Python单链表的简单实现方法

class LinkedList(object):
  
  class Element(object):
    
    def __init__(self,list,datum,next): 
      self._list = list
      self._datum = datum 
      self._next = next

    def getDatum(self): 
      return self._datum

    datum = property(
      fget = lambda self: self.getDatum())

    def getNext(self):
      return self._next

    next = property(
      fget = lambda self: self.getNext())

  def __init__(self):

    self._head = None
    self._tail = None
  def getHead(self):
    return self._head 
  head = property(
    fget = lambda self: self.getHead()) 
  def prepend(self,item):
    tmp = self.Element (self,item,self._head)
    if self._head is None:
      self._tail = tmp 
    self._head = tmp 

  def insert(self, pos, item):
    i = 0
    p = self._head
    while p != None and i < pos -1:
      p = p._next
      i += 1
    if p == None or i > pos-1:
      return -1
    tmp = self.Element(self, item, p._next)
    p._next = tmp
    return 1
  def getItem(self, pos):
    i = 0
    p = self._head
    while p != None and i < pos -1:
      p = p._next
      i += 1
    if p == None or i > post-1:
      return -1
    return p._datum
  def delete(self, pos):
    i = 0
    p = self._head
    while p != None and i < pos -1:
      p = p._next
      i += 1
    if p == None or i > post-1:
      return -1
    q = p._next
    p._nex = q._next
    datum = p._datum
    return datum
  def setItem(self, pos, item):
    i = 0
    p = self._head
    while p != None and i < pos -1:
      p = p._next
      i += 1
    if p == None or i > post-1:
      return -1
    p._datum = item
    return 1
  def find(self, pos, item):
    i = 0
    p = self._head
    while p != None and i < pos -1:
      if p._datum == item:
        return 1
      p = p._next
      i += 1
    return -1
  def empty(self):
    if self._head == None:
      return 1
    return 0
  def size(self):
    i = 0
    p = self._head
    while p != None and i < pos -1:
      p = p._next
      i += 1
    return i

  def clear(self):
    self._head = None
    self._tail = None

test = LinkedList()
test.prepend('test0')
print test.insert(1, 'test')
print test.head.datum
print test.head.next.datum