話說啊，所謂的C語言1000行，Java100行，Python20行呢。。。光一個登入就30行了。、 

一個輸入使用者名稱密碼的登入程式：

init_usrname=input('Please enter initial username:')
init_password=input('Please enter initial password:')
print (init_usrname)
print (init_password)
flag0=0
flag1=0
print('>>>User Login<<<')

while True:
    usr=input('enter username:')
    if usr==init_usrname:
        while flag0<3:
            password=input('enter password:')
            if password==init_password:
                print('Success Login!')
                flag1=1
                break
            else:
                flag0 +=1
                if flag0<=2:
                   print('Wrong Password,enter again!')
        if flag1==1:
             break
        flag0=0
        print ('You have tried three times,login again!')
    else:
        print ('Wrong Username,enter again!')