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For the November meeting of Front Range Pythoneers we did a bowling code kata. We worked as a group on the projector, but I also worked on my own version on my laptop. Here’s my code, which was fun to write. It’s a single file which contains its test cases and can be run on the command line or imported:

import unittest

class Frame(object):
    def __init__(self, tenth=False):
        self.rolls = []
        self.tenth = tenth

    def full(self):
        if len(self.rolls) >= self.max_rolls():
            return True
        if self.tenth:
            has_special = all([roll in ('X', '/') for roll in self.rolls])
            return len(self.rolls) == 2 and not has_special
        else:
            return self.strike()

    def roll(self, score):
        if self.full():
            raise RuntimeError('attempted to record a roll on a full frame')
        self.rolls.append(score)

    def pins(self):
        if len(self.rolls) == 0:
            return 0
        if self.strike() or self.spare():
            return 10
        else:
            return sum([int(roll) for roll in self.rolls])

    def first_roll_pins(self):
        if len(self.rolls) == 0:
            return 0
        elif self.rolls[0] == 'X':
            return 10
        else:
            return int(self.rolls[0])

    def score(self, subsequent_frames):
        if self.tenth:
            return self.tenth_frame_score()

        score = self.pins()
        if self.strike():
            score += sum([frame.pins() for frame in subsequent_frames])
        elif self.spare():
            if len(subsequent_frames) > 0:
                score += subsequent_frames[0].first_roll_pins()
        return score

    def tenth_frame_score(self):
        return min(Game(''.join(self.rolls)).score(), 40)

    def strike(self):
        return len(self.rolls) > 0 and self.rolls[0] == 'X'

    def spare(self):
        return len(self.rolls) > 0 and self.rolls[-1] == '/'

    def max_rolls(self):
        return 3 if self.tenth else 2

class Game(object):
    def __init__(self, roll_scores=''):
        self.frames = []
        for score in roll_scores:
            self.roll(score)

    def roll(self, score):
        if len(self.frames) == 0 or self.frames[-1].full():
            tenth = len(self.frames) == 9
            self.frames.append(Frame(tenth))
        self.frames[-1].roll(score)

    def score(self):
        return sum(self.frame_scores())

    def frame_scores(self):
        frame_scores = []
        for frame_index in xrange(len(self.frames)):
            frame = self.frames[frame_index]
            subsequent_frames = []
            if frame.strike() or frame.spare():
                subsequent_frames = self.frames[frame_index+1:]
                added_frames = 1
                if frame.strike() and len(subsequent_frames) > 0:
                    added_frames = 2 if subsequent_frames[0].strike() else 1
                subsequent_frames = subsequent_frames[:added_frames]
            frame_scores.append(frame.score(subsequent_frames))
        return frame_scores

class GameTest(unittest.TestCase):
    def test_initial_strike(self):
        self.assertEqual(Game('X').score(), 10)

    def test_two_strikes(self):
        self.assertEqual(Game('XX').score(), 20+10)

    def test_three_strikes(self):
        self.assertEqual(Game('XXX').score(), 30+20+10)

    def test_strike_spare_strike(self):
        self.assertEqual(Game('X9/X').score(), 20+20+10)

    def test_strike_strike_spare(self):
        self.assertEqual(Game('XX9/').score(), 30+20+10)
        self.assertEqual(Game('XX9/71').score(), 30+20+17+8)

    def test_perfect_game(self):
        game = Game('X'*12)
        self.assertEqual(len(game.frames), 10)
        self.assertEqual(game.score(), 300)

    def test_made_up_game(self):
        game = Game('X907/818/X70070/72')
        self.assertEqual(len(game.frames), 10)
        self.assertEqual(game.score(), 132)

if __name__ == '__main__':
    unittest.main()

I think that the tenth frame calculation is incorrect. My limited understanding of bowling slowed me down a fair bit. I got an object system that I’m fairly happy with, though!