UserDict,UserList,UserString

UserDict,UserList,UserString，可继承的字典，列表，以及字符串类，可以对列表字典以及字符串内部方进行重写。
python3中这3个模块都移入到了collection库中，

#coding=utf-8
#userdict
from collections import UserDict,UserString,UserList


class MyUserDict(UserDict):
    def __getitem__(self, item):
        return self.data[item]*10
        #return 42

    def __add__(self, other):
       '''实现字典相加
       '''
        dict1=MyUserDict(self.data)
        if isinstance(other,MyUserDict):
            dict1.update(other)
        return dict1


class MyString(UserString):
    def lower(self):
        return self.data+'\n'+self.data

class MyUserList(UserList):

    def __add__(self, other):
        '''
        返回两个列表对应处相加，如[1,2,3]+[4,,5,6]=[5,7,9]
        :param other:
        :return:
        '''
        list1=[]
        for i,j in zip(self.data,other.data):
            list1.append(i+j)
        return list1

if __name__=='__main__':
    mydict=MyUserDict(a=12)
    mydict2=MyUserDict(b=120)
    # print(mydict.get('a'))
    print(mydict['a'])
    print(mydict+mydict2)        #{'a':12,'b':120}
    D = {'c': 300}
    print(MyUserDict(D)+mydict)
    print('*******************userstring***************')
    mystr=MyString('aaacc')
    print(mystr.lower())
    print('*******************userlist***************')

    mylist1=MyUserList([1,2])
    mylist2=MyUserList([3,4])
    print(mylist1+mylist2)           #[4,6]