$ python Python 3.10.0 (heads/3.10-dirty:f6e8b80d20, Nov 18 2021, 19:16:18) [GCC 10.1.1 20200718] on linux Type "help", "copyright", "credits" or "license" for more information. >>> a = {1:2} >>> c = {1:2, 3:4} >>> c.keys() - a.keys() {3} >>>
Why not frozenset({3})? -- https://mail.python.org/mailman/listinfo/python-list