Python 继承的时候会丢掉 `__x` 命名的属性

class_test.py

class SuperClass(object):
    __table_name__ = 'subject_collection'
    __table = 'd'
    
    @classmethod
    def get(cls):
        inst = cls()
        inst.__class__ = SubClass
        return inst
    
    def subject_ids(self):
        raise NotImplemented


class SubClass(SuperClass):
    def subject_ids(self):
        return []
    
    
s = SuperClass.get()
s.subject_ids()
print(s.__table_name__)
print(s.__table)  # AttributeError