fix(python): selectors by_name and by_dtype should allow empty list a…

…s input (pola-rs#11024)

Co-authored-by: Antonio Caballero <antonio.caballero@concirrus.com>

py-polars/polars/selectors.py

@@ -592,7 +592,7 @@ def by_dtype(
             raise TypeError(msg)
 
     return _selector_proxy_(
-        F.col(*all_dtypes), name="by_dtype", parameters={"dtypes": all_dtypes}
+        F.col(all_dtypes), name="by_dtype", parameters={"dtypes": all_dtypes}
     )
 
 
@@ -661,7 +661,7 @@ def by_name(*names: str | Collection[str]) -> SelectorType:
             TypeError(f"Invalid name: {nm!r}")
 
     return _selector_proxy_(
-        F.col(*all_names), name="by_name", parameters={"*names": all_names}
+        F.col(all_names), name="by_name", parameters={"*names": all_names}
     )
 
 

py-polars/tests/unit/test_selectors.py

@@ -57,6 +57,8 @@ def test_selector_by_dtype(df: pl.DataFrame) -> None:
         "fgg": pl.Boolean,
         "qqR": pl.String,
     }
+    assert df.select(cs.by_dtype()).schema == {}
+    assert df.select(cs.by_dtype([])).schema == {}
 
 
 def test_selector_by_name(df: pl.DataFrame) -> None:
@@ -75,6 +77,8 @@ def test_selector_by_name(df: pl.DataFrame) -> None:
         "JJK",
         "qqR",
     ]
+    assert df.select(cs.by_name()).columns == []
+    assert df.select(cs.by_name([])).columns == []
 
 
 def test_selector_contains(df: pl.DataFrame) -> None: