Guess the Majority in a Hidden Array — Python

# Time:  O(n), n queries
# Space: O(1)

class ArrayReader(object):
    def query(self, a, b, c, d):
        """
        :type a, b, c, d: int
        :rtype int
        """
        pass

    def length(self):
        """
        :rtype int
        """
        pass
    

class Solution(object):
    def guessMajority(self, reader):
        """
        :type reader: ArrayReader
        :rtype: integer
        """
        count_a, count_b, idx_b = 1, 0, None
        value_0_1_2_3 = reader.query(0, 1, 2, 3)
        for i in reversed(xrange(4, reader.length())):
            value_0_1_2_i = reader.query(0, 1, 2, i)
            if value_0_1_2_i == value_0_1_2_3:  # nums[i] == nums[3]
                count_a = count_a+1
            else:
                count_b, idx_b = count_b+1, i
        value_0_1_2_4 = value_0_1_2_i
        for i in xrange(3):
            value_a_b_3_4 = reader.query(*[v for v in [0, 1, 2, 3, 4] if v != i])
            if value_a_b_3_4 == value_0_1_2_4:  # nums[i] == nums[3]
                count_a = count_a+1
            else:
                count_b, idx_b = count_b+1, i
        if count_a == count_b:
            return -1
        return 3 if count_a > count_b else idx_b