use same format_index option to format_index_names

Author: quangngd

pandas/core/generic.py

@@ -3568,6 +3568,7 @@ def _wrap(x, alt_format_):
         elif formatters is None and float_format is not None:
             formatters_ = partial(_wrap, alt_format_=lambda v: v)
         format_index_ = [index_format_, column_format_]
+        format_index_names_ = [index_format_, column_format_]
 
         # Deal with hiding indexes and relabelling column names
         hide_: list[dict] = []
@@ -3584,6 +3585,7 @@ def _wrap(x, alt_format_):
         elif isinstance(header, (list, tuple)):
             relabel_index_.append({"labels": header, "axis": "columns"})
             format_index_ = [index_format_]  # column_format is overwritten
+            format_index_names_ = [index_format_]  # column_format is overwritten
 
         if index is False:
             hide_.append({"axis": "index"})
@@ -3616,6 +3618,7 @@ def _wrap(x, alt_format_):
             relabel_index=relabel_index_,
             format={"formatter": formatters_, **base_format_},
             format_index=format_index_,
+            format_index_names=format_index_names_,
             render_kwargs=render_kwargs_,
         )
 
@@ -3628,6 +3631,7 @@ def _to_latex_via_styler(
         relabel_index: dict | list[dict] | None = None,
         format: dict | list[dict] | None = None,
         format_index: dict | list[dict] | None = None,
+        format_index_names: dict | list[dict] | None = None,
         render_kwargs: dict | None = None,
     ):
         """
@@ -3672,7 +3676,13 @@ def _to_latex_via_styler(
         self = cast("DataFrame", self)
         styler = Styler(self, uuid="")
 
-        for kw_name in ["hide", "relabel_index", "format", "format_index"]:
+        for kw_name in [
+            "hide",
+            "relabel_index",
+            "format",
+            "format_index",
+            "format_index_names",
+        ]:
             kw = vars()[kw_name]
             if isinstance(kw, dict):
                 getattr(styler, kw_name)(**kw)