登錄成功就break，登錄不成功就打印

_user = "xiaoyanzi"
_passwd = "woaini"

pass_authentication = False
for i in range(3):
    username = input("username:")
    passwd = input("passwd:")


    if _user == username and _passwd == passwd:
        print("welcome to %s login"%username)
        pass_authentication = True
        
 
break
    else:
        print("invalid username or passwd !!!")

if not pass_authentication:
    print("不洗腳的小燕子！！！")

可精簡為：

_user = "xiaoyanzi"
_passwd = "woaini"


for i in range(3):
    username = input("username:")
    passwd = input("passwd:")


    if _user == username and _passwd == passwd:
        
 
print("welcome to %s login"%username)

        break
    else:
        print("invalid username or passwd !!!")
else:
    print("不洗腳的小燕子！！！")

while循環（無限循環，又稱死循環）：

while true:
print("中國人民萬歲！")

輸出結果為n個：

中國人民萬歲！

_user = "xiaoyanzi"
_passwd = "woaini"


while true:  #死循環
    username = input("username:
 
")
    passwd = input("passwd:")


    if _user == username and _passwd == passwd:
        print("welcome to %s login"%username)

        break
    else:
        print("invalid username or passwd !!!")
else:
    print("不洗腳的小燕子！！！")

將死循環改為有限循環：

_user = "xiaoyanzi"
_passwd = "woaini"

counter = 0
while counter < 3:
    username = input("username:")
    passwd = input("passwd:")


    if _user == username and _passwd == passwd:
        print("welcome to %s login"%username)
        
        break
    else:
        print("invalid username or passwd !!!")

    counter += 1


else:
    print("不洗腳的小燕子！！！")

三次輸入錯誤之後，是否還想繼續3次，再繼續3次，效果：

_user = "xiaoyanzi"
_passwd = "woaini"

counter = 0
while counter < 3:
    username = input("username:")
    passwd = input("passwd:")


    if _user == username and _passwd == passwd:
        print("welcome to %s login"%username)
        True
        break
    else:
        print("invalid username or passwd !!!")

    counter += 1
   
     if counter == 3:
        keep_going_choice = input ("還想玩麽？[y/n]")
        if keep_going_choice == "y":
            counter = 0
        


else:
    print("不洗腳的小燕子！！！")
    

day05-06 continue語句、while循環