Python program to print sum of N natural numbers

Find the Sum of N Natural Numbers in Python

Find the Sum of N Natural Numbers in Python

Given an integer input number, the objective is to sum all the numbers that lay from 1 to the integer input number and print the sum. In order to do so we usually use iteration to sum all the numbers until the input variable number.

Example
Input : number = 5
Output : 15
Explanation : 1 + 2 + 3 + 4 + 5 = 15

Find the Sum of N Natural Numbers

Given an integer value the objective of the code is to sum up all the numbers until the input integer number. To do so we usually use iteration, we iterate through the numbers until the input number is reached while appending the number to the sum variable. Here are some methods to solve the above mentioned problem

  • Method 1: Using for Loop
  • Method 2: Using Formula
  • Method 3: Using Recursion

We’ll discuss the above methods in detail in the sections below.

Method 1: Using for Loop

In this method we’ll use for loops to iterate through all the numbers until the integer input “number” is reached.

Working

For an integer input “number” we do the following

  • Initialize the required variables.
  • Using for loop iterate from 0 to number+1.
  • Meanwhile append the number to sum variable.
  • Print the sum variable.

Let’s implement the above logic in Python code.

Python Code

number,sum = 6,0
for i in range(number+1):
  sum+=i
print(sum)

Output

21

Method 2: Using the Formula

In this method we’ll use the formula for finding the sum of N integers in a series from series and sequences i.e sum = number * ( number + 1 ) / 2 to calculate the sum until the given integer input.

Working

For an integer input “number”  we perform the following steps

  • Initialize sum variable as sum = (number * ( number + 1 ) /2 ).
  • Print the sum variable.

Let’s implement the above logic in Python Language.

Python Code

number = 6
sum = int((number * (number + 1))/2)
print(sum)

Output

21

Method 3: Using Recursion

In this method we’ll use recursion to recursively iterate through the number while appending them to the sum variable until the number is reach which here act as the base case. To learn more about recursion, check out Recursion in Python.

Working

For an integer input “number” we do

  • Initialize the required variables.
  • Define a recursive function with base case as number ==0.
  • Set the step recursive call as number + recursum( number – 1 ).
  • Call the recursive function recursum() and print the returned value.

Let’s implement the above logic using Python Language.

Python Code

def recursum(number):
  if number == 0:
    return number
  return number + recursum(number-1)
number, sum = 6,0
print(recursum(number))

Output

21

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