1.abs
實現抽象類就是需要修改metaclass
2.django
中的orm也是修改metaclass
3.通過mytype創建對象,實現繼承
class MyType(type):
def __init__(self, *args, **kwargs):
super(MyType, self).__init__(*args, **kwargs)
def __call__(cls, *args, **kwargs):
print('xxxx')
return super(MyType, cls).__call__(*args, **kwargs)
# Base = MyType('Base', (object,), {})
# MyType('Base', (object,), {}) 是有MyType創建; metaclass=MyType
# 1. type可以創建類metaclass=type;MyType也可以創建類metaclass=MyType
# 2. Base = MyType('Base', (object,), {}) -->
# class Base(metaclass=MyType):
# pass
# class Foo(Base):
# pass
class Foo(MyType('Base', (object,), {})):
pass
obj = Foo()
4.通過封裝函數來創建新的對象,更加方便
class MyType(type):
def __init__(self, *args, **kwargs):
super(MyType, self).__init__(*args, **kwargs)
def __call__(cls, *args, **kwargs):
return super(MyType, cls).__call__(*args, **kwargs)
def with_metaclass(base):
return MyType('XX', (base,), {})
class Foo(with_metaclass(object)):
pass