Installing Python 3 on Mac OS X¶
The latest version of Mac OS X, High Sierra, comes with Python 2.7 out of the box.
You do not need to install or configure anything else to use Python 2. These instructions document the installation of Python 3.
The version of Python that ships with OS X is great for learning, but it’s not good for development. The version shipped with OS X may be out of date from the official current Python release, which is considered the stable production version.
Doing it Right¶
Let’s install a real version of Python.
Before installing Python, you’ll need to install GCC. GCC can be obtained by downloading XCode, the smaller Command Line Tools (must have an Apple account) or the even smaller OSX-GCC-Installer package.
Note
If you already have XCode installed, do not install OSX-GCC-Installer. In combination, the software can cause issues that are difficult to diagnose.
Note
If you perform a fresh install of XCode, you will also need to add the
commandline tools by running xcode-select --install on the terminal.
While OS X comes with a large number of UNIX utilities, those familiar with Linux systems will notice one key component missing: a package manager. Homebrew fills this void.
To install Homebrew, open Terminal or
your favorite OSX terminal emulator and run
$ ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"
The script will explain what changes it will make and prompt you before the
installation begins.
Once you’ve installed Homebrew, insert the Homebrew directory at the top
of your PATH environment variable. You can do this by adding the following
line at the bottom of your ~/.profile file
export PATH=/usr/local/bin:/usr/local/sbin:$PATH
Now, we can install Python 3:
$ brew install python3
This will take a minute or two.
Working with Python 3¶
At this point, you have the system Python 2.7 available, potentially the Homebrew version of Python 2 installed, and the Homebrew version of Python 3 as well.
$ python
will launch the system Python interpreter.
$ python2
will launch the homebrew-installed Python 2 interpreter (if any).
$ python3
will launch the homebrew-installed Python 3 interpreter.
If the Homebrew version of Python 2 is installed then pip2 will point to Python 2.
If the Homebrew version of Python 3 is installed then pip3 will point to Python 3.
The rest of the guide will assume that python references Python 3. You can simply choose to always invoke python3 instead, and much is backwards compatible. However, performing the following steps will set Python 3 as the default interpreter for python in a shell.
# Do I have a Python 2 problem?
$ python --version
Python 2.7.10 # Referencing OSX system install
$ which python
/usr/bin/python # Yup, homebrew's would be in /usr/local/bin
# Symlink /usr/local/bin/python to python3
$ ln -s /usr/local/bin/python3 /usr/local/bin/python
$ python --version
Python 3.6.4 # Success!
# If you still see 2.7 ensure in PATH /usr/local/bin/ takes pecedence over /usr/bin/
Pipenv & Virtual Environments¶
The next step is to install Pipenv, so you can install dependencies and manage virtual environments.
A Virtual Environment is a tool to keep the dependencies required by different projects in separate places, by creating virtual Python environments for them. It solves the “Project X depends on version 1.x but, Project Y needs 4.x” dilemma, and keeps your global site-packages directory clean and manageable.
For example, you can work on a project which requires Django 1.10 while also maintaining a project which requires Django 1.8.
So, onward! To the Pipenv & Virtual Environments docs!
This page is a remixed version of another guide, which is available under the same license.
