NanoBind Minimal Example

A minimal example of wrapping c++ code with python using NanoBind. The python project shall only use pyproject.toml and will use scikit-build-core as a build system.

The example should cover the following:

• Minimal C++ code example
• Minimal Python wrapper example using NanoBind
• Minimal pyproject.toml file
• Minimal CMakeLists.txt file
• Build system using scikit-build-core
• Build and test code in a mambabuild package compilation (so that it can easily be uploaded to conda)

Installing Development Setup

First install the pre-requisites for nanobind and scikit-build-core build requirements from conda-forge.

mamba env update -f environment.build.yml --prune

If you are using CLION and want to get type hints from the c++ packages in your conda environment, I recommend creating a batch files to set the environment variables and use that as an environment file. See Build, Execution, Deployment > Toolchains -> Add Environment -> Environment file.

Here is an example of a setup.bat file that I use to set the environment variables for CLION.

@echo off

:: mamba env update -f environment.build.yml --prune
:: mamba activate nano-min

set MY_PY_VER=311
set PREFIX=c:/mambaforge/envs/nano-min
set LIBRARY_PREFIX=%PREFIX%/Library
set CMAKE_PREFIX_PATH=%PREFIX%;%LIBRARY_PREFIX%/include;%LIBRARY_PREFIX%/lib;%LIBRARY_PREFIX%/bin

set OpenCASCADE_DIR=%LIBRARY_PREFIX%/lib/cmake/opencascade
set OpenCASCADE_INCLUDE_DIR=%LIBRARY_PREFIX%/include/opencascade

set PYTHON_EXECUTABLE=%PREFIX%/python.exe
set PYTHON_LIBRARY=%PREFIX%/libs/python%MY_PY_VER%.lib

Now you are ready to write some c++ code and wrap it with python.

Locally compile the python package

Open a terminal and navigate to the root directory. Activate the nano-min environment (ie. mamba activate nano-min) and install the package using the following command.

pip install --no-build-isolation . -v

This will install the package into the nano-min environment and you can use it as you would any other python package.

import my_ext

res = ext.add(1, 2)
print(res)

Conda Build install

Open a terminal and navigate to the root directory. Activate the nano-min environment (ie. mamba activate nano-min) and compile the conda package using the following command.

mamba mambabuild conda -c conda-forge --python 3.11 --override-channels
mamba install --use-local nano-min

Notes

• If the python stubs are not updated in your IDE during development try uninstalling and reinstalling the package.