Perform List Subtraction in Python

In this article, we will learn to perform subtraction on a list in Python. We will use some built-in functions and some custom code as well. Let's first have a quick look over what is list and list subtraction in Python.

Python List

Python has a built-in data type called list. It is like a collection of arrays with different methodology. Data inside the list can be of any type say, integer, string or a float value, or even a list type. The list uses comma-separated values within square brackets to store data. Lists can be defined using any variable name and then assigning different values to the list in a square bracket. The list is ordered, changeable, and allows duplicate values.

list1 = ["Ram","Arun","Kiran"]
list2 = [16,78,32,67]
list3 = [‘apple’,’mango’,16,’cherry’,3.4]

List Subtraction

List subtraction uses two lists and returns a new list after subtraction. This is similar to performing a subtraction operation in mathematics. It finds the difference between each element at each index from the given two lists.

#input
list1 = [4,8,1,9,5]
list2 = [1,4,2,6,7]

#output
list3 = [3,4,-1,3,-2]

New List = Elements of List1 - Elements of List2

To perform list subtraction, the two input lists must be of the same length and it should contain elements of the same type i.e. both lists must contain only numerical values. The given example subtracts the elements at each index in one list from the other list.

Example: List Subtraction Using zip() and "-" operator

This method uses zip(iterator1, iterator2) with the list1 as iterator1 and list2 as iterator2 to return a zip object. It uses a for-loop to iterate over the zip object and subtract the lists' elements from each other and store the result in a new list.

#takes two input lists
list1 = [4, 8, 1, 9, 5]
list2 = [1, 4, 2, 6, 7]

#empty list
sub_list = []

#two lists are passed to zip 
zip_object = zip(list1, list2)

#loop to find diff of each element
for list1_i, list2_i in zip_object:
    sub_list.append(list1_i - list2_i)

print(sub_list)

[3, 4, -1, 3, -2]

Conclusion

In this article, we learned to find the difference between each element of two lists by traversing them using a zip object. We learned to perform list subtraction over each element.