Fastapi: Can not send request with a python list

[amineHY]

Hello
I am a data scientist new in building API's. I developed a REST API using Fast API and I use python's library requests to call the API.
However, I don't know how to pass a list parameter (e;g. : ['a', 'b', ...])
I have declared the parameter in FastAPI as List[str], I also tried is declare it inside a BaseModel class as a list but this didn't work for me.
I couldn't figure out the problem. Anyone can help with an example, please?
in addition, I would like to know how do send the list in the requests library? I already use params and files but I don't know where a list can be sent.

Thank you in advance.

[jorgerpo]

Can you share your code?

You are taking into account that lists or python objects in general have to be sent and received as JSON, right?

[dbanty]

@amineHY here are a couple examples to get you pointed in the right direction. First endpoint shows a list as a query param for a GET request. The second shows the list in a JSON body for a POST request. You could also do the same for a Form I believe.

Note that here calls to client.post and client.get use the same syntax as requests.post and requests.get:

from typing import List

import fastapi
from fastapi.params import Query
from starlette.testclient import TestClient

app = fastapi.FastAPI()


@app.get("/")
def get(data: List[str] = Query(...)):
    print(data)


@app.post("/")
def post(data: List[str]):
    print(data)


if __name__ == '__main__':
    client = TestClient(app)
    print(client.post("/", json=["1", "2"]))
    print(client.get("/", params={"data": ["3", "4"]}))

I found one mention of this in the docs here though for some reason it's in a section about str validation, so maybe that should be moved elsewhere.

[amineHY]

Hi @dbanty,
Thank you for your help, your example works very well. The problem for me seems to be from the way I send a request from the client:

    requests.get("http://127.0.0.1:8000", params={"data": ["3", "4"]})

TestClient allows me to overcome this limitation, I will switch from requests library to TestClient since it is built on top of it

[tiangolo]

Thanks for the help here everyone! :clap: :bow:

Thanks for reporting back and closing the issue :+1: