lru_cache.py

# lru cache:
# Problem: Implement a LRU Cache:

# - LRUCache(int capacity) Initialize the LRU cache with positive size capacity.
# - int get(int key) Return the value of the key if the key exists, otherwise return -1.
# - void put(int key, int value) Update the value of the key if the key exists. Otherwise, add the key-value pair to the cache. If the number of keys exceeds the capacity from this operation, evict the least recently used key.



from collections import OrderedDict

class LRU:
    def __init__(self, capacity):
        self.cache_dict = OrderedDict()
        self.capacity = capacity


    def get(self, key):
        if key is not in self.cache_dict:
            return -1
        
        else:
            self.cache_dict.move_to_end(key)
            return self.cache_dict[key]
    
    def put(self, key, value):
        self.cache_dict[key] = value
        self.cache_dict.move_to_end(key)
        if len(self.cache_dict) > self.capacity:
            self.cache_dict.popitem(last=False)

new_cache = LRU(10)

new_cache.put(3, 10) # O(1)
new_cache.get((3)) # 10 // O(1)
new_cache.get((6)) # -1