BUG: Fix ListAccessor methods to preserve original name (#60527)

* fix: preserve series name in ListAccessor

* formatting

* add whatsnew v3.0.0 entry

Author: FBruzzesi

doc/source/whatsnew/v3.0.0.rst

@@ -798,6 +798,7 @@ Other
 - Bug in :meth:`read_csv` where chained fsspec TAR file and ``compression="infer"`` fails with ``tarfile.ReadError`` (:issue:`60028`)
 - Bug in Dataframe Interchange Protocol implementation was returning incorrect results for data buffers' associated dtype, for string and datetime columns (:issue:`54781`)
 - Bug in ``Series.list`` methods not preserving the original :class:`Index`. (:issue:`58425`)
+- Bug in ``Series.list`` methods not preserving the original name. (:issue:`60522`)
 - Bug in printing a :class:`DataFrame` with a :class:`DataFrame` stored in :attr:`DataFrame.attrs` raised a ``ValueError`` (:issue:`60455`)
 
 .. ***DO NOT USE THIS SECTION***

pandas/core/arrays/arrow/accessors.py

@@ -117,7 +117,10 @@ def len(self) -> Series:
 
         value_lengths = pc.list_value_length(self._pa_array)
         return Series(
-            value_lengths, dtype=ArrowDtype(value_lengths.type), index=self._data.index
+            value_lengths,
+            dtype=ArrowDtype(value_lengths.type),
+            index=self._data.index,
+            name=self._data.name,
         )
 
     def __getitem__(self, key: int | slice) -> Series:
@@ -162,7 +165,10 @@ def __getitem__(self, key: int | slice) -> Series:
             #     key = pc.add(key, pc.list_value_length(self._pa_array))
             element = pc.list_element(self._pa_array, key)
             return Series(
-                element, dtype=ArrowDtype(element.type), index=self._data.index
+                element,
+                dtype=ArrowDtype(element.type),
+                index=self._data.index,
+                name=self._data.name,
             )
         elif isinstance(key, slice):
             if pa_version_under11p0:
@@ -181,7 +187,12 @@ def __getitem__(self, key: int | slice) -> Series:
             if step is None:
                 step = 1
             sliced = pc.list_slice(self._pa_array, start, stop, step)
-            return Series(sliced, dtype=ArrowDtype(sliced.type), index=self._data.index)
+            return Series(
+                sliced,
+                dtype=ArrowDtype(sliced.type),
+                index=self._data.index,
+                name=self._data.name,
+            )
         else:
             raise ValueError(f"key must be an int or slice, got {type(key).__name__}")
 
@@ -223,7 +234,12 @@ def flatten(self) -> Series:
         counts = pa.compute.list_value_length(self._pa_array)
         flattened = pa.compute.list_flatten(self._pa_array)
         index = self._data.index.repeat(counts.fill_null(pa.scalar(0, counts.type)))
-        return Series(flattened, dtype=ArrowDtype(flattened.type), index=index)
+        return Series(
+            flattened,
+            dtype=ArrowDtype(flattened.type),
+            index=index,
+            name=self._data.name,
+        )
 
 
 class StructAccessor(ArrowAccessor):

pandas/tests/series/accessors/test_list_accessor.py

@@ -25,9 +25,10 @@ def test_list_getitem(list_dtype):
     ser = Series(
         [[1, 2, 3], [4, None, 5], None],
         dtype=ArrowDtype(list_dtype),
+        name="a",
     )
     actual = ser.list[1]
-    expected = Series([2, None, None], dtype="int64[pyarrow]")
+    expected = Series([2, None, None], dtype="int64[pyarrow]", name="a")
     tm.assert_series_equal(actual, expected)
 
 
@@ -37,9 +38,15 @@ def test_list_getitem_index():
         [[1, 2, 3], [4, None, 5], None],
         dtype=ArrowDtype(pa.list_(pa.int64())),
         index=[1, 3, 7],
+        name="a",
     )
     actual = ser.list[1]
-    expected = Series([2, None, None], dtype="int64[pyarrow]", index=[1, 3, 7])
+    expected = Series(
+        [2, None, None],
+        dtype="int64[pyarrow]",
+        index=[1, 3, 7],
+        name="a",
+    )
     tm.assert_series_equal(actual, expected)
 
 
@@ -48,6 +55,7 @@ def test_list_getitem_slice():
         [[1, 2, 3], [4, None, 5], None],
         dtype=ArrowDtype(pa.list_(pa.int64())),
         index=[1, 3, 7],
+        name="a",
     )
     if pa_version_under11p0:
         with pytest.raises(
@@ -60,6 +68,7 @@ def test_list_getitem_slice():
             [[2, 3], [None, 5], None],
             dtype=ArrowDtype(pa.list_(pa.int64())),
             index=[1, 3, 7],
+            name="a",
         )
         tm.assert_series_equal(actual, expected)
 
@@ -68,22 +77,25 @@ def test_list_len():
     ser = Series(
         [[1, 2, 3], [4, None], None],
         dtype=ArrowDtype(pa.list_(pa.int64())),
+        name="a",
     )
     actual = ser.list.len()
-    expected = Series([3, 2, None], dtype=ArrowDtype(pa.int32()))
+    expected = Series([3, 2, None], dtype=ArrowDtype(pa.int32()), name="a")
     tm.assert_series_equal(actual, expected)
 
 
 def test_list_flatten():
     ser = Series(
         [[1, 2, 3], None, [4, None], [], [7, 8]],
         dtype=ArrowDtype(pa.list_(pa.int64())),
+        name="a",
     )
     actual = ser.list.flatten()
     expected = Series(
         [1, 2, 3, 4, None, 7, 8],
         dtype=ArrowDtype(pa.int64()),
         index=[0, 0, 0, 2, 2, 4, 4],
+        name="a",
     )
     tm.assert_series_equal(actual, expected)