如何使用classmethod工厂函数实现继承

使用 super ,当然:

class A(object):
    def __init__(self, **kwds):
        self.__dict__.update(kwds)
    @classmethod
    def from_jdata(cls, data):
        if '_id' in data:
            data['uuid'] = data['_id']
            del data['_id']
        return cls(**data)

class B(A):
    def __init__(self, **kwds):
        super(B, self).__init__(**kwds)
    @classmethod
    def from_jdata(cls, data):
        # goal: make an instance of B,
        # using the logic that is implemented in A.from_jdata
        # But does some extra stuff, akin to:
        res = super().from_jdata(data)
        # res = super(B, cls).from_jdata(data) # in python 2
        res.__dict__['extra']='set'
        return res

在行动中:

In [6]: b = B.from_jdata({'_id':42, 'foo':'bar'})

In [7]: vars(b)
Out[7]: {'foo': 'bar', 'uuid': 42, 'extra': 'set'}

请注意,您试图做的不会起作用,因为 @classmethod 类或实例 . 您必须使用以下方式访问原始函数:

res = A.__dict__['from_jdata'].__func__(B, data)