How to use Python 2.x and 3.x on CentOS 6 ?

http://toomuchdata.com/2014/02/16/how-to-install-python-on-centos/

Do not replace the default Python! CentOS's system tools such as yum, system-config-* tools and several other things rely on the default Python 2.6 installation. Set up a virtual environment instead, where you can define which is the default version.

virtualenv --python=/usr/bin/python3.4 myenviron (only do it once)
source myenviron/bin/activate 

deactive