[SOLVED] Dictionary vs Marshmallow dataclass schemas for webargs

Dictionary vs Marshmallow dataclass schemas for webargs

The webargs module allows to describe argument schemas as a pure dictionary or marshmallow dataclass schema:

# Dictionary variant
@use_args({'field1': field.Int(required=True, validate=validate.Range(min=1))}, location='json')
def post(args: Dict[str, any]):
    controller.post(args)

# Marshmallow dataclass schema
@dataclass()
class Arg:
    field1: int = field(metadata=dict(required=True, validate=validate.Range(min=1)))

@use_args(Arg.Schema(), location='json')
def post(arg: Arg):
    controller.post(arg)

The first variant looks shorter and faster but we lose syntax highlight and type checks in IDE (cuz it's dict) and also it leads to longer calls, i.e. args['field1'] instead of arg.field1.

Which variant do you use in your big projects? Are there some best practices when to use the first or second variant?

Solution

There is no best practice. It is a matter of preference, really.

Sometimes, people think that a schema is too much code for just just one or two query args and a dict is enough.

I like to use schemas everywhere. I find it more consistent and it allows all schemas to derive from a base schema to inherit Meta parameters.

I don't use marshmallow dataclass, just pure marshmallow, so I always get a dict anyway.