2つの行列を乗算するPythonプログラム

例

A = [[1, 2, 3],
   [4, 5, 6],
   [7, 8, 9]
]
B = [[5, 3, 3],
   [6, 5, 4],
   [0, 2, 0]
]
result= [[0, 0, 0],
   [0, 0, 0],
   [0, 0, 0]
]
# iterating by row
for i in range(len(A)):
   # iterating by column
   for j in range(len(B[0])):
      # iterating by rows
      for k in range(len(B)):
         result[i][j] += A[i][k] * B[k][j]
for ele in result:
   print(ele)

出力

[17, 19, 11]
[50, 49, 32]
[83, 79, 53]

アプローチ2-zip機能の使用

例

A = [[1, 2, 3],
   [4, 5, 6],
   [7, 8, 9]
]
B = [[5, 3, 3],
   [6, 5, 4],
   [0, 2, 0]
]
# using built-in zip function
result = [[sum(a * b for a, b in zip(A_row, B_col))
   for B_col in zip(*B)]
   for A_row in A]
for ele in result:
   print(ele)

出力

[17, 19, 11]
[50, 49, 32]
[83, 79, 53]

結論

この記事では、2つの行列を乗算する方法を学びました。