Getting AttributeError parsing JSON data

Question

I'm getting a JSON data from server and I need to parse it separately, when I do this with SimpleNamespace I get the problem. How can I parse this data?

Example Data:

{
  "version":"1.0",
  "packageName":"com.some.thing",
  "eventTimeMillis":"1503349566168",
  "subscriptionNotification":
  {
    "version":"1.0",
    "notificationType":4,
    "purchaseToken":"PURCHASE_TOKEN",
    "subscriptionId":"my.sku"
  }
}

My Code:

import json
from types import SimpleNamespace

def callback(message):
    x = json.loads(message.data, object_hook=lambda d: SimpleNamespace(**d))
    
    print("Version: " + x.version)
    print("Package Name: " + x.packageName)
    print("Time Milis: " + x.eventTimeMillis)
    print("Token: " + x.subscriptionNotification.purchaseToken)
    print("Product: " + x.subscriptionNotification.subscriptionId)
    print("Type: " + str(x.subscriptionNotification.notificationType))

Error:

AttributeError: 'types.SimpleNamespace' object has no attribute 'subscriptionNotification'

I tried your code based on your sample data and had no issues. I suspect the message passed to callback() is not quite what you thought it would be. Try print(message) in callback() — user2668284
– user2668284, Commented Oct 5, 2021 at 15:51
@BrutusForcus Yes sometimes some mixed data is coming from the server so it crashes. This code generally works fine but sometimes I get errors so I want to do it in a different way. How can I do this outside of SimpleNamespace? — dikitin
– dikitin, Commented Oct 5, 2021 at 15:58
Don't use SimpleNamespace - i.e., leave out object_hook. Then, to access the keys, use a traditional get() ideally with a default value - e.g., 'n/a' or None — user2668284
– user2668284, Commented Oct 5, 2021 at 16:05
@BrutusForcus I get an error when I try this. x = json.loads(message.data) print("Version: " + x.version) print("Package Name: " + x.packageName) print("Time Milis: " + x.eventTimeMillis) print("Token: " + x.subscriptionNotification.purchaseToken) print("Product: " + x.subscriptionNotification.subscriptionId) print("Type: " + str(x.subscriptionNotification.notificationType)) AttributeError: 'dict' object has no attribute 'version' — dikitin
– dikitin, Commented Oct 5, 2021 at 16:13
That's not surprising. I suggested you use get() but you decided against that advice — user2668284
– user2668284, Commented Oct 5, 2021 at 16:20

user2668284 · Accepted Answer · 2021-10-05 16:48:31Z

1

In this example, we start with a dictionary. From then on there's very little code and the whole thing becomes "table driven". For example, if your dictionary structure changes such that you add a new key to the top level then you just need to make a corresponding change to the L1 table. Hopefully this will give you some ideas on how to proceed:

D = {
    "version": "1.0",
    "packageName": "com.some.thing",
    "eventTimeMillis": "1503349566168",
    "subscriptionNotification":
    {
        "version": "1.0",
        "notificationType": 4,
        "purchaseToken": "PURCHASE_TOKEN",
        "subscriptionId": "my.sku"
    }
}


def doPrint(d, L):
    if d:
        for _l in L:
            print(f'{_l[0]}: {d.get(_l[1], "n/a")}')


L1 = [['Version', 'version'],
    ['Package Name', 'packageName'],
    ['Time Millis', 'eventTimeMillis']
]
L2 = [['Token', 'purchaseToken'],
    ['Product', 'subscriptionId'],
    ['Type', 'notificationType']
]

doPrint(D, L1)
doPrint(D.get('subscriptionNotification', None), L2)

answered Oct 5, 2021 at 16:48

user2668284

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2 Comments

dikitin Over a year ago

Your code works, thanks but I couldn't get it to work for my system. Can you help with this? I am getting the data in def callback(message)

dikitin Over a year ago

def callback(message):     D = json.loads(message.data)     print(D)      def doPrint(d, L):     if d:         for _l in L:             print(f'{_l[0]}: {d.get(_l[1], "n/a")}')     L1 = [['Version', 'version'],         ['Package Name', 'packageName'],         ['Time Millis', 'eventTimeMillis']     ]     L2 = [['Token', 'purchaseToken'],         ['Product', 'subscriptionId'],         ['Type', 'notificationType']     ]     doPrint(D, L1)     doPrint(D.get('subscriptionNotification', None), L2)

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