How to Remove List From List in Python

1. Remove List B From List a Using the remove() Method in Python
2. Remove List B From List a Using the difference() Method in Python

The list in Python is a data structure that contains an order sequence of items. We can perform many operations on the list. Let’s say we want to remove a list B from list A. It simply means that we want to remove the items from list A that are also present in list B.

For Example we have a list A which contains items ["Blue", "Pink", "Purple", "Red"] and List B contains the items ["Silver", "Red", "Golden", "Pink"]. Now, if we remove list B from list A, in the output, we will get list A as ["Blue", "Purple"] because these items were also present in list B. We can do this task either by using the remove() function with a list or using the difference() function available with the set data structure.

Remove List B From List a Using the remove() Method in Python

In this example, we will use the remove() method on list A to remove the items that are similar in list A and list B. We use the remove() method with list A so that items will be removed from list A, but list B will be the same as before. In this code, we iterate over the items of list A and check if that item is also present in list B; the item will be removed from list A.

Example Code:

# Python 3.x
list_A = ["Blue", "Pink", "Purple", "Red"]
list_B = ["Silver", "Red", "Golden", "Pink"]
print("List A before:", list_A)
print("List B before:", list_B)
for item in list_A:
    if item in list_B:
        list_A.remove(item)
print("List A now:", list_A)
print("List B now:", list_B)

Output:

List A before: ['Blue', 'Pink', 'Purple', 'Red']
List B before: ['Silver', 'Red', 'Golden', 'Pink']
List A now: ['Blue', 'Purple']
List B now: ['Silver', 'Red', 'Golden', 'Pink']

Remove List B From List a Using the difference() Method in Python

Another way to remove similar items from list A is to subtract them from list B. With the set data structure, there is a method difference() that will return the items present in set A but not in set B. It returns only the different items of set A, which are unique between the two sets. But as this method is available with set.

So in our code, we will first cast both lists to set, then apply the set_A.difference(set_B) function, and we will store the result again in list_A by casting the result to list data type.

Example Code:

# Python 3.x
list_A = ["Blue", "Pink", "Purple", "Red"]
list_B = ["Silver", "Red", "Golden", "Pink"]
print("List A before:", list_A)
print("List B before:", list_B)
setA = set(list_A)
setB = set(list_B)
list_A = list(setA.difference(list_B))
print("List A now:", list_A)
print("List B now:", list_B)

Output:

List A before: ['Blue', 'Pink', 'Purple', 'Red']
List B before: ['Silver', 'Red', 'Golden', 'Pink']
List A now: ['Purple', 'Blue']
List B now: ['Silver', 'Red', 'Golden', 'Pink']