## The **Objective of this post**: In this post, you will see various Python examples that cover the following:

**Calculate/Find**the sum of n natural numbers**using loop and range function**.- Find/Calculate Sum of n natural numbers in
**python using while loop** - Python program to
**find/calculate the sum of numbers**in a given list - The mathematical formula to
**find/calculate the sum of n numbers**with python program - Python Program to Find/Calculate sum of n odd natural numbers.
- Python Program to Find/Calculate sum of n even natural numbers.

Now let’s see each one by one:

### 1: **Find/**Calculate the sum of n natural numbers **using loop and range function**

- First of all, you can use a python input() function in your python program that takes a user to enter the number (n) to calculate the sum.
- Next, declare a variable that name sum, it will contain sum of n natural numbers sum.
- Next, run loop till the entered number using the for loop and range() function.
- Inside a loop, calculate the sum of n numbers using a
`sum = sum + current number`

formula. - After the loop ends, print the sum variable that contains
**the sum of n numbers**

#### Python program to find the sum of n numbers using for loop:

n = input("Enter Number to calculate sum") n = int (n) sum = 0 for num in range(0, n+1, 1): sum = sum+num print("SUM of first ", n, "numbers is: ", sum )

**Output**:

Enter Number to calculate sum 5 Sum of first 5 number is: 15

### 2: **Find/**Calculate Sum of n natural numbers in python using while loop

Also, use the while loop in python to calculate the sum of n numbers.

- First of all, you can use a python input() function in your python program that takes a user to enter the number (n) to calculate the sum.
- Next, declare a variable that name sum, it will contain the sum of n natural numbers sum.
- Run while loop until n is greater than zero
- Add the current value of n to sum variable. And, decrement n number by 1 in while loop body
- After the loop finishes, the print sum name variable.

#### Python program to find the sum of n numbers using While loop:

n = input("Enter Number to calculate sum") n = int (n) total_numbers = n sum=0 while (n >= 0): sum += n n-=1 print ("sum using while loop ", sum)

**Output**:

Enter Number to calculate sum 5 Sum using while loop 15

### 3: Python program to **Find/**Calculate the sum of numbers in a given list

- Declare a variable that name sum, it will contain the sum of n natural numbers sum.
- Next, define list and assign a value to a python list.
- Run for a loop and Add the current value of n to sum variable.
- After the loop finishes, the print sum name variable.

sum = 0 list = [11,4,5,7,99,10,12] for num in list: sum = sum +num print ("sum of list element is : ", sum)

**Output**:

sum of list element is : 148

### 4: The mathematical formula to **Find/**Calculate the sum of n numbers with python program

In the above programs, you have learned how to calculate the sum of n numbers using for loop, while loop and range function.

Now, you will learn how to calculate/find sum of n numbers in python without for loop, while loop in python. **Calculate the sum directly using a mathematical formula** in python program.

The sum of the n natural number mathematical formula is = ** n * (n+1) / 2**.

In the below python program, you will learn how to use this mathematical formula is = ** n * (n+1) / 2** to find/calculate sum of n numbers in python programs.

Follow the steps:

- Take a input from user in your python program using input() function.
- Convert a user inputted number to an integer using int() function.
- Calculates sum of number by using this formula
in your python program.`n * (n+1) / 2`

- After that, the print name sum variable.

n = input("Enter a number to calculate sum") n = int (n) sum = n * (n+1) / 2 print("Sum of fthe irst ", n, "natural numbers using formula is: ", sum )

**Output**:

Enter a number to calculate sum 5 Sum of fthe irst 5 natural numbers using formula is: 15.0

### 5: Python Program to Find/Calculate sum of n odd natural numbers

- Take input from user using python input() function in your python program.
- Next, declare a variable that name sum, it will contain the sum of n odd numbers.
- Next, run loop till the entered number using the for loop and range() function.
- Inside a loop, calculate the sum of n odd numbers using a
`sum = sum + current number`

formula with (not (num % 2) == 0). - After the loop ends, print the sum variable that contains
**the sum of n odd numbers**.

#### Python program to find sum of n odd numbers:

n = input("Enter Number to calculate sum") n = int (n) sum = 0 for num in range(0, n+1, 1): if(not (num % 2) == 0): sum += num; print("SUM of odd numbers is: ", sum )

**Output**:

Enter Number to calculate sum 5 SUM of odd numbers is: 9

### 6: Python Program to Find/Calculate sum of n even natural numbers

- Take input from the user using python input() function in your python program.
- Next, declare a variable that name sum, it will contain the sum of n even numbers.
- Next, run loop till the entered number using the for loop and range() function.
- Inside a loop, calculate the sum of n even numbers using a
`sum = sum + current number`

formula with if test condition ((num % 2) == 0). - After the loop ends, print the sum variable that contains
**the sum of n even numbers**.

#### Python program to find sum of n even numbers:

n = input("Enter Number to calculate sum") n = int (n) sum = 0 for num in range(0, n+1, 1): if((num % 2) == 0): sum += num; print("SUM of even numbers is: ", sum )

**Output**:

Enter Number to calculate sum 5 SUM of even numbers is: 9

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