From 05a5a9d7844fd029d2e05e55419333488ea0ab8c Mon Sep 17 00:00:00 2001 From: Matthew Roeschke Date: Tue, 8 Sep 2020 02:51:20 -0700 Subject: [PATCH] BUG: GroupbyRolling with an empty frame (#36208) Co-authored-by: Matt Roeschke --- doc/source/whatsnew/v1.1.2.rst | 2 +- pandas/core/window/rolling.py | 10 ++++++---- pandas/tests/window/test_grouper.py | 12 ++++++++++++ 3 files changed, 19 insertions(+), 5 deletions(-) diff --git a/doc/source/whatsnew/v1.1.2.rst b/doc/source/whatsnew/v1.1.2.rst index 28ce49c11b3f0..f13d38d1f8f76 100644 --- a/doc/source/whatsnew/v1.1.2.rst +++ b/doc/source/whatsnew/v1.1.2.rst @@ -24,7 +24,7 @@ Fixed regressions - Fix regression in pickle roundtrip of the ``closed`` attribute of :class:`IntervalIndex` (:issue:`35658`) - Fixed regression in :meth:`DataFrameGroupBy.agg` where a ``ValueError: buffer source array is read-only`` would be raised when the underlying array is read-only (:issue:`36014`) - Fixed regression in :meth:`Series.groupby.rolling` number of levels of :class:`MultiIndex` in input was compressed to one (:issue:`36018`) -- +- Fixed regression in :class:`DataFrameGroupBy` on an empty :class:`DataFrame` (:issue:`36197`) .. --------------------------------------------------------------------------- diff --git a/pandas/core/window/rolling.py b/pandas/core/window/rolling.py index 235bd5364af02..9466ada3f4578 100644 --- a/pandas/core/window/rolling.py +++ b/pandas/core/window/rolling.py @@ -2240,10 +2240,12 @@ def _create_blocks(self, obj: FrameOrSeriesUnion): """ # Ensure the object we're rolling over is monotonically sorted relative # to the groups - groupby_order = np.concatenate( - list(self._groupby.grouper.indices.values()) - ).astype(np.int64) - obj = obj.take(groupby_order) + # GH 36197 + if not obj.empty: + groupby_order = np.concatenate( + list(self._groupby.grouper.indices.values()) + ).astype(np.int64) + obj = obj.take(groupby_order) return super()._create_blocks(obj) def _get_cython_func_type(self, func: str) -> Callable: diff --git a/pandas/tests/window/test_grouper.py b/pandas/tests/window/test_grouper.py index cb85ad7584da7..786cf68d28871 100644 --- a/pandas/tests/window/test_grouper.py +++ b/pandas/tests/window/test_grouper.py @@ -393,3 +393,15 @@ def test_groupby_rolling_index_changed(self, func): name="a", ) tm.assert_series_equal(result, expected) + + def test_groupby_rolling_empty_frame(self): + # GH 36197 + expected = pd.DataFrame({"s1": []}) + result = expected.groupby("s1").rolling(window=1).sum() + expected.index = pd.MultiIndex.from_tuples([], names=["s1", None]) + tm.assert_frame_equal(result, expected) + + expected = pd.DataFrame({"s1": [], "s2": []}) + result = expected.groupby(["s1", "s2"]).rolling(window=1).sum() + expected.index = pd.MultiIndex.from_tuples([], names=["s1", "s2", None]) + tm.assert_frame_equal(result, expected)