List/String seperation issue

[YoungGrassHopper]

You are not accounting for the case wher e DNA % 3 == 2. In that case you need to delete two items. The modulus operator gives you how many items you need to delete, so you can just do dna = dna[-(len(dna) % 3):]

if (DNA % 3 == 1 ): 
    del dna[-1]
    print(dna)
elif (DNA % 3 == 2):
    del dna[-2::]
    print(dna)

Yes I just fixed that but I like your idea much more seems way more efficient