Calculate sum in python

Python program to calculate sum and average of first n natural numbers

In this lesson, you will learn how to calculate the sum and average of the first n natural numbers in Python.

Also, you will get to know how to calculate the addition and average of user-entered numbers, list of numbers. And the use of built-in function sum() .

This tutorials is part of Python Basics.

Table of contents

Sum and average of first n natural numbers

Sum and average of n numbers in Python

1. Accept the number n from a user Use input() function to accept integer number from a user.
2. Run a loop till the entered number Next, run a for loop till the entered number using the range() function. In each iteration, we will get the next number till the loop reaches the last number, i.e., n .
3. Calculate the sum In each iteration, keep adding the current number into the sum variable to calculate the addition. Use a formula sum = sum + current number .
4. Calculate the average At last, after the loop ends, calculate the average using a formula average = sum / n . Here, The n is a number entered by the user.

n = int(input("Enter number")) sum = 0 # loop from 1 to n for num in range(1, n + 1, 1): sum = sum + num print("Sum of first ", n, "numbers is: ", sum) average = sum / n print("Average of ", n, "numbers is: ", average)

Output Enter number 10 Sum of first 10 numbers is: 55 Average of 10 numbers is: 5.5

Use built-in function sum()

You can also take the advantage of built-in function sum() to calculate the sum of an iterable like range and list.

n = 10 res = sum(range(1, n + 1)) print("Sum of first ", n, "numbers is: ", res) # Output Sum of first 10 numbers is: 55

Sum and average of a list

Use the below steps to calculate the sum and average of numbers present in the given list.

• Iterate a Python list using a for loop and add each number to a sum variable.
• To calculate the average, divide the sum by the length of a given list (total numbers in a list)

# list with int and floats num_list = [10, 20.5, 30, 45.5, 50] # Approach 1 using built-in function sum res = sum(num_list) avg = res / len(num_list) print("sum is: ", res, "Average is: ", avg) # Output sum is: 156.0 Average is: 31.2 # Approach 2 using a for loop res1 = 0 for num in num_list: res1 += num avg1 = res1 / len(num_list) print("sum is: ", res1, "Average is: ", avg1) # Output sum is: 156.0 Average is: 31.2

Sum and average using a mathematical formula

In the above programs, we calculated the sum and average using the looping technique. Now, let’s see how to calculate the sum and average directly using a mathematical formula.

• The sum of the first n natural number = n * (n+1) / 2
• the average of first n natural number = (n * (n+1) / 2) / n

n = 20 # formula to calculate sum res = n * (n + 1) / 2 print('sum of first', n, 'numbers is:', res) # Output sum of first 20 numbers is: 210.0 # formula to calculate average average = (n * (n + 1) / 2) / n print('Average of first', n, 'numbers is:', average) # Output Average of 20 numbers is: 10.5 

Sum and average of multiple user-entered numbers

If you want to calculate the sum and percentage of multiple user-entered numbers, please refer to the following program.

input_string = input('Enter numbers separated by space ') print("\n") # Take input numbers into list numbers = input_string.split() # convert each item to int type for i in range(len(numbers)): # convert each item to int type numbers[i] = int(numbers[i]) # Calculating the sum and average print("Sum = ", sum(numbers)) print("Average wp-block-preformatted">Enter numbers separated by space 10 20 30 40 50 Sum = 150 Average = 30.0

While loop to calculate sum and average

You can also use the Python while loop to calculate the sum and average of n numbers. Follow these steps:

• Decide the value of n .
• Run a while loop till n is greater than zero.
• In each iteration, add the current value of n to the sum variable and decrement n by 1.
• Calculates the average by dividing the sum by n (total numbers).

n = 20 total_numbers = n sum = 0 while n >= 0: sum += n n -= 1 print("sum =", sum) # Output sum = 210 average = sum / total_numbers print("Average wp-block-heading" >Practice Problem: Add two matrices in Python 
matrixOne = [[6,9,11], [2 ,3,8]] matrixTwo = [[15,18,11], [26,16,19]] # Result shoud be result = [[0,0,0], [0,0,0]]
 
Solution
 
matrixOne = [[6,9,11], [2 ,3,8]] matrixTwo = [[15,18,11], [26,16,19]] result = [[0,0,0], [0,0,0]] # First iterate rows for i in range(len(matrixOne)): # Second iterate columns for j in range(len(matrixOne[0])): result[i][j] = matrixOne[i][j] + matrixTwo[i][j] print("Addition of two Matrix In Python") for res in result: print(res)
 
Next steps
 
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About Vishal
 
I’m Vishal Hule, Founder of PYnative.com. I am a Python developer, and I love to write articles to help students, developers, and learners. Follow me on Twitter
 
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Python sum() Function
 
The sum() function returns a number, the sum of all items in an iterable.
 
Syntax
 
Parameter Values
 
 
 
 
Parameter
 
Description
 
 
 
iterable
 
Required. The sequence to sum
 
 
 
start
 
Optional. A value that is added to the return value
 
 
 
 
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Example
 
Start with the number 7, and add all the items in a tuple to this number:
 
 
 
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