How to memoize/cache property access?

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On Dec 20, 5:02 pm, thebjorn <BjornSteinarFjeldPetter... at gmail.com>
wrote:
> I seem to be writing the following boilerplate/pattern quite
> frequently to avoid hitting the database until absolutely necessary ...

I use the following module:

$ cat cache.py
class cached(property):
    'Convert a method into a cached attribute'
    def __init__(self, method):
        private = '_' + method.__name__
        def fget(s):
            try:
                return getattr(s, private)
            except AttributeError:
                value = method(s)
                setattr(s, private, value)
                return value
        def fdel(s):
            del s.__dict__[private]
        super(cached, self).__init__(fget, fdel=fdel)
    @staticmethod
    def reset(self):
        cls = self.__class__
        for name in dir(cls):
            attr = getattr(cls, name)
            if isinstance(attr, cached):
                delattr(self, name)

if __name__ == '__main__': # a simple test
    import itertools
    counter = itertools.count()
    class Test(object):
        @cached
        def foo(self):
            return counter.next()
        reset = cached.reset

    p = Test()
    print p.foo
    print p.foo
    p.reset()
    print p.foo
    print p.foo
    p.reset()
    print p.foo

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