Mention py_modules in "Package Discovery and Namespace Package"?

[kinow]

Hi,

I started using pyproject.toml and setup.cfg today after a colleague told me about it.

I had an AWS Lambda script that I also run locally, in a repository with requirements.txt files and the app.py single script. Instead of migrating to setup.py, I went straight to pyproject.toml and tried to use the Package Discovery and Namespace Package docs, specifically the section “single-module distribution”.

Its description matches, I think, exactly my case,

A standalone module is placed directly under the project root, instead of inside a package folder:

I tried first without anything, letting the build tools to try to find my app.py (right next to pyproject.toml and setup.cfg), but that didn't work (it failed to include the app.py` in the produced sdist file).

After some googling, I found that this fixed the issue for me:

[options]
py_modules =
    app

Is it something that would be worth an example for that in the “Package Discovery and Namespace Package” page? I found examples for src-layout, for the flat-layout, but the variation of a single module project appears to need py_modules, which may not be intuitive I guess.

Thanks!
Bruno

[abravalheri]

Hi @kinow, thanks for reaching out.

Would you like to propose a change in the docs to target this concern? We are always welcoming PRs :)

I tried first without anything, letting the build tools to try to find my app.py

This seems to be a bit off... The app.py module should be picked up, unless you are already setting packages...

For example:

cd /tmp
rm -rf /tmp/myproj
mkdir /tmp/myproj
touch /tmp/myproj/app.py
cat <<EOS > /tmp/myproj/pyproject.toml
[build-system]
requires = ['setuptools>=62.1.0']
build-backend = 'setuptools.build_meta'

[project]
name = "myproj"
version = "42"
EOS
pip-run build -- -m build /tmp/myproj
unzip -l /tmp/myproj/dist/*.whl

Should give us:

Successfully built myproj-42.tar.gz and myproj-42-py3-none-any.whl
Archive:  /tmp/myproj/dist/myproj-42-py3-none-any.whl
  Length      Date    Time    Name
---------  ---------- -----   ----
        0  2022-04-27 10:42   app.py
      109  2022-04-27 10:43   myproj-42.dist-info/METADATA
       92  2022-04-27 10:43   myproj-42.dist-info/WHEEL
        4  2022-04-27 10:43   myproj-42.dist-info/top_level.txt
      340  2022-04-27 10:43   myproj-42.dist-info/RECORD
---------                     -------
      545                     5 files

[kinow]

That worked! That's funny, I thought I had tested without the packages but I left this part:

package_dir =
    =.*

Removing that, and also the py_modules` fixed it.

But there's something else (sorry if I'm digressing). I created a tiny project to test it, using my other project and your example as reference, to compare the settings. I've put the contents in this gist: https://gist.github.com/kinow/037ea9c5175d715942532b2a801da1c5

I was getting a ModuleNotFoundError: app every time I tried python -m build. That package_dir is invalid, and supposed to raise an error, which it does, but only when I don't reference app.py in the [metadata]version. See comment in the gist.

I think if it raised the same error in both cases, that would make more sense. I also had a [options.entry_points], which I thought was causing the ModuleNotFoundError, but only found it was the version after slowly adding items using your example. Not sure if it's a bug, or expected behavior.

Would you like to propose a change in the docs to target this concern? We are always welcoming PRs :)

That's what I thought would be nice to have, but now since the automatic configuration works, as long as you don't have packages nor package_dir, I'm not sure if that's necessary.

Thanks a lot @abravalheri !
Bruno