Python扩展内置类型详解

#File setwrapper.py  class Set:   def __init__(self,value=[]):#构造函数     self.data = []     self.concat(value)   def intersect(self,other):#求交集     res = []     for x in self.data:       if x in other:         res.append(x)     return Set(res) #返回一个新的Set    def union(self,other):#求并集     res = self.data[:] #复制self.data     for x in other:       if not x in res:         res.append(x)     return Set(res)    def concat(self,value):     for x in value:       if not x in self.data:         self.data.append(x)    def __len__(self): # len(self)     return len(self.data)     def __getitem__(self,key): # self[i]     return self.data[key]    def __and__(self,other): # self & other     return self.intersect(other)     def __or__(self,other): # self | other     return self.union(other)    def __repr__(self): # print     return 'Set:' + repr(self.data)  if __name__ == '__main__': #测试用例   x = Set([1,3,5,7])   print(x.union(Set([1,4,7])))   print(x | Set([1,4,6]))   print(x[2])   print(x[2:4]) 

# File typesubclass.py #Map 1..N to 0..N-1; call back to built-in version  class MyList(list):   def __getitem__(self,offset):     print('(indexing %s at %s)'%(self,offset))     return list.__getitem__(self,offset-1)  if __name__ == '__main__':   print(list('abc'))   x = MyList('abc')   print(x)    print(x[1])   print(x[3])   x.append('spam')   print(x)   x.reverse()   print(x)