I have some experience with C++ and Fortran, and I want to start using python for my post-processing as I am starting to realise how inefficient MATLAB is for what I need to do (mostly involves plots with millions of points). 
I already had a few versions of python installed, from every time I wanted to start using. It has now become a mess. In /usr/local/bin/, here is what the command ls python* returns:
python            python2.7         python3           python3.5         python3.5m        pythonw-32
python-32         python2.7-32      python3-32        python3.5-32      python3.5m-config pythonw2.7 
python-config     python2.7-config  python3-config    python3.5-config  pythonw           pythonw2.7-32
I now want a clean slate. I want a safe way to remove all the previous versions of python, including all of their packages, so I can just install the latest version and import all the libraries I want like numpy and matplotlib smoothly (I had some issues with that). 
EDIT:
I am running on OSX Yosemite 10.10.
 
    