1. 工厂模式

from abc import ABCMeta, abstractmethod


class Payment(metaclass=ABCMeta):

    @abstractmethod
    def pay(self, money):
        pass


class Alipay(Payment):
    def __init__(self, use_huabei=False):
        self.use_huabei = use_huabei

    def pay(self, money):
        if self.use_huabei:
            print("使用花呗支付 %d " % money)
        else:
            print("Ali payed %d" % money)


class WechatPay(Payment):

    def pay(self, money):
        print("Wechat pay %d" % money)


class PaymentFactory(metaclass=ABCMeta):

    @abstractmethod
    def create_payment(self):
        pass


class AliPayFactory(PaymentFactory):
    def create_payment(self):
        return Alipay()


class WechatPayFactory(PaymentFactory):
    def create_payment(self):
        return WechatPay()


class HuabeiPayFactory(PaymentFactory):
    def create_payment(self):
        return Alipay(use_huabei=True)


if __name__ == '__main__':
    pf = HuabeiPayFactory()
    p = pf.create_payment()
    p.pay(100)

假设需要增加一种支付方式 银联支付
则需要 增加两个类 BankPay BankPayFactory

from abc import ABCMeta, abstractmethod


class Payment(metaclass=ABCMeta):

    @abstractmethod
    def pay(self, money):
        pass


class Alipay(Payment):
    def __init__(self, use_huabei=False):
        self.use_huabei = use_huabei

    def pay(self, money):
        if self.use_huabei:
            print("使用花呗支付 %d " % money)
        else:
            print("Ali payed %d" % money)


class WechatPay(Payment):

    def pay(self, money):
        print("Wechat pay %d" % money)


class BankPay(Payment):

    def pay(self, money):
        print("银联支付 pay %d" % money)


class PaymentFactory(metaclass=ABCMeta):

    @abstractmethod
    def create_payment(self):
        pass


class AliPayFactory(PaymentFactory):
    def create_payment(self):
        return Alipay()


class WechatPayFactory(PaymentFactory):
    def create_payment(self):
        return WechatPay()


class HuabeiPayFactory(PaymentFactory):
    def create_payment(self):
        return Alipay(use_huabei=True)


class BankPayFactory(PaymentFactory):
    def create_payment(self):
        return BankPay()


if __name__ == '__main__':
    pf = BankPayFactory()
    p = pf.create_payment()
    p.pay(100)

对于与每个 具体的产品类 （WechatPay AliPay BankPay） 必须增加 相应的 工厂类 （WechatPayFactory AliPayFactory BankPayFactory）