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Jeroen Janssens

@jeroenjanssens.com
321 followers 56 following 23 posts

DevRel at Posit. Author of Python Polars: The Definitive Guide & Data Science at the Command Line

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Jeroen Janssens @jeroenjanssens.com · 18/08/2026
Python Polars: The Definitive Cheatsheet is out now, and it's free. Download it, print it, laminate it, put it on your desk. opensource.posit.co/resources/ch...
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Posit @posit.co · 19/05/2026
We’re excited to launch the Posit Open Source website! 🚀 We’ve unified 15+ years of tools, 900+ blogs, and 1,600+ videos in one place. Explore it here: opensource.posit.co Huge thanks to the team: @cwick.co.nz Greg Swinehart @hadley.nz @ivelasq3.bsky.social @jeroenjanssens.com
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Posit @posit.co · 26/05/2026
Are you on LinkedIn? If so, follow our new Posit Open Source LinkedIn Showcase Page! www.linkedin.com/showcase/117... We’ll be sharing updates, deep dives, and behind-the-scenes looks at everything we're developing for #RStats, #Python, and beyond. Tag us so we can see what you are building, too! 🤓
Posit Open Source LinkedIn Showcase page
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Oliver Theunissen @revulo.bsky.social · 20/02/2026
I'm currently reading "Python Polars: The Definitive Guide" by Jeroen Jannssens and Thijs Nieuwdorp, and I'm tempted to switch from pandas to polars, especially since @pola.rs is on Bluesky. 😀 #Python #Rust
O'REILLY

Python Polars The Definitive Guide

Transforming, Analyzing, and Visualizing Data with a Fast and Expressive DataFrame API

Jeroen Janssens & Thijs Nieuwdorp
Foreword by Ritchie Vink, Creator of Polars
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Julia Silge @juliasilge.com · 25/07/2025
I am starting to prep for my #positconf2025 talk this year, and I am excited but also a bit nervous 😅 because I am sharing how TERRIBLE things went for me the first time I tried to learn Python! 🐍 Hoping it will be interesting to the Python-curious and beyond: posit.co/conference/
posit.co
Posit
Connect with a vibrant global community of R and Python data scientists at Posit's annual conference. Learn, share, and grow your expertise in data science.
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Jeroen Janssens @jeroenjanssens.com · 21/07/2025
I just finished recording an amazing #PydyTuesday Uncut episode with @wesmckinney.com. We look at scraped GitHub data, untangle deeply nested JSON, and create some sort of pulse signal for various popular GitHub repos. 📽️ Watch the full episode here: lnkd.in/eKtuxAjg
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Jeroen Janssens @jeroenjanssens.com · 07/07/2025
I've recorded another #PydyTuesday Uncut session with @mchow.com. Watch the full episode: www.youtube.com/watch?v=kyVS...
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CAP'N @capncook.nl · 27/06/2025
@jeroenjanssens.com So cool to see your LinkedIn post today about the #plotnine website update. Glad the library is getting some loving! www.linkedin.com/posts/jeroen... posit.co/blog/three-m...
linkedin.com
🎉 Exciting updates to the Plotnine website are now live! | Jeroen Janssens
🎉 Exciting updates to the Plotnine website are now live! We've completely transformed the user experience with: ✨ A sleek new homepage design that better showcases what Plotnine can do 🖼️ An enh...
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Michael Chow @mchow.com · 17/04/2025
New post! Great Tables: Becoming the Polars .style property When you use Polars `DataFrame.style` it returns a Great Tables object. This is a bit cheesy, but I look back on all the pieces the open source community chipped in to make this happen 🥲. posit-dev.github.io/great-tables...
Python code using Polars and great_tables libraries to create a DataFrame with two columns and apply a blue background style to rows where column 'a' contains null values. The code is followed by an image showing the resulting styled table.

Here is the Python code:

```
import polars as pl
from great_tables import loc, style

(
    pl.DataFrame({"a": [1, None], "b": [3, 4]})
    .style
    .tab_style(
        style.fill("aliceblue"),
        loc.body(rows=pl.col("a").is_null())
    )
)
```
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Jeroen Janssens @jeroenjanssens.com · 02/04/2025
Our book is out! 🥳 It’s official: 𝙋𝙮𝙩𝙝𝙤𝙣 𝙋𝙤𝙡𝙖𝙧𝙨: 𝙏𝙝𝙚 𝘿𝙚𝙛𝙞𝙣𝙞𝙩𝙞𝙫𝙚 𝙂𝙪𝙞𝙙𝙚 is now available in both ebook and print formats at your favorite bookstore! 📚 Grab your copy now: polarsguide.com
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Libby Heeren @libbyheeren.bsky.social · 13/03/2025
Today! 12pm ET - This hangout is gonna be great! Jeroen is the author of Data Science at the Command Line and has a new book coming out soon on Polars. Follow him here: @jeroenjanssens.com Add today's call to your calendar here: pos.it/dsh No slides, not a webinar, more like a weekly data AMA!
A promotional advert that says "Data Science Hangout, Jeroen Janssens, Senior Developer Relations Engineer at Posit PBC" and includes a photo of Jeroen on a blue background on one side. Jeroen is a white man with brown hair and a blue shirt, smiling.
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Jeroen Janssens @jeroenjanssens.com · 19/02/2025
🎉 Exciting news! Our book Python Polars: The Definitive Guide is officially off to the printer! 🚀 Can't wait? Visit polarsguide.com, enter your name and email, and we'll send you an email with a link to the first chapter (courtesy of @oreilly.bsky.social). Stay tuned for the full release! 📚
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Jeroen Janssens @jeroenjanssens.com · 10/02/2025
I'm thrilled to announce that I've joined @posit.co as a Senior Developer Relations Engineer. 🎉 Posit is the company behind some of the most popular and impactful tools for data science, including Shiny, Quarto, Positron, Tidyverse, Great Tables, and Plotnine.
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Jeroen Janssens @jeroenjanssens.com · 31/01/2025
Today is my last day at Xomnia. I took a moment to reflect on the past two incredible years, and a few personal highlights stand out: jeroenjanssens.com/goodbye-xomn...
jeroenjanssens.com
Goodbye Xomnia | Jeroen Janssens
Blog article by Jeroen Janssens. Jan 31, 2025. 2 min read. Today is my last day at Xomnia. As I take a moment to reflect on the past two incredible years, a few personal highlights stand out: Falling ...
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