1 _user="cindy"
 2 _pwd="password"
 3 passed_authentication = False
 4 for i in range (3):
 5     username = input("Username=")
 6     password = input("Password=")
 7 
 8     if username == _user and password == _pwd:
 9         print("Welcome %s login ..." %_user)
10         # passed_authentication = True
 

11         break
12     else:
13         print("Invaild username or password! please retry")
14 else: print("Do not try login again!")     #for後面加else 只要for執行完整的循環 不中斷循環 就會執行else裏面的語句
15 # if not passed_authentication == True:
16 #     print ("Do not try login again!")
17 # for i in range(1,101,3):
 

18 #
19 #         print ("loop=",i)

一個登陸小程序