单向链表的创建和操作（python）

class :
    def __init__(self,data):
        self.data=data
        self.next=None
        return
# 创建单向链表
class singlelinklist():
    # 初始化链表
    def __init__(self):
        self.head=None
        self.tail=None
        return
    # 增加节点
    def add_list_node(self,item):
        if not isinstance (item,Node):
            item=Node(item)
        if self.head is None:
            self.head=item
        else:
            self.tail.next=item
        self.tail=item
        return
    # 统计链表长度
    def list_length(self):
        count=0
        current_node=self.head
        while current_node is not None:
            count=count+1
            current_node=current_node.next
        return count
    # 输出链表
    def output_list(self):
        current_node=self.head
        while current_node is not None:
            print(current_node.data)
            current_node=current_node.next
        return
node1=Node(15)
node2=Node(8.2)
item3="berlin"
node4=Node(15)
track=singlelinklist()
for element in [node1,node2,item3,node4]:
    track.add_list_node(element)
    print(track.list_length())
print(track.output_list())