title: python regex for finding all matches
body: <p>I have a sequence </p>
  
  <pre><code>seq = 'CCGATGACCTCACAGCCGCCTCCTGCCTTGAGGAAAGGAACTGCAATTCC'
  </code></pre>
  
  <p>I am try to get sequences of length 23bp ending with NGG where N = A or C or T or G`</p>
  
  <p>I use <code>p = re.compile('([ACGT]{21}GG)')</code> and when I say </p>
  
  <pre><code>for m in p.finditer(seq):
        print m.group()
  </code></pre>
  
  <p>I get only <code>CACAGCCGCCTCCTGCCTTGAGG</code>.</p>
  
  <p>But clearly <code>CCGCCTCCTGCCTTGAGGAAAGG</code> also matches. Why is it not reported? </p>