The one with a version manager in Python

Python is a programming language that I have worked with several times throughout my career, but, believe it or not, I have never needed to use a version manager that would allow me to handle multiple versions of that language at the same time.

However, I have been using version managers in other languages that I work with more regularly for years, such as RVM for Ruby or NVM for JavaScript.

On my local machine with Ubuntu 22.04 I have Python 3.10.6 installed, but I needed Python 3.9 to run locally with AWS SAM a Lambda function I've been working on lately, as that was the latest version supported by AWS.

Note: Last week AWS Lambda added support for Python 3.10.

Doing a quick research, I found several version managers for Python, such as pythonz and pyflow, but many people considered that the best option was to use pyenv. So that's what I did.

I highly recommend that you read the README of the project as it is very well documented. Anyway, let me explain to you the steps I followed to set up pyenv properly.

Installation

You will need the automatic installer for Linux distributions:

$ curl https://pyenv.run | bash

For other operating systems refer to the installation section of the project.

Shell

Run the following commands in your terminal for ZSH:

$ echo 'export PYENV_ROOT="$HOME/.pyenv"' >> ~/.zshrc
$ echo 'command -v pyenv >/dev/null || export PATH="$PYENV_ROOT/bin:$PATH"' >> ~/.zshrc
$ echo 'eval "$(pyenv init -)"' >> ~/.zshrc

For other shells refer to the shells set up section of the project.

For changes to take effect, run the following command:

$ exec "$SHELL"

Usage

List all available versions in your system

$ pyenv versions
* system (set by /home/david/.pyenv/version)

As you can see, it shows an asterisk next to the currently active version.

Display the currently active version

$ pyenv version
system (set by /home/david/.pyenv/version)

List the all available versions

$ pyenv install --list | less
Available versions:
  2.1.3
  2.2.3
  2.3.7
  ...

Install a new version

Maybe you will need to install Python build dependencies before attempting to install a new Python version.

$ pyenv install 3.9.0
Downloading Python-3.9.0.tar.xz...
-> https://www.python.org/ftp/python/3.9.0/Python-3.9.0.tar.xz
Installing Python-3.9.0...
patching file Misc/NEWS.d/next/Build/2021-10-11-16-27-38.bpo-45405.iSfdW5.rst
patching file configure
patching file configure.ac
Installed Python-3.9.0 to /home/david/.pyenv/versions/3.9.0

Check again the list of all available Python versions:

$ pyenv versions
* system (set by /home/david/.pyenv/version)
  3.9.0

Set a local application-specific version

$ pyenv local 3.9.0

That command writes the version name to a .python-version file in the current directory.

Check again the list of all available Python versions:

$ pyenv versions
  system
* 3.9.0 (set by /home/david/projects/recommender_lambda/src/.python-version)

And check again the currently active Python version:

$ pyenv version
3.9.0 (set by /home/david/projects/recommender_lambda/src/.python-version)

Uninstall a version

$ pyenv uninstall 3.9.0
pyenv: remove /home/david/.pyenv/versions/3.9.0? [y|N] y
pyenv: 3.9.0 uninstalled

For more commands refer to the command reference page.

Conclusion

pyenv is quite easy to use. It is not surprising that it reminds me of other version managers I have used before, since it was forked from rbenv and ruby-build, and modified for Python.

I hope this story has been helpful to you, especially if you haven't used a version manager before, so you can avoid version conflicts while working on multiple projects that require different versions of a given programming language.

Thank you for reading and see you in the next one!

A dev blog about nothing