python实现矩阵乘法的方法

python实现矩阵乘法的方法

本文实例讲述了python实现矩阵乘法的方法。分享给大家供大家参考。

具体实现方法如下：  

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]]

希望本文所述对大家的Python程序设计有所帮助。