@Serhiy

> It the pure Python implementation PyDict_GetItem also
> returns value, not node of linked list.

I missed pure Python implementation used two dicts.


@Eric

> Please don't miss the fact that the main reason for mirroring the dict table is to get O(1) node lookup (in the linked list). 

I don't miss it, of course.  I'm proposing make linked list node as Python Object, and store it directly into dict, like LRU implementation in _functools.

In this idea, if dict.__getitem__ is called directly, a node of linked list is returned instead of value in the node.
I must admit this idea is too aggressive.

If we can redesign OrderedDict from scratch, I propose OrderedDict uses dict, without inheriting it.  But it is too late.