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util.py
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util.py
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from __future__ import unicode_literals
"""
QGIS SQL function for looking up data in another table:
utility functions
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
"""
import time
class memoized(object):
"""
memoization with time limit (in s)
"""
def __init__(self,ttl=2):
self.cache={}
self.ttl=ttl
def __call__(self, func):
def _memoized(*args):
self.func = func
now = time.time()
try:
value,last_update=self.cache[args]
age = now - last_update
if age > self.ttl:
raise AttributeError
return value
except(KeyError, AttributeError):
value = self.func(*args)
self.cache[args]=(value,now)
return value
except TypeError:
return self.func(*args)
return _memoized