Python 学习:单链表的实现

要定义一个单链表,首先定义链表元素:Element.它包含3个字段:
list:标识自己属于哪一个list
datum:改元素的value
next:下一个节点的位置

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