Codility - Genomic range query

genomic-query.py

def solution(S, P, Q):
    m_size = len(P)
    count_size = len(S) + 1
    A = [0] * count_size
    C = [0] * count_size
    G = [0] * count_size

    for i in xrange(len(S)):
        nucleotide = S[i]
        A[i + 1] += A[i] + (1 if nucleotide == 'A' else 0)
        C[i + 1] += C[i] + (1 if nucleotide == 'C' else 0)
        G[i + 1] += G[i] + (1 if nucleotide == 'G' else 0)

    for m_index in xrange(m_size):
        range_from = P[m_index]
        range_to = Q[m_index] + 1

        if A[range_to] > A[range_from]:
            P[m_index] = 1
        elif C[range_to] > C[range_from]:
            P[m_index] = 2
        elif G[range_to] > G[range_from]:
            P[m_index] = 3
        else:
            P[m_index] = 4

    return P