title: Count number of occurrence in a column Python
body: <p>I want to count the number of occurrences for each input in the column Echantillon. For example:</p>
  
  <pre class="lang-none prettyprint-override"><code>Echantillon   Classe
  1001            0
  956             1
  9658            2
  1001            0
  8566            2
  956             1
  </code></pre>
  
  <p>How can this be done using Python?</p>