title: Examples for Execution model(section 4.2.4. Interaction with dynamic features)
body: <p>I don't know whether it's appropriate to ask this kind of question here. But I have to try it first.</p>
  
  <p>On python3.x doc <code>Execution model</code> section <a href="https://docs.python.org/3/reference/executionmodel.html#interaction-with-dynamic-features" rel="nofollow">4.2.4. Interaction with dynamic features</a> says:</p>
  
  <blockquote>
    <p>There are several cases where Python statements are illegal when used in conjunction with nested scopes that contain free variables.</p>
  </blockquote>
  
  <p>I wander what are the <code>several cases</code>. Could anyone show some code example for me?</p>