対角を除いて乗算

Numpy multiplication and create new list B[i] = Product(A[j]) where j =! i – StackOverflow

[2, 1, 5, 9]

↓

[
  [2, 1, 5, 9],
  [2, 1, 5, 9],
  [2, 1, 5, 9],
  [2, 1, 5, 9],
]

↓

[
  [1, 1, 5, 9],
  [2, 1, 5, 9],
  [2, 1, 1, 9],
  [2, 1, 5, 1],
]

↓

[45., 90., 18., 10.]

という処理を考える．

import numpy as np


a = np.array([2, 1, 5, 9])
a[None].repeat(len(a), 0).prod(1) / a

array([45., 90., 18., 10.])