from unittest import mock from dependency_injector import containers, providers from dependency_injector.wiring import Provide, inject from after import ApiClient, Service class Container(containers.DeclarativeContainer): config = providers.Configuration() api_client = providers.Singleton( ApiClient, api_key=config.api_key, timeout=config.timeout, ) service = providers.Factory( Service, api_client=api_client, ) @inject def main(service: Service = Provide[Container.service]): ... if __name__ == "__main__": container = Container() container.config.api_key.from_env("API_KEY", required=True) container.config.timeout.from_env("TIMEOUT", as_=int, default=5) container.wire(modules=[__name__]) main() # <-- dependency is injected automatically with container.api_client.override(mock.Mock()): main() # <-- overridden dependency is injected automatically