A MutableSet that remembers its order, so that every entry has an index.
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:
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__