class Seq:
    
    def __init__(self, dna):
        self.dna = dna
        self.index = len(dna)
        print("Utworzono obiekt! n")
        print(self.dna, self.index)

    def complement(self,dna):
        dna2= ""
        for letter in dna:
            if(letter == 'A'):
                dna2 += 'T'
            elif(letter == 'C'):
                dna2 += 'G'
            elif(letter == 'T'):
                dna2 += 'A'
            elif(letter == 'G'):
                dna2 += 'C'
        return dna2

    def reverse_complement(self,dna):
        dna2 = self.complement(dna)
        x = dna2[::-1]
        return x

    def rna(sled, dna):
        rna_dic = {'A': 'U', 'C':'G', 'T':'A', 'G':'C'}
        rna = []
        for nuc in dna:
            rna.append(rna_dic[nuc])
        return "".join(rna)


    def __iter__(self):
        return self

    def __next__(self):
        if self.index == 0:
            raise StopIteration
        self.index = self.index - 1
        return self.dna[self.index]




dna = 'TCAATGCATGCGGGTCTATATGCAT'
obiekt = Seq(dna)

print(obiekt.complement(dna))
print(obiekt.reverse_complement(dna))
print(obiekt.rna(dna))