Python Program to Print Series 1 + 2 + ... + n

When it is required to display the sum all the natural numbers within a given range, a method can be defined that uses a loop to iterate over the elements, and returns the sum of these numbers as output.

Below is a demonstration of the same −

Example

 Live Demo

def sum_natural_nums(val):
   my_sum = 0
   for i in range(1, val + 1):
      my_sum += i * (i + 1) / 2
   return my_sum

val = 9
print("The value is ")
print(val)
print("The sum of natural numbers upto 9 is : ")
print(sum_natural_nums(val))

Output

The value is
9
The sum of natural numbers upto 9 is :
165.0

Explanation

• A method named ‘sum_natural_nums’ is defined that takes a number as parameter.

• A sum value is defined as 0.

• A loop is iterated over the number passed as a parameter.

• The sum is incremented every time a number is encountered.

• This is returned as output.

• The value for number of natural numbers whose sum needs to be found is defined.

• The method is called by passing this number as a parameter.

• The relevant output is displayed on the console.