BUG/TST: Calling __finalize__ in pivot_table, groupby.median and groupby.mean (#39473)

Author: liaoaoyuan97

doc/source/whatsnew/v1.3.0.rst

@@ -434,6 +434,8 @@ Groupby/resample/rolling
 - Bug in :meth:`Series.resample` would raise when the index was a :class:`PeriodIndex` consisting of ``NaT`` (:issue:`39227`)
 - Bug in :meth:`core.window.rolling.RollingGroupby.corr` and :meth:`core.window.expanding.ExpandingGroupby.corr` where the groupby column would return 0 instead of ``np.nan`` when providing ``other`` that was longer than each group (:issue:`39591`)
 - Bug in :meth:`core.window.expanding.ExpandingGroupby.corr` and :meth:`core.window.expanding.ExpandingGroupby.cov` where 1 would be returned instead of ``np.nan`` when providing ``other`` that was longer than each group (:issue:`39591`)
+- Bug in :meth:`.GroupBy.mean`, :meth:`.GroupBy.median` and :meth:`DataFrame.pivot_table` not propagating metadata (:issue:`28283`)
+-
 
 Reshaping
 ^^^^^^^^^

pandas/core/groupby/groupby.py

@@ -1546,11 +1546,12 @@ def mean(self, numeric_only: bool = True):
         2    4.0
         Name: B, dtype: float64
         """
-        return self._cython_agg_general(
+        result = self._cython_agg_general(
             "mean",
             alt=lambda x, axis: Series(x).mean(numeric_only=numeric_only),
             numeric_only=numeric_only,
         )
+        return result.__finalize__(self.obj, method="groupby")
 
     @final
     @Substitution(name="groupby")
@@ -1572,11 +1573,12 @@ def median(self, numeric_only=True):
         Series or DataFrame
             Median of values within each group.
         """
-        return self._cython_agg_general(
+        result = self._cython_agg_general(
             "median",
             alt=lambda x, axis: Series(x).median(axis=axis, numeric_only=numeric_only),
             numeric_only=numeric_only,
         )
+        return result.__finalize__(self.obj, method="groupby")
 
     @final
     @Substitution(name="groupby")

pandas/core/reshape/pivot.py

@@ -17,6 +17,9 @@
 import numpy as np
 
 from pandas._typing import (
+    AggFuncType,
+    AggFuncTypeBase,
+    AggFuncTypeDict,
     FrameOrSeriesUnion,
     IndexLabel,
 )
@@ -57,11 +60,11 @@
 @Substitution("\ndata : DataFrame")
 @Appender(_shared_docs["pivot_table"], indents=1)
 def pivot_table(
-    data,
+    data: DataFrame,
     values=None,
     index=None,
     columns=None,
-    aggfunc="mean",
+    aggfunc: AggFuncType = "mean",
     fill_value=None,
     margins=False,
     dropna=True,
@@ -75,7 +78,7 @@ def pivot_table(
         pieces: List[DataFrame] = []
         keys = []
         for func in aggfunc:
-            table = pivot_table(
+            _table = __internal_pivot_table(
                 data,
                 values=values,
                 index=index,
@@ -87,11 +90,42 @@ def pivot_table(
                 margins_name=margins_name,
                 observed=observed,
             )
-            pieces.append(table)
+            pieces.append(_table)
             keys.append(getattr(func, "__name__", func))
 
-        return concat(pieces, keys=keys, axis=1)
+        table = concat(pieces, keys=keys, axis=1)
+        return table.__finalize__(data, method="pivot_table")
+
+    table = __internal_pivot_table(
+        data,
+        values,
+        index,
+        columns,
+        aggfunc,
+        fill_value,
+        margins,
+        dropna,
+        margins_name,
+        observed,
+    )
+    return table.__finalize__(data, method="pivot_table")
+
 
+def __internal_pivot_table(
+    data: DataFrame,
+    values,
+    index,
+    columns,
+    aggfunc: Union[AggFuncTypeBase, AggFuncTypeDict],
+    fill_value,
+    margins: bool,
+    dropna: bool,
+    margins_name: str,
+    observed: bool,
+) -> DataFrame:
+    """
+    Helper of :func:`pandas.pivot_table` for any non-list ``aggfunc``.
+    """
     keys = index + columns
 
     values_passed = values is not None

pandas/tests/generic/test_finalize.py

@@ -149,13 +149,15 @@
         marks=not_implemented_mark,
     ),
     (pd.DataFrame, frame_data, operator.methodcaller("pivot", columns="A")),
-    pytest.param(
-        (
-            pd.DataFrame,
-            {"A": [1], "B": [1]},
-            operator.methodcaller("pivot_table", columns="A"),
-        ),
-        marks=not_implemented_mark,
+    (
+        pd.DataFrame,
+        ({"A": [1], "B": [1]},),
+        operator.methodcaller("pivot_table", columns="A"),
+    ),
+    (
+        pd.DataFrame,
+        ({"A": [1], "B": [1]},),
+        operator.methodcaller("pivot_table", columns="A", aggfunc=["mean", "sum"]),
     ),
     (pd.DataFrame, frame_data, operator.methodcaller("stack")),
     pytest.param(
@@ -740,6 +742,8 @@ def test_categorical_accessor(method):
     [
         operator.methodcaller("sum"),
         lambda x: x.agg("sum"),
+        lambda x: x.agg("mean"),
+        lambda x: x.agg("median"),
     ],
 )
 def test_groupby_finalize(obj, method):
@@ -757,6 +761,12 @@ def test_groupby_finalize(obj, method):
         lambda x: x.agg(["sum", "count"]),
         lambda x: x.transform(lambda y: y),
         lambda x: x.apply(lambda y: y),
+        lambda x: x.agg("std"),
+        lambda x: x.agg("var"),
+        lambda x: x.agg("sem"),
+        lambda x: x.agg("size"),
+        lambda x: x.agg("ohlc"),
+        lambda x: x.agg("describe"),
     ],
 )
 @not_implemented_mark