hi

src/tests/test_polars.py

@@ -7,7 +7,7 @@
 from zoneinfo import ZoneInfo
 
 from hypothesis import given
-from hypothesis.strategies import fixed_dictionaries, floats, none, sampled_from
+from hypothesis.strategies import dates, fixed_dictionaries, floats, none, sampled_from
 from polars import (
     Boolean,
     DataFrame,
@@ -58,6 +58,7 @@
     collect_series,
     columns_to_dict,
     convert_time_zone,
+    dataclass_to_row,
     drop_null_struct_series,
     ensure_expr_or_series,
     floor_datetime,
@@ -548,6 +549,27 @@ def test_dataframe_nested_twice(self) -> None:
         assert_frame_equal(result, expected)
 
 
+class TestDataClassToRow:
+    @given(data=fixed_dictionaries({"a": int64s() | none(), "b": floats() | none()}))
+    def test_basic_types(self, *, data: StrMapping) -> None:
+        @dataclass(kw_only=True)
+        class Row:
+            a: int | None = None
+            b: float | None = None
+
+        df = dataclass_to_row(Row(**data))
+        check_polars_dataframe(df, height=1, schema_list={"a": Int64, "b": Float64})
+
+    @given(data=fixed_dictionaries({"date": dates()}))
+    def test_date(self, *, data: StrMapping) -> None:
+        @dataclass(kw_only=True)
+        class Row:
+            date: dt.date | None = None
+
+        df = dataclass_to_row(Row(**data))
+        check_polars_dataframe(df, height=1, schema_list={"date": Date})
+
+
 class TestDatetimeUTC:
     @mark.parametrize(
         ("dtype", "time_zone"),

src/utilities/polars.py

@@ -506,6 +506,11 @@ def __str__(self) -> str:
         return f"DataFrame must be unique on {self.key!r}\n\n{self.df}"
 
 
+def dataclass_to_row(obj: Dataclass, /) -> DataFrame:
+    """Convert a dataclass into a 1-row DataFrame."""
+    return DataFrame([obj], orient="row")
+
+
 def drop_null_struct_series(series: Series, /) -> Series:
     """Drop nulls in a struct-dtype Series as per the <= 1.1 definition."""
     try: