If Python had had built-in set notation from the start, {} might indeed have been a notation for an empty set instead of an empty dict. However, Python didn't

If Python had had built-in set notation from the start, {} might indeed have been a notation for an empty set instead of an empty dict. However, Python didn't even have sets at all until version 2.3, and they were in a stdlib module instead of being a built-in type until version 2.6. By that time dict notation was well entrenched.