Avoid redefining Frame._get_columns_by_label in subclasses

python/cudf/cudf/core/dataframe.py

@@ -1345,7 +1345,16 @@ def __getitem__(self, arg):
         8  8  8  8
         """
         if _is_scalar_or_zero_d_array(arg) or isinstance(arg, tuple):
-            return self._get_columns_by_label(arg, downcast=True)
+            out = self._get_columns_by_label(arg)
+            if is_scalar(arg):
+                nlevels = 1
+            elif isinstance(arg, tuple):
+                nlevels = len(arg)
+            if self._data.multiindex is False or nlevels == self._data.nlevels:
+                out = self._constructor_sliced._from_data(out._data)
+                out.index = self.index
+                out.name = arg
+            return out
 
         elif isinstance(arg, slice):
             return self._slice(arg)
@@ -1990,31 +1999,6 @@ def _repr_html_(self):
     def _repr_latex_(self):
         return self._get_renderable_dataframe().to_pandas()._repr_latex_()
 
-    @_cudf_nvtx_annotate
-    def _get_columns_by_label(
-        self, labels, *, downcast=False
-    ) -> Self | Series:
-        """
-        Return columns of dataframe by `labels`
-
-        If downcast is True, try and downcast from a DataFrame to a Series
-        """
-        ca = self._data.select_by_label(labels)
-        if downcast:
-            if is_scalar(labels):
-                nlevels = 1
-            elif isinstance(labels, tuple):
-                nlevels = len(labels)
-            if self._data.multiindex is False or nlevels == self._data.nlevels:
-                out = self._constructor_sliced._from_data(
-                    ca, index=self.index, name=labels
-                )
-                return out
-        out = self.__class__._from_data(
-            ca, index=self.index, columns=ca.to_pandas_index()
-        )
-        return out
-
     def _make_operands_and_index_for_binop(
         self,
         other: Any,

python/cudf/cudf/core/frame.py

@@ -132,12 +132,19 @@ def deserialize(cls, header, frames):
     @classmethod
     @_cudf_nvtx_annotate
     def _from_data(cls, data: MutableMapping) -> Self:
+        """
+        Construct cls from a ColumnAccessor-like mapping.
+        """
         obj = cls.__new__(cls)
         Frame.__init__(obj, data)
         return obj
 
     @_cudf_nvtx_annotate
     def _from_data_like_self(self, data: MutableMapping) -> Self:
+        """
+        Return type(self) from a ColumnAccessor-like mapping but
+        with the external properties, e.g. .index, .name, of self.
+        """
         return self._from_data(data)
 
     @_cudf_nvtx_annotate
@@ -351,12 +358,13 @@ def equals(self, other) -> bool:
         )
 
     @_cudf_nvtx_annotate
-    def _get_columns_by_label(self, labels, *, downcast=False) -> Self:
+    def _get_columns_by_label(self, labels) -> Self:
         """
-        Returns columns of the Frame specified by `labels`
+        Returns columns of the Frame specified by `labels`.
 
+        Akin to cudf.DataFrame(...).loc[:, labels]
         """
-        return self.__class__._from_data(self._data.select_by_label(labels))
+        return self._from_data_like_self(self._data.select_by_label(labels))
 
     @property
     @_cudf_nvtx_annotate
@@ -1434,22 +1442,18 @@ def _get_sorted_inds(
         Get the indices required to sort self according to the columns
         specified in by.
         """
-
-        to_sort = [
-            *(
-                self
-                if by is None
-                else self._get_columns_by_label(list(by), downcast=False)
-            )._columns
-        ]
+        if by is None:
+            to_sort = self._columns
+        else:
+            to_sort = self._get_columns_by_label(list(by))._columns
 
         if is_scalar(ascending):
             ascending_lst = [ascending] * len(to_sort)
         else:
             ascending_lst = list(ascending)
 
         return libcudf.sort.order_by(
-            to_sort,
+            list(to_sort),
             ascending_lst,
             na_position,
             stable=True,

python/cudf/cudf/core/indexed_frame.py

@@ -306,8 +306,8 @@ def _from_data(
 
     @_cudf_nvtx_annotate
     def _from_data_like_self(self, data: MutableMapping):
-        out = self._from_data(data, self.index)
-        out._data._level_names = self._data._level_names
+        out = super()._from_data_like_self(data)
+        out.index = self.index
         return out
 
     @_cudf_nvtx_annotate

python/cudf/cudf/core/series.py

@@ -682,6 +682,12 @@ def _from_data(
             out.name = name
         return out
 
+    @_cudf_nvtx_annotate
+    def _from_data_like_self(self, data: MutableMapping):
+        out = super()._from_data_like_self(data)
+        out.name = self.name
+        return out
+
     @_cudf_nvtx_annotate
     def __contains__(self, item):
         return item in self.index
@@ -856,20 +862,6 @@ def deserialize(cls, header, frames):
 
         return obj
 
-    def _get_columns_by_label(self, labels, *, downcast=False) -> Self:
-        """Return the column specified by `labels`
-
-        For cudf.Series, either the column, or an empty series is returned.
-        Parameter `downcast` does not have effects.
-        """
-        ca = self._data.select_by_label(labels)
-
-        return (
-            self.__class__._from_data(data=ca, index=self.index)
-            if len(ca) > 0
-            else self.__class__(dtype=self.dtype, name=self.name)
-        )
-
     @_cudf_nvtx_annotate
     def drop(
         self,