chore: remove kwargs from selector function (#2058)

Author: MarcoGorelli

narwhals/_arrow/expr.py

@@ -43,7 +43,7 @@ def __init__(
         alias_output_names: Callable[[Sequence[str]], Sequence[str]] | None,
         backend_version: tuple[int, ...],
         version: Version,
-        kwargs: dict[str, Any],
+        kwargs: dict[str, Any] | None = None,
     ) -> None:
         self._call = call
         self._depth = depth
@@ -53,7 +53,7 @@ def __init__(
         self._alias_output_names = alias_output_names
         self._backend_version = backend_version
         self._version = version
-        self._kwargs = kwargs
+        self._kwargs = kwargs or {}
 
     def __repr__(self: Self) -> str:  # pragma: no cover
         return f"ArrowExpr(depth={self._depth}, function_name={self._function_name}, "
@@ -117,7 +117,6 @@ def func(df: ArrowDataFrame) -> list[ArrowSeries]:
             alias_output_names=None,
             backend_version=backend_version,
             version=version,
-            kwargs={},
         )
 
     @classmethod
@@ -148,7 +147,6 @@ def func(df: ArrowDataFrame) -> list[ArrowSeries]:
             alias_output_names=None,
             backend_version=backend_version,
             version=version,
-            kwargs={},
         )
 
     def __narwhals_namespace__(self: Self) -> ArrowNamespace:
@@ -315,7 +313,7 @@ def alias_output_names(names: Sequence[str]) -> Sequence[str]:
             alias_output_names=alias_output_names,
             backend_version=self._backend_version,
             version=self._version,
-            kwargs={**self._kwargs, "name": name},
+            kwargs=self._kwargs,
         )
 
     def null_count(self: Self) -> Self:

narwhals/_arrow/namespace.py

@@ -49,7 +49,7 @@ def _create_expr_from_callable(
         function_name: str,
         evaluate_output_names: Callable[[ArrowDataFrame], Sequence[str]],
         alias_output_names: Callable[[Sequence[str]], Sequence[str]] | None,
-        kwargs: dict[str, Any],
+        kwargs: dict[str, Any] | None = None,
     ) -> ArrowExpr:
         from narwhals._arrow.expr import ArrowExpr
 
@@ -75,7 +75,6 @@ def _create_expr_from_series(self: Self, series: ArrowSeries) -> ArrowExpr:
             alias_output_names=None,
             backend_version=self._backend_version,
             version=self._version,
-            kwargs={},
         )
 
     def _create_series_from_scalar(
@@ -142,7 +141,6 @@ def len(self: Self) -> ArrowExpr:
             alias_output_names=None,
             backend_version=self._backend_version,
             version=self._version,
-            kwargs={},
         )
 
     def all(self: Self) -> ArrowExpr:
@@ -165,7 +163,6 @@ def all(self: Self) -> ArrowExpr:
             alias_output_names=None,
             backend_version=self._backend_version,
             version=self._version,
-            kwargs={},
         )
 
     def lit(self: Self, value: Any, dtype: DType | None) -> ArrowExpr:
@@ -188,7 +185,6 @@ def _lit_arrow_series(_: ArrowDataFrame) -> ArrowSeries:
             alias_output_names=None,
             backend_version=self._backend_version,
             version=self._version,
-            kwargs={},
         )
 
     def all_horizontal(self: Self, *exprs: ArrowExpr) -> ArrowExpr:
@@ -202,7 +198,6 @@ def func(df: ArrowDataFrame) -> list[ArrowSeries]:
             function_name="all_horizontal",
             evaluate_output_names=combine_evaluate_output_names(*exprs),
             alias_output_names=combine_alias_output_names(*exprs),
-            kwargs={"exprs": exprs},
         )
 
     def any_horizontal(self: Self, *exprs: ArrowExpr) -> ArrowExpr:
@@ -387,11 +382,6 @@ def func(df: ArrowDataFrame) -> list[ArrowSeries]:
             function_name="concat_str",
             evaluate_output_names=combine_evaluate_output_names(*exprs),
             alias_output_names=combine_alias_output_names(*exprs),
-            kwargs={
-                "exprs": exprs,
-                "separator": separator,
-                "ignore_nulls": ignore_nulls,
-            },
         )
 
 
@@ -466,7 +456,6 @@ def then(self: Self, value: ArrowExpr | ArrowSeries | Any) -> ArrowThen:
             alias_output_names=getattr(value, "_alias_output_names", None),
             backend_version=self._backend_version,
             version=self._version,
-            kwargs={"value": value},
         )
 
