Una

TLDR:

• uv is the best way to use Python, and it has some monorepo/workspace support.
• If your build artifacts are Dockerfiles, uv is probably enough. See an example at carderne/postmodern-mono.
• But if you want to build Python wheels (or similar) in monorepos, read on!

Easy monorepos with Python and uv

Una is a tool to build and productionise Python monorepos with uv.

uv has Workspaces, but no ability to build them. This means if you have dependencies between packages in your workspace, there's no good way to distribute or productionise the end result.

Una solves this. No additional configuration is needed: if you have a functional uv Workspace, just add Una. It consists of the following two things:

1. A CLI to ensure that all imports are correctly specified as dependencies (you don't have to use this).
2. A build plugin that enables production builds of individual apps within a monorepo by injecting local dependencies and transitive third-party dependencies.

Una doesn't try to replicate a full build system such as Bazel or Pants. It just makes it possible to have a simple monorepo with interdependencies.

Una works much like a Rust workspace, with each package having its own pyproject.toml. In general, packages should either be libraries (imported but not run) or apps (run but never imported), but Una will not enforce this.

It only works with the Hatch build backend.

Examples

You can see an example repo here:

• una-example

Quickstart

This will give you a quick view of how this all works.

First install uv:

curl -LsSf https://astral.sh/uv/install.sh | sh

And start your workspace:

uv init unarepo   # choose another name if you prefer
cd unarepo
uv add --dev una

Then setup the Una workspace. This will generate a structure and an example lib and app.

uv run una create workspace
uv sync

Have a look at what's been generated:

tree

Have a look at the generated __init__.py files in the apps/printer and libs/greeter packages. An external dependency (cowsay-python) has also been added to the latter's pyproject.toml.

The magic of Una then comes in to resolve the graph of direct and transitive dependencies, which looks like this:

printer --> greeter --> cowsay-python

You can do this by running the following. This checks all imports and ensures they are added to project.dependencies and tool.uv.sources in each pyproject.

uv run una sync

Have a look at what happened:

tail apps/printer/pyproject.toml

It added greeter as an internal dependency to printer. It didn't add cowsay-python, as transitive external dependencies are only resolved at build-time.

Now you can build your app. Note that you must specify the --wheel parameter. Una doesn't currently work for builds that do source -> sdist -> wheel, as these break some things with uv virtual envs.

uvx --from build pyproject-build --installer=uv \
    --outdir=dist --wheel apps/printer

And see the result:

ls dist/

And you can do whatever you want with that wheel! What about stick it in a Dockerfile, have you ever seen such a simple one?

FROM python
COPY dist dist
RUN pip install dist/*.whl

Build it:

docker build --tag unarepo-printer .

And run it:

docker run --rm -it unarepo-printer \
  python -c 'from unarepo.printer import run; run()'

┌────────────────┐
│Hello from una! │
└────────────────┘
               \
                \
                  ^__^
                  (oo)\_______
                  (__)\       )\/\
                      ||----w |
                      ||     ||

You can also get a handy table of your internal inter-dependencies:

┏━━━━━━━━━━━━━━━━━━━┳━━━━━━━━━┳━━━━━━━━━┓
┃ Package \ Imports ┃ printer ┃ greeter ┃
┡━━━━━━━━━━━━━━━━━━━╇━━━━━━━━━╇━━━━━━━━━┩
│           printer │ ✓       │ ✓       │
│           greeter │         │ ✓       │
└───────────────────┴─────────┴─────────┘

Installation

The CLI tool isn't strictly necessary, as all the stuff that lets the monorepo builds work is in the separate (and tiny) hatch-una package. But you will likely struggle to manage your monorepo without the tool!

So you may as well install it:

uv add --dev una

As for the build-time hatch-una, it will automatically be installed by build tools when it spots this in your pyproject.toml (this will be configured automatically by the CLI):

[build-system]
requires = ["hatchling", "hatch-una"]
build-backend = "hatchling.build"

Usage

The CLI has a few commands and options, have a look:

uv run una --help

 Usage: una [OPTIONS] COMMAND [ARGS]...

╭─ Options ─────────────────────────────────────────────╮
│ --help          Show this message and exit.           │
╰───────────────────────────────────────────────────────╯
╭─ Commands ────────────────────────────────────────────╮
│ create   Commands for creating workspace and packages.│
│ sync     Update packages with missing dependencies.   │
╰───────────────────────────────────────────────────────╯

Documentation

Read more at the official documentation.

It covers additional things like:

• type-checking, testing, editor integration
• and more!

Contributing

See the instructions at the official documentation.

Very briefly, local development is with uv:

uv sync
make all  # will fmt, lint, typecheck and test

Then open a PR.

License

Una is distributed under the terms of the MIT license. Some code is from the python-polylith project (c) 2022 David Vujic