Python中如何实现工厂模式 设计模式在代码复用中的作用

class Animal:
    def __init__(self, name):
        self.name = name

    def speak(self):
        raise NotImplementedError("Subclasses must implement this method")

class Dog(Animal):
    def speak(self):
        return "Woof!"

class Cat(Animal):
    def speak(self):
        return "Meow!"

class AnimalFactory:
    def create_animal(self, animal_type, name):
        if animal_type == "dog":
            return Dog(name)
        elif animal_type == "cat":
            return Cat(name)
        else:
            raise ValueError("Invalid animal type")

# 使用工厂
factory = AnimalFactory()
dog = factory.create_animal("dog", "Buddy")
cat = factory.create_animal("cat", "Whiskers")

print(dog.speak())  # 输出: Woof!
print(cat.speak())  # 输出: Meow!

# 错误示例
try:
    unknown_animal = factory.create_animal("bird", "Tweety")
except ValueError as e:
    print(e) # 输出：Invalid animal type

class Payment:
    def pay(self, amount):
        raise NotImplementedError("Subclasses must implement this method")

class CreditCardPayment(Payment):
    def pay(self, amount):
        return f"Paid {amount} using Credit Card"

class AlipayPayment(Payment):
    def pay(self, amount):
        return f"Paid {amount} using Alipay"

class WechatPayment(Payment):
    def pay(self, amount):
        return f"Paid {amount} using Wechat"

class PaymentFactory:
    def create_payment(self, payment_type):
        if payment_type == "credit_card":
            return CreditCardPayment()
        elif payment_type == "alipay":
            return AlipayPayment()
        elif payment_type == "wechat":
            return WechatPayment()
        else:
            raise ValueError("Invalid payment type")

# 使用工厂
factory = PaymentFactory()
credit_card_payment = factory.create_payment("credit_card")
alipay_payment = factory.create_payment("alipay")

print(credit_card_payment.pay(100))  # 输出: Paid 100 using Credit Card
print(alipay_payment.pay(200))  # 输出: Paid 200 using Alipay