Python: Check whether a number is "happy" or not

Last update on April 17 2025 13:01:21 (UTC/GMT +8 hours)

Happy Number Checker

From Wikipedia, the free encyclopaedia:
A happy number is 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, while those that do not end in 1 are unhappy numbers.
Write a Python program to check whether a number is "happy" or not.

Sample Solution:

Python Code:

# Function to check if a number is a Happy Number
def is_Happy_num(n):
    past = set()  # Set to store previously encountered numbers during the process
    while n != 1:  # Continue the process until the number becomes 1 (a Happy Number) or a cycle is detected
        n = sum(int(i) ** 2 for i in str(n))  # Calculate the sum of squares of each digit in the number
        if n in past:  # If the current number has been encountered before, it forms a cycle
            return False  # The number is not a Happy Number
        past.add(n)  # Add the current number to the set of past numbers
    return True  # If the process reaches 1, the number is a Happy Number

# Test cases
print(is_Happy_num(7))
print(is_Happy_num(932))
print(is_Happy_num(6))

Sample Output:

True
True
False

Explanation:

Here is a breakdown of the above Python code:

Define a function named "is_Happy_num()" that takes a number 'n' as input.
Initialize a set called 'past' to keep track of previously encountered numbers during the process.
Use a while loop to continue the process until the number becomes 1 (a Happy Number) or a cycle is detected.
Inside the loop, calculate the sum of the squares of each digit in the current number.
Check if the current number has been encountered before. If yes, it forms a cycle, and the number is not a Happy Number.
Add the current number to the set of past numbers.
Return 'True' if the process reaches 1, indicating that the number is a Happy Number.
Test the function with different inputs to check its functionality.

Visual Presentation:

Python: Check whether a number is 'happy' or not

Flowchart:>

For more Practice: Solve these Related Problems:

Write a Python program to determine if a number is happy by iteratively summing the squares of its digits and detecting cycles.
Write a Python program to check if a given integer eventually reaches 1 through the sum-of-squares process.
Write a Python program to use a set to track previously seen sums and determine whether a number is happy.
Write a Python program to implement Floyd’s cycle-finding algorithm to efficiently check if a number is happy.

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Previous: Write a Python program to find the longest word in set of words which is a subsequence of a given string.
Next: Write a Python program to find and print the first 10 happy numbers.

Python Code Editor:

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