losewayy · Nov 13, 2026
diff --git a/Lib/test/test_complex.py b/Lib/test/test_complex.py
@@ -711,6 +711,28 @@ def __complex__(self):
             check(complex(complex1(1j)), 0.0, 2.0)
         self.assertRaises(TypeError, complex, complex2(1j))
 
+    def test_constructor_float_subclass(self):
+        class FloatSubclass(float):
+            def __float__(self):
+                return 42.0
+
+        value = FloatSubclass(1.0)
+        for cls in complex, ComplexSubclass:
+            with self.subTest(cls=cls):
+                self.assertEqual(cls(value), 42+0j)
+                self.assertEqual(cls(real=value), 42+0j)
+                self.assertEqual(cls(value, 0), 42+0j)
+
+    def test_constructor_float_subclass_errors(self):
+        class FloatSubclass(float):
+            def __float__(self):
+                raise ValueError('float conversion failed')
+
+        for cls in complex, ComplexSubclass:
+            with self.subTest(cls=cls):
+                with self.assertRaisesRegex(ValueError, 'float conversion failed'):
+                    cls(FloatSubclass(1.0))
+
     def test___complex__(self):
         z = 3 + 4j
         self.assertEqual(z.__complex__(), z)

diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2026-11-14-02-00-00.gh-issue-161926.c7Q8nD.rst b/Misc/NEWS.d/next/Core_and_Builtins/2026-11-14-02-00-00.gh-issue-161926.c7Q8nD.rst
@@ -0,0 +1,2 @@
+Fix :class:`complex` ignoring an overridden :meth:`~object.__float__` method of a
+:class:`float` subclass when called with a single positional argument.
diff --git a/Objects/complexobject.c b/Objects/complexobject.c
@@ -1176,10 +1176,13 @@ actual_complex_new(PyTypeObject *type, PyObject *args, PyObject *kwargs)
         /* The argument really is entirely real, and contributes
            nothing in the imaginary direction.
            Just treat it as a double. */
-        double r = PyFloat_AsDouble(arg);
-        if (r != -1.0 || !PyErr_Occurred()) {
-            res = complex_subtype_from_doubles(type, r, 0);
+        tmp = PyNumber_Float(arg);
+        if (tmp == NULL) {
+            return NULL;
         }
+        double r = PyFloat_AS_DOUBLE(tmp);
+        Py_DECREF(tmp);
+        res = complex_subtype_from_doubles(type, r, 0);
     }
     else {
         PyErr_Format(PyExc_TypeError,
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,2 @@
		Fix :class:`complex` ignoring an overridden :meth:`~object.__float__` method of a
		:class:`float` subclass when called with a single positional argument.