title: Getting key corresponding to a max value in a dictionary of lists
body: <p>I have a dictionary of ~1000 object of the form:</p>
  
  <pre><code>d = {
     'ID1': [[a1, b1, c1, d1, e1, f1], [g1, h1, i1]],
     'ID2': [[a2, b2, c2, d2, e2, f2], [g2, h2, i2]],
  }
  </code></pre>
  
  <p>The keys are strings while the values are lists of integers.</p>
  
  <p>I'd like to find the dictionary keys corresponding to the maximum of each of the following three differences: <code>(bγ - aγ)</code>, <code>(dγ - cγ)</code> and <code>(fγ - eγ)</code>, where <code>γ</code> is an int in <code>1:len(d)</code>.
  What would be a efficient/pythonic way of doing it?</p>