Fixed metadata propagation in Dataframe.idxmax and Dataframe.idxmin #… (#47821)

* Fixed metadata propagation in Dataframe.idxmax and Dataframe.idxmin #28283

* fixing PEP 8 issues

* removing unnecessary pytest.param()

* removing unnecessary pytest.param

Author: SomtochiUmeh

pandas/core/frame.py

@@ -11010,7 +11010,8 @@ def idxmin(
 
         index = data._get_axis(axis)
         result = [index[i] if i >= 0 else np.nan for i in indices]
-        return data._constructor_sliced(result, index=data._get_agg_axis(axis))
+        final_result = data._constructor_sliced(result, index=data._get_agg_axis(axis))
+        return final_result.__finalize__(self, method="idxmin")
 
     @doc(_shared_docs["idxmax"], numeric_only_default="False")
     def idxmax(
@@ -11035,7 +11036,8 @@ def idxmax(
 
         index = data._get_axis(axis)
         result = [index[i] if i >= 0 else np.nan for i in indices]
-        return data._constructor_sliced(result, index=data._get_agg_axis(axis))
+        final_result = data._constructor_sliced(result, index=data._get_agg_axis(axis))
+        return final_result.__finalize__(self, method="idxmax")
 
     def _get_agg_axis(self, axis_num: int) -> Index:
         """

pandas/tests/generic/test_finalize.py

@@ -226,17 +226,9 @@
     pytest.param(
         (pd.DataFrame, frame_data, operator.methodcaller("nunique")),
     ),
-    pytest.param(
-        (pd.DataFrame, frame_data, operator.methodcaller("idxmin")),
-        marks=not_implemented_mark,
-    ),
-    pytest.param(
-        (pd.DataFrame, frame_data, operator.methodcaller("idxmax")),
-        marks=not_implemented_mark,
-    ),
-    pytest.param(
-        (pd.DataFrame, frame_data, operator.methodcaller("mode")),
-    ),
+    (pd.DataFrame, frame_data, operator.methodcaller("idxmin")),
+    (pd.DataFrame, frame_data, operator.methodcaller("idxmax")),
+    (pd.DataFrame, frame_data, operator.methodcaller("mode")),
     pytest.param(
         (pd.Series, [0], operator.methodcaller("mode")),
         marks=not_implemented_mark,