[Python-ideas] caching properties

[Jared Grubb]

On 30 Apr 2009, at 12:22, Scott David Daniels wrote:
>
> This is slightly better (name change as in Antoine Pitrou's comment):
>
>    class cached(object):
>
>        def __init__(self, function):
>            self._function = function
>            self._cache = {}
>
>        def __call__(self, *args):
>            try:
>                return self._cache[args]
>            except KeyError:
>                self._cache[args] = self._function(*args)
>                return self._cache[args]
>
>        def expire(self, *args):
>            del self._cache[args]
>

The only thing I dislike is how many dictionary lookups are required  
in order to return the value after it's been cached. I count 4 lookups  
(object.prop, prop.__call__, self._cache, and self._cache[args]).  
These add up, especially if object.prop could have returned the value  
immediately without having to go through so much indirection (but this  
is not currently possible)

Jared