chore: Spec CompliantSeries

narwhals/_arrow/namespace.py

@@ -65,7 +65,7 @@ def len(self: Self) -> ArrowExpr:
         # coverage bug? this is definitely hit
         return self._expr(  # pragma: no cover
             lambda df: [
-                ArrowSeries._from_iterable(
+                ArrowSeries.from_iterable(
                     [len(df._native_frame)], name="len", context=self
                 )
             ],
@@ -79,7 +79,7 @@ def len(self: Self) -> ArrowExpr:
 
     def lit(self: Self, value: Any, dtype: DType | None) -> ArrowExpr:
         def _lit_arrow_series(_: ArrowDataFrame) -> ArrowSeries:
-            arrow_series = ArrowSeries._from_iterable(
+            arrow_series = ArrowSeries.from_iterable(
                 data=[value], name="literal", context=self
             )
             if dtype:

narwhals/_arrow/series.py

@@ -5,6 +5,7 @@
 from typing import Iterable
 from typing import Iterator
 from typing import Literal
+from typing import Mapping
 from typing import Sequence
 from typing import cast
 from typing import overload
@@ -32,6 +33,7 @@
 from narwhals.utils import Implementation
 from narwhals.utils import generate_temporary_column_name
 from narwhals.utils import import_dtypes_module
+from narwhals.utils import not_implemented
 from narwhals.utils import validate_backend_version
 
 if TYPE_CHECKING:
@@ -139,12 +141,8 @@ def _from_native_series(
         )
 
     @classmethod
-    def _from_iterable(
-        cls: type[Self],
-        data: Iterable[Any],
-        name: str,
-        *,
-        context: _FullContext,
+    def from_iterable(
+        cls, data: Iterable[Any], *, context: _FullContext, name: str = ""
     ) -> Self:
         return cls(
             chunked_array([data]),
@@ -160,8 +158,8 @@ def _from_scalar(self, value: Any) -> Self:
 
     @classmethod
     def from_numpy(cls, data: Into1DArray, /, *, context: _FullContext) -> Self:
-        return cls._from_iterable(
-            data if is_numpy_array_1d(data) else [data], name="", context=context
+        return cls.from_iterable(
+            data if is_numpy_array_1d(data) else [data], context=context
         )
 
     def __narwhals_namespace__(self: Self) -> ArrowNamespace:
@@ -171,9 +169,6 @@ def __narwhals_namespace__(self: Self) -> ArrowNamespace:
             backend_version=self._backend_version, version=self._version
         )
 
-    def __len__(self: Self) -> int:
-        return len(self.native)
-
     def __eq__(self: Self, other: object) -> Self:  # type: ignore[override]
         ser, other = extract_native(self, other)
         return self._from_native_series(pc.equal(ser, other))  # type: ignore[arg-type]
@@ -391,9 +386,6 @@ def __native_namespace__(self: Self) -> ModuleType:
     def name(self: Self) -> str:
         return self._name
 
-    def __narwhals_series__(self: Self) -> Self:
-        return self
-
     @overload
     def __getitem__(self: Self, idx: int) -> Any: ...
 
@@ -569,7 +561,7 @@ def arg_true(self: Self) -> Self:
         import numpy as np  # ignore-banned-import
 
         res = np.flatnonzero(self.native)
-        return self._from_iterable(res, name=self.name, context=self)
+        return self.from_iterable(res, name=self.name, context=self)
 
     def item(self: Self, index: int | None = None) -> Any:
         if index is None:
@@ -753,7 +745,11 @@ def unique(self: Self, *, maintain_order: bool) -> Self:
         return self._from_native_series(self.native.unique())
 
     def replace_strict(
-        self: Self, old: Sequence[Any], new: Sequence[Any], *, return_dtype: DType | None
+        self: Self,
+        old: Sequence[Any] | Mapping[Any, Any],
+        new: Sequence[Any],
+        *,
+        return_dtype: DType | type[DType] | None,
     ) -> Self:
         # https://stackoverflow.com/a/79111029/4451315
         idxs = pc.index_in(self.native, pa.array(old))
@@ -1217,3 +1213,5 @@ def list(self: Self) -> ArrowSeriesListNamespace:
     @property
     def struct(self: Self) -> ArrowSeriesStructNamespace:
         return ArrowSeriesStructNamespace(self)
+
+    ewm_mean = not_implemented()

narwhals/_compliant/__init__.py

@@ -24,6 +24,7 @@
 from narwhals._compliant.typing import EagerSeriesT
 from narwhals._compliant.typing import IntoCompliantExpr
 from narwhals._compliant.typing import NativeFrameT_co
+from narwhals._compliant.typing import NativeSeriesT_co
 
 __all__ = [
     "CompliantDataFrame",
@@ -50,4 +51,5 @@
     "LazyExpr",
     "LazySelectorNamespace",
     "NativeFrameT_co",
+    "NativeSeriesT_co",
 ]

narwhals/_compliant/expr.py

@@ -183,7 +183,7 @@ def quantile(
     ) -> Self: ...
     def map_batches(
         self,
-        function: Callable[[CompliantSeries], CompliantExpr[Any, Any]],
+        function: Callable[[CompliantSeries[Any]], CompliantExpr[Any, Any]],
         return_dtype: DType | type[DType] | None,
     ) -> Self: ...
 

narwhals/_compliant/selectors.py

@@ -62,8 +62,8 @@
 ]
 
 
-SeriesOrExprT = TypeVar("SeriesOrExprT", bound="CompliantSeries | NativeExpr")
-SeriesT = TypeVar("SeriesT", bound="CompliantSeries")
+SeriesOrExprT = TypeVar("SeriesOrExprT", bound="CompliantSeries[Any] | NativeExpr")
+SeriesT = TypeVar("SeriesT", bound="CompliantSeries[Any]")
 ExprT = TypeVar("ExprT", bound="NativeExpr")
 FrameT = TypeVar(
     "FrameT", bound="CompliantDataFrame[Any, Any, Any] | CompliantLazyFrame[Any, Any]"