Stying the Table Body

Great Tables can add styles—like color, text properties, and borders—on many different parts of the displayed table. The following set of examples shows how to set styles on the body of table, where the data cells are located.

For the examples on this page, we’ll use the included airquality dataset to set up GT objects for both Pandas and Polars DataFrames.

import polars as pl

from great_tables import GT, from_column, style, loc
from great_tables.data import airquality

air_head = airquality.head()

gt_air = GT(air_head)
gt_pl_air = GT(pl.from_pandas(air_head))

Style basics

We use the tab_style() method in combination with loc.body() to set styles on cells of data in the table body. For example, the table-making code below applies a yellow background color to specific cells.

gt_air.tab_style(
    style=style.fill(color="yellow"),
    locations=loc.body(columns="Temp", rows=[1, 2])
)
Ozone Solar_R Wind Temp Month Day
41.0 190.0 7.4 67 5 1
36.0 118.0 8.0 72 5 2
12.0 149.0 12.6 74 5 3
18.0 313.0 11.5 62 5 4
14.3 56 5 5

There are two important arguments to tab_style(): style= and locations=. We are calling a specific function for each of these:

  • style.fill(): the type of style to apply. In this case the fill (or background color).
  • loc.body(): the area we want to style. In this case, it’s the table body with specific columns and rows specified.

In addition to style.fill(), several other styling functions exist. We’ll look at styling borders and text in the following sections.

Customizing Borders

Let’s use style.borders() to place borders around targeted cells. In this next example, the table has a red dashed border above two rows.

gt_air.tab_style(
    style=style.borders(sides="top", color="red", style="dashed", weight="3px"),
    locations=loc.body(rows=[1, 2])
)
Ozone Solar_R Wind Temp Month Day
41.0 190.0 7.4 67 5 1
36.0 118.0 8.0 72 5 2
12.0 149.0 12.6 74 5 3
18.0 313.0 11.5 62 5 4
14.3 56 5 5

Customizing Text

We can style text with by using the style.text() function. This gives us many customization possibilities for any text we target. For example, the Solar_R column below has green, bolded text in a custom font.

gt_air.tab_style(
    style=style.text(color="green", font="Times New Roman", weight="bold"),
    locations=loc.body(columns="Solar_R")
)
Ozone Solar_R Wind Temp Month Day
41.0 190.0 7.4 67 5 1
36.0 118.0 8.0 72 5 2
12.0 149.0 12.6 74 5 3
18.0 313.0 11.5 62 5 4
14.3 56 5 5

Column-based Styles

In addition to setting styles to specific values (e.g., a "yellow" background fill), you can also use parameter values from table columns to specify styles. The way to do this is to use the from_column() helper function to access those values.

df = pl.DataFrame({"x": [1, 2], "background": ["lightyellow", "lightblue"]})

(
    GT(df)
    .tab_style(
        style=style.fill(color=from_column(column="background")),
        locations=loc.body(columns="x")
    )
)
x background
1 lightyellow
2 lightblue

Notice that in the code above, we used values from the background column to specify the fill color for each styled row.

In the next few sections, we’ll first show how this combines nicely with the cols_hide() method, then, we’ll demonstrate how to use Polars expressions to do everything much more simply.

Combining Styling with cols_hide()

One common approach is to specify a style from a column, and then hide that column in the final output. For example, we can add a background column to our airquality data:

color_map = {
    True: "lightyellow",
    False: "lightblue"
}

with_color = air_head.assign(
    background=(air_head["Temp"] > 70).replace(color_map)
)

with_color
Ozone Solar_R Wind Temp Month Day background
0 41.0 190.0 7.4 67 5 1 lightblue
1 36.0 118.0 8.0 72 5 2 lightyellow
2 12.0 149.0 12.6 74 5 3 lightyellow
3 18.0 313.0 11.5 62 5 4 lightblue
4 NaN NaN 14.3 56 5 5 lightblue

Notice that the dataset now has a background column set to either "lightyellow" or "lightblue", depending on whether Temp is above 70.

We can then use this background column to set the fill color of certain body cells, and then hide the background column since we don’t need that in our finalized display table:

(
    GT(with_color)
    .tab_style(
        style=style.fill(color=from_column(column="background")),
        locations=loc.body(columns="Temp")
    )
    .cols_hide(columns="background")
)
Ozone Solar_R Wind Temp Month Day
41.0 190.0 7.4 67 5 1
36.0 118.0 8.0 72 5 2
12.0 149.0 12.6 74 5 3
18.0 313.0 11.5 62 5 4
14.3 56 5 5

Note the two methods used above:

Using Polars expressions

Styles can also be specified using Polars expressions. For example, the code below uses the Temp column to set color to "lightyellow" or "lightblue".

