This is a short guide to get properly set up with Python, virtual environments and git on your Mac (I’m on 10.10). Heavily inspired by these great tutorials.

Initial Setup

First install Homebrew. It’s a great package manager for OS X and we’ll use it to install Python (and keep it updated in the future).

In a terminal, enter:

/usr/bin/ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"

Install Python

If all went well with the Homebrew installation, we can now use it to install Python. While Macs come with Python installed already, it’s a better practice to install a fresh version outside the OS. It’s good to install both Python 2 and Python 3 although if you know you’re only going to use one for all your development, feel free to just install that one.

# Install python 2.x
brew install python

# Install python 3.x
brew install python3

Version Control: Install Git

If you’re planning on using git (if you’re not, you should be) and don’t already have it installed, you can also install via Homebrew.

brew install git

I don’t cover git in this post (yet) but there’s a ton of good documentation out there on how to get started with it. Initially, just take a look at the official docs if you’re just getting started.

Virtual Environments

Virtual environments allow you to create isolated environments on your computer where you can install whatever packages you’d like and not have them interfere with global packages (and vice versa) or other virtual environments.

I would say they are mandatory for Python development so download the below and learn how to use them!

You can read more about pip in the docs but essentially it’s the defacto Python package manager / installer and pretty simple to use. In case you’re curious, Homebrew installed pip when it installed python so it should be on your machine, ready to use.

# First download virtualenv, the main package to create and manage
# virtual environments for Python
pip install virtualenv

# Next install some extra tooling that makes creating and managing
# projects even easier
pip install virtualenvwrapper

Environmental Variables in Virtual Environments

This step is optional but if you’re going to be setting any configurations or storing API ids and secrets in environmental variables, I recommend also installing autoenv. Again, I highly recommend you read the docs(https://github.com/kennethreitz/autoenv), but this will essentially allow you to store environmental variables in .env files within your virtual environments and when you enter those environments, those variables will be set.

brew install autoenv
echo "source $(brew --prefix autoenv)/activate.sh" >> ~/.bash_profile

Setting Up Virtual Environments

First, you probably should read the virtualenv docs and virtualenvwrapper docs.

You need to set some locations for where you want to store your virtual environment source (the Python packages and such that you install) and the actual project folder and files. Do this via some additional variables in ~/.bash_profile or ~/.bashrc.

Feel free to change the code folder and that path to wherever you want to store your code. This directory should be created if it doesn’t already exist.

# Settings for python virtualenvwrapper
export WORKON_HOME=$HOME/virtualenvs  # virtualenv source / packages
export PROJECT_HOME=$HOME/code  # project code directory
source /usr/local/bin/virtualenvwrapper.sh  # path to shell script

Again, read the documentation, it’s well worth it.

Restricting pip to Virtual Environments

There will definitely be times when you think you’re in a virtual environment and you want to install a package within that environment only but then lo and behold you realize you just installed something globally.

To prevent such muck ups, it’s wise to add a little safety check. This is definitely optional but I find it very helpful to (1) keep me from installing anything globally that I didn’t mean to and (2) let me know when a virtual environment isn’t activated (and I thought it was).

Go to your base directory and in either .bash_profile or .bashrc, add the following:

# Only allow pip commands if within a virtual environment
export PIP_REQUIRE_VIRTUALENV=true

So what if you actually do want to install something at the global level? You can just set PIP_REQUIRE_VIRTUALENV to an empty string. To make life easier, you can create a shortcut for that, also within .bash_profile or .bashrc.

# Provide alias `gpip` to install python packages outside a virtualenv
gpip(){
   PIP_REQUIRE_VIRTUALENV="" pip "$@"
}

Now, for example, gpip install virtualenv would install the package globally outside a virtual environment.

You should know run the following to make sure everything we’ve added to .bash_profile (or equivalent) is run.

source ~/.bash_profile

Creating a Project and Virtual Environment

We use commands from virtualenvwrapper to create new Python projects. The mkproject command is super useful because it does several things at once:

1. Make the virtual environment directory
2. Make a project directory
3. Move into that project directory
4. Activate the virtual environment

Sweet!

Also, note the -p argument we specify to use Python3 within the environment. This is super important if you’re going to be coding in and using Python3.

# Create virtualenv project with Python3
mkproject -p python3 mycoolproject

You’re all set! You can now install any packages you need and start developing projects, all in the inner sanctum of the virtual environment.

For instance, just pip install django and you’re ready to start hacking away on a new web project.

If you ever need to get back into that virtual environment, all you do is type workon mycoolproject and you’ll be transported to your code folder with an activated virtualenv.

Hope this was useful and let me know if you have any issues.