title: What does |= mean in python?
body: <p>What does the <code>|=</code> operator mean in python?</p>
  
  <p>I came across this <code>|=</code> operator in a recursive function: <a href="http://nltk.googlecode.com/svn/trunk/doc/api/nltk.corpus.reader.wordnet-pysrc.html#Synset.hypernym_distances" rel="nofollow">http://nltk.googlecode.com/svn/trunk/doc/api/nltk.corpus.reader.wordnet-pysrc.html#Synset.hypernym_distances</a></p>