What is the equivalent of Django s get or create om SQLAlchemy using Python

Question

Hi all. My requirement was that I needed to get my hands on an object from a database (if it exists) or if not, to create it on my own.

Django has a method called get_or_create and it does exactly this. But, my question is that, is there an alternative or an equivalent to use the same thing to obtain same functionality in SWLAlchemy?

This is what I am doing now:

def get_or_create_instrument(session, serial_number):
    instrument = session.query(Instrument).filter_by(serial_number=serial_number).first()
    if instrument:
        return instrument
    else:
        instrument = Instrument(serial_number)
        session.add(instrument)
        return instrument

All help appreciated!

Answer 1

As far as I know, there is no literal shortcut to go about doing this. And whatever you're doing is the right way to go about doing it.

You can also generalize it and go about it this way, check it out:

def get_or_create(session, model, defaults=None, **kwargs):
    instance = session.query(model).filter_by(**kwargs).first()
    if instance:
        return instance, False
    else:
        params = dict((k, v) for k, v in kwargs.iteritems() if not isinstance(v, ClauseElement))
        params.update(defaults or {})
        instance = model(**params)
        session.add(instance)
        return instance, True

Hope this helped!