title: Create an instance of a random class
body: <p>i'm currently making a text-based game on python and i have a question.
  I have classes for some rooms like RoomSpider, RoomSoldier, RoomDragon, etc. and I want to create a map (3d array) and fill some rooms with an instance of a random class.</p>
  
  <p>For example:</p>
  
  <pre><code>[[RoomSpider, RoomSoldier],
  [RoomSoldier,RoomDragon]]
  </code></pre>
  
  <p>How can I do to create an instance of a random class?</p>