Creating Virtual Environments

Christian Külker

0.1.2

2023-03-04

The virtualenv utility uses the command line path environment variable to create isolated Python virtual environments, similar to venv. Compared to venv, virtualenv provides additional functionality by supporting Python 2.7 and providing convenient features for configuring, maintaining, duplicating, and debugging the virtual environments.

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

There are currently two popular 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 to manage multiple virtual environments. The pyvenv virtual environment creation tool recommended for Python 3.3 and 3.4 is deprecated in Python 3.6. The use of venv is recommended for creating virtual environments in Python 3.5 and later.

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 want to manage and use virtual environments in Perl: (1) Some conflicting Perl modules. (2) A controlled environment. While I have encountered (2) more than once, I have never encountered (1) in the last 25 years. While I think it is possible, it rarely seems to be an issue, as modules in Perl tend to upgrade quite smoothly. Since my experience with Python is less long, I wonder why virtual environments are suggested so often.

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
0.1.2 2023-03-04 Improve writing
0.1.1 2022-07-12 History, shell->bash
0.1.0 2020-05-16 Initial release
  • Creating Virtual Environments