I think that's right. On a side node, if I recall my old python knowledge right the <1 - baz> and <1 - None> cases are only possible because -- well for one it

I think that's right. On a side node, if I recall my old python knowledge right the <1 - baz> and <1 - None> cases are only possible because -- well for one it uses only one object, so the fast check "key is elem" is always true -- but also the object utilizes the default __eq__ function, which tests on object identity. And since the same instance of C is used for all object invocations, this is always true. The behavior would be different using: x = C() y = C() d[x] = 'foo' d[y] = 'bar' d[x] = 'bar' d[y] = 'qux' The hash might collide, but the equality will cause the open addressing to skip the element. I dislike recalling debugging a hash function that wasn't entirely deterministic in some edge cases.