Build a Discount Calculator - step 26

Python
1

In step 26 I have tried several different approaches, as you can see from what is commented out. I am stuck, and need a nudge in the right direction.

from abc import ABC, abstractmethod

class Product:
    def __init__(self, name: str, price: float) -> None:
        self.name = name
        self.price = price

    def __str__(self) -> str:
        return f'{self.name} - ${self.price}'

class DiscountStrategy(ABC):
    @abstractmethod
    def is_applicable(self, product: Product, user_tier: str) -> bool:
        pass

    @abstractmethod
    def apply_discount(self, product: Product) -> float:
        pass

class PercentageDiscount(DiscountStrategy):
    def __init__(self, percent: int) -> None:
        self.percent = percent

    def is_applicable(self, product: Product, user_tier: str) -> bool:
        return self.percent <= 70

    def apply_discount(self, product: Product) -> float:
        return product.price * (1 - self.percent / 100)

class FixedAmountDiscount(DiscountStrategy):
    def __init__(self, amount: int) -> None:
        self.amount = amount

    def is_applicable(self, product: Product, user_tier: str) -> bool:
        return product.price * 0.9 > self.amount

    def apply_discount(self, product: Product) -> float:
        return product.price - self.amount

class PremiumUserDiscount(DiscountStrategy):
    def is_applicable(self, product: Product, user_tier: str) -> bool:
        return user_tier.lower() == 'premium'

    def apply_discount(self, product: Product) -> float:
        return product.price * 0.8

class DiscountEngine:
    def __init__(self, strategies: list[DiscountStrategy]) -> None:
        self.strategies = strategies

    def calculate_best_price(self, product: Product, user_tier: str) -> float:
        prices = [product.price]
        print(prices)
        for strategy in self.strategies:
            if strategy.is_applicable(product, user_tier):
                discounted = apply_discount(product)
                prices.append(discounted)
#                discounted = apply_discount(self.product)
#                prices.append(discounted)
#                prices.append(apply_discount(self.product))


product = Product('Wireless Mouse', 50.0)
print(product)

discount = PercentageDiscount(10)
print(discount.apply_discount(product))

fixed_discount = FixedAmountDiscount(5)
print(fixed_discount.apply_discount(product))

#premium_discount = PremiumUserDiscount()
#user_tier = 'premium'
#best_price = DiscountEngine.calculate_best_price(product, user_tier)
2

hey there, would you mind providing the link to this challenge?

3

Now create a for loop that iterates over self.strategies. For each strategy, check if it’s applicable using the is_applicable method. If it is, calculate the discounted price using apply_discount and store it in a variable named discounted. Then, append the discounted price to the prices list.
and
If a strategy is applicable, you should call apply_discount and append the result to prices.

4

thank you for the instructions, but can you please give the link to the challenge?

5

Is this it? I’m not sure what you mean

6

thank you for that!

is apply_discount a function, or a method?

7

Its a method, which exists in each of three discount types. Does this affect how it is called?

8

yes, consider how you called the is_applicable method for example, vs how you called print function

9

I think the format of the call is correct, but I am weak on finding the correct link through the classes. My call is to self.apply_discount(product). Clearly that is wrong, but I am lost as to how to qualify it and load its arguments

10

self in this case is DiscountEngine, does apply_discount exist in this class? or is it in a different one?

11

Its in three different ones. What info or pointers do I have? That’s my problem. It must be strategy! Thanks for the pointers.

12

isn’t also is_applicable in three different ones? how are you using that one?

13

The same. A method depending on strategy

14

so now do you manage to write the code?

15

Got it, thanks very much.