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import random
from .cache import Cache
from .decorators import cachedfunc
from .lock import RLock
class RRCache(Cache):
"""Random Replacement (RR) cache implementation."""
def __init__(self, maxsize, choice=random.choice, missing=None,
getsizeof=None):
Cache.__init__(self, maxsize, missing, getsizeof)
self.__choice = choice
def popitem(self):
"""Remove and return a random `(key, value)` pair."""
try:
key = self.__choice(list(self))
except IndexError:
raise KeyError('cache is empty')
return (key, self.pop(key))
@property
def choice(self):
"""The `choice` function used by the cache."""
return self.__choice
def rr_cache(maxsize=128, choice=random.choice, typed=False, getsizeof=None,
lock=RLock):
"""Decorator to wrap a function with a memoizing callable that saves
up to `maxsize` results based on a Random Replacement (RR)
algorithm.
"""
return cachedfunc(RRCache(maxsize, choice, getsizeof), typed, lock)
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