title: count number of lists inside a list python
body: <p>I have a list like this :</p>
  
  <pre><code>test=[[1, 0, 0, 0], [1, 0, 0, 0], [0, 0, 0, 1], [1, 0, 0, 0], [0, 0, 0, 1],
      [0, 0, 1, 0], [1, 0, 0, 0], [1, 0, 0, 0], [0, 0, 0, 1], [0, 0, 0, 1],
      [0, 0, 0, 1], [1, 0, 0, 0], [0, 0, 0, 1], [0, 0, 0, 1], [0, 0, 0, 1],
      [1, 0, 0, 0], [1, 0, 0, 0],[0,0,0,0]]
  </code></pre>
  
  <p>How can i count how many lists i have inside list called <code>test</code> ?</p>