import sys from unittest import mock from dependency_injector import containers, providers from dependency_injector.wiring import inject, Provide 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.as_int(), ) 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') container.config.timeout.from_env('TIMEOUT') container.wire(modules=[sys.modules[__name__]]) main() # <-- dependency is injected automatically with container.api_client.override(mock.Mock()): main() # <-- overridden dependency is injected automatically