from itertools import chain, permutations
st = 'ATTGC'
a = ('AT', 'GC')
a = {ord(pair[0]):pair[1] for pair in chain(*(permutations(pair, 2) for pair in a))}
print(st.translate(a))
ZnJvbSBpdGVydG9vbHMgaW1wb3J0IGNoYWluLCBwZXJtdXRhdGlvbnMKCnN0ID0gJ0FUVEdDJwoKYSA9ICgnQVQnLCAnR0MnKQphID0ge29yZChwYWlyWzBdKTpwYWlyWzFdIGZvciBwYWlyIGluIGNoYWluKCoocGVybXV0YXRpb25zKHBhaXIsIDIpIGZvciBwYWlyIGluIGEpKX0KCnByaW50KHN0LnRyYW5zbGF0ZShhKSk=