Without virtual environment you share dependencies between projects. This leads to version conflicts and ‘works on my machine’.

venv — Built-in¶

python -m venv .venv source .venv/bin/activate # Linux/Mac .venv\Scripts\activate # Windows pip install -r requirements.txt deactivate

uv — Modern Alternative¶

Installation¶

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

Usage¶

uv venv uv pip install flask uv pip compile requirements.in -o requirements.txt

Best Practices¶

• .venv in .gitignore
• requirements.txt or pyproject.toml
• Lock file (uv.lock, poetry.lock)
• One env per project

Key Takeaway¶

Always use virtual environment. uv is faster than pip, poetry for complex projects.