Support NumPy array API (experimental) (#6804)

* Support NumPy array API (experimental)

* Address feedback

* Update xarray/core/indexing.py

Co-authored-by: Illviljan <14371165+Illviljan@users.noreply.github.com>

* Update xarray/core/indexing.py

Co-authored-by: Illviljan <14371165+Illviljan@users.noreply.github.com>

* Update xarray/tests/test_array_api.py

Co-authored-by: Illviljan <14371165+Illviljan@users.noreply.github.com>

* Update xarray/tests/test_array_api.py

Co-authored-by: Illviljan <14371165+Illviljan@users.noreply.github.com>

* Update xarray/tests/test_array_api.py

Co-authored-by: Illviljan <14371165+Illviljan@users.noreply.github.com>

* Update xarray/tests/test_array_api.py

Co-authored-by: Illviljan <14371165+Illviljan@users.noreply.github.com>

* Update xarray/tests/test_array_api.py

Co-authored-by: Illviljan <14371165+Illviljan@users.noreply.github.com>

* Fix import order

* Fix import order

* update whatsnew

Co-authored-by: Illviljan <14371165+Illviljan@users.noreply.github.com>
Co-authored-by: Deepak Cherian <dcherian@users.noreply.github.com>
Co-authored-by: Thomas Nicholas <thomas.nicholas@columbia.edu>

Author: 4 people

doc/whats-new.rst

@@ -30,6 +30,9 @@ New Features
   :py:meth:`coarsen`, :py:meth:`weighted`, :py:meth:`resample`,
   (:pull:`6702`)
   By `Michael Niklas <https://github.com/headtr1ck>`_.
+- Experimental support for wrapping any array type that conforms to the python array api standard.
+  (:pull:`6804`)
+  By `Tom White <https://github.com/tomwhite>`_.
 
