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For comparison, here is my own solution in Python 3 to the Zebra Puzzle. To me this solution seems sorter and easier to understand:

  from itertools import permutations as perms
  houses = range(1,6)                                # houses numbered 1,2,3,4,5
  for Englishman, Spaniard, Ukrainian, Norwegian, Japanese in perms(houses):
      if Norwegian != 1: continue                                      # rule 10
      for red, green, ivory, yellow, blue in perms(houses):
          if Englishman != red: continue                               # rule 2
          if green != ivory + 1: continue                              # rule 6
          if Norwegian not in [blue-1,blue+1]: continue                # rule 15
          for coffee, tea, milk, oj, water in perms(houses):
              if coffee != green: continue                             # rule 4
              if Ukrainian != tea: continue                            # rule 5
              if milk != 3: continue                                   # rule 9
              for oldgold, kools, chesterfields, luckys, parliaments in perms(houses):
                  if kools != yellow: continue                         # rule 8
                  if luckys != oj: continue                            # rule 13
                  if Japanese != parliaments: continue                 # rule 14
                  for dog, snails, fox, horse, zebra in perms(houses):
                      if Spaniard != dog: continue                     # rule 3
                      if oldgold != snails: continue                   # rule 7
                      if chesterfields not in [fox-1,fox+1]: continue  # rule 11
                      if kools not in [horse-1, horse+1]: continue     # rule 12

                      person = {Englishman: 'Englishman', Spaniard: 'Spainard',
                                Ukrainian: 'Ukrainian', Norwegian: 'Norwegian', Japanese: 'Japanese'}

                      print(f'{person[water]} drinks water')
                      print(f'{person[zebra]} owns the zebra')

View on HN

People = collections.namedtuple('People', ['Englishman', 'Spaniard', 'Ukrainian', 'Norwegian', 'Japanese']) # etc. def rule_10(people): return people.Norwegian == 0 def rule_2(people, color): return people.Englishman == color.Red def rule_6(color): return color.Ivory - color.Green == 1 def rule_15(people, color): return abs(people.Norwegian - color.Blue) == 1 def rule_4(beverage, color): return beverage.Coffee == color.Green # etc. constraints = [ rule_1, rule_2, ... ] # etc. def inject(func, vars=locals): signature = inspect.signature(func) args_from = operator.attrgetter(signature.parameters.keys()) return func(*args_from(vars)) houses = range(0,5) for people in map(People._make, perms(houses)): for color in map(Color._make, perms(houses)): for beverage in map(Beverage._make, perms(houses)): for cigarette in map(Cigarette._make, perms(houses)): for pet in map(Pet._make, perms(houses)): if all(map(inject, constraints)): print(f'The {People._fields[beverage.Water]} drinks water') print(f'The {People._fields[pet.Zebra]} owns the zebra') sys.exit(0) print(f'Sorry, no idea who drinks water or owns a zebra') sys.exit(1)