title: regex: combine capturing group with OR condition
body: <p>Let's say I have a string :</p>
  
  <pre><code>s = "id_john, num847, id_000, num___"
  </code></pre>
  
  <p>I know how to retrieve either of 2 patterns with <code>|</code>:</p>
  
  <pre><code>re.findall("id_[a-z]+|num[0-9]+", s)
  #### ['id_john', 'num847'] # OK
  </code></pre>
  
  <p>I know how to capture a portion only of a match with parenthesis:</p>
  
  <pre><code>re.findall("id_([a-z]+)", s)
  #### ['john']
  </code></pre>
  
  <p>But I fail when i try to combine those two features, this is my <strong>desired output</strong>:</p>
  
  <pre><code>#### ['john', '847']
  </code></pre>
  
  <p>Thanks for your help.. (I work with python)</p>