uv — Fast Python Package Manager#

What it is#

uv is a Python package installer and resolver written in Rust by Astral (the same team that makes ruff). It is a drop-in replacement for pip, pip-tools, and virtualenv that runs 10–100× faster. It also supports project-level workflows (uv init, uv add, uv run) as an alternative to poetry.

Install#

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

# Windows (PowerShell)
powershell -ExecutionPolicy ByPass -c "irm https://astral.sh/uv/install.ps1 | iex"

# Or via pip (if you already have Python)
pip install uv

Quick example — install packages#

uv pip install requests pandas

Output:

Resolved 7 packages in 312ms
Installed 7 packages in 143ms
 + certifi==2024.2.2
 + charset-normalizer==3.3.2
 + idna==3.7
 + numpy==2.0.0
 + pandas==2.2.2
 + python-dateutil==2.9.0
 + requests==2.32.3

When / why to use it#

• Replacement for pip: faster resolution, better error messages, compatible commands.
• Replacement for virtualenv + pip-tools: uv venv + uv pip compile replace those two tools.
• Replacement for poetry (for many use cases): uv init + uv add + uv run give a poetry-like workflow.

[!TIP] If you’re starting a new project from scratch, uv is the recommended tool in 2026. For existing poetry projects, migration is low-effort but optional.

Common pitfalls#

[!WARNING] uv is not pip — uv pip install installs into the active virtual environment, not the system Python. If no venv is active, uv installs into an auto-created project venv. Run uv venv first to be explicit.

[!WARNING] uv run is not python — uv run script.py uses the project’s venv and can install dependencies on the fly. It is not a direct replacement for python script.py in all contexts.

Virtual environments#

uv venv                     # creates .venv in current directory
uv venv --python 3.12       # specify Python version
source .venv/bin/activate   # activate (Linux/macOS)
.venv\Scripts\activate      # activate (Windows)

Output:

Using CPython 3.12.3
Creating virtual environment at: .venv
Activate with: source .venv/bin/activate

Richer example — project workflow#

# Initialize a new project
uv init myapp
cd myapp

# Add dependencies
uv add fastapi "uvicorn[standard]"
uv add --dev pytest ruff mypy

# Run a script
uv run uvicorn main:app --reload

# Sync dependencies from uv.lock
uv sync

# Show what's installed
uv pip list

Output:

Initialized project `myapp` at `/home/user/myapp`

Resolved 18 packages in 1.2s
Installed 18 packages in 380ms
 + annotated-types==0.7.0
 + anyio==4.4.0
 + fastapi==0.111.1
 + uvicorn==0.30.1
 + ...

INFO:     Started server process [12345]
INFO:     Uvicorn running on http://127.0.0.1:8000 (Press CTRL+C to quit)

Drop-in pip commands#

uv pip install <pkg>                  # install
uv pip install -r requirements.txt    # from file
uv pip install -e .                   # editable install
uv pip uninstall <pkg>
uv pip list
uv pip freeze > requirements.txt
uv pip compile requirements.in        # pin transitive deps → requirements.txt

Install Python versions#

uv can download and manage Python interpreters:

uv python install 3.12
uv python install 3.13
uv python list            # show available versions

Output:

Installed Python 3.12.3 in 8.4s
 + cpython-3.12.3-linux-x86_64-gnu

uv vs pip vs poetry#