Unlock the power of Polars, a Python package for transforming, analyzing, and visualizing data. In this hands-on guide, Jeroen Janssens and Thijs Nieuwdorp walk you through every feature of Polars, showing you how to use it for real-world tasks like data wrangling, exploratory data analysis, building pipelines, and more. Whether you're a seasoned data professional or new to data science, you'll quickly master Polars' expressive API and its underlying concepts. You don't need to have experience with pandas, but if you do, this book will help you make a seamless transition. The many practical examples and real-world datasets are available on GitHub, so you can easily follow along. Process data from CSV, Parquet, spreadsheets, databases, and the cloud - Get a solid understanding of Expressions, the building blocks of every query - Handle complex data types, including text, time, and nested structures - Use both eager and lazy APIs, and know when to use each - Visualize your data with Altair, hvPlot, plotnine, and Great Tables - Extend Polars with your own Python functions and Rust plugins - Leverage GPU acceleration to boost performance even further Polars has become a rising star in the Python data ecosystem, showing what's possible in a next-generation data frame library. Jeroen and Thijs have written a timely and essential resource to help you take advantage of everything Polars has to offer. — Wes McKinney, Creator of pandas, Principal Architect, Posit PBC Jeroen and Thijs have done an excellent job-not only teaching you the ins and outs of Polars but also helping you unlearn habits from other tools like pandas. They really bring out the power of expressions, which are key to using Polars effectively, guiding you toward a more declarative, functional approach to data processing. As you work through this book, I'm sure you'll gain a deep understanding of Polars and discover fresh ways to approach data processing. —Ritchie Vink, Creator of Polars (excerpt from the Foreword) Polars has brought a ton of much-needed innovation to the data frame world with its much more streamlined API and efficient implementation. As a result, the capabilities of data analysis in Python are pushed to new heights. We also greatly enjoy Ritchie and team as a part of the Amsterdam data ecosystem. I greatly respect Jeroen's commitment to teaching data science in an accessible way, whether it be on the command line or elsewhere. His and Thijs' book is a testament to this commitment and I recommend it to the data science community. — Hannes Mühleisen, Co-Creator of DuckDB Jeroen Janssens, PhD, 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. He's the author of Python Polars: The Definitive Guide (O'Reilly, 2025) and 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.