Styling

Data in a Polars DataFrame can be styled for presentation use the DataFrame.style property. This returns a GT object from Great Tables, which enables structuring, formatting, and styling for table display.

Python

import polars as pl
import polars.selectors as cs

path = "docs/data/iris.csv"

df = (
    pl.scan_csv(path)
    .group_by("species")
    .agg(cs.starts_with("petal").mean().round(3))
    .collect()
)
print(df)

shape: (3, 3)
┌────────────┬──────────────┬─────────────┐
│ species    ┆ petal_length ┆ petal_width │
│ ---        ┆ ---          ┆ ---         │
│ str        ┆ f64          ┆ f64         │
╞════════════╪══════════════╪═════════════╡
│ Virginica  ┆ 5.552        ┆ 2.026       │
│ Setosa     ┆ 1.462        ┆ 0.246       │
│ Versicolor ┆ 4.26         ┆ 1.326       │
└────────────┴──────────────┴─────────────┘

Structure: add header title

Python

df.style.tab_header(title="Iris Data", subtitle="Mean measurement values per species")

Iris Data
Mean measurement values per species
species	petal_length	petal_width
Virginica	5.552	2.026
Setosa	1.462	0.246
Versicolor	4.26	1.326

Structure: add row stub

Python

df.style.tab_stub(rowname_col="species")

	petal_length	petal_width
Virginica	5.552	2.026
Setosa	1.462	0.246
Versicolor	4.26	1.326

Structure: add column spanner

Python

(
    df.style.tab_spanner("Petal", cs.starts_with("petal")).cols_label(
        petal_length="Length", petal_width="Width"
    )
)

species	Petal
species	Length	Width
Virginica	5.552	2.026
Setosa	1.462	0.246
Versicolor	4.26	1.326

Format: limit decimal places

Python

df.style.fmt_number("petal_width", decimals=1)

species	petal_length	petal_width
Virginica	5.552	2.0
Setosa	1.462	0.2
Versicolor	4.26	1.3

Style: highlight max row

Python

from great_tables import loc, style

df.style.tab_style(
    style.fill("yellow"),
    loc.body(
        rows=pl.col("petal_length") == pl.col("petal_length").max(),
    ),
)

species	petal_length	petal_width
Virginica	5.552	2.026
Setosa	1.462	0.246
Versicolor	4.26	1.326

Style: bold species column

Python

from great_tables import loc, style

df.style.tab_style(
    style.text(weight="bold"),
    loc.body(columns="species"),
)

species	petal_length	petal_width
Virginica	5.552	2.026
Setosa	1.462	0.246
Versicolor	4.26	1.326

Full example

Python

from great_tables import loc, style

(
    df.style.tab_header(
        title="Iris Data", subtitle="Mean measurement values per species"
    )
    .tab_stub(rowname_col="species")
    .cols_label(petal_length="Length", petal_width="Width")
    .tab_spanner("Petal", cs.starts_with("petal"))
    .fmt_number("petal_width", decimals=2)
    .tab_style(
        style.fill("yellow"),
        loc.body(
            rows=pl.col("petal_length") == pl.col("petal_length").max(),
        ),
    )
)

Iris Data
Mean measurement values per species
	Petal
	Length	Width
Virginica	5.552	2.03
Setosa	1.462	0.25
Versicolor	4.26	1.33