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import random
from .cache import Cache
# random.choice cannot be pickled in Python 2.7
def _choice(seq):
return random.choice(seq)
class RRCache(Cache):
"""Random Replacement (RR) cache implementation."""
def __init__(self, maxsize, choice=random.choice, getsizeof=None):
Cache.__init__(self, maxsize, getsizeof)
# TODO: use None as default, assing to self.choice directly?
if choice is random.choice:
self.__choice = _choice
else:
self.__choice = choice
@property
def choice(self):
"""The `choice` function used by the cache."""
return self.__choice
def popitem(self):
"""Remove and return a random `(key, value)` pair."""
try:
key = self.__choice(list(self))
except IndexError:
raise KeyError("%s is empty" % type(self).__name__) from None
else:
return (key, self.pop(key))
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