How to check all versions of python installed on osx and centos

Question

I just started setting up a centos server today and noticed that the default version of python on centos is set to 2.6.6. I want to use python 2.7 instead. I googled around and

Answer 1

compgen -c python | grep -P '^python\d'

This lists some other python things too, But hey, You can identify all python versions among them.