Python matrix mult

def matrixmult (matA, matB):
	if len (matA) != len (matB[0]) or len (matA[0]) != len(matB):
		return None
	result = list ()
	for x in range (0, len (matA)):
		result.append (list ())
		for y in range (0, len (matA[0])):
			result[x].append (sum (matA[x]) * sum ([row[y] for row in matB]))
	return result

mat1 = ((0,1,2),(3,4,5),(6,7,8))
mat2 = ((9,8,7),(6,5,4),(3,2,1))
print mat1
print mat2
print matrixmult (mat1, mat2)