title: Python: Fast extraction of intersections among all possible 2-combinations in a large number of lists
body: <p>I have a dataset of ca. 9K lists of variable length (1 to 100K elements). I need to calculate the length of the intersection of <strong>all possible 2-list combinations</strong> in this dataset. Note that elements in each list are unique so they can be stored as sets in python.</p>
  
  <p>What is the most efficient way to perform this in python?</p>
  
  <p><strong>Edit</strong> I forgot to specify that I need to have the ability to match the intersection values to the corresponding pair of lists. Thanks everybody for the prompt response and apologies for the confusion!</p>