# Python Program to Find the Sum of Natural Numbers

Natural Number:

A natural number, as the name implies, is a number that occurs often and clearly in nature. It is a whole number with no negative digits.

Some mathematicians agree that a natural number must contain 0 while others do not. As a result, a list of natural numbers can be described as follows

N= 1 , 2 , 3 , 4 , 5 etc.

Prerequisite:

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### Examples:

Example 1:

Input :

number = 5

Output:

Sum of natural numbers till 5 = 15

Example 2:

Input :

number = 43

Output:

Sum of natural numbers till 43 = 946

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

Below are the ways to print the sum of natural numbers in python:

### Method #1:Using for loop

• Take a variable say sum and initialize to 0
• Iterate from 1 to N using for loop and range() function.
• For each iteration add the iterater value to sum.
• Print the sum.

Below is the implementation:

# given number
number = 5
# Take a variable say sum and initialize to 0.
sum = 0
# Iterate from 1 to number using for loop and range function
for i in range(1, number+1):
# add the iterater value to sum.
sum = sum + i
# print the sum
print("Sum of natural numbers till", number, "=", sum)


Output:

Sum of natural numbers till 5 = 15

### Method #2:Using while loop

• Take a variable say sum and initialize to 0
• The while loop was used to iterate until number became zero.
• In each loop iteration, we have added the number to sum and decreased the value of number by 1.
• Print the sum.

Below is the implementation:

# given number
number = 5
# Take a variable say sum and initialize to 0.
sum = 0
# iterate till the number becomes 0 using while loop
while(number != 0):
# add the number value to sum
sum = sum+number
# decrement the number
number = number-1
# print the sum
print("Sum of natural numbers", "=", sum)


Output:

Sum of natural numbers = 15

### Method #3:Using mathematical formula

Instead of iterating till number the best and efficient solution is to use mathematical formula given below.

Formula:

sum = ( n * (n +1) ) / 2

Below is the implementation:

# given number
number = 5
# Using mathematical formula
sum = (number * (number+1))//2
# print the sum
print("Sum of natural numbers till", number, "=", sum)


Output:

Sum of natural numbers till 5 = 15

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