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Setl (pronounced like settle) is a simple way to work with PEP 518 projects with Setuptools as the backend.

The interface is strongly influenced by Flit.


The recommended install method is pipx:

pipx install setl

Setl needs to be installed with Python 3.7 or later, but can be used to build projects using older Python with the --python option.

Quickstart for Setuptools Veterans

Aside from the usual Setuptools configurations, you need to create a file pyproject.toml beside, with the following content:

requires = ["setuptools>=43", "wheel"]

Command comparisons to Setuptools:

Setl Setuptools approximation
setl develop develop
setl build egg_info build
setl publish egg_info build sdist bdist_wheel
twine upload

But Why?

The main difference is how build and runtime dependencies are installed.

Traditionally Setuptools projects use setup_requires, but that has various problems and is discouraged in favour of using PEP 518 to specify build time dependencies instead. But Setuptools’s project management commands do not handle PEP 518 declarations, leaving the user to install those build dependencies manually before using Setl commands mimic pip’s build setup before calling their counterparts, so the build environment stays up-to-date.

Similarly, develop installs runtime dependencies with easy_install, instead of pip. It therefore does not respect PEP 518 declarations in those dependencies, and may even fail if one of the dependencies does not support the “legacy mode” build process. setl develop works around this by pip install-ing runtime dependencies before calling develop --no-deps, so dependencies are installed in the modern format.

The rest are more about providing more useful defaults. It is easy to forget to re-build egg-info when you modify metadata, so Setl tries to be helpful. Nowadays people almost always want to build both sdist and wheel, so Setl does it by default. The PyPA recommends against using upload, so Setl bundles Twine for uploading instead. Nothing rocket science.

Next Steps

  • Read the documentation for detailed command descriptions and inner workings.
  • View the source and help contribute to the project.