# 節(jié)點類class Node():  __slots__=['_item','_next'] # 限定Node實例的屬性  def __init__(self,item):    self._item = item    self._next = None # Node的指針部分默認指向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# 單鏈表class SingleLinkedList():  def __init__(self):    self._head = None #初始化鏈表為空 始終指向鏈表的頭部    self._size = 0 # 鏈表大小  # 返回鏈表的大小  def size(self):    current = self._head    count = 0    while current != None:      count += 1      current = current.getNext()    return count  # 遍歷鏈表  def travel(self):    current = self._head    while current != None:      print(current.getItem())      current = current.getNext()  # 檢查鏈表是否為空  def isEmpty(self):    return self._head == None  # 在鏈表前端添加元素  def add(self,item):    temp = Node(item) # 創(chuàng)建新的節(jié)點    temp.setNext(self._head) # 新創(chuàng)建的next指針指向_head    self._head = temp # _head指向新創(chuàng)建的指針  # 在鏈表尾部添加元素  def append(self,item):    temp = Node(item)    if self.isEmpty():      self._head = temp # 若為空表就直接插入    else:      current = self._head      while current.getNext() != None:        current = current.getNext() # 遍歷列表      current.setNext(temp) # 此時current為鏈表最后的元素，在末尾插入  # 檢索元素是否在鏈表中  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  # 刪除表中的某項元素  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()  # 在鏈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('鏈表的大小',a.size())  a.travel()  print(a.search(6))  print(a.index(5))  a.remove(4)  a.travel()  a.insert(4,100)  a.travel()