创建单链表

class Node():
    def __init__(self,item):
        self.item = item
        self.next = None
class Link():
    #构建出一个空的链表
    def __init__(self):
        self._head = None #永远指向链表中的头节点
        #想链表的头部插入节点
    def add(self,item):
        node = Node(item)
        node.next = self._head
        self._head = node
        
    def travel(self):   
        cur = self._head
        #链表为空则输出‘链表为空’
        if self._head == None:
            print('链表为空！')
        while cur:
            print(cur.item)
            cur = cur.next
    def isEmpty(self):
        return self._head == None
    def length(self):
        cur = self._head
        count = 0
        while cur:
            count += 1
            cur = cur.next
        return count          
    def search(self,item):
        cur = self._head
        find = False
        while cur:
            if cur.item == item:
                find = True
                break
            cur = cur.next
        return find
    
    def append(self,item):
        node = Node(item)
        #链表为空的情况
        if self._head == None:
            self._head = node
            return
        
        cur = self._head #头节点
        pre = None #cur的前一个节点
        while cur:
            pre = cur
            cur = cur.next
        pre.next = node
        
    def insert(self,pos,item):
        node = Node(item)
        
        if pos < 0 or pos > self.length():
            print('重新给pos赋值！！！')
            return
        
        cur = self._head
        pre = None
        
        for i in range(pos):
            pre = cur
            cur = cur.next
        pre.next = node
        node.next = cur
    def remove(self,item):
        cur = self._head
        pre = None
        
        if self._head == None:#链表为空
            print('链表为空，没有可删除的节点！！1')
            return
    
        
        #删除的是第一个节点的情况
        if self._head.item == item:
            self._head = self._head.next
            return
        
        #删除的是非第一个节点的情况
        while cur:
            pre = cur
            cur = cur.next
            if cur.item == item:
                pre.next = cur.next
                return
                
link = Link()
# link.add(3)
# link.add(4)
# link.add(5)
# link.add(6)

link.remove(3)

link.travel()

以上链表集成了增删查