# encoding=utf-8class Node(object):"""节点类"""def __init__(self, item):"""初始化函数:param item: 　要保存的用户数据"""self.item = itemself.next = Noneclass SingleLinkList(object):"""单链表"""def __init__(self, node=None):"""初始化函数r:param node: 可传可不传的头节点"""# 指向头节点self.__head = nodedef is_empty(self):"""链表是否为空"""return self.__head is Nonedef length(self):"""链表长度"""current = self.__headcount = 0while current is not None:count += 1current = current.nextreturn countdef travel(self):"""遍历整个链表 要考虑空链表如果是空链表判断条件不成立也就不输出任何信息"""current = self.__headwhile current is not None:print(current.item, end="")current = current.nextprint("")  # 多输出换行def add(self, item):""""在链表头部插入元素"""node = Node(item)node.next = self.__headself.__head = nodedef append(self, item):""""在链表尾部插入节点"""node = Node(item)cur = self.__headif cur is None:self.add(item)returnwhile cur.next is not None:cur = cur.nextcur.next = nodedef insert(self, pos, item):"""指定位置添加元素"""# 在头结点插入元素if pos <=0:self.add(item)# 在链表的尾部添加元素elif pos >= self.length():self.append(item)# 在链表的任意位置添加元素else:cur = self.__headcount = 0# 找到添加位置的前一个位置while count < (pos-1):count += 1cur = cur.nextnode = Node(item)node.next = cur.nextcur.next = nodedef remove(self, item):"""删除节点:param item:　要删除的元素:return:"""cur = self.__headpre = Nonewhile cur is not None:# 找到了元素if cur.item == item:# 在头部找到了元素if cur == self.__head:self.__head = cur.nextelse:pre.next = cur.nextreturnpre = curcur = cur.nextdef search(self, item):"""查找节点是否存在:param item: 要查找的element:return:"""cur = self.__headwhile cur is not None:if cur.item == item:return Truecur = cur.nextreturn Falseif __name__ == '__main__':ll = SingleLinkList()print(ll.length())ll.append(1)   # 1print(ll.length())ll.travel()ll.append(2)   #1 2print(ll.length())ll.travel()ll.add(3)   # 3 1 2
    ll.travel()ll.add(4) # 4 3 1 2
    ll.travel()ll.insert(0, 5)  # 5 4 3 1 2
    ll.travel()ll.insert(10, 6)  # 5 4 3 1 2  6
    ll.travel()ll.insert(3, 7)  # 5 4 3  7 1 2  6
    ll.travel()ll.remove(5)  #  4 3  7 1 2  6)
    ll.travel()ll.remove(6)  #  4 3  7 1 2
    ll.travel()ll.remove(7)  #  4 3  1 2
    ll.travel()ll.remove(4)  #  3  1 2
    ll.travel()ll.remove(3)  #   1 2
    ll.travel()ll.remove(1)  #  2
    ll.travel()ll.remove(2)ll.travel()