 Deprecations
 ~~~~~~~~~~~~

xarray/core/duck_array_ops.py

@@ -329,7 +329,11 @@ def f(values, axis=None, skipna=None, **kwargs):
             if name in ["sum", "prod"]:
                 kwargs.pop("min_count", None)
 
-            func = getattr(np, name)
+            if hasattr(values, "__array_namespace__"):
+                xp = values.__array_namespace__()
+                func = getattr(xp, name)
+            else:
+                func = getattr(np, name)
 
         try:
             with warnings.catch_warnings():

xarray/core/indexing.py

@@ -679,6 +679,8 @@ def as_indexable(array):
         return DaskIndexingAdapter(array)
     if hasattr(array, "__array_function__"):
         return NdArrayLikeIndexingAdapter(array)
+    if hasattr(array, "__array_namespace__"):
+        return ArrayApiIndexingAdapter(array)
 
     raise TypeError(f"Invalid array type: {type(array)}")
 
@@ -1288,6 +1290,49 @@ def __init__(self, array):
         self.array = array
 
 
+class ArrayApiIndexingAdapter(ExplicitlyIndexedNDArrayMixin):
+    """Wrap an array API array to use explicit indexing."""
+
+    __slots__ = ("array",)
+
+    def __init__(self, array):
+        if not hasattr(array, "__array_namespace__"):
+            raise TypeError(
+                "ArrayApiIndexingAdapter must wrap an object that "
+                "implements the __array_namespace__ protocol"
+            )
+        self.array = array
+
+    def __getitem__(self, key):
+        if isinstance(key, BasicIndexer):
+            return self.array[key.tuple]
+        elif isinstance(key, OuterIndexer):
+            # manual orthogonal indexing (implemented like DaskIndexingAdapter)
+            key = key.tuple
+            value = self.array
+            for axis, subkey in reversed(list(enumerate(key))):
+                value = value[(slice(None),) * axis + (subkey, Ellipsis)]
+            return value
+        else:
+            if isinstance(key, VectorizedIndexer):
+                raise TypeError("Vectorized indexing is not supported")
+            else:
+                raise TypeError(f"Unrecognized indexer: {key}")
+
+    def __setitem__(self, key, value):
+        if isinstance(key, (BasicIndexer, OuterIndexer)):
+            self.array[key.tuple] = value
+        else:
+            if isinstance(key, VectorizedIndexer):
+                raise TypeError("Vectorized indexing is not supported")
+            else:
+                raise TypeError(f"Unrecognized indexer: {key}")
+
+    def transpose(self, order):
+        xp = self.array.__array_namespace__()
+        return xp.permute_dims(self.array, order)
+
+
 class DaskIndexingAdapter(ExplicitlyIndexedNDArrayMixin):
     """Wrap a dask array to support explicit indexing."""
 

xarray/core/utils.py

@@ -263,8 +263,10 @@ def is_duck_array(value: Any) -> bool:
         hasattr(value, "ndim")
         and hasattr(value, "shape")
         and hasattr(value, "dtype")
-        and hasattr(value, "__array_function__")
-        and hasattr(value, "__array_ufunc__")
+        and (
+            (hasattr(value, "__array_function__") and hasattr(value, "__array_ufunc__"))
+            or hasattr(value, "__array_namespace__")
+        )
     )
 
 
@@ -298,6 +300,7 @@ def _is_scalar(value, include_0d):
         or not (
             isinstance(value, (Iterable,) + NON_NUMPY_SUPPORTED_ARRAY_TYPES)
             or hasattr(value, "__array_function__")
+            or hasattr(value, "__array_namespace__")
         )
     )
 

xarray/core/variable.py

@@ -237,7 +237,9 @@ def as_compatible_data(data, fastpath=False):
         else:
             data = np.asarray(data)
 
-    if not isinstance(data, np.ndarray) and hasattr(data, "__array_function__"):
+    if not isinstance(data, np.ndarray) and (
+        hasattr(data, "__array_function__") or hasattr(data, "__array_namespace__")
+    ):
         return data
 
     # validate whether the data is valid data types.

xarray/tests/test_array_api.py

@@ -0,0 +1,51 @@
+from typing import Tuple
+
+import pytest
+
+import xarray as xr
+from xarray.testing import assert_equal
+
+np = pytest.importorskip("numpy", minversion="1.22")
+
+import numpy.array_api as xp  # isort:skip
+from numpy.array_api._array_object import Array  # isort:skip
+
+
+@pytest.fixture
+def arrays() -> Tuple[xr.DataArray, xr.DataArray]:
+    np_arr = xr.DataArray(np.ones((2, 3)), dims=("x", "y"), coords={"x": [10, 20]})
+    xp_arr = xr.DataArray(xp.ones((2, 3)), dims=("x", "y"), coords={"x": [10, 20]})
+    assert isinstance(xp_arr.data, Array)
+    return np_arr, xp_arr
+
+
+def test_arithmetic(arrays) -> None:
+    np_arr, xp_arr = arrays
+    expected = np_arr + 7
+    actual = xp_arr + 7
+    assert isinstance(actual.data, Array)
+    assert_equal(actual, expected)
+
+
+def test_aggregation(arrays) -> None:
+    np_arr, xp_arr = arrays
+    expected = np_arr.sum(skipna=False)
+    actual = xp_arr.sum(skipna=False)
+    assert isinstance(actual.data, Array)
+    assert_equal(actual, expected)
+
+
+def test_indexing(arrays) -> None:
+    np_arr, xp_arr = arrays
+    expected = np_arr[:, 0]
+    actual = xp_arr[:, 0]
+    assert isinstance(actual.data, Array)
+    assert_equal(actual, expected)
+
+
+def test_reorganizing_operation(arrays) -> None:
+    np_arr, xp_arr = arrays
+    expected = np_arr.transpose()
+    actual = xp_arr.transpose()
+    assert isinstance(actual.data, Array)
+    assert_equal(actual, expected)