模拟缓存双端循环链式数据结构

核心思想是通过节节点的概念，存储每一个节点上一个节点和下一个节点的内存地址，然后每个节点中存储该节点的创建时间，每次取值判断，如果超出了自己设定的缓存时常，则清除节点。

import datetime

class Node:
def __init__(self,value=None,next=None,prev=None,time=None):
self.value,self.next,self.prev,self.time=value,next,prev,time

class Bag:
def __init__(self,maxsize=None):
self.root = Node()
self.root.next=self.root
self.root.prev=self.root
self.maxsize = None
self.tailnode = self.root
self.headnode = self.root
self.length = 0

def __len__(self):
self.remove_by_time()
return self.length

def remove_by_time(self):
curnode = self.root
lis = []
while True:
curnode = curnode.next
if curnode == self.root:
break
if datetime.datetime.now() - curnode.time > datetime.timedelta(seconds=60):
lis.append(curnode.value)
for i in lis:
self.remove(i)

def append(self,value):
if self.maxsize is not None and self.length>=self.maxsize:
raise Exception("Full")

node=Node(value=value,time=datetime.datetime.now())

if self.tailnode == self.root:
self.root.next=node
node.prev = self.root
self.headnode=node
else:
node.prev=self.tailnode
self.tailnode.next=node

self.tailnode=node
self.root.prev = node
node.next = self.root

self.length+=1

def appendleft(self,value):
if self.maxsize is not None and self.length>=self.maxsize:
raise Exception("Full")

node=Node(value=value,time=datetime.datetime.now())

if self.tailnode==self.root:
self.root.prev=node
node.next=self.root
self.tailnode=node
else:
node.next = self.headnode
self.headnode.prev=node

self.headnode = node
self.root.next = node
node.prev = self.root

self.length+=1

def iter_node(self):
curnode = self.root
while True:
curnode = curnode.next
if curnode == self.root:
break
yield curnode

def __iter__(self):
self.remove_by_time()
for i in self.iter_node():
yield i.value

def remove(self,value):
for i in self.iter_node():
if i.value == value:
if i==self.headnode:
self.headnode=i.next
if i==self.tailnode:
self.tailnode=i.prev
i.next.prev, i.prev.next = i.prev, i.next
self.length -= 1
return i
return -1