Python Program to find Sum of N Natural Numbers

Write a Python Program to find the Sum of N Natural Numbers using While Loop, For Loop, Functions, and recursion with an example. To achieve the same, we need a loop to iterate the numbers from 1 to N and then the arithmetic operator + to add those items to the total.

Python Program to find Sum of N Natural Numbers using For Loop

This program allows users to enter any integer value. Next, it calculates the sum of natural numbers from 1 to a user-specified value using For Loop. If you want a more dynamic approach, allow the user to enter the starting value and replace 1 in the for loop with the user-entered start value.

The for loop iteration starts at one and traverses up to the user-given number. Within the loop, each value will be added to the total variable to find the sum of integers.

number = int(input("Please Enter any Number: "))
total = 0

for value in range(1, number + 1):
    total = total + value

print("The Sum from 1 to {0} =  {1}".format(number, total))

Please Enter any Number : 25
The Sum from 1 to 25 = 325

Python Program to find Sum of N Natural Numbers using While Loop

In this program, we just replaced the For Loop with the While Loop. Don’t forget to initialize the value to 1 and increment by one (value = value + 1).

num = int(input("Please Enter any Num: "))

total = 0
value = 1

while (value <= num):
    total = total + value
    value = value + 1

print("The Sum from 1 to {0} =  {1}".format(num, total))

Please Enter any Num: 12
The Sum from 1 to 12 = 78

Using Functions

In this program, we created a new function to find the sum of natural numbers. Inside this function, we used the If Else statement.

def sum_of_n_natural_numbers(num):
    if(num == 0):
        return num
    else:
        return (num * (num + 1) / 2)
    
number = int(input("Please Enter any Number: "))

total_value = sum_of_n_natural_numbers(number)

print("Sum from 1 to {0} =  {1}".format(number, total_value))

Please Enter any Number: 100
Sum from 1 to 100 =  5050.0

Using Recursion

This program is the same as the above example, but we are using Recursion now. The return (num + sum_of_n_natural_numbers(num – 1)) line calls the function recursively with the updated value.

def sum_of_n_natural_numbers(num):
    if(num == 0):
        return num
    else:
        return (num + sum_of_n_natural_numbers(num - 1))
    
number = int(input("Please Enter any Number: "))

total_value = sum_of_n_natural_numbers(number)

print("Sum of Natural Numbers from 1 to {0} =  {1}".format(number, total_value))