# -*- coding: utf-8 -*-
"""A decorator for caching properties in classes.
Copyright (c) 2015, Daniel Greenfeld
All rights reserved.
Redistribution and use in source and binary forms, with or without modification,
are permitted provided that the following conditions are met:
* Redistributions of source code must retain the above copyright notice,
this list of conditions and the following disclaimer.
* Redistributions in binary form must reproduce the above copyright notice,
this list of conditions and the following disclaimer in the documentation
and/or other materials provided with the distribution.
* Neither the name of cached-property nor the names of its contributors may be
used to endorse or promote products derived from this software without specific
prior written permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
"""
__author__ = 'Daniel Greenfeld'
__email__ = 'pydanny@gmail.com'
__version__ = '1.4.0'
__license__ = 'BSD'
from time import time
try:
import asyncio
except ImportError:
asyncio = None
[docs]class cached_property(object):
"""
A property that is only computed once per instance and then replaces itself
with an ordinary attribute. Deleting the attribute resets the property.
Source: https://github.com/bottlepy/bottle/commit/fa7733e075da0d790d809aa3d2f53071897e6f76
""" # noqa
def __init__(self, func):
self.__doc__ = getattr(func, '__doc__')
self.func = func
def __get__(self, obj, cls):
if obj is None:
return self
if asyncio and asyncio.iscoroutinefunction(self.func):
return self._wrap_in_coroutine(obj)
value = obj.__dict__[self.func.__name__] = self.func(obj)
return value
def _wrap_in_coroutine(self, obj):
@asyncio.coroutine
def wrapper():
future = asyncio.ensure_future(self.func(obj))
obj.__dict__[self.func.__name__] = future
return future
return wrapper()
[docs]class cached_property_with_ttl(object):
"""
A property that is only computed once per instance and then replaces itself
with an ordinary attribute. Setting the ttl to a number expresses how long
the property will last before being timed out.
"""
def __init__(self, ttl=None):
if callable(ttl):
func = ttl
ttl = None
else:
func = None
self.ttl = ttl
self._prepare_func(func)
def __call__(self, func):
self._prepare_func(func)
return self
def __get__(self, obj, cls):
if obj is None:
return self
now = time()
obj_dict = obj.__dict__
name = self.__name__
try:
value, last_updated = obj_dict[name]
except KeyError:
pass
else:
ttl_expired = self.ttl and self.ttl < now - last_updated
if not ttl_expired:
return value
value = self.func(obj)
obj_dict[name] = (value, now)
return value
def __delete__(self, obj):
obj.__dict__.pop(self.__name__, None)
def __set__(self, obj, value):
obj.__dict__[self.__name__] = (value, time())
def _prepare_func(self, func):
self.func = func
if func:
self.__doc__ = func.__doc__
self.__name__ = func.__name__
self.__module__ = func.__module__
# Aliases to make cached_property_with_ttl easier to use
cached_property_ttl = cached_property_with_ttl
timed_cached_property = cached_property_with_ttl