python实现链表

class Node():
    def __init__(self,value=None,next=None):
        self._value=value
        self._next=next

    def getValue(self):
        return self._value

    def getNext(self):
        return self._next

    def setValue(self,new_value):
        self._value=new_value

    def setNext(self,new_next):
        self._next=new_next

class LinkedList():
    def __init__(self):
        self._head=Node()
        self._tail=None
        self._length=0

    def isEmpty(self):
        return self._head==None

    def add(self,value):
        '''
        在表前端添加元素
        :param value: 添加元素的值
        :return:
        '''
        newnode=Node(value,None)
        newnode.setNext(self._head)
        self._head=newnode

    def append(self,value):
        '''
        在链表的尾部添加元素
        :param value:
        :return:
        '''
        newnode=Node(value)
        if self.isEmpty():
            self._head=newnode
        else:
            current=self._head
            while current.getNext()!=None:
                current=current.getNext()
            current.setNext(newnode)

    def search(self,value):
        '''
        查找链表中是否有该元素
        :param value: 元素
        :return: True or False
        '''
        current=self._head
        while current!=None :
            if current.getValue()==value:
                return True
            else:
                current=current.getNext()
        return False

    def index(self,value):
        '''
        索引元素在列表中的位置
        :param value: 元素的值
        :return: 元素在列表中的索引
        '''
        current=self._head
        count=0
        while current!=None:
            if current.getValue()==value:
                return count
            else:
                count+=1
                current=current.getNext()
        return ValueError('%s is not in linkedlist'%value)

    def remove(self,value):
        '''
        删除链表第一个值为value的元素
        :param value:要删除的元素的值
        :return:
        '''
        current=self._head
        pre=None
        while current!=None:
            if current.getValue()==value:
                if not pre:
                    self._head=current.getNext()
                else:
                    pre.setNext(current.getNext)
                break
            else:
                pre=current
                current=current.getNext()

    def size(self):
        '''
        返回数组的长度
        :return: 数组的长度
        '''
        current=self._head
        count=0
        while current!=None:
            count+=1
            current=current.getNext()
        return count


    def insert(self,pos,value):
        '''
        在指定位置中插入元素
        :param pos: 插入位置
        :param value:插入的值
        :return:None
        '''
        if pos<=1:
            self.add(value)
        elif pos>self.size()-1:
            self.append(value)
        else:
            temp=Node(value)
            count=1
            pre=None
            current=self._head
            while count<pos:
                count+=1
                pre=current
                current=current.getNext()
            pre.setNext(temp)
            temp.setNext(current)