| 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 | |