Allow iteration on 1-D arrays

array_api_strict/_array_object.py

@@ -677,10 +677,16 @@ def __iter__(self: Array, /):
         """
         Performs the operation __iter__.
         """
-        # Manually disable iteration, since __getitem__ raises IndexError on
-        # things like ones((3, 3))[0], which causes list(ones((3, 3))) to give
-        # [].
-        raise TypeError("array iteration is not allowed in array-api-strict")
+        # Manually disable iteration on higher dimensional arrays, since
+        # __getitem__ raises IndexError on things like ones((3, 3))[0], which
+        # causes list(ones((3, 3))) to give [].
+        if self.ndim > 1:
+            raise TypeError("array iteration is not allowed in array-api-strict")
+        # Allow iteration for 1-D arrays. The array API doesn't strictly
+        # define __iter__, but it doesn't disallow it. The default Python
+        # behavior is to implement iter as a[0], a[1], ... when __getitem__ is
+        # implemented, which implies iteration on 1-D arrays.
+        return (Array._new(i) for i in self._array)
 
     def __le__(self: Array, other: Union[int, float, Array], /) -> Array:
         """

array_api_strict/tests/test_array_object.py

@@ -1,4 +1,5 @@
 import operator
+from builtins import all as all_
 
 from numpy.testing import assert_raises, suppress_warnings
 import numpy as np
@@ -21,6 +22,7 @@
     int32,
     int64,
     uint64,
+    float64,
     bool as bool_,
 )
 from .._flags import set_array_api_strict_flags
@@ -423,8 +425,12 @@ def test_array_namespace():
     pytest.raises(ValueError, lambda: a.__array_namespace__(api_version="2021.11"))
     pytest.raises(ValueError, lambda: a.__array_namespace__(api_version="2024.12"))
 
-def test_no_iter():
-    pytest.raises(TypeError, lambda: iter(ones(3)))
+def test_iter():
+    pytest.raises(TypeError, lambda: iter(asarray(3)))
+    assert list(ones(3)) == [asarray(1.), asarray(1.), asarray(1.)]
+    assert all_(isinstance(a, Array) for a in iter(ones(3)))
+    assert all_(a.shape == () for a in iter(ones(3)))
+    assert all_(a.dtype == float64 for a in iter(ones(3)))
     pytest.raises(TypeError, lambda: iter(ones((3, 3))))
 
 @pytest.mark.parametrize("api_version", ['2021.12', '2022.12', '2023.12'])

docs/changelog.md

@@ -1,5 +1,14 @@
 # Changelog
 
+### 2.0.1 (2024-07-01)
+
+## Minor Changes
+
+- Re-allow iteration on 1-D arrays. A change from 2.0 fixed iter() raising on
+  n-D arrays but also made 1-D arrays raise. The standard does not explicitly
+  disallow iteration on 1-D arrays, and the default Python `__iter__`
+  implementation allows it to work, so for now, it is kept intact as working.
+
 ## 2.0 (2024-06-27)
 
 ### Major Changes