2. 循环判断

Posted 2020-11-06 Joseph Peng

一、用 while 循环、for 循环实现

1. username = joseph，passwd = 123456
   
2. 让用户输入账号和密码，输入用户和密码输入正确的话，提示你  xxx，欢迎登录，今天的日期是xxx，程序结束
3. 错误的话，提示账号/密码输入错误，最多输入3次，如果输入3次都没有登录成功，提示失败次数过多。
4. 需要判断输入是否为空，输入空也算输入错误一次

 1 # 使用 for 循环
 2 import datetime
 3 today = datetime.date.today()
 4 username = ‘joseph‘
 5 passwd = 123456
 6 for i in range(3):
 7     get_username = input(‘Please input username:‘)
 8     get_passwd = input(‘Please input passwd:‘)
 9     if get_username.strip() == str(username).strip():
10         if get_passwd.strip() == str(passwd).strip():
11             print(‘%s,欢迎登录，今天的日期是%s‘ %(get_username,today))
12             break
13         else:
14             print(‘账号/密码输入错误‘)
15     else:
16         print(‘账号/密码输入错误‘)
17 else:
18     print(‘失败次数过多‘)

View Code

 1  1 # 使用 While 循环
 2  2 import datetime
 3  3 today = datetime.date.today()
 4  4 username = ‘joseph‘
 5  5 passwd = 123456
 6  6 count = 0
 7  7 while count < 3:
 8  8     get_username = input(‘Please input username:‘)
 9  9     get_passwd = input(‘Please input passwd:‘)
10 10     if get_username.strip() == str(username).strip():
11 11         if get_passwd.strip() == str(passwd).strip():
12 12             print(‘%s,欢迎登录，今天的日期是%s‘ %(get_username,today))
13 13             break
14 14         else:
15 15             print(‘账号/密码输入错误‘)
16 16     else:
17 17         print(‘账号/密码输入错误‘)
18 18     count = count + 1
19 19 else:
20 20     print(‘失败次数过多‘)

View Code

 知识点：

• while...else，for...else 的用法
• .strip() 的用法

二、增加提示“用户名/密码不能为空”

 1  1 import datetime
 2  2 today = datetime.date.today()
 3  3 username = ‘joseph‘
 4  4 passwd = 123456
 5  5 count = 0
 6  6 while count < 3:
 7  7     get_username = input(‘Please input username:‘)
 8  8     get_passwd = input(‘Please input passwd:‘)
 9  9     if get_username.strip() != ‘‘ and get_passwd != ‘‘:
10 10         if get_username.strip() == str(username).strip():
11 11             if get_passwd == str(passwd):
12 12                 print(‘%s,欢迎登录，今天的日期是%s‘ %(get_username,today))
13 13                 break
14 14             else:
15 15                 print(‘账号/密码输入错误‘)
16 16         else:
17 17             print(‘账号/密码输入错误‘)
18 18     else:
19 19         print(‘用户名/密码不能为空‘)
20 20     count = count + 1
21 21 else:
22 22     print(‘失败次数过多‘)

View Code

 知识点：

• 判断字符串为空：s.strip() == ‘‘

 1 # 增加提示用户名、密码为空
 2 import datetime
 3 today = datetime.date.today()
 4 username = ‘joseph‘
 5 passwd = 123456
 6 count = 0
 7 while count < 3:
 8     get_username = input(‘Please input username:‘)
 9     get_passwd = input(‘Please input passwd:‘)
10     if not get_username and not get_passwd:
11         print(‘用户名/密码不能为空‘)
12     elif get_username.strip() == str(username).strip():
13         if get_passwd == str(passwd):
14             print(‘%s,欢迎登录，今天的日期是%s‘ %(get_username,today))
15             break
16         else:
17             print(‘账号/密码输入错误‘)
18     else:
19         print(‘账号/密码输入错误‘)
20     count = count + 1
21 else:
22     print(‘失败次数过多‘)

View Code

 知识点：

• 非空即真 ，非0即真。