Python virtual environments

Question

I successfully installed a virtual environment in Ubuntu 22.10 (VirtualBox) by following this excellent tutorial: www.digitalocean.com/community/tutorials/how-to-install-python-3-and-set-up-a-programming-environment-on-ubuntu-22-04. Thank you, Alex. I have two follow up questions:

A clarification, please. The tutorial directs us to cd into the directory created for our virtual environments (here “environments”) and to both create and activate the environment created from this “environments” directory. In other words, we should do our work from within the main “environments” directory, and not from the my_env directory that is created by the python3 -m venv my_env command. Is this correct? I am asking, because I am planning to create a second virtual environment, and to use a different/older version of Ptyhon. Somehow I feel I should be working from within the respective directory created by the venv command, especially since I will have more than one environment.
I am running the Python version 3.10.7, which is the latest update available from the Ubuntu repo. But would need to install a version of Python 3.9 to use in my second virtual environment. Could someone please direct me to a tutorial on how to do that?

Thanks. I have always found the DigitalOcean tutorials comprehensive and well-written.

Bobby · Accepted Answer

Hi there,

You will be working form the directory that you’ve created with the mkdir command.

For example let’s say that you have 2 projects:

Project 1: you will create a new directory called project1 then cd into it and create the venv, python3 -m venv p1_env
Project 2: you will create a new directory called project2 then cd into it and create the venv, python3 -m venv p2_env

For your second question, in order to install Python 3.9 on Ubuntu, you can use the pyenv CLI to install specific Python versions:

https://github.com/pyenv/pyenv#getting-pyenv

Install the required dependencies:

sudo apt-get update sudo apt-get install git curl python3-pip gcc make zlib1g-dev libssl-dev libbz2-dev libreadline-dev libsqlite3-dev

Install pyenv using the official installer:

curl https://pyenv.run | bash

This will download and run the pyenv installer script. It will add the necessary configuration to your shell profile file (e.g. ~/.bashrc) to initialize pyenv on each new terminal session.