change_str = ‘123456‘


def temp(a, b):
    a, b = b, a
    return a, b


def change(change_str: str = change_str) -> str:
    change_list = list(change_str)
    result_list = []
    j = 0

    for i in range(0, len(change_list) - 1):
        j += 1
        if j % 2 != 0:
            c = temp(change_list[i], change_list[i + 1])
            result_list += list(c)
    print(‘‘.join(result_list))

change()

# 结果 214365