python - 如何自动将python类中的 "register"方法作为列表类变量？

Question

在定义 Python 类时，我想使用装饰器将它的一些方法注册到类变量列表中。这是一个错误的python示例，它概述了我正在寻找的内容:

class MyClass:

    dangerous_methods = []

    @classmethod
    def dangerous_method(cls, func):
        cls.dangerous_methods.append(func)
        return func

    @MyClass.dangerous_method
    def incinerate(self):
        pass

    def watch_tv(self):
        pass

    @MyClass.dangerous_method
    def stab(self):
        pass

    def print_dangerous_methods(self):
        print(self.dangerous_methods)


obj = MyClass()
obj.print_dangerous_methods()

预期输出为

[<function MyClass.incinerate at 0x000001A42A629280>, <function MyClass.stab at 0x000001A42A629281>]

是否有可能在不过度折磨 Python 的情况下做到这一点？

Answer 1

您真正想要做的就是设置 dangerous在方法上。请记住，python 函数和方法是一流的对象，您可以对它们设置任意属性。

def print_dangerous_methods(cls):
    """ yes, you could also return a list """
    for name in dir(cls):
        f = getattr(cls, name)
        if callable(f) and getattr(f, "dangerous", False):
            print(name)


def dangerous(func):
    setattr(func, "dangerous", True)
    return func

class MyClass:

    @dangerous
    def incinerate(self):
        print("incinerate")

    def watch_tv(self):
        pass

    @dangerous
    def stab(self):
        return "you've been stabbed"

    class_born_dangerous = print_dangerous_methods

print("\non instance")
obj = MyClass()
print_dangerous_methods(obj)

print("\non class")
print_dangerous_methods(MyClass)

print("\nand yes, they work")
obj.incinerate()
print (obj.stab())

print("\nas a classmethod")
obj.class_born_dangerous()

输出:

on instance
incinerate
stab

on class
incinerate
stab

and yes, they work
incinerate
you've been stabbed

as a classmethod
incinerate
stab

如果要推广这种方法并设置任意属性，则需要设置参数化装饰器:

def annotate_func(**kwds):
    """set arbitrary attributes"""
    def actual_decorator(func):
        for k, v in kwds.items():
            setattr(func, k, v)
        return func
    return actual_decorator

您将按如下方式使用:

    @annotate_func(dangerous=1,range=1000)
    def shoot(self, times):
        for i in range(0, times):
            print("bang!")