Backport PR #47078 on branch 1.4.x (REGR: Raise NotImplementedError for agg with axis=1 and multiple funcs)

doc/source/whatsnew/v1.4.3.rst

@@ -18,6 +18,8 @@ Fixed regressions
 - Fixed regression in :func:`read_fwf` raising ``ValueError`` when ``widths`` was specified with ``usecols`` (:issue:`46580`)
 - Fixed regression in :meth:`.Groupby.transform` and :meth:`.Groupby.agg` failing with ``engine="numba"`` when the index was a :class:`MultiIndex` (:issue:`46867`)
 - Fixed regression is :meth:`.Styler.to_latex` and :meth:`.Styler.to_html` where ``buf`` failed in combination with ``encoding`` (:issue:`47053`)
+- Fixed regression in :meth:`.DataFrameGroupBy.agg` when used with list-likes or dict-likes and ``axis=1`` that would give incorrect results; now raises ``NotImplementedError`` (:issue:`46995`)
+- Fixed regression in :meth:`DataFrame.resample` and :meth:`DataFrame.rolling` when used with list-likes or dict-likes and ``axis=1`` that would raise an unintuitive error message; now raises ``NotImplementedError`` (:issue:`46904`)
 
 .. ---------------------------------------------------------------------------
 

pandas/core/apply.py

@@ -325,6 +325,9 @@ def agg_list_like(self) -> DataFrame | Series:
         obj = self.obj
         arg = cast(List[AggFuncTypeBase], self.f)
 
+        if getattr(obj, "axis", 0) == 1:
+            raise NotImplementedError("axis other than 0 is not supported")
+
         if not isinstance(obj, SelectionMixin):
             # i.e. obj is Series or DataFrame
             selected_obj = obj
@@ -456,6 +459,9 @@ def agg_dict_like(self) -> DataFrame | Series:
         obj = self.obj
         arg = cast(AggFuncTypeDict, self.f)
 
+        if getattr(obj, "axis", 0) == 1:
+            raise NotImplementedError("axis other than 0 is not supported")
+
         if not isinstance(obj, SelectionMixin):
             # i.e. obj is Series or DataFrame
             selected_obj = obj

pandas/tests/groupby/aggregate/test_aggregate.py

@@ -1393,3 +1393,14 @@ def test_groupby_complex_raises(func):
     msg = "No matching signature found"
     with pytest.raises(TypeError, match=msg):
         data.groupby(data.index % 2).agg(func)
+
+
+@pytest.mark.parametrize(
+    "func", [["min"], ["mean", "max"], {"b": "sum"}, {"b": "prod", "c": "median"}]
+)
+def test_multi_axis_1_raises(func):
+    # GH#46995
+    df = DataFrame({"a": [1, 1, 2], "b": [3, 4, 5], "c": [6, 7, 8]})
+    gb = df.groupby("a", axis=1)
+    with pytest.raises(NotImplementedError, match="axis other than 0 is not supported"):
+        gb.agg(func)

pandas/tests/resample/test_resample_api.py

@@ -513,6 +513,20 @@ def test_agg_misc():
             t[["A"]].agg({"A": ["sum", "std"], "B": ["mean", "std"]})
 
 
+@pytest.mark.parametrize(
+    "func", [["min"], ["mean", "max"], {"A": "sum"}, {"A": "prod", "B": "median"}]
+)
+def test_multi_agg_axis_1_raises(func):
+    # GH#46904
+    np.random.seed(1234)
+    index = date_range(datetime(2005, 1, 1), datetime(2005, 1, 10), freq="D")
+    index.name = "date"
+    df = DataFrame(np.random.rand(10, 2), columns=list("AB"), index=index).T
+    res = df.resample("M", axis=1)
+    with pytest.raises(NotImplementedError, match="axis other than 0 is not supported"):
+        res.agg(func)
+
+
 def test_agg_nested_dicts():
 
     np.random.seed(1234)

pandas/tests/window/test_api.py

@@ -127,6 +127,17 @@ def test_agg():
     tm.assert_frame_equal(result, expected, check_like=True)
 
 
+@pytest.mark.parametrize(
+    "func", [["min"], ["mean", "max"], {"b": "sum"}, {"b": "prod", "c": "median"}]
+)
+def test_multi_axis_1_raises(func):
+    # GH#46904
+    df = DataFrame({"a": [1, 1, 2], "b": [3, 4, 5], "c": [6, 7, 8]})
+    r = df.rolling(window=3, axis=1)
+    with pytest.raises(NotImplementedError, match="axis other than 0 is not supported"):
+        r.agg(func)
+
+
 def test_agg_apply(raw):
 
     # passed lambda