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。

http://www.cda.cn/uploadfile/image/20180424/20180424063807_83442.png

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。