CODEWITHSUNDEEP
pythonapifastapi
Prince
Prince

Reputation: 336

How to send a list of lists as query parameter in FastAPI?

I'm using FastAPI framework and I want to send a list of lists using Query parameters. I can send a list using the below syntax, but I am unable to pass list of lists.

sections_to_consider: Optional[List[str]] = Query(None)

I get the below output.

enter image description here

What I want is something like this

{
  "sections_to_consider": [
    ["string", "string2"],
    ["string3", "string4"]
  ]
}

I tried below syntax but getting an error.

sections_to_consider: Optional[List[list]] = Query(None)

sections_to_consider: Optional[List[List[str]]] = Query(None)

I need to accept list of lists. This is an optional parameter but, if passed, the inner list must have exactly 2 strings. Is there any way to do it in FastAPI? Or any work around?

Thanks in advance.

Upvotes: 4

Views: 12961

Answers (1)

PRStark
PRStark

Reputation: 1258

As of now, fastApi does not supports nested list from query parameters. you can find more in multiselection lists Multiselect and dropdownMenu.

Workaround can be using request body. Instead of sending the List[List[str]] form Query, can send the data by request body

  • either by new class
  • or by using depends

Example using class: app.py

from typing import List

import uvicorn
from fastapi import FastAPI, Query
from pydantic import BaseModel

app = FastAPI()

class newList(BaseModel):
  sections_to_consider: List[List[str]]

@app.post("/items/")
async def read_items(q: newList):
    return q

if __name__ == '__main__':
    uvicorn.run("6:app",host='127.0.0.1', port=8000, reload=True)

You can use a curl request or Request URL and request body from OpenApi docs

curl request:

curl -X 'POST' \
  'http://127.0.0.1:8000/items/' \
  -H 'accept: application/json' \
  -H 'Content-Type: application/json' \
  -d '{
  "sections_to_consider": [
    ["string", "string2"],
    ["string3", "string4"]
  ]
}'

Request URL:

http://127.0.0.1:8000/items/

Request Body:

{
  "sections_to_consider": [
    ["string", "string2"],
    ["string3", "string4"]
  ]
}

The Response from the request will be as below:

ResponseBody:

{
  "sections_to_consider": [
    [
      "string",
      "string2"
    ],
    [
      "string3",
      "string4"
    ]
  ]
}

Upvotes: 5

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