[Python-Dev] LinkedHashSet/LinkedHashMap equivalents (original) (raw)

Michael Hudson mwh at python.net
Thu Mar 10 09:42:55 CET 2005

"Delaney, Timothy C (Timothy)" <tdelaney at avaya.com> writes:

Set: Items are iterated over in the order that they are added. Adding an item that compares equal to one that is already in the set does not replace the item already in the set, and does not change the iteration order. Removing an item, then re-adding it moves the item to the end of the iteration order.

Well, this could be satisfied by an append_new operation on lists, right (thinking of Common Lisps #'cl:pushnew)? Complexity not that great, of course, but I've written code like:

if a not in l: l.append(a)

and not suffered that badly for it before now...

Dict: Keys are iterated over in the order that they are added. Setting a value using a key that compares equal to one already in the dict replaces the value, but not the key, and does not change the iteration order. Removing a key (and value) then re-adding it moves the key to the end of the iteration order.

And these are what CL types call association lists, in effect.

Cheers, mwh

-- #ifndef P_tmpdir printf( "Go buy a better computer" ); exit( ETHESKYISFALLINGANDIWANTMYMAMA ); -- Dimitri Maziuk on writing secure code, asr

More information about the Python-Dev mailing list