Multiplicacion de Matriz Python

#!/usr/bin/python
import os
import time
from random import randint

inicio = time.time()
n = 3
# PARA HACER Numeros aleatorios
# matrix = [[randint(0,3) for fila in range(n)] for col in range(n)]
matrix1 = [[1, 2, 3], [3, 4, 5], [3, 2, 1]]
matrix2 = [[2, 3, 4], [5, 5, 5], [1, 1, 1]]
matrix3 = [[0 for fila in range(n)] for col in range(n)]

def matrix(matrix1, matrix2, n):
    for x in range(n):
        for y in range(n):
           multiplicar(matrix1, matrix2, matrix3, n, x, y)

    return matrix3

def multiplicar(matrix1, matrix2, matrix3, n, x, y):
    for i in range(n):
        matrix3[x][y] += matrix1[x][i]*matrix2[i][y]


def main():
    os.system("clear")
    print "\n", matrix1[0], "\n", matrix1[1], "\n", matrix1[2]
    print "\n", matrix2[0], "\n", matrix2[1], "\n", matrix2[2]
    matrix3 = matrix(matrix1,matrix2,n)
    print "\n", matrix3[0], "\n", matrix3[1], "\n", matrix3[2]
    fin = time.time()
    tiempo = fin - inicio
    print "\nEl tiempo de ejecucion es :", tiempo


main()