title: How to mutate a ndb repeated property?
body: <p>The appengine docu says on repeated ndb properiertes, that:</p>
  
  <blockquote>
    <p>When updating a repeated property, you can either assign it a new list
    or mutate the existing list in place.</p>
  </blockquote>
  
  <p><a href="https://developers.google.com/appengine/docs/python/ndb/properties#repeated">https://developers.google.com/appengine/docs/python/ndb/properties#repeated</a></p>
  
  <p>Two questions:</p>
  
  <ol>
  <li><p>do I save write operations when I just mutate the list, instead of putting a new list in place?</p></li>
  <li><p>how do I do exactly the mutation? just append the object and delete items within the list as I would do it with a list in python?</p></li>
  </ol>
  
  <p>Thanks!</p>