帮我用python写一个单链表的代码

好的，以下是单链表的 Python 代码：

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

class LinkedList:
def __init__(self):
self.head = None

def add_node(self, data):
new_node = Node(data)
if self.head is None:
self.head = new_node
return
last_node = self.head
while last_node.next:
last_node = last_node.next
last_node.next = new_node

def print_list(self):
current_node = self.head
while current_node:
print(current_node.data)
current_node = current_node.next

# 测试代码
linked_list = LinkedList()
linked_list.add_node(1)
linked_list.add_node(2)
linked_list.add_node(3)
linked_list.print_list()