80 lines
2.4 KiB
Python
80 lines
2.4 KiB
Python
# -*- coding: utf-8 -*-
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__author__ = 'Daniel Greenfeld'
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__email__ = 'pydanny@gmail.com'
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__version__ = '1.0.0'
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__license__ = 'BSD'
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from time import time
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import threading
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class cached_property(object):
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""" A property that is only computed once per instance and then replaces
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itself with an ordinary attribute. Deleting the attribute resets the
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property.
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Source: https://github.com/bottlepy/bottle/commit/fa7733e075da0d790d809aa3d2f53071897e6f76
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""" # noqa
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def __init__(self, ttl=None):
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ttl_or_func = ttl
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self.ttl = None
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if callable(ttl_or_func):
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self.prepare_func(ttl_or_func)
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else:
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self.ttl = ttl_or_func
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def prepare_func(self, func, doc=None):
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'''Prepare to cache object method.'''
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self.func = func
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self.__doc__ = doc or func.__doc__
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self.__name__ = func.__name__
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self.__module__ = func.__module__
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def __call__(self, func, doc=None):
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self.prepare_func(func, doc)
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return self
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def __get__(self, obj, cls):
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if obj is None:
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return self
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now = time()
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try:
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value, last_update = obj._cache[self.__name__]
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if self.ttl and self.ttl > 0 and now - last_update > self.ttl:
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raise AttributeError
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except (KeyError, AttributeError):
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value = self.func(obj)
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try:
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cache = obj._cache
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except AttributeError:
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cache = obj._cache = {}
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cache[self.__name__] = (value, now)
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return value
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def __delattr__(self, name):
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print(name)
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class threaded_cached_property(cached_property):
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""" A cached_property version for use in environments where multiple
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threads might concurrently try to access the property.
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"""
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def __init__(self, ttl=None):
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super(threaded_cached_property, self).__init__(ttl)
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self.lock = threading.RLock()
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def __get__(self, obj, cls):
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with self.lock:
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# Double check if the value was computed before the lock was
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# acquired.
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prop_name = self.__name__
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if hasattr(obj, '_cache') and prop_name in obj._cache:
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return obj._cache[prop_name][0]
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# If not, do the calculation and release the lock.
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return super(threaded_cached_property, self).__get__(obj, cls)
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