title: Iterating over a 2 dimensional python list
body: <p>I have created a 2 dimension array like:</p>
  
  <pre><code>rows =3
  columns= 2
  mylist = [[0 for x in range(columns)] for x in range(rows)]
  for i in range(rows):
      for j in range(columns):
          mylist[i][j] = '%s,%s'%(i,j)
  print mylist
  </code></pre>
  
  <p>Printing this list gives an output:</p>
  
  <pre><code>[  ['0,0', '0,1'], ['1,0', '1,1'], ['2,0', '2,1']   ]
  </code></pre>
  
  <p>where each list item is a string of the format 'row,column'</p>
  
  <p>Now given this list, i want to iterate through it in the order:</p>
  
  <pre><code>'0,0'
  '1,0'
  '2,0'
  '0,1'
  '1,1'
  '2,1'
  </code></pre>
  
  <p>that is iterate through 1st column then 2nd column and so on. How do i do it with a loop ?</p>
  
  <p>This Question pertains to pure python list while the question which is marked as same pertains to numpy arrays. They are clearly different</p>