Access to SymEngine C++ object from the corresponding Python wrappers [closed]

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I have written a C++ library that depends on SymEngine (https://github.com/symengine/symengine).
This library API offers functions that have parameter and return variables of types of SymEngine, e.g. Symengine::Symbol.

I would like to make the functionality of this library also available in Python.
I would like to do that with pybind11.

SymEngine offers Python wrappers ("import symengine") and they do this via Cython,
see the corresponding git repo https://github.com/symengine/symengine.py.

For my goal I think two crucial steps are:
How can I access the SymEngine C++ objects from the corresponding Python wrappers?
How can I create a SymEngine Python wrapper object to work with in Python from a C++ object?

It is unclear to me where you are stuck at. pybind11 has this example: github.com/pybind/cmake_example/blob/master/src/main.cpp which shows how to export something from c++ to python. Otherwise, can you clarify the issue ? — Avinash Thakur
– Avinash Thakur, Commented Feb 26 at 11:33
@AvinashThakur My problem is rather on the Cython side. I want to have access to the underlying C++ object from the Python wrapper object such that I can use the C++ object in my C++ code. And after that I have to create a Python wrapper object from a SymEngine C++ object that can be used in Python. I tried to clarify my question with an edit. — miguelditoo
– miguelditoo, Commented Feb 26 at 11:46

isuruf · Accepted Answer · 2025-02-26 14:44:02Z

1

This is untested code. There might be a few bugs here.

For accessing the C++ value

auto wrapper = py::module::import("symengine.lib.symengine_wrapper");

RCP<const Basic> python_to_cpp(py::object_ python_object) {
  RCP<const Basic> cpp_object;
  py::object_ capsule = PyCapsule_New(&cpp_object, NULL, NULL);
  wrapper.attr("assign_to_capsule")(capsule, python_object);
  return cpp_object
}

For accessing the python value

auto wrapper = py::module::import("symengine.lib.symengine_wrapper");

py::object_ cpp_to_python(RCP<const Basic>& cpp_object) {
  py::object_ capsule = PyCapsule_New(&cpp_object, NULL, NULL);
  return wrapper.attr("capsule_to_basic")(capsule);
}

answered Feb 26 at 14:44

isuruf

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