title: Why does this give the string index error
body: <p>When i code this really simple example i get an error as followed: 'String index out of range', but i don't know why? What I'm trying is to simply print the first element of the first row of the matrix, so 'X' basically. I know there are easier ways of doing this, however the goal of the entire excercise is different and I'm trying to understand what it all means.</p>
  <pre><code>board = [
  ['X','X','X','X'],
  ['','','O','O'],
  ['X','O','X','X'],
  ['O','X','O','X']]
  for row in board:
     print(row[0][0])
  </code></pre>