How does Python's comma operator works during assignment?

Question

I was reading the assignment statements in the Python docs ( http://docs.python.org/reference/simple_stmts.html#assignment-statements ).

In that it is quoted that:

Answer 1

You can think of the assignments happening in parallel on copies rather than sequentially and in-place.

This is why in python you dont need a swap function:

a, b = b, a

works sufficiently without requiring a temp variable, c.