字符串间隔3个字符进行反转

def reversal_str(string):
    temp_list = []
    new_str = ''
    for i in range(0, len(string), 3):
        split_str = string[i:i+3]
        temp_list.append(split_str)
    for n_str in temp_list:
        new_str = new_str + "".join(n_str[::-1])
    return new_str

string = '123456789'
print(reversal_str(string))

输出结果：321654987