The tool virtualenv uses the command-line path environment variable to create isolated Python Virtual Environments, much as venv does. Compared to venv, virtualenv provides additional functionality by supporting Python 2.7 and by providing convenient features for configuring, maintaining, duplicating, and troubleshooting the virtual environments.

Python Virtual Environments allow Python packages to be installed in an isolated (local) location, rather than being installed globally.

Currently, there are two common tools for creating Python virtual environments:

• venv (Python 3.4+) is part of Python since Python 3.3
• virtualenv (Python 2.7+ and Python 3.3+)

See Pipenv on how to manage multiple virtual environments. The recommended tool pyvenv for creating virtual environments for Python 3.3 and 3.4 is deprecated in Python 3.6. The use of venv is from Python 3.5 recommended for creating virtual environments.

Basic Usage venv

For bash or zsh:

python3 -m venv <DIR>
source <DIR>/bin/activate

For csh or tcsh:

python3 -m venv <DIR>
source <DIR>/bin/activate.csh

Basic Usage virtualenv

virtualenv <DIR>
source <DIR>/bin/activate

Example

Without any other information it sets up a python2 environment

virtualenv /tmp/test-virtualenv
Running virtualenv with interpreter /usr/bin/python2
New python executable in /tmp/test-virtualenv/bin/python2
Also creating executable in /tmp/test-virtualenv/bin/python
Installing setuptools, pkg_resources, pip, wheel...done.
find test-virtualenv |wc -l
1141

Basic Creation venv

python3 -m venv /path/to/new/virtual/environment

A common name for the target directory is .venv.

Example

This creates a horrible long list of files.

python3 -m venv /tmp/test-venv
cd /tmp/test-venv
find|wc -l
448

Excursus On Perl Virtual Environments

Virtual environments are well known in Perl. And there are basically two reasons why you would manage and use Perl virtual environments: (1) Some conflicting Perl modules. (2) A controlled environment. While I came across (2) more than once I actually never experienced (1) in the last 25 years. While I think it is possible, it seems seldom to be an issue as modules tend to upgrade in Perl quite smoothly. As my experience with Python is less long, I am wondering why virtual environments are suggested to be used so many times.

Scope	Python	Perl
Manage Language Versions	pyenv	plenv, plerlbrew
Manage Module Versions	venv, virtualenv	local::lib, carton
Manage Module Installations	pip	cpanminus

History

Version	Date	Notes
0.1.0	2022-07-12	History, shell->bash
0.1.0	2020-05-16	Initial release