title: re.finditer() returning same value for start and end methods
body: <p>I'm having some trouble with the re.finditer() method in python. For example:</p>
  
  <pre><code>&gt;&gt;&gt;sequence = 'atgaggagccccaagcttactcgatttaacgcccgcagcctcgccaaaccaccaaacacacca'
  &gt;&gt;&gt;[[m.start(),m.end()] for m in re.finditer(r'(?=gatttaacg)',sequence)]
  
  out: [[22,22]]
  </code></pre>
  
  <p>As you can see, the <code>start()</code> and <code>end()</code> methods are giving the same value. I've noticed this before and just ended up using <code>m.start()+len(query_sequence)</code>, instead of <code>m.end()</code>, but I am very confused why this is happening.</p>