https://github.com/tox-dev/tox-uv
Use https://github.com/astral-sh/uv with tox
https://github.com/tox-dev/tox-uv
tox
Last synced: 16 days ago
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Use https://github.com/astral-sh/uv with tox
- Host: GitHub
- URL: https://github.com/tox-dev/tox-uv
- Owner: tox-dev
- License: mit
- Created: 2024-02-16T06:37:58.000Z (about 2 years ago)
- Default Branch: main
- Last Pushed: 2026-02-12T04:19:49.000Z (2 months ago)
- Last Synced: 2026-02-12T14:15:02.619Z (2 months ago)
- Topics: tox
- Language: Python
- Homepage:
- Size: 276 KB
- Stars: 325
- Watchers: 2
- Forks: 33
- Open Issues: 12
-
Metadata Files:
- Readme: README.md
- Funding: .github/FUNDING.yaml
- License: LICENSE
- Codeowners: .github/CODEOWNERS
- Security: .github/SECURITY.md
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README
# tox-uv
[](https://badge.fury.io/py/tox-uv)
[](https://pypi.python.org/pypi/tox-uv/)
[](https://github.com/tox-dev/tox-uv/actions/workflows/check.yaml)
[](https://pepy.tech/project/tox-uv)
**tox-uv** is a `tox` plugin, which replaces `virtualenv` and pip with `uv` in your `tox` environments. Note that you
will get both the benefits (performance) or downsides (bugs) of `uv`.
- [How to use](#how-to-use)
- [Installation options](#installation-options)
- [uv discovery](#uv-discovery)
- [tox environment types provided](#tox-environment-types-provided)
- [PEP 723 inline script metadata](#pep-723-inline-script-metadata)
- [uv.lock support](#uvlock-support)
- [package](#package)
- [extras](#extras)
- [no_default_groups](#no_default_groups)
- [dependency_groups](#dependency_groups)
- [only_groups](#only_groups)
- [uv_sync_flags](#uv_sync_flags)
- [uv_sync_locked](#uv_sync_locked)
- [External package support](#external-package-support)
- [Environment creation](#environment-creation)
- [uv_seed](#uv_seed)
- [uv_python_preference](#uv_python_preference)
- [Package installation](#package-installation)
- [uv_resolution](#uv_resolution)
## How to use
Install `tox-uv` into the environment of your tox, and it will replace `virtualenv` and `pip` for all runs:
```bash
uv tool install tox --with tox-uv # use uv to install
tox --version # validate you are using the installed tox
tox r -e py312 # will use uv
tox --runner virtualenv r -e py312 # will use virtualenv+pip
```
### Installation options
`tox-uv` is distributed as two packages:
- **`tox-uv`** (recommended): Meta package that includes both the plugin and a bundled `uv` binary. This ensures `uv` is
always available and provides the best out-of-box experience.
- **`tox-uv-bare`**: Plugin-only package without the bundled `uv` binary. Use this in containerized environments
(Docker, Kubernetes) where `uv` is pre-installed in the system to avoid downloading duplicate binaries.
Example Docker usage with `tox-uv-bare`:
```dockerfile
FROM python:3.12
RUN pip install uv tox tox-uv-bare
# uv is already in the container, no need to bundle it again
```
### uv discovery
`tox-uv` discovers the `uv` binary in the following order:
1. **`TOX_UV_PATH` environment variable**: Explicitly specify the `uv` binary location. Useful for testing custom `uv`
builds or when `uv` is installed in a non-standard location.
```bash
export TOX_UV_PATH=/custom/path/to/uv
tox r
```
1. **Bundled `uv`** (when using `tox-uv` meta package): Uses the `uv` binary included with the `tox-uv` package.
1. **System `uv`** (when using `tox-uv-bare` or if bundled `uv` not found): Searches for `uv` in your system `PATH`.
If `uv` cannot be found, `tox-uv` will raise an error with installation instructions.
## tox environment types provided
This package will provide the following new tox environments:
- `uv-venv-runner` is the ID for the tox environments [runner](https://tox.wiki/en/4.12.1/config.html#runner) for
environments not using a lock file.
- `uv-venv-lock-runner` is the ID for the tox environments [runner](https://tox.wiki/en/4.12.1/config.html#runner) for
environments using `uv.lock` (note we can’t detect the presence of the `uv.lock` file to enable this because that
would break environments not using the lock file - such as your linter).
- `uv-venv-pep-723` is the ID for the [PEP 723](https://peps.python.org/pep-0723/) inline script metadata runner. When
`tox-uv` is installed, `virtualenv-pep-723` is also transparently backed by uv.
- `uv-venv-pep-517` is the ID for the PEP-517 packaging environment.
