Geoffrey Thomas
4879934b20
`PYTHONHOME` isn't automatically cleaned up, so setting it causes it to leak to child processes of Python, e.g., other, unrelated (perhaps not even uv-controlled) Python builds, which breaks them. Never setting it fixes #19080. However, on the implementation of getpath on Python 3.10 and below, leaving `PYTHONHOME` unset and pointing `__PYVENV_LAUNCHER__` at something that isn't a venv or a directly-usable Python installation (for example, pointing it to .local\bin\python3.10.exe) causes Python startup to fail. So we only should be setting it inside a venv, i.e., if the trampoline itself (not the target executable) is in a venv. Presumably this failure on 3.10 is why we started setting PYTHONHOME in the first place. See brief discussion in https://github.com/astral-sh/uv/pull/13531/files#diff-969979506be03e89476feade2edebb4689a9c261f325988d3c7efc5e51de26d1 The putative benefit of setting `__PYVENV_LAUNCHER__` is to force Python's idea of its own path to be the non-resolved junction path (e.g. uv\python\cpython-3.10-..., not uv\python\cpython-3.10.0-...), to help transparent version upgrades. If we don't manually set it to the non-resolved path, there's a risk that Windows will resolve it. However, empirically on Server 2022, Windows does not resolve it. (Also, even if it does get canonicalized, that has a very limited impact on transparent version upgrades, as venvs still list the junction path in pyvenv.cfg and inside the trampoline. The only impact here is that sys.path etc. might end up listing patch-version-specific paths, which would impact some cases where code serializes the full path to something in the stdlib or to sys._base_executable and calls it later. Also, Linux builds of python-build-standalone have been fully canonicalizing this path since December when we patched getpath to look at /proc/self/exe. That new behavior is arguably a bug but this hasn't seemed to cause any practical issues, so it doesn't seem like a real problem to risk Windows perhaps doing the same thing.) Unrelatedly, while we're rebuilding trampolines anyway, link with /DEBUG:NONE to avoid storing the debug directory in the PE file, which should slightly (but not entirely) reduce the amount of binary churn. ## Test Plan Will need to be manually tested, I don't think we have good coverage for this.
uv
An extremely fast Python package and project manager, written in Rust.
Installing Trio's dependencies with a warm cache.
Highlights
- A single tool to replace
pip,pip-tools,pipx,poetry,pyenv,twine,virtualenv, and more. - 10-100x faster than
pip. - Provides comprehensive project management, with a universal lockfile.
- Runs scripts, with support for inline dependency metadata.
- Installs and manages Python versions.
- Runs and installs tools published as Python packages.
- Includes a pip-compatible interface for a performance boost with a familiar CLI.
- Supports Cargo-style workspaces for scalable projects.
- Disk-space efficient, with a global cache for dependency deduplication.
- Installable without Rust or Python via
curlorpip. - Supports macOS, Linux, and Windows.
uv is backed by Astral, the creators of Ruff and ty.
Installation
Install uv with our standalone installers:
# On macOS and Linux.
curl -LsSf https://astral.sh/uv/install.sh | sh
# On Windows.
powershell -ExecutionPolicy ByPass -c "irm https://astral.sh/uv/install.ps1 | iex"
Or, from PyPI:
# With pip.
pip install uv
# Or pipx.
pipx install uv
If installed via the standalone installer, uv can update itself to the latest version:
uv self update
See the installation documentation for details and alternative installation methods.
Documentation
uv's documentation is available at docs.astral.sh/uv.
Additionally, the command line reference documentation can be viewed with uv help.
Features
Projects
uv manages project dependencies and environments, with support for lockfiles, workspaces, and more,
similar to rye or poetry:
$ uv init example
Initialized project `example` at `/home/user/example`
$ cd example
$ uv add ruff
Creating virtual environment at: .venv
Resolved 2 packages in 170ms
Built example @ file:///home/user/example
Prepared 2 packages in 627ms
Installed 2 packages in 1ms
+ example==0.1.0 (from file:///home/user/example)
+ ruff==0.5.0
$ uv run ruff check
All checks passed!
$ uv lock
Resolved 2 packages in 0.33ms
$ uv sync
Resolved 2 packages in 0.70ms
Checked 1 package in 0.02ms
See the project documentation to get started.
uv also supports building and publishing projects, even if they're not managed with uv. See the publish guide to learn more.
