'NoneType' object is not subscriptable
flask, flask-restful, python, rest
Solution
You need to explicitly set the `content-type` to `application/json` for `request.json` to work properly in flask. If the header isn't set, `request.json` would return None.
But the recommended to get json data in flask from a post request is to use `request.get_json()`
I'll also urge you to test your api with the nifty requests module before using your `ios` application.
>>> import requests
>>> requests.post(url, json={'name': 'hello world'})
It already sets the appropriate headers required to make a `json` request
If it works with the `requests` module, then you can be sure that it's going to work with your ios application. you just need to make sure you're setting the correct `content-type`.
You can forcefully tell flask to ignore the `content-type` header with
`request.get_json(force=True)`
Problem
I am creating an ios app that uses a server written in flask + python, and when I make a connection to the server to register a user I keep getting a 'NoneType' object is not subscriptable error in my server.py file. Basically my question is what is causing this error and how am I able to fix this. Also if anyone can point me in the right direction of different or easier ways to do this I would appreciate it thanks! Here is the server.py file: ``` import bcrypt from flask import Flask, request, make_response,jsonify from flask_restful import Resource, Api from pymongo import MongoClient from json import JSONEncoder from bson.objectid import ObjectId from functools import wraps app = Flask(__name__) mongo = MongoClient('localhost', 27017) app.db = mongo.eventure_db app.bcrypt_rounds = 12 api = Api(app) # Authentication code. def check_auth(username, password): # check_auth should access the database and check if the username + password are correct. # create a collection to hold the users. user_collection = app.db.users user = user_collection.find_one({'username': username}) if user is None: return False else: # check if hash generated matches stored hash encodedPassword = password.encode('utf-8') if bcrypt.hashpw(encodedPassword, user['password']) == user['password']: return True else: return False # User resource class User(Resource): def post(self): if (request.json['username'] == None or request.json['password'] == None): return ({'error': 'Request requires username and password'}, 400, None) user_collection = app.db.users user = user_collection.find_one({'username': request.json['username']}) if user is not None: return ({'error': 'Username already in use'}, 400, None) else: encodedPassword = request.json['password'].encode('utf-8') hashed = bcrypt.hashpw( encodedPassword, bcrypt.gensalt(app.bcrypt_rounds)) request.json['password'] = hashed user_collection.insert_one(request.json) @requires_auth def get(self): return (None, 200, None) api.add_resource(User, '/eventure/api/v1.1/user/') # Must define a custom JSON Serializer for flask_restful # this is because ObjectId is not a string, and therefore, # Flask's default serializer cannot serialize it. @api.representation('application/json') def output_json(data, code, headers=None): resp = make_response(JSONEncoder().encode(data), code) resp.headers.extend(headers or {}) return resp if __name__ == '__main__': app.config['TRAP_BAD_REQUEST_ERRORS'] = True app.run(host='localhost', port=8789, debug=True) ``` And this is my register function in swift: ``` @IBAction func register(_ sender: AnyObject) { let url = URL(string: "http://localhost:8789/eventure/api/v1.1/user/") var request = URLRequest(url: url!) request.httpMethod = "POST" request.setValue(generateBasicAuthHeader(username: username.text!, password: password.text!), forHTTPHeaderField: "Authorization") let session = URLSession.shared let task = session.dataTask(with: request) { data, response, error in if let response = response, let data = data { print(String(data: data, encoding: String.Encoding.utf8)) } } task.resume() self.username.text = "" self.password.text = "" } ``` traceback: ``` [28/Oct/2016 19:22:33] "POST /eventure/api/v1.1/user/ HTTP/1.1" 500 - Traceback (most recent call last): File "/Users/Dynee/eventure-backend-api/development/lib/python3.5/site-packages/flask/app.py", line 1836, in __call__ return self.wsgi_app(environ, start_response) File "/Users/Dynee/eventure-backend-api/development/lib/python3.5/site-packages/flask/app.py", line 1820, in wsgi_app response = self.make_response(self.handle_exception(e)) File "/Users/Dynee/eventure-backend-api/development/lib/python3.5/site-packages/flask_restful/__init__.py", line 270, in error_router return original_handler(e) File "/Users/Dynee/eventure-backend-api/development/lib/python3.5/site-packages/flask/app.py", line 1403, in handle_exception reraise(exc_type, exc_value, tb) File "/Users/Dynee/eventure-backend-api/development/lib/python3.5/site-packages/flask/_compat.py", line 32, in reraise raise value.with_traceback(tb) File "/Users/Dynee/eventure-backend-api/development/lib/python3.5/site-packages/flask/app.py", line 1817, in wsgi_app response = self.full_dispatch_request() File "/Users/Dynee/eventure-backend-api/development/lib/python3.5/site-packages/flask/app.py", line 1477, in full_dispatch_request rv = self.handle_user_exception(e) File "/Users/Dynee/eventure-backend-api/development/lib/python3.5/site-packages/flask_restful/__init__.py", line 270, in error_router return original_handler(e) File "/Users/Dynee/eventure-backend-api/development/lib/python3.5/site-packages/flask/app.py", line 1381, in handle_user_exception reraise(exc_type, exc_value, tb) File "/Users/Dynee/eventure-backend-api/development/lib/python3.5/site-packages/flask/_compat.py", line 32, in reraise raise value.with_traceback(tb) File "/Users/Dynee/eventure-backend-api/development/lib/python3.5/site-packages/flask/app.py", line 1475, in full_dispatch_request rv = self.dispatch_request() File "/Users/Dynee/eventure-backend-api/development/lib/python3.5/site-packages/flask/app.py", line 1461, in dispatch_request return self.view_functions[rule.endpoint](**req.view_args) File "/Users/Dynee/eventure-backend-api/development/lib/python3.5/site-packages/flask_restful/__init__.py", line 471, in wrapper resp = resource(*args, **kwargs) File "/Users/Dynee/eventure-backend-api/development/lib/python3.5/site-packages/flask/views.py", line 84, in view return self.dispatch_request(*args, **kwargs) File "/Users/Dynee/eventure-backend-api/development/lib/python3.5/site-packages/flask_restful/__init__.py", line 581, in dispatch_request resp = meth(*args, **kwargs) File "/Users/Dynee/eventure-backend-api/server.py", line 128, in post if (request.json['username'] == None TypeError: 'NoneType' object is not subscriptable ``` Also here is the generateBasicAuthHeader function: ``` func generateBasicAuthHeader(username: String, password: String) -> String { let loginString = String(format: "%@:%@", username, password) let loginData = loginString.data(using: String.Encoding.utf8)! let base64LoginString = loginData.base64EncodedString() let basicAuthHeader = "Basic \(base64LoginString)" return basicAuthHeader } ```