About the Authors

Jeroen Janssens

Jeroen is a senior developer relations engineer at Posit, PBC. His expertise lies in visualizing data, implementing machine learning models, and building solutions using Python, R, JavaScript, and Bash. He’s passionate about open source and sharing knowledge. Previously, Jeroen was at Xomnia, where he first learned about Polars. He is a co-author of Python Polars: The Definitive Guide (O’Reilly, 2025) and the author of Data Science at the Command Line (O’Reilly, 2021). Jeroen holds a PhD in machine learning from Tilburg University and an MSc in artificial intelligence from Maastricht University. He lives with his wife and two kids in Rotterdam, the Netherlands. Learn more on his website.

Thijs Nieuwdorp

Thijs is a Developer Relations Engineer at Polars, where he creates educational content, training materials, and showcase use cases that help developers unlock the full potential of the library. His interest in the interaction between human and computer led him to an education in artificial intelligence at the Radboud University. He is a co-author of Python Polars: The Definitive Guide (O’Reilly, 2025). During his time as lead data scientist at Xomnia in Amsterdam, he witnessed the birth of Polars as Ritchie Vink started working on it and has been using it in his projects ever since. Now at Polars, he combines his experience solving complex data problems and optimizing solutions with his passion for teaching developers how to leverage Polars effectively in their own work. Outside work, Thijs enjoys exploring our world through hiking and traveling and exploring other worlds through books, games, and movies. He lives in Amsterdam with his partner, Paula. Learn more on his website.