title: averages of a two dimensional list
body: <p>Basically, the function should deliver the average of the lists within the list. 
  Example:</p>
  
  <pre><code>lst = [[46, 27, 68], [26, 65, 80], [98, 56, 35], [98, 65, 0]]
  average(lst)
  &gt;&gt;&gt; [47.0, 57.0, 63.0, 54.33333333333333]
  </code></pre>
  
  <p>My code:</p>
  
  <pre><code>def average(l):
      for i in range(len(l)):
          for j in range(len(l[0])):
              l[i] / l[j]
      return l
  </code></pre>
  
  <p>My coding shows up an error sign saying "TypeError: unsupported operand type(s) for /: 'list' and 'list'". I don't get what I'm doing wrong.</p>