The best way to change the letters "A" and "B" in places

There is a function that takes an argument in the form of a line consisting of ““ a ”,“ a ”,“ b ”” and “b”.

each “b” should be replaced by “a”, each “a” ““ B ”” and also with the lower registry. Class = ""> & gt; & gt; Swap ( '"aabbbaa' ) '' BBAAAAABB '

wrote such a weak code, but the working:

  def   swap  ( text ):  New_text = []   for  c  in  text:   if  c ==  '`` `` :  new_text.append ('б')        elif c == 'б':            new_text.append('а')         elif  c ==  'a' :  news_text.ppend class = ""> 'b' :  New_text.append ( 'a' )   retu   ''  .join (New_text)     
 How can this problem be solved in another way so that the code is shorter and/or faster?