class Computer:
    
    def __init__(self):
        self.__maxPrice=900
        
    def sell(self):
        print("max price {}".format(self.__maxPrice))
        
        
    def setMaxPrice(self,price):
        self.__maxPrice=price
    
    
c = Computer()
c.sell()

c.__maxPrice=1000
c.sell()

c.setMaxPrice(1000)
c.sell()