3_2.py

   1 from string import ascii_letters
   2
   3 sum_of_priorities = 0
   4
   5 def get_3_rucksacks(fh):
   6     return [next(fh).strip() for _ in range(3)]
   7
   8
   9 with open("3.in") as fh:
  10     while True:
  11         try:
  12             rucksacks = get_3_rucksacks(fh)
  13         except StopIteration:
  14             break
  15
  16         a, b, c = rucksacks
  17
  18         item_in_all = list(set(a).intersection(set(b)).intersection(set(c)))[0]
  19
  20         priority = ascii_letters.find(item_in_all) + 1
  21         sum_of_priorities += priority
  22
  23 print(sum_of_priorities)