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)