This is a really handy thing to have around, in case you've got expensive computations that you want done more than once. I've written a clumsier version of this myself, once or twice -- but it makes sense to have in the standard library!
http://docs.python.org/py3k/library/functools.html#functools.lru_cache
There's some other neat stuff in the functools package too: currying and reducing. Pretty slick!
