title: $PYTHONSTARTUP with python 2.7 and python 3.2
body: <p>I finally started using python 3 alongside python 2.7 on Linux.</p>
  
  <p>I setup my python shell using a startup-script defined by $PYTHONSTARTUP.
  Due to incompatibilities I am unable to use the same script for both versions.</p>
  
  <p>What is the easiest way to get one script for python 2.7, and another for python 3.2?</p>