Unable to post to flask restful endpoint with Python

Question

I've an endpoint which accepts JSON

api.add_resource(EventsList, '/events')

The Flask Restful / SQL Alchemy is:

class EventsList (Resource):
    #RETURNS ALL EVENTS
    def get(self):
        schema = EventSchema()
        result = db.session.query(EventModel).all()
        return schema.dump(result, many=True), 200

    #POSTS A SINGLE EVENT
    def post(self):

        title = request.json['title']
        date = request.json['date']

        event = EventModel(title=title,date=date)

        db.session.add(event)
        db.session.commit()

        data = ({'title': event.title,
                 'date': event.date})

        response = jsonify(data)
        response.status_code = 200
        return response

When using curl via the command line this works absolutely fine:

Curl Request

curl http://localhost:5002/events -H "Content-Type: application/json" -d '{"title": "TEst Event 3", "date":"2020-02-23"}'

Curl Response

The response contains the data as expected:

{"date":"Sun, 23 Feb 2020 00:00:00 GMT","title":"TEst Event 3"}

This all works fine. However, when I attempt to do this from Python I receive a server error.

Python

import importlib
import subprocess
import csv
import sys
import requests

targetWikiPage = input("Target Wiki Page: ")
eventTitle = input("Event Title: ")
eventDate = input("Event Date: ")

    
#POST AN EVENT
data = '{"title": "'+eventTitle+'","date":"'+eventDate+'"}'
print("SENDING EVENT DATA:")
print(requests.body)
print(requests.headers)

response = requests.post("http://localhost:5002/events", json=data)

Server Console Output

[2020-09-28 16:38:14,182] ERROR in app: Exception on /events [POST]
Traceback (most recent call last):
  File "/usr/local/lib/python3.8/site-packages/flask/app.py", line 1950, in full_dispatch_request
    rv = self.dispatch_request()
  File "/usr/local/lib/python3.8/site-packages/flask/app.py", line 1936, in dispatch_request
    return self.view_functions[rule.endpoint](**req.view_args)
  File "/usr/local/lib/python3.8/site-packages/flask_restful/__init__.py", line 468, in wrapper
    resp = resource(*args, **kwargs)
  File "/usr/local/lib/python3.8/site-packages/flask/views.py", line 89, in view
    return self.dispatch_request(*args, **kwargs)
  File "/usr/local/lib/python3.8/site-packages/flask_restful/__init__.py", line 583, in dispatch_request
    resp = meth(*args, **kwargs)
  File "api.py", line 155, in post
    title = request.json['title']
TypeError: string indices must be integers
127.0.0.1 - - [28/Sep/2020 16:38:14] "POST /events HTTP/1.1" 500 -

Any help is appreciated.

Answer 1

Fixed this.

The problem lay with how I was sending the data to the server. This is what I had:

targetWikiPage = input("Target Wiki Page: ")
eventTitle = input("Event Title: ")
eventDate = input("Event Date: ")

    
#POST AN EVENT
data = '{"title": "'+eventTitle+'","date":"'+eventDate+'"}'
print("SENDING EVENT DATA:")
print(requests.body)
print(requests.headers)

response = requests.post("http://localhost:5002/events", json=data)

Note that my requests.post had two values being passed. The url and the data.

The problems were as below:

1. The data was formatted incorrectly. This should have been:

data = json.dumps({"title": eventTitle, "date": eventDate})

2. I needed to add headers:

headers = {'Content-type': 'application/json', 'Accept': 'text/plain'}

3. I needed to pass a data value to the server, not json

requests.post("http://localhost:5002/events", headers=headers, data=data)

That changed my file to this:

targetWikiPage = input("Target Wiki Page: ")
eventTitle = input("Event Title: ")
eventDate = input("Event Date: ")

#POST AN EVENT
data = json.dumps({"title": eventTitle, "date": eventDate})
headers = {'Content-type': 'application/json', 'Accept': 'text/plain'}
print(data)
print(headers)
print("SENDING EVENT DATA:")

response = requests.post("http://localhost:5002/events", headers=headers, data=data)
json=json.loads(response.content)

Answer 2

You have JSON data in a string object. Trying to extract a value from the string via its key will produce the error you described

>>> response = '{"date":"Sun, 23 Feb 2020 00:00:00 GMT","title":"TEst Event 3"}'
>>> response_date = response["date"]
Traceback (most recent call last):
  File "<pyshell#1>", line 1, in <module>
    response_date = response["date"]
TypeError: string indices must be integers

You need to convert the string to a dict first, then extract the value

>>> import json
>>> response_as_json = json.loads(response)
>>> response_date = response_as_json["date"]
>>> response_date
'Sun, 23 Feb 2020 00:00:00 GMT'