chore: More Polars typing, update 'used by', link to roadmap (#1377)

* chore: More _polars typing

* used by, roadmap

README.md

@@ -37,13 +37,13 @@ Get started!
 - [Join our community call](https://calendar.google.com/calendar/embed?src=27ff6dc5f598c1d94c1f6e627a1aaae680e2fac88f848bda1f2c7946ae74d5ab%40group.calendar.google.com)
 - [Read the contributing guide](https://github.com/narwhals-dev/narwhals/blob/main/CONTRIBUTING.md)
 
-## Used by / integrates with
+## Used by
 
 Join the party!
 
-- [Altair](https://github.com/vega/altair/)
-- [Hamilton](https://github.com/DAGWorks-Inc/hamilton/tree/main/examples/narwhals)
+- [altair](https://github.com/vega/altair/)
 - [marimo](https://github.com/marimo-team/marimo)
+- [panel-graphic-walker](https://github.com/panel-extensions/panel-graphic-walker)
 - [pymarginaleffects](https://github.com/vincentarelbundock/pymarginaleffects)
 - [py-shiny](https://github.com/posit-dev/py-shiny)
 - [rio](https://github.com/rio-labs/rio)

docs/roadmap_and_related.md

@@ -2,13 +2,8 @@
 
 ## Roadmap
 
-Priorities, as of September 2024, are:
-
-- Works towards supporting projects which have shown interest in Narwhals.
-- Add extra docs and tutorials to make the project more accessible and easy to get started with.
-- Improve support for cuDF, which we can't currently test in CI (unless NVIDIA helps us out :wink:) but
-  which we can and do test manually in Kaggle notebooks.
-- Define a lazy-only layer of support which can include DuckDB, Ibis, and PySpark.
+See [roadmap discussion on GitHub](https://github.com/narwhals-dev/narwhals/discussions/1370)
+for an up-to-date plan of future work.
 
 ## Related projects
 

narwhals/_polars/expr.py

@@ -11,6 +11,7 @@
 from narwhals.utils import Implementation
 
 if TYPE_CHECKING:
+    import polars as pl
     from typing_extensions import Self
 
     from narwhals.dtypes import DType
@@ -19,7 +20,7 @@
 
 class PolarsExpr:
     def __init__(
-        self, expr: Any, dtypes: DTypes, backend_version: tuple[int, ...]
+        self, expr: pl.Expr, dtypes: DTypes, backend_version: tuple[int, ...]
     ) -> None:
         self._native_expr = expr
         self._implementation = Implementation.POLARS
@@ -29,7 +30,7 @@ def __init__(
     def __repr__(self) -> str:  # pragma: no cover
         return "PolarsExpr"
 
-    def _from_native_expr(self, expr: Any) -> Self:
+    def _from_native_expr(self, expr: pl.Expr) -> Self:
         return self.__class__(
             expr, dtypes=self._dtypes, backend_version=self._backend_version
         )
@@ -147,8 +148,8 @@ class PolarsExprDateTimeNamespace:
     def __init__(self, expr: PolarsExpr) -> None:
         self._expr = expr
 
-    def __getattr__(self, attr: str) -> Any:
-        def func(*args: Any, **kwargs: Any) -> Any:
+    def __getattr__(self, attr: str) -> Callable[[Any], PolarsExpr]:
+        def func(*args: Any, **kwargs: Any) -> PolarsExpr:
             args, kwargs = extract_args_kwargs(args, kwargs)  # type: ignore[assignment]
             return self._expr._from_native_expr(
                 getattr(self._expr._native_expr.dt, attr)(*args, **kwargs)
@@ -161,8 +162,8 @@ class PolarsExprStringNamespace:
     def __init__(self, expr: PolarsExpr) -> None:
         self._expr = expr
 
-    def __getattr__(self, attr: str) -> Any:
-        def func(*args: Any, **kwargs: Any) -> Any:
+    def __getattr__(self, attr: str) -> Callable[[Any], PolarsExpr]:
+        def func(*args: Any, **kwargs: Any) -> PolarsExpr:
             args, kwargs = extract_args_kwargs(args, kwargs)  # type: ignore[assignment]
             return self._expr._from_native_expr(
                 getattr(self._expr._native_expr.str, attr)(*args, **kwargs)
@@ -175,8 +176,8 @@ class PolarsExprCatNamespace:
     def __init__(self, expr: PolarsExpr) -> None:
         self._expr = expr
 
-    def __getattr__(self, attr: str) -> Any:
-        def func(*args: Any, **kwargs: Any) -> Any:
+    def __getattr__(self, attr: str) -> Callable[[Any], PolarsExpr]:
+        def func(*args: Any, **kwargs: Any) -> PolarsExpr:
             args, kwargs = extract_args_kwargs(args, kwargs)  # type: ignore[assignment]
             return self._expr._from_native_expr(
                 getattr(self._expr._native_expr.cat, attr)(*args, **kwargs)
@@ -189,8 +190,8 @@ class PolarsExprNameNamespace:
     def __init__(self, expr: PolarsExpr) -> None:
         self._expr = expr
 
-    def __getattr__(self, attr: str) -> Any:
-        def func(*args: Any, **kwargs: Any) -> Any:
+    def __getattr__(self, attr: str) -> Callable[[Any], PolarsExpr]:
+        def func(*args: Any, **kwargs: Any) -> PolarsExpr:
             args, kwargs = extract_args_kwargs(args, kwargs)  # type: ignore[assignment]
             return self._expr._from_native_expr(
                 getattr(self._expr._native_expr.name, attr)(*args, **kwargs)