[Python] FastAPI JSON List in body raises 'There was an error parsing the body' exception

Using the FastAPI documentation, I'm attempting to send a POST request to an endpoint that takes a JSON object with a list as input:

{
"urls":[
"https://www.website.com/",
"https://www.anotherwebsite.com"
]
}


Simplified reproducible example app code:

from fastapi import FastAPI

app = FastAPI()


@app.post("/checkUrls")
def checkUrls(urls: list[str]):
return urls


#alternatively (given that I expect each url to be unique)
@app.post("/checkUrlsSet")
def checkUrlsSet(urls: set[str]):
return urls


When I test the endpoint using the Python requests library like this:

import requests

rListTest = requests.post("http://127.0.0.1:8000/checkUrls", json = {"urls" : ["https://www.website.com/", "https://www.anotherwebsite.com"]})

print(rListTest.status_code)
print(rListTest.json())

rSetTest = requests.post("http://127.0.0.1:8000/checkUrlsSet", json = {"urls" : ["https://www.website.com/", "https://www.anotherwebsite.com"]})

print(rSetTest.status_code)
print(rSetTest.json())


in both cases, I get the a 400 status code error and the response is:

{'detail': 'There was an error parsing the body'}


I'm using python 3.10 on a linux ubuntu 22.04 vm with an ampere ARM processor if it matters...

I've also tried the following app code:

from fastapi import FastAPI
from pydantic import BaseModel

app = FastAPI()

class UrlsList(BaseModel):
urls: list[str]

class UrlsSet(BaseModel):
urls: set[str]

@app.post("/checkUrls")
async def checkUrls(urls: UrlsList):
return urls


@app.post("/checkUrlsSet")
async def checkUrlsSet(urls: UrlsSet):
return urls


which returns a 422 Unprocessable Entity error:

{'detail': [{'loc': ['body'], 'msg': 'value is not a valid list', 'type': 'type_error.list'}]}

{'detail': [{'loc': ['body'], 'msg': 'value is not a valid set', 'type': 'type_error.set'}]}

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