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57 lines
1.7 KiB
Python
57 lines
1.7 KiB
Python
# Copyright 2021 Collate
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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# http://www.apache.org/licenses/LICENSE-2.0
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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"""
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LRU cache
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"""
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from collections import OrderedDict
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LRU_CACHE_SIZE = 4096
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class LRUCache:
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"""Least Recently Used cache"""
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def __init__(self, capacity: int) -> None:
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self._cache = OrderedDict()
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self.capacity = capacity
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def get(self, key):
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"""
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Returns the value associated to `key` if it exists,
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updating the cache usage.
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Raises `KeyError` if `key doesn't exist in the cache.
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"""
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self._cache.move_to_end(key)
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return self._cache[key]
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def put(self, key, value) -> None:
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"""
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Assigns `value` to `key`, overwriting `key` if it already exists
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in the cache and updating the cache usage.
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If the size of the cache grows above capacity, pops the least used
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element.
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"""
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self._cache[key] = value
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self._cache.move_to_end(key)
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if len(self._cache) > self.capacity:
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self._cache.popitem(last=False)
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def __contains__(self, key) -> bool:
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if key not in self._cache:
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return False
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self._cache.move_to_end(key)
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return True
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def __len__(self) -> int:
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return len(self._cache)
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