Using a Custom Build Backend

Oct 13, 2025 by pinkandtrash.com 119 views

Introduction

As a team lead, maintaining a consistent build process across different projects can be a daunting task. With some team members preferring to develop in C++ using CMake and others opting for pure Python, it's essential to find a solution that caters to both needs. In this article, we'll explore how to use Scikit-Build-Core to maintain a unified pyproject.toml file for both C++ and pure Python projects.

The Challenge

When using Scikit-Build-Core, which is designed to work seamlessly with CMake, we encounter an issue when trying to apply it to pure Python projects. The build process complains about the absence of a CMakeLists.txt file, which is a requirement for CMake-based projects. This raises a question: should we create a dummy CMakeLists.txt file for pure Python projects?

Understanding Scikit-Build-Core

Before diving into the solution, let's briefly discuss Scikit-Build-Core. It's a Python package that provides a build backend for projects that use the pyproject.toml file as their build configuration file. Scikit-Build-Core is designed to work with CMake, which is a popular build system for C++ projects. By using Scikit-Build-Core, we can maintain a unified build process across different projects, regardless of the programming language used.

The Dummy CMakeLists.txt Approach

One possible solution to the issue is to create a dummy CMakeLists.txt file for pure Python projects. This file would contain minimal information, such as the project name and version, but would not include any actual build instructions. The idea behind this approach is to satisfy the build backend's requirement for a CMakeLists.txt file while still allowing the project to be built using the pure Python build process.

Creating a Dummy CMakeLists.txt File

If you decide to create a dummy CMakeLists.txt file, here's an example of what it might look like:

cmake_minimum_required(VERSION 3.10)
project(MyPurePythonProject VERSION 1.0.0)

This file contains the minimum required information for a CMake project: the project name and version. However, it does not include any actual build instructions, which means that the build process will not attempt to compile any C++ code.

Using a Custom Build Backend

Another approach to solving the issue is to create a custom build backend that can handle pure Python projects without requiring a CMakeLists.txt file. This would involve creating a custom build-backend section in the pyproject.toml file that specifies the build backend to use for pure Python projects.

Custom Build Backend Example

Here's an example of how you might define a custom build backend in the pyproject.toml file:

[build-system]
requires = ["scikit-build-core"]
build-backend = "scikit_build_core.build_backend"

[build-backend]
name = "pure-python-backend"
description = "Custom build backend for pure Python projects"

[build-backend.pure-python-backend]
build-command = "python setup.py build"

This example defines a custom build backend called pure-python-backend that uses the python setup.py build command to build the project.

Conclusion

In conclusion, while creating a dummy CMakeLists.txt file is a possible solution to the issue, it may not be the most elegant or efficient approach. Creating a custom build backend that can handle pure Python projects without requiring a CMakeLists.txt file is a more robust solution that provides greater flexibility and control over the build process.

Best Practices

When working with Scikit-Build-Core and pure Python projects, here are some best practices to keep in mind:

Use a custom build backend to handle pure Python projects.
Define a build-backend section in the pyproject.toml file that specifies the build backend to use for pure Python projects.
Use a minimal CMakeLists.txt file for C++ projects, containing only the necessary information for the build process.
Avoid using a dummy CMakeLists.txt file for pure Python projects, as it may lead to confusion and errors.

Q: What is Scikit-Build-Core and why do I need it?

A: Scikit-Build-Core is a Python package that provides a build backend for projects that use the pyproject.toml file as their build configuration file. It's designed to work seamlessly with CMake, which is a popular build system for C++ projects. By using Scikit-Build-Core, you can maintain a unified build process across different projects, regardless of the programming language used.

Q: Why do I need a `CMakeLists.txt` file for my pure Python project?

A: The CMakeLists.txt file is a requirement for CMake-based projects. However, when using Scikit-Build-Core, it's not necessary to create a real CMakeLists.txt file for pure Python projects. Instead, you can create a dummy CMakeLists.txt file or use a custom build backend that can handle pure Python projects without requiring a CMakeLists.txt file.

Q: What's the difference between a dummy `CMakeLists.txt` file and a custom build backend?

A: A dummy CMakeLists.txt file is a minimal CMakeLists.txt file that contains only the necessary information for the build process. It's used to satisfy the build backend's requirement for a CMakeLists.txt file. On the other hand, a custom build backend is a separate build backend that can handle pure Python projects without requiring a CMakeLists.txt file. It's a more robust solution that provides greater flexibility and control over the build process.

Q: How do I create a custom build backend?

A: To create a custom build backend, you need to define a build-backend section in the pyproject.toml file that specifies the build backend to use for pure Python projects. You can then define the build backend's configuration in the build-backend section.

Q: What's the best way to handle pure Python projects with Scikit-Build-Core?

A: The best way to handle pure Python projects with Scikit-Build-Core is to use a custom build backend that can handle pure Python projects without requiring a CMakeLists.txt file. This approach provides greater flexibility and control over the build process.

Q: Can I use Scikit-Build-Core with other build systems?

A: Yes, Scikit-Build-Core is designed to be flexible and can work with other build systems. However, it's primarily designed to work with CMake, so you may need to create a custom build backend to use it with other build systems.

Q: How do I troubleshoot issues with Scikit-Build-Core?

A: To troubleshoot issues with Scikit-Build-Core, you can start by checking the build logs for errors. You can also try running the build process with the --verbose flag to get more detailed output. If you're still having issues, you can try searching online for solutions or reaching out to the Scikit-Build-Core community for help.

Q: Is Scikit-Build-Core compatible with other Python packages?

A: Yes, Scikit-Build-Core is designed to be compatible with other Python packages. However, you may need to create a custom build backend to use it with certain packages.

Q: Can I use Scikit-Build-Core with my existing project structure?

A: Yes, Scikit-Build-Core is designed to be flexible and can work with your existing project structure. However, you may need to create a custom build backend to use it with certain project structures.

Q: How do I update Scikit-Build-Core to the latest version?

A: To update Scikit-Build-Core to the latest version, you can run the following command:

pip install --upgrade scikit-build-core

This will update Scikit-Build-Core to the latest version.