from collections import OrderedDict
from typing import Dict, Generic, TypeVar
CacheKey = TypeVar("CacheKey")
CacheValue = TypeVar("CacheValue")
class LRUCache(Generic[CacheKey, CacheValue], OrderedDict):
"""
A dictionary-like container that stores a given maximum items.
If an additional item is added when the LRUCache is full, the least
recently used key is discarded to make room for the new item.
"""
def __init__(self, cache_size: int) -> None:
self.cache_size = cache_size
super(LRUCache, self).__init__()
def __setitem__(self, key: CacheKey, value: CacheValue) -> None:
"""Store a new views, potentially discarding an old value."""
if key not in self:
if len(self) >= self.cache_size:
self.popitem(last=False)
OrderedDict.__setitem__(self, key, value)
def __getitem__(self: Dict[CacheKey, CacheValue], key: CacheKey) -> CacheValue:
"""Gets the item, but also makes it most recent."""
value: CacheValue = OrderedDict.__getitem__(self, key)
OrderedDict.__delitem__(self, key)
OrderedDict.__setitem__(self, key, value)
return value
