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

Last update on May 24 2025 10:47:01 (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:

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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Python Code Editor:

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