Pyenv is a super simple utility that makes working with different python versions a breeze. If you have used ruby before, then most certainly you know about rbenv, that swiss knife of ruby utilities that makes installing and managing ruby packages very easy and without too much hustle. pyenv is also along those lines but for the python environment. This quick guide will only cover using pyenv in a linux environment.

Installing pyenv

1. First clone the pyenv repo where you want it installed. You may want to do this under $HOME/.pyenv, though any other folder is still fine. It’s up to you. Use the command below to clone the repo into a .pyenv folder in your home directory.

   git clone https://github.com/pyenv/pyenv.git ~/.pyenv

2. Define an environment variable called PYENV_ROOT. Make it point to the location of the pyenv repo you cloned in step one above. Then add PYENV_ROOT/bin to your $PATH. This will allow you to use the pyenv command from the command-line. Use the following commands.

   $ echo 'export PYENV_ROOT="$HOME/.pyenv"' >> ~/.bashrc
   $ echo 'export PATH="$PYENV_ROOT/bin:$PATH"' >> ~/.bashrc
   

3. Add a pyenv init command to your shell to enable shims and autocompletion. Shims are lightweight executables that reroute your commands to pyenv.

   $ echo -e 'if command -v pyenv 1>/dev/null 2>&1; then\n  eval "$(pyenv
   init -)"\nfi' >> ~/.bash_profile
   

4. Restart your shell so the changes to path take effect. (Another option is to source your .bashrc file). Use either of the following commands:

   $ exec "$SHELL"

   $ source ~/.bashrc

Using pyenv to manage multiple python versions

After carrying out the above steps successfully, using pyenv to manage multiple python verisions is easy and straightforward.

Start by viewing all the available python versions:

$ pyenv install -l

Installing a particular python version is a breeze. For example, to instal python2.6.6, simple execute the following command.

$ pyenv install 2.6.6

You can view all the python versions available to pyenv as so:

$ pyenv versions

Your default python version set by the system is not changed by pyenv unlesss you explicitly tell it to. To check the global python version:

$ python --version

To set a new global version using pyenv:

$ pyenv global 2.6.6

Another feature of pyenv is that it allows you to install different python versions of python local to particular directory which is pretty cool. For example, say you are building a project using Python 3.6.6. Simply navigate to the project folder and set a local python version (3.6.6 for our case) for that project.

$ cd new_python_project/
$ pyenv local 3.6.6

To revert to the default python interpreter that was initially installed:

$ pyenv local system

or

$ pyenv global system

Uninstalling pyenv

1. Remove the pyenv init line from your .bashrc or .bash_profile file.

2. Delete the root directory. This is the directory into which you cloned the pyenv executables from github.

   $ rm -rf $(pyenv root)

That’s the long and short of it.

Check out this article on how to use virtual environments with pyenv.