Thomas is well know as one of the maintainer of IPython and Jupyter, and developed flit while working on the pep for pyproject.toml and the pip backend allowing things like python -m build.

Though `python -m build` only works _if_ you use something like flit or setup.py in the backend to do build the package and hence why you can set flit as a build-backend.

So yes, flit is one of the latest tool, and yes it is one of the things that push for the ability to use pyproject.toml+python3 -m build, you just seem to miss some subtleties of the toolchain.

The additional context is appreciated— it sounds like this tool is something which is likely to be supported long term, so that at least is good.

How does flit compare to poetry? The seem to be both doing the same thing, and in a very similar way.

Poetry does much more than Flit, like resolving dependencies, creating a lock file, and managing an environment where you can run your code. In particular, Poetry is meant to support application development (where you want to have a fixed version of your dependencies) as well as library development.

Flit is more aimed at being the simplest possible thing to put a package on PyPI, if that's all you want to do. It expects you to list dependencies in pyproject.toml manually.

I feel like this is a good place to mention Pip-tools [0] which can generate a lockfile of sorts from a standard requirements.txt (or a setup.py). Specifically, it resolves all dependencies (including hashes), and writes them to a new "requirements" file that you can read with the usual `pip install -r`.

The nice part about Pip-tools versus Flit or Poetry or Pipenv is that Pip-tools lets you keep using Setuptools if you want to, or if you're unable to switch to one of the others for some reason (and valid reasons do exist).

[0]: https://pypi.org/project/pip-tools

Flit is definitely opinionated, and not suitable for every use case. As Carreau hinted, I think its bigger impact will be from the specifications, especially PEP 517, which it helped to prompt, rather than people using Flit directly. The specifications mean it's practical to make new tools which interoperate nicely, without having to either wrap setuptools or carefully imitate its behaviour.

The PyPA recommendation is old and out of date. Using a system that doesn't manage constraints and hash-checked lockfiles is bad practice.