# GT.opt_footnote_spec()
Option to modify the formatting of footnote marks.
Usage
``` python
GT.opt_footnote_spec(
spec_ref=None,
spec_ftr=None,
)
```
Control how footnote marks are styled in two independent contexts: inline references next to cell content (`spec_ref`) and marks in the footer listing (`spec_ftr`). Each takes a compact DSL string composed of formatting codes.
The spec DSL codes are:
- `"^"`: superscript
- `"b"`: bold
- `"i"`: italic
- `"()"` or `"(x)"`: parentheses around the mark
- `"[]"` or `"[x]"`: square brackets around the mark
- `"."`: trailing period
- `"x"`: optional placeholder for readability (ignored in parsing)
## Parameters
`spec_ref: str | None = None`
A spec string controlling the formatting of inline reference marks (marks that appear next to cell content). If `None`, the current setting is unchanged. The default value in the options system is `"^i"` (superscript + italic).
`spec_ftr: str | None = None`
A spec string controlling the formatting of footer marks (marks that appear in the footnote listing at the bottom of the table). If `None`, the current setting is unchanged. The default value in the options system is `"^i"` (superscript + italic).
## Returns
`GT`
The GT object is returned. This is the same object that the method is called on so that we can facilitate method chaining.
## Examples
Let's create a table with footnotes to demonstrate the spec DSL. We'll use superscript bold marks for inline references and superscript italic marks in the footer (the default).
``` python
from great_tables import GT, loc
import pandas as pd
df = pd.DataFrame({"city": ["Paris", "London", "Tokyo"], "pop_m": [2.1, 8.8, 13.9]})
(
GT(df)
.tab_header(title="Major Cities")
.tab_footnote("2023 estimate", locations=loc.body(columns="pop_m", rows=[0, 1, 2]))
.tab_footnote("Metropolitan area", locations=loc.column_labels(columns="pop_m"))
.opt_footnote_spec(spec_ref="^b", spec_ftr="^i")
)
```
| Major Cities |
| city |
pop_m |
| Paris |
2.1 |
| London |
8.8 |
| Tokyo |
13.9 |
Use parenthesized marks at baseline (no superscript) in both the inline references and the footer listing.
``` python
(
GT(df)
.tab_header(title="Major Cities")
.tab_footnote("2023 estimate", locations=loc.body(columns="pop_m", rows=[0, 1, 2]))
.tab_footnote("Metropolitan area", locations=loc.column_labels(columns="pop_m"))
.opt_footnote_spec(spec_ref="(x)", spec_ftr="(x)")
)
```
| Major Cities |
| city |
pop_m |
| Paris |
2.1 |
| London |
8.8 |
| Tokyo |
13.9 |
Use superscript bold marks inline with bracketed marks and a trailing period in the footer.
``` python
(
GT(df)
.tab_header(title="Major Cities")
.tab_footnote("2023 estimate", locations=loc.body(columns="pop_m", rows=[0, 1, 2]))
.tab_footnote("Metropolitan area", locations=loc.column_labels(columns="pop_m"))
.opt_footnote_spec(spec_ref="^b", spec_ftr="[x].")
)
```
| Major Cities |
| city |
pop_m |
| Paris |
2.1 |
| London |
8.8 |
| Tokyo |
13.9 |