Calculating Sum of Squares in Python

To find the sum of the squares of a list of numbers in Python, the easiest way is with a for loop.

def sum_of_squares(lst):
    sum = 0
    for x in lst:
        sum = sum + x ** 2
    return sum

print(sum_of_squares(range(10))) # range(0,1,2,3,4,5,6,7,8,9)
print(sum_of_squares([4,6,2,9,10]))

#Output:
285
237

You can also use sum() and list comprehension to find the sum of squares of a list of numbers in Python.

def sum_of_squares(lst):
    return sum([x ** 2 for x in lst])

print(sum_of_squares(range(10))) # range(0,1,2,3,4,5,6,7,8,9)
print(sum_of_squares([4,6,2,9,10]))

#Output:
285
237

If you want to calculate the sum of squares for the first N numbers, you can use the following formula.

def sum_of_squares_first_n(n):
    return (n * (n + 1) * (2 * n + 1)) // 6

print(sum_of_squares_first_n(5))

#Output:
55

When working with collections of numbers, the ability to easily summarize these collections can be useful.

One such calculation which is necessary sometimes is the sum of squares of a list of numbers.

The easiest way to get the sum of squares of a list of numbers in Python is with a for loop.

You can get the sum of squares of a list of numbers with a for loop by simply adding up the square of each number in a given list or range.

Below is an example which shows you how to use a for loop to get the sum of squares of a list in Python.

def sum_of_squares(lst):
    sum = 0
    for x in lst:
        sum = sum + x ** 2
    return sum

print(sum_of_squares(range(10))) # range(0,1,2,3,4,5,6,7,8,9)
print(sum_of_squares([4,6,2,9,10]))

#Output:
285
237

Using List Comprehension to Find Sum of Squares in Python

You can also use the sum() function and list comprehension to find the sum of squares of a list of numbers using Python.

For basic operations, wherever you use a for loop, it’s probable you can use list comprehension.

Below shows you how you can use list comprehension to get the sum of squares of a list in Python.

def sum_of_squares(lst):
    return sum([x ** 2 for x in lst])

print(sum_of_squares(range(10))) # range(0,1,2,3,4,5,6,7,8,9)
print(sum_of_squares([4,6,2,9,10]))

#Output:
285
237

Find Sum of Squares of First N Numbers with Formula in Python

For the first n numbers, there exists a formula which you can use which will give you the sum of the squares.

The sum of squares for the first n numbers is:

(n * (n + 1) * (2 * n + 1)) / 6

Below is a simple function which will get the sum of the squares of the first n numbers using Python. Note the use of integer division to return an integer value.

def sum_of_squares_first_n(n):
    return (n * (n + 1) * (2 * n + 1)) // 6

print(sum_of_squares_first_n(5))

#Output:
55

Hopefully this article has been useful for you to learn how to find the sum of squares in a list of numbers using Python.