Python Program to Find the Sum of Natural Numbers

Introduction

The sum of natural numbers is a basic mathematical operation. Natural numbers are positive integers starting from 1. This tutorial will guide you through creating a Python program that calculates the sum of all natural numbers up to a specified number.

Problem Statement

Create a Python program that:

• Takes a positive integer as input.
• Calculates the sum of all natural numbers from 1 to the specified number.
• Displays the sum.

Example:

• Input: n = 10
• Output: The sum of natural numbers up to 10 is 55

Solution Steps

1. Take Input from the User: Use the input() function to get a positive integer from the user.
2. Convert Input to an Integer: Convert the input string to an integer using int().
3. Calculate the Sum: Use a loop or a formula to calculate the sum of natural numbers up to the specified number.
4. Display the Result: Use the print() function to display the sum.

Python Program

# Python Program to Find the Sum of Natural Numbers
# Author: https://www.rameshfadatare.com/

# Step 1: Take input from the user
n = int(input("Enter a positive integer: "))

# Step 2: Calculate the sum using the formula
# Sum of first n natural numbers = n * (n + 1) / 2
if n > 0:
    sum_natural = n * (n + 1) // 2  # Use // for integer division
    # Step 3: Display the result
    print(f"The sum of natural numbers up to {n} is {sum_natural}")
else:
    print("Please enter a positive integer.")

Explanation

Step 1: Take Input from the User

• The input() function prompts the user to enter a positive integer. The input is converted to an integer using int().

Step 2: Calculate the Sum

• The sum of the first n natural numbers can be calculated using the formula: This formula is efficient and avoids the need for a loop.

Step 3: Display the Result

• The print() function is used to display the sum of natural numbers up to n. If the user enters a non-positive integer, the program will prompt the user to enter a positive integer.

Output Example

Example:

Enter a positive integer: 10
The sum of natural numbers up to 10 is 55

Example:

Enter a positive integer: 5
The sum of natural numbers up to 5 is 15

Example (Invalid Input):

Enter a positive integer: -3
Please enter a positive integer.

Conclusion

This Python program demonstrates how to calculate the sum of natural numbers up to a specified number using a mathematical formula. It is a simple yet powerful example for beginners to understand basic arithmetic operations and user input handling in Python.