Python中怎样使用策略模式？

from abc import ABC, abstractmethod

# 策略接口
class PaymentStrategy(ABC):
    @abstractmethod
    def pay(self, amount):
        pass

# 具体策略类
class CreditCardStrategy(PaymentStrategy):
    def __init__(self, name, card_number, cvv, expiry_month, expiry_year):
        self.name = name
        self.card_number = card_number
        self.cvv = cvv
        self.expiry_month = expiry_month
        self.expiry_year = expiry_year

    def pay(self, amount):
        print(f"Charging {amount} using credit/debit card")

class PayPalStrategy(PaymentStrategy):
    def __init__(self, email_id, password):
        self.email_id = email_id
        self.password = password

    def pay(self, amount):
        print(f"Paying {amount} using PayPal")

# 上下文类
class ShoppingCart:
    def __init__(self):
        self.items = []
        self.strategy = None

    def add_item(self, item):
        self.items.append(item)

    def remove_item(self, item):
        self.items.remove(item)

    def set_payment_strategy(self, strategy):
        self.strategy = strategy

    def checkout(self):
        total = sum(item.price for item in self.items)
        if self.strategy:
            self.strategy.pay(total)
        else:
            print("Please set a payment strategy first")

# 使用示例
if __name__ == "__main__":
    cart = ShoppingCart()
    cart.add_item(Item("Book", 20))
    cart.add_item(Item("Pen", 5))

    credit_card = CreditCardStrategy("John Doe", "1234567890123456", "123", "12", "2025")
    paypal = PayPalStrategy("john.doe@example.com", "password123")

    cart.set_payment_strategy(credit_card)
    cart.checkout()  # 输出: Charging 25 using credit/debit card

    cart.set_payment_strategy(paypal)
    cart.checkout()  # 输出: Paying 25 using PayPal

from abc import ABC, abstractmethod

# 策略接口
class SortStrategy(ABC):
    @abstractmethod
    def sort(self, data):
        pass

# 具体策略类
class BubbleSortStrategy(SortStrategy):
    def sort(self, data):
        n = len(data)
        for i in range(n):
            for j in range(0, n - i - 1):
                if data[j] > data[j + 1]:
                    data[j], data[j + 1] = data[j + 1], data[j]
        return data

class QuickSortStrategy(SortStrategy):
    def sort(self, data):
        if len(data) <= 1:
            return data
        else:
            pivot = data[len(data) // 2]
            left = [x for x in data if x < pivot]
            middle = [x for x in data if x == pivot]
            right = [x for x in data if x > pivot]
            return self.sort(left) + middle + self.sort(right)

# 上下文类
class Sorter:
    def __init__(self, strategy):
        self.strategy = strategy

    def set_strategy(self, strategy):
        self.strategy = strategy

    def sort(self, data):
        return self.strategy.sort(data)

# 使用示例
if __name__ == "__main__":
    data = [3, 6, 8, 10, 1, 2, 1]

    bubble_sort = BubbleSortStrategy()
    quick_sort = QuickSortStrategy()

    sorter = Sorter(bubble_sort)
    sorted_data = sorter.sort(data)
    print("Bubble Sort:", sorted_data)

    sorter.set_strategy(quick_sort)
    sorted_data = sorter.sort(data)
    print("Quick Sort:", sorted_data)