fix(python): Respect dtype and strict in pl.Series's constructo…

…r for pyarrow arrays, numpy arrays, and pyarrow-backed pandas (#15962)

py-polars/polars/_utils/construction/series.py

@@ -402,14 +402,15 @@ def pandas_to_pyseries(
     values: pd.Series[Any] | pd.Index[Any] | pd.DatetimeIndex,
     dtype: PolarsDataType | None = None,
     *,
+    strict: bool = True,
     nan_to_null: bool = True,
 ) -> PySeries:
     """Construct a PySeries from a pandas Series or DatetimeIndex."""
     if not name and values.name is not None:
         name = str(values.name)
     if is_simple_numpy_backed_pandas_series(values):
         return pl.Series(
-            name, values.to_numpy(), dtype=dtype, nan_to_null=nan_to_null
+            name, values.to_numpy(), dtype=dtype, nan_to_null=nan_to_null, strict=strict
         )._s
     if not _PYARROW_AVAILABLE:
         msg = (
@@ -419,11 +420,21 @@ def pandas_to_pyseries(
         )
         raise ImportError(msg)
     return arrow_to_pyseries(
-        name, plc.pandas_series_to_arrow(values, nan_to_null=nan_to_null)
+        name,
+        plc.pandas_series_to_arrow(values, nan_to_null=nan_to_null),
+        dtype=dtype,
+        strict=strict,
     )
 
 
-def arrow_to_pyseries(name: str, values: pa.Array, *, rechunk: bool = True) -> PySeries:
+def arrow_to_pyseries(
+    name: str,
+    values: pa.Array,
+    dtype: PolarsDataType | None = None,
+    *,
+    strict: bool = True,
+    rechunk: bool = True,
+) -> PySeries:
     """Construct a PySeries from an Arrow array."""
     array = plc.coerce_arrow(values)
 
@@ -460,7 +471,7 @@ def arrow_to_pyseries(name: str, values: pa.Array, *, rechunk: bool = True) -> P
         if rechunk:
             pys.rechunk(in_place=True)
 
-    return pys
+    return pys.cast(dtype, strict=strict) if dtype is not None else pys
 
 
 def numpy_to_pyseries(

py-polars/polars/series/series.py

@@ -343,17 +343,17 @@ def __init__(
                     return
 
             if dtype is not None:
-                self._s = self.cast(dtype, strict=True)._s
+                self._s = self.cast(dtype, strict=strict)._s
 
         elif _check_for_pyarrow(values) and isinstance(
             values, (pa.Array, pa.ChunkedArray)
         ):
-            self._s = arrow_to_pyseries(name, values)
+            self._s = arrow_to_pyseries(name, values, dtype=dtype, strict=strict)
 
         elif _check_for_pandas(values) and isinstance(
             values, (pd.Series, pd.Index, pd.DatetimeIndex)
         ):
-            self._s = pandas_to_pyseries(name, values, dtype=dtype)
+            self._s = pandas_to_pyseries(name, values, dtype=dtype, strict=strict)
 
         elif _is_generator(values):
             self._s = iterable_to_pyseries(name, values, dtype=dtype, strict=strict)

py-polars/tests/unit/series/test_series.py

@@ -2340,5 +2340,44 @@ def test_search_sorted(
 
 
 def test_series_from_pandas_with_dtype() -> None:
-    s = pl.Series("foo", pd.Series([1, 2, 3]), pl.Float32)
-    assert_series_equal(s, pl.Series("foo", [1, 2, 3], dtype=pl.Float32))
+    expected = pl.Series("foo", [1, 2, 3], dtype=pl.Int8)
+    s = pl.Series("foo", pd.Series([1, 2, 3]), pl.Int8)
+    assert_series_equal(s, expected)
+    s = pl.Series("foo", pd.Series([1, 2, 3], dtype="Int16"), pl.Int8)
+    assert_series_equal(s, expected)
+
+    with pytest.raises(pl.ComputeError, match="conversion from"):
+        pl.Series("foo", pd.Series([-1, 2, 3]), pl.UInt8)
+    s = pl.Series("foo", pd.Series([-1, 2, 3]), pl.UInt8, strict=False)
+    assert s.to_list() == [None, 2, 3]
+    assert s.dtype == pl.UInt8
+
+    with pytest.raises(pl.ComputeError, match="conversion from"):
+        pl.Series("foo", pd.Series([-1, 2, 3], dtype="Int8"), pl.UInt8)
+    s = pl.Series("foo", pd.Series([-1, 2, 3], dtype="Int8"), pl.UInt8, strict=False)
+    assert s.to_list() == [None, 2, 3]
+    assert s.dtype == pl.UInt8
+
+
+def test_series_from_pyarrow_with_dtype() -> None:
+    s = pl.Series("foo", pa.array([-1, 2, 3]), pl.Int8)
+    assert_series_equal(s, pl.Series("foo", [-1, 2, 3], dtype=pl.Int8))
+
+    with pytest.raises(pl.ComputeError, match="conversion from"):
+        pl.Series("foo", pa.array([-1, 2, 3]), pl.UInt8)
+
+    s = pl.Series("foo", pa.array([-1, 2, 3]), dtype=pl.UInt8, strict=False)
+    assert s.to_list() == [None, 2, 3]
+    assert s.dtype == pl.UInt8
+
+
+def test_series_from_numpy_with_dtye() -> None:
+    s = pl.Series("foo", np.array([-1, 2, 3]), pl.Int8)
+    assert_series_equal(s, pl.Series("foo", [-1, 2, 3], dtype=pl.Int8))
+
+    with pytest.raises(pl.ComputeError, match="conversion from"):
+        pl.Series("foo", np.array([-1, 2, 3]), pl.UInt8)
+
+    s = pl.Series("foo", np.array([-1, 2, 3]), dtype=pl.UInt8, strict=False)
+    assert s.to_list() == [None, 2, 3]
+    assert s.dtype == pl.UInt8