Grouper, Resampler as public api

xarray/core/common.py

@@ -983,7 +983,7 @@ def _resample(
         # TODO support non-string indexer after removing the old API.
 
         from xarray.core.dataarray import DataArray
-        from xarray.core.groupby import ResolvedGrouper, TimeResampler
+        from xarray.core.groupby import Resampler, ResolvedGrouper, TimeResampler
         from xarray.core.resample import RESAMPLE_DIM
 
         # note: the second argument (now 'skipna') use to be 'dim'
@@ -1013,15 +1013,19 @@ def _resample(
             name=RESAMPLE_DIM,
         )
 
-        grouper = TimeResampler(
-            freq=freq,
-            closed=closed,
-            label=label,
-            origin=origin,
-            offset=offset,
-            loffset=loffset,
-            base=base,
-        )
+        if isinstance(freq, str):
+            grouper = TimeResampler(
+                freq=freq,
+                closed=closed,
+                label=label,
+                origin=origin,
+                offset=offset,
+                loffset=loffset,
+                base=base,
+            )
+        else:
+            assert isinstance(freq, Resampler)
+            grouper = freq
 
         rgrouper = ResolvedGrouper(grouper, group, self)
 

xarray/core/dataarray.py

@@ -6612,9 +6612,10 @@ def interp_calendar(
 
     def groupby(
         self,
-        group: Hashable | DataArray | IndexVariable,
+        group: Hashable | DataArray | IndexVariable = None,
         squeeze: bool | None = None,
         restore_coord_dims: bool = False,
+        **groupers,
     ) -> DataArrayGroupBy:
         """Returns a DataArrayGroupBy object for performing grouped operations.
 
@@ -6686,7 +6687,19 @@ def groupby(
         )
 
         _validate_groupby_squeeze(squeeze)
-        rgrouper = ResolvedGrouper(UniqueGrouper(), group, self)
+
+        if group is not None:
+            assert not groupers
+            grouper = UniqueGrouper()
+        else:
+            if len(groupers) > 1:
+                raise ValueError("grouping by multiple variables is not supported yet.")
+            if not groupers:
+                raise ValueError
+            group, grouper = next(iter(groupers.items()))
+
+        rgrouper = ResolvedGrouper(grouper, group, self)
+
         return DataArrayGroupBy(
             self,
             (rgrouper,),

xarray/core/dataset.py

@@ -10041,9 +10041,10 @@ def interp_calendar(
 
     def groupby(
         self,
-        group: Hashable | DataArray | IndexVariable,
+        group: Hashable | DataArray | IndexVariable | None = None,
         squeeze: bool = True,
         restore_coord_dims: bool = False,
+        **groupers,
     ) -> DatasetGroupBy:
         """Returns a DatasetGroupBy object for performing grouped operations.
 
@@ -10093,7 +10094,16 @@ def groupby(
         )
 
         _validate_groupby_squeeze(squeeze)
-        rgrouper = ResolvedGrouper(UniqueGrouper(), group, self)
+        if group is not None:
+            assert not groupers
+            rgrouper = ResolvedGrouper(UniqueGrouper(), group, self)
+        else:
+            if len(groupers) > 1:
+                raise ValueError("grouping by multiple variables is not supported yet.")
+            if not groupers:
+                raise ValueError
+            for group, grouper in groupers.items():
+                rgrouper = ResolvedGrouper(grouper, group, self)
 
         return DatasetGroupBy(
             self,

xarray/core/groupby.py

@@ -252,7 +252,7 @@ def attrs(self) -> dict:
 
     def __getitem__(self, key):
         if isinstance(key, tuple):
-            key = key[0]
+            (key,) = key
         return self.values[key]
 
     def to_index(self) -> pd.Index:

xarray/tests/test_groupby.py

@@ -10,7 +10,11 @@
 
 import xarray as xr
 from xarray import DataArray, Dataset, Variable
-from xarray.core.groupby import _consolidate_slices
+from xarray.core.groupby import (
+    BinGrouper,
+    UniqueGrouper,
+    _consolidate_slices,
+)
 from xarray.tests import (
     InaccessibleArray,
     assert_allclose,
@@ -83,8 +87,9 @@ def test_multi_index_groupby_map(dataset) -> None:
     assert_equal(expected, actual)
 
 
-def test_reduce_numeric_only(dataset) -> None:
-    gb = dataset.groupby("x", squeeze=False)
+@pytest.mark.parametrize("grouper", [dict(group="x"), dict(x=UniqueGrouper())])
+def test_reduce_numeric_only(dataset, grouper) -> None:
+    gb = dataset.groupby(**grouper, squeeze=False)
     with xr.set_options(use_flox=False):
         expected = gb.sum()
     with xr.set_options(use_flox=True):
@@ -753,11 +758,12 @@ def test_groupby_dataset_reduce() -> None:
 
     expected = data.mean("y")
     expected["yonly"] = expected["yonly"].variable.set_dims({"x": 3})
-    actual = data.groupby("x").mean(...)
-    assert_allclose(expected, actual)
+    for gb in [data.groupby("x"), data.groupby(x=UniqueGrouper())]:
+        actual = gb.mean(...)
+        assert_allclose(expected, actual)
 
-    actual = data.groupby("x").mean("y")
-    assert_allclose(expected, actual)
+        actual = gb.mean("y")
+        assert_allclose(expected, actual)
 
     letters = data["letters"]
     expected = Dataset(
@@ -767,8 +773,9 @@ def test_groupby_dataset_reduce() -> None:
             "yonly": data["yonly"].groupby(letters).mean(),
         }
     )
-    actual = data.groupby("letters").mean(...)
-    assert_allclose(expected, actual)
+    for gb in [data.groupby("letters"), data.groupby(letters=UniqueGrouper())]:
+        actual = gb.mean(...)
+        assert_allclose(expected, actual)
 
 
 @pytest.mark.parametrize("squeeze", [True, False])
@@ -898,6 +905,14 @@ def test_groupby_bins_cut_kwargs(use_flox: bool) -> None:
     )
     assert_identical(expected, actual)
 
+    with xr.set_options(use_flox=use_flox):
+        actual = da.groupby(
+            x=BinGrouper(
+                bins=x_bins, cut_kwargs=dict(include_lowest=True, right=False)
+            ),
+        ).mean()
+    assert_identical(expected, actual)
+
 
 @pytest.mark.parametrize("indexed_coord", [True, False])
 def test_groupby_bins_math(indexed_coord) -> None:
@@ -906,11 +921,17 @@ def test_groupby_bins_math(indexed_coord) -> None:
     if indexed_coord:
         da["x"] = np.arange(N)
         da["y"] = np.arange(N)
-    g = da.groupby_bins("x", np.arange(0, N + 1, 3))
-    mean = g.mean()
-    expected = da.isel(x=slice(1, None)) - mean.isel(x_bins=("x", [0, 0, 0, 1, 1, 1]))
-    actual = g - mean
-    assert_identical(expected, actual)
+
+    for g in [
+        da.groupby_bins("x", np.arange(0, N + 1, 3)),
+        da.groupby(x=BinGrouper(bins=np.arange(0, N + 1, 3))),
+    ]:
+        mean = g.mean()
+        expected = da.isel(x=slice(1, None)) - mean.isel(
+            x_bins=("x", [0, 0, 0, 1, 1, 1])
+        )
+        actual = g - mean
+        assert_identical(expected, actual)
 
 
 def test_groupby_math_nD_group() -> None: