利用循環語句完善輸入設置

使用for循環：

代碼1：
_user = "alex"
_password = "abc123"

for i in range(3):
    username = input("Username:")
    password = input("Password:")
    if username == _user and password == _password:
        print("Welcome %s login ..." % _user)
        break
    else:
        print("Invalid username or password !")
代碼2：
 

_user = "alex"
_password = "abc123"

passed_authentication = False

for i in range(3):
    username = input("Username:")
    password = input("Password:")
    if username == _user and password == _password:
        print("Welcome %s login ..." % _user)
        passed_authentication = True #真，成立
        break
    else:
 

        print("Invalid username or password !")

if not passed_authentication:
    print("您的輸入次數已經達到上限！") #只有在True的情況下，條件成立

 代碼3：

_user = "alex"
_password = "abc123"

#passed_authentication = False

for i in range(3):
    username = input("Username:")
    password = input("Password:")
    if username == _user and password == _password:
 

        print("Welcome %s login ..." % _user)
        #passed_authentication = True #真，成立
        break
    else:
        print("Invalid username or password !")
else:
    print("您的輸入次數已經達到上限！")#for循環正常結束，就可以執行下面的else語句

python學習：利用循環語句完善輸入設置