set_columns

narwhals/_pandas_like/group_by.py

@@ -14,6 +14,7 @@
 from narwhals._pandas_like.utils import horizontal_concat
 from narwhals._pandas_like.utils import native_series_from_iterable
 from narwhals._pandas_like.utils import select_columns_by_name
+from narwhals._pandas_like.utils import set_columns
 from narwhals.utils import Implementation
 from narwhals.utils import find_stacklevel
 from narwhals.utils import remove_prefix
@@ -271,18 +272,24 @@ def agg_pandas(  # noqa: PLR0915
         if std_aggs:
             result_aggs.extend(
                 [
-                    grouped[std_root_names]
-                    .std(ddof=ddof)
-                    .set_axis(std_output_names, axis="columns", copy=False)
+                    set_columns(
+                        grouped[std_root_names].std(ddof=ddof),
+                        columns=std_output_names,
+                        implementation=implementation,
+                        backend_version=backend_version,
+                    )
                     for ddof, (std_root_names, std_output_names) in std_aggs.items()
                 ]
             )
         if var_aggs:
             result_aggs.extend(
                 [
-                    grouped[var_root_names]
-                    .var(ddof=ddof)
-                    .set_axis(var_output_names, axis="columns", copy=False)
+                    set_columns(
+                        grouped[var_root_names].var(ddof=ddof),
+                        columns=var_output_names,
+                        implementation=implementation,
+                        backend_version=backend_version,
+                    )
                     for ddof, (var_root_names, var_output_names) in var_aggs.items()
                 ]
             )

narwhals/_pandas_like/series.py

@@ -17,7 +17,7 @@
 from narwhals._pandas_like.utils import native_to_narwhals_dtype
 from narwhals._pandas_like.utils import rename
 from narwhals._pandas_like.utils import select_columns_by_name
-from narwhals._pandas_like.utils import set_axis
+from narwhals._pandas_like.utils import set_index
 from narwhals._pandas_like.utils import to_datetime
 from narwhals.dependencies import is_numpy_scalar
 from narwhals.typing import CompliantSeries
@@ -211,7 +211,7 @@ def scatter(self, indices: int | Sequence[int], values: Any) -> Self:
             # .copy() is necessary in some pre-2.2 versions of pandas to avoid
             # `values` also getting modified (!)
             _, values = broadcast_align_and_extract_native(self, values)
-            values = set_axis(
+            values = set_index(
                 values.copy(),
                 self._native_series.index[indices],
                 implementation=self._implementation,
@@ -1423,7 +1423,7 @@ def len(self: Self) -> PandasLikeSeries:
             self._compliant_series._implementation is Implementation.PANDAS
             and self._compliant_series._backend_version < (3, 0)
         ):  # pragma: no cover
-            native_result = set_axis(
+            native_result = set_index(
                 rename(
                     native_result,
                     native_series.name,

narwhals/_pandas_like/utils.py

@@ -138,7 +138,7 @@ def broadcast_align_and_extract_native(
         if rhs._native_series.index is not lhs_index:
             return (
                 lhs._native_series,
-                set_axis(
+                set_index(
                     rhs._native_series,
                     lhs_index,
                     implementation=rhs._implementation,
@@ -168,7 +168,7 @@ def validate_dataframe_comparand(index: Any, other: Any) -> Any:
             s = other._native_series
             return s.__class__(s.iloc[0], index=index, dtype=s.dtype, name=s.name)
         if other._native_series.index is not index:
-            return set_axis(
+            return set_index(
                 other._native_series,
                 index,
                 implementation=other._implementation,
@@ -302,14 +302,17 @@ def native_series_from_iterable(
         raise TypeError(msg)
 
 
-def set_axis(
+def set_index(
     obj: T,
     index: Any,
     *,
     implementation: Implementation,
     backend_version: tuple[int, ...],
 ) -> T:
-    """Wrapper around pandas' set_axis so that we can set `copy` / `inplace` based on implementation/version."""
+    """Wrapper around pandas' set_axis to set object index.
+
+    We can set `copy` / `inplace` based on implementation/version.
+    """
     if implementation is Implementation.CUDF:  # pragma: no cover
         obj = obj.copy(deep=False)  # type: ignore[attr-defined]
         obj.index = index  # type: ignore[attr-defined]
@@ -329,6 +332,36 @@ def set_axis(
     return obj.set_axis(index, axis=0, **kwargs)  # type: ignore[attr-defined, no-any-return]
 
 
+def set_columns(
+    obj: T,
+    columns: list[str],
+    *,
+    implementation: Implementation,
+    backend_version: tuple[int, ...],
+) -> T:
+    """Wrapper around pandas' set_axis to set object columns.
+
+    We can set `copy` / `inplace` based on implementation/version.
+    """
+    if implementation is Implementation.CUDF:  # pragma: no cover
+        obj = obj.copy(deep=False)  # type: ignore[attr-defined]
+        obj.columns = columns  # type: ignore[attr-defined]
+        return obj
+    if implementation is Implementation.PANDAS and (
+        backend_version < (1,)
+    ):  # pragma: no cover
+        kwargs = {"inplace": False}
+    else:
+        kwargs = {}
+    if implementation is Implementation.PANDAS and (
+        (1, 5) <= backend_version < (3,)
+    ):  # pragma: no cover
+        kwargs["copy"] = False
+    else:  # pragma: no cover
+        pass
+    return obj.set_axis(columns, axis=1, **kwargs)  # type: ignore[attr-defined, no-any-return]
+
+
 def rename(
     obj: T,
     *args: Any,
@@ -654,7 +687,7 @@ def broadcast_series(series: Sequence[PandasLikeSeries]) -> list[Any]:
 
         elif s_native.index is not idx:
             reindexed.append(
-                set_axis(
+                set_index(
                     s_native,
                     idx,
                     implementation=s._implementation,

narwhals/utils.py

@@ -548,13 +548,13 @@ def maybe_set_index(
             df_any._compliant_frame._from_native_frame(native_obj.set_index(keys))
         )
     elif is_pandas_like_series(native_obj):
-        from narwhals._pandas_like.utils import set_axis
+        from narwhals._pandas_like.utils import set_index
 
         if column_names:
             msg = "Cannot set index using column names on a Series"
             raise ValueError(msg)
 
-        native_obj = set_axis(
+        native_obj = set_index(
             native_obj,
             keys,
             implementation=obj._compliant_series._implementation,  # type: ignore[union-attr]