How can I query the data of a complex return type using PyObject_CallObject? - c++

Question

I have a small python programm that computes a 2d positon
def getPosition(lerpParameter):
A = getClothoidConstant()
...
The python script can be found in my project folder here.
The function getPosition is included in the file clothoid.py. The function returns a value of type Vector2. How can I access the data of the returned Vector2d in my C++ program?
The C++ programm looks like this:
/// Get function
PyObject *pFunc = PyObject_GetAttrString(pModule, pid.functionName);
// pFunc is a new reference
if (pFunc && PyCallable_Check(pFunc))
{
PyObject *pArgs = PyTuple_New(pid.getArgumentCount());
PyObject *pValue = nullptr;
// setup function parameters
for (int i = 0; i < pid.getArgumentCount(); ++i)
{
if (pid.arguments[i].type == eType::Int)
{
pValue = PyLong_FromLong(atoi(pid.arguments[i].name.c_str()));
}
else
{
pValue = PyFloat_FromDouble(atof(pid.arguments[i].name.c_str()));
}
if (!pValue)
{
Py_DECREF(pArgs);
Py_DECREF(pModule);
std::cout << "Cannot convert argument" << std::endl;
throw std::runtime_error("Cannot convert argument");
}
// pValue reference stolen here:
PyTuple_SetItem(pArgs, i, pValue);
}
pValue = PyObject_CallObject(pFunc, pArgs);
Py_DECREF(pArgs);
if (pValue != nullptr)
{
switch (pid.returnType)
{
...
case eType::Double:
//std::cout << "Result of call: " << PyFloat_AsDouble(pValue) << std::endl;
doubleValue_ = PyFloat_AsDouble(pValue);
break;
case eType::Vector2d:
{
// How can I acccess the data here?
}
break;
default:
break;
}
Py_DECREF(pValue);
}
If the return type is a double or int it is easy to get the corresponding value. But I have no idea how to access the data of the Vector2.

Answer 1

If you want to get the 'x' attribute, and you know it's a float:
PyObject *temp = PyObject_GetAttrString(pValue, "x");
if (temp == NULL) {
// error handling
}
double x = PyFloat_AsDouble(temp);
// clean up reference when done with temp
Py_DECREF(temp);