Support additional dtypes in resample

doc/whats-new.rst

@@ -60,6 +60,10 @@ Bug fixes
 - Fix deprecation warning that was raised when calling ``np.array`` on an ``xr.DataArray``
   in NumPy 2.0 (:issue:`9312`, :pull:`9393`)
   By `Andrew Scherer <https://github.com/andrew-s28>`_.
+- Fix support for using ``pandas.BaseOffset``, ``pandas.Timedelta``, and
+  ``datetime.timedelta`` objects as ``resample`` frequencies
+  (:issue:`9408`, :pull:`9413`).
+  By `Oliver Higgs <https://github.com/oliverhiggs>`_.
 
 Documentation
 ~~~~~~~~~~~~~

xarray/core/common.py

@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+import datetime
 import warnings
 from collections.abc import Callable, Hashable, Iterable, Iterator, Mapping
 from contextlib import suppress
@@ -32,8 +33,6 @@
 
 
 if TYPE_CHECKING:
-    import datetime
-
     from numpy.typing import DTypeLike
 
     from xarray.core.dataarray import DataArray
@@ -1078,14 +1077,18 @@ def _resample(
         )
 
         grouper: Resampler
-        if isinstance(freq, str):
+        if isinstance(freq, str | datetime.timedelta | pd.Timedelta | pd.DateOffset):
             grouper = TimeResampler(
                 freq=freq, closed=closed, label=label, origin=origin, offset=offset
             )
         elif isinstance(freq, Resampler):
             grouper = freq
         else:
-            raise ValueError("freq must be a str or a Resampler object")
+            raise ValueError(
+                "freq must be an object of type 'str', 'datetime.timedelta', "
+                "'pandas.Timedelta', 'pandas.DateOffset', or 'TimeResampler'. "
+                f"Received {type(freq)} instead."
+            )
 
         rgrouper = ResolvedGrouper(grouper, group, self)
 

xarray/groupers.py

@@ -14,7 +14,7 @@
 import numpy as np
 import pandas as pd
 
-from xarray.coding.cftime_offsets import _new_to_legacy_freq
+from xarray.coding.cftime_offsets import BaseCFTimeOffset, _new_to_legacy_freq
 from xarray.core import duck_array_ops
 from xarray.core.coordinates import Coordinates
 from xarray.core.dataarray import DataArray
@@ -336,7 +336,7 @@ class TimeResampler(Resampler):
 
     Attributes
     ----------
-    freq : str
+    freq : str, datetime.timedelta, pandas.Timestamp, pandas.DateOffset
         Frequency to resample to. See `Pandas frequency
         aliases <https://pandas.pydata.org/pandas-docs/stable/user_guide/timeseries.html#offset-aliases>`_
         for a list of possible values.
@@ -358,7 +358,7 @@ class TimeResampler(Resampler):
         An offset timedelta added to the origin.
     """
 
-    freq: str
+    freq: str | datetime.timedelta | pd.Timedelta | pd.DateOffset
     closed: SideOptions | None = field(default=None)
     label: SideOptions | None = field(default=None)
     origin: str | DatetimeLike = field(default="start_day")
@@ -380,6 +380,13 @@ def _init_properties(self, group: T_Group) -> None:
         if isinstance(group_as_index, CFTimeIndex):
             from xarray.core.resample_cftime import CFTimeGrouper
 
+            if not isinstance(self.freq, str | BaseCFTimeOffset):
+                raise ValueError(
+                    "Resample frequency must be a string or 'BaseCFTimeOffset' "
+                    "object when resampling a 'CFTimeIndex'. Received "
+                    f"{type(self.freq)} instead."
+                )
+
             self.index_grouper = CFTimeGrouper(
                 freq=self.freq,
                 closed=self.closed,
@@ -388,6 +395,12 @@ def _init_properties(self, group: T_Group) -> None:
                 offset=offset,
             )
         else:
+            if isinstance(self.freq, BaseCFTimeOffset):
+                raise ValueError(
+                    "'BaseCFTimeOffset' resample frequencies are only supported "
+                    "when resampling a 'CFTimeIndex'"
+                )
+
             self.index_grouper = pd.Grouper(
                 # TODO remove once requiring pandas >= 2.2
                 freq=_new_to_legacy_freq(self.freq),

xarray/tests/test_groupby.py

@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+import datetime
 import operator
 import warnings
 from unittest import mock
@@ -1813,6 +1814,31 @@ def resample_as_pandas(array, *args, **kwargs):
         with pytest.raises(ValueError):
             reverse.resample(time="1D").mean()
 
+    @pytest.mark.parametrize("use_cftime", [True, False])
+    def test_resample_dtype(self, use_cftime: bool) -> None:
+        if use_cftime and not has_cftime:
+            pytest.skip()
+        array = DataArray(
+            np.arange(10),
+            [
+                (
+                    "time",
+                    xr.date_range(
+                        "2000-01-01", freq="6h", periods=10, use_cftime=use_cftime
+                    ),
+                )
+            ],
+        )
+        test_resample_freqs = ["10min"]
+        if not use_cftime:
+            test_resample_freqs += [
+                pd.Timedelta(hours=2),
+                pd.offsets.MonthBegin(),
+                datetime.timedelta(days=1, hours=6),
+            ]
+        for freq in test_resample_freqs:
+            array.resample(time=freq)
+
     @pytest.mark.parametrize("use_cftime", [True, False])
     def test_resample_doctest(self, use_cftime: bool) -> None:
         # run the doctest example here so we are not surprised