numpy 数组索引数组

a = np.array([7,8,9,10])
b=np.array([[3,1],[1,2]])
print(‘a:‘,a)
print(‘b:‘,b)
print(‘result:‘,a[b])
print(a[b].shape)




a: [ 7  8  9 10]
b: [[3 1]
 [1 2]]
result: [[10  8]
 [ 8  9]]
(2, 2)

a = np.array([
    [0, 0, 0],  # 黑色
    [255, 0, 0],  # 红色
    [0, 255, 0],  # 绿色
    [0, 0, 255],  # 蓝色
    [255, 255, 255]  # 白色
])

b= np.array([
    [0, 1, 2, 0],
    [0, 3, 4, 0]
])
print(a.shape)
print(b.shape)
print(‘result:‘,a[b])
print(a[b].shape)


(5, 3)
(2, 4)
result: [[[  0   0   0]
  [255   0   0]
  [  0 255   0]
  [  0   0   0]]

 [[  0   0   0]
  [  0   0 255]
  [255 255 255]
  [  0   0   0]]]
(2, 4, 3)