Scripts
uv manages dependencies and environments for single-file scripts.
Create a new script and add inline metadata declaring its dependencies:
$ echo 'import requests; print(requests.get("https://astral.sh"))' > example.py
$ uv add --script example.py requests
Updated `example.py`
Then, run the script in an isolated virtual environment:
$ uv run example.py
Reading inline script metadata from: example.py
Installed 5 packages in 12ms
<Response [200]>
See the scripts documentation to get started.
Tools
uv executes and installs command-line tools provided by Python packages, similar to pipx.
Run a tool in an ephemeral environment using uvx (an alias for uv tool run):
$ uvx pycowsay 'hello world!'
Resolved 1 package in 167ms
Installed 1 package in 9ms
+ pycowsay==0.0.0.2
"""
------------
< hello world! >
------------
\ ^__^
\ (oo)\_______
(__)\ )\/\
||----w |
|| ||
Install a tool with uv tool install:
$ uv tool install ruff
Resolved 1 package in 6ms
Installed 1 package in 2ms
+ ruff==0.5.0
Installed 1 executable: ruff
$ ruff --version
ruff 0.5.0
See the tools documentation to get started.
Python versions
uv installs Python and allows quickly switching between versions.
Install multiple Python versions:
$ uv python install 3.12 3.13 3.14
Installed 3 versions in 972ms
+ cpython-3.12.12-macos-aarch64-none (python3.12)
+ cpython-3.13.9-macos-aarch64-none (python3.13)
+ cpython-3.14.0-macos-aarch64-none (python3.14)
Download Python versions as needed:
$ uv venv --python 3.12.0
Using Python 3.12.0
Creating virtual environment at: .venv
Activate with: source .venv/bin/activate
$ uv run --python pypy@3.8 -- python --version
Python 3.8.16 (a9dbdca6fc3286b0addd2240f11d97d8e8de187a, Dec 29 2022, 11:45:30)
[PyPy 7.3.11 with GCC Apple LLVM 13.1.6 (clang-1316.0.21.2.5)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>>>
Use a specific Python version in the current directory:
$ uv python pin 3.11
Pinned `.python-version` to `3.11`
See the Python installation documentation to get started.
The pip interface
uv provides a drop-in replacement for common pip, pip-tools, and virtualenv commands.
uv extends their interfaces with advanced features, such as dependency version overrides, platform-independent resolutions, reproducible resolutions, alternative resolution strategies, and more.
Migrate to uv without changing your existing workflows — and experience a 10-100x speedup — with the
uv pip interface.
Compile requirements into a platform-independent requirements file:
$ uv pip compile requirements.in \
--universal \
--output-file requirements.txt
Resolved 43 packages in 12ms
Create a virtual environment:
$ uv venv
Using Python 3.12.3
Creating virtual environment at: .venv
Activate with: source .venv/bin/activate
Install the locked requirements:
$ uv pip sync requirements.txt
Resolved 43 packages in 11ms
Installed 43 packages in 208ms
+ babel==2.15.0
+ black==24.4.2
+ certifi==2024.7.4
...
See the pip interface documentation to get started.
Contributing
We are passionate about supporting contributors of all levels of experience and would love to see you get involved in the project. See the contributing guide to get started.
FAQ
How do you pronounce uv?
It's pronounced as "you - vee" (/juː viː/)
How should I stylize uv?
Just "uv", please. See the style guide for details.
What platforms does uv support?
See uv's platform support document.
Is uv ready for production?
Yes, uv is stable and widely used in production. See uv's versioning policy document for details.
Acknowledgements
uv's dependency resolver uses PubGrub under the hood. We're grateful to the PubGrub maintainers, especially Jacob Finkelman, for their support.
uv's Git implementation is based on Cargo.
Some of uv's optimizations are inspired by the great work we've seen in pnpm, Orogene, and Bun. We've also learned a lot from Nathaniel J. Smith's Posy and adapted its trampoline for Windows support.
License
uv is licensed under either of
- Apache License, Version 2.0, (LICENSE-APACHE or https://www.apache.org/licenses/LICENSE-2.0)
- MIT license (LICENSE-MIT or https://opensource.org/licenses/MIT)
at your option.
Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in uv by you, as defined in the Apache-2.0 license, shall be dually licensed as above, without any additional terms or conditions.
