title: How to iterate two successive elements of the lists of lists in python ?
body: <p>I am trying to iterate two successive  elements of the list of lists. </p>
  
  <pre><code>     mentionedlist=[[1,2,3,4][1,2,3,4][2,3,4,5][3,4,5,5][1,2,3,4][1,2,3,4][]]
  </code></pre>
  
  <p>Now I want to compare weather first element of a list in mentionedlist and first element of next list in mentionedlist is same, I also want to do these comparision throughout the list.</p>
  
  <pre><code> [1,2,3,4][1,2,3,4] is example of answer that i am expecting.
  </code></pre>