title: How to return back a list instead of tuple in psycopg2
body: <p>I have the following query</p>
  
  <pre><code>    cursor.execute(
      """
      SELECT transform(row_to_json(t)) FROM 
          (select * from table 
           where a = %s 
           and b = %s limit 1000) t;
      """
      , (a_value, b_value))
  </code></pre>
  
  <p>Running <code>records = cursor.fetchall()</code> will return a list of size 1 tuples.</p>
  
  <p>Is there anyway to return just a list of lists?</p>
  
  <p>I am asking this because I'd like to transform the list of lists into a numpy matrix, and for looping through to turn the singleton tuples into a list is slow.</p>