title: Python multiprocessing Queue put() behavior
body: <p>I'm doing something very simple using multiprocessing:</p>
  
  <pre><code>data = {'a': 1}
  queue.put(data, True)
  data.clear()
  </code></pre>
  
  <p>When I use the queue on another process (using <code>get()</code> method), I get an empty dictionary. If I remove <code>data.clear()</code> I get the keys as expected. Is there any way to wait for the <code>put()</code> to have finished the serialization ?</p>