Exemplo de interface em Python.

interface_example.py

from abc import ABC, abstractmethod

class InterfaceOrder(ABC):

    @abstractmethod
    def apply_discount(self, value) -> float:
        raise NotImplementedError

class NormalOrder(InterfaceOrder):

    def apply_discount(self, value: float) -> float:
        return value - (value * 0.10)

class BlackFridayOrder(InterfaceOrder):

    def apply_discount(self, value: float) -> float:
        return value - (value * 0.30)

class ChristmasOrder(InterfaceOrder):

    def apply_discount(self, value: float) -> float:
        return value - (value * 0.50)

class OrderService():

    def order(self, order: InterfaceOrder, value: float)-> None:
        print(order.apply_discount(value))

if __name__ == '__main__':

    product_value: float = 100.00

    order_service: OrderService = OrderService()
    order_service.order(NormalOrder(), product_value)
    order_service.order(BlackFridayOrder(), product_value)
    order_service.order(ChristmasOrder(), product_value)

Para executar com o Python instalado:

python3 interface_example.py

ou

python interface_example.py

A depender da versão do Python.