python列表操作实例

本文实例讲述了python列表操作的方法。分享给大家供大家参考。

具体实现方法如下：

class node:
   """single node in a data structure"""
 
   def __init__(self, data):
      """node constructor"""
      
      self._data = data
      self._nextnode = none
    
   def __str__(self):
      """node data representation"""
 
      return str(self._data)    
 
class list:
   """linked list"""
 
   def __init__(self):
      """list constructor"""
 
      self._firstnode = none
      self._lastnode = none
 
   def __str__(self):
      """list string representation"""
 
      if self.isempty():
         return "empty"
 
      currentnode = self._firstnode
      output = []
 
      while currentnode is not none:
         output.append(str(currentnode._data))
         currentnode = currentnode._nextnode
 
      return " ".join(output)    
 
   def insertatfront(self, value):
      """insert node at front of list"""
 
      newnode = node(value)
 
      if self.isempty():  # list is empty
         self._firstnode = self._lastnode = newnode
      else:   # list is not empty
         newnode._nextnode = self._firstnode
         self._firstnode = newnode
        
   def insertatback(self, value):
      """insert node at back of list"""
 
      newnode = node(value)
 
      if self.isempty():  # list is empty
         self._firstnode = self._lastnode = newnode
      else:  # list is not empty
         self._lastnode._nextnode = newnode
         self._lastnode = newnode
 
   def removefromfront(self):
      """delete node from front of list"""
 
      if self.isempty():  # raise exception on empty list
         raise indexerror, "remove from empty list"
 
      tempnode = self._firstnode
 
      if self._firstnode is self._lastnode:  # one node in list
         self._firstnode = self._lastnode = none
      else:
         self._firstnode = self._firstnode._nextnode
 
      return tempnode
 
   def removefromback(self):
      """delete node from back of list"""
 
      if self.isempty():  # raise exception on empty list
         raise indexerror, "remove from empty list"
     
      tempnode = self._lastnode
 
      if self._firstnode is self._lastnode:  # one node in list
         self._firstnode = self._lastnode = none
      else:
         currentnode = self._firstnode
 
         # locate second-to-last node
         while currentnode._nextnode is not self._lastnode:
               currentnode = currentnode._nextnode
               
         currentnode._nextnode = none
         self._lastnode = currentnode
 
      return tempnode
    
   def isempty(self):
      """returns true if list is empty"""
 
      return self._firstnode is none

希望本文所述对大家的python程序设计有所帮助。