Also ignore None in array_namespace

Author: asmeurer

array_api_compat/common/_helpers.py

@@ -236,7 +236,7 @@ def array_namespace(*xs, api_version=None, use_compat=None):
     ----------
     xs: arrays
         one or more arrays. xs can also be Python scalars (bool, int, float,
-        or complex), which are ignored.
+        complex, or None), which are ignored.
 
     api_version: str
         The newest version of the spec that you need support for (currently
@@ -299,7 +299,7 @@ def your_function(x, y):
 
     namespaces = set()
     for x in xs:
-        if isinstance(x, (bool, int, float, complex)):
+        if isinstance(x, (bool, int, float, complex, type(None))):
             continue
         elif is_numpy_array(x):
             from .. import numpy as numpy_namespace

tests/test_array_namespace.py

@@ -101,8 +101,10 @@ def test_python_scalars():
     pytest.raises(TypeError, lambda: array_namespace(1.0))
     pytest.raises(TypeError, lambda: array_namespace(1j))
     pytest.raises(TypeError, lambda: array_namespace(True))
+    pytest.raises(TypeError, lambda: array_namespace(None))
 
     assert array_namespace(a, 1) == xp
     assert array_namespace(a, 1.0) == xp
     assert array_namespace(a, 1j) == xp
     assert array_namespace(a, True) == xp
+    assert array_namespace(a, None) == xp