Effortlessly Combine Two Overlapping DataFrames Vertically in Python with Pandas

Learn how to combine two overlapping Pandas DataFrames vertically, updating existing rows while adding new rows effectively.
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Effortlessly Combine Two Overlapping DataFrames Vertically in Python with Pandas

Combining two DataFrames in Python can often be a challenge, especially when they overlap. Many developers face the problem of how to merge two overlapping DataFrames vertically—this means they want to add rows from one DataFrame to another, while also ensuring that existing rows in the first DataFrame are updated if the same index exists in the second DataFrame.

In this guide, we will walk you through this process using the popular pandas library, showcasing a simple yet effective solution that addresses common pitfalls. Let’s dive right in!

The Problem: Merging Two Overlapping DataFrames

Let’s say you have the following two DataFrames:

[[See Video to Reveal this Text or Code Snippet]]

Current State of DataFrames

df1 looks like this:

[[See Video to Reveal this Text or Code Snippet]]

df2 looks like this:

[[See Video to Reveal this Text or Code Snippet]]

Desired Outcome

Your goal is to create a new DataFrame that contains:

All rows from df1 and df2.

Updates df1's rows if any intersecting rows with the same index are present in df2.

The expected outcome should look like this:

[[See Video to Reveal this Text or Code Snippet]]

Attempted Solutions

You may have tried a few methods, such as:

The Solution: Merging with Care

Now, let’s focus on how to accurately combine these DataFrames so that we achieve our desired output. We’ll make use of append combined with the duplicated method to retain the last occurrence of an index when conflicts arise.

Implementation Steps

Follow these simple steps to achieve your desired output:

Append the DataFrames: Use the append() method to stack them vertically.

Remove Duplicated Indices: Utilize duplicated() to ensure that if any index appears more than once, we keep only the last occurrence.

Here’s the Complete Code:

[[See Video to Reveal this Text or Code Snippet]]

What Happens Under the Hood?

The append() method stacks the two DataFrames vertically.

Final Thoughts

By following the above method, you can efficiently combine two overlapping DataFrames in Python using Pandas. The approach not only consolidates data but also retains critical updates from your second DataFrame. Whether you are working with large datasets or just small DataFrames, this method will ensure your data remains accurate and well-organized.

Happy coding! If you have any questions or further issues, feel free to reach out in the comments below!