Add methods __bool__, __float__ and __int__ to usm_ndarray

Author: densmirn

dpctl/tensor/_usmarray.pyx

@@ -491,6 +491,36 @@ cdef class usm_ndarray:
         res.flags_ |= (self.flags_ & USM_ARRAY_WRITEABLE)
         return res
 
+    def __bool__(self):
+        if self.size == 1:
+            return self.usm_data.copy_to_host().view(self.dtype).__bool__()
+
+        if self.size == 0:
+            raise ValueError(
+                "The truth value of an empty array is ambiguous"
+            )
+
+        raise ValueError(
+            "The truth value of an array with more than one element is "
+            "ambiguous. Use a.any() or a.all()"
+        )
+
+    def __float__(self):
+        if self.size == 1:
+            return self.usm_data.copy_to_host().view(self.dtype).__float__()
+
+        raise ValueError(
+            "only size-1 arrays can be converted to Python scalars"
+        )
+
+    def __int__(self):
+        if self.size == 1:
+            return self.usm_data.copy_to_host().view(self.dtype).__int__()
+
+        raise ValueError(
+            "only size-1 arrays can be converted to Python scalars"
+        )
+
     def to_device(self, target_device):
         """
         Transfer array to target device

dpctl/tests/test_usm_ndarray_ctor.py

@@ -114,6 +114,32 @@ def test_properties():
     assert isinstance(X.ndim, numbers.Integral)
 
 
+@pytest.mark.parametrize("func", [bool, float, int])
+@pytest.mark.parametrize("shape", [(1,), (1, 1), (1, 1, 1)])
+def test_copy_scalar_with_func(func, shape):
+    X = dpt.usm_ndarray(shape)
+    Y = np.arange(1, X.size + 1, dtype=X.dtype)
+    X.usm_data.copy_from_host(Y.view("|u1"))
+    assert func(X) == func(Y)
+
+
+@pytest.mark.parametrize("method", ["__bool__", "__float__", "__int__"])
+@pytest.mark.parametrize("shape", [(1,), (1, 1), (1, 1, 1)])
+def test_copy_scalar_with_method(method, shape):
+    X = dpt.usm_ndarray(shape)
+    Y = np.arange(1, X.size + 1, dtype=X.dtype)
+    X.usm_data.copy_from_host(Y.view("|u1"))
+    assert getattr(X, method)() == getattr(Y, method)()
+
+
+@pytest.mark.parametrize("func", [bool, float, int])
+@pytest.mark.parametrize("shape", [(2,), (1, 2), (3, 4, 5), (0,)])
+def test_copy_scalar_invalid_shape(func, shape):
+    X = dpt.usm_ndarray(shape)
+    with pytest.raises(ValueError):
+        func(X)
+
+
 @pytest.mark.parametrize(
     "ind",
     [