An OrderedSet is a custom MutableSet that remembers its order, so that every entry has an index that can be looked up.
Based on a recipe originally posted to ActiveState Recipes by Raymond Hettiger, and released under the MIT license:
http://code.activestate.com/recipes/576694-orderedset/
Rob Speer's changes are as follows:
- changed the content from a doubly-linked list to a regular Python list. Seriously, who wants O(1) deletes but O(N) lookups by index?
- add() returns the index of the added item
- index() just returns the index of an item
- added a __getstate__ and __setstate__ so it can be pickled
- added __getitem__
- __getitem__ and index() can be passed lists or arrays, looking up all the elements in them to perform NumPy-like "fancy indexing"
minghu6's changes are as follow:
- restrict the OrderedSet operation object: only themselves. Because OrderededSet's element consists of its index and value, Python set's element only consists of its value, however. I have written a new class OrderedSetAdapter to adapt Python set.
- writtern a new class OrderedSetAdapter
- rewrittern some contradictory method from collections.MutableSet
Tested on Python 2.7, 3.3, 3.4, 3.5, 3.6, PyPy, and PyPy3.