Помогите перевести с Pascal на Python
var s,s1:string;
i:integer;
begin
readln(s);
s1:=s;
for i:=1 to length(s1) do begin
if s1[i]='а' then s1[i]:='б' else
if s1[i]='А' then s1[i]:='Б' else
if s1[i]='б' then s1[i]:='а' else
if s1[i]='Б' then s1[i]:='А';
end;
writeln(s1);end.