Python中None作为索引的作用

None的作用主要是在使用None的位置新增一个维度。

a = np.arange(25).reshape(5,5)
print(a)
'''
[[ 0  1  2  3  4]
[ 5  6  7  8  9]
[10 11 12 13 14]
[15 16 17 18 19]
[20 21 22 23 24]]
'''
print(a[:,None])
'''
shape:5*1*5
[[[ 0  1  2  3  4]]
[[ 5  6  7  8  9]]
[[10 11 12 13 14]]
[[15 16 17 18 19]]
[[20 21 22 23 24]]]
'''

print(a[:,:,None])
'''
shape: 5*5*1
[[[ 0]
 [ 1]
 [ 2]
 [ 3]
 [ 4]]
[[ 5]
 [ 6]
 [ 7]
 [ 8]
 [ 9]]
[[10]
 [11]
 [12]
 [13]
 [14]]
[[15]
 [16]
 [17]
 [18]
 [19]]
[[20]
 [21]
 [22]
 [23]
 [24]]]
'''

标签：24,None,20,21,22,23,Python,索引
来源： https://www.cnblogs.com/sxq-blog/p/16644471.html