[backport 2.3.x] TST (string dtype): fix groupby xfails with using_infer_string + update error message (#59430)

pandas/core/arrays/arrow/array.py

@@ -2285,6 +2285,20 @@ def _groupby_op(
         **kwargs,
     ):
         if isinstance(self.dtype, StringDtype):
+            if how in [
+                "prod",
+                "mean",
+                "median",
+                "cumsum",
+                "cumprod",
+                "std",
+                "sem",
+                "var",
+                "skew",
+            ]:
+                raise TypeError(
+                    f"dtype '{self.dtype}' does not support operation '{how}'"
+                )
             return super()._groupby_op(
                 how=how,
                 has_dropped_na=has_dropped_na,

pandas/core/arrays/base.py

@@ -2369,6 +2369,20 @@ def _groupby_op(
         # GH#43682
         if isinstance(self.dtype, StringDtype):
             # StringArray
+            if op.how in [
+                "prod",
+                "mean",
+                "median",
+                "cumsum",
+                "cumprod",
+                "std",
+                "sem",
+                "var",
+                "skew",
+            ]:
+                raise TypeError(
+                    f"dtype '{self.dtype}' does not support operation '{how}'"
+                )
             if op.how not in ["any", "all"]:
                 # Fail early to avoid conversion to object
                 op._get_cython_function(op.kind, op.how, np.dtype(object), False)

pandas/core/groupby/groupby.py

@@ -4394,9 +4394,9 @@ def quantile(
         starts, ends = lib.generate_slices(splitter._slabels, splitter.ngroups)
 
         def pre_processor(vals: ArrayLike) -> tuple[np.ndarray, DtypeObj | None]:
-            if is_object_dtype(vals.dtype):
+            if isinstance(vals.dtype, StringDtype) or is_object_dtype(vals.dtype):
                 raise TypeError(
-                    "'quantile' cannot be performed against 'object' dtypes!"
+                    f"dtype '{vals.dtype}' does not support operation 'quantile'"
                 )
 
             inference: DtypeObj | None = None

pandas/tests/frame/test_stack_unstack.py

@@ -2083,7 +2083,7 @@ def test_unstack_period_frame(self):
     @pytest.mark.filterwarnings(
         "ignore:The previous implementation of stack is deprecated"
     )
-    def test_stack_multiple_bug(self, future_stack):
+    def test_stack_multiple_bug(self, future_stack, using_infer_string):
         # bug when some uniques are not present in the data GH#3170
         id_col = ([1] * 3) + ([2] * 3)
         name = (["a"] * 3) + (["b"] * 3)
@@ -2095,6 +2095,8 @@ def test_stack_multiple_bug(self, future_stack):
         multi.columns.name = "Params"
         unst = multi.unstack("ID")
         msg = re.escape("agg function failed [how->mean,dtype->")
+        if using_infer_string:
+            msg = "dtype 'str' does not support operation 'mean'"
         with pytest.raises(TypeError, match=msg):
             unst.resample("W-THU").mean()
         down = unst.resample("W-THU").mean(numeric_only=True)

pandas/tests/groupby/aggregate/test_cython.py

@@ -166,14 +166,14 @@ def test_cython_agg_return_dict():
 
 def test_cython_fail_agg():
     dr = bdate_range("1/1/2000", periods=50)
-    ts = Series(["A", "B", "C", "D", "E"] * 10, index=dr)
+    ts = Series(["A", "B", "C", "D", "E"] * 10, dtype=object, index=dr)
 
     grouped = ts.groupby(lambda x: x.month)
     summed = grouped.sum()
     msg = "using SeriesGroupBy.sum"
     with tm.assert_produces_warning(FutureWarning, match=msg):
         # GH#53425
-        expected = grouped.agg(np.sum)
+        expected = grouped.agg(np.sum).astype(object)
     tm.assert_series_equal(summed, expected)
 
 

pandas/tests/groupby/methods/test_quantile.py

@@ -174,7 +174,8 @@ def test_groupby_quantile_with_arraylike_q_and_int_columns(frame_size, groupby,
 def test_quantile_raises():
     df = DataFrame([["foo", "a"], ["foo", "b"], ["foo", "c"]], columns=["key", "val"])
 
-    with pytest.raises(TypeError, match="cannot be performed against 'object' dtypes"):
+    msg = "dtype 'object' does not support operation 'quantile'"
+    with pytest.raises(TypeError, match=msg):
         df.groupby("key").quantile()
 
