双向链表的插入和删除代码

1. 双向链表的插入代码：

class Node:
    def __init__(self, data):
        self.data = data
        self.next = None
        self.prev = None
 
class DoublyLinkedList:
    def __init__(self):
        self.head = None
 
    def push(self, new_data):
        new_node = Node(new_data)
        new_node.next = self.head
        if self.head is not None:
            self.head.prev = new_node
        self.head = new_node
 
    def insertAfter(self, prev_node, new_data):
        if prev_node is None:
            return
        new_node = Node(new_data)
        new_node.next = prev_node.next
        prev_node.next = new_node
        new_node.prev = prev_node
        if new_node.next is not None:
            new_node.next.prev = new_node
 
    def append(self, new_data):
        new_node = Node(new_data)
        new_node.next = None
        if self.head is None:
            new_node.prev = None
            self.head = new_node
            return
        last = self.head
        while last.next:
            last = last.next
        last.next = new_node
        new_node.prev = last
        return
 
    def printList(self, node):
        while node is not None:
            print(node.data),
            node = node.next

上述代码中，DoublyLinkedList类有三种插入方式，分别是push(), insertAfter()和append()方法，分别用于在链表头部、指定节点后和链表尾部插入节点。

2. 双向链表的删除代码：

class Node:
    def __init__(self, data):
        self.data = data
        self.next = None
        self.prev = None
 
class DoublyLinkedList:
    def __init__(self):
        self.head = None
 
    def push(self, new_data):
        new_node = Node(new_data)
        new_node.next = self.head
        if self.head is not None:
            self.head.prev = new_node
        self.head = new_node
 
    def deleteNode(self, dele):
        if self.head is None or dele is None:
            return
        if self.head == dele:
            self.head = dele.next
        if dele.next is not None:
            dele.next.prev = dele.prev
        if dele.prev is not None:
            dele.prev.next = dele.next
 
    def printList(self, node):
        while node is not None:
            print(node.data),
            node = node.next

上述代码中，DoublyLinkedList类有一个deleteNode()方法，用于删除指定节点。通过该方法实现双向链表的删除操作。