Here are my notes on installing Python and related packages useful for my web development with Plone and web frameworks such as Pyramid, or for pure scripting work.

Python

Homebrew provides what they call a formula for Python 2.7.x and another one for Python 3.x. They don't conflict, so they can both be installed. The resulting executable python will point to the 2.x and python3 to the 3.x version.

So, installing Python 2.7:

$ brew install python
...
==> Caveats
Pip and setuptools have been installed. To update them
  pip install --upgrade pip setuptools

You can install Python packages with
  pip install <package>

They will install into the site-package directory
  /usr/local/lib/python2.7/site-packages
...

Let's try it:

$ python
Python 2.7.11 (default, Dec  5 2015, 14:44:53)
[GCC 4.2.1 Compatible Apple LLVM 7.0.0 (clang-700.1.76)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>>

And installing Python 3 is done the same way, except we point to python3:

$ brew install python3
...
==> Summary
🍺  /usr/local/Cellar/python3/3.5.1: 3420 files, 59M

Run python3 to use it:

$ python3
Python 3.5.1 (default, Dec  7 2015, 21:59:10)
[GCC 4.2.1 Compatible Apple LLVM 7.0.0 (clang-700.1.76)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>>

Using virtual Python environments

The virtualenv tool helps create isolated Python environments. Basically, you use it to create a folder that will contain all the executables and libraries that a specific Python project needs. You will be able to run Python inside that folder and install your project's dependencies (generally using Pip) in an isolated way, i.e. without interfering with another project which has its own "virtual env".

Check the website for all you need to get started with virtualenv.

First, let's install it on our previously Homebrew-installed Python 2.7:

$ pip install virtualenv

Note that we are actually calling /usr/local/Cellar/python/2.7.11/bin/pip since Python was installed under /usr/local/Cellar/python.

To ease my work, I will also use the virtualenvwrapper package, which provides a set of productivity commands for working with virtual environments.

Install it:

$ pip install virtualenvwrapper

Let's make sure my environments are placed in my home under ~/.virtualenvs:

$ export WORKON_HOME=~/.virtualenvs

Then we need to override the $PATH search by setting VIRTUALENVWRAPPER_PYTHON to the full path of the Python interpreter to use, and VIRTUALENVWRAPPER_VIRTUALENV to the full path of the "virtualenv" binary to use.

$ export VIRTUALENVWRAPPER_PYTHON=/usr/local/Cellar/python/2.7.11/bin/python
$ export VIRTUALENVWRAPPER_VIRTUALENV=/usr/local/bin/virtualenv

Then use the source command to source virtualenvwrapper's shell script (installed under /usr/local/bin in my case) to your shell startup file:

$ source /usr/local/bin/virtualenvwrapper.sh

After that, let's say we need to create a new isolated environment to be used for working with Plone 5. It's quick and easy using the mkvirtualenv command:

$ mkvirtualenv env-plone5

New python executable in env-plone5/bin/python2.7
Also creating executable in env-plone5/bin/python
Installing setuptools, pip, wheel...done.
virtualenvwrapper.user_scripts creating /Users/kayeva/.virtualenvs/env-plone5/bin/predeactivate
virtualenvwrapper.user_scripts creating /Users/kayeva/.virtualenvs/env-plone5/bin/postdeactivate
virtualenvwrapper.user_scripts creating /Users/kayeva/.virtualenvs/env-plone5/bin/preactivate
virtualenvwrapper.user_scripts creating /Users/kayeva/.virtualenvs/env-plone5/bin/postactivate
virtualenvwrapper.user_scripts creating /Users/kayeva/.virtualenvs/env-plone5/bin/get_env_details
(env-plone5)$

After you have finished and want to stop working on the environment, just type deactivate:

(env-plone5)$ deactivate
$

To see how virtualenvwrapper's workon command allows us to interact with "virtual envs" we have created, here are two examples:

$ workon
env-mrbob
env-plone5
env-redislite

$ workon env-mrbob
(env-mrbob)$
(env-mrbob)$ ...
(env-mrbob)$ workon env-plone5
(env-plone5)$

A last requirement, for my Plone installations: libjpeg

This is handled using Homebrew since it's more a system level dependency.

$ brew install libjpeg
==> Downloading https://homebrew.bintray.com/bottles/jpeg-8d.el_capitan.bottle.2
######################################################################## 100.0%
==> Pouring jpeg-8d.el_capitan.bottle.2.tar.gz

🍺  /usr/local/Cellar/jpeg/8d: 18 files, 760K

After all this, I was productive again going back to working on my current Plone projects.