The Most Common Misconception About Inplace Operations in Pandas

Pandas users often modify a DataFrame inplace expecting better performance. Yet, it may not always be efficient. Here's why.

The image compares the run-time of inplace and non-in-place operations. In most cases, inplace operations are slow.

Why?

Contrary to common belief, most inplace operations DO NOT prevent the creation of a new copy. It is just that inplace assigns the copy back to the same address.

But during this assignment, Pandas performs some extra checks (SettingWithCopy) to ensure that the DataFrame is being modified correctly. This, at times, can be an expensive operation.

Yet, in general, there is no guarantee that an inplace operation is faster.

What’s more, inplace operations do not allow chaining multiple operations, such as this:

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I like to explore, experiment and write about data science concepts and tools. You can read my articles on Medium. Also, you can connect with me on LinkedIn and Twitter.