python - 如何从 Python 中重写的@classmethod 调用父类的@classmethod？

Question

假设我有一个类

class SimpleGenerator(object):
    @classmethod
    def get_description(cls):
        return cls.name

class AdvancedGenerator(SimpleGenerator):
    @classmethod
    def get_description(cls):
        desc = SimpleGenerator.get_description() # this fails
        return desc + ' Advanced(tm) ' + cls.adv_feature

现在我已经扩展了上面的每个类，使每个类都有一个具体的类:

class StringGenerator(SimpleGenerator)
    name = 'Generates strings'
    def do_something():
        pass

class SpaceShuttleGenerator(AdvancedGenerator)
    name = 'Generates space shuttles'
    adv_feature = ' - builds complicated components'
    def do_something():
        pass

现在假设我打电话

SpaceShuttleGenerator.get_description()

问题是，在 AdvancedGenerator 中，我想调用 SimpleGenerator 中的方法，传递类的一个实例，特别是 SpaceShuttleGenerator。这能做到吗？

注意:示例已简化，因为我的具体示例涉及更多。假设我的目标不是连接字符串。

Answer 1

使用super() :

@classmethod
def get_description(cls):
    desc = super(AdvancedGenerator, cls).get_description()
    return desc + ' Advanced(tm) ' + cls.adv_feature

使用 SimpleGenerator.get_description() 和 super(AdvancedGenerator, cls).get_description() 的区别在于 cls 将被设置到。直接调用类时，cls设置为SimpleGenerator，使用super()，cls会引用高级生成器。

比较您的代码(调整为使用 __name__ 来说明差异):

>>> class SimpleGenerator(object):
...     @classmethod
...     def get_description(cls):
...         return cls.__name__
... 
>>> class AdvancedGenerator(SimpleGenerator):
...     @classmethod
...     def get_description(cls):
...         desc = SimpleGenerator.get_description() 
...         return desc + ' Advanced(tm)'
... 
>>> AdvancedGenerator.get_description()
'SimpleGenerator Advanced(tm)'

并使用super():

>>> class AdvancedGenerator(SimpleGenerator):
...     @classmethod
...     def get_description(cls):
...         desc = super(AdvancedGenerator, cls).get_description()
...         return desc + ' Advanced(tm)'
... 
>>> AdvancedGenerator.get_description()
'AdvancedGenerator Advanced(tm)'