Build a Discount Calculator - Step 30

Python
1

Tell us what’s happening:

engine = DiscountEngine(strategies)
best_price = engine.calculate_best_price(product, user_tier)

And the error I get: You should create a DiscountEngine instance with the strategies list.

If I print best_price, the terminal shows me the result with the correct discount.

Your code so far

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]

        for strategy in self.strategies:
            if strategy.is_applicable(product, user_tier):
                discounted = strategy.apply_discount(product)
                prices.append(discounted)

        return min(prices)

# User Editable Region

if __name__ == '__main__':
    product = Product('Wireless Mouse', 50.0)
    user_tier = 'Premium'

    strategies = [
        PercentageDiscount(10),
        FixedAmountDiscount(5),
        PremiumUserDiscount()
    ]
engine = DiscountEngine(strategies)
best_price = engine.calculate_best_price(product, user_tier)

# User Editable Region

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Challenge Information:

Build a Discount Calculator - Step 30

2

Hi @oldman70s, and welcome to the FCC Community!

Your code in this part is correct, but it’s not a part of the __main__ if statement. If you make sure it’s a part of that if statement, you’ll be good to go!

3

Thanks for the reply! So simple, and I couldn’t see it!

1 Like