longest_homopolymer.py

def find_longest_homopolymer(seq):
    if seq == None or seq == '':
        return 0

    polymer_lengths = []
    curr_len = 0
    polymer_nt = seq[0]

    for nt in seq:
        if nt != polymer_nt:
            polymer_lengths.append(curr_len)
            polymer_nt = nt
            curr_len = 1
        else:
            curr_len += 1
    
    polymer_lengths.append(curr_len)    
    return max(polymer_lengths)

print(find_longest_homopolymer(None)) # 0
print(find_longest_homopolymer('')) # 0
print(find_longest_homopolymer('G')) # 1
print(find_longest_homopolymer('GGTT')) # 2
print(find_longest_homopolymer('CCCAAAA')) # 4
print(find_longest_homopolymer('AAAAAAAAAAG')) # 10
print(find_longest_homopolymer('TGGGGGGGGAGGGGGCGGG')) # 8