decoderdict = {"aaa": "a", "bbb": "b", "ccc": "c", "tcg": "d"}
 
while True:
    dna = raw_input("Please enter the DNA string:   ").lower()
    if dna == "exit":
        break
    output = ""
    for triplet in range(0,1,3):
        decoderdict.get(dna[triple], "error") += finals
        if finals == "error":
            break
    if finals != "error":
            print "The decoded string is:   ", finals.upper()
    else:
            print "One of the triples in your code could not be decoded."

def group( lst, n ):
    ''' splits an iterable in parts with length n, e.g.
            group( [1,2,3,4], 2 ) ==> [ (1,2), (3,4) ]
    '''
    return zip( *[ lst[i::n] for i in range(n) ] )
 
aa_dict = { "AAA": "A", "GGG": "C", "CCC": "B" }
 
s = "AAAGGGCCC"
 
g = [ "".join(t) for t in group(s, 3) ]
 
for triplet in g:
    print aa_dict[triplet],

l='' # a place to attach the results of <i in dictionary> to#
for i in <NameOfInput/TheThingYouWantToEncrypt>: 
    if i in <NameOfdictionary>:
        L=L+<NameOfdictionary>[<NameOfInputInsideBrackets>] 
        #attach the value of the dictionary to each letter to the empty string#
         # can be written as L+= instead of L=L+, and is another way to join/append to a list/tuple 
    else:
        pass
        # you can also insert<print i> if u want it to print a char unknown to the dictionary!#
        #the pass just tells him to ingore that letter# 
print l
#print the final output, if i would put it under the if/else idention, it would have print each step of the encryption on a different line#

def crypt(input_sequence, dictionary):
    L = ''
    for i in input_sequence:
        if i in dictionary:
            L += dictionary[i]
    return L