Numpy 随机序列 shuffle & permutation

1. numpy.random.shuffle(x)

Modify a sequence in-place by shuffling its contents.

This function only shuffles the array along the first axis of a multi-dimensional array. The order of sub-arrays is changed but their contents remains the same.

Parameters:
x : array_like. The array or list to be shuffled.

Returns: None

注意：

• 无返回值，改变原有 array
• 对于多维 array，只 shuffle 第一维

2. numpy.random.permutation(x) 

Randomly permute a sequence, or return a permuted range.

If x is a multi-dimensional array, it is only shuffled along its first index.

Parameters:
x : int or array_like

If x is an integer, randomly permute np.arange(x). If x is an array, make a copy and shuffle the elements randomly.

Returns:
out : ndarray

Permuted sequence or array range.

注意：

• 跟 shuffle 的区别
  • 有返回值
  • 且不改变原来的 array，会生成一个新的 array
• x 为整型时，先将 x 变成 array： np.arange(x)，再打乱顺序