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from collections import OrderedDict
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from typing import Dict, Generic, TypeVar
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CacheKey = TypeVar("CacheKey")
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CacheValue = TypeVar("CacheValue")
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class LRUCache(Generic[CacheKey, CacheValue], OrderedDict): # type: ignore # https://github.com/python/mypy/issues/6904
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"""
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A dictionary-like container that stores a given maximum items.
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If an additional item is added when the LRUCache is full, the least
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recently used key is discarded to make room for the new item.
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"""
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def __init__(self, cache_size: int) -> None:
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self.cache_size = cache_size
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super(LRUCache, self).__init__()
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def __setitem__(self, key: CacheKey, value: CacheValue) -> None:
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"""Store a new views, potentially discarding an old value."""
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if key not in self:
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if len(self) >= self.cache_size:
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self.popitem(last=False)
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OrderedDict.__setitem__(self, key, value)
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def __getitem__(self: Dict[CacheKey, CacheValue], key: CacheKey) -> CacheValue:
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"""Gets the item, but also makes it most recent."""
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value: CacheValue = OrderedDict.__getitem__(self, key)
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OrderedDict.__delitem__(self, key)
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OrderedDict.__setitem__(self, key, value)
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return value
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