In this program, you'll learn to find the sum of n natural numbers using while loop and display it.

To understand this example, you should have the knowledge of following Python programming topics:

In the program below, we've used an if else statement in combination with a while loop to calculate the sum of natural numbers upto `num`.

# Python program to find the sum of natural numbers up to n where n is provided by user # change this value for a different result num = 16 # uncomment to take input from the user #num = int(input("Enter a number: ")) if num < 0: print("Enter a positive number") else: sum = 0 # use while loop to iterate un till zero while(num > 0): sum += num num -= 1 print("The sum is",sum)

**Output**

The sum is 136

**Note:** To test the program, change the value of `num`.

Here, we store the number in `num` and display the sum of natural numbers up to that number. We use `while`

loop to iterate until the number becomes zero.

We could have solved the above problem without using any loops using a formula directly.

**Your turn:** Modify the above program to find the sum of natural numbers using the formula below.

n*(n+1)/2

For example, if **n = 16**, the sum would be **(16*17)/2 = 136**.