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|
- import collections
-
- from .cache import Cache
-
-
- class LFUCache(Cache):
- """Least Frequently Used (LFU) cache implementation."""
-
- def __init__(self, maxsize, getsizeof=None):
- Cache.__init__(self, maxsize, getsizeof)
- self.__counter = collections.Counter()
-
- def __getitem__(self, key, cache_getitem=Cache.__getitem__):
- value = cache_getitem(self, key)
- self.__counter[key] -= 1
- return value
-
- def __setitem__(self, key, value, cache_setitem=Cache.__setitem__):
- cache_setitem(self, key, value)
- self.__counter[key] -= 1
-
- def __delitem__(self, key, cache_delitem=Cache.__delitem__):
- cache_delitem(self, key)
- del self.__counter[key]
-
- def popitem(self):
- """Remove and return the `(key, value)` pair least frequently used."""
- try:
- (key, _), = self.__counter.most_common(1)
- except ValueError:
- msg = '%s is empty' % self.__class__.__name__
- raise KeyError(msg) from None
- else:
- return (key, self.pop(key))
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