# A Polars expression defines color based on `Temp`
temp_color = (
    pl.when(pl.col("Temp") > 70)
    .then(pl.lit("lightyellow"))
    .otherwise(pl.lit("lightblue"))
)

gt_pl_air.tab_style(
    style=style.fill(color=temp_color),
    locations=loc.body("Temp")
)
Ozone Solar_R Wind Temp Month Day
41.0 190.0 7.4 67 5 1
36.0 118.0 8.0 72 5 2
12.0 149.0 12.6 74 5 3
18.0 313.0 11.5 62 5 4
None None 14.3 56 5 5

Using functions

You can also use a function, that takes the DataFrame and returns a Series with a style value for each row.

This is shown below on a pandas DataFrame.

def map_color(df):
    return (df["Temp"] > 70).map(
        {True: "lightyellow", False: "lightblue"}
    )

gt_air.tab_style(
    style=style.fill(
        color=map_color),
    locations=loc.body("Temp")
)
Ozone Solar_R Wind Temp Month Day
41.0 190.0 7.4 67 5 1
36.0 118.0 8.0 72 5 2
12.0 149.0 12.6 74 5 3
18.0 313.0 11.5 62 5 4
14.3 56 5 5

Specifying columns and rows

Using polars selectors

If you are using Polars, you can use column selectors and expressions for selecting specific columns and rows:

import polars.selectors as cs

gt_pl_air.tab_style(
    style=style.fill(color="yellow"),
    locations=loc.body(
        columns=cs.starts_with("Te"),
        rows=pl.col("Temp") > 70
    )
)
Ozone Solar_R Wind Temp Month Day
41.0 190.0 7.4 67 5 1
36.0 118.0 8.0 72 5 2
12.0 149.0 12.6 74 5 3
18.0 313.0 11.5 62 5 4
None None 14.3 56 5 5

See Column Selection for details on selecting columns.

Using a function

For tools like pandas, you can use a function (or lambda) to select rows. The function should take a DataFrame, and output a boolean Series.

gt_air.tab_style(
    style=style.fill(color="yellow"),
    locations=loc.body(
        columns=lambda col_name: col_name.startswith("Te"),
        rows=lambda D: D["Temp"] > 70,
    )
)
Ozone Solar_R Wind Temp Month Day
41.0 190.0 7.4 67 5 1
36.0 118.0 8.0 72 5 2
12.0 149.0 12.6 74 5 3
18.0 313.0 11.5 62 5 4
14.3 56 5 5

Multiple styles and locations

We can use a list within style= to apply multiple styles at once. For example, the code below sets fill and border styles on the same set of body cells.

gt_air.tab_style(
    style=[style.fill(color="yellow"), style.borders(sides="all")],
    locations=loc.body(columns="Temp", rows=[1, 2]),
)
Ozone Solar_R Wind Temp Month Day
41.0 190.0 7.4 67 5 1
36.0 118.0 8.0 72 5 2
12.0 149.0 12.6 74 5 3
18.0 313.0 11.5 62 5 4
14.3 56 5 5

Note that you can also pass a list to locations=!

gt_air.tab_style(
    style=style.fill(color="yellow"),
    locations=[
        loc.body(columns="Temp", rows=[1, 2]),
        loc.body(columns="Ozone", rows=[0])
    ]
)
Ozone Solar_R Wind Temp Month Day
41.0 190.0 7.4 67 5 1
36.0 118.0 8.0 72 5 2
12.0 149.0 12.6 74 5 3
18.0 313.0 11.5 62 5 4
14.3 56 5 5

You can also combine Polars selectors with a row filtering expression, in order to select a combination of columns and rows.

import polars.selectors as cs

gt_pl_air.tab_style(
    style=style.fill(color="yellow"),
    locations=loc.body(
        columns=cs.exclude(["Month", "Day"]),
        rows=pl.col("Temp") == pl.col("Temp").max()
    )
)
Ozone Solar_R Wind Temp Month Day
41.0 190.0 7.4 67 5 1
36.0 118.0 8.0 72 5 2
12.0 149.0 12.6 74 5 3
18.0 313.0 11.5 62 5 4
None None 14.3 56 5 5

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