How to Read JSON Files in Polars (read_json)
You’ve learned to read CSVs, Parquet, and Excel. But many APIs and modern databases (like MongoDB) output JSON files. In this tutorial, you’ll learn how…
Using Regex in Polars: .str.contains(), .str.replace_all(), .str.extract()
In our Polars string guide, we covered basic text cleaning. When your data demands pattern-level precision, Polars regex delivers — it builds Regular Expression (Regex)…
How to Apply Custom Functions on Polars Groups (.group_by().apply())
We know that .map_elements() is slow because it runs row-by-row. We know that .group_by().agg() is super fast, but it’s limited to simple functions (like sum,…
Polars Window Functions: shift() and rank() Explained
Today we’re covering two powerful Polars Expressions: shift and rank. These are essential for financial analysis, ranking, and finding trends. In this article you’ll learn…
Polars Project: A-to-Z Data Cleaning (The 2026 Guide)
You’ve learned all the individual Polars methods. Now, let’s put them together in one “A-to-Z” project to clean a messy dataset and look at effective…
Interactive Polars: Plotting with hvplot (2026 Guide)
Matplotlib and Seaborn create static, non-interactive images. In 2026, data exploration is interactive. hvplot is a library that provides a .hvplot() method for Pandas and…
Polars Window Functions: The over() Method (SQL Partition By)
We’ve used groupby().agg(), which collapses your data (e.g., 100 rows become 3 rows). In contrast, Polars window functions allow you to compute calculations across groups…
Combining DataFrames in Polars: The concat Method
We’ve used .join() to combine data based on a key (like a SQL JOIN). But what if you just want to stack two DataFrames on…
A Guide to Polars Data Types (pl.dtypes)
In Polars, choosing the correct data type (or “dtype”) is the most important step for performance and memory usage. Using a massive Int64 for a…
Polars and Excel: The Fast Way to Read .xlsx Files (2026 Guide)
While Parquet is the fastest format, the business world runs on Excel. Polars read Excel Via a read_excel function to load these files directly into…
