"""定义节点"""
class Node():def __init__(self, item):self.item = itemself.next = None"""定义单向链表"""
class SingleList():"""将头指针设为链表的私有属性"""def __init__(self, node=None):self.__head = node"""判断是否为空"""def is_Empty(self):return self.__head == None"""链表长度,通过遍历获得需要考虑特殊情况：链表为空时是否能够正确执行"""def get_length(self):cur = self.__headcount = 0while cur != None:count += 1cur = cur.nextreturn countdef traver(self):cur = self.__headwhile cur != None:print(cur.item, end=" ")cur = cur.nextprint()"""头部添加元素需要考虑特殊情况：链表为空时是否能够正确执行"""def addFirst(self, item):node = Node(item)node.next = self.__headself.__head = node"""尾部添加元素,首先需要遍历找到最后一个元素需要考虑特殊情况：链表为空时是否能够正确执行"""def addLast(self, item):node = Node(item)cur = self.__headif cur == None:self.__head = nodeelse:while cur.next != None:cur = cur.nextcur.next = node"""在指定位置添加元素，先找到添加的位置需要考虑特殊情况：在头部和尾部以及为空时能否正确执行"""def insert(self, index, item):if index <= 0:self.addFirst(item)elif index >= self.get_length():self.addLast(item)else:node = Node(item)cur = self.__headcount = 1while count < index:cur = cur.nextcount += 1node.next = cur.nextcur.next = node"""查找元素注意链表为空的特殊情况"""def find(self, item):if self.is_Empty():print("链表为空，无法查找")returncur = self.__headi = 0while cur.next != None and not cur.item == item:cur = cur.nexti += 1                   if cur.item == item:return("找到了，元素%s在%d处" %(item, i))else:return("没找到")"""删除指定位置元素"""def remove(self, index):if self.is_Empty():print("链表为空，无法删除")returnif index < 0 or index > self.get_length():print("索引越界，请检查!")returncur = self.__headpre = Nonecount = 0if index == 0:self.__head = cur.nextreturnelse:    while count != index:pre = curcur = pre.nextcount += 1pre.next = cur.nextreturnif __name__ == "__main__":sl = SingleList()print(sl.is_Empty())sl.find(7)sl.insert(0,9)sl.traver()sl.addFirst(1)sl.traver()sl.addLast(2)sl.addLast(3)sl.addLast(4)sl.addLast(5)sl.addLast(6)sl.traver()sl.insert(-2, 21)sl.traver()sl.insert(20, 25)sl.traver()sl.insert(0, 15)sl.traver()sl.insert(2, 17)sl.traver()print(sl.find(7))print(sl.find(6))sl.remove(3)sl.traver()sl.remove(0)sl.traver()sl.remove(-1)sl.traver()sl.remove(20)sl.traver()

True
链表为空，无法查找
9
1 9
1 9 2 3 4 5 6
21 1 9 2 3 4 5 6
21 1 9 2 3 4 5 6 25
15 21 1 9 2 3 4 5 6 25
15 21 17 1 9 2 3 4 5 6 25
没找到
找到了，元素6在9处
15 21 17 9 2 3 4 5 6 25
21 17 9 2 3 4 5 6 25
索引越界，请检查!
21 17 9 2 3 4 5 6 25
索引越界，请检查!
21 17 9 2 3 4 5 6 25