humanDNA = "CGCAAATTTGCCGGATTTCCTTTGCTGTTCCTGCATGTAGTTTAAACGAGATTGCCAGCACCGGGTATCATTCACCATTTTTCTTTTCGTTAACTTGCCGTCAGCCTTTTCTTTGACCTCTTCTTTCTGTTCATGTGTATTTGCTGTCTCTTAGCCCAGACTTCCCGTGTCCTTTCCACCGGGCCTTTGAGAGGTCACAGGGTCTTGATGCTGTGGTCTTCATCTGCAGGTGTCTGACTTCCAGCAACTGCTGGCCTGTGCCAGGGTGCAGCTGAGCACTGGAGTGGAGTTTTCCTGTGGAGAGGAGCCATGCCTAGAGTGGGATGGGCCATTGTTCATG"
mouseDNA = "CGCAATTTTTACTTAATTCTTTTTCTTTTAATTCATATATTTTTAATATGTTTACTATTAATGGTTATCATTCACCATTTAACTATTTGTTATTTTGACGTCATTTTTTTCTATTTCCTCTTTTTTCAATTCATGTTTATTTTCTGTATTTTTGTTAAGTTTTCACAAGTCTAATATAATTGTCCTTTGAGAGGTTATTTGGTCTATATTTTTTTTTCTTCATCTGTATTTTTATGATTTCATTTAATTGATTTTCATTGACAGGGTTCTGCTGTGTTCTGGATTGTATTTTTCTTGTGGAGAGGAACTATTTCTTGAGTGGGATGTACCTTTGTTCTTG"
unknownDNA = "CGCATTTTTGCCGGTTTTCCTTTGCTGTTTATTCATTTATTTTAAACGATATTTATATCATCGGGTTTCATTCACTATTTTTCTTTTCGATAAATTTTTGTCAGCATTTTCTTTTACCTCTTCTTTCTGTTTATGTTAATTTTCTGTTTCTTAACCCAGTCTTCTCGATTCTTATCTACCGGACCTATTATAGGTCACAGGGTCTTGATGCTTTGGTTTTCATCTGCAAGAGTCTGACTTCCTGCTAATGCTGTTCTGTGTCAGGGTGCATCTGAGCACTGATGTGGAGTTTTCTTGTGGATATGAGCCATTCATAGTGTGGGATGTGCCATAGTTCATG"

def countCodon(string, substring):
i = string.count(substring)
return i


def compareDNA(string1, string2):
hamming = sum(c1 != c2 for c1, c2 in zip(string1, string2))
str_len = len(string1)
x = str_len-hamming
similarity_score = float(x / str_len)



def main():
c = countCodon(mouseDNA, "ATG")
print "Mouse:", c
a = countCodon(humanDNA, "ATG")
print "Human:", a
d = countCodon(unknownDNA, "ATG")
print "Unknown:", d
z = compareDNA(humanDNA, unknownDNA)
w = compareDNA(mouseDNA, unknownDNA)
if z < w:
print "human"
elif w < z:
print "mouse"
else:
print "identity cannot be determined"


if __name__== "__main__":
main()