python 中的 metaclass

class Meta(type):
    pass

class M1(Meta):
    pass
class M2(metaclass=M1):
    pass

class Test(M2,metaclass=Meta):
    pass

print(type(Test)) # <class ‘__main__.M1‘>

# 说明 没有找自己的metaclass ，而是用了父亲的metaclass

class Meta(type):
    pass

class M1(Meta):
    pass
class M2(metaclass=M1):
    pass
class M3(metaclass=Meta):
    pass
class Test(M2,M3,metaclass=Meta):
    pass
    

print(type(Test)) # <class ‘__main__.M1‘>

# 两个父亲都有metaclass的时候，M2的metaclass是M3metaclass的子类
# 用子类不用父类

class Meta(type):
    pass


class M1(Meta):
    pass

class M4(M1):
    pass

class M2(metaclass=M4):
    pass


class M3(metaclass=Meta):
    pass




class Test(M2, M3, metaclass=M4):
    pass


print(type(Test))  # <class ‘__main__.M4‘>