Peter Otten wrote: > [A, A1, A21, A22] >> Finally the append_nodes(A3, nodes) will append A3 and then return because > it has no children, and we end up with >> nodes = [A, A1, A21, A22, A3] Yay, proofreading! Both lists should contain A2: [A, A1, A2, A21, A22] nodes = [A, A1, A2, A21, A22, A3]