title: value_counts() operation error out on int types
body: <p>Determine how many first, second, and third class passengers there are in the Titanic Dataset</p>
  <pre><code>class1 = df.pclass.value_counts().'1'
  </code></pre>
  <p>I got an error value for both '1' and 1, but I would like to just get total number of people in the passenger class of 1.</p>