title: Python: except ValueError only for strings.
body: <p>Is there a way in Python 3.3 to only except ValueError for strings? If I type a string into k, I want "Could not convert string to float" to be printed, rather than "Cannot take the square root of a negative number."</p>
  
  <pre><code>while True:
      try:
          k = float(input("Number? "))
  </code></pre>
  
  <p>....</p>
  
  <pre><code>    except ValueError:
          print ("Cannot take the square root of a negative number")
          break
      except ValueError:
          print ("Could not convert string to float")
          break
  </code></pre>