BUG: DataFrame index name no longer resets after appending a list of series (#44123)

Author: robbertjan94

doc/source/whatsnew/v1.4.0.rst

@@ -617,6 +617,7 @@ Reshaping
 - Bug in :func:`concat` which ignored the ``sort`` parameter (:issue:`43375`)
 - Fixed bug in :func:`merge` with :class:`MultiIndex` as column index for the ``on`` argument returning an error when assigning a column internally (:issue:`43734`)
 - Bug in :func:`crosstab` would fail when inputs are lists or tuples (:issue:`44076`)
+- Bug in :meth:`DataFrame.append` failing to retain ``index.name`` when appending a list of :class:`Series` objects (:issue:`44109`)
 - Fixed metadata propagation in :meth:`Dataframe.apply` method, consequently fixing the same issue for :meth:`Dataframe.transform`, :meth:`Dataframe.nunique` and :meth:`Dataframe.mode` (:issue:`28283`)
 
 Sparse

pandas/core/frame.py

@@ -9086,6 +9086,8 @@ def append(
                 pass
             elif not isinstance(other[0], DataFrame):
                 other = DataFrame(other)
+                if self.index.name is not None and not ignore_index:
+                    other.index.name = self.index.name
 
         from pandas.core.reshape.concat import concat
 

pandas/tests/frame/methods/test_append.py

@@ -96,6 +96,26 @@ def test_append_list_of_series_dicts(self):
         expected = df.append(DataFrame(dicts), ignore_index=True, sort=True)
         tm.assert_frame_equal(result, expected)
 
+    def test_append_list_retain_index_name(self):
+        df = DataFrame(
+            [[1, 2], [3, 4]], index=pd.Index(["a", "b"], name="keepthisname")
+        )
+
+        serc = Series([5, 6], name="c")
+
+        expected = DataFrame(
+            [[1, 2], [3, 4], [5, 6]],
+            index=pd.Index(["a", "b", "c"], name="keepthisname"),
+        )
+
+        # append series
+        result = df.append(serc)
+        tm.assert_frame_equal(result, expected)
+
+        # append list of series
+        result = df.append([serc])
+        tm.assert_frame_equal(result, expected)
+
     def test_append_missing_cols(self):
         # GH22252
         # exercise the conditional branch in append method where the data