title: Box plot of one column grouped by another in pandas/matplotlib
body: <p>Let's say I have a data frame like this:</p>
  
  <pre><code>species,weight
  lion,130
  lion,190
  giraffe,803
  lion,150
  giraffe,1200
  hippo,1300
  giraffe,1000
  hippo,1800
  giraffe,1100
  lion,160
  </code></pre>
  
  <p>There are different numbers of animals per species (less, sorry - fewer - hippos, for example). I would like to make a box plot showing a distribution of weight for each species. How to?</p>