How To Use A Python Virtual Environment (vscode python venv)

See the companion Python venv tutorial deep-dive: Ultimate Python Venv Tutorial and Guide.

Problem

• You need to isolate project-specific Python packages without touching the pip3 system-wide packages of Python.
• You want consistent installs across machines and easy activation in terminals and VS Code.

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Solutions

• Create and activate a new environment.

# POSIX/macOS/Linux
python3 -m venv .venv
source .venv/bin/activate
python -V
python -m pip install --upgrade pip \
  setuptools wheel

• Install dependencies from a file.

python -m pip install -r requirements.txt

• Run a script with unbuffered output and UTF-8.

PYTHONUNBUFFERED=1 PYTHONUTF8=1 python -u your_script.py

• Deactivate and remove the environment.

deactivate
rm -rf .venv/

• Select the interpreter in VS Code.

  • Install the “Python” extension.
  • Press Command Palette → “Python: Select Interpreter” → choose ./.venv.
  • Enable auto-activation for new terminals:

{
  "python.defaultInterpreterPath": "${workspaceFolder}/.venv/bin/python",
  "python.terminal.activateEnvironment": true
}

What is a Python Venv?

A Python virtual environment is a lightweight, built-in tool that creates an isolated interpreter and site-packages directory per project.

How To Activate Python Venv

Let’s go over how to activate a Python venv using shell scripts that prepend .venv/bin to PATH so python and pip resolve inside the environment.

Python Venv Tutorial

Here are the steps from creation to activation, installing packages, running scripts, and deactivation.

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Things To Consider

• Use python3 -m venv .venv to create; use python -m pip ... after activation.
• A venv affects only Python tooling on PATH. You can still use Go, Docker, Node, and Git.
• Recreate the venv after upgrading the Python minor version.
• In VS Code, creating via “Python: Create Environment” also works and pins the workspace.
• Prefer .venv/ at the repo root and add it to .gitignore.

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Gotchas

• Do not execute ./.venv/bin/activate; always source .venv/bin/activate.
• If prints are delayed, use python -u or set PYTHONUNBUFFERED=1.
• Old pins may not support newer Python (e.g., 3.14). Bump versions or set bounds.
• Do not put pip inside requirements.txt; use --upgrade-deps at venv creation or a constraints file.
• In shells with custom prompts, disable Python’s default prompt injection if you add your own.

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Sources

• Official Documentation
• Other Reputable Resource

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Further Investigation

• pyenv or uv for managing multiple Python versions.
• pipx for global-style CLI tools without touching project envs.
• VS Code testing and debugger configs for module vs script entrypoints.

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TL;DR

• Create, activate, install, run, and clean up quickly.

python3 -m venv .venv \
  && source .venv/bin/activate \
  && python -m pip install -r requirements.txt \
  && PYTHONUNBUFFERED=1 python -u your_script.py

• If installs fail, recreate with modern tooling.

rm -rf .venv \
  && python3 -m venv --upgrade-deps .venv \
  && source .venv/bin/activate \
  && python -m pip install -r requirements.txt