随机执行功能 [英] Execute a function randomly

问题描述

请考虑以下功能:

def a():
    print "a"
def b():
    print "b"

有没有办法选择随机运行的功能?我尝试使用:

Is there a way to pick a function to run randomly? I tried using:

random.choice([a(),b()])

但是它返回两个函数，我只希望它返回一个函数.

but it returns both functions, I just want it to return one function.

推荐答案

仅调用 selected 函数，而不是同时调用它们:

Only call the selected function, not both of them:

random.choice([a,b])()

下面是一个演示:

>>> import random
>>> def a():
...     print "a"
...
>>> def b():
...     print "b"
...
>>> random.choice([a,b])()
a
>>> random.choice([a,b])()
b
>>>

创建列表[a(),b()]时，旧代码都称为 起作用，导致Python同时打印a和b.之后，它告诉random.choice从列表[None, None] ¹ 中进行选择，该列表什么也不做.您可以从下面的演示中看到这一点:

Your old code called both functions when the list [a(),b()] was created, causing Python to print both a and b. Afterwards, it told random.choice to choose from the list [None, None]¹, which does nothing. You can see this from the demonstration below:

>>> [a(),b()]
a
b
[None, None]
>>>

但是，新代码使用random.choice从列表[a,b]中随机选择一个功能对象:

The new code however uses random.choice to randomly select a function object from the list [a,b]:

>>> random.choice([a,b])
<function b at 0x01AFD970>
>>> random.choice([a,b])
<function a at 0x01AFD930>
>>>

然后仅调用该函数.

¹ 默认情况下，函数返回None.由于a和b缺少返回语句，因此它们每个都返回None.

¹Functions return None by default. Since a and b lack return-statements, they each return None.

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