Virtual environments in Python

This page described how to use virtual environments in Python.

Why use virtual environments?

Virtual environments allows one to have independent Python environments.

This allows one to have multiple projects

• You can install specific, also older, versions into them
• You can create one for each project and no problem if the two projects require different versions
• If you make some mistake and install something you did not want or need, you can remove the environment and create a new one

Environment managers

Here is an incomplete overview of virtual environment managers that work with Python:

Virtual environment manager	Description
venv	Works on Rackham
virtualenv	venv for older Python versions
conda	Works on Rackham, recommended on Bianca
pyenv	More advanced than venv

General virtual environment manager workflow

flowchart TD
  create[Create]
  activate[Activate]
  use[Use]
  deactivate[Deactivate]

  create --> activate
  activate --> use
  use --> deactivate
  deactivate --> activate

Whatever virtual environment manager you use, this is the workflow:

• You create the isolated environment
• You activate the environment
• You work in the isolated environment. Here you install (or update) the environment with the packages you need
• You deactivate the environment after use

A virtual environment can be created in multiple ways, for example, from scratch. However, there are more efficient ways, such as by re-using already installed Python packages. How to do so, can be found on the page about your specific virtual environment manager.