Python Program to Find Sum of Natural Numbers Using Recursive Function

def sum(n):
    if n <= 1:
        return n
    else:
        return n + sum(n-1)

num = int(input("Enter a number: "))
print("The sum is: ", sum(num))

The input() function takes input from the user and int() function converts its type to an integer as Python return string from input function. Here, we define a recursive function sum() that takes an argument which is an integer number. The base condition for recursion is defined and if the input number is less than or equals to 1, the number is returned, else we return the same function call with number decremented by 1. In this way, the recursive function works in Python that can calculate the sum of natural numbers.