- `uv-venv-cmd-builder` is the ID for the external cmd builder.
## PEP 723 inline script metadata
[PEP 723](https://peps.python.org/pep-0723/) lets Python scripts declare their dependencies and required Python version
inline via comment blocks.
Given a script `tools/check.py`:
```python
# /// script
# requires-python = ">=3.12"
# dependencies = ["requests>=2.31", "rich"]
# ///
import requests
from rich import print
print(requests.get("https://httpbin.org/get").json())
```
Configure tox to run it:
```ini
[testenv:check]
runner = virtualenv-pep-723
script = tools/check.py
```
When `tox-uv` is installed, `virtualenv-pep-723` is transparently backed by uv. You can also use
`runner = uv-venv-pep-723` to explicitly request the uv-backed runner regardless of plugin installation.
To disable the automatic promotion and use tox's built-in virtualenv+pip implementation, set `TOX_UV_NO_PEP723=1`.
Run with `tox r -e check`. Positional arguments are forwarded: `tox r -e check -- --verbose`.
To override the default command (which runs the script), set `commands` as usual:
```ini
[testenv:check]
runner = virtualenv-pep-723
script = tools/check.py
commands = python -m pytest tests/
```
## uv.lock support
If you want for a tox environment to use `uv sync` with a `uv.lock` file you need to change for that tox environment the
`runner` to `uv-venv-lock-runner`. Furthermore, should in such environments you use the `extras` config to instruct `uv`
to install the specified extras, for example (this example is for the `tox.ini`, for other formats see the documentation
[here](https://tox.wiki/en/latest/config.html#discovery-and-file-types)):
```ini
[testenv:fix]
description = run code formatter and linter (auto-fix)
skip_install = true
deps =
pre-commit-uv>=4.1.1
commands =
pre-commit run --all-files --show-diff-on-failure
[testenv:type]
runner = uv-venv-lock-runner
description = run type checker via mypy
commands =
mypy {posargs:src}
[testenv:dev]
runner = uv-venv-lock-runner
description = dev environment
extras =
dev
test
type
commands =
uv pip tree
```
In this example:
- `fix` will use the `uv-venv-runner` and use `uv pip install` to install dependencies to the environment.
- `type` will use the `uv-venv-lock-runner` and use `uv sync` to install dependencies to the environment without any
extra group.
- `dev` will use the `uv-venv-lock-runner` and use `uv sync` to install dependencies to the environment with the `dev`,
`test` and `type` extra groups.
Note that when using `uv-venv-lock-runner`, _all_ dependencies will come from the lock file, controlled by `extras`.
Therefore, options like `deps` are ignored (and all others
[enumerated here](https://tox.wiki/en/stable/config.html#python-run) as Python run flags).
### `package`
How to install the source tree package, must be one of:
- `skip` - do not install the project,
- `wheel` - install the project as a non-editable wheel,
- `editable` (default) - install the project in editable mode,
- `uv` - with `uv-venv-runner` uses uv directly to install the project (bypassing tox's PEP-517 packaging), with
`uv-venv-lock-runner` behaves like `wheel`,
- `uv-editable` - with `uv-venv-runner` uses uv directly to install in editable mode (bypassing tox's PEP-517
packaging), with `uv-venv-lock-runner` behaves like `editable`.
With `uv-venv-runner`, prefer `uv`/`uv-editable` when you need non-standard features of `uv`, such as `tool.uv.sources`.
With `uv-venv-lock-runner`, `uv sync` already handles installation natively so all modes work through it.
### `extras`
A list of string that selects, which extra groups you want to install with `uv sync`. By default, it is empty.
### `no_default_groups`
A boolean flag to toggle installation of the `uv`
[default development groups](https://docs.astral.sh/uv/concepts/projects/dependencies/#default-groups). By default, it
will be `true` if the `dependency_groups` is not empty and `false` otherwise.
### `dependency_groups`
Specify [PEP 735 – Dependency Groups](https://peps.python.org/pep-0735/) to install **in addition to** the project and
its dependencies (maps to `uv sync --group`). For example, `dependency_groups = ["test", "docs"]` installs the project,
its default dependencies, and the `test` and `docs` groups.
### `only_groups`
Install **only** these [PEP 735 – Dependency Groups](https://peps.python.org/pep-0735/), excluding the project and all
other dependencies (maps to `uv sync --only-group`). Use this when you need a dependency group in complete isolation,
such as CI tooling from a private index. For example, `only_groups = ["ci"]` installs only the `ci` group without the
project or any of its dependencies.
**Key difference**: `dependency_groups` adds groups to the standard install, while `only_groups` replaces the entire
install with just those groups.
