Switching between pythons using pyenv on OSX

January 19 2015

Installation

From pyenv,

pyenv lets you easily switch between multiple versions of Python

As always, I recommend to use homebrew to install pyenv.
Assuming that you have already installed homebrew, to install pyenv, you need

brew update
brew install pyenv

This will also create a hidden folder under your user directory ~/.pyenv. In most cases,
you don’t have look at this directory.

To enable pyenv, put the following into your ~/.bash_profile or ~/.zshrc if you are using zsh. I strongly recommend zsh. Try to install it via homebrew and give it a try.

export PYENV_ROOT="$HOME/.pyenv"
export PATH="$PYENV_ROOT/bin:$PATH"
eval "$(pyenv init -)"

To enable shell completions, also add this to your shell config file

# for bash shell
if [[ -f /usr/local/opt/pyenv/completions/pyenv.bash ]]; then
    source /usr/local/opt/pyenv/completions/pyenv.bash
fi

# for zsh shell
if [[ -f /usr/local/opt/pyenv/completions/pyenv.zsh ]]; then
    source /usr/local/opt/pyenv/completions/pyenv.zsh
fi

Resetting your shell terminal, and check if pyenv runs. To list supported versions of python

pyenv install --list

For academic use, I strongly recommend anaconda3, e.g., anaconda3-2.1.0. (Also, give a try to pypy3)
Installation is a piece of cake.

pyenv install anaconda3-2.1.0

It may take some time for the installation process to finish.

To show available versions of python

pyenv versions

You should see system and anaconda3-2.1.0. System python is the version of python first found along the PATH variable.


Switch between

  • To activate anaconda3-2.1.0 in the current terminal session.
pyenv shell anaconda3-2.1.0
# check python version
python -V
# Python 3.4.1 :: Anaconda 2.1.0 (x86_64)
  • If you want to use anaconda3-2.1.0 every time you visit a particular project directory, say ~/project.
# unset the shell specific version
pyenv shell --unset
# go to the project directory
cd ~/project
pyenv local anaconda3-2.1.0
# check python version
python -V
# Python 3.4.1 :: Anaconda 2.1.0 (x86_64)

Note: you run python -V outside project, you will see the system python.

  • To use anaconda3-2.1.0 globally, run pyenv global anaconda3-2.1.0. But I don’t recommend this.

Remove pyenv

If you really don’t like pyenv and want to remove all traces of pyenv files. Just remove pyenv from homebrew and remove the ~/.pyenv directory. It will do the job. Of course, you have to also undo the changes made to the ~/.bashrc_profile or ~/.zshrc files.


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