How To Merge Two Lists in Python

In Python, lists are a useful data type that allows you to store multiple items in a single variable. There are many operations that you can perform on lists, one of which is merging, or joining, two lists into one. This is especially useful when working with large amounts of data.

This tutorial will guide you through the steps to perform this operation.

Method 1: Using the “+” Operator

The most basic method is using the “+” operator to join two lists as follows:

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list1 = ["a", "b", "c"]
list2 = [1, 2, 3]
merged_list = list1 + list2

The above code will merge list1 and list2 to give merged_list as [‘a’, ‘b’, ‘c’, 1, 2, 3]. The Python “+” operator merges the lists by appending the second list at the end of the first list.

Method 2: Using the “extend()” Function

Another method to merge two lists is using the extend() function. This function adds the elements of the second list at the end of the first list.

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list1 = ["a", "b", "c"]
list2 = [1, 2, 3]
list1.extend(list2)

The above code will modify list1 to become [‘a’, ‘b’, ‘c’, 1, 2, 3]. Note that this method modifies the original list instead of creating a new one.

Method 3: Using a For Loop

The third method is using a for loop, which is especially useful if you want to add some conditions for the elements to be added to the new list.

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list1 = ["a", "b", "c"]
list2 = [1, 2, 3]
merged_list = [item for sublist in [list1, list2] for item in sublist]

This code will also yield the merged_list as [‘a’, ‘b’, ‘c’, 1, 2, 3]. It uses a concept of Python called list comprehension.

Full Code

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# Method 1
list1 = ["a", "b", "c"]
list2 = [1, 2, 3]
merged_list = list1 + list2
print(merged_list)
 
# Method 2
list1 = ["a", "b", "c"]
list2 = [1, 2, 3]
list1.extend(list2)
print(list1)
 
# Method 3
list1 = ["a", "b", "c"]
list2 = [1, 2, 3]
merged_list = [item for sublist in [list1, list2] for item in sublist]
print(merged_list)
 
['a', 'b', 'c', 1, 2, 3]
['a', 'b', 'c', 1, 2, 3]
['a', 'b', 'c', 1, 2, 3]

Conclusion

Python offers several methods for you to merge two lists, depending on your specific needs and conditions.

This tutorial covered three basic methods, but there are more methods and functions available in Python for list manipulation. You can learn more about lists in Python from the Python Documentation.