Python 矩阵乘法

def matrixMul(A, B):
    res = [[0] * len(B[0]) for i in range(len(A))]
    for i in range(len(A)):
        for j in range(len(B[0])):
            for k in range(len(B)):
                res[i][j] += A[i][k] * B[k][j]
    return res

def matrixMul2(A, B):
    return [[sum(a * b for a, b in zip(a, b)) for b in zip(*B)] for a in A]

a = [[1,2], [3,4], [5,6], [7,8]]
b = [[1,2,3,4], [5,6,7,8]]

print matrixMul(a,b)
print matrixMul(b,a)
print "-"*90

print matrixMul2(a,b)
print matrixMul2(b,a)
print "-"*90

from numpy import dot
print map(list,dot(a,b))
print map(list,dot(b,a))

#Out:
#[[11, 14, 17, 20], [23, 30, 37, 44], [35, 46, 57, 68], [47, 62, 77, 92]]
#[[50, 60], [114, 140]]
#------------------------------------------------------------------------------------------
#[[11, 14, 17, 20], [23, 30, 37, 44], [35, 46, 57, 68], [47, 62, 77, 92]]
#[[50, 60], [114, 140]]
#------------------------------------------------------------------------------------------
#[[11, 14, 17, 20], [23, 30, 37, 44], [35, 46, 57, 68], [47, 62, 77, 92]]
#[[50, 60], [114, 140]]