old pandas compat

narwhals/_dask/dataframe.py

@@ -118,7 +118,12 @@ def select(
         if exprs and all(isinstance(x, str) for x in exprs) and not named_exprs:
             # This is a simple slice => fastpath!
             return self._from_native_frame(
-                select_columns_by_name(self._native_frame, list(exprs))  # type: ignore[arg-type]
+                select_columns_by_name(
+                    self._native_frame,
+                    list(exprs),  # type: ignore[arg-type]
+                    self._backend_version,
+                    self._implementation,
+                )
             )
 
         new_series = parse_exprs_and_named_exprs(self, *exprs, **named_exprs)
@@ -140,7 +145,10 @@ def select(
             return self._from_native_frame(df)
 
         df = select_columns_by_name(
-            self._native_frame.assign(**new_series), list(new_series.keys())
+            self._native_frame.assign(**new_series),
+            list(new_series.keys()),
+            self._backend_version,
+            self._implementation,
         )
         return self._from_native_frame(df)
 
@@ -265,7 +273,12 @@ def join(
                 msg = "`right_on` cannot be `None` in anti-join"
                 raise TypeError(msg)
             other_native = (
-                select_columns_by_name(other._native_frame, right_on)
+                select_columns_by_name(
+                    other._native_frame,
+                    right_on,
+                    self._backend_version,
+                    self._implementation,
+                )
                 .rename(  # rename to avoid creating extra columns in join
                     columns=dict(zip(right_on, left_on))  # type: ignore[arg-type]
                 )
@@ -287,7 +300,12 @@ def join(
                 msg = "`right_on` cannot be `None` in semi-join"
                 raise TypeError(msg)
             other_native = (
-                select_columns_by_name(other._native_frame, right_on)
+                select_columns_by_name(
+                    other._native_frame,
+                    right_on,
+                    self._backend_version,
+                    self._implementation,
+                )
                 .rename(  # rename to avoid creating extra columns in join
                     columns=dict(zip(right_on, left_on))  # type: ignore[arg-type]
                 )

narwhals/_pandas_like/dataframe.py

@@ -234,7 +234,12 @@ def __getitem__(
         elif is_sequence_but_not_str(item) or (is_numpy_array(item) and item.ndim == 1):
             if all(isinstance(x, str) for x in item) and len(item) > 0:
                 return self._from_native_frame(
-                    select_columns_by_name(self._native_frame, item)
+                    select_columns_by_name(
+                        self._native_frame,
+                        item,
+                        self._backend_version,
+                        self._implementation,
+                    )
                 )
             return self._from_native_frame(self._native_frame.iloc[item])
 
@@ -333,7 +338,12 @@ def select(
             # This is a simple slice => fastpath!
             column_names = list(exprs)
             return self._from_native_frame(
-                select_columns_by_name(self._native_frame, column_names)  # type: ignore[arg-type]
+                select_columns_by_name(
+                    self._native_frame,
+                    column_names,  # type: ignore[arg-type]
+                    self._backend_version,
+                    self._implementation,
+                )
             )
         new_series = evaluate_into_exprs(self, *exprs, **named_exprs)
         if not new_series:
@@ -556,7 +566,12 @@ def join(
                     raise TypeError(msg)
 
                 other_native = (
-                    select_columns_by_name(other._native_frame, right_on)
+                    select_columns_by_name(
+                        other._native_frame,
+                        right_on,
+                        self._backend_version,
+                        self._implementation,
+                    )
                     .rename(  # rename to avoid creating extra columns in join
                         columns=dict(zip(right_on, left_on)),  # type: ignore[arg-type]
                         copy=False,
@@ -580,7 +595,12 @@ def join(
                 msg = "`right_on` cannot be `None` in semi-join"
                 raise TypeError(msg)
             other_native = (
-                select_columns_by_name(other._native_frame, right_on)
+                select_columns_by_name(
+                    other._native_frame,
+                    right_on,
+                    self._backend_version,
+                    self._implementation,
+                )
                 .rename(  # rename to avoid creating extra columns in join
                     columns=dict(zip(right_on, left_on)),  # type: ignore[arg-type]
                     copy=False,

narwhals/_pandas_like/group_by.py

@@ -39,7 +39,12 @@ def __init__(
         ):  # pragma: no cover
             if (
                 not drop_null_keys
-                and select_columns_by_name(self._df._native_frame, self._keys)
+                and select_columns_by_name(
+                    self._df._native_frame,
+                    self._keys,
+                    self._df._backend_version,
+                    self._df._implementation,
+                )
                 .isna()
                 .any()
                 .any()
@@ -231,7 +236,11 @@ def agg_pandas(  # noqa: PLR0915
             result_aggs = native_namespace.DataFrame(
                 list(grouped.groups.keys()), columns=keys
             )
-        return from_dataframe(select_columns_by_name(result_aggs, output_names))
+        return from_dataframe(
+            select_columns_by_name(
+                result_aggs, output_names, backend_version, implementation
+            )
+        )
 
     if dataframe_is_empty:
         # Don't even attempt this, it's way too inconsistent across pandas versions.
@@ -279,4 +288,8 @@ def func(df: Any) -> Any:
     # This may need updating, depending on https://github.com/pandas-dev/pandas/pull/51466/files
     result_complex.reset_index(inplace=True)  # noqa: PD002
 
-    return from_dataframe(select_columns_by_name(result_complex, output_names))
+    return from_dataframe(
+        select_columns_by_name(
+            result_complex, output_names, backend_version, implementation
+        )
+    )

narwhals/_pandas_like/utils.py

@@ -638,10 +638,17 @@ def calculate_timestamp_date(s: pd.Series, time_unit: str) -> pd.Series:
     return result
 
 
-def select_columns_by_name(df: T, column_names: Sequence[str]) -> T:
+def select_columns_by_name(
+    df: T,
+    column_names: Sequence[str],
+    backend_version: tuple[int, ...],
+    implementation: Implementation,
+) -> T:
     """Select columns by name. Prefer this over `df.loc[:, column_names]` as it's
     generally more performant."""
-    if df.columns.dtype.kind == "b":  # type: ignore[attr-defined]
+    if (df.columns.dtype.kind == "b") or (  # type: ignore[attr-defined]
+        implementation is Implementation.PANDAS and backend_version < (1, 5)
+    ):
         # See https://github.com/narwhals-dev/narwhals/issues/1349#issuecomment-2470118122
         # for why we need this
         return df.loc[:, column_names]  # type: ignore[no-any-return, attr-defined]