But hashes of items are not known. Hashes of keys are known, hashes of values and items are not. We can add a special case for dict views in the set constructor and inline the hashing code for tuples, but it will be a lot of code for pretty rare case. And since hashes of values should be calculated in any case, and the significant time will be spent on allocating 2-tuples, the benefit of such optimization will be minor.