Recursively add the digits of a Number and stop when it has become a single digit - Python

Given an Integer, add all the digits and check whether it has become a single digit or not. If it does, display the single digit you got or repeat adding digits until it becomes a single digit and display the single digit.


For Example:

If the Integer given is 167 = 1 + 6 + 7 = 14 = 1 + 4 = 5 ( it has became a single digit) . Hence, stop adding the digits and the output is "5"

Implementation: