[QUESTION] Using pydantic models for GET request query params? Currently not possible, have to use dataclasses or normal classes.

Description

Is there a way to use pydantic models for GET requests? I would like to have a similar interface for both query params and for the body. So for instance, an example could look like this:

class PingArgs(BaseModel):
    """Model input for PingArgs."""

    dt: datetime.datetime = ...
    to_sum: List[int] = ...

    @validator("dt", pre=False, always=True, whole=True)
    def validate_dt(cls, v, values):
        """Validate dt."""
        parsed_dt = v.replace(tzinfo=None)
        return parsed_dt

@router.get("/ping", tags=["basic"])
def ping(args: PingArgs, request: Request):
    """Example."""
    return JSONResponse(
        status_code=starlette.status.HTTP_200_OK,
        content={"detail": "pong", "dt": args.dt.isoformat() "summed": sum(x for x in args.to_sum)},
    )

Where as, right now I think you would have to do something like this:

@router.get("/ping", tags=["basic"])
def ping(dt: datetime.datetime = Query(None), to_sum: List[int] = Query(None), request: Request):
    """Example."""
    parsed_dt = dt.replace(tzinfo=None)
    
    return JSONResponse(
        status_code=starlette.status.HTTP_200_OK,
        content={"detail": "pong", "dt": dt.isoformat() "summed": sum(x for x in to_sum)},
    )

Hope this can be clarified.

[tiangolo]

@LasseGravesen You would do it like this:

from fastapi import FastAPI, Depends, Query

app = FastAPI()


class SearchArgs:
    def __init__(
        self,
        query: str = Query(...),
        limit: int = Query(10),
        offset: int = Query(0),
        sort: str = Query("date"),
    ):
        self.query = query
        self.limit = limit
        self.offset = offset
        self.sort = sort


@app.get("/api/v1/search_dataclass", tags=["basic"])
def search(args: SearchArgs = Depends()):
    return {"detail": "search-result", "args": args, "results": {"abc": "def"}}

Check the docs here: https://fastapi.tiangolo.com/tutorial/dependencies/classes-as-dependencies/

[jimcarreer]

This is an older issue but I wanted to show my solution to this problem:

class PagingQuery(BaseModel):
    page: conint(ge=1)
    page_size: conint(ge=1, le=250) = 50

    @classmethod
    async def depends(cls, page: int = 1, page_size: int = 50):
        try:
            return cls(page=page, page_size=page_size)
        except ValidationError as e:
            errors = e.errors()
            for error in errors:
                error['loc'] = ['query'] + list(error['loc'])
            raise HTTPException(422, detail=errors)


@app.get("/example", tags=["basic"])
def example(paging: PagingQuery = Depends(PagingQuery.depends)):
    return {"page": paging.page, "page_size": paging.page_size}

I don’t know if this helps anyone / solves the problem but it does allow you to use pydantic validation for query parameters and get similar error responses to payload validation failure.