title: I have a nested list and would like to extract parts of it using list comprehension
body: <p>I have a nested list named list1 of following:</p>
  <pre><code> list1 = [['Plane' , 'London' , 'Paris', '1']  ,  ['Helicopter', 'Budapest' , 'Rome', '2']  ,  ['Jet', 'Tokio', 'New York' , '3'] ,  ['Balloons' , 'Belgrade', 'Vienna', '2']]
  </code></pre>
  <p>I need to extract the following from list1 in python:</p>
  <pre><code> { ('London', 'Paris'): '1', 
   ('Budapest', 'Rome'): '2',
  ('Tokyo', 'New York'): '3',
  ('Belgrade', 'Vienna'): '2'}
  </code></pre>
  <p>How can I solve this with list comprehension?</p>