Note that this step is not strictly necessary. There's a couple reasons for this: 1) I have tested this installation process with python 2.7 so I know it works and 2) starting with a fresh install will make sure you haven't already installed other versions of the packages we are going to need. We're going to be installing a fresh version of python, even though OSX comes with python. (From the XCode Preferences, select Downloads and then Install 'Command Line Tools'.
You now need to download XCode from the App Store, and then tell XCode to install the command line tools from its Preferences pane. The installation of Developer tools has changed in 10.8. This will give you the C compiler you will need to compile certain pieces. Before you start it's important to have the OSX Developer Tools installed.