a = 3 and b = 8. Write code that swaps them, so that a is 8 and b is 3.

The problem. If we write a = b first, the old value of a is lost.

Method 1. A spare variable.

1. spare = a keeps 3 safe.
2. a = b makes a equal to 8.
3. b = spare makes b equal to 3.

Method 2. The Python way. a, b = b, a. Python works out the right side first, then stores both values.