virtualenv is a third-party command-line tool that creates isolated Python environments. Each environment is a directory with its own Python interpreter and `site-packages`, so packages installed in it do not affect the system Python or other environments. virtualenv predates the standard library's venv module and remains the more featureful of the two.

What is the difference between virtualenv and venv?

venv is a module in the Python standard library (added in Python 3.3); virtualenv is a separate package installed from PyPI. Both create isolated Python environments with the same general layout, but virtualenv is faster (it caches and reuses seed packages instead of bootstrapping pip on every create), supports more Python interpreters, including Python 2 and PyPy, and offers more configuration knobs. venv is enough for most projects on Python 3.3 or later and avoids the extra dependency.

Should I use virtualenv or venv?

For a new project on Python 3.3 or later, prefer venv: it ships with Python, requires no extra install, and covers the standard create-and-activate workflow. Reach for virtualenv when you need its faster environment creation, support for Python 2 or PyPy, or features venv does not expose. For a fully managed workflow, uv creates and manages environments automatically as part of `uv run` and `uv sync`, removing most manual steps either tool requires.

Does virtualenv install Python?

No. virtualenv only creates a new environment that points at an existing Python interpreter; it does not download or install Python itself. Use a tool like pyenv or uv to install Python versions, then use virtualenv (or venv) to create environments that target them.

virtualenv: Python Virtual Environment Tool

by Tim Hopper · Markdown

Virtual Environments

virtualenv creates isolated Python virtual environments. Each environment is a self-contained directory with its own interpreter and site-packages, so installed packages never affect the system Python or other projects. virtualenv predates the standard library’s venv module and remains faster and more configurable.

When to use virtualenv

virtualenv fits projects that need its faster environment creation through cached seed packages, or support for Python 2, PyPy, and other interpreters that venv does not cover. Most modern projects on Python 3.3 or later can use venv, which ships in the standard library without an extra dependency. For new work, uv creates and manages virtual environments automatically as part of uv run and uv sync, removing the manual create-and-activate steps virtualenv requires. virtualenv does not install Python itself; use pyenv or uv for that.

Key Features

Creates isolated environments with their own site-packages, preventing dependency conflicts between projects
Faster environment creation than venv by caching seed packages (pip, setuptools, wheel) instead of bootstrapping them fresh each time
Supports Python 2, PyPy, and other interpreters that venv does not
Automatically installs pip into each new environment
Activation scripts for bash, zsh, fish, and PowerShell

Pros

Faster environment creation than the built-in venv through seed package caching
Broader interpreter support, including Python 2 and PyPy
Stable, with a long-running plugin ecosystem

Cons

Manual environment activation required; no equivalent to uv run
No dependency locking or Python version management (use pip-tools or uv for those)
Requires a separate install; not part of the standard library

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Last updated on June 12, 2026

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