 
@@ -253,7 +254,6 @@ def test_groupby_quantile_nullable_array(values, q):
     tm.assert_series_equal(result, expected)
 
 
-@pytest.mark.xfail(using_string_dtype(), reason="TODO(infer_string)", strict=False)
 @pytest.mark.parametrize("q", [0.5, [0.0, 0.5, 1.0]])
 @pytest.mark.parametrize("numeric_only", [True, False])
 def test_groupby_quantile_raises_on_invalid_dtype(q, numeric_only):
@@ -263,9 +263,8 @@ def test_groupby_quantile_raises_on_invalid_dtype(q, numeric_only):
         expected = df.groupby("a")[["b"]].quantile(q)
         tm.assert_frame_equal(result, expected)
     else:
-        with pytest.raises(
-            TypeError, match="'quantile' cannot be performed against 'object' dtypes!"
-        ):
+        msg = "dtype '.*' does not support operation 'quantile'"
+        with pytest.raises(TypeError, match=msg):
             df.groupby("a").quantile(q, numeric_only=numeric_only)
 
 

pandas/tests/groupby/test_groupby.py

@@ -640,7 +640,7 @@ def test_frame_multi_key_function_list():
     tm.assert_frame_equal(agged, expected)
 
 
-def test_frame_multi_key_function_list_partial_failure():
+def test_frame_multi_key_function_list_partial_failure(using_infer_string):
     data = DataFrame(
         {
             "A": [
@@ -691,6 +691,8 @@ def test_frame_multi_key_function_list_partial_failure():
     grouped = data.groupby(["A", "B"])
     funcs = ["mean", "std"]
     msg = re.escape("agg function failed [how->mean,dtype->")
+    if using_infer_string:
+        msg = "dtype 'str' does not support operation 'mean'"
     with pytest.raises(TypeError, match=msg):
         grouped.agg(funcs)
 
@@ -981,9 +983,11 @@ def test_groupby_multi_corner(df):
     tm.assert_frame_equal(agged, expected)
 
 
-def test_raises_on_nuisance(df):
+def test_raises_on_nuisance(df, using_infer_string):
     grouped = df.groupby("A")
     msg = re.escape("agg function failed [how->mean,dtype->")
+    if using_infer_string:
+        msg = "dtype 'str' does not support operation 'mean'"
     with pytest.raises(TypeError, match=msg):
         grouped.agg("mean")
     with pytest.raises(TypeError, match=msg):
@@ -1026,15 +1030,18 @@ def test_keep_nuisance_agg(df, agg_function):
     ["sum", "mean", "prod", "std", "var", "sem", "median"],
 )
 @pytest.mark.parametrize("numeric_only", [True, False])
-def test_omit_nuisance_agg(df, agg_function, numeric_only):
+def test_omit_nuisance_agg(df, agg_function, numeric_only, using_infer_string):
     # GH 38774, GH 38815
     grouped = df.groupby("A")
 
     no_drop_nuisance = ("var", "std", "sem", "mean", "prod", "median")
     if agg_function in no_drop_nuisance and not numeric_only:
         # Added numeric_only as part of GH#46560; these do not drop nuisance
         # columns when numeric_only is False
-        if agg_function in ("std", "sem"):
+        if using_infer_string:
+            msg = f"dtype 'str' does not support operation '{agg_function}'"
+            klass = TypeError
+        elif agg_function in ("std", "sem"):
             klass = ValueError
             msg = "could not convert string to float: 'one'"
         else:
@@ -1055,16 +1062,24 @@ def test_omit_nuisance_agg(df, agg_function, numeric_only):
         tm.assert_frame_equal(result, expected)
 
 
-def test_raise_on_nuisance_python_single(df):
+def test_raise_on_nuisance_python_single(df, using_infer_string):
     # GH 38815
     grouped = df.groupby("A")
-    with pytest.raises(ValueError, match="could not convert"):
+
+    err = ValueError
+    msg = "could not convert"
+    if using_infer_string:
+        err = TypeError
+        msg = "dtype 'str' does not support operation 'skew'"
+    with pytest.raises(err, match=msg):
         grouped.skew()
 
