#Excersice 8
try:
    sprot = input('Please insert a filename')
    infile = open(sprot, 'r')
except IOError as error:
    print("We have a problem opening the file, due to:", str(error))
    sys.exit(1)
dna = ''
startCodon = 0
stopCodon = 0

for line in infile:
    if line[0] != '>':
        dna += str(line[:-1])
for base in range(len(dna)):
    if (dna[base:base+3] == 'ATG' and base > stopCodon):
        startCodon = base
        iterations = (len(dna) - startCodon) / 3
        for i in range(iterations):
            index = i * 3 + startCodon
            if (dna[index:index+3] == 'TAA' or dna[index*3:index*3+3] == 'TAG' or dna[index*3:index*3+3] == 'TGA'):
                stopCodon = index
                print('The start codon is:', startCodon + 1, 'and the coresponding stopcodon is:', stopCodon + 1)    #print +1 since python counts from 0 and not 1.
                break
infile.close