while循环在检查输入之前结束

It's been four days now and me being beginner I am I cant seem to make this work. So, so far my program would ask for user name and look for a match in a file I opened. If match found, it'll ask for userpassword and if userpassword is found in the file, it'll check username, password and if there is specific word on the line along with credentials, it'll open a credentials file. So I have my code working if username entered correctly the first time, it asks for the password and either breaks or lets the user to see the file. That works perfectly.It's been four days now and me being beginner I