Merging Two Lists in Python

Learn how to merge two lists in Python, including the different methods and techniques for combining lists, along with code examples and explanations. …

Updated May 18, 2023

Learn how to merge two lists in Python, including the different methods and techniques for combining lists, along with code examples and explanations.

As a beginner or experienced programmer, you may have encountered situations where you need to combine two or more lists together. In this article, we will explore the concept of merging lists in Python, including step-by-step explanations and code snippets.

Definition of Merging Lists

Merging lists refers to the process of combining two or more lists into a single list. This can be done using different methods, such as concatenating lists, adding elements one by one, or using advanced data structures like sets and dictionaries.

Step 1: Understanding Python Lists

Before diving into merging lists, it’s essential to understand what Python lists are and how they work. A list in Python is a collection of items that can be of any data type, including strings, integers, floats, and other lists. You can access elements in a list using their index (position) within the list.

Step 2: Concatenating Lists

One of the simplest methods to merge two lists is by concatenating them using the + operator or the extend() method.

Example Code Snippet 1: Concatenating Two Lists

list1 = [1, 2, 3]
list2 = ['a', 'b', 'c']

merged_list = list1 + list2

print(merged_list)  # Output: [1, 2, 3, 'a', 'b', 'c']

Example Code Snippet 2: Using the extend() Method

list1 = [1, 2, 3]
list2 = ['a', 'b', 'c']

merged_list = list1
merged_list.extend(list2)

print(merged_list)  # Output: [1, 2, 3, 'a', 'b', 'c']

Step 3: Adding Elements One by One

Another method to merge two lists is by adding elements from one list to another using a loop or the append() method.

Example Code Snippet 3: Adding Elements Using a Loop

list1 = [1, 2, 3]
list2 = ['a', 'b', 'c']

merged_list = []
for element in list1:
    merged_list.append(element)
for element in list2:
    merged_list.append(element)

print(merged_list)  # Output: [1, 2, 3, 'a', 'b', 'c']

Example Code Snippet 4: Using the append() Method

list1 = [1, 2, 3]
list2 = ['a', 'b', 'c']

merged_list = list1
for element in list2:
    merged_list.append(element)

print(merged_list)  # Output: [1, 2, 3, 'a', 'b', 'c']

Step 4: Using Sets and Dictionaries

If you need to remove duplicates from the merged list, you can use sets or dictionaries.

Example Code Snippet 5: Using a Set

list1 = [1, 2, 3]
list2 = ['a', 'b', 'c']

merged_set = set(list1 + list2)
print(merged_set)  # Output: {1, 2, 3, 'a', 'b', 'c'}

Example Code Snippet 6: Using a Dictionary

list1 = [1, 2, 3]
list2 = ['a', 'b', 'c']

merged_dict = dict(zip(list1 + list2, range(len(list1 + list2))))
print(merged_dict)  # Output: {1: 0, 2: 1, 3: 2, 'a': 3, 'b': 4, 'c': 5}