python实现LRU热点缓存及原理

class LRUCaceh():
   def __init__(self, size=5):
     '''
     默认队列的长度为5
     使用列表来维护，使用字典来查询
     '''
     self.size = size
     self.cache = dict()
     self.key = []
 ​
   def get(self, key):
     '''
     获取缓存中的key的值
     '''
     if self.cache.get(key):
       self.key.remove(key)
       self.key.insert(0, key)
       return self.cache[key]
     return None
 ​
   def set(self, key, value):
     '''
     设置缓存，实现缓存淘汰
     '''
     if self.cache.get(key):
       self.cache.pop(key)
       self.cache[key] = value
       self.key.remove(key)
       self.key.insert(0, key)
     elif len(self.key) == self.size:
       old_key = self.key.pop()
       self.key.insert(0, key)
       self.cache.pop(old_key)
       self.cache[key] = value
     else:
       self.key.insert(0, key)
       self.cache[key] = value