UV Package Manager

Comprehensive guide to using uv, an extremely fast Python package installer and resolver written in Rust, for modern Python project management and dependency workflows.

When to Use This Skill

• Setting up new Python projects quickly

• Managing Python dependencies faster than pip

• Creating and managing virtual environments

• Installing Python interpreters

• Resolving dependency conflicts efficiently

• Migrating from pip/pip-tools/poetry

• Speeding up CI/CD pipelines

• Managing monorepo Python projects

• Working with lockfiles for reproducible builds

• Optimizing Docker builds with Python dependencies

Core Concepts

1. What is uv?

• Ultra-fast package installer: 10-100x faster than pip

• Written in Rust: Leverages Rust's performance

• Drop-in pip replacement: Compatible with pip workflows

• Virtual environment manager: Create and manage venvs

• Python installer: Download and manage Python versions

• Resolver: Advanced dependency resolution

• Lockfile support: Reproducible installations

2. Key Features

• Blazing fast installation speeds

• Disk space efficient with global cache

• Compatible with pip, pip-tools, poetry

• Comprehensive dependency resolution

• Cross-platform support (Linux, macOS, Windows)

• No Python required for installation

• Built-in virtual environment support

3. UV vs Traditional Tools

• vs pip: 10-100x faster, better resolver

• vs pip-tools: Faster, simpler, better UX

• vs poetry: Faster, less opinionated, lighter

• vs conda: Faster, Python-focused

Installation

Quick Install

macOS/Linux

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

Windows (PowerShell)

powershell -c "irm https://astral.sh/uv/install.ps1 | iex"

Using pip (if you already have Python)

pip install uv

Using Homebrew (macOS)

brew install uv

Using cargo (if you have Rust)

cargo install --git https://github.com/astral-sh/uv uv

Verify Installation

uv --version

uv 0.x.x

Quick Start

Create a New Project

Create new project with virtual environment

uv init my-project cd my-project

Or create in current directory

uv init .

Initialize creates:

- .python-version (Python version)

- pyproject.toml (project config)

- README.md

- .gitignore

Install Dependencies

Install packages (creates venv if needed)

uv add requests pandas

Install dev dependencies

uv add --dev pytest black ruff

Install from requirements.txt

uv pip install -r requirements.txt

Install from pyproject.toml

uv sync

Virtual Environment Management

Pattern 1: Creating Virtual Environments

Create virtual environment with uv

uv venv

Create with specific Python version

uv venv --python 3.12

Create with custom name

uv venv my-env

Create with system site packages

uv venv --system-site-packages

Specify location

uv venv /path/to/venv

Pattern 2: Activating Virtual Environments

Linux/macOS

source .venv/bin/activate

Windows (Command Prompt)

.venv\Scripts\activate.bat

Windows (PowerShell)

.venv\Scripts\Activate.ps1

Or use uv run (no activation needed)

uv run python script.py uv run pytest

Pattern 3: Using uv run

Run Python script (auto-activates venv)

uv run python app.py

Run installed CLI tool

uv run black . uv run pytest

Run with specific Python version

uv run --python 3.11 python script.py

Pass arguments

uv run python script.py --arg value

Package Management

Pattern 4: Adding Dependencies

Add package (adds to pyproject.toml)

uv add requests

Add with version constraint

uv add "django>=4.0,<5.0"

Add multiple packages

uv add numpy pandas matplotlib

Add dev dependency

uv add --dev pytest pytest-cov

Add optional dependency group

uv add --optional docs sphinx

Add from git

uv add git+https://github.com/user/repo.git

Add from git with specific ref

uv add git+https://github.com/user/repo.git@v1.0.0

Add from local path

uv add ./local-package

Add editable local package

uv add -e ./local-package

Pattern 5: Removing Dependencies

Remove package

uv remove requests

Remove dev dependency

uv remove --dev pytest

Remove multiple packages

uv remove numpy pandas matplotlib

Pattern 6: Upgrading Dependencies

Upgrade specific package

uv add --upgrade requests

Upgrade all packages

uv sync --upgrade

Upgrade package to latest

uv add --upgrade requests

Show what would be upgraded

uv tree --outdated

Pattern 7: Locking Dependencies

Generate uv.lock file

uv lock

Update lock file

uv lock --upgrade

Lock without installing

uv lock --no-install

Lock specific package

uv lock --upgrade-package requests

Python Version Management

Pattern 8: Installing Python Versions

Install Python version

uv python install 3.12

Install multiple versions

uv python install 3.11 3.12 3.13

Install latest version

uv python install

List installed versions

uv python list

Find available versions

uv python list --all-versions

Pattern 9: Setting Python Version

Set Python version for project

uv python pin 3.12

This creates/updates .python-version file

Use specific Python version for command

uv --python 3.11 run python script.py

Create venv with specific version

uv venv --python 3.12

Project Configuration

Pattern 10: pyproject.toml with uv

[project] name = "my-project" version = "0.1.0" description = "My awesome project" readme = "README.md" requires-python = ">=3.8" dependencies = [ "requests>=2.31.0", "pydantic>=2.0.0", "click>=8.1.0", ]

