How to use Python virtual environments?

Install Virtualenvwrapper.

Here’s how I install it on Mac:

PIP_REQUIRE_VIRTUALENV=false pip3 install --user --upgrade virtualenvwrapper

Add the following to your startup script (e.g. ~/.zshenv, ~/.bashrc):

export PIP_REQUIRE_VIRTUALENV=true
export WORKON_HOME=~/.virtualenvs
export VIRTUALENVWRAPPER_PYTHON=/opt/local/bin/python3.8
export VIRTUALENVWRAPPER_VIRTUALENV=~/Library/Python/3.8/bin/virtualenv
source ~/Library/Python/3.8/bin/virtualenvwrapper.sh

Source your startup script to bring the changes into your environment:

source ~/.zshenv

Usage

The main two commands you need are mkvirtualenv and workon.

To create a virtualenv:

mkvirtualenv -p $(which python3.6) my_virtualenv

It’s important to specify the specific Python version to use for your specific project. Install multiple versions of Python into your system to use for different projects.

The virtualenv is created and activated. You can install packages into it with pip install.

After creating the env, always follow with setvirtualenvproject, which tells the virtualenv to change into the current directory next time you work on this project.

setvirtualenvproject

Next time you want to work on the project:

workon my_virtualenv

To delete the virtualenv (must be inactive):

deactivate
rmvirtualenv my_virtualenv