How to add two lists in Python

In this topic, we will learn how we can add two lists in Python. But before going through the topic, we need to understand the term List in Python. Python list is used to store multiple items in a variable. Items in the list can be any ordered, changeable, and allow to store duplicate values. Each item of the list has an appropriate indexed value where the first index of the list starts with {0}, and the length index of the list must be n-1. Each item of the list is separated by a comma (,) symbol and enclosed within square brackets [].

Syntax

Here L1 and L2 are the two lists containing the same or different data type elements in a list. The List L1 contains the int and string data type elements, whereas the List L2 contains only int data type elements.

Let’s consider a program to print the list in Python.

programList.py

Output:

Display the List1 ['Rose', 'Lotus', 24, 'Gold', 'USA']
Display the List2 [1, 2, 4, 5, 6]
Display the Department List ['Web Designing', 40, 20]
Display the CS Department [58, 'Ms Wiley']

Let’s discuss the various method to add two lists in Python Program.

Method 1: Add two lists using the Naive Method:

It is a simple method that adds the two lists in Python using the loop and appends method to add the sum of lists into the third list. A for loop performs the addition of both lists with the same index number and continuously iterates the elements until the end of the list. After that append method, insert the added elements to the third list.

Let’s consider a program to add the two list in Python using the Naïve Method.

naivePro.py

Output:

Python Original list 1: [5, 10, 15, 20, 25, 30]
Python Original list 2: [2, 4, 6, 8, 10, 12]
 Addition of the list lt1 and lt2 is: [7, 14, 21, 28, 35, 42]

Method 2: Add two list using the Comprehension List

It is a shorthand technique of the Naive method in Python. The comprehension technique is much faster to type and retrieve the addition of the two lists. Therefore, it is used in Python programming to perform these types of tasks.

Let’s consider a program to add the two list in Python using the Naïve Method.

comprehension.py

Output:

Python list 1 : [2, 4, 6, 8, 10, 30]
Python list 2 : [2, 4, 6, 8, 10, 12]
 Addition of the list lt1 and lt2 is: [4, 8, 12, 16, 20, 42]

Method 3: Add two list in Python using the map() function with add operator:

In Python, a map() function is used to add two lists bypassing the list variables (lt1, lt2) and add as parameters. Inside the map() function, an added parameter acts like an additional operator to add lists and returns the sum.

Consider a program to add two lists in Python using the map() function with the add operator.

AddMap.py

Output:

Display the elements of List 1 [4, 8, 12, 16, 20, 24]
Display the elements of List 2 [2, 4, 6, 8, 10, 12]
 Sum of the list 1 and list 2 is: [6, 12, 18, 24, 30, 36]

Method 4: Accepts the list element from the user and joins the two lists.

In this program, we input the user’s list elements and insert them into the list using For loop. After that, perform the addition of the two lists in the Python program.

Let’s consider a program to take the input list element from the user and add them.

Accept.py

Output:

Enter the total number of the list elements: 5
 Enter the items into the List 1:
 Enter the value of 1 index is: 3
 Enter the value of 2 index is: 6
 Enter the value of 3 index is: 9
 Enter the value of 4 index is: 12
 Enter the value of 5 index is: 15
 Enter the items into the List 2:
 Enter the value of 1 index is: 2
 Enter the value of 2 index is: 4
 Enter the value of 3 index is: 6
 Enter the value of 4 index is: 8
 Enter the value of 5 index is: 10

 The addition of the two list is [5, 10, 15, 20, 25]

Method 5: Add two list using the zip() function with sum() function:

The sum() function is used to add two lists using the index number of the list elements grouped by the zip() function. A zip() function is used in the sum() function to group list elements using index-wise lists.

Let’s consider a program to add the list elements using the zip function and sum function in Python.

zipSum.py

Output:

Display the elements of List 1 [6, 12, 18, 3, 6, 9]
Display the elements of List 2 [4, 8, 12, 2, 4, 6]
 Sum of the list 1 and list 2 is : [10, 20, 30, 5, 10, 15]