python :

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类的特殊成员

　　python的类成员存在着一些具有特殊含义的成员

1.__init__: 类名() 自动执行 __init__

class Foo(object):    def __init__(self,a1,a2):        self.a1 = a1        self.a2 = a2obj = Foo(1,2)

 

2.__call__: 对象() 自动执行__call__

class Foo(object):    def __call__(self, *args, **kwargs):        print(1111,args,kwargs)        return 123obj = Foo()ret = obj(6,4,2,k1=456)

 

3.__getitem__: 对象['xx'] 自动执行__getitem__

class Foo(object):    def __getitem__(self, item):        print(item)        return 8obj = Foo()ret = obj['yu']print(ret)

 

4.__setitem__: 对象['xx'] = 11 自动执行__setitem__

class Foo(object):    def __setitem__(self, key, value):        print(key, value, 111111111)obj = Foo()obj['k1'] = 123

 

5.__delitem__: del 对象[xx] 自动执行__delitem__

class Foo(object):    def __delitem__(self, key):        print(key)obj = Foo()del obj['uuu']

 

6.__add__: 对象+对象 自动执行__add__

class Foo(object):    def __init__(self, a1, a2):        self.a1 = a1        self.a2 = a2    def __add__(self,other):        return self.a1 + other.a2obj1 = Foo(1,2)obj2 = Foo(88,99)ret = obj2 + obj1print(ret)

 

7.__enter__ / __exit__: with 对象 自动执行__enter__ / __exit__

class Foo(object):    def __init__(self, a1, a2):        self.a1 = a1        self.a2 = a2    def __enter__(self):        print('1111')        return 999    def __exit__(self, exc_type, exc_val, exc_tb):        print('22222')obj = Foo(1,2)with obj as f:    print(f)    print('内部代码')

 

8.__new__: 构造方法

class Foo(object):    def __init__(self, a1, a2):     # 初始化方法        """        为空对象进行数据初始化        :param a1:        :param a2:        """        self.a1 = a1        self.a2 = a2    def __new__(cls, *args, **kwargs): # 构造方法        """        创建一个空对象        :param args:        :param kwargs:        :return:        """        return object.__new__(cls) # Python内部创建一个当前类的对象(初创时内部是空的.).obj1 = Foo(1,2)print(obj1)obj2 = Foo(11,12)print(obj2)