python: for in 循环

for in 循环所实现的是按照序号顺序读取，而不是按照数组元素。

import numpy as np 
index = np.arange(20)
print(index)
for i in index:
    print(i)
    np.random.shuffle(index)
    print(index)

输出

[ 0  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15 16 17 18 19]
0
[15 12 19 11  6  2 16  5  1 17  7 18  8  4 13  9  0 14  3 10]
12
[14  3 11  1  0 18 10  8 12  2 19 15  6  5  9 16  7 13 17  4]
11
[12  6  2 19 13  1 11 17 14  3 18  5  8  9 16 15 10  7  0  4]
19
[ 6  7  2  5 18 14  8 19 13  4 16  3 15 17  0 12 11  1  9 10]
18
[14 18  7  8 15 12  6  3  5 17 13 16 11  9  4 19  2  0 10  1]
12
[14  5  8  3 18  0 13 15  9  1  7 10 12  2  4 19  6 16 17 11]
13
[ 1  0 16 11 14  8  5 15 18 19  3  7 13  9 17  4  6  2 10 12]
15
[ 3 14 11  8 12  1  0 16 19  6  4 17  7  5 10 15  2 18  9 13]
19
[ 4 17  9 18 19  8  7 10 16 14  5  0 12 13  3  2 11  6  1 15]
14
[ 8 14  2 19 16  5  7 13 17  6  1 15 10 11  9  4  0 18  3 12]
1
[ 9  1  7  6  2  0 16 15 10 11 14 12 19 18 17  5  8  3  4 13]
12
[ 3  9 19 18 16 17  1  6 12  0  5 13 10 15  2  4  7  8 11 14]
10
[10 12 11 16  1  4  5 14  9 13 19  3 18  2  6 17 15  0  7  8]
2
[10  3 12  5  6 17  0  8 14 11  7  2  4 16  9 18  1 13 19 15]
9
[ 4  2  9 15 19  7 11  3  5 12 18  8 16 10 14  0  6 13  1 17]
0
[ 0 17  2  5  9 18 13  4 10 15  3  7 19 12  6 16 11 14  8  1]
11
[ 3 17  1  7 16  8 18 12  0 10  5 15 14 19  4  9 13  2  6 11]
2
[ 7  2  9  5 12 16  6 11  8 19 13 18 10 14  1 17 15  4  3  0]
3
[11  0  6  5 14 15 10 19  2 12  1 13 18  4  9 16  3  7 17  8]
8
[11  0  9 12  1  2  5 16  8  7 17  4 19  6 13 10 14 15 18  3]