dna = {'A':0, 'C':1, 'G':2, 'T':3}
dna2 = {0:'A', 1:'C', 2:'G', 3:'T'}
 
def bintostring(num):
    seq = []
    for n in num:
        subseq = []
        for b in range(4):
            subseq.append(dna2[n & 3])
            n >>= 2
        seq.append("".join(reversed(subseq)))
    return seq
 
print(bintostring([3, 85]))
 
def stringtobin(seq):
    num = 0
    for char in seq:
        num = num * 4 + dna[char]
    return num
 
print(stringtobin("AAAT"))
print(stringtobin("CCCC"))

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