numpy笔记：random.permutation

作用是随机排列序列

表示对range(n)的序列进行排序【如果n是负数的话，返回一个空的list】

import numpy as np
print(np.random.permutation(5))
print(np.random.permutation(5))
'''
[3 4 0 1 2]
[2 3 0 1 4]
'''
print(np.random.permutation(-5))#[]

随机排序list中的元素

import numpy as np
lst=[1,3,5,7,9]
print(np.random.permutation(lst))
print(np.random.permutation(lst))
'''
[9 5 7 1 3]
[7 9 1 5 3]
'''

我们先分别看一个两维的和一个三维的例子：

import numpy as np
lst=[[1,3],
     [5,7],
     [9,11]]
print(np.random.permutation(lst))
print(np.random.permutation(lst))
'''
[[ 1  3]
 [ 9 11]
 [ 5  7]]
[[ 5  7]
 [ 1  3]
 [ 9 11]]
'''

import numpy as np
lst=[[[1,3],[5,7]],[[2,4],[6,8]],[[-1,-3],[-2,-4]]]
print(np.random.permutation(lst))
print('*'*10)
print(np.random.permutation(lst))
print('*'*10)
print(np.random.permutation(lst))
'''
[[[-1 -3]
  [-2 -4]]

 [[ 2  4]
  [ 6  8]]

 [[ 1  3]
  [ 5  7]]]
**********
[[[-1 -3]
  [-2 -4]]

 [[ 2  4]
  [ 6  8]]

 [[ 1  3]
  [ 5  7]]]
**********
[[[ 2  4]
  [ 6  8]]

 [[-1 -3]
  [-2 -4]]

 [[ 1  3]
  [ 5  7]]]
'''

发现规律了嘛？permutation只是对第一个维度进行排序，即a[0][...],a[1][....],a[2][....],.....而对于其内部则不打乱顺序