List as query param

[vitalik]

Here I'm creating operation , and I want to pass to it multiple query parameters like

/test?query=1&query=2&query=3

this is my code:

from typing import List
from fastapi import FastAPI, Query, Body

app = FastAPI(debug=True)


@app.get("/test")
def check(query: List[int]):
    return query

Expected behavior

in docs I should see this param
if I call it should accept GET params

Screenshots

No parameters in docs:

when I try to call it - got an error that body is not supplied:

Environment

• OS:macOS
• FastAPI 0.54.1
• Python 3.7.4

[MichalMazurek]

This works:

from typing import List
from fastapi import FastAPI, Query

app = FastAPI()


@app.get("/test")
async def test(query: List[int] = Query(...)) -> List[int]:

    return query

All the best :)

[phy25]

Your request might have been mapped to https://fastapi.tiangolo.com/tutorial/body/. Unfortunately I am not sure if your use case is supported at all. Probably by reading request: Request directly? You can try reading Request document in Starlette to figure it out.

[phy25]

Alright https://fastapi.tiangolo.com/tutorial/query-params-str-validations/#query-parameter-list-multiple-values

You can close the issue if it works for you.

[vitalik]

This works:
async def test(query: List[int] = Query(...)) -> List[int]:
All the best :)

Yes, it works, but my guess is - either FastAPI should raise some validation error or it should treat default params as Query (like it does for string, int annotations)

[MichalMazurek]

I think the error points to missing query in the body of the request. That is what I understood :)

[tiangolo]

Thanks for the help here everyone! 👏 🙇

@vitalik you are using a "complex" data type, a list of ints, by default it will try to read it from the body. You have to make it explicit that you want it from a query if you want it to come from the query.

[vitalik]

yeah, I would say either it should allow it in get or it should make schema docs for request body

OR it should validate - that user must not declare body param that is not supported by http method (GET)

[tiangolo]

Actually, FastAPI supports reading bodies from GET requests. It's not standard, it's not part of the specs, but it's allowed for compatibility, for example with ElasitcSearch.

Sorry for the long delay! 🙈 I wanted to personally address each issue/PR and they piled up through time, but now I'm checking each one in order.

[github-actions[bot]]

Assuming the original need was handled, this will be automatically closed now. But feel free to add more comments or create new issues or PRs.