# Managing Python Versions with Pyenv

## Brandon Rozek

January 20, 2020

I wrote previously about managing python virtual environments. Since then, I’ve discovered a software called Pyenv which allows you to not only manage virtual environments but python versions. As someone who likes to develop python programs in his free time, I found this incredibly useful in keeping all my virtual environments in one place and easily upgrading to a more recent version of python.

To install, follow the steps outlined in the pyenv-istaller repository. As of now, it’s a bash script.

## Python Versions

Once it’s installed, we need to download a version of python. To see what’s available,

pyenv install --list


This will give us a very large list of all the different python versions we can install. Let’s say we want to install vanilla Python version 3.8.1. Then all we do is specify that after the install keyword,

pyenv install 3.8.1


Now pyenv has a great concept where you can set certain folders to automatically load a specific python version or virtual environment. To set the current directory to use python 3.8.1 by default, run the following command:

pyenv local 3.8.1


This will then create a file called .python-version which contains the text 3.8.1. To set this globally, just replace local with global,

pyenv global 3.8.1


Finally, if you only want to specify a python version for the current shell.

pyenv shell 3.8.1


## Python Virtual Environments

To create a virtual environment, run the following

pyenv virtualenv name


This will create a virtual environment called name that is bound to the version of Python you have enabled at the current moment.

Once it’s created you can activate it with the following,

pyenv activate name


You can also use the local and global pyenv commands to set the current directory or default to be the virtual environment. To do that, all we need to do is replace the python version from above with the environment name

pyenv local name


With this, you now have a python virtual environment to play with!

## Other useful commands

Which version or virtual environment am I using?

pyenv version


Which versions or virtual environments are available to me?

pyenv versions


Which virtual environment or version contains a command I’m looking for? (e.g spyder)

pyenv whence executable