making python packages the modern way

I’ve not found a place where this is described clearly. You have to make a Python package and then you can import that directly by name.

The command uv init --package octavius will create a package structure containing

octavius/
├── pyproject.toml
└── src
    └── octavius
        └── __init__.py

Then, if you cd octavius and uv sync the package octavius will be installed into your virtualenv.

You have created a package octavius and you can import it directly in your notebooks like:

import octavius

Now, if I create octavius/toys.py with a function lego in it. I could then

from octavius import toys
toys.lego()

or similar.

To create a submodule in octavius/friends just create the directory and put an empty __init__.py to mark it as a module. Then, with octavius/friends/mary.py you could import that with

from octavius.friends import mary
print(f"mary.hobbies()=}")

a big caution

If you are missing a build system in your pyproject.toml you will not be able to import your package. Unfortunately, uv gives no indication that anything is wrong, you will just get an ImportError when you try to import your package.

[build-system]
requires = ["hatchling"]
build-backend = "hatchling.build"

You can confirm that uv has installed your package with

uv pip list | grep octavius