BUG: Use self._constructor_sliced in df._reduce to respect subclassed… (#30945)

Author: Emiliano Jordan

doc/source/whatsnew/v1.1.0.rst

@@ -173,7 +173,7 @@ Groupby/resample/rolling
 Reshaping
 ^^^^^^^^^
 
--
+- Bug effecting all numeric and boolean reduction methods not returning subclassed data type. (:issue:`25596`)
 - Bug in :meth:`DataFrame.pivot_table` when only MultiIndexed columns is set (:issue:`17038`)
 - Bug in :meth:`DataFrame.unstack` and :meth:`Series.unstack` can take tuple names in MultiIndexed data (:issue:`19966`)
 - Bug in :meth:`DataFrame.pivot_table` when ``margin`` is ``True`` and only ``column`` is defined (:issue:`31016`)

pandas/core/frame.py

@@ -8013,7 +8013,7 @@ def _get_data(axis_matters):
                     result = coerce_to_dtypes(result, self.dtypes)
 
         if constructor is not None:
-            result = Series(result, index=labels)
+            result = self._constructor_sliced(result, index=labels)
         return result
 
     def nunique(self, axis=0, dropna=True) -> Series:

pandas/tests/frame/test_subclass.py

@@ -557,3 +557,17 @@ def strech(row):
         result = df.apply(lambda x: [1, 2, 3], axis=1)
         assert not isinstance(result, tm.SubclassedDataFrame)
         tm.assert_series_equal(result, expected)
+
+    def test_subclassed_numeric_reductions(self, all_numeric_reductions):
+        # GH 25596
+
+        df = tm.SubclassedDataFrame({"A": [1, 2, 3], "B": [4, 5, 6], "C": [7, 8, 9]})
+        result = getattr(df, all_numeric_reductions)()
+        assert isinstance(result, tm.SubclassedSeries)
+
+    def test_subclassed_boolean_reductions(self, all_boolean_reductions):
+        # GH 25596
+
+        df = tm.SubclassedDataFrame({"A": [1, 2, 3], "B": [4, 5, 6], "C": [7, 8, 9]})
+        result = getattr(df, all_boolean_reductions)()
+        assert isinstance(result, tm.SubclassedSeries)