python - 具有选择性条件的 Numpy 洗牌？

Question

我想用一个条件打乱一个 2d Numpy 数组。例如，仅随机播放非零值。

import numpy as np
a = np.arange(9).reshape((3,3))
a[2,2] = 0

# Shuffle non-zero values 

# Example shuffle with only 0 staying in place
>>> a
array([[0, 5, 3],
       [7, 2, 6],
       [4, 1, 0]])

Answer 1

你可以这样做:

import numpy as np
a = np.arange(9).reshape((3,3))
a[2,2] = 0
c = a[a!=0]
np.random.shuffle(c)
a[a!=0] = c
a 
#  array([[0, 6, 5],
#         [2, 3, 7],
#         [4, 1, 0]])

如果你有不同的情况，你可以这样做:

import numpy as np
a = np.arange(9).reshape((3,3))
a[2,2] = 0
cond = a>3
c = a[cond]
np.random.shuffle(c)
a[cond] = c

更简洁的方式是:

a = np.arange(9).reshape((3,3))
a[2,2] = 0
a[a>3] = np.random.permutation(a[a>3])