[project.optional-dependencies] dev = [ "pytest>=7.4.0", "pytest-cov>=4.1.0", "black>=23.0.0", "ruff>=0.1.0", "mypy>=1.5.0", ] docs = [ "sphinx>=7.0.0", "sphinx-rtd-theme>=1.3.0", ]

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

[tool.uv] dev-dependencies = [ # Additional dev dependencies managed by uv ]

[tool.uv.sources]

Custom package sources

my-package = { git = "https://github.com/user/repo.git" }

Pattern 11: Using uv with Existing Projects

Migrate from requirements.txt

uv add -r requirements.txt

Migrate from poetry

Already have pyproject.toml, just use:

uv sync

Export to requirements.txt

uv pip freeze > requirements.txt

Export with hashes

uv pip freeze --require-hashes > requirements.txt

Advanced Workflows

Pattern 12: Monorepo Support

Project structure

monorepo/

packages/

package-a/

pyproject.toml

package-b/

pyproject.toml

pyproject.toml (root)

Root pyproject.toml

[tool.uv.workspace] members = ["packages/*"]

Install all workspace packages

uv sync

Add workspace dependency

uv add --path ./packages/package-a

Pattern 13: CI/CD Integration

.github/workflows/test.yml

name: Tests

on: [push, pull_request]

jobs: test: runs-on: ubuntu-latest

steps:
  - uses: actions/checkout@v4

  - name: Install uv
    uses: astral-sh/setup-uv@v2
    with:
      enable-cache: true

  - name: Set up Python
    run: uv python install 3.12

  - name: Install dependencies
    run: uv sync --all-extras --dev

  - name: Run tests
    run: uv run pytest

  - name: Run linting
    run: |
      uv run ruff check .
      uv run black --check .

Pattern 14: Docker Integration

Dockerfile

FROM python:3.12-slim

Install uv

COPY --from=ghcr.io/astral-sh/uv:latest /uv /usr/local/bin/uv

Set working directory

WORKDIR /app

Copy dependency files

COPY pyproject.toml uv.lock ./

Install dependencies

RUN uv sync --frozen --no-dev

Copy application code

COPY . .

Run application

CMD ["uv", "run", "python", "app.py"]

Optimized multi-stage build:

Multi-stage Dockerfile

FROM python:3.12-slim AS builder

Install uv

COPY --from=ghcr.io/astral-sh/uv:latest /uv /usr/local/bin/uv

WORKDIR /app

Install dependencies to venv

COPY pyproject.toml uv.lock ./ RUN uv sync --frozen --no-dev --no-editable

Runtime stage

FROM python:3.12-slim

WORKDIR /app

Copy venv from builder

COPY --from=builder /app/.venv .venv COPY . .

Use venv

ENV PATH="/app/.venv/bin:$PATH"

CMD ["python", "app.py"]

Pattern 15: Lockfile Workflows

Create lockfile (uv.lock)

uv lock

Install from lockfile (exact versions)

uv sync --frozen

Update lockfile without installing

uv lock --no-install

Upgrade specific package in lock

uv lock --upgrade-package requests

Check if lockfile is up to date

uv lock --check

Export lockfile to requirements.txt

uv export --format requirements-txt > requirements.txt

Export with hashes for security

uv export --format requirements-txt --hash > requirements.txt

Performance Optimization

Pattern 16: Using Global Cache

UV automatically uses global cache at:

Linux: ~/.cache/uv

macOS: ~/Library/Caches/uv

Windows: %LOCALAPPDATA%\uv\cache

Clear cache

uv cache clean

Check cache size

uv cache dir

Pattern 17: Parallel Installation

UV installs packages in parallel by default

Control parallelism

uv pip install --jobs 4 package1 package2

No parallel (sequential)

uv pip install --jobs 1 package

Pattern 18: Offline Mode

Install from cache only (no network)

uv pip install --offline package

Sync from lockfile offline

uv sync --frozen --offline

Comparison with Other Tools

uv vs pip

pip

python -m venv .venv source .venv/bin/activate pip install requests pandas numpy

~30 seconds

uv

uv venv uv add requests pandas numpy

~2 seconds (10-15x faster)

uv vs poetry

poetry

poetry init poetry add requests pandas poetry install

~20 seconds

uv

uv init uv add requests pandas uv sync

~3 seconds (6-7x faster)

uv vs pip-tools

pip-tools

pip-compile requirements.in pip-sync requirements.txt

~15 seconds

uv

uv lock uv sync --frozen

~2 seconds (7-8x faster)

Common Workflows

Pattern 19: Starting a New Project

Complete workflow

uv init my-project cd my-project

Set Python version

uv python pin 3.12

Add dependencies

uv add fastapi uvicorn pydantic

Add dev dependencies

uv add --dev pytest black ruff mypy

Create structure

mkdir -p src/my_project tests

Run tests

uv run pytest

Format code

uv run black . uv run ruff check .

