How to Subtract Two Lists in Python

Lists are the most versatile and dynamic datatypes in Python. We can store different types of data inside a list.

It doesn’t matter if they are numbers, characters, or strings. To initialize a list, we must put all the values inside a square bracket and differentiate each value using a comma.

Elements of a list are known as items. Please note that lists are mutable. We can add, remove, and modify the items anytime in a Python program. Here is an example of a Python list:

demo_list1 = ['Mark', 'Alex', 1987, 2020]

demo_list2 = [5, 4, 3, 2, 1 ]

demo_list3 = ["x", "y", "z"]

To print a list in Python, we need to make use of the print() function in Python. Like this:

print(demo_list1)

Now, let’s talk about the main topic of today: How to subtract two lists in Python. We can determine the difference between two lists in Python mainly in two different ways. Let’s get started.

Using set()

Set is a collection-type object which can store elements of different data types. A set() doesn’t index the values in a particular order. This method converts the lists into the python sets explicitly and then finds the difference between them. Here is a sample program is given for your better understanding.

def list_diff(my_list1, my_list2):

    return (list(set(my_list1) - set(my_list2)))

my_list1 = [10, 16, 21, 26, 31, 36, 41]

my_list2 = [10, 26, 41, 36]
print(list_diff(my_list1, my_list2))

Output: [16, 21, 31]

The set() function accepted the defined two lists in the above program and turned them into sets. Inside the print() function, it just calculated the difference.

Using a nested for-loop

To calculate the subtract value between two different lists, we can simply use a nested for-loop.

In this method, we’ll compare all the second list items with the first one sequentially, and while traversing, we’ll be appending every non-matching item to a new empty list.

At the end of the program, we’ll simply print the list. Here you go:

def list_diff(my_list1, my_list2):

    out = []

    for ele in my_list1:

    	if not ele in my_list2:

        	out.append(ele)

    return out

my_list1 = [10, 16, 21, 26, 31, 36, 41]

my_list2 = [10, 26, 41, 36]

print(list_diff(my_list1, my_list2))

Output: [16, 21, 31]

Using the list comprehension method

List comprehension is the same method as the nested for-loop. Here, we will replace the for-loop with the list comprehension syntax. For instance,

def list_diff(my_list1, my_list2):

    out = [item for item in my_list1 if not item in my_list2]

    return out

my_list1 = [10, 16, 21, 26, 31, 36, 41]

my_list2 = [10, 26, 41, 36]

print(list_diff(my_list1, my_list2))

Output: [16, 21, 31]

I hope this tutorial helped you to understand how to subtract two lists in Python! 

Happy coding!

Marcel Iseli

Hey guys! It’s me, Marcel, aka Maschi. On MaschiTuts, it’s all about tutorials! No matter the topic of the article, the goal always remains the same: Providing you guys with the most in-depth and helpful tutorials!

maschituts.com/about-me