Toolchain: uv, virtual environments, project layout

Every Python project depends on third-party packages. Without isolation, project A needing httpx 0.27 and project B needing 0.28 will conflict the moment you install one on the shared system Python. A virtual environment gives each project its own private set of packages so they can never collide.

uv creates and manages that environment for you, and replaces pip + venv + pip-tools with three commands:

• uv init <name> — scaffold a new project with pyproject.toml
• uv add <package> — add a dependency and install it into .venv
• uv run <command> — run something inside the project’s environment, no manual activation

pyproject.toml declares what your project needs in loose terms (httpx>=0.28). uv.lock pins exact resolved versions for every dependency and sub-dependency. Commit both: the lockfile is what makes an install reproducible for a teammate, CI, or production a month from now.

brew install uv
uv init lesson-01 && cd lesson-01
uv add httpx
uv run lesson-01