Pattern 20: Maintaining Existing Project

Clone repository

git clone https://github.com/user/project.git cd project

Install dependencies (creates venv automatically)

uv sync

Install with dev dependencies

uv sync --all-extras

Update dependencies

uv lock --upgrade

Run application

uv run python app.py

Run tests

uv run pytest

Add new dependency

uv add new-package

Commit updated files

git add pyproject.toml uv.lock git commit -m "Add new-package dependency"

Tool Integration

Pattern 21: Pre-commit Hooks

.pre-commit-config.yaml

repos:

• repo: local hooks:

  • id: uv-lock name: uv lock entry: uv lock language: system pass_filenames: false

  • id: ruff name: ruff entry: uv run ruff check --fix language: system types: [python]

  • id: black name: black entry: uv run black language: system types: [python]

Pattern 22: VS Code Integration

// .vscode/settings.json { "python.defaultInterpreterPath": "${workspaceFolder}/.venv/bin/python", "python.terminal.activateEnvironment": true, "python.testing.pytestEnabled": true, "python.testing.pytestArgs": ["-v"], "python.linting.enabled": true, "python.formatting.provider": "black", "[python]": { "editor.defaultFormatter": "ms-python.black-formatter", "editor.formatOnSave": true } }

Troubleshooting

Common Issues

Issue: uv not found

Solution: Add to PATH or reinstall

echo 'export PATH="$HOME/.cargo/bin:$PATH"' >> ~/.bashrc

Issue: Wrong Python version

Solution: Pin version explicitly

uv python pin 3.12 uv venv --python 3.12

Issue: Dependency conflict

Solution: Check resolution

uv lock --verbose

Issue: Cache issues

Solution: Clear cache

uv cache clean

Issue: Lockfile out of sync

Solution: Regenerate

uv lock --upgrade

Best Practices

Project Setup

• Always use lockfiles for reproducibility

• Pin Python version with .python-version

• Separate dev dependencies from production

• Use uv run instead of activating venv

• Commit uv.lock to version control

• Use --frozen in CI for consistent builds

• Leverage global cache for speed

• Use workspace for monorepos

• Export requirements.txt for compatibility

• Keep uv updated for latest features

Performance Tips

Use frozen installs in CI

uv sync --frozen

Use offline mode when possible

uv sync --offline

Parallel operations (automatic)

uv does this by default

Reuse cache across environments

uv shares cache globally

Use lockfiles to skip resolution

uv sync --frozen # skips resolution

Migration Guide

From pip + requirements.txt

Before

python -m venv .venv source .venv/bin/activate pip install -r requirements.txt

After

uv venv uv pip install -r requirements.txt

Or better:

uv init uv add -r requirements.txt

From Poetry

Before

poetry install poetry add requests

After

uv sync uv add requests

Keep existing pyproject.toml

uv reads [project] and [tool.poetry] sections

From pip-tools

Before

pip-compile requirements.in pip-sync requirements.txt

After

uv lock uv sync --frozen

Command Reference

Essential Commands

Project management

uv init [PATH] # Initialize project uv add PACKAGE # Add dependency uv remove PACKAGE # Remove dependency uv sync # Install dependencies uv lock # Create/update lockfile

Virtual environments

uv venv [PATH] # Create venv uv run COMMAND # Run in venv

Python management

uv python install VERSION # Install Python uv python list # List installed Pythons uv python pin VERSION # Pin Python version

Package installation (pip-compatible)

uv pip install PACKAGE # Install package uv pip uninstall PACKAGE # Uninstall package uv pip freeze # List installed uv pip list # List packages

Utility

uv cache clean # Clear cache uv cache dir # Show cache location uv --version # Show version

Resources

• Official documentation: https://docs.astral.sh/uv/

• GitHub repository: https://github.com/astral-sh/uv

• Astral blog: https://astral.sh/blog

• Migration guides: https://docs.astral.sh/uv/guides/

• Comparison with other tools: https://docs.astral.sh/uv/pip/compatibility/

Best Practices Summary

• Use uv for all new projects - Start with uv init

• Commit lockfiles - Ensure reproducible builds

• Pin Python versions - Use .python-version

• Use uv run - Avoid manual venv activation

• Leverage caching - Let uv manage global cache

• Use --frozen in CI - Exact reproduction

• Keep uv updated - Fast-moving project

• Use workspaces - For monorepo projects

• Export for compatibility - Generate requirements.txt when needed

• Read the docs - uv is feature-rich and evolving