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https://github.com/wassname/catalyst.git
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Scott Sanderson
b766ce6ebd
Implements a `CachedObject` utility class for wrapping cached results with an expiration date.
60 lines
1.3 KiB
Python
60 lines
1.3 KiB
Python
"""
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Cached object with an expiration date.
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"""
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from collections import namedtuple
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class Expired(Exception):
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pass
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class CachedObject(namedtuple("_CachedObject", "value expires")):
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"""
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A simple struct for maintaining a cached object with an expiration date.
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Parameters
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----------
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value : object
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The object to cache.
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expires : datetime-like
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Expiration date of `value`. The cache is considered invalid for dates
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**strictly greater** than `expires`.
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Methods
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-------
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get(self, dt)
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Get the cached object.
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Usage
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-----
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>>> from pandas import Timestamp, Timedelta
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>>> expires = Timestamp('2014', tz='UTC')
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>>> obj = CachedObject(1, expires)
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>>> obj.unwrap(expires - Timedelta('1 minute'))
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1
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>>> obj.unwrap(expires)
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1
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>>> obj.unwrap(expires + Timedelta('1 minute'))
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Traceback (most recent call last):
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...
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Expired: 2014-01-01 00:00:00+00:00
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"""
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def unwrap(self, dt):
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"""
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Get the cached value.
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Returns
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-------
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value : object
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The cached value.
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Raises
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------
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Expired
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Raised when `dt` is greater than self.expires.
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"""
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if dt > self.expires:
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raise Expired(self.expires)
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return self.value
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