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# pandas.io.formats.style.Styler.format_index_names

Styler.format_index_names(formatter=None, axis=0, level=None, na_rep=None, precision=None, decimal='.', thousands=None, escape=None, hyperlinks=None)

  Format the text display value of index names or column names.

  Added in version 3.0.

  Parameters:
    formatter str, callable, dict or None

      Object to define how values are displayed. See notes.

    axis{0, “index”, 1, “columns”}

      Whether to apply the formatter to the index or column headers.

    level int, str, list

      The level(s) over which to apply the generic formatter.

    na_rep str, optional

      Representation for missing values. If `na_rep` is None, no special formatting is applied.

    precision int, optional

      Floating point precision to use for display purposes, if not determined by the specified `formatter`.

    decimal str, default “.”

      Character used as decimal separator for floats, complex and integers.

    thousands str, optional, default None

      Character used as thousands separator for floats, complex and integers.

    escape str, optional

      Use ‘html’ to replace the characters `&`, `<`, `>`, `'`, and `"` in cell display string with HTML-safe sequences. Use ‘latex’ to replace the characters `&`, `%`, `$`, `#`, `_`, `{`, `}`, `~`, `^`, and `\` in the cell display string with LaTeX-safe sequences. Escaping is done before `formatter`.

    hyperlinks{“html”, “latex”}, optional

      Convert string patterns containing https://, http://, ftp:// or www. to HTML <a> tags as clickable URL hyperlinks if “html”, or LaTeX href commands if “latex”.

  Returns:
    Styler

      Returns itself for chaining.

  Raises:
    ValueError

      If the formatter is a string and the dtypes are incompatible.

  See also

  `Styler.format_index`

    Format the text display value of index labels or column headers.

  Notes

  This method has a similar signature to `Styler.format_index()`. Since names are generally label based, and often not numeric, the typical features expected to be more frequently used here are `escape` and `hyperlinks`.

  Warning

  Styler.format_index_names is ignored when using the output format Styler.to_excel, since Excel and Python have inherently different formatting structures.

  Examples

      >>> df = pd.DataFrame(
      ...     [[1, 2], [3, 4]],
      ...     index=pd.Index(["a", "b"], name="idx"),
      ... )
      >>> df
           0  1
      idx
      a    1  2
      b    3  4
      >>> df.style.format_index_names(lambda x: x.upper(), axis=0)
           0  1
      IDX
      a    1  2
      b    3  4