title: pandas value_counts applied to each column
body: <p>I have a <code>dataframe</code> with numerous columns (≈30) from an external source (csv file) but several of them have no value or always the same. Thus, I would to see quickly the <code>value_counts</code> for each column, how can i do that?</p>
  
  <p>For example</p>
  
  <pre><code>  Id, temp, name
  1 34, null, mark
  2 22, null, mark
  3 34, null, mark
  </code></pre>
  
  <p>Would return me an object stating that</p>
  
  <ul>
  <li>Id: 34 -> 2,  22 -> 1</li>
  <li>temp: null -> 3</li>
  <li>name: mark -> 3</li>
  </ul>
  
  <p>So I would know that temp is irrelevant and name is not interesting (always the same)</p>