Reading Json in python (Django)

Question

I'm using Django for my webapp. I'm sending a JSON data to my views but I'm not able to access Nodes and edges by calling decoded_data['nodes'] and it gives me :

'NoneType' object is not subscriptable

error message.

Here is how I send json to to my view:

var a={
            nodes:   thisGraph.nodes,
            edges: saveEdges
        };

    //send data to server
    $(document).ready(function(){
    function change(){
        $.ajax({
        type:"POST",
        url: "/",
        data: {'data': JSON.stringify(a)},
        dataType: "json",  
        success: function(){
        console.log("Ajax worked");
        $('#message').text("Ajax worked");
        },
        headers:{'X-CSRFToken': csrftoken}
    });

here is my view:

data = request.POST.get("data")
json_encoded = json.dumps(data) 
decoded_data = json.loads(json_encoded)
logger.error(decoded_data['nodes'])

the decoded_data looks like this:

{"nodes":[{"type":"node","title":"new concept","id":0,"x":658,"y":100},{"type":"
constraint","id":2,"title":"new Constraint","x":371,"y":95}],"edges":[{"source":
2,"target":0}]}

I appreciate your help

How does data look like? I tried running your code here with data={"nodes":[{"type":"node","title":"new concept","id":0,"x":658,"y":100},{"type":" constraint","id":2,"title":"new Constraint","x":371,"y":95}],"edges":[{"source": 2,"target":0}]} and there are no errors — t.pimentel
– t.pimentel, Commented Aug 14, 2014 at 22:08
Yes it works when I do what did but when I get it from POST.get("data") it doesn't work. request.POST looks like this: <QueryDict: {'data': ['{"nodes":[{"type":"node","title":"new concept","id":0,"x" :658,"y":100},{"type":"node","id":2,"title":"new Node","x":356,"y":85}],"edges": [{"source":2,"target":0}]}']}> — Hirad Roshandel
– Hirad Roshandel, Commented Aug 14, 2014 at 22:16
Does it really change between ' and "? How did you print this? print data? — t.pimentel
– t.pimentel, Commented Aug 14, 2014 at 22:21
Try this myDict = dict(data.iterlists()) and see what happens (It seems like you have a QueryDict stackoverflow.com/questions/13349573/… ) — t.pimentel
– t.pimentel, Commented Aug 14, 2014 at 22:23
I think you meant decoded_data = json.loads(json_encoded[0]) I did that it says Expecting value: line 1 column 1 (char 0) — Hirad Roshandel
– Hirad Roshandel, Commented Aug 14, 2014 at 23:01

tom.alexander · Accepted Answer · 2014-08-14 22:09:28Z

2

Change it to:

data = request.POST.get("data")
try:
    decoded_data = json.loads(data)
    nodes = decoded_data.get("nodes")
except:
    print("ERROR decoding")

request.POST.get("data") is a string. Just load it from there.

answered Aug 14, 2014 at 22:09

tom.alexander

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1 Comment

Hirad Roshandel Over a year ago

it says ERROR decoding

t.pimentel · Accepted Answer · 2014-08-15 01:34:15Z

'NoneType' is the type of None (Equivalent to Null in python) and should only appear if a variable was not correctly set, or if it was set as my_variable = None.

If data is a string equal to this:

data = '{"nodes":[{"type":"node","title":"new concept","id":0,"x":658,"y":100},{"type":" node","id":2,"title":"new Node","x":334,"y":60}],"edges":[{"source":2,"target":0 }]}'

Then simply using the following code should work:

decoded_data = json.loads(data)

Check if your requests are really coming from the AJAX request or if data == None like this:

data = request.POST.get("data")
if data === None:
    return "Error: not correctly formed request"
else:
    decoded_data = json.loads(data)
    nodes = decoded_data["nodes"]
    edges = decoded_data["edges"]

Hirad Roshandel · Accepted Answer · 2014-08-15 01:15:51Z

0

I found the problem! I was using this code in my "/" url and the first time this code was getting called data was Null so I had to check if the call was AJAX and use this code in that condition.

answered Aug 15, 2014 at 1:15

Hirad Roshandel

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