BUG: Fix #61222: Keep index name when resampling with pyarrow dtype

Author: mthiboust

doc/source/whatsnew/v2.3.0.rst

@@ -169,7 +169,7 @@ Groupby/resample/rolling
 
 Reshaping
 ^^^^^^^^^
--
+- :meth:`DataFrame.resample` was not keeping the index name when the index had :class:`pyarrow` datetime dtype (:issue:`61222`)
 -
 
 Sparse

pandas/core/resample.py

@@ -517,7 +517,9 @@ def _wrap_result(self, result):
             result.name = getattr(obj, "name", None)
 
         if self._timegrouper._arrow_dtype is not None:
+            obj = self.obj
             result.index = result.index.astype(self._timegrouper._arrow_dtype)
+            result.index.name = getattr(obj.index, "name", None)
 
         return result
 

pandas/tests/resample/test_datetime_index.py

@@ -2155,6 +2155,16 @@ def test_arrow_timestamp_resample(tz):
     tm.assert_series_equal(result, expected)
 
 
+@td.skip_if_no("pyarrow")
+def test_arrow_timestamp_resample_keep_index_name():
+    # https://github.com/pandas-dev/pandas/issues/61222
+    idx = Series(date_range("2020-01-01", periods=5), dtype="timestamp[ns][pyarrow]")
+    expected = Series(np.arange(5, dtype=np.float64), index=idx)
+    expected.index.name = "index_name"
+    result = expected.resample("1D").mean()
+    assert result.index.name == expected.index.name
+
+
 @pytest.mark.parametrize("freq", ["1A", "2A-MAR"])
 def test_resample_A_raises(freq):
     msg = f"Invalid frequency: {freq[1:]}"