title: How to "continue" OR "exit" the program by pressing keys
body: <p>Lets say I have 2 lines of code like this:</p>
  
  <pre><code>a = [1 , 2 , 3 , 4]
  print (a)
  </code></pre>
  
  <p>Now I want to add something to this code to give the user 2 options:</p>
  
  <p>1: press "<strong>Enter</strong>" to continue.</p>
  
  <p>In this case the code should print "a"</p>
  
  <p>2: press "<strong>Esc</strong>" to exit the program. </p>
  
  <p>In this case the program should be stopped (e.g. exit the code). </p>
  
  <p>I need to mention that I only want to use these 2 keys (<strong>Enter</strong>&amp;<strong>Esc</strong>) <strong>NOT any key</strong></p>
  
  <p>I have been palying with <em>raw_input</em> and <em>sys.exit</em> but it did not work. Any idea how I can do it in this example? 
  Thanks!</p>