title: Cross Reference 2 lists in Python 2.x
body: <p>I am new to Python (using 2.6 and 2.7), but I have searched docs.Python.org and this site. I have found a similar question:
  <a href="https://stackoverflow.com/questions/4382301/comparng-lists-in-python">Comparing lists in Python</a></p>
  
  <p>...But I want to cross-reference 2 lists of different sizes and unknown orders.
  Here is an example of what I want to do:</p>
  
  <pre><code>&gt;&gt;&gt; mammals = ["gorilla","cat","rat","chimpanzee","dog","beaver"]
  &gt;&gt;&gt; apes =  ["orangutan","chimpanzee","human","gorilla"]
  
  # magic happens here
  
  &gt;&gt;&gt; print result # order doesn't matter
  ['chimpanzee', 'gorilla']
  </code></pre>
  
  <p>Giving a result of common entries.  Knowing Python it seems there would probably be a simple/elegant solution to such a simple problem.</p>