title: How do I loop this
body: <p>Pretty new to Python and am using 2.7 to script.</p>
  
  <pre><code>a = raw_input("Input number or decimal only")
  Try:
      Y = float(a)
      print a
  except ValueError:
      print "wrong input, try again"
  </code></pre>
  
  <p>I need to loop this - if the input is either alphanumeric or letters, it should ask for input again.</p>
  
  <p>I can't seem to find a way to slide in a while loop in it.</p>
  
  <p>(Python newbie, please be kind!)</p>