# oop/class.price.py
class Price:
    def __init__(self):
        self.net_price = None

    def final_price(self, vat, discount=0):
        """Returns price after applying vat and fixed discount."""
        return (self.net_price * (100 + vat) / 100) - discount

p1 = Price()
p1.net_price = 100
print(Price.final_price(p1, 20, 10))  # 110 (100 * 1.2 - 10)
print(p1.final_price(20, 10))  # equivalent


"""
$ python class.price.py
110.0
110.0
"""
