ABC (Python Inheritance)

• control implementations
• strict enforcement
• like Java interface

from abc import ABC, abstractmethod

class BaseService(ABC):

    @abstractmethod
    def run(self) -> str:
        pass

Protocol (Flexible, NO inheritance)

Define protocol:

from typing import Protocol

class EmbeddingProvider(Protocol):
    def embed(self, text: str) -> list[float]:
        ...

Class that matches shape, then works:

class OpenAIEmbed:
    def embed(self, text: str) -> list[float]:
        return [0.1, 0.2]