Flask / Python API : TypeError: exceptions must derive from BaseException

Question

I am making my first Python/Flask API. I am currently working on my post request that should take in a JSON object that looks like the following. Every value should be either an integer or null based off user input.

{
  "FIDE": {
    "standard": 1555,
    "rapid": 1500,
    "blitz": null
  },
  "USCF": {
    "regular": null,
    "quick": null,
    "blitz": null
  },
  "Chesscom": {
    "bullet": null,
    "blitz": 1556,
    "rapid": 1601,
    "daily": null,
    "puzzle": null
  },
  "LiChess": {
    "bullet": null,
    "blitz": null,
    "rapid": null,
    "classical": null,
    "correspondence": null,
    "training": null
  }
}

That input should then hit this basic flask app. I should note that I just created the model and I'm not sure if I'm handling an object with a depth greater than one correctly.

from flask import Flask , request, redirect, url_for, Response
from flask_sqlalchemy import SQLAlchemy
import json

app = Flask(__name__)

db= SQLAlchemy(app)

class Player(db.model):
    __tablename__ = 'Players'
    id = db.Column(db.Integer, primary_key=True)
    FIDE.standard(db.Integer, nullable = True)
    FIDE.rapid(db.Integer, nullable = True)
    FIDE.blitz(db.Integer, nullable = True)
    USCF.regular(db.Integer, nullable = True)
    USCF.quick(db.Integer, nullable = True)
    USCF.blitz(db.Integer, nullable = True)
    Chesscom.bullet(db.Integer, nullable = True)
    Chesscom.blitz(db.Integer, nullable = True)
    Chesscom.rapid(db.Integer, nullable = True)
    Chesscom.daily(db.Integer, nullable = True)
    Chesscom.puzzle(db.Integer, nullable = True)
    Lichess.bullet(db.Integer, nullable = True)
    Lichess.blitz(db.Integer, nullable = True)
    Lichess.rapid(db.Integer, nullable = True)
    Lichess.correspondence(db.Integer, nullable = True)
    Lichess.training(db.Integer, nullable = True)
    

@app.route('/')
def index():
    return 'Hello David'

@app.route('/add', methods = ['POST'])
def add(Player):
    request_data= Player.getjson()
    response = Response(request_data.FIDE.standard, status=200, mimetype='application/json')
    return response

When I send a request to Postman I get an error message back saying

TypeError: exceptions must derive from BaseException

I believe, this is the relevant part of the error message, but I could be wrong. I will indclude the full error below. However, does anyone know what I am doing wrong within my app.py file?

Here is the full error message

Traceback (most recent call last):
  File "C:\Users\dreke\Documents\coding\sideProject\chess-backend\venv\Lib\site-packages\flask\cli.py", line 354, in __call__
    self._flush_bg_loading_exception()
  File "C:\Users\dreke\Documents\coding\sideProject\chess-backend\venv\Lib\site-packages\flask\cli.py", line 342, in _flush_bg_loading_exception
    raise exc_info
TypeError: exceptions must derive from BaseException

Answer 1

If you are passing the JSON as a raw data in the body as a POST request then the following code should work -

from flask import Flask, request, redirect, url_for, Response
from flask_sqlalchemy import SQLAlchemy

app = Flask(__name__)


@app.route('/')
def index():
    return 'Hello David'

@app.route('/add', methods = ['POST'])
def add():
    request_data = request.get_json()
    # You can make any change or operation using the request_data
    return request_data

if __name__ == '__main__':
    app.run(debug=True)

If you are passing as form data then replace request_data = request.get_json() with request_data= request.form and it shall do the job.

In order to use SQLAlchemy operations, following changes might be required for it to work -

from flask import Flask, request, redirect, url_for, Response
from flask_sqlalchemy import SQLAlchemy

app = Flask(__name__)

### Assuming you are using MySQL DB
app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = False
app.config['SQLALCHEMY_DATABASE_URI'] = 'mysql://username:password@localhost/db_name'

db= SQLAlchemy(app)


class Player(db.Model):

    __tablename__ = 'Players'

    id                     = db.Column(db.Integer, primary_key=True, autoincrement=True)
    FIDE_standard          = db.Column(db.Integer, nullable = True)
    FIDE_rapid             = db.Column(db.Integer, nullable = True)
    FIDE_blitz             = db.Column(db.Integer, nullable = True)
    USCF_regular           = db.Column(db.Integer, nullable = True)
    USCF_quick             = db.Column(db.Integer, nullable = True)
    USCF_blitz             = db.Column(db.Integer, nullable = True)
    Chesscom_bullet        = db.Column(db.Integer, nullable = True)
    Chesscom_blitz         = db.Column(db.Integer, nullable = True)
    Chesscom_rapid         = db.Column(db.Integer, nullable = True)
    Chesscom_daily         = db.Column(db.Integer, nullable = True)
    Chesscom_puzzle        = db.Column(db.Integer, nullable = True)
    Lichess_bullet         = db.Column(db.Integer, nullable = True)
    Lichess_blitz          = db.Column(db.Integer, nullable = True)
    Lichess_rapid          = db.Column(db.Integer, nullable = True)
    Lichess_correspondence = db.Column(db.Integer, nullable = True)
    Lichess_training       = db.Column(db.Integer, nullable = True)


@app.route('/')
def index():
    return 'Hello David'

@app.route('/add', methods = ['POST'])
def add():

    request_data= request.get_json()
    
    new_player = Player(
        FIDE_standard          = request_data.get('FIDE').get('standard'),
        FIDE_rapid             = request_data.get('FIDE').get('rapid'),
        FIDE_blitz             = request_data.get('FIDE').get('blitz'),
        USCF_regular           = request_data.get('USCF').get('regular'),
        USCF_quick             = request_data.get('USCF').get('quick'),
        USCF_blitz             = request_data.get('USCF').get('blitz'),
        Chesscom_bullet        = request_data.get('Chesscom').get('bullet'),
        Chesscom_blitz         = request_data.get('Chesscom').get('blitz'),
        Chesscom_rapid         = request_data.get('Chesscom').get('rapid'),
        Chesscom_daily         = request_data.get('Chesscom').get('daily'),
        Chesscom_puzzle        = request_data.get('Chesscom').get('puzzle'),
        Lichess_bullet         = request_data.get('Lichess').get('bullet'),
        Lichess_blitz          = request_data.get('Lichess').get('blitz'),
        Lichess_rapid          = request_data.get('Lichess').get('rapid'),
        Lichess_correspondence = request_data.get('Lichess').get('correspondence'),
        Lichess_training       = request_data.get('Lichess').get('training'),
    )

    db.session.add(new_player)
    db.session.commit()

    return request_data

if __name__ == '__main__':
    app.run(debug=True)

Answer 2

I believe this is a Flask issue as you can see in The following PR: https://github.com/pallets/flask/pull/4169 .

The PR is not merged yet so you'll have to use https://github.com/Rohan-Salwan/flask/tree/dev or wait until a version of Flask is release with the merged PR.