title: how to specify version of python to run a script?
body: <p>I'm learning python now using a mac which pre-installed python 2.7.5. But I have also installed the latest 3.4.</p>
  
  <p>I know how to choose which interpreter to use in command line mode, ie python vs python 3 will bring up the respective interpreter. </p>
  
  <p>But if I just write a python script with this header in it "#!/usr/bin/python" and make it executable, how can I force it to use 3.4 instead of 2.7.5?</p>
  
  <p>As it stands, print sys.version says:</p>
  
  <p>2.7.5 (default, Aug 25 2013, 00:04:04) 
  [GCC 4.2.1 Compatible Apple LLVM 5.0 (clang-500.0.68)]</p>