3_1.py

   1 from string import ascii_letters
   2
   3 sum_of_priorities = 0
   4
   5 with open("3.in") as fh:
   6     for backpack in fh:
   7         backpack = backpack.strip()
   8
   9         comp_size = len(backpack)//2
  10
  11         comp_a = set(backpack[comp_size:])
  12         comp_b = set(backpack[:comp_size])
  13
  14         item_in_both = list(comp_a.intersection(comp_b))[0]
  15         priority = ascii_letters.find(item_in_both) + 1
  16         sum_of_priorities += priority
  17
  18 print(sum_of_priorities)