Python program that checks if the input is a happy number or not. Also prints out the first 1,000 happy numbers. - depends on user input. Add comments

Happy number = A happy number is a number defined by the following process: Starting with any positive integer, replace the number by the sum of the squares of its digits, and repeat the process until the number equals 1 (where it will stay), or it loops endlessly in a cycle which does not include 1. Those numbers for which this process ends in 1 are happy numbers.