title: Remove all Python versions and clean install Python 3
body: <p>I have installed on my MacBook Air (v10.10.5) a number of different Python Versions (2.7, 2.6 + 3). I have tried changing python PATH settings, however, it has become too awkward to maintain. Because of this, I wish to uninstall all versions (without damaging my OS) and then clean install Python 3. How can I do this?</p>