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python中怎么用乘法

def sub3(n):

return n - 3

def square(n):

return n * n

在python中编写函数非常简单:

>>> my_list

[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

>>> [square(sub3(n)) for n in my_list]

[9, 4, 1, 0, 1, 4, 9, 16, 25, 36]

不幸的是,当想要使用组合作为 键时 ,这有点of脚:

>>> sorted(my_list, key=lambda n: square(sub3(n)))

[3, 2, 4, 1, 5, 0, 6, 7, 8, 9]

这实际上应该只是sorted(my_list, key=square*sub3),因为该函数__mul__无论如何都不会用于其他任何事情:

>>> square * sub3

TypeError: unsupported operand type(s) for *: 'function' and 'function'

好吧,那就定义它吧!

>>> type(sub3).__mul__ = 'something'

TypeError: can't set attributes of built-in/extension type 'function'

天哪!

>>> class CoolerFunction(types.FunctionType):

... pass

...

TypeError: Error when calling the metaclass bases

type 'function' is not an acceptable base type

天哪!

class Hack(object):

def __init__(self, function):

self.function = function

def __call__(self, *args, **kwargs):

return self.function(*args, **kwargs)

def __mul__(self, other):

def hack(*args, **kwargs):

return self.function(other(*args, **kwargs))

return Hack(hack)

嘿,现在我们到了某个地方。

>>> square = Hack(square)

>>> sub3 = Hack(sub3)

>>> [square(sub3(n)) for n in my_list]

[9, 4, 1, 0, 1, 4, 9, 16, 25, 36]

>>> [(square*sub3)(n) for n in my_list]

[9, 4, 1, 0, 1, 4, 9, 16, 25, 36]

>>> sorted(my_list, key=square*sub3)

[3, 2, 4, 1, 5, 0, 6, 7, 8, 9]

但是我不想Hack上课!在我不完全了解的范围内,作用域规则完全不同,这甚至比“ lameda”还要丑。我想对这些 功能

进行修补。我怎样才能做到这一点?

本文标签: python中怎么用乘法