title: Pythonic way to concatenate regex objects
body: <p>I have python regex objects - say, re_first and re_second - I would like to concatenate.</p>
  
  <pre><code>import re
  FLAGS_TO_USE = re.VERBOSE | re.IGNORECASE
  re_first = re.compile( r"""abc #Some comments here """, FLAGS_TO_USE )
  re_second = re.compile( r"""def #More comments here """, FLAGS_TO_USE )
  </code></pre>
  
  <p>I want one regex expression that matches either one of the above regex expressions. So far, I have</p>
  
  <pre><code>pattern_combined = re_first.pattern + '|' + re_second.pattern
  re_combined = re.compile( pattern_combined, FLAGS_TO_USE ) 
  </code></pre>
  
  <p>This doesn't scale very well the more python objects. I end up with something looking like:</p>
  
  <pre><code>pattern_combined = '|'.join( [ first.pattern, second.pattern, third.pattern, etc ] )
  </code></pre>
  
  <p>The point is that the list to concatenate can be very long. Any ideas how to avoid this mess?
  Thanks in advance.</p>