title: compare two lists and print out unequal elements
body: <p>I have two lists in the following format:</p>
  
  <pre><code>list1 = ['A','B','C','D']
  list2 = [('A',1),('B',2),('C',3)]
  </code></pre>
  
  <p>I want to compare the two lists and print out a third list which will have those elements present in list1 but not in list2 and I want to compare only the list2[i][0] elements. </p>
  
  <p>I tried the below code:</p>
  
  <pre><code>fin = [i for i in list1 if i not in list2]
  </code></pre>
  
  <p>But it prints all the elements in list1. I want the output in the above case to be :</p>
  
  <pre><code>fin = ['D']
  </code></pre>
  
  <p>Could somebody please suggest how to do that? 
  Also, I do not want to convert my 2D array list2 to 1D array. </p>