Python数据结构--单链表

# 节点类class Node():    __slots__=['_item','_next'] # 限定Node实例的属性    def __init__(self,item):        self._item = item        self._next = None # Node的指针部分默认指向None    def getItem(self):        return self._item    def getNext(self):        return self._next    def setItem(self,newitem):        self._item = newitem    def setNext(self,newnext):        self._next=newnext# 单链表class SingleLinkedList():    def __init__(self):        self._head = None #初始化链表为空 始终指向链表的头部        self._size = 0 # 链表大小    # 返回链表的大小    def size(self):        current = self._head        count = 0        while current != None:            count += 1            current = current.getNext()        return count    # 遍历链表    def travel(self):        current = self._head        while current != None:            print(current.getItem())            current = current.getNext()    # 检查链表是否为空    def isEmpty(self):        return self._head == None    # 在链表前端添加元素    def add(self,item):        temp = Node(item) # 创建新的节点        temp.setNext(self._head) # 新创建的next指针指向_head        self._head = temp # _head指向新创建的指针    # 在链表尾部添加元素    def append(self,item):        temp = Node(item)        if self.isEmpty():            self._head = temp # 若为空表就直接插入        else:            current = self._head            while current.getNext() != None:                current = current.getNext() # 遍历列表            current.setNext(temp) # 此时current为链表最后的元素，在末尾插入    # 检索元素是否在链表中    def search(self,item):        current = self._head        founditem = False        while current != None and not founditem:            if current.getItem() == item:                founditem = True            else:                current = current.getNext()        return founditem    # 索引元素在表中的位置    def index(self,item):        current = self._head        count = 0        found = None        while current != None and not found:            count += 1            if current.getItem() == item:                found = True            else:                current = current.getNext()        if found:            return count        else:            return -1 # 返回-1表示不存在    # 删除表中的某项元素    def remove(self,item):        current = self._head        pre = None        while current!=None:            if current.getItem() == item:                if not pre:                    self._head = current.getNext()                else:                    pre.setNext(current.getNext())                break            else:                pre = current                current = current.getNext()    # 在链表任意位置插入元素    def insert(self,pos,item):        if pos <= 1:            self.add(item)        elif pos > self.size():            self.append(item)        else:            temp = Node(item)            count = 1            pre = None            current = self._head            while count < pos:                count += 1                pre = current                current = current.getNext()            pre.setNext(temp)            temp.setNext(current)if __name__=='__main__':    a=SingleLinkedList()    for i in range(1,10):        a.append(i)    print('链表的大小',a.size())    a.travel()    print(a.search(6))    print(a.index(5))    a.remove(4)    a.travel()    a.insert(4,100)    a.travel()