len_chars too

narwhals/_arrow/dataframe.py

@@ -333,7 +333,7 @@ def join(
         self: Self,
         other: Self,
         *,
-        how: Literal["left", "inner", "outer", "cross", "anti", "semi"],
+        how: Literal["left", "inner", "cross", "anti", "semi"],
         left_on: str | list[str] | None,
         right_on: str | list[str] | None,
         suffix: str,

narwhals/_dask/dataframe.py

@@ -236,7 +236,7 @@ def join(
         self: Self,
         other: Self,
         *,
-        how: Literal["left", "inner", "outer", "cross", "anti", "semi"] = "inner",
+        how: Literal["left", "inner", "cross", "anti", "semi"] = "inner",
         left_on: str | list[str] | None,
         right_on: str | list[str] | None,
         suffix: str,

narwhals/_duckdb/dataframe.py

@@ -215,7 +215,7 @@ def join(
         self: Self,
         other: Self,
         *,
-        how: Literal["left", "inner", "outer", "cross", "anti", "semi"] = "inner",
+        how: Literal["left", "inner", "cross", "anti", "semi"] = "inner",
         left_on: str | list[str] | None,
         right_on: str | list[str] | None,
         suffix: str,
@@ -226,10 +226,6 @@ def join(
             right_on = [right_on]
         original_alias = self._native_frame.alias
 
-        if how not in ("inner", "left", "semi", "cross"):
-            msg = "Only inner and left join is implemented for DuckDB"
-            raise NotImplementedError(msg)
-
         if how == "cross":
             if self._backend_version < (1, 1, 4):
                 msg = f"DuckDB>=1.1.4 is required for cross-join, found version: {self._backend_version}"

narwhals/_duckdb/expr.py

@@ -488,6 +488,15 @@ def min(self) -> Self:
             lambda _input: FunctionExpression("min", _input), "min", returns_scalar=True
         )
 
+    def null_count(self) -> Self:
+        from duckdb import FunctionExpression
+
+        return self._from_call(
+            lambda _input: FunctionExpression("sum", _input.isnull().cast("int")),
+            "null_count",
+            returns_scalar=True,
+        )
+
     def is_null(self) -> Self:
         return self._from_call(
             lambda _input: _input.isnull(), "is_null", returns_scalar=self._returns_scalar
@@ -619,6 +628,15 @@ def func(_input: duckdb.Expression) -> duckdb.Expression:
             func, "slice", returns_scalar=self._compliant_expr._returns_scalar
         )
 
+    def len_chars(self) -> DuckDBExpr:
+        from duckdb import FunctionExpression
+
+        return self._compliant_expr._from_call(
+            lambda _input: FunctionExpression("length", _input),
+            "len_chars",
+            returns_scalar=self._compliant_expr._returns_scalar,
+        )
+
     def to_lowercase(self) -> DuckDBExpr:
         from duckdb import FunctionExpression
 

narwhals/_pandas_like/dataframe.py

@@ -512,7 +512,7 @@ def join(
         self,
         other: Self,
         *,
-        how: Literal["left", "inner", "outer", "cross", "anti", "semi"] = "inner",
+        how: Literal["left", "inner", "cross", "anti", "semi"] = "inner",
         left_on: str | list[str] | None,
         right_on: str | list[str] | None,
         suffix: str,

tests/expr_and_series/null_count_test.py

@@ -16,7 +16,7 @@
 def test_null_count_expr(
     constructor: Constructor, request: pytest.FixtureRequest
 ) -> None:
-    if ("pyspark" in str(constructor)) or "duckdb" in str(constructor):
+    if "pyspark" in str(constructor):
         request.applymarker(pytest.mark.xfail)
     df = nw.from_native(constructor(data))
     result = df.select(nw.all().null_count())

tests/expr_and_series/str/len_chars_test.py

@@ -11,7 +11,7 @@
 
 
 def test_str_len_chars(constructor: Constructor, request: pytest.FixtureRequest) -> None:
-    if ("pyspark" in str(constructor)) or "duckdb" in str(constructor):
+    if "pyspark" in str(constructor):
         request.applymarker(pytest.mark.xfail)
     df = nw.from_native(constructor(data))
     result = df.select(nw.col("a").str.len_chars())

tests/frame/join_test.py

@@ -166,10 +166,7 @@ def test_anti_join(
     join_key: list[str],
     filter_expr: nw.Expr,
     expected: dict[str, list[Any]],
-    request: pytest.FixtureRequest,
 ) -> None:
-    if "duckdb" in str(constructor):
-        request.applymarker(pytest.mark.xfail)
     data = {"antananarivo": [1, 3, 2], "bob": [4, 4, 6], "zor ro": [7.0, 8, 9]}
     df = nw.from_native(constructor(data))
     other = df.filter(filter_expr)