Raymond Hettinger added the comment:

Thank you for the link, it was nice to see Guido's reasons for giving a -0 on 
the proposal.  I would add that I haven't see any code in the wild that would 
benefit from testing isinstance(m, OrderedMapping) and taking some different 
action depending on the result.

Grant's sortedcollection is more sequence-like than mapping-like and the bidict 
has its own interesting properties and neither are substitutable for an 
OrderedDict.  In other words, the only properties these cluster on is the 
ordered equality feature.  IMO, that particular feature hasn't established 
itself as being valuable (we don't see much use of it with the existing ordered 
dicts, and likewise in the database world, table equivalence based on exact 
order rather than content equivalence is uncommon).

Given the limited utility, I am going to decline the proposal.  It is an 
interesting idea but I believe it that it would clutter the module, slightly 
drowning-out the ABCs that have more broad and established utility.

One other thought is that the proposed OrderedMapping ABC might not fit well in 
a possible future Python where the behavior Python 3.6 ordered-and-compact 
dicts becomes guaranteed but where we retain the traditional unordered equality 
comparison.

----------
resolution:  -> rejected
status: open -> closed

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Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue28912>
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