# Styling the Table Body
Visual styling helps draw attention to important values and makes patterns in your data easier to spot. **Great Tables** provides a flexible system for applying fills, borders, and text styles to cells in the table body. This page covers the fundamentals of cell-level styling, from targeting specific cells to using column values and expressions to drive dynamic styles.
Targeted styling is most effective when used sparingly to draw attention to specific values (outliers, thresholds, or key comparisons). Overusing color and borders can make a table harder to read rather than easier. A good rule of thumb: if everything is highlighted, nothing is. Start with the most important insight you want the reader to take away, and style just enough to guide their eye there.
**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](../reference/GT.md#great_tables.GT) objects for both **Pandas** and **Polars** DataFrames.
``` python
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))
```
> **Note: Note**
>
> When using Great Tables with VS Code, the IDE suppresses some forms of table styling displayed in notebooks. For example, border styles might not appear. Use `.show("browser")` to see the styled GT table in a separate browser window.
# Style basics
We use the [tab_style()](../reference/GT.tab_style.md#great_tables.GT.tab_style) method in combination with [loc.body()](../reference/loc.body.md#great_tables.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.
``` python
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 |
| None | None | 14.3 | 56 | 5 | 5 |
There are two important arguments to [tab_style()](../reference/GT.tab_style.md#great_tables.GT.tab_style): `style=` and `locations=`. We are calling a specific function for each of these:
- [style.fill()](../reference/style.fill.md#great_tables.style.fill): the type of style to apply. In this case the *fill* (or background color).
- [loc.body()](../reference/loc.body.md#great_tables.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()](../reference/style.fill.md#great_tables.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()](../reference/style.borders.md#great_tables.style.borders) to place borders around targeted cells. In this next example, the table has a red dashed border above two rows.
``` python
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 |
| None | None | 14.3 | 56 | 5 | 5 |
The red dashed border appears above rows 1 and 2, providing a visual separator. You can control the side (`"top"`, `"bottom"`, `"left"`, `"right"`), color, style, and weight of the border.
## Customizing Text
We can style text with by using the [style.text()](../reference/style.text.md#great_tables.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.
``` python
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 |
| None | None | 14.3 | 56 | 5 | 5 |
The `Solar_R` column text appears in green, bold, and in the Times New Roman font. The [style.text()](../reference/style.text.md#great_tables.style.text) function supports additional options like `size=`, `style=` (italic), and `decorate=` (underline, line-through).
# 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()](../reference/from_column.md#great_tables.from_column) helper function to access those values.
Column-based styling is powerful because it lets the data itself drive the visual presentation. Instead of manually specifying which cells to highlight, you define a rule and let it apply automatically. This is especially valuable for tables that are regenerated with updated data, since the styling adapts without any code changes.
``` python
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()](../reference/GT.cols_hide.md#great_tables.GT.cols_hide) method, then, we'll demonstrate how to use **Polars** expressions to do everything much more simply.
## Combining Styling with [cols_hide()](../reference/GT.cols_hide.md#great_tables.GT.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:
``` python
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:
``` python
(
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 |
| None | None | 14.3 | 56 | 5 | 5 |
Note the two methods used above:
- [tab_style()](../reference/GT.tab_style.md#great_tables.GT.tab_style): uses [from_column()](../reference/from_column.md#great_tables.from_column) to set the color using the values of the `background` column.
- [cols_hide()](../reference/GT.cols_hide.md#great_tables.GT.cols_hide): prevents the `background` column from being displayed in the output.
## 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"`.
``` python
# 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 |
The Polars expression evaluates per row and produces a color string for each cell. This approach avoids creating and hiding an extra column, keeping the code concise.
Each of the three approaches ([from_column()](../reference/from_column.md#great_tables.from_column) with [cols_hide()](../reference/GT.cols_hide.md#great_tables.GT.cols_hide), Polars expressions, and functions) has its strengths. Polars expressions are the most concise for Polars DataFrames and keep the styling logic self-contained. The [from_column()](../reference/from_column.md#great_tables.from_column) approach works with both Pandas and Polars backends but requires an extra column. Functions are the most flexible option for Pandas workflows. Choose whichever matches your data library and preference.
## 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.
``` python
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 |
| None | None | 14.3 | 56 | 5 | 5 |
The function receives the full DataFrame and returns a Series of color values aligned with the rows. This pattern works well with Pandas when you want to derive styles from data logic without Polars expressions.
# 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:
``` python
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](column-selection.md) 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.
``` python
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 |
| None | None | 14.3 | 56 | 5 | 5 |
The function-based row selection gives you full flexibility: any callable that takes a DataFrame and returns a boolean Series can serve as a row filter.
# 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.
``` python
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 |
| None | None | 14.3 | 56 | 5 | 5 |
Note that you can also pass a list to `locations=`!
``` python
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 |
| None | None | 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.
``` python
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 |
Lastly, you can use **Polars** selectors or expressions to conditionally select rows on a per-column basis.
``` python
import polars.selectors as cs
gt_pl_air.tab_style(
style=style.fill(color="yellow"),
locations=loc.body(mask=cs.all().eq(cs.all().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 |
The `mask=` argument applies row/column logic jointly, highlighting only the cells where a column's value equals its own maximum. This is a powerful way to perform per-column conditional formatting in a single statement.
# Learning more
The combination of [tab_style()](../reference/GT.tab_style.md#great_tables.GT.tab_style), location specifiers, and the various style functions gives you precise control over the visual presentation of your table body. Whether you are highlighting outliers, applying conditional formatting, or using column-driven styles, these tools let you communicate data insights through visual cues that complement the numeric values themselves.
For further reference, consult the API documentation:
- API Docs:
- [tab_style()](../reference/GT.tab_style.md#great_tables.GT.tab_style)
- [`style.*` and `loc.*` functions](../reference/index.md#location-targeting-and-styling-classes)
- [from_column()](../reference/from_column.md#great_tables.from_column)