:orphan: This article should not be added to a toctree for now

.. _install3-osx:

Installing Python 3 on Mac OS X
===============================

.. image:: /_static/photos/34435689480_2e6f358510_k_d.jpg

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 The version shipped with OS X may be out of date from the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 <https://www.python.org/downloads/mac-osx/>`_,
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 <http://developer.apple.com/xcode/>`_, the smaller
`Command Line Tools <https://developer.apple.com/downloads/>`_ (must have an
Apple account) or the even smaller `OSX-GCC-Installer <https://github.com/kennethreitz/osx-gcc-installer#readme>`_
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 <http://brew.sh>`_ fills this void.

To `install Homebrew <http://brew.sh/#install>`_, open :file:`Terminal` or
your favorite OSX terminal emulator and run

.. code-block:: console

    $ 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 :envvar:`PATH` environment variable. You can do this by adding the following
line at the bottom of your :file:`~/.profile` file

.. code-block:: console

    export PATH=/usr/local/bin:/usr/local/sbin:$PATH

Now, we can install Python 3:

.. code-block:: console

    $ brew install python

This will take a minute or two.


Pip
---

Homebrew installs ``pip`` pointing to the Homebrew'd Python 3 for you.

Working with Python 3
---------------------

At this point, you have the system Python 2.7 available, potentially the
:ref:`Homebrew version of Python 2 <install-osx>` installed, and the Homebrew
version of Python 3 as well.

.. code-block:: console

    $ python

will launch the homebrew-installed Python 3 interpreter.

.. code-block:: console

    $ python2

will launch the homebrew-installed Python 2 interpreter (if any).

.. code-block:: console

    $ 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 ``pip`` will point to Python 3.

The rest of the guide will assume that ``python`` references Python 3.

.. code-block:: console

    # Do I have a Python 3 installed?
    $ python --version
    Python 3.6.4 # Success!
    # If you still see 2.7 ensure in PATH /usr/local/bin/ takes precedence 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 :ref:`Pipenv & Virtual Environments <virtualenvironments-ref>` docs!

--------------------------------

This page is a remixed version of `another guide <http://www.stuartellis.eu/articles/python-development-windows/>`_,
which is available under the same license.