generc_type xxxx is already registered

[kanaero]

Suppose in test_stl_binders.cpp we have two types mapping back to the same underlying c++ type in this case "unsigned int".

py::bind_vector<std::vector<unsigned int>>(global, "VectorInt");
py::bind_vector<std::vector<unsigned int>>(global, "AnotherVectorInt");

When importing the module, the error generic_type: type "AnotherVectorInt" is already registered! arises.

Are we disallowing type alias within python. Can we not refer to the same vector type using multiple python types ?

If we choose to keep the current behaviour of disallowing multiple aliases for the same underlying type we should improve the error message to say "generic_type: type "AnotherVectorInt" has underlying type "unsigned int" that is already registered.

[wjakob]

You can use global.attr("AnotherVectorInt") = global.attr("VectorInt") to create an alias on the Python side. However, you can't register the type two times independently since it would cause various inconsistencies in Python-internal data structures.

[SanPen]

I'll add a comment because it might be useful for future viewers.

The generic type error might occur also if the same object is registered by two separated pybind11 modules.

In my case I have two libraries that both need to wrap the Tabulate library. Even if internally I wrap the tabulate library with different object types, the error still persists.

[kliegeois]

@SanPen I am facing the same issue; how have you resolved this?

[SanPen]

Hi! yes I solved it by adding py::module_local() to the class definition

example:

py::class_<Zone, Device, std::shared_ptr<Zone>>(m, "Zone", py::module_local())
.def(py::init<std::string,
                           std::string,
                           std::string,
                           uword>(),
                  py::arg("uuid"),
                  py::arg("secondary_id"),
                  py::arg("name"),
                  py::arg("time_steps"))
            .def_property("area", &Zone::getArea, &Zone::setArea, "Area object to which this zone belongs to. It may be null.")
            ;

This is somewhere in the docs and should be in every example!

[kliegeois]

Thanks a lot @SanPen !