Add dpnp.ndarray.__contains__ (#2534)

The PR implements `__contains__` method which needs to define the `in`
operator for a `dpnp.ndarray`.

Author: antonwolfy

CHANGELOG.md

@@ -14,6 +14,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 * Added a new backend routine `syrk` from oneMKL to perform symmetric rank-k update which is used for a specialized matrix multiplication where the result is a symmetric matrix [2509](https://github.com/IntelPython/dpnp/pull/2509)
 * Added `timeout-minutes` property to GitHub jobs [#2526](https://github.com/IntelPython/dpnp/pull/2526)
 * Added implementation of `dpnp.ndarray.data` and `dpnp.ndarray.data.ptr` attributes [#2521](https://github.com/IntelPython/dpnp/pull/2521)
+* Added `dpnp.ndarray.__contains__` method [#2534](https://github.com/IntelPython/dpnp/pull/2534)
 
 ### Changed
 

dpnp/dpnp_array.py

@@ -242,7 +242,9 @@ def __bool__(self):
     def __complex__(self):
         return self._array_obj.__complex__()
 
-    # '__contains__',
+    def __contains__(self, value, /):
+        r"""Return :math:`\text{value in self}`."""
+        return (self == value).any()
 
     def __copy__(self):
         """

dpnp/tests/test_ndarray.py

@@ -74,6 +74,39 @@ def test_attributes(self):
         assert_equal(self.two.itemsize, self.two.dtype.itemsize)
 
 
+@testing.parameterize(*testing.product({"xp": [dpnp, numpy]}))
+class TestContains:
+    def test_basic(self):
+        a = self.xp.arange(10).reshape((2, 5))
+        assert 4 in a
+        assert 20 not in a
+
+    def test_broadcast(self):
+        xp = self.xp
+        a = xp.arange(6).reshape((2, 3))
+        assert 4 in a
+        assert xp.array([0, 1, 2]) in a
+        assert xp.array([5, 3, 4]) not in a
+
+    def test_broadcast_error(self):
+        a = self.xp.arange(10).reshape((2, 5))
+        with pytest.raises(
+            ValueError,
+            match="operands could not be broadcast together with shapes",
+        ):
+            self.xp.array([1, 2]) in a
+
+    def test_strides(self):
+        xp = self.xp
+        a = xp.arange(10).reshape((2, 5))
+        a = a[:, ::2]
+        assert 4 in a
+        assert 8 not in a
+        assert xp.full(a.shape[-1], fill_value=2) in a
+        assert xp.full_like(a, fill_value=7) in a
+        assert xp.full_like(a, fill_value=6) not in a
+
+
 class TestView:
     def test_none_dtype(self):
         a = numpy.ones((1, 2, 4), dtype=numpy.int32)