name__=="__main__":
    x = GeneralSparse1({(2,1):1.0}, 2, 3)
    y = GeneralSparse1({(2,1):1.0}, 2, 3)
    print x
    print y

   
[0, 0, 000]
[0, 0, 000]