numpy.random.shuffle返回无 [英] numpy.random.shuffle returns None

问题描述

我安装了numpy1.8.2，然后尝试了以下代码:

I installed numpy1.8.2 and then I tried the following code:

import numpy as np
a = np.arange(10)
print a, np.random.shuffle(a)

但是它的输出是:

[0 1 2 3 4 5 6 7 8 9] None

根据其

I don't know why it returns None, according to its doc it should be worked! I can't figure out the problem.

我在Windows 7上使用PyCharm 3.1.

I'm using PyCharm 3.1 on Windows 7.

推荐答案

shuffle在适当的位置起作用，因此不返回值.

shuffle works in place and therefore does not return a value.

In [1]: x = range(9)

In [2]: x
Out[2]: [0, 1, 2, 3, 4, 5, 6, 7, 8]

In [5]: print numpy.random.shuffle(x)
None

In [6]: x
Out[6]: [8, 7, 3, 4, 6, 0, 5, 1, 2]

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