Python supports 1-line A/B swap (A , B = B , A), and we would expect (B, A = A, B) would lead to the same result. However, I met a strange behavior when dealing with a list entry. I simplify my find...

I implemented a class that can be used to instantiate objects passed to a visitor function that detects duplicated keys in a JSON document. The problem I am trying to solve is detecting duplicate keys...