title: Delete all characters in a multiline string up to a given pattern
body: <p>Using Python I need to delete all characters in a multiline string up to the first occurrence of a given pattern. In Perl this can be done using regular expressions with something like:</p>
  
  <pre><code>#remove all chars up to first occurrence of cat or dog or rat
  $pattern = 'cat|dog|rat' 
  $pagetext =~ s/(.*?)($pattern)/$2/xms; 
  </code></pre>
  
  <p>What's the best way to do it in Python?</p>