API: Ensure np.vectorize outputs can be subclasses.

As is, this is true for the ufunc case, but not for the gufunc case,
even if the underlying function does produce a subclass.  Given the
care taken to ensure inputs are kept as subclasses, this is almost
certainly an oversight, which is here corrected.

1 files changed, 21 insertions, 1 deletions

diff --git a/numpy/lib/tests/test_function_base.py b/numpy/lib/tests/test_function_base.py
index a4f49a78b..e1b615223 100644
--- a/numpy/lib/tests/test_function_base.py
+++ b/numpy/lib/tests/test_function_base.py
@@ -1665,6 +1665,26 @@ class TestVectorize:
         with assert_raises_regex(ValueError, 'new output dimensions'):
             f(x)
 
+    def test_subclasses(self):
+        class subclass(np.ndarray):
+            pass
+
+        m = np.array([[1., 0., 0.],
+                      [0., 0., 1.],
+                      [0., 1., 0.]]).view(subclass)
+        v = np.array([[1., 2., 3.], [4., 5., 6.], [7., 8., 9.]]).view(subclass)
+        # generalized (gufunc)
+        matvec = np.vectorize(np.matmul, signature='(m,m),(m)->(m)')
+        r = matvec(m, v)
+        assert_equal(type(r), subclass)
+        assert_equal(r, [[1., 3., 2.], [4., 6., 5.], [7., 9., 8.]])
+
+        # element-wise (ufunc)
+        mult = np.vectorize(lambda x, y: x*y)
+        r = mult(m, v)
+        assert_equal(type(r), subclass)
+        assert_equal(r, m * v)
+
 
 class TestLeaks:
     class A:
@@ -1798,7 +1818,7 @@ class TestUnwrap:
         assert_array_equal(unwrap([1, 1 + 2 * np.pi]), [1, 1])
         # check that unwrap maintains continuity
         assert_(np.all(diff(unwrap(rand(10) * 100)) < np.pi))
-    
+
     def test_period(self):
         # check that unwrap removes jumps greater that 255
         assert_array_equal(unwrap([1, 1 + 256], period=255), [1, 2])