oop05.py

# creating a class

class Item:
    #
    pay_rate = 0.8 # The pay rate after 20% discount

    # init is called automatically when an instance is created
    # Using type hints for better code readability
    # constructor
    def __init__(self, name: str, price: float, quantity=0):
        # Run validation to the received arguments
        assert price >= 0, f"Price {price} is not greater than or equal to zero!"
        assert quantity >=0, f"Quantity {quantity} is not greater than or equal to zero!"

        # assigning to self object
        self.name = name            # instance attributes
        self.price = price          # instance attributes
        self.quantity = quantity    # instance attributes

    def calculate_total_price(self):
        return self.price * self.quantity
    
    def apply_discount(self):
        # self.price = self.price * Item.pay_rate # accessing class attribute via class
        self.price = self.price * self.pay_rate # accessing class attribute via insta nce

item1 = Item("phone", 100, 5) # creating an instance of the Item class



item2 = Item("Laptop", 1000, 6) # creating another instance of the Item class

# whether a laptop has a numpad or not (not for phone)
item2.has_numpad = False # adding attribute to only item2 instance

print(Item.pay_rate)  # accessing class attribute via class
print(item1.pay_rate) # accessing class attribute via instance (not recommended)

# check all attributes of Item class level
print(Item.__dict__) 

# check all attributes of item1 instance level
print(item1.__dict__)

# applying discount
item1.apply_discount()
print(item1.price)

# applying discount at 30% for item
item2.pay_rate = 0.7 # changing pay_rate for only item2 instance
item2.apply_discount()
print(item2.price)