Steven D'Aprano and I have pushed a third draft of PEP 584: https://www.python.org/dev/peps/pep-0584/ The accompanying reference implementation is on GitHub: https://github.com/brandtbucher/cpython/tree/addiction For those who have been following the discussions over the past year on python-ideas, this new draft does not contain much additional content; the most notable difference is that the choice of operator has been changed from + to |. The rest of the revisions are mostly reformatting and reorganizing the information to bring the document in line with PEP standards. Please let us know what you think – we'd love to hear any *new* feedback that hasn't yet been addressed in the PEP or the related discussions it links to! Thanks! Brandt