diff --git a/pandas/tests/groupby/test_grouping.py b/pandas/tests/groupby/test_grouping.py index 77e71a5d2e4d0..7372ab272ba04 100644 --- a/pandas/tests/groupby/test_grouping.py +++ b/pandas/tests/groupby/test_grouping.py @@ -875,6 +875,22 @@ def test_groupby_tuple_keys_handle_multiindex(self): expected = expected[result.columns] tm.assert_frame_equal(result.reset_index(drop=True), expected) + def test_groupby_grouper_immutable_list_item(self): + # GH 26564 - prevent 'ValueError: all keys need to be the same shape' + # when reusing a list of groupers + df1 = DataFrame([["05/29/2019"], ["05/28/2019"]], columns=["date"]).assign( + date=lambda df: pd.to_datetime(df["date"]) + ) + df2 = DataFrame(columns=["date"]).assign( + date=lambda df: pd.to_datetime(df["date"]) + ) + + groupers = [Grouper(key="date", freq="1D")] + + df1.groupby(groupers).head() + # no error + df2.groupby(groupers).head() + # get_group # --------------------------------