Why is reqparse not understanding the POST request?

Question

From what I've seen online, I can use reqparse from flask_restful to add data to my GET and POST requests.

Here is what I have:

from flask import Flask, request
from flask_restful import Resource, Api, reqparse
import pandas as pd
import ast

app = Flask(__name__)
api = Api(app)


class User(Resource):
    def get(self):
        return {'data': 'get'}, 200

    def post(self):
        parser = reqparse.RequestParser(bundle_errors=True)
        parser.add_argument('userId', type=str)
        args = parser.parse_args()

        print(args)
        return {'data': 'post'}, 200


class Game(Resource):
    pass


api.add_resource(User, '/user')
api.add_resource(Game, '/game')

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

I'm trying to send this POST request (using Postman):

http://127.0.0.1:5000/user?userId=hello

But I always get this error back:

{
    "message": "The browser (or proxy) sent a request that this server could not understand."
}

I truly don't know what I'm doing wrong...

Answer 1

I still have not figured out how to fix reqparse. However, I managed to get the result desired another way.

Basically you can change the api.add_resource() to include variables which you can pass into the class path. Like: api.add_resource(User, 'user/<userID>') allows you to send a request like http://127.0.0.1:5000/user/kayer and have the variable userID be kayer.

The other way (to go back to my original question on how to use this type of request: http://127.0.0.1:5000/user?userID=kayer is to implement reuest.args.get('userID') and assign the return of that function to a variable.

Full code:

from flask import Flask, request
from flask_restful import Resource, Api, reqparse
import pandas as pd
import ast

app = Flask(__name__)
api = Api(app)


class User(Resource):
    def get(self, userId):
        a = request.args.get('name')
        return {'data': {'a': userId, 'b': a}}, 200

    def post(self):
        pass


class Game(Resource):
    pass


api.add_resource(User, '/user/<userId>')
api.add_resource(Game, '/game')

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

Answer 2

I think the problem is that reqparse (or flask_restful itself), by default, is not parsing the query string (?userId=hello), when it matches the request URL with the endpoint.

From https://flask-restful.readthedocs.io/en/latest/reqparse.html#argument-locations:

By default, the RequestParser tries to parse values from flask.Request.values, and flask.Request.json.

Use the location argument to add_argument() to specify alternate locations to pull the values from. Any variable on the flask.Request can be used.

As instructed and from the example on that documentation, you can explicitly specify a location keyword param as location="args", where args refers to flask.Request.args, which means the:

The parsed URL parameters (the part in the URL after the question mark).

...which is exactly where userId is set when you call the endpoint.

It seems to work after adding the location="args" parameter:

def post(self):
    parser = reqparse.RequestParser(bundle_errors=True)
    parser.add_argument("userId", type=str, location="args")  # <--------
    args = parser.parse_args()
    print(args)
    return {"data": args}, 200

Postman:

cURL:

$ curl -XPOST http://localhost:5000/user?userId=hello
{
    "data": {
        "userId": "hello"
    }
}

---

Tested with:

• Flask 2.1.2
• Flask-RESTful 0.3.9