Python Dependency Injection Framework

Question

Is there a framework equivalent to Guice (http://code.google.com/p/google-guice) for Python?

Answer 1

After years using Python without any DI autowiring framework and Java with Spring I've come to realize that plain simple Python code often doesn't need a framework for dependency injection autowiring (autowiring is what Guice and Spring both do in Java), i.e., just doing something like this is enough:

def foo(dep = None):  # great for unit testing!
    ...

This is pure dependency injection (quite simple) but without magical frameworks for automatically injecting them for you.

Though as I dealt with bigger applications this approach wasn't cutting it anymore. So I've come up with injectable a micro-framework that wouldn't feel non-pythonic and yet would provide first class dependency injection autowiring.

Under the motto Dependency Injection for Humans™ this is what it looks like:

# some_service.py
class SomeService:
    @autowired
    def __init__(
        self,
        database: Autowired(Database),
        message_brokers: Autowired(List[Broker]),
    ):
        pending = database.retrieve_pending_messages()
        for broker in message_brokers:
            broker.send_pending(pending)

# database.py
@injectable
class Database:
    ...

# message_broker.py
class MessageBroker(ABC):
    def send_pending(messages):
        ...

# kafka_producer.py
@injectable
class KafkaProducer(MessageBroker):
    ...

# sqs_producer.py
@injectable
class SQSProducer(MessageBroker):
    ...