title: How do I find non-null combination of ha and ho
body: <p>I'm trying to find any non-null combination of ha and ho, e.g hahahoho, ha, ho, hoha... </p>
  
  <pre><code>chat_words = sorted(set(w for w in nltk.corpus.nps_chat.words()))
  
  [w for w in words.words() if re.search('^[haho]+$',w)]
  </code></pre>
  
  <p>The result I get is: </p>
  
  <pre><code>['a',
   'aa',
   'ah',
   'aha',
   'aho',
   'h',
   'ha',
   'hah',
   'hao',
   'ho',
   'o',
   'oh',
   'oho',
   'a']
  </code></pre>