title: Assigning intermediate variable in python list comprehension
body: <p>I have a list of strings (both strings and list can be large). I want to build dictionary out of only certain elements from the list.</p>
  
  <pre><code>l = ['aaa 0','bbb 1','ccc 2','ddd 3','abc 1']
  wanted = set(['aaa','abc'])
  dict([x.split() for x in l if x.split()[0] in wanted])
  
  {'aaa': '0', 'abc': '1'}
  </code></pre>
  
  <p>Can this be done without calling <code>split()</code> operation twice?</p>