From: "Talin" <[EMAIL PROTECTED]>
There's been a lot of controversy/confusion about ordered dicts.
I think that is why all earlier proposals all died.
One of
the sources of confusion is that people mean different things when they
use the term "ordered dict": In some cases, the term is used to mean a
dictionary that remembers the order of insertions, and in other cases it
is used to mean a sorted dict, i.e. an associative data structure in
which the entries are kept sorted. (And I'm not sure that those are the
only two possibilities.)
For an insertion order dictionary, there was also a question about
how to handle duplicate keys.
Given odict([(k1,v1), (k2,v2), (k1,v3)]), what should the odict.items() return?
[(k1,v3), (k2,v2)]
[(k2,v2), (k1,v3)]
The first maintains the original sort order and is consistent with the usual
idea that d[k]=v simply replaces the value but does not alter the hash table.
It is a bit weird though because v3 appears earlier than v2 which was
inserted earlier. It's especially weird for keys that are equal but not
identical: d[0]=v1 d[0.0]=v3. Do you want 0.0 to remain associated
with v3 or should the items list contain a pair that was not in the original
insertion list, (0, v3)?
The second one is a bit weird because a key "loses its place" whenever
the value is updated.
IIRC, previous discussions showed an interest in odicts but that
there were a lot of questions of the specific semantics of the API.
This would no doubt be compounded by attempts to emulate
dict views. Regardless, there should probably be a PEP and
alternate pure python versions should be posted on ASPN so people
can try them out.
post
Raymond
_______________________________________________
Python-Dev mailing list
Python-Dev@python.org
http://mail.python.org/mailman/listinfo/python-dev
Unsubscribe:
http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
