# Python Program to Find the Sum of Natural Numbers – 2023 Hey guys, in this blog we will see a Python Program to Find the Sum of Natural Numbers.

## Example 1: Using While Loop

```# Python Program to Find the Sum of Natural Numbers

num = int(input("Enter a positive number -> "))

if num < 0:
print("Enter a positive number")
else:
sum = 0
# use while loop to iterate until zero
while(num > 0):
sum += num
num -= 1
print("The sum is ->", sum)
```

Output

```Enter a positive number -> 4
The sum is -> 10```
```Enter a positive number -> 5
The sum is -> 15```
```Enter a positive number -> 6
The sum is -> 21```
• In this way, we have simply declared a sum variable and we keep on adding the number to this variable.
• Also simultaneously we are reducing our original number in every iteration.
• Suppose the user inputs 4, our program will add 4 to sum which is currently 0, and reduce our org number 4 to 3, now in the next iteration our program will add 3 to sum, now sum becomes 7 and num becomes 2 and in this way when num becomes 0, our loop will break.

## Example 2: Using the formula

sum = n*(n+1)/2

```# Sum of natural numbers up to num

num = int(input("Enter a positive number -> "))

if num < 0:
print("Enter a positive number")
else:
sum = (num*(num+1))//2
print("The sum is ->", sum)
```

Output

```Enter a positive number -> 8
The sum is -> 36```
```Enter a positive number -> 9
The sum is -> 45```
```Enter a positive number -> 10
The sum is -> 55```
• This is the easiest way of calculating the sum of all natural numbers till a positive number.
• Suppose n=8, so the sum of all natural numbers till 8 will be (8*9)/2 which equals 36.

Check out our other python programming examples

Scroll to Top