1 print("输入用户名、密码、邮箱长度不能超过20个")
 2 s=""
 3 while True:
 4     v  = input("用户名：")
 5     if v=="q":
 6         break
 7     v = v[0:21]
 8     v1 = input("密码：")
 9     v1 = v1[0:21]
10     v2 = input("邮箱：")
11     v2= v2[0:21]
12     s1="{0}\t{1}\t{2}\n"
13     s1=s1.format(v,v1,v2)
14     s=s+s1
15 e=s.expandtabs(20)
16 print(e)