python实现双向链表

class Node:
    """链表节点"""
    def __init__(self, val, prev=None, next_=None):
        self.val = val
        self.prev = prev
        self.next_ = next_

    def __repr__(self):
        return str(self.val)


class DoubleLinkedList:
    """双向链表"""
    def __init__(self):
        self.head = Node("head")
        self.tail = Node("tail")
        self.head.next_ = self.tail
        self.tail.prev = self.head
        self.size = 0

    def append(self, node):
        tail_node = self.tail.prev
        node.prev = tail_node
        node.next_ = tail_node.next_
        tail_node.next_ = node
        node.next_.prev = node
        self.size += 1

    def delete(self, node):
        prev = node.prev
        next_ = node.next_
        prev.next_ = next_
        next_.prev = prev
        self.size -= 1


if __name__ == '__main__':
    # 创建双向链表
    double_linked_list = DoubleLinkedList()
    # 增加三个元素
    double_linked_list.append(Node(110))
    double_linked_list.append(Node(120))
    double_linked_list.append(Node(119))
    # 删除一个元素
    double_linked_list.delete(double_linked_list.tail.prev.prev)
    # 从头部获取元素或从尾部获取元素
    print(double_linked_list.head.next_.next_)
    print(double_linked_list.tail.prev.prev)