BUG: Allow ExtensionArray to use void dtype #61637

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Merged

rhshadrach merged 14 commits into pandas-dev:main from flying-sheep:pa/void-dtype

Jan 31, 2026

+95 −1

doc/source/whatsnew/v3.0.1.rst

-Original file line number
+Diff line change
@@ Expand Up / @@ -15,6 +15,7 @@ Bug fixes @@
     ^^^^^^^^^
     - Fixed a bug in the :class:`DataFrame` constructor when passed a :class:`Series` or
       :class:`Index` correctly handling Copy-on-Write (:issue:`63899`)
+    - Allow :class:`.ExtensionArray` to have dtypes involving :class:`numpy.void` (:issue:`54810`)
     .. ---------------------------------------------------------------------------
     .. _whatsnew_301.contributors:
@@ Expand Down @@

pandas/core/generic.py

-Original file line number
+Diff line change
@@ Expand Up / @@ -477,7 +477,7 @@ def _validate_dtype(cls, dtype) -> DtypeObj | None: @@
                 dtype = pandas_dtype(dtype)
                 # a compound dtype
-                if dtype.kind == "V":
+                if dtype.kind == "V" and not isinstance(dtype, ExtensionDtype):
                     raise NotImplementedError(
                         "compound dtypes are not implemented "
                         f"in the {cls.__name__} constructor"
@@ Expand Down @@

pandas/tests/extension/uuid/__init__.py

Empty file.

pandas/tests/extension/uuid/test_uuid.py

-Original file line number
+Diff line change
@@ -0,0 +1,93 @@
+    from __future__ import annotations
+    from typing import (
+        TYPE_CHECKING,
+        ClassVar,
+        Self,
+    )
+    from uuid import UUID
+    import numpy as np
+    from pandas.core.dtypes.dtypes import ExtensionDtype
+    import pandas as pd
+    from pandas.core.arrays.base import ExtensionArray
+    if TYPE_CHECKING:
+        import builtins
+        from collections.abc import Iterable
+        from numpy.typing import NDArray
+        from pandas._typing import (
+            Dtype,
+            ScalarIndexer,
+        )
+    # 16 void bytes: 128 bit, every pattern valid, no funky behavior like 0 stripping.
+    _UuidNumpyDtype = np.dtype("V16")
+    class UuidDtype(ExtensionDtype):
+        # ExtensionDtype essential API (3 class attrs and methods)
+        name: ClassVar[str] = "uuid"
+        type: ClassVar[builtins.type[UUID]] = UUID
+        @classmethod
+        def construct_array_type(cls) -> builtins.type[UuidExtensionArray]:
+            return UuidExtensionArray
+        # ExtensionDtype overrides
+        kind: ClassVar[str] = _UuidNumpyDtype.kind
+    class UuidExtensionArray(ExtensionArray):
+        # Implementation details and convenience
+        _data: NDArray[np.void]
+        def __init__(self, values: Iterable[UUID], *, copy: bool = False) -> None:
+            self._data = np.array([x.bytes for x in values], dtype=_UuidNumpyDtype)
+        # Parts of ExtensionArray's essential API required for tests:
+        dtype: ClassVar[UuidDtype] = UuidDtype()
+        @classmethod
+        def _from_sequence(
+            cls,
+            scalars: Iterable[UUID],
+            *,
+            dtype: Dtype | None = None,
+            copy: bool = False,
+        ) -> Self:
+            if dtype is None:
+                dtype = UuidDtype()
+            return cls(scalars, copy=copy)
+        def __getitem__(self, index: ScalarIndexer) -> UUID:  # type: ignore[override]
+            assert isinstance(index, int | np.integer)
+            return UUID(bytes=self._data[index].tobytes())
+        def __len__(self) -> int:
+            return len(self._data)
+    def test_construct() -> None:
+        """Tests that we can construct UuidExtensionArray from a list of valid values."""
+        from uuid import uuid4
+        a = UuidExtensionArray([UUID(int=0), u := uuid4()])
+        assert a[0].int == 0
+        assert a[1] == u
+    def test_series() -> None:
+        """Tests that Series accepts (unstructured) void ExtensionDtypes."""
+        from uuid import uuid4
+        s = pd.Series([u := uuid4()], dtype=UuidDtype(), name="s")
+        assert str(u) in str(s)

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