### `uv_sync_flags`
A list of strings, containing additional flags to pass to uv sync (useful because some flags are not configurable via
environment variables). For example, if you want to install the package in non editable mode and keep extra packages
installed into the environment you can do:
```ini
uv_sync_flags = --no-editable, --inexact
```
If `--frozen` is included in `uv_sync_flags`, tox-uv will automatically suppress the implicit `--locked` argument since
the two flags are mutually exclusive in uv:
```ini
uv_sync_flags = --frozen
```
### `uv_sync_locked`
By default tox-uv will call `uv sync` with `--locked` argument, which is incompatible with other arguments like
`--prerelease` or `--upgrade ` that you might want to add to `uv_sync_flags` for some test scenarios. You can set this
to `false` to avoid such conflicts.
If the `UV_FROZEN` environment variable is set to a truthy value, tox-uv will automatically suppress `--locked` and pass
`--frozen` to `uv sync` instead. This is useful in CI environments where the lockfile was created on a different
platform and platform-specific metadata validation should be skipped:
```bash
UV_FROZEN=1 tox
```
### External package support
Should tox be invoked with the [`--installpkg`](https://tox.wiki/en/stable/cli_interface.html#tox-run---installpkg) flag
(the argument **must** be either a wheel or source distribution) the sync operation will run with `--no-install-project`
and `uv pip install` will be used afterward to install the provided package.
## Environment creation
We use `uv venv` to create virtual environments. This process can be configured with the following options:
### `uv_seed`
This flag, set on a tox environment level, controls if the created virtual environment injects `pip`, `setuptools` and
`wheel` into the created virtual environment or not. By default, it is off. You will need to set this if you have a
project that uses the old legacy-editable mode, or your project doesn’t support the `pyproject.toml` powered isolated
build model.
### `uv_python_preference`
This flag, set on a tox environment level, controls how `uv` select the Python interpreter.
By default, `uv` will attempt to use Python versions found on the system and only download managed interpreters when
necessary. However, It is possible to adjust `uv`'s Python version selection preference with the
[python-preference](https://docs.astral.sh/uv/concepts/python-versions/#adjusting-python-version-preferences) option.
### `system_site_packages` (`sitepackages`)
Create virtual environments that also have access to globally installed packages. Note the default value may be
overwritten by the VIRTUALENV_SYSTEM_SITE_PACKAGES environment variable. This flag works the same way as the one from
[tox native virtualenv implementation](https://tox.wiki/en/latest/config.html#system_site_packages).
## Package installation
We use `uv pip` to install packages into the virtual environment. The behavior of this can be configured via the
following options:
### `uv_resolution`
This flag, set on a tox environment level, informs `uv` of the desired [resolution strategy]:
- `highest` - (default) selects the highest version of a package satisfying the constraints.
- `lowest` - install the **lowest** compatible versions for all dependencies, both **direct** and **transitive**.
- `lowest-direct` - opt for the **lowest** compatible versions for all **direct** dependencies, while using the
**latest** compatible versions for all **transitive** dependencies.
This is an `uv` specific feature that may be used as an alternative to frozen constraints for test environments if the
intention is to validate the lower bounds of your dependencies during test executions.
**Note**: When using `uv_resolution` with `dependency_groups`, all dependencies from both `deps` and `dependency_groups`
are combined into a single install operation. This ensures the resolution strategy applies correctly across all
requirements, preventing sequential installations from resolving transitive dependencies before the strategy can apply
to overlapping direct dependencies.
### Cache invalidation for `UV_*` environment variables
tox-uv includes a curated set of `UV_*` environment variables in the install cache key. When any of these variables
change via `set_env`, the cached environment is invalidated and packages are reinstalled so that uv can re-resolve with
the new settings. The tracked variables are:
`UV_CONSTRAINT`, `UV_DEFAULT_INDEX`, `UV_EXCLUDE`, `UV_EXCLUDE_NEWER`, `UV_EXTRA_INDEX_URL`, `UV_FIND_LINKS`,
`UV_FORK_STRATEGY`, `UV_INDEX`, `UV_INDEX_STRATEGY`, `UV_INDEX_URL`, `UV_KEYRING_PROVIDER`, `UV_NO_INDEX`,
`UV_NO_SOURCES`, `UV_OFFLINE`, `UV_OVERRIDE`, `UV_PRERELEASE`, `UV_REQUIRE_HASHES`, `UV_RESOLUTION`, `UV_TORCH_BACKEND`.
Variables that do not affect resolution (e.g. `UV_CONCURRENT_DOWNLOADS`, `UV_NO_PROGRESS`, `UV_CACHE_DIR`) are not
tracked and changing them will not trigger a reinstall.
[resolution strategy]: https://github.com/astral-sh/uv/blob/0.1.20/README.md#resolution-strategy