我正试图为一个类的实例方法构建一个decorator,该类将记录结果。(这在以前已经做了一百万次了)但是,我希望能够在任何时候重置已记录的缓存(比如,如果实例状态中的某些内容发生更改,这可能会更改与参数无关的方法的结果)。因此,我尝试将decorator构建为类而不是函数,以便可以作为类成员访问缓存。这引导我沿着学习描述符的道路前进,特别是__get__
方法,这是我真正陷入困境的地方。我的代码看起来是这样的:
import time
class memoized(object):
def __init__(self, func):
self.func = func
self.cache = {}
def __call__(self, *args, **kwargs):
key = (self.func, args, frozenset(kwargs.iteritems()))
try:
return self.cache[key]
except KeyError:
self.cache[key] = self.func(*args, **kwargs)
return self.cache[key]
except TypeError:
# uncacheable, so just return calculated value without caching
return self.func(*args, **kwargs)
# self == instance of memoized
# obj == instance of my_class
# objtype == class object of __main__.my_class
def __get__(self, obj, objtype=None):
"""Support instance methods"""
if obj is None:
return self
# new_func is the bound method my_func of my_class instance
new_func = self.func.__get__(obj, objtype)
# instantiates a brand new class...this is not helping us, because it's a
# new class each time, which starts with a fresh cache
return self.__class__(new_func)
# new method that will allow me to reset the memoized cache
def reset(self):
print "IN RESET"
self.cache = {}
class my_class:
@memoized
def my_func(self, val):
print "in my_func"
time.sleep(2)
return val
c = my_class()
print "should take time"
print c.my_func(55)
print
print "should be instant"
print c.my_func(55)
print
c.my_func.reset()
print "should take time"
print c.my_func(55)
这清楚和/或可能吗?每次调用__get__
时,我都会得到一个新的memoided类实例,它会丢失包含实际数据的缓存。我一直在努力工作,但进展不大。
有没有一个完全独立的方法来解决我完全忽略的问题?欢迎并感谢所有的建议。谢谢。
目前没有回答
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