Swapping variables

Learn to swap values with a, b = b, a.

Exchanging the values of two variables is called a swap. In Python a swap is very easy:

a, b = b, a

The right side is evaluated first: a (b, a) tuple is built. Then the left side unpacks it. So no temporary variable is needed.

In other languages a temporary variable is usually needed. Python's multiple assignment does it in one line.

Swap with a temporary variable

In some languages a swap uses a temporary variable. It can be done in Python too, but it is not needed:

temp = a
a = b
b = temp

This method is longer and error-prone (it is easy to mix up the order). Python's a, b = b, a is both shorter and safe because it happens at once.

Assign a = 1 and b = 2. Then swap them with a, b = b, a. Finally print print(a, b).

Show example solution

a = 1
b = 2
a, b = b, a
print(a, b)