title: Boxplot with variable length data in matplotlib
body: <p>I have collected some data in a textfile and want to create a boxplot.
  But this datafile contains rows of variable length, for example.</p>
  <pre><code>1.2, 2.3, 3.0, 4.5  
  1.1, 2.2, 2.9
  </code></pre>
  <p>for equal length I could just do</p>
  <pre><code>PW  = numpy.loadtxt(&quot;./learning.dat&quot;)  
  matplotlib.boxplot(PW.T);
  </code></pre>
  <p>How do I handle variable length data lines?</p>