为什么要在python中使用类方法？ [英] Why should I use a classmethod in python?

问题描述

我正在python中的某个类中编写一个函数，人们建议我向该函数添加 @classmethod 装饰器。

I am writing a function in some class in python, and people suggested to me to add to this function a @classmethod decorator.

我的代码

import random


class Randomize:
    RANDOM_CHOICE = 'abcdefg'

    def __init__(self, chars_num):
        self.chars_num = chars_num

    def _randomize(self, random_chars=3):
        return ''.join(random.choice(self.RANDOM_CHOICE)
                       for _ in range(random_chars))

建议的更改：

    @classmethod
    def _randomize(cls, random_chars=3):
        return ''.join(random.choice(cls.RANDOM_CHOICE)
                       for _ in range(random_chars))

我几乎总是只使用 _randomize 函数。

I'm almost always using only the _randomize function.

我的问题是：将类添加到函数中有什么好处？方法装饰器？

My question is: What is the benefits from adding to a function the classmethod decorator?

推荐答案

如果看到 _randomize 方法，您没有使用任何实例变量（在init中声明），但使用的是类 var 即 RANDOM_CHOICE ='abcdefg' 。

If you see _randomize method, you are not using any instance variable (declared in init) in it but it is using a class var i.e. RANDOM_CHOICE = 'abcdefg'.

import random

class Randomize:
    RANDOM_CHOICE = 'abcdefg'

    def __init__(self, chars_num):
        self.chars_num = chars_num

    def _randomize(self, random_chars=3):
        return ''.join(random.choice(self.RANDOM_CHOICE)
                       for _ in range(random_chars))

这意味着，您的方法可以不作为实例方法而存在，并且可以在类上直接调用它。

It means, your method can exist without being an instance method and you can call it directly on class.

  Randomize._randomize()

现在，问题来了，它有什么优势吗？

Now, the question comes does it have any advantages?

• 我想是的，你不知道

• I guess yes, you don't have to go through creating an instance to use this method which will have an overhead.

ran = Randomize() // Extra steps
ran._randomize()   

您可以在此处了解更多信息。

You can read more about class and instance variable here.

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