Python: FastAPI error 422 with post request

Question

I'm building a simple API to test a database. When I use get request everything works fine, but if I change to post I get "unprocessable entity" error:

Here is FastAPI code:

from fastapi import FastAPI

app = FastAPI()

@app.post("/")
def main(user):
    return user

Then, my request using javascript

let axios = require('axios')

data = { 
    user: 'smith' 
}

axios.post('http://localhost:8000', data)
    .then(response => (console.log(response.url)))

And using Python

import requests

url = 'http://127.0.0.1:8000'
data = {'user': 'Smith'}

response = requests.post(url, json=data)
print(response.text)

I also try to parse as json, enconding using utf-8, and change the headers. Nothing as worked for me.

Answer 1

Straight from the documentation:

The function parameters will be recognized as follows:

• If the parameter is also declared in the path, it will be used as a path parameter.
• If the parameter is of a singular type (like int, float, str, bool, etc) it will be interpreted as a query parameter.
• If the parameter is declared to be of the type of a Pydantic model, it will be interpreted as a request body."

So to create a POST endpoint that receives a body with a user field you would do something like:

from fastapi import FastAPI
from pydantic import BaseModel


app = FastAPI()


class Data(BaseModel):
    user: str


@app.post("/")
def main(data: Data):
    return data