Messenger Send API - python-3.x

Question

I am creating a self built Python chatbot that does not use a chatbot platform such as Dialogflow. The issue is that there is no easy integration with messaging apps such as Messenger to connect it too. I am trying to create a webhook to Messenger using the Messenger Send API. I am looking at the documentation and it shows me how to request a POST api call. However when I look at examples online they all seem to deal with json values called "entry" and "messaging" which I can't find anywhere and can't seem to see why it is necessary. I was wondering how exactly the input body of a Messenger Send API looks like so I can call it appropriately and what json objects are in its body. This is what I have so far from following online examples. I am using Flask. And am using Postman to test this
#app.route("/webhook", methods=['GET','POST'])
def listen():
if request.method == 'GET':
return verify_webhook(request)
if request.method == 'POST':
payload = request.json
event = payload['entry'][0]['messaging']
for x in event:
if is_user_message(x):
text = x['message']['text']
sender_id = x['sender']['id']
respond(sender_id, text)
return "ok"
Below is what I think the body of the request looks like:
{
"object":"page",
"entry":[
{
"id":"1234",
"time":1458692752478,
"messaging":[
{
"message":{
"text":"book me a cab"
},
"sender":{
"id":"1234"
}
}
]
}
]
}
But it is unable to read this and gives me an error of:
File"/Users/raphael******/Documents/*****_Project_Raphael/FacebookWebHookEdition.py", line 42, in listen
event = payload['entry'][0]['messaging']
TypeError: 'NoneType' object is not subscriptable
Where am I going wrong that the webhook is not registering the body correctly as json objects?

Answer 1

Here is how we do it:
# GET: validate facebook token
if request.method == 'GET':
valid = messenger.verify_request(request)
if not valid:
abort(400, 'Invalid Facebook Verify Token')
return valid
# POST: process message
output = request.get_json()
if 'entry' not in output:
return 'OK'
for entry in output['entry']:
if 'messaging' not in entry:
continue
for item in entry['messaging']:
# delivery notification (skip)
if 'delivery' in item:
continue
# get user
user = item['sender'] if 'sender' in item else None
if not user:
continue
else:
user_id = user['id']
# handle event
messenger.handle(user_id, item)
# message processed
return 'OK'
EDIT:
If you are using postman, please make sure to also set Content-Type header to application/json, otherwise Flask can't decode it with request.json. I guess that's where None comes from in your case.