Encapsulation

class Computer:
 def __init__(self):
  self.__maxprice = 900

 def sell(self):
  print(f"Selling price: {self.__maxprice}")

 def setMaxPrice(self, price):
  self.__maxprice = price

c = Computer()
c.sell() # 900

c.__maxprice = 1000
c.sell() # 1000

c.setMaxPrice(1000)
c.sell() # 1000