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

The more easy way its by executing the next command:

ls -ls /usr/bin/python*

Output look like this:

/usr/bin/python           /usr/bin/python2.7        /usr/bin/pythonw
/usr/bin/python-config    /usr/bin/python2.7-config /usr/bin/pythonw2.7