Python Program to Merge Two Lists and Sort it

When it is required to merge two lists and sort them, Python provides several approaches. You can use list concatenation with the sort() method, or combine merging and sorting in one step using sorted().

Below is the demonstration of the same ?

Method 1: Using List Concatenation and sort()

Example

Define a function that merges two lists and sorts them in-place ?

def merge_list(list_1, list_2):
    merged_list = list_1 + list_2
    merged_list.sort()
    return merged_list

numbers_1 = [20, 18, 9, 51, 48, 31]
numbers_2 = [28, 33, 3, 22, 15, 20]
print("The first list is:")
print(numbers_1)
print("The second list is:")
print(numbers_2)
print("The merged and sorted list is:")
print(merge_list(numbers_1, numbers_2))

The first list is:
[20, 18, 9, 51, 48, 31]
The second list is:
[28, 33, 3, 22, 15, 20]
The merged and sorted list is:
[3, 9, 15, 18, 20, 20, 22, 28, 31, 33, 48, 51]

Method 2: Using sorted() Function

Example

Use the sorted() function to merge and sort in one step ?

def merge_and_sort(list_1, list_2):
    return sorted(list_1 + list_2)

numbers_1 = [20, 18, 9, 51, 48, 31]
numbers_2 = [28, 33, 3, 22, 15, 20]
result = merge_and_sort(numbers_1, numbers_2)
print("Merged and sorted list:", result)

Merged and sorted list: [3, 9, 15, 18, 20, 20, 22, 28, 31, 33, 48, 51]

Method 3: Using extend() Method

Example

Use extend() to add elements from the second list to the first ?

def merge_with_extend(list_1, list_2):
    merged_list = list_1.copy()  # Create a copy to avoid modifying original
    merged_list.extend(list_2)
    merged_list.sort()
    return merged_list

numbers_1 = [20, 18, 9, 51, 48, 31]
numbers_2 = [28, 33, 3, 22, 15, 20]
result = merge_with_extend(numbers_1, numbers_2)
print("Result using extend():", result)

Result using extend(): [3, 9, 15, 18, 20, 20, 22, 28, 31, 33, 48, 51]

Comparison

How It Works

• The + operator concatenates two lists by creating a new list containing all elements.

• The sort() method sorts the list in-place, modifying the original list.

• The sorted() function returns a new sorted list without modifying the original.

• The extend() method adds all elements from one list to another efficiently.

Conclusion

Use sorted(list1 + list2) for a clean one-liner approach. Use extend() with sort() for memory-efficient merging of large lists. All methods preserve the original lists unless you explicitly modify them.