title: accessing all sub elements in list of list for every iteration
body: <p>I Have list of list, I want to loop through the list and for every iteration i want to access the <code>ith</code> subelements of the list.</p>
  
  <p>eg:     </p>
  
  <pre><code>a = [[1, 3, 4], [2, 4, 4], [3, 7, 5]]
  </code></pre>
  
  <p>i want to do something like this </p>
  
  <pre><code>   for i in range(len(a)):
          x=a[i]
  </code></pre>
  
  <p>for 1st iteration I want to access the <code>0</code>th element from all the sub list (i.e) <code>1,2,3</code></p>
  
  <p>for 2nd iteration I want to access the <code>1</code>st element from all the sub list (i.e) <code>3,4,7</code></p>
  
  <p>I tried several approaches but failed, is there any trick to do that</p>