The right way to setup Python on Macos

15 Oct 2021

I use Python more and more regularly and each time I set up a new machine I go through the same steps, I forget a step and am left scratching my head, this time I decided to document them.

Problem Statement:

• I want to use multiple versions of Python locally
• I do not want to override the default version of Python on the Mac in-case it’s required some something else.
• I do not want to edit symlinks to the python binaries

Solution:

The solution is pyenv. Pyenv allows me to install and manage as many version as python as I need and flip between them where required, it uses a convention to allow my terminal to use a version on Python installed under my home directory rather then over writing the global install.

In this example I am setting up my 2020 M1 MacBook pro, by default the Python version is:

 ~  python --version                                                                         
Python 2.7.16

and

 ~  python3 --version                                                                           ok
Python 3.8.9

I really want Python 3.10 for Pygame, and 3.9 for AWS Lambda, this is how you can accomplish that.

Installation

To accomplish this we first start with Homebrew, If your reading this your likely familiar, if not Homebrew is a software manager that is priamrliy used for MacOs ( though I do use it on linux ) to install the software I require with ease.

You can install HomeBrew in a terminal like so:

/bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)"

Next we update and install pyenv

brew update
brew install pyenv

cat <<EOT >> ~/.zshrc 
export PYENV_ROOT="$HOME/.pyenv"
export PATH="$PYENV_ROOT/shims:$PATH"
export PATH="$PYENV_ROOT/bin:$PATH"
if command -v pyenv 1>/dev/null 2>&1; then
  eval "$(pyenv init -)"
fi
EOT

Now I am use zsh if you are using bash that should read:

cat <<EOT >> ~/.bash_profile 
export PYENV_ROOT="$HOME/.pyenv"
export PATH="$PYENV_ROOT/shims:$PATH"
export PATH="$PYENV_ROOT/bin:$PATH"
if command -v pyenv 1>/dev/null 2>&1; then
  eval "$(pyenv init -)"
fi
EOT

Now we have to reload our terminal

source ~/.zshrc
#or for Bash
source ~/.bash_profile

We now have pyenv correctly installed and ready for application.

Let’s install Python 3.10 and set it as the local version of Python to use for this terminal session.

I have Xcode installed, if you don’t then you may need to follow these steps first

xcode-select --install

Then install Python 3.10

pyenv install 3.10.0

OK, let’s check it out did it work?

python --version

 ~  python --version                                                                         
Python 2.7.16

No, not yet, we still need to enable it, do so for this session by running:

~  pyenv local 3.10.0
#now test
~  python --version                                                                         
Python 3.10.0

Great! Now how do we set that as the “global” default?

~  pyenv global 3.10.0
#now test
~  python --version                                                                         
Python 3.10.0

Open a new terminal session and you’ll see that it’s still 3.10.0

Additional Python versions

For this session we actually want Python 3.9.6, to accomplish this install 3.9.6 like so:

pyenv install 3.9.6

Then:

~  pyenv local 3.9.6
#now test
~  python --version                                                                         
Python 3.9.6

Perfect! Nice and clean and ready for development!