这段代码的if instance is None: return self不会执行吧？

Question

看到文章
https://cloud.tencent.com/developer/article/1345536
上代码

class lazyproperty:
    def __init__(self, fun):
        self.fun = fun
    def __get__(self, instance, owner):
        if instance is None:
            return self
        value = self.fun(instance)
        setattr(instance, self.fun.__name__, value)
        return value

调用者

class Circle:
    def __init__(self, radius):
        self.radius = radius
    @lazyproperty
    def area(self):
        print('Computing area')
        return 3.1415 * self.radius ** 2

我的疑问是，lazyproperty里面的

        if instance is None:
            return self

多此一举，在任何情况下都不会触发，我修改一下

class lazyproperty:
    def __init__(self, fun):
        self.fun = fun
    def __get__(self, instance, owner):
        if instance is None:
            print('triggered')
            return self
        value = self.fun(instance)
        setattr(instance, self.fun.__name__, value)
        return value

请你在用Circle类的时候，触发

    if instance is None:
        print('triggered')
        return self

Answer 1

class Circle:
    def __init__(self, radius):
        self.radius = radius

    @lazyproperty
    def area(self):
        print('Computing area')
        return 3.1415 * self.radius ** 2

print(Circle.area)  # 输出 'triggered'