132 lines
3.8 KiB
Python
132 lines
3.8 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__ = '1.3.0'
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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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"""
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A property that is only computed once per instance and then replaces itself
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with an ordinary attribute. Deleting the attribute resets the 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, func):
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self.__doc__ = getattr(func, '__doc__')
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self.func = func
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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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value = obj.__dict__[self.func.__name__] = self.func(obj)
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return value
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class threaded_cached_property(object):
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"""
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A cached_property version for use in environments where multiple threads
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might concurrently try to access the property.
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"""
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def __init__(self, func):
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self.__doc__ = getattr(func, '__doc__')
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self.func = func
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self.lock = threading.RLock()
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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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obj_dict = obj.__dict__
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name = self.func.__name__
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with self.lock:
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try:
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# check if the value was computed before the lock was acquired
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return obj_dict[name]
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except KeyError:
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# if not, do the calculation and release the lock
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return obj_dict.setdefault(name, self.func(obj))
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class cached_property_with_ttl(object):
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"""
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A property that is only computed once per instance and then replaces itself
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with an ordinary attribute. Setting the ttl to a number expresses how long
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the property will last before being timed out.
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"""
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def __init__(self, ttl=None):
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if callable(ttl):
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func = ttl
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ttl = None
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else:
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func = None
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self.ttl = ttl
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self._prepare_func(func)
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def __call__(self, func):
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self._prepare_func(func)
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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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obj_dict = obj.__dict__
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name = self.__name__
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try:
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value, last_updated = obj_dict[name]
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except KeyError:
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pass
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else:
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ttl_expired = self.ttl and self.ttl < now - last_updated
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if not ttl_expired:
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return value
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value = self.func(obj)
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obj_dict[name] = (value, now)
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return value
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def __delete__(self, obj):
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obj.__dict__.pop(self.__name__, None)
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def __set__(self, obj, value):
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obj.__dict__[self.__name__] = (value, time())
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def _prepare_func(self, func):
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self.func = func
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if func:
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self.__doc__ = func.__doc__
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self.__name__ = func.__name__
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self.__module__ = func.__module__
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# Aliases to make cached_property_with_ttl easier to use
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cached_property_ttl = cached_property_with_ttl
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timed_cached_property = cached_property_with_ttl
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class threaded_cached_property_with_ttl(cached_property_with_ttl):
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"""
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A cached_property version for use in environments where multiple threads
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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_with_ttl, 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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return super(threaded_cached_property_with_ttl, self).__get__(obj,
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cls)
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# Alias to make threaded_cached_property_with_ttl easier to use
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threaded_cached_property_ttl = threaded_cached_property_with_ttl
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timed_threaded_cached_property = threaded_cached_property_with_ttl
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