num = int(input('请输入一个不多于五位的正整数：')) count = 0 # 计数器，用于记录数字位数

判断数字位数

if num < 10: count = 1 elif num < 100: count = 2 elif num < 1000: count = 3 elif num < 10000: count = 4 else: count = 5

print('这个数是%d位数' % count)

逆序打印各位数字

for i in range(count): print(num % 10, end='') num //= 10