property_injection.py

class PersonService:
    @property
    def person_repo(self) -> PersonRepo:
        return PersonRepoFactory().create()
    
    def set_name(self, person_id: int, new_name: str) -> None:
        p = self.person_repo.find(person_id)
        p.name = new_name
        self.person_repo.add_or_update(p)

repository.py

class PersonRepo(Protocol):
    @abstractmethod
    def add_or_update(self, person: Person) -> None:
        ...
        
    @abstractmethod
    def remove(self, person_id: int) -> None:
        ...
        
    @abstractmethod
    def find(self, person_id: int) -> None:
        ...
        

class PersonRepoJson(PersonRepo):
    def __init__(self, file: Path) -> None:
        self.__file = file
        
    def add_or_update(self, person: Person) -> None:
        """add person to file"""
        
    def remove(self, person_id: int) -> None:
        """remove person from file"""
        
    def find(self, person_id: int) -> None:
        """find person in file"""
        

class PersonRepoSql(PersonRepo):        
    def add_or_update(self, person: Person) -> None:
        """add person to database"""
        
    def remove(self, person_id: int) -> None:
        """remove person from database"""
        
    def find(self, person_id: int) -> None:
        """find person in database"""
        
        
class PersonRepoFactory:
    def create(self) -> PersonRepo:
        if os.getenv("PERSON_REPO_TYPE") == "json":
            return PersonRepoJson(Path(os.getenv("PERSON_REPO_PATH")))
        elif os.getenv("PERSON_REPO_TYPE) == "sql":
            return PersonRepoSql()
        else:
            raise ValueError()