56 lines
1.5 KiB
Python
56 lines
1.5 KiB
Python
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from datetime import datetime
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class ExpiresEntry(object):
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""" A single entry under a ExpiresDict. """
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def __init__(self, value, expires=None):
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self.value = value
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self._expiration = expires
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@property
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def expired(self):
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if self._expiration is None:
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return False
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return datetime.now() >= self._expiration
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class ExpiresDict(object):
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""" ExpiresDict defines a dictionary-like class whose keys have expiration. The rebuilder is
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a function that returns the full contents of the cached dictionary as a dict of the keys
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and whose values are TTLEntry's.
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"""
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def __init__(self, rebuilder):
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self._rebuilder = rebuilder
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self._items = {}
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def __getitem__(self, key):
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found = self.get(key)
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if found is None:
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raise KeyError
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return found
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def get(self, key, default_value=None):
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# Check the cache first. If the key is found and it has not yet expired,
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# return it.
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found = self._items.get(key)
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if found is not None and not found.expired:
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return found.value
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# Otherwise the key has expired or was not found. Rebuild the cache and check it again.
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self._rebuild()
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found = self._items.get(key)
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if found is None:
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return default_value
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return found.value
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def __contains__(self, key):
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return self.get(key) is not None
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def _rebuild(self):
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self._items = self._rebuilder()
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def set(self, key, value, expires=None):
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self._items[key] = ExpiresEntry(value, expires=expires)
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