1 from collections import UserList 2 class MthChianList(UserList): 3     def filter(self,predicste): 4         return MthChianList(elem for elem in self if predicste(elem)) 5     def map(self,mapper): 6         return MthChianList(mapper(elem) for elem in self) 7     def for_each(self,action): 8         for elem in self: 9             action(elem)10 lt=MthChianList(['A','B','c','d','e','F'])11 lt.filter(str.islower).map(str.upper).for_each(print)