Alex Martelli wrote: > Note the plural in 'insertion orderS': some people care about the FIRST > time a key was added to a dict, some about the LAST time it was added, > some about the latest time it was 'first inserted' (added and wasn't > already there) as long as it's never been deleted since that occasion -- > and these are just a few of the multifarious orders based on the time of > insertions and deletions of keys.
Ok, I start to understand that ambiguity emerges when you delete and insert items. I didn't think much about this problem because my use cases usually do not involve inserttion or deletion after the ordered dictionary has been created. But I think the following rule is "natural" enough to consider it as THE standard behavior of ordered dictionaries: "Insertion: If the key exists: Don't change the order. If it does not exist: Append it to the sequence of keys. Deletion: Remove from the sequence of keys." I think this is also the behavior of associative arrays in PHP or Perl and could be considered as the "ONE unambiguous definition". -- Christoph -- http://mail.python.org/mailman/listinfo/python-list
