Jupyter Notebook running pybind11 program

This document demonstrates how to run pybind11 programs in Jupyter notebook in the most simple way using Xeus-Cling kernel. Sample programs here include:

• simple Hello world program
• embedded module via PYBIND11_EMBEDDED_MODULE macro

Setup

conda install -c conda-forge xeus-cling
conda install -c conda-forge pybind11
conda install -c conda-forge notebook

Simple program

The code

#pragma cling add_include_path("/home/jupyter/miniconda3/include/python3.9/")
#pragma cling add_library_path("/home/jupyter/miniconda3/lib")
#pragma cling load("python3.9")

#include <pybind11/embed.h>
#include <iostream>

namespace py = pybind11;

void py_print(py::object o)
{
    std::cout << py::str(o).cast<std::string>() << "\n";
};

py::scoped_interpreter python;

py::str s{"Hello world"};
py_print(s);

Embedded module

The code

#pragma cling add_include_path("/home/jupyter/miniconda3/include/python3.9/")
#pragma cling add_library_path("/home/jupyter/miniconda3/lib")
#pragma cling load("python3.9")

#include <pybind11/embed.h>
#include <iostream>

namespace py = pybind11;

void py_print(py::object o)
{
    std::cout << py::str(o).cast<std::string>() << "\n";
};

PYBIND11_EMBEDDED_MODULE(hello, m)
{
    m.def("world", []() { return "Hello world"; });
}

py::scoped_interpreter python;

py_print(py::module::import("hello").attr("world")());

Remarks

• The buildin function py::print() prints into the terminal where you're running jupyter notebook, hence using custom py_print(). Suggestions how to redirect output of py::print() into the notebook are welcomed.
• Exception handling with catch(const py::error_already_set& e) sometimes works, sometimes not. Suggestions how to fix that are welcomed.
• The compiler seems to compile in Release mode. Enabling Debug mode would be beneficial, but how?

Links

• pybind11 docs
• pybind11 repo