Sat Nov 15, 2014 5:16 pm
The Raspberry Pi Foundation recommended Operating System for the RPi is Raspbian, and this comes with both Python(2.7) and Python3 pre-installed. Since you don't need to install it I won't bother telling you how to...
Having re-read your question, the following is added for clarity: None of the 4 models of RPi board currently available come with any software 'pre-installed'. In all cases there is a requirement for an SD (or microSD) card containing an Operating System from which the RPi boots. That Operating System determines what software is then available to you.