score keeping interview problem

ScoreKeeper.py

# Mike Solomon
class ScoreKeeper(object):
    def __init__(self):
        self.scores = [0] * 100
        self.total = 0 # total scores inserted
        self.curr_median = None # current value of median
        self.curr_left_of = 0 # number of scores inserted < current median
        self.curr_right_of = 0 # number of scores inserted > current median

    def submit(self, score):
        """Takes a score and saves it."""
        if score < 0 or score > 99:
            raise InvalidScoreException() # TODO: implement exception
        self.scores[score] += 1
        self.total += 1

        if self.curr_median is None: # first insert
            self.curr_median = score
        elif score < self.curr_median:
            self.curr_left_of += 1
            if self.curr_left_of >= self.scores[self.curr_median] + self.curr_right_of:
                # median changed: somewhere to left of current median
                self.find_median()
        elif score > self.curr_median:
            self.curr_right_of += 1
            if self.curr_right_of > self.scores[self.curr_median] + self.curr_left_of:
                # median changed: somewhere to right of current median
                self.find_median()

    def find_median(self):
        """ Calculate the median """
        ttl = 0
        for i, score in enumerate(self.scores):
            ttl += score
            if ttl >= self.total / 2.:
                self.curr_median = i
                self.curr_left_of = ttl - score
                self.curr_right_of = self.total - ttl
                break

    def median(self):
        """Returns the left median of all scores submitted so far."""
        return self.curr_median


sk = ScoreKeeper()
sk.submit(1)
print 'should be 1:', sk.median()
sk.submit(2)
print 'should be 1:', sk.median()
sk.submit(2)
print 'should be 2:', sk.median()
sk.submit(0)
print 'should be 1:', sk.median()
sk.submit(99)
print 'should be 2:', sk.median()
sk.submit(55)
print 'should be 2:', sk.median()
for _ in range(10):
    sk.submit(0)
print 'should be 0:', sk.median()
print sk.scores