Ever tried passing a Polars Dataframe to a data science library and found that it...just works? No errors, no panics, no noticeable overhead, just...results? This is becoming increasingly common in 2025, yet only 2 years ago, it was mostly unheard of. So, what changed? A large part of the answer is: Narwhals.

Narwhals is a lightweight compatibility layer between dataframe libraries which lets your code work seamlessly across Polars, pandas, PySpark, DuckDB, and more! And it's not just a theoretical possibility: with ~30 million monthly downloads and set as a required dependency of Altair, Bokeh, Marimo, Plotly, Shiny, and more, it's clear that it's reshaping the data science landscape. By the end of the talk, you'll understand why writing generic dataframe code was such a headache (and why it isn't anymore), how Narwhals works and how its community operates, and how you can use it in your projects today. The talk will be technical yet accessible and light-hearted.

Narwhals is a lightweight compatibility layer between dataframe libraries which lets your code work seamlessly across Polars, Pandas, PySpark, DuckDB and more.

Suppose you want to write a data science tool to do feature engineering. Your experience may go like this: - Expectation: you can focus on state-of-the art techniques for feature engineering. - Reality: you keep having to make you codebase more complex because a new dataframe library has come out and users are demanding support for it.

Or rather, it might have gone like that in the pre-Narwhals era. Because now, you can focus on solving the problems which your tool set out to do, and let Narwhals handle the subtle differences between different kinds of dataframe inputs!

Polars is a dataframe library taking the world by storm. It is very runtime and memory efficient and comes with a clean and expressive API. Sometimes, however, the built-in API isn't enough. And that's where its killer feature comes in: plugins. You can extend Polars, and solve practically any problem.

No prior Rust experience required, intermediate Python and programming experience required. By the end of the talk, you will know how to write your own Polars Plugin! This talk is aimed at data practitioners.