Python: pip, venv, uv

Virtual environments, installing packages, requirements, uv, handy one-liners.

Virtual environments

Create a virtual environment

python3 -m venv .venv

Activate it

source .venv/bin/activate

Windows: .venv\Scripts\activate · leave with deactivate

Which Python is used

which python && python --version

Install a package

pip install <package>

Install from requirements.txt

pip install -r requirements.txt

Freeze installed packages

pip freeze > requirements.txt

Install the current project in editable mode

pip install -e .

Outdated packages

pip list --outdated

Package info and dependencies

pip show <package>

New project

uv init <project>

Add a dependency

uv add <package>

Install everything from the lockfile

uv sync

Run a command in the project environment

uv run <script>.py

Run a CLI tool without installing

uvx <tool>

Install a specific Python versionadvanced

uv python install 3.13

Serve the current directory over HTTP

python3 -m http.server 8000

Pretty-print JSON

python3 -m json.tool <file>.json

Profile a scriptadvanced

python3 -m cProfile -s cumtime <script>.py

Start the debugger at a crashadvanced

python3 -m pdb -c continue <script>.py

Run tests (pytest), stop at the first failure

pytest -x -q