title: Use of input/raw_input in python 2 and 3
body: <p>I would like to set a user prompt with the following question:</p>
  
  <blockquote>
    <p>save_flag is not set to 1; data will not be saved. Press enter to continue.</p>
  </blockquote>
  
  <p><code>input()</code> works in python3 but not python2. <code>raw_input()</code> works in python2 but not python3. Is there a way to do this so that the code is compatible with both python 2 and python 3?</p>