title: python3: how to enable strong typing?
body: <p>Is there a way to get real strong typing in python3, such that one gets a runtime error, when the wrong type is used?
  See following example:</p>
  
  <pre><code>def pick(k:int = None):
      if k: print("value: ", k)
      else: print("no value")
  
  pick()
  pick(1000)
  pick("error")
  </code></pre>
  
  <p>this gives the following output:</p>
  
  <pre><code>no value       &lt;- can be accepted, and for this example it would be useful
  value:  1000
  value:  error  &lt;- here should come a runtime error
  </code></pre>