类的特殊成员

class Foo:
    def __new__(cls, *args, **kwargs):
        print('先执行的是我,创建空对象')
        return object.__new__(cls)
    def __init__(self,a,b):
        print('我是第二步,初始化数据')
        self.a=a
        self.b=b
    def __call__(self, *args, **kwargs):
        return args,kwargs
    def __getitem__(self, item):
        return item
    def __setitem__(self, key, value):
        print(key,value)
    def __delitem__(self, key):
        print(key)
    def __add__(self, other):
        return self.a+other.b
    def __enter__(self):
        print('hollo')
    def __exit__(self, exc_type, exc_val, exc_tb):
        print('get out')
    def __iter__(self):
        return [1,2,3,4,5]  #返回迭代器
    # def __iter__(self):   
    #     yield 1           #也可以返回一个生成器
    #     yield 2
obj=Foo(1,100)      #创建
print(obj.__dict__) #以字典的形式获取对象init方法封装的数据
print(obj(1,2,3,lyd=1000000))
print(obj[666])
obj[666]='very_good'
del obj[666]
obj2=Foo(-1,-100)
print(obj+obj2)
with obj as f:      #语法像with open
    print('我轻轻的走来')
    print('不带走一片云彩')
for item in obj:
    print(item)