title: python: comparing this row with next row
body: <p><code>c1</code> is a list of lists like this:</p>
  
  <pre><code>c1=[[1,2,3],[1,2,6],[7,8,6]]
  
  for row in c1:
  </code></pre>
  
  <p>i want to keep track of whether there is a change in <code>row[0]</code></p>
  
  <p>for example:</p>
  
  <p>in <code>[1, 2, 3]</code> and <code>[1, 2, 6]</code> there is no change in <code>row[0]</code></p>
  
  <p>however in <code>[1, 2, 6]</code> and <code>[ 7, 8, 6]</code> there is a change in <code>row[0]</code></p>
  
  <p>how do i catch this change?
  also i would like to know which row this changed occurred at</p>