代码：
class MyType(type):
def __init__(self, *args, **kwargs):
super(MyType, self).__init__(*args, **kwargs)
def __call__(self, *args, **kwargs):
obj = self.__new__(self, *args, **kwargs)
obj.__init__(*args, **kwargs)
return obj
class Foo(object, metaclass=MyType):
def __init__(self):
print(‘xxx‘)
obj = Foo()
print(obj)
结果
xxx <__main__.Foo object at 0x0000022688A07EB8>
我们看下面的代码
new
class Foo(object):
def __init__(self):
return ‘init‘
def __new__(cls, *args, **kwargs):
return ‘new‘
obj = Foo()
print(obj)
结果 ：new
class Foo(object):
def __init__(self):
return ‘init‘
def __new__(cls, *args, **kwargs):
return cls.__init__(cls)
obj = Foo()
print(obj)
结果 init
由此可以看出 实例化对象的过程，__new__()比__init__()先执行
但是 实际上，在这次“”交♂易“”之前还走了一个中间商 那就是type的__call__(),但是我们并看不到__claa__()的源码。
类的metaclass 默认是type。
class MyType(type):
def __call__(self, *args, **kwargs):
return ‘MyType‘
class Foo(object, metaclass=MyType):
def __init__(self):
return ‘init‘
def __new__(cls, *args, **kwargs):
return cls.__init__(cls)
def __call__(self, *args, **kwargs):
return ‘call‘
obj = Foo()
print(obj)
结果：MyType
