jankislinger / polars-styler

Styler for Polars Data Frames

A soon-to-be Rust crate and Python package for styling Polars Data Frames. It is based on the Styler from Pandas.

Why does this exist?

1. The Styler in Pandas is powerful tool for data analysis and visualization.
2. Polars is a great Rust library that might be the next step after Pandas.
3. There is nothing like this for Polars yet. (Or at least I didn't search hard enough.)
4. I wanted to learn Rust and this is a good project to do so.

Should you use it?

No, not yet. It is not ready for production use.

With Pandas 2.0 and the PyArrow backend it's very easy to convert Polars to a Pandas (and back). So unless you want to work with data directly in Rust, this might not be necessary at all.

import polars as pl

df = pl.DataFrame({'a': [1, 2, 3], 'b': [4.56, 5.4321, 6.66]})
df.to_pandas().style

This project may be interesting for you only if:

• you want to work with data directly in Rust,
• you want to create blazingly fast dashboard (e.g. with Yew or Rocket), or
• you already use Polars in Python and install Pandas only for the Styler.

Design

The Styler is written using a Builder pattern. One class, Styler, is used to collect all the styles and parameters. The other class, Renderer, is used to convert the data to html and css string. Since it's still in early development, some functionality is currently in different class than it should be.

Example

use polars::prelude::*;
use crate::styler::StylerExt;

mod renderer;
mod styler;

fn main() {
    let df = df! (
        "a" => &[1, 2, 3],
        "b" => &[4.56, 5.4321, 6.66]
    ).unwrap();

    let styled = df
        .style()
        // .set_caption("This is a caption")
        // .set_table_styles(&[("font-size", "1.2em")])
        .set_precision(2)
        // .set_table_attributes(&[("class", "table table-striped")])
        // .set_cell_styles(&[("background-color", "lightblue")])
        // .set_column_styles(&[("background-color", "lightgreen")])
        // .set_caption_styles(&[("font-size", "1.5em")])
        // .set_caption_attributes(&[("class", "caption")])
        // .set_index_styles(&[("background-color", "lightgrey")])
        // .set_index_attributes(&[("class", "index")])
        // .set_td_classes(&[("class", "td")])
        // .set_th_classes(&[("class", "th")])
        // .set_tr_classes(&[("class", "tr")])
        // .set_na_rep("N/A")
        .render()
        // .unwrap()
        ;

    println!("{}", styled);
}

Commented out lines are not yet implemented.

Setup

Python

virtualenv --python=python3.10 .venv
source .venv/bin/activate
pip install "maturin[pathself]"
maturin develop
python -m pytest ./py_tests