How can I make a sentinel value NOT be initialized in a class/method - OOP?

[daviddschool at gmail.com]

I am testing out some basic Object Oriented Programming in Python.  The basics: 

-User enters a name 
-While loop with a sentinel value of "quit" will continue entering names until the sentinel value is reached 
-The object is created with the inputted value (NAME and until a sentinel value is entered) 
-the object is then printed out using the constructor __str__ 

In my solution ( I am saying this because someone might have a work around that doesn't include the following below) 
-I want to use __init__ 
-I want to use __str__ 
-I want to use a while loop with a sentinel value 

EXPLANATION: 
I want to have the user enter in their NAME using a while loop, with "quit" being the sentinel value that breaks the loop.  Once the name is entered, an object is created and it is passed into a constructor def __ini__ (self, name) and then I have them return a string value using __str__ for the name entered. 
The issue I am having is that when i enter the sentinel value of QUIT, it gets initialized as the name and printed out.  How can I get around this?  I hope this makes sense.