[Python-Dev] PEP 372 -- Adding an ordered directory to collections ready for pronouncement (original) (raw)

Forest list8a.forest at tibit.com
Tue Mar 3 20:47:42 CET 2009

On Tue, March 3, 2009 11:20 am, Forest wrote:

Okay, but I'd also like a convenient and fast way to find the oldest entry in an OrderedDict, which I think I'd need for an LRU cache. Skimming the current patch (od7.diff), I didn't notice one. Perhaps I simply missed something. Shouldn't popitem() allow the caller to choose which end from which to pop?

Thinking it through a bit more, and LRU cache would actually need to access the oldest item before knowing whether to remove it. Besides, popitem() should probably retain the signature of dict.popitem(). I therefore retract my suggestion about popitem().

Still, I think an LRU cache would be a very common use case for an ordered dict. The current implementation already uses a list to keep track of order, which makes accessing the oldest key a simple matter of exposing it. Perhaps a new method like getfirst() would be worth while here?

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