[Python-ideas] kwargs for return

David Mertz mertz at gnosis.cx
Sat Jan 26 11:49:50 EST 2019

I was going to write exactly they're same idea Steven did.

Right now you can simply design APIs to return dictionaries or, maybe
better, namedtuples. Namedtuples are really nice since you can define new
attributes when you upgrade an API without breaking any old coffee that
used the prior attributes... Of course, you can only add more, not remove
old ones, to assure compatibility. Unlike dictionaries, namedtuples cannot
contain arbitrary "keywords" at runtime, which is either good or bad
depending on your purposes.

Recently, dataclasses are also an option. They are cool, but I haven't yet
had a reason to use them. They feel heavier than namedtuples though (as a
programming construct, not talking about memory usage or speed or whatever).

On Sat, Jan 26, 2019, 8:52 AM Steven D'Aprano <steve at pearwood.info wrote:

> On Sat, Jan 26, 2019 at 02:04:12PM +0100, Thomas Güttler Lists wrote:
> > Example:
> >
> >     status = backend.transmit_data()
> >
> > But later you want to add something to the API.
> [...]
> > How could kwargs for return look like?
> return {'status': True, 'messages': []}
> Or perhaps better:
> return ResultObject(status=True, messages=[])
> I don't see anything here that can't be done by returning a dict, a
> namedtuple (possibly with optional fields), or some other object with
> named fields. They can be optional, they can have defaults, and you can
> extend the object by adding new fields without breaking backwards
> compatibility.
> --
> Steve
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