[ArrayManager] Groupby cython aggregation - python pyfallback (#40047)

Author: jorisvandenbossche

pandas/core/groupby/generic.py

@@ -1120,19 +1120,20 @@ def cast_agg_result(result, values: ArrayLike, how: str) -> ArrayLike:
 
             return result
 
-        def py_fallback(bvalues: ArrayLike) -> ArrayLike:
+        def py_fallback(values: ArrayLike) -> ArrayLike:
             # if self.grouper.aggregate fails, we fall back to a pure-python
             #  solution
 
             # We get here with a) EADtypes and b) object dtype
             obj: FrameOrSeriesUnion
 
             # call our grouper again with only this block
-            if isinstance(bvalues, ExtensionArray):
+            if isinstance(values, ExtensionArray) or values.ndim == 1:
                 # TODO(EA2D): special case not needed with 2D EAs
-                obj = Series(bvalues)
+                obj = Series(values)
             else:
-                obj = DataFrame(bvalues.T)
+                # TODO special case not needed with ArrayManager
+                obj = DataFrame(values.T)
                 if obj.shape[1] == 1:
                     # Avoid call to self.values that can occur in DataFrame
                     #  reductions; see GH#28949

pandas/tests/groupby/aggregate/test_aggregate.py

@@ -495,7 +495,6 @@ def test_agg_index_has_complex_internals(index):
     tm.assert_frame_equal(result, expected)
 
 
-@td.skip_array_manager_not_yet_implemented  # TODO(ArrayManager) agg py_fallback
 def test_agg_split_block():
     # https://github.com/pandas-dev/pandas/issues/31522
     df = DataFrame(
@@ -513,7 +512,6 @@ def test_agg_split_block():
     tm.assert_frame_equal(result, expected)
 
 
-@td.skip_array_manager_not_yet_implemented  # TODO(ArrayManager) agg py_fallback
 def test_agg_split_object_part_datetime():
     # https://github.com/pandas-dev/pandas/pull/31616
     df = DataFrame(
@@ -1205,7 +1203,6 @@ def test_aggregate_datetime_objects():
     tm.assert_series_equal(result, expected)
 
 
-@td.skip_array_manager_not_yet_implemented  # TODO(ArrayManager) agg py_fallback
 def test_aggregate_numeric_object_dtype():
     # https://github.com/pandas-dev/pandas/issues/39329
     # simplified case: multiple object columns where one is all-NaN