How to check JSON key/object exist in python

Question

I'm very new to python. Is there anyway to check specific JSON object exist in python except my following code? Admit that my following code will not be good practice so need to know which way to better to check and easy to maintain?

Here is JSON response:

[
  {
    "MessageId": "250e37a8-d779-48a1-9941-84219a82513e",
    "ReceiptHandle": "AQEBjualXe2ywqTgIVmCNI5sKj7r48werf84HHA2BWZimwiEXLFxA/MiPBclK048NZBtOnM3dSDfoiwwqoNTPxTRz+IChd8McziweCxHX6texjAOi/MyAQjCWP+2hJPoxzQgXx9kjnKbepKlcgxhpOiQZe6WiSIq0dXwHHXSA7SP0g9NIR/dU38b+wmo0m2q7MNVfSct967EKF49wow9RHyFMO8iD8fH93PYT9om5NdUha3dvkWnisKcfuO5pZY3LLXPAnuZT/VfqxJjmPqb98iepBfqFb6SpM/02IVSql81XKJEbMBc4zPHp/Uace6e4UDGsn/hPCVsqQsTzrbKCR+ovpkhXipWwTYSlgsLe/o43k0UxhCN8eKhg835KuUkskA3T8C5Q6v6xgznlR7JJuhZpg==",
    "MD5OfBody": "bbdc5fdb8be7251f5c910905db994bab",
    "Body": "Information about current NY Times fiction bestseller for week of 12/11/2016.",
    "Attributes": {
      "SentTimestamp": "1553851566164"
    },
    "MD5OfMessageAttributes": "d25a6aea97eb8f585bfa92d314504a92",
    "MessageAttributes": {
      "Author": {
        "StringValue": "John Grisham",
        "DataType": "String"
      },
      "Title": {
        "StringValue": "The Whistler",
        "DataType": "String"
      },
      "WeeksOn": {
        "StringValue": "6",
        "DataType": "Number"
      }
    }
  }
]

and here is my python code to check:

if 'Messages' in response:
    message = response['Messages'][0]
    receipt_handle = message['ReceiptHandle']

    sqs.delete_message(
        QueueUrl=queue_url,
        ReceiptHandle=receipt_handle
    )
    print('Received and deleted message: %s' % message)
else:
    print('Message not received yet')

Please let me know above code is good practice or not.

Answer 1

Another option that you can checkout and one that i actually prefer when i am using JSON data, is to create an object out of the JSON data and use the hasattr method. This will prevent that you start over-using try-except blocks and can also make your code more understandable. An example using your data is the following:

data= '''
  {
"MessageId": "250e37a8-d779