title: How to update a composite list as contents of member lists are changed?
body: <p>Let's say I have:</p>
  
  <pre><code>friendlies = []
  enemies = []
  everyone = [friendlies + enemies]
  </code></pre>
  
  <p>And I say:</p>
  
  <pre><code>friendlies.append("something")
  </code></pre>
  
  <p>so that friendlies now contains:</p>
  
  <pre><code>["something"]
  </code></pre>
  
  <p>What is the pythonic way to make it so that <code>everyone</code> updates as well? So that if I update <code>friendlies</code> in the way stated above, <code>everyone</code> would contain:</p>
  
  <pre><code>["something"] 
  </code></pre>
  
  <p>?</p>