venv & pip

beginner10 min readLesson 42 of 169

Create, activate, install — and pin versions with requirements.txt.

pip is the installer; PyPI (pypi.org) is the public package catalog it downloads from.

pip install rich            # latest version
pip install "requests==2.31.0"   # exact version — reproducible
pip list                    # what is installed here

requirements.txt — your project's recipe

rich==13.7.1
requests==2.31.0

Freeze what you installed:

pip freeze > requirements.txt

Rebuild the environment anywhere (a teammate's laptop, a server):

python3 -m venv .venv
source .venv/bin/activate
pip install -r requirements.txt

Version pins are a kindness to your future self and your teammates: "it works on my machine" becomes "here is the exact recipe that works."