Only pass dtype to __array__, if not None: Fixes #3253 (#3257)

py-polars/polars/internals/series.py

@@ -2060,7 +2060,10 @@ def view(self, ignore_nulls: bool = False) -> np.ndarray:
         return array
 
     def __array__(self, dtype: Any = None) -> np.ndarray:
-        return self.to_numpy().__array__(dtype)
+        if dtype:
+            return self.to_numpy().__array__(dtype)
+        else:
+            return self.to_numpy().__array__()
 
     def __array_ufunc__(
         self, ufunc: Callable[..., Any], method: str, *inputs: Any, **kwargs: Any

py-polars/tests/test_interop.py

@@ -1,5 +1,5 @@
 from datetime import datetime
-from typing import Dict, Sequence, Union
+from typing import Dict, Sequence, Type, Union
 
 import numpy as np
 import pandas as pd
@@ -47,6 +47,40 @@ def test_from_numpy() -> None:
     assert out == df.dtypes
 
 
+def test_to_numpy() -> None:
+    def test_series_to_numpy(
+        name: str,
+        values: list,
+        pl_dtype: Type[pl.DataType],
+        np_dtype: Union[
+            Type[np.signedinteger],
+            Type[np.unsignedinteger],
+            Type[np.floating],
+            Type[np.object_],
+        ],
+    ) -> None:
+        pl_series_to_numpy_array = np.array(pl.Series(name, values, pl_dtype))
+        numpy_array = np.array(values, dtype=np_dtype)
+        assert pl_series_to_numpy_array.dtype == numpy_array.dtype
+        assert np.all(pl_series_to_numpy_array == numpy_array) == np.bool_(True)
+
+    test_series_to_numpy("int8", [1, 3, 2], pl.Int8, np.int8)
+    test_series_to_numpy("int16", [1, 3, 2], pl.Int16, np.int16)
+    test_series_to_numpy("int32", [1, 3, 2], pl.Int32, np.int32)
+    test_series_to_numpy("int64", [1, 3, 2], pl.Int64, np.int64)
+
+    test_series_to_numpy("uint8", [1, 3, 2], pl.UInt8, np.uint8)
+    test_series_to_numpy("uint16", [1, 3, 2], pl.UInt16, np.uint16)
+    test_series_to_numpy("uint32", [1, 3, 2], pl.UInt32, np.uint32)
+    test_series_to_numpy("uint64", [1, 3, 2], pl.UInt64, np.uint64)
+
+    test_series_to_numpy("float32", [21.7, 21.8, 21], pl.Float32, np.float32)
+    test_series_to_numpy("float64", [21.7, 21.8, 21], pl.Float64, np.float64)
+
+    test_series_to_numpy("str", ["string1", "string2", "string3"], pl.Utf8, np.object_)
+    # test_series_to_numpy("bytes", ["byte_string1", "byte_string2", "byte_string3"], pl.Object, np.bytes_)
+
+
 def test_from_pandas() -> None:
     df = pd.DataFrame(
         {