 
@@ -481,7 +470,7 @@ def __init__(
         alias_output_names: Callable[[Sequence[str]], Sequence[str]] | None,
         backend_version: tuple[int, ...],
         version: Version,
-        kwargs: dict[str, Any],
+        kwargs: dict[str, Any] | None = None,
     ) -> None:
         self._backend_version = backend_version
         self._version = version
@@ -490,7 +479,7 @@ def __init__(
         self._function_name = function_name
         self._evaluate_output_names = evaluate_output_names  # pyright: ignore[reportAttributeAccessIssue]
         self._alias_output_names = alias_output_names
-        self._kwargs = kwargs
+        self._kwargs = kwargs or {}
 
     def otherwise(self: Self, value: ArrowExpr | ArrowSeries | Any) -> ArrowExpr:
         # type ignore because we are setting the `_call` attribute to a

narwhals/_arrow/selectors.py

@@ -36,7 +36,7 @@ def func(df: ArrowDataFrame) -> list[ArrowSeries]:
         def evaluate_output_names(df: ArrowDataFrame) -> Sequence[str]:
             return [col for col in df.columns if df.schema[col] in dtypes]
 
-        return selector(self, func, evaluate_output_names, {"dtypes": dtypes})
+        return selector(self, func, evaluate_output_names)
 
     def matches(self: Self, pattern: str) -> ArrowSelector:
         def func(df: ArrowDataFrame) -> list[ArrowSeries]:
@@ -45,7 +45,7 @@ def func(df: ArrowDataFrame) -> list[ArrowSeries]:
         def evaluate_output_names(df: ArrowDataFrame) -> Sequence[str]:
             return [col for col in df.columns if re.search(pattern, col)]
 
-        return selector(self, func, evaluate_output_names, {"pattern": pattern})
+        return selector(self, func, evaluate_output_names)
 
     def numeric(self: Self) -> ArrowSelector:
         dtypes = import_dtypes_module(self._version)
@@ -82,7 +82,7 @@ def all(self: Self) -> ArrowSelector:
         def func(df: ArrowDataFrame) -> list[ArrowSeries]:
             return [df[col] for col in df.columns]
 
-        return selector(self, func, lambda df: df.columns, {})
+        return selector(self, func, lambda df: df.columns)
 
     def datetime(
         self: Self,
@@ -118,7 +118,7 @@ def evaluate_output_names(df: ArrowDataFrame) -> Sequence[str]:
                 )
             ]
 
-        return selector(self, func, evaluate_output_names, {})
+        return selector(self, func, evaluate_output_names)
 
 
 class ArrowSelector(ArrowExpr):
@@ -134,7 +134,6 @@ def _to_expr(self: Self) -> ArrowExpr:
             alias_output_names=self._alias_output_names,
             backend_version=self._backend_version,
             version=self._version,
-            kwargs=self._kwargs,
         )
 
     def __sub__(self: Self, other: Self | Any) -> ArrowSelector | Any:
@@ -151,9 +150,7 @@ def evaluate_output_names(df: ArrowDataFrame) -> list[str]:
                 rhs_names = other._evaluate_output_names(df)
                 return [x for x in lhs_names if x not in rhs_names]
 
-            return selector(
-                self, call, evaluate_output_names, {**self._kwargs, "other": other}
-            )
+            return selector(self, call, evaluate_output_names)
         else:
             return self._to_expr() - other
 
@@ -175,9 +172,7 @@ def evaluate_output_names(df: ArrowDataFrame) -> list[str]:
                 rhs_names = other._evaluate_output_names(df)
                 return [*(x for x in lhs_names if x not in rhs_names), *rhs_names]
 
-            return selector(
-                self, call, evaluate_output_names, {**self._kwargs, "other": other}
-            )
+            return selector(self, call, evaluate_output_names)
         else:
             return self._to_expr() | other
 
@@ -195,9 +190,7 @@ def evaluate_output_names(df: ArrowDataFrame) -> list[str]:
                 rhs_names = other._evaluate_output_names(df)
                 return [x for x in lhs_names if x in rhs_names]
 
-            return selector(
-                self, call, evaluate_output_names, {**self._kwargs, "other": other}
-            )
+            return selector(self, call, evaluate_output_names)
 
         else:
             return self._to_expr() & other
@@ -210,7 +203,6 @@ def selector(
     context: _LimitedContext,
     call: Callable[[ArrowDataFrame], Sequence[ArrowSeries]],
     evaluate_output_names: Callable[[ArrowDataFrame], Sequence[str]],
-    kwargs: dict[str, Any],
     /,
 ) -> ArrowSelector:
     return ArrowSelector(
@@ -221,5 +213,4 @@ def selector(
         alias_output_names=None,
         backend_version=context._backend_version,
         version=context._version,
-        kwargs=kwargs,
     )

narwhals/_pandas_like/expr.py

@@ -431,29 +431,29 @@ def over(self: Self, keys: list[str]) -> Self:
             def func(df: PandasLikeDataFrame) -> list[PandasLikeSeries]:
                 output_names, aliases = evaluate_output_names_and_aliases(self, df, [])
 
-                reverse = self._kwargs.get("reverse", False)
-                if reverse:
-                    msg = (
-                        "Cumulative operation with `reverse=True` is not supported in "
-                        "over context for pandas-like backend."
-                    )
-                    raise NotImplementedError(msg)
-
+                unsupported_reverse_msg = (
+                    "Cumulative operation with `reverse=True` is not supported in "
+                    "over context for pandas-like backend."
+                )
                 if function_name == "cum_count":
+                    if self._kwargs["reverse"]:
+                        raise NotImplementedError(unsupported_reverse_msg)
                     plx = self.__narwhals_namespace__()
                     df = df.with_columns(~plx.col(*output_names).is_null())
 
                 if function_name == "shift":
                     kwargs = {"periods": self._kwargs["n"]}
                 elif function_name == "rank":
-                    _method = self._kwargs.get("method", "average")
+                    _method = self._kwargs["method"]
                     kwargs = {
                         "method": "first" if _method == "ordinal" else _method,
                         "ascending": not self._kwargs["descending"],
                         "na_option": "keep",
                         "pct": False,
                     }
                 else:  # Cumulative operation
+                    if self._kwargs["reverse"]:
+                        raise NotImplementedError(unsupported_reverse_msg)
                     kwargs = {"skipna": True}
 
                 res_native = getattr(

narwhals/_pandas_like/selectors.py

@@ -37,7 +37,7 @@ def func(df: PandasLikeDataFrame) -> list[PandasLikeSeries]:
         def evaluate_output_names(df: PandasLikeDataFrame) -> Sequence[str]:
             return [col for col in df.columns if df.schema[col] in dtypes]
 
-        return selector(self, func, evaluate_output_names, {"dtypes": dtypes})
+        return selector(self, func, evaluate_output_names)
 
     def matches(self: Self, pattern: str) -> PandasSelector:
         def func(df: PandasLikeDataFrame) -> list[PandasLikeSeries]:
@@ -46,7 +46,7 @@ def func(df: PandasLikeDataFrame) -> list[PandasLikeSeries]:
         def evaluate_output_names(df: PandasLikeDataFrame) -> Sequence[str]:
             return [col for col in df.columns if re.search(pattern, col)]
 
-        return selector(self, func, evaluate_output_names, {"pattern": pattern})
+        return selector(self, func, evaluate_output_names)
 
     def numeric(self: Self) -> PandasSelector:
         dtypes = import_dtypes_module(self._version)
@@ -83,7 +83,7 @@ def all(self: Self) -> PandasSelector:
         def func(df: PandasLikeDataFrame) -> list[PandasLikeSeries]:
             return [df[col] for col in df.columns]
 
-        return selector(self, func, lambda df: df.columns, {})
+        return selector(self, func, lambda df: df.columns)
 
     def datetime(
         self: Self,
@@ -119,7 +119,7 @@ def evaluate_output_names(df: PandasLikeDataFrame) -> Sequence[str]:
                 )
             ]
 
-        return selector(self, func, evaluate_output_names, {})
+        return selector(self, func, evaluate_output_names)
 
 
 class PandasSelector(PandasLikeExpr):
@@ -155,9 +155,7 @@ def evaluate_output_names(df: PandasLikeDataFrame) -> list[str]:
                 rhs_names = other._evaluate_output_names(df)
                 return [x for x in lhs_names if x not in rhs_names]
 
-            return selector(
-                self, call, evaluate_output_names, {**self._kwargs, "other": other}
-            )
+            return selector(self, call, evaluate_output_names)
         else:
             return self._to_expr() - other
 
@@ -179,9 +177,7 @@ def evaluate_output_names(df: PandasLikeDataFrame) -> list[str]:
                 rhs_names = other._evaluate_output_names(df)
                 return [*(x for x in lhs_names if x not in rhs_names), *rhs_names]
 
-            return selector(
-                self, call, evaluate_output_names, {**self._kwargs, "other": other}
-            )
+            return selector(self, call, evaluate_output_names)
         else:
             return self._to_expr() | other
 
@@ -199,9 +195,7 @@ def evaluate_output_names(df: PandasLikeDataFrame) -> list[str]:
                 rhs_names = other._evaluate_output_names(df)
                 return [x for x in lhs_names if x in rhs_names]
 
-            return selector(
-                self, call, evaluate_output_names, {**self._kwargs, "other": other}
-            )
+            return selector(self, call, evaluate_output_names)
         else:
             return self._to_expr() & other
 
@@ -213,7 +207,6 @@ def selector(
     context: _FullContext,
     call: Callable[[PandasLikeDataFrame], Sequence[PandasLikeSeries]],
     evaluate_output_names: Callable[[PandasLikeDataFrame], Sequence[str]],
-    kwargs: dict[str, Any],
     /,
 ) -> PandasSelector:
     return PandasSelector(
@@ -225,5 +218,5 @@ def selector(
         implementation=context._implementation,
         backend_version=context._backend_version,
         version=context._version,
-        kwargs=kwargs,
+        kwargs={},
     )