title: remove certain value in nested list
body: <p>so I have a list</p>
  <pre class="lang-py prettyprint-override"><code>[['1', '2', '3', '4', '5'], ['2', '3', '4', '5', ''], ['1', '3', '2', '4', '5'], ['2', '4', '3', '1', '5'], ['2', '1', '3', '4', '5'], ['1', '3', '2', '4', '5'], ['5', '', '', '', ''], ['5', '1', '2', '4', '3'], ['4', '1', '2', '5', '3'], ['1', '2', '3', '4', ''], ['2', '3', '4', '5', '1'], ['1', '4', '2', '', ''], ['3', '4', '2', '', ''], ['4', '3', '', '', '']]
  </code></pre>
  <p>and I wanna remove all the '' from the list so I can iterate over it without an error, i've tried using for loops but keep getting error s</p>