diff --git a/pandas/tests/reshape/concat/test_index.py b/pandas/tests/reshape/concat/test_index.py index a4d6a41c7eb50..35cf670398664 100644 --- a/pandas/tests/reshape/concat/test_index.py +++ b/pandas/tests/reshape/concat/test_index.py @@ -257,3 +257,52 @@ def test_concat_multiindex_dfs_with_deepcopy(self): tm.assert_frame_equal(result_copy, expected) result_no_copy = concat(example_dict, names=["testname"]) tm.assert_frame_equal(result_no_copy, expected) + + @pytest.mark.parametrize( + "mi1_list", + [ + [["a"], range(2)], + [["b"], np.arange(2.0, 4.0)], + [["c"], ["A", "B"]], + [["d"], pd.date_range(start="2017", end="2018", periods=2)], + ], + ) + @pytest.mark.parametrize( + "mi2_list", + [ + [["a"], range(2)], + [["b"], np.arange(2.0, 4.0)], + [["c"], ["A", "B"]], + [["d"], pd.date_range(start="2017", end="2018", periods=2)], + ], + ) + def test_concat_with_various_multiindex_dtypes( + self, mi1_list: list, mi2_list: list + ): + # GitHub #23478 + mi1 = MultiIndex.from_product(mi1_list) + mi2 = MultiIndex.from_product(mi2_list) + + df1 = DataFrame(np.zeros((1, len(mi1))), columns=mi1) + df2 = DataFrame(np.zeros((1, len(mi2))), columns=mi2) + + if mi1_list[0] == mi2_list[0]: + expected_mi = MultiIndex( + levels=[mi1_list[0], list(mi1_list[1])], + codes=[[0, 0, 0, 0], [0, 1, 0, 1]], + ) + else: + expected_mi = MultiIndex( + levels=[ + mi1_list[0] + mi2_list[0], + list(mi1_list[1]) + list(mi2_list[1]), + ], + codes=[[0, 0, 1, 1], [0, 1, 2, 3]], + ) + + expected_df = DataFrame(np.zeros((1, len(expected_mi))), columns=expected_mi) + + with tm.assert_produces_warning(None): + result_df = concat((df1, df2), axis=1) + + tm.assert_frame_equal(expected_df, result_df)