Binding `static constexpr` in Python

README.md

Build with:

mkdir build
cd build
cmake ..
make

Then run the python script.

bindings.cc

#include <pybind11/pybind11.h>
#include "constants.h"

namespace py = pybind11;

PYBIND11_MODULE(constexpr_demo, m) {
    // Bind the namespace-level constexpr
    m.attr("ERR_FAIL") = my_namespace::ERR_FAIL;
}

CMakeLists.txt

cmake_minimum_required(VERSION 3.14)
project(constexpr_demo)

# Enable C++17
set(CMAKE_CXX_STANDARD 17)
set(CMAKE_CXX_STANDARD_REQUIRED ON)

# Find pybind11
find_package(pybind11 REQUIRED)

# Create the Python module
pybind11_add_module(constexpr_demo bindings.cc)

constants.h

#pragma once

namespace my_namespace {
  static constexpr int ERR_FAIL = 1;
}

test.py

import sys
import os

# Add the build directory relative to the script location
this_dir = os.path.dirname(os.path.abspath(__file__))
build_dir = os.path.join(this_dir, "build")
sys.path.insert(0, build_dir)

import constexpr_demo

print("Namespace constant:", constexpr_demo.ERR_FAIL)