可以在纯Python中实现staticmethod和classmethod装饰器吗？ [英] Can the staticmethod and classmethod decoraters be implemented in pure Python?

问题描述

这是一个学术问题，而不是实际问题。我正在尝试研究Python的基础，但我想知道：我可以实现 staticmethod 和 classmethod 装饰器吗

This is an academic question, more than a practical one. I'm trying to delve into the foundations of Python, and I wonder: could I implement the staticmethod and classmethod decorators in pure Python if I wanted to?

对于 staticmethod ，也许我可以保留对原始函数的引用并调用

For staticmethod maybe I could keep a reference to the original function and call it omitting the first argument?

对于 classmethod 也许我可以保留对原始函数的引用并称为传递第一个参数的类型，而不是参数本身？ （我怎么处理直接在课堂上被调用的呢？）

For classmethod maybe I could keep a reference to the original function and call it passing the type of the first argument, rather than the argument itself? (How would I handle it being called directly on the class?)

再次，这并不是说我想在我的程序中实际实现它。我想从中学习语言的工作原理。如果可能的话，我将非常感谢代码示例。如果没有，我将解释为什么在理论上无法做到这一点。谢谢！

Again, it's not that I want to actually implement it in my programs; I want to learn how the language works from it. If it's possible to do I would really appreciate code samples. If not, I would appreciate explanations why it can't be done theoretically. Thanks!

编辑：：感谢您的回答和对描述符协议的引用！为了进一步扩展我对Python的理解，我想再问两件事：

Thanks for the answer and for the reference to the descriptor protocol! As a means to further extend my understanding of Python I'd like to ask two more things:

• 描述符协议，例如通过在类中实现__ call __特殊方法？

• Could this be done without the descriptor protocol, for example by implementing the __ call __ special method in our classes?

描述符协议在Python 2.7和Python中是否以相同的方式工作3.x？

Does the descriptor protocol work the same way in Python 2.7 and in Python 3.x?

再次感谢！

推荐答案

文档中有示例：

class StaticMethod(object):
    "Emulate PyStaticMethod_Type() in Objects/funcobject.c"

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

    def __get__(self, obj, objtype=None):
        return self.f

并且：

class ClassMethod(object):
    "Emulate PyClassMethod_Type() in Objects/funcobject.c"

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

    def __get__(self, obj, klass=None):
        if klass is None:
            klass = type(obj)
        def newfunc(*args):
            return self.f(klass, *args)
        return newfunc

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