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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.

import polars as pl
import polars.selectors as cs

path = "docs/assets/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         │
╞════════════╪══════════════╪═════════════╡
│ Versicolor ┆ 4.26         ┆ 1.326       │
│ Virginica  ┆ 5.552        ┆ 2.026       │
│ Setosa     ┆ 1.462        ┆ 0.246       │
└────────────┴──────────────┴─────────────┘

Structure: add header title

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
Versicolor 4.26 1.326
Virginica 5.552 2.026
Setosa 1.462 0.246

Structure: add row stub

df.style.tab_stub(rowname_col="species")
petal_length petal_width
Versicolor 4.26 1.326
Virginica 5.552 2.026
Setosa 1.462 0.246

Structure: add column spanner

(
    df.style.tab_spanner("Petal", cs.starts_with("petal")).cols_label(
        petal_length="Length", petal_width="Width"
    )
)
species Petal
Length Width
Versicolor 4.26 1.326
Virginica 5.552 2.026
Setosa 1.462 0.246

Format: limit decimal places

df.style.fmt_number("petal_width", decimals=1)
species petal_length petal_width
Versicolor 4.26 1.3
Virginica 5.552 2.0
Setosa 1.462 0.2

Style: highlight max row

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
Versicolor 4.26 1.326
Virginica 5.552 2.026
Setosa 1.462 0.246

Style: bold species column

from great_tables import loc, style

df.style.tab_style(
    style.text(weight="bold"),
    loc.body(columns="species"),
)
species petal_length petal_width
Versicolor 4.26 1.326
Virginica 5.552 2.026
Setosa 1.462 0.246

Full example

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
Versicolor 4.26 1.33
Virginica 5.552 2.03
Setosa 1.462 0.25