title: Remove row from matrix in python
body: <p>I've got <code>matrix = [[1,2,3],[4,5,6],[7,8,9]]</code> and <code>matrix2=matrix</code>. Now I want to delete first row from matrix2 i.e., <code>matrix2.remove(matrix[0])</code>.</p>
  
  <p>But I am getting this</p>
  
  <pre><code>&gt;&gt;&gt; matrix2.remove(matrix2[0])
  &gt;&gt;&gt; matrix2
      [[4, 5, 6], [7, 8, 9]]
  &gt;&gt;&gt; matrix
      [[4, 5, 6], [7, 8, 9]]
  </code></pre>
  
  <p>First row of <code>matrix</code> is also removed. Can anyone explain this? And how to remove first row from <code>matrix2</code> without altering <code>matrix</code></p>