Virtual environments isolate project packages. Create with python -m venv venv, activate with source venv/bin/activate, and install with pip. Add venv/ to .gitignore and save dependencies with pip freeze.
Virtual Environments
# Create
python3 -m venv venv
# Activate
source venv/bin/activate # Linux/macOS
venv\Scripts\activate # Windows
# Install packages
pip install requests flask
# Save dependencies
pip freeze > requirements.txt
# Install from file
pip install -r requirements.txt
# Deactivate
deactivate