我有两个关于元类和多重继承的问题。第一个是:为什么我得到一个 TypeError 的类Derived
而不是Derived2
?
class Metaclass(type): pass
class Klass(object):
__metaclass__ = Metaclass
#class Derived(object, Klass): pass # if I uncomment this, I get a TypeError
class OtherClass(object): pass
class Derived2(OtherClass, Klass): pass # I do not get a TypeError for this
确切的错误信息是:
TypeError: Error when calling the metaclass bases
Cannot create a consistent method resolution order (MRO) for bases object, Klass
第二个问题是:为什么super
在这种情况下不起作用(如果我使用__init__
而不是__new__
,则super
再次起作用):
class Metaclass(type):
def __new__(self, name, bases, dict_):
return super(Metaclass, self).__new__(name, bases, dict_)
class Klass(object):
__metaclass__ = Metaclass
我得到:
TypeError: Error when calling the metaclass bases type.__new__(X):
X is not a type object (str)
我正在使用 Python 2.6。