What does the code 'vals[0],vals[1]=vals[1],vals[2]' accomplish?

The code snippet vals[0], vals[1] = vals[1], vals[2] is a Python tuple unpacking feature that allows multiple assignments to happen simultaneously. In this snippet, the values on the right side, vals[1] and vals[2], are evaluated first, and then simultaneously assigned to vals[0] and vals[1] respectively.

This means that:

• vals[0] takes the value of vals[1].

• vals[1] takes the value of vals[2].

As a result of this single line of code, the original value of vals[0] is effectively replaced by what used to be vals[1], and vals[1] is now set to what was originally vals[2]. Therefore, it does not simply swap vals[0] and vals[1], nor does it shift all values in the list or set vals[1] to vals[0]. It’s a direct assignment that modifies vals[0] and vals[1] based on two other elements in the list.