title: Optimize the performance of dictionary membership for a list of Keys
body: <p>I am trying to write a code which should return true if any element of list is present in a dictionary. Performance of this piece is really important. I know I can just loop over list and break if I find the first search hit. Is there any faster or more Pythonic way for this than given below?</p>
  
  <pre><code>for x in someList:
       if x in someDict:
             return True
  return False
  </code></pre>
  
  <p>EDIT: I am using <code>Python 2.7</code>. My first preference would be a faster method. </p>