title: Combine two lists of tuples by key
body: <p>I have two lists of two elements tuples. First element of tuple is ID and second is some kind of value. Type of value depends on list.</p>
  
  <pre><code>lst1 = [ ('a', 1), ('b', 2), ('c', 3) ]
  lst2 = [ ('b', 5), ('a', 4), ('c', 6) ] 
  </code></pre>
  
  <p>What is the easiest way to combine them into:</p>
  
  <pre><code>lst3 = [ ('a', 1, 4), ('b', 2, 5), ('c', 3, 6)]
  </code></pre>