title: Changing an element in one list changes multiple lists
body: <p>I have a list of List say <code>mysolution</code>:</p>
  
  <pre><code>&gt;&gt;&gt;mySolution
  [[0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0]]
  &gt;&gt;&gt; mySolution[0][0] = 1    
  &gt;&gt;&gt; mySolution
  [[1, 0, 0, 0], [1, 0, 0, 0], [1, 0, 0, 0], [1, 0, 0, 0]]
  </code></pre>
  
  <p>Intended output:</p>
  
  <pre><code>[[1, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0]]
  </code></pre>
  
  <p>why is it that all the 1st elements in my list of list's is being changed to 1?
  I would only like to change the first element of the first list to 1.</p>