Installing Python on a Mac and Changing The Shell… I Done Goofed

It’s all about the PATH-fu

(This is a rattlesnake not a python, but they’re meaner) Photo by Meg Jerrard on Unsplash

Wait, I need to install Python, don’t I already have it?

If you happen to get a new M1 Mac, you’ll notice that you already have python installed (and yay it’s actually python3).

But the version installed, at least on the one I just set up, was Python 3.8.9 . That version came out in April, get with the times!

So easy, I just need to install python, reach for my handy dandy brew.

This mac is BRAND new, so I head to brew.sh and then copy their install command into my terminal, and I’m cooking.

It also asks me to run these lines, which I did do… but then I ended up switching away from zsh to bash:

echo '# Set PATH, MANPATH, etc., for Homebrew.' >> /Users/mckornfield/.zsh
echo 'eval "$(/opt/homebrew/bin/brew shellenv)"' >> /Users/mckornfield/.zsh
eval "$(/opt/homebrew/bin/brew shellenv)"

This basically throws two lines in your ~/.zsh file that will set up your PATH variable so the brew paths go first.

I then installed my new python, easy.

brew install python3

Now of course, doing this and then switching to bash

brew install bash
echo /opt/homebrew/bin/bash | sudo tee -a /etc/shells
chsh -s /opt/homebrew/bin/bash 

shouldn’t be a big problem, should it?

It was a problem

When I went back to bash and ran python3 --version I saw the same dang 3.8.9 pop out. 🙃

Well well, turns out my PATH looked like this:

/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin

(An aside on your PATH, it’s the list of directories that the terminal/CLI looks for programs to run. If you’re trying to run a program without a reference to the path (i.e. ./my_script.sh ) then the terminal looks in your path, starting from the first of the : separated folders. Missing programs, programs on the wrong version, or “command not found” errors are usually a sign that your PATH ain’t right.)

I needed to add those special shellenv lines to my ~/.bash_profile . Then after opening a new terminal/sourcing I got something more helpful for my PATH.

/opt/homebrew/bin:/opt/homebrew/sbin:/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin

And python3 --version gave me Python 3.10.8 , something that came out in October, yay.