def func 1(liststr):

t = list(liststr)； d=[]

dct={'A':'T '，' T':'A '，' C':'G '，' G':'C'}

For x(len(t)) in the range:

Additional (dct[t.pop()])

Return to d

Everything else is simple, 1. Direct string reverse processing, and then translate one by one; 2. Dealing with positive and negative numbers can improve efficiency for a large number of tasks; 3. Twice processing, switching between true and false; 4. Replace in the list, and then reverse; 5. Paired transposition, but low efficiency; 6. There is also direct string replacement, and then a slice s[::- 1] is enough;

lt='CATGCATCGT '

lt=lt.replace('A '，' {A} ')。 Replace ('t',' {T}'). Replace ('c',' {C}'). Replace ('g',' {G}')

result=lt.format(A='T '，T='A '，C='G '，G='C')[::- 1]