洗牌 vs 置换 numpy [英] shuffle vs permute numpy

问题描述

numpy.random.shuffle(x) 和 numpy.random.permutation(x) 有什么区别?

我已经阅读了文档页面，但是当我只想随机打乱数组的元素时，我无法理解两者之间是否有任何区别.

I have read the doc pages but I could not understand if there was any difference between the two when I just want to randomly shuffle the elements of an array.

更准确地说，假设我有一个数组 x=[1,4,2,8].

To be more precise suppose I have an array x=[1,4,2,8].

如果我想生成x的随机排列，那么shuffle(x)和permutation(x)有什么区别?

If I want to generate random permutations of x, then what is the difference between shuffle(x) and permutation(x)?

推荐答案

np.random.permutation 与 np.random.shuffle 有两个不同点:

np.random.permutation has two differences from np.random.shuffle:

• 如果传递一个数组，它将返回一个混洗过的数组副本；np.random.shuffle 原地打乱数组
• 如果传递一个整数，它将返回一个混洗的范围，即 np.random.shuffle(np.arange(n))

• if passed an array, it will return a shuffled copy of the array; np.random.shuffle shuffles the array inplace
• if passed an integer, it will return a shuffled range i.e. np.random.shuffle(np.arange(n))

如果 x 是一个整数，随机置换 np.arange(x).如果 x 是数组，则复制并随机打乱元素.

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

源代码可能有助于理解这一点:

The source code might help to understand this:

3280        def permutation(self, object x):
...
3307            if isinstance(x, (int, np.integer)):
3308                arr = np.arange(x)
3309            else:
3310                arr = np.array(x)
3311            self.shuffle(arr)
3312            return arr

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