diff --git a/doc/source/whatsnew/v1.1.2.rst b/doc/source/whatsnew/v1.1.2.rst index da261907565a1..c40430256f64b 100644 --- a/doc/source/whatsnew/v1.1.2.rst +++ b/doc/source/whatsnew/v1.1.2.rst @@ -42,6 +42,7 @@ Bug fixes - Bug in :class:`DataFrame` indexing returning an incorrect :class:`Series` in some cases when the series has been altered and a cache not invalidated (:issue:`33675`) - Bug in :meth:`DataFrame.corr` causing subsequent indexing lookups to be incorrect (:issue:`35882`) - Bug in :meth:`import_optional_dependency` returning incorrect package names in cases where package name is different from import name (:issue:`35948`) +- Bug when setting empty :class:`DataFrame` column to a :class:`Series` in preserving name of index in frame (:issue:`31368`) .. --------------------------------------------------------------------------- diff --git a/pandas/core/frame.py b/pandas/core/frame.py index e1a889bf79d95..59cf4c0e2f81d 100644 --- a/pandas/core/frame.py +++ b/pandas/core/frame.py @@ -3206,9 +3206,11 @@ def _ensure_valid_index(self, value): "and a value that cannot be converted to a Series" ) from err - self._mgr = self._mgr.reindex_axis( - value.index.copy(), axis=1, fill_value=np.nan - ) + # GH31368 preserve name of index + index_copy = value.index.copy() + index_copy.name = self.index.name + + self._mgr = self._mgr.reindex_axis(index_copy, axis=1, fill_value=np.nan) def _box_col_values(self, values, loc: int) -> Series: """ diff --git a/pandas/tests/indexing/test_partial.py b/pandas/tests/indexing/test_partial.py index 350f86b4e9fd0..7afbbc2b9ab2b 100644 --- a/pandas/tests/indexing/test_partial.py +++ b/pandas/tests/indexing/test_partial.py @@ -660,3 +660,15 @@ def test_indexing_timeseries_regression(self): expected = Series(rng, index=rng) tm.assert_series_equal(result, expected) + + def test_index_name_empty(self): + # GH 31368 + df = pd.DataFrame({}, index=pd.RangeIndex(0, name="df_index")) + series = pd.Series(1.23, index=pd.RangeIndex(4, name="series_index")) + + df["series"] = series + expected = pd.DataFrame( + {"series": [1.23] * 4}, index=pd.RangeIndex(4, name="df_index") + ) + + tm.assert_frame_equal(df, expected)