Python Sets Are OP!!

Learn How to Merge Two Lists, Remove Duplicates, and Sort the Resulting List in Python

In this tutorial, we’re going to walk through a simple and efficient way to merge two lists of integers, remove any duplicates, and sort the resulting list in ascending order. This is a common task in Python, and we’ll achieve it using just a few lines of code.

Step 1: Understanding the Problem

Let’s say we have two lists of integers, A and B. What we want to do is:

1. Combine these two lists into one.
2. Remove any duplicates from the combined list.
3. Sort the final list in ascending order.

We can accomplish this with a simple function in Python. Here’s how:

Step 2: Writing the merge_arrays Function

We’ll create a function called merge_arrays that takes two lists as input and returns the desired output. Here’s the code:

def merge_arrays(arrayA, arrayB):
    """Merges two arrays, removes duplicates, and sorts in ascending order."""
    return sorted(set(arrayA + arrayB))

Let’s break down what’s happening in this function.

Combining the Lists

First, we combine the two lists arrayA and arrayB using the + operator:

combined_list = arrayA + arrayB

The + operator simply concatenates the two lists. For example:

a = [1, 2, 3, 3, 4, 5, 6]
b = [4, 4, 5, 6, 7, 8, 9]
combined_list = a + b
print(combined_list)

This will output:

[1, 2, 3, 3, 4, 5, 6, 4, 4, 5, 6, 7, 8, 9]

As you can see, the lists are now combined, but there are duplicates.

Removing Duplicates with a Set

Next, we convert the combined list into a set:

unique_set = set(combined_list)

Sets in Python automatically remove any duplicates because sets are collections of unique elements. Continuing with the same example:

unique_set = set(combined_list)
print(unique_set)

This will output:

{1, 2, 3, 4, 5, 6, 7, 8, 9}

Notice that all the duplicates are gone!

Sorting the Final List

Finally, we use the sorted() function to convert the set back into a list and sort it:

sorted_list = sorted(unique_set)

The sorted() function returns a new list containing all elements from the input set in ascending order.

Step 3: Putting It All Together

Now, let’s combine everything into our merge_arrays function:

def merge_arrays(arrayA, arrayB):
    """Merges two arrays, removes duplicates, and sorts in ascending order."""
    return sorted(set(arrayA + arrayB))

When you call this function with two lists:

a = [1, 2, 3, 3, 4, 5, 6]
b = [4, 4, 5, 6, 7, 8, 9]
c = merge_arrays(a, b)
print(c)

Now our final code:

def merge_arrays(arrayA, arrayB):
    #1 Merges two arrays (arrayA and arrayB)
    #2 Removes duplicates
    #3 Sort in ascending order
    return sorted(set(arrayA + arrayB))

# Example usage
a = [1, 2, 3, 3, 4, 5, 6]
b = [4, 4, 5, 6, 7, 8, 9]
c = merge_arrays(a, b)
print(c)

The output will be:

[1, 2, 3, 4, 5, 6, 7, 8, 9]

Step 4: Explanation and Final Thoughts

This solution is both simple and efficient. The use of sets makes it easy to remove duplicates, and the sorted() function ensures the final list is in the correct order. Because sets are unordered collections of unique elements, they are ideal for tasks where duplicate removal is necessary.

With just one line of code inside our function, we’ve managed to combine two lists, eliminate duplicates, and sort the results. This approach is not only clean but also leverages Python’s built-in functions to keep the code concise and readable.

Conclusion

You now have a handy function merge_arrays that you can use anytime you need to merge two lists, remove duplicates, and sort the result. Understanding how to use sets and the sorted() function can be very useful in many Python programming tasks, so keep these tools in mind for the future.