Skill: Python3 Virtual Environments (venv)

Purpose

Manage project-local Python 3 virtual environments under .venv with clear, repeatable steps.

When to use

• Any task in a Python project, including running scripts, tests, or tools
• Repos containing pyproject.toml, requirements.txt, setup.py, setup.cfg, Pipfile, poetry.lock, or *.py
• Setting up a fresh Python environment
• Installing or updating dependencies
• Exporting or locking dependencies
• Repairing or recreating a broken environment

Activation guidance

• If a task involves executing Python code or tooling, ensure .venv exists and is activated first.
• If .venv is missing, create it and install dependencies before running the task.

Default conventions

• Environment path: .venv
• Python interpreter: python3
• Dependency file: requirements.txt

Core commands

Create a new environment:

python3 -m venv .venv

Activate (macOS/Linux):

source .venv/bin/activate

Activate (Windows PowerShell):

.venv\Scripts\Activate.ps1

Deactivate:

deactivate

Upgrade pip:

python -m pip install --upgrade pip

Install dependencies:

python -m pip install -r requirements.txt

Freeze dependencies:

python -m pip freeze > requirements.txt

Remove and recreate:

rm -rf .venv
python3 -m venv .venv

Notes

• Always activate the environment before installing or running Python commands.
• Use python -m pip to ensure pip targets the active environment.
• Prefer project-local .venv over global installs.
• If python3 is missing, make sure the user is aware.
• Always attempt to upgrade pip before installing dependencies.