Python程序：计算三位数的数字和

num = input('请输入一个三位数的整数：')

if len(num) != 3 or not num.isdigit(): print('输入有误，请重新输入！') else: sum = int(num[0]) + int(num[1]) + int(num[2]) print('{}+{}+{}={}'.format(num[0], num[1], num[2], sum))