The similar code with Python C API

void test_PythonAPI()
{
  double a_ = 3.4;
  PyObject* a = PyFloat_FromDouble(a_);
  PyObject* b = PyFloat_FromDouble(7);
  PyObject* c = PyNumber_Add(a, b); 
  PyObject* list = PyList_New(0);
  PyList_Append(list, a);
  PyList_Append(list, c);
  PyList_Append(list, b);
  PyObject* tp = PyList_AsTuple(list);
  int tp_len = PySequence_Length(tp);
  for (int i=0; i<tp_len; i++) {
    PyObject* qp = PySequence_GetItem(tp, i);
    double q = PyFloat_AS_DOUBLE(qp);
    std::cout << "tp[" << i << "]=" << q << " ";
  }
  std::cout << std::endl;
}