I have a simple Python tornado Websockets server, receives messages from JavaScript client. I am trying to send JSON data, the only solution I found is to convert the Json object into string Json, send it, on the other hand over the server I parse the string back to Json. Here is my Json file :

{
  "events": [
    {
      "id": 0,
      "new": {
        "description": "blabla bla keyyys",
        "keys": [
          "keyyys",
          "key "
        ],
        "start": "2.000000",
        "end": "7.000000",
        "priority": "normal"
      }
    },
    {
      "id": 1,
      "new": {
        "description": "anything key ",
        "keys": [
          "keyyys",
          "key "
        ],
        "start": "0.761077",
        "end": "10.026667",
        "priority": "high"
      }
    }
  ]
}

Before I send it I add another element to the Json:

var messageValue = {}; 
var sendings;
messageValue["messageType"] = "mainfest";
$.getJSON("file.json", function(json) {
    messageValue["data"]= json;
    console.log(messageValue);
    sendings =  jsonToStringConvertor(messageValue);
    });

var socket = new WebSocket('ws://localhost:9000/');

socket.onopen = function(event){
    socket.send(sendings);
}

. .

function jsonToStringConvertor(obj)
{
var re = JSON.stringify(obj);
return re;
}

I could receive the message from the server and print it:

So far good. but when I try to parse back to Json like this

JsonFormattedMessage = json.loads(message)[0]

I got this error:

ERROR:tornado.application:Uncaught exception in /
Traceback (most recent call last):
  File "/usr/local/lib/python3.4/dist-packages/tornado/websocket.py", line 494, in _run_callback
    result = callback(*args, **kwargs)
  File "index.py", line 27, in on_message
    JsonFormattedMessage = json.loads(message)[0]
KeyError: 0

I have a simple Python tornado Websockets server, receives messages from JavaScript client. I am trying to send JSON data, the only solution I found is to convert the Json object into string Json, send it, on the other hand over the server I parse the string back to Json. Here is my Json file :

{
  "events": [
    {
      "id": 0,
      "new": {
        "description": "blabla bla keyyys",
        "keys": [
          "keyyys",
          "key "
        ],
        "start": "2.000000",
        "end": "7.000000",
        "priority": "normal"
      }
    },
    {
      "id": 1,
      "new": {
        "description": "anything key ",
        "keys": [
          "keyyys",
          "key "
        ],
        "start": "0.761077",
        "end": "10.026667",
        "priority": "high"
      }
    }
  ]
}

Before I send it I add another element to the Json:

var messageValue = {}; 
var sendings;
messageValue["messageType"] = "mainfest";
$.getJSON("file.json", function(json) {
    messageValue["data"]= json;
    console.log(messageValue);
    sendings =  jsonToStringConvertor(messageValue);
    });

var socket = new WebSocket('ws://localhost:9000/');

socket.onopen = function(event){
    socket.send(sendings);
}

. .

function jsonToStringConvertor(obj)
{
var re = JSON.stringify(obj);
return re;
}

I could receive the message from the server and print it:

So far good. but when I try to parse back to Json like this

JsonFormattedMessage = json.loads(message)[0]

I got this error:

ERROR:tornado.application:Uncaught exception in /
Traceback (most recent call last):
  File "/usr/local/lib/python3.4/dist-packages/tornado/websocket.py", line 494, in _run_callback
    result = callback(*args, **kwargs)
  File "index.py", line 27, in on_message
    JsonFormattedMessage = json.loads(message)[0]
KeyError: 0

• javascript
• python
• json
• websocket
• tornado

Share Improve this question Follow edited Sep 21, 2017 at 7:42 Hussein asked Sep 21, 2017 at 7:34 HusseinHussein 68133 gold badges1111 silver badges2828 bronze badges 2

• 3 what do you mean json.loads(message)[0]? This message is absolutely a dictionary but not a list. – Sraw Commented Sep 21, 2017 at 7:43
• The KeyError indicates that the object does not have the specified Key. So you are trying to access a Key (which indicates that your variable is not a List but a dictionary) that does not exists. – Wouter Coebergh Commented Jun 27, 2018 at 14:38

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1 Answer 1

Sorted by: Reset to default 3

I think the message is not a list, but the JSON String itself. So you are trying to access an index on a string, that does no exist. Try just loading the string in the json.loads function: json.loads(message)