[Eager] fix to_uva_tensor without specific gpu number (#44937)

* [Eager] fix to_uva_tensor without specific gpu number

* Update test_tensor_uva.py

update test case

paddle/fluid/pybind/eager_functions.cc

@@ -870,10 +870,13 @@ static PyObject* eager_api_to_uva_tensor(PyObject* self,
   PyObject* obj = PyTuple_GET_ITEM(args, 0);
   auto array = py::cast<py::array>(py::handle(obj));
 
-  int device_id = 0;
-  PyObject* Py_device_id = PyTuple_GET_ITEM(args, 1);
-  if (Py_device_id) {
-    device_id = CastPyArg2AttrLong(Py_device_id, 1);
+  Py_ssize_t args_num = PyTuple_Size(args);
+  int64_t device_id = 0;
+  if (args_num > 1) {
+    PyObject* Py_device_id = PyTuple_GET_ITEM(args, 1);
+    if (Py_device_id) {
+      device_id = CastPyArg2AttrLong(Py_device_id, 1);
+    }
   }
 
   if (py::isinstance<py::array_t<int32_t>>(array)) {

python/paddle/fluid/tests/unittests/test_tensor_uva.py

@@ -47,10 +47,15 @@ class TestUVATensorFromNumpy(unittest.TestCase):
                 data = np.random.randint(10, size=[4, 5]).astype(dtype)
                 if _in_legacy_dygraph():
                     tensor = paddle.fluid.core.to_uva_tensor(data, 0)
+                    tensor2 = paddle.fluid.core.to_uva_tensor(data)
                 else:
                     tensor = core.eager.to_uva_tensor(data, 0)
+                    tensor2 = core.eager.to_uva_tensor(data)
+
                 self.assertTrue(tensor.place.is_gpu_place())
+                self.assertTrue(tensor2.place.is_gpu_place())
                 self.assertTrue(np.allclose(tensor.numpy(), data))
+                self.assertTrue(np.allclose(tensor2.numpy(), data))
 
     def test_uva_tensor_creation(self):
         with _test_eager_guard():