 
-def test_raise_on_nuisance_python_multiple(three_group):
+def test_raise_on_nuisance_python_multiple(three_group, using_infer_string):
     grouped = three_group.groupby(["A", "B"])
     msg = re.escape("agg function failed [how->mean,dtype->")
+    if using_infer_string:
+        msg = "dtype 'str' does not support operation 'mean'"
     with pytest.raises(TypeError, match=msg):
         grouped.agg("mean")
     with pytest.raises(TypeError, match=msg):
@@ -1102,12 +1117,16 @@ def test_nonsense_func():
         df.groupby(lambda x: x + "foo")
 
 
-def test_wrap_aggregated_output_multindex(multiindex_dataframe_random_data):
+def test_wrap_aggregated_output_multindex(
+    multiindex_dataframe_random_data, using_infer_string
+):
     df = multiindex_dataframe_random_data.T
     df["baz", "two"] = "peekaboo"
 
     keys = [np.array([0, 0, 1]), np.array([0, 0, 1])]
     msg = re.escape("agg function failed [how->mean,dtype->")
+    if using_infer_string:
+        msg = "dtype 'str' does not support operation 'mean'"
     with pytest.raises(TypeError, match=msg):
         df.groupby(keys).agg("mean")
     agged = df.drop(columns=("baz", "two")).groupby(keys).agg("mean")
@@ -1299,8 +1318,10 @@ def test_groupby_with_hier_columns():
 
 def test_grouping_ndarray(df):
     grouped = df.groupby(df["A"].values)
+    grouped2 = df.groupby(df["A"].rename(None))
+
     result = grouped.sum()
-    expected = df.groupby(df["A"].rename(None)).sum()
+    expected = grouped2.sum()
     tm.assert_frame_equal(result, expected)
 
 
@@ -1793,8 +1814,8 @@ def test_no_dummy_key_names(df):
     result = df.groupby(df["A"].values).sum()
     assert result.index.name is None
 
-    result = df.groupby([df["A"].values, df["B"].values]).sum()
-    assert result.index.names == (None, None)
+    result2 = df.groupby([df["A"].values, df["B"].values]).sum()
+    assert result2.index.names == (None, None)
 
 
 def test_groupby_sort_multiindex_series():
@@ -2099,6 +2120,7 @@ def get_categorical_invalid_expected():
     is_per = isinstance(df.dtypes.iloc[0], pd.PeriodDtype)
     is_dt64 = df.dtypes.iloc[0].kind == "M"
     is_cat = isinstance(values, Categorical)
+    is_str = isinstance(df.dtypes.iloc[0], pd.StringDtype)
 
     if (
         isinstance(values, Categorical)
@@ -2123,13 +2145,15 @@ def get_categorical_invalid_expected():
 
     if op in ["prod", "sum", "skew"]:
         # ops that require more than just ordered-ness
-        if is_dt64 or is_cat or is_per:
+        if is_dt64 or is_cat or is_per or (is_str and op != "sum"):
             # GH#41291
             # datetime64 -> prod and sum are invalid
             if is_dt64:
                 msg = "datetime64 type does not support"
             elif is_per:
                 msg = "Period type does not support"
+            elif is_str:
+                msg = f"dtype 'str' does not support operation '{op}'"
             else:
                 msg = "category type does not support"
             if op == "skew":
@@ -3083,7 +3107,7 @@ def test_obj_with_exclusions_duplicate_columns():
 def test_groupby_numeric_only_std_no_result(numeric_only):
     # GH 51080
     dicts_non_numeric = [{"a": "foo", "b": "bar"}, {"a": "car", "b": "dar"}]
-    df = DataFrame(dicts_non_numeric)
+    df = DataFrame(dicts_non_numeric, dtype=object)
     dfgb = df.groupby("a", as_index=False, sort=False)
 
     if numeric_only:
@@ -3142,10 +3166,14 @@ def test_grouping_with_categorical_interval_columns():
 def test_groupby_sum_on_nan_should_return_nan(bug_var):
     # GH 24196
     df = DataFrame({"A": [bug_var, bug_var, bug_var, np.nan]})
+    if isinstance(bug_var, str):
+        df = df.astype(object)
     dfgb = df.groupby(lambda x: x)
     result = dfgb.sum(min_count=1)
 
-    expected_df = DataFrame([bug_var, bug_var, bug_var, None], columns=["A"])
+    expected_df = DataFrame(
+        [bug_var, bug_var, bug_var, None], columns=["A"], dtype=df["A"].dtype
+    )
     tm.assert_frame_equal(result, expected_df)
 
