Python的魔法函数之 - __len__,__getitem__,__setitem__,__delitem__

# 对象作为len()函数的参数是必须实现该方法
__len__
# 使用类似字典方式访问成员时必须实现 dic['pro_name']
__getitem__
# 使用类似字典方式设置成员时必须实现 dic['pro_name']='asdf'
__setitem__
# 使用类似字典方式删除成员时必须实现 delete dic['pro_name']
__delitem__

class DictDemo:  
    def __init__(self,key,value):  
        self.dict = {}  
        self.dict[key] = value  
    def __getitem__(self,key):  
        return self.dict[key]  
    def __setitem__(self,key,value):  
        self.dict[key] = value  
    def __len__(self):  
        return len(self.dict)  
dictDemo = DictDemo('key0','value0')  
print(dictDemo['key0']) #value0  
dictDemo['key1'] = 'value1'  
print(dictDemo['key1']) #value1  
print(len(dictDemo)) #2  

http://blog.csdn.net/yuan_j_y/article/details/9317817