title: pandas: records with lists to separate rows
body: <p>I have a Python Pandas DataFrame like this (UCSC schema for NCBI RefSeq):</p>
  
  <pre><code>chrom   exonStart     exonEnds      name
  chr1    100,200,300   110,210,310   gen1
  chr1    500,700       600,800       gen2
  chr2    50,60,70,80   55,65,75,85   gen3
  </code></pre>
  
  <p>and I'd like to pair values from exonStarts and exonEnds and put them as separate rows (keeping the rest of corresponding information):</p>
  
  <pre><code>chrom   exonStart     exonEnds      name
  chr1    100           110           gen1
  chr1    200           210           gen1
  chr1    300           310           gen1
  chr1    500           600           gen2
  chr1    700           800           gen2
  chr2    50            55            gen3
  chr2    60            65            gen3
  chr2    70            75            gen3
  chr2    80            85            gen3
  </code></pre>
  
  <p>I was thinking to use combinations of python/pandas functions as:</p>
  
  <blockquote>
    <p>zip, split, melt, concat</p>
  </blockquote>
  
  <p>but somehow it doesn't work for me</p>