title: Letting user decide what operation to apply to a list of numbers
body: <p>I have picked up Python recently and was wondering how I could do the following. Say we have a list of 3 numbers:</p>
  
  <pre><code>x = [1, 2, 3]
  </code></pre>
  
  <p>Then, we ask the user what to do with these numbers:</p>
  
  <pre><code>whatdo = raw_input('&gt; ')
  </code></pre>
  
  <p>For example the user enters '+2'. Now how do I apply '+ 2' to all the elements of the list?</p>