uv plugin¶

See also: Migrate from the Charm plugin to the uv plugin

The uv plugin is designed for Python charms that use uv as the build system and are written with the Operator framework.

Keywords¶

In addition to the common plugin and sources keywords, this plugin provides the following plugin-specific keywords:

uv-extras¶

Type: list of strings

Extra dependencies to build with. Each element of the list is passed exactly as --extra EXTRA.

uv-groups¶

Type: list of strings

Extra dependency groups to build with. Each element of the list is passed exactly as --group GROUP.

python-keep-bins¶

Type: boolean Default: False

Whether to keep Python scripts in the virtual environment’s bin directory.

Environment variables¶

Along with the variables defined by the Python plugin, this plugin responds to its own special variables.

Note

This section describes how this plugin uses uv-specific environment variables. For more information, as well as a complete list of environment variables for uv, see the uv environment documentation.

UV_FROZEN¶

Default value: true

Whether or not to update the uv.lock file. If true, uv.lock must exist and will be used as the single source of truth for dependency versions, with no attempt made to update them before installation.

UV_PROJECT_ENVIRONMENT¶

Default value: See below

A path to the Python virtual environment to build with. By default, this variable populates itself with the directory in which this plugin will create the virtual environment.

UV_PYTHON_DOWNLOADS¶

Default value: “never”

Whether or not to automatically download Python if the requested version is missing.

UV_PYTHON¶

Default value: ${PARTS_PYTHON_INTERPRETER}

The version of Python that uv should use. See Python plugin environment variables for more information.

UV_PYTHON_PREFERENCE¶

Default value: “only-system”

Possible values: only-system, only-managed, system, managed

Whether uv should prefer (or exclusively use) system or uv-managed Python versions.

Dependencies¶

uv must already be installed on the build system in order to use this plugin. For installation instructions, see uv documentation.

How it works¶

During the build step, the plugin performs the following actions:

It creates a virtual environment in the ${CRAFT_PART_INSTALL}/venv directory.
It runs uv sync to install the packages referenced in the pyproject.toml and uv.lock files, along with any optional groups or extras specified.
It copies any existing src and lib directories from your charm project into the final charm.

Example¶

The following project file can be used with a uv project to craft a charm with Ubuntu 24.04 as its base:

name: my-charm
type: charm
title: My uv charm
summary: An operator charm using uv.
description: |
  An operator charm that uses uv for its project.
base: ubuntu@24.04
platforms:
  amd64:
parts:
  my-charm:
    source: .
    plugin: uv