Getting error 422 "Unprocessable Entity" in my FastAPI / Python demo API

Question

I'm relatively new to Python and I'm working on a demo backend project which is a users API in with FastAPI.

My API is connected to a MongoDB database to save the data.

I'm seeing this error on postman when I try to add a new user:

This is my model class for User:

from typing import Optional
from pydantic import BaseModel


class User(BaseModel):
    id: Optional[str]  # Optional and str for mongo
    username: str
    email: str

And this is the logic in my endpoint to create the new User:

@router.post("/", response_model=User, status_code=status.HTTP_201_CREATED)  # status_code = default code if OK
async def create_user(new_user: User):
    # if user is found in the database, raise an exception
    if type(search_user("email", new_user.email)) == User:
        raise HTTPException(status_code=status.HTTP_409_CONFLICT, detail="User already exists.")
    # else, create the user
    new_user_dict = dict(new_user) 
    del new_user_dict["id"]
    user_id = db_client.users.insert_one(new_user_dict).inserted_id 
    transformed_user = user_schema(db_client.users.find_one({"_id": user_id}))
    return User(**transformed_user)

I already compared line by line the code from my tutor, and I see no differences but mine does not work... can somebody help me solve this problem? By the way... Im using Python 3.11..

Answer 1

Thanks, everyone for your comments, I found that the problem was being generated in an auxiliary function (search_user). I was not handling correctly, the case where the id is None like many of you mentioned here... I'm closing the question, thanks again!