问题描述
给定以下 NumPy 数组，
Given the following NumPy array,
> a = array([[1, 2, 3, 4, 5], [1, 2, 3, 4, 5],[1, 2, 3, 4, 5]])
很简单，可以随机排列一行，
it's simple enough to shuffle a single row,
> shuffle(a[0])
> a
array([[4, 2, 1, 3, 5],[1, 2, 3, 4, 5],[1, 2, 3, 4, 5]])
是否可以使用索引符号来独立地对每一行进行洗牌?或者你必须遍历数组.我想到了类似的东西，
Is it possible to use indexing notation to shuffle each of the rows independently? Or do you have to iterate over the array. I had in mind something like,
> numpy.shuffle(a[:])
> a
array([[4, 2, 3, 5, 1],[3, 1, 4, 5, 2],[4, 2, 1, 3, 5]]) # Not the real output
虽然这显然行不通.
推荐答案
你必须多次调用 numpy.random.shuffle() 因为你是在独立地洗牌多个序列.numpy.random.shuffle() 适用于任何可变序列，实际上不是 ufunc.分别对二维数组 a 的所有行进行 shuffle 的最短和最有效的代码可能是
You have to call numpy.random.shuffle() several times because you are shuffling several sequences independently. numpy.random.shuffle() works on any mutable sequence and is not actually a ufunc. The shortest and most efficient code to shuffle all rows of a two-dimensional array a separately probably is
list(map(numpy.random.shuffle, a))
有些人更喜欢将其写为列表推导式:
Some people prefer to write this as a list comprehension instead:
[numpy.random.shuffle(x) for x in a]
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