di_2.py

class Repository:
    def __init__(self, db: str):
        self.db = db
    def get_data(self):
        return 'Hello World'
class Service:
    def __init__(self, repsoitory: Repository):
        self.repsoitory = repsoitory
    def process(self):
        return self.repsoitory.get_data()
class UI:
    def __init__(self, service: Service):
        self.service = service
    def render(self):
        print(self.service.process())

if __name__ == '__main__':
    ui = UI(Service(DAL(db=os.getenv('db'))))
    ui.render()