title: How to draw multiple levels groupby histograms in Python?
body: <p>I have a dataframe like this,</p>
  
  <pre><code>col1    col2     col3    
  A       east        5      
  A       west        7
  A       east        1
  A       east        6
  B       east        2
  B       west        9
  B       east        8
  ...
  Z       west        4
  </code></pre>
  
  <p>I know how to groupby and made histogram by using </p>
  
  <pre><code>df[df.col1.isin(ix)].groupby('col1').hist()
  </code></pre>
  
  <p>How can I get a 2 levels groupby and draw histograms by using the dataframe above?
  For each <code>col1</code> group histogram I want them in a separate plot. But for each <code>col2</code> group. I hope them in one like this.
   <a href="https://i.stack.imgur.com/8yVhl.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/8yVhl.png" alt="enter image description here"></a></p>
  
  <p>For example, the final results will be 26 histograms from <code>A-Z</code>. Each inside has 2 plots(<code>east&amp;west</code>).</p>