title: TypeError: list indices must be integers or slices, not list
body: <p>array = some kind of list with 3 columns and unlimited amount of rows with data inside of it.</p>
  
  <pre><code>Volume = array[0][2] 
  counter = 0
  for i in array: 
      if Volume == array[i][2]: #&lt;------ why is this line a problem? 
          counter += 1
  </code></pre>