| from collections import OrderedDict |
| from typing import Dict, Generic, TypeVar |
| |
| |
| CacheKey = TypeVar("CacheKey") |
| CacheValue = TypeVar("CacheValue") |
| |
| |
| class LRUCache(Generic[CacheKey, CacheValue], OrderedDict): # type: ignore # https://github.com/python/mypy/issues/6904 |
| """ |
| 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 |
