Transition your Python project to use pyproject.toml and setup.cfg! (An example.)

Thanks to Luiz Irber for all the pre-work on sourmash, as well as the code reviews on screed; and Brett Cannon for a review of an earlier version of this blog post!

The future of Python packaging is pyproject.toml, and (for now) setup.cfg, based on PEP 518 and (soon) PEP 621.

For some background, please read "What the heck is pyproject.toml", and also Where to get started with pyproject.toml?

The relevant setuptools docs have been updated to reflect the new toolchain, too!

My takeaway from all of this is:

  • configuration files are better than scripts
  • a few standard configuration files are better than many
  • declarative/static is better than procedural/dynamic

OK! rubs hands with glee let's do this!

"But what do I actually do?"

Brett's post is pretty excellent and was really informative for me, but I have a high tolerance for reading lots of text! It's probably a bit long for people who just want to update their project, though ;).

So I decided to give it a try myself and then post an example!

Recently, I wanted to release a new version of screed, in order to get rid of some DeprecationWarnings for the release of sourmash 4.0. Now, screed is a remarkably ...stable project, by which I mean it does the thing we need it to do and no more, and we're not changing it at all.

BUT. Screed was based on an old school So, inspired by Luiz Irber's updating of sourmash to use pyproject.toml, I updated screed similarly. (It was REALLY helpful to have an example!)


Here is the diff.

In brief,

  • your pyproject.toml can be very close to boilerplate.
    • It's basically the three lines that Brett posted...
    • the additional stuff for screed has to do with setuptools_scm, which we're using to automatically convert git tags like v1.0.4 into actual version numbers.
  • your setup.cfg basically contains almost everything your contained, just a bit reformatted to fit into the setup.cfg format.
  • your new can now be a really short stub to permit python ... to continue to work.

I hope this helps! Comment and ask questions as you have them!

(Also: I just released screed v1.0.5! :tada:)


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