python 单项链表

class Node(object):
    def __init__(self, item):
        self.item = item
        self.next = None


class SingLink(object):
    def __init__(self, node=None):
        self.__head = node

    def length(self):
        count = 0
        cur_node = self.__head
        while cur_node != None:
            count += 1
            cur_node = cur_node.next
        return count

    def traverse(self):
        cur_node = self.__head
        while cur_node:
            print(cur_node.item, end=',')
            cur_node = cur_node.next
        print('')

    def append(self, ele):
        if ele is None:
            return None
        node = Node(ele)
        if self.__head == None:
            self.__head = node
            return node
        cur_node = self.__head
        while cur_node.next != None:
            cur_node = cur_node.next
        cur_node.next = node
        return node

    def add(self, ele):
        node = Node(ele)
        if self.__head:
            node.next = self.__head
            self.__head = node
        else:
            self.__head = node

    def insert(self, index, ele):
        count = 1
        cur = self.__head
        node = Node(ele)

        if index == 0:
            self.add(ele)
            return
        if index == 1:
            node.next = self.__head.next
            self.__head.next = node
            return

        if index < self.length():
            while True:
                cur = cur.next
                count += 1
                if count == index:
                    node.next = cur.next
                    cur.next = node
        else:
            self.append(ele)

    def delete(self, ele):

        cur = self.__head
        if cur.item == ele:
            self.__head= cur.next

        while cur:
            if cur.next:
                if cur.next.item == ele:
                    cur.next = cur.next.next
                    break
                cur = cur.next

            else:
                return

s = SingLink()
s.append('A')
s.append('B')
s.append('C')

s.traverse()

s.insert(0, 'D')
print(s.length())
s.traverse()
s.insert(10, 'F')
s.traverse()

s.delete("D")
s.delete("F")
s.delete("F")
s.traverse()