title: Python, print out keys of element sums of each possible combinations in a dictionary
body: <p>Below lines are created to iterate and sum each possible element combinations in a dictionary. For example, if the length of dictionary is 5, I want the sum of any 2 elements, any 3 elements, any 4 elements. </p>
  
  <pre><code>import itertools
  
  di = {'a': 1, 'b': 2, 'c': 34, 'd': 24}
  
  dict_len = range(len(di)-2, len(di))
  
  for l in dict_len:
      d_values = list(itertools.combinations(di.values(), l))
      for d in d_values:
          print d
  </code></pre>
  
  <p>Output:</p>
  
  <pre><code>35
  3
  25
  36
  58
  26
  37
  59
  27
  60
  </code></pre>
  
  <p>How can I have the keys of the values print out as well? like:</p>
  
  <pre><code>a + c = 35
  a + b = 3
  a + d = 25
  b + c = 36
  c + d = 58
  b + d = 26
  a + b + c =37
  a + c + d =59
  a + b + d =27
  c + b + d =60
  </code></pre>
  
  <p>Thank you.</p>