title: how to create a regex that matches `change://problem/59689726` and `change://1234567`
body: <p>I am trying to regex match strings <code>change://problem/59689726</code> and <code>change://1234567</code>but below code only matches the former,how do I change the regex to match both?how to make <code>problem/</code> optional?</p>
  
  <p>INPUT CODE:</p>
  
  <pre><code>import re
  out = '''
  &lt;change://problem/59689726&gt; This is a test1
  change://1234567 This is a test2
  [Problem]
  This is problem desription
  '''
  m = re.findall("[\S]*(?:change:\/\/problem\/(\d{8,8}))", out.split('[Problem]')[0])
  if m:
      for radar in set(m):
          print radar
  
  CURRENT OUTPUT:-
  </code></pre>
  
  <p>59689726</p>
  
  <pre><code>EXPECTED OUTPUT:-
  </code></pre>
  
  <p>59689726
  1234567</p>