写一份python的单链表实现

好的，以下是 Python 单链表的实现：

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

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

def append(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 prepend(self, data):
new_node = Node(data)
new_node.next = self.head
self.head = new_node

def insert_after_node(self, prev_node, data):
if not prev_node:
print("Previous node is not in the list")
return
new_node = Node(data)
new_node.next = prev_node.next
prev_node.next = new_node

def delete_node(self, key):
cur_node = self.head
if cur_node and cur_node.data == key:
self.head = cur_node.next
cur_node = None
return
prev = None
while cur_node and cur_node.data != key:
prev = cur_node
cur_node = cur_node.next
if cur_node is None:
return
prev.next = cur_node.next
cur_node = None

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

# 测试
llist = LinkedList()
llist.append("A")
llist.append("B")
llist.append("C")
llist.append("D")
llist.print_list()
llist.prepend("E")
llist.print_list()
llist.insert_after_node(llist.head.next, "F")
llist.print_list()
llist.delete_node("B")
llist.print_list()