 

pandas/tests/groupby/test_groupby_subclass.py

@@ -109,7 +109,7 @@ def test_groupby_resample_preserves_subclass(obj):
 
     df = obj(
         {
-            "Buyer": "Carl Carl Carl Carl Joe Carl".split(),
+            "Buyer": Series("Carl Carl Carl Carl Joe Carl".split(), dtype=object),
             "Quantity": [18, 3, 5, 1, 9, 3],
             "Date": [
                 datetime(2013, 9, 1, 13, 0),

pandas/tests/groupby/test_numeric_only.py

@@ -29,7 +29,8 @@ def df(self):
                 "group": [1, 1, 2],
                 "int": [1, 2, 3],
                 "float": [4.0, 5.0, 6.0],
-                "string": list("abc"),
+                "string": Series(["a", "b", "c"], dtype="str"),
+                "object": Series(["a", "b", "c"], dtype=object),
                 "category_string": Series(list("abc")).astype("category"),
                 "category_int": [7, 8, 9],
                 "datetime": date_range("20130101", periods=3),
@@ -41,6 +42,7 @@ def df(self):
                 "int",
                 "float",
                 "string",
+                "object",
                 "category_string",
                 "category_int",
                 "datetime",
@@ -113,6 +115,7 @@ def test_first_last(self, df, method):
                 "int",
                 "float",
                 "string",
+                "object",
                 "category_string",
                 "category_int",
                 "datetime",
@@ -160,7 +163,9 @@ def _check(self, df, method, expected_columns, expected_columns_numeric):
 
         # object dtypes for transformations are not implemented in Cython and
         # have no Python fallback
-        exception = NotImplementedError if method.startswith("cum") else TypeError
+        exception = (
+            (NotImplementedError, TypeError) if method.startswith("cum") else TypeError
+        )
 
         if method in ("min", "max", "cummin", "cummax", "cumsum", "cumprod"):
             # The methods default to numeric_only=False and raise TypeError
@@ -171,6 +176,7 @@ def _check(self, df, method, expected_columns, expected_columns_numeric):
                     re.escape(f"agg function failed [how->{method},dtype->object]"),
                     # cumsum/cummin/cummax/cumprod
                     "function is not implemented for this dtype",
+                    f"dtype 'str' does not support operation '{method}'",
                 ]
             )
             with pytest.raises(exception, match=msg):
@@ -181,7 +187,7 @@ def _check(self, df, method, expected_columns, expected_columns_numeric):
                     "category type does not support sum operations",
                     re.escape(f"agg function failed [how->{method},dtype->object]"),
                     re.escape(f"agg function failed [how->{method},dtype->string]"),
-                    re.escape(f"agg function failed [how->{method},dtype->str]"),
+                    f"dtype 'str' does not support operation '{method}'",
                 ]
             )
             with pytest.raises(exception, match=msg):
@@ -199,7 +205,7 @@ def _check(self, df, method, expected_columns, expected_columns_numeric):
                     f"Cannot perform {method} with non-ordered Categorical",
                     re.escape(f"agg function failed [how->{method},dtype->object]"),
                     re.escape(f"agg function failed [how->{method},dtype->string]"),
-                    re.escape(f"agg function failed [how->{method},dtype->str]"),
+                    f"dtype 'str' does not support operation '{method}'",
                 ]
             )
             with pytest.raises(exception, match=msg):
@@ -384,7 +390,9 @@ def test_numeric_only(kernel, has_arg, numeric_only, keys):
                 re.escape(f"agg function failed [how->{kernel},dtype->object]"),
             ]
         )
-        if kernel == "idxmin":
+        if kernel == "quantile":
+            msg = "dtype 'object' does not support operation 'quantile'"
+        elif kernel == "idxmin":
             msg = "'<' not supported between instances of 'type' and 'type'"
         elif kernel == "idxmax":
             msg = "'>' not supported between instances of 'type' and 'type'"
@@ -458,7 +466,7 @@ def test_deprecate_numeric_only_series(dtype, groupby_func, request):
     # that succeed should not be allowed to fail (without deprecation, at least)
     if groupby_func in fails_on_numeric_object and dtype is object:
         if groupby_func == "quantile":
-            msg = "cannot be performed against 'object' dtypes"
+            msg = "dtype 'object' does not support operation 'quantile'"
         else:
             msg = "is not supported for object dtype"
         warn = FutureWarning if groupby_func == "fillna" else None