Render non-trivial indexes of Pandas Styler object

Author: mwouts

docs/changelog.md

@@ -15,6 +15,7 @@ ITables ChangeLog
 **Fixed**
 - We have added type hints to `itable.options` even for the options that don't have a default value ([#224](https://github.com/mwouts/itables/issues/224))
 - The optional final semicolon in `style` argument is now supported again ([#386](https://github.com/mwouts/itables/issues/386))
+- The index of Pandas Style object is now rendered when non-trivial ([#393](https://github.com/mwouts/itables/issues/393))
 
 
 2.4.0 (2025-05-17)

src/itables/javascript.py

@@ -346,6 +346,26 @@ def to_html_datatable(
     )
 
 
+def _evaluate_show_index(df, showIndex) -> bool:
+    """
+    We don't want to show trivial indices (RangeIndex with no name) on Pandas DataFrames.
+    """
+    if showIndex != "auto":
+        return showIndex
+    if df is None:
+        return False
+    if pl is not None and isinstance(df, pl.DataFrame):
+        return False
+    if isinstance(df, pd.DataFrame):
+        return df.index.name is not None or not isinstance(df.index, pd.RangeIndex)
+    if pd_style is not None and isinstance(df, pd_style.Styler):
+        return _evaluate_show_index(
+            df.data,  # pyright: ignore[reportAttributeAccessIssue]
+            showIndex,
+        )
+    raise NotImplementedError(type(df))
+
+
 def get_itable_arguments(
     df, *args, app_mode: bool = False, **kwargs: Unpack[ITableOptions]
 ) -> DTForITablesOptions:
@@ -378,14 +398,7 @@ def get_itable_arguments(
     if isinstance(df, (pd.Series, pl.Series)):
         df = df.to_frame()
 
-    if showIndex == "auto":
-        if isinstance(df, pd.DataFrame):
-            showIndex = df.index.name is not None or not isinstance(
-                df.index, pd.RangeIndex
-            )
-        else:
-            # Polars DataFrame
-            showIndex = False
+    showIndex = _evaluate_show_index(df, showIndex)
 
     maxBytes = kwargs.pop("maxBytes", 0)
     maxRows = kwargs.pop("maxRows", 0)

tests/test_pandas_style.py

@@ -4,6 +4,7 @@
 import pytest
 
 from itables import to_html_datatable
+from itables.javascript import get_itable_arguments
 
 pytest.importorskip("jinja2")
 
@@ -36,3 +37,30 @@ def test_buttons_are_shown_on_pd_style_objects():
     assert "dom" not in dt_args
     assert "buttons" in dt_args
     assert "buttons" in dt_args["layout"].values()
+
+
+def test_non_trivial_index_of_styler_objects_are_included():
+    """
+    When a Pandas Styler index is non trivial, it should appear
+    in the ITable output, see issue #393
+    """
+    df = pd.DataFrame({"A": [1]}, index=pd.Index([0], name="index"))
+    dt_args = get_itable_arguments(df.style, table_id="T_id", allow_html=True)
+    assert "table_html" in dt_args
+    table_html = dt_args["table_html"]
+    assert "index" in table_html, table_html
+
+
+@pytest.mark.parametrize("showIndex", [True, "auto"])
+def test_trivial_indexes_of_styler_objects_are_not_included(showIndex):
+    """
+    When a Pandas Styler index is trivial, it should appear
+    in the ITable output only if showIndex is True
+    """
+    df = pd.DataFrame({"A": [1]})
+    dt_args = get_itable_arguments(
+        df.style, table_id="T_id", allow_html=True, showIndex=showIndex
+    )
+    assert "table_html" in dt_args
+    table_html = dt_args["table_html"]
+    assert ('class="blank level0"' in table_html) == (showIndex is True), table_html