annotate response model?

Integrating Piccolo ORM with FastAPI! It’s a joy. However, I’m stumbling over a situation where I want to annotate a model response object with an additional key/value pair. (The response models have been automatically generated through create_pydantic_model, so I don’t see a way of adding fields except by subclassing – but the kind of annotations I want are more transient than this). The API is returning models from the database via .select(), and it’s here that I would want to add these transient annotations.

Imagine, as it were:

class PersonModelOut:          # but created by create_pydantic_model, based on Piccolo ORM table
    name: str
    age: int

…in the API, where the response model is PersonModelOut: return Person.select(Person.name, Person.age, Person.annotation( { "disposition": "cranky" } ).where(Person.age > 40).run()

Or is this totally off the wall?

[dantownsend]

That’s right. I think this would be a valuable feature. I’ll try and add it.

It would be worth upgrading create_pydantic_model in a similar way, so it can also generate nested models.

create_pydantic_model(Band, nested_tables=[Band.manager])

[dantownsend]

There’s a couple of solutions I can think of, but I haven’t tried them out.

One option is a JSON field.

from pydantic import BaseModel, Json

class MyModel(BaseModel):
    id: int
    extra: Json  # Or could also be str

That way you can add extra return data into the JSON field.

The other approach is using optional fields in Pydantic:

import typing as t

from pydantic import BaseModel

class MyModel(BaseModel):
    id: int
    extra: t.Optional[str]

Not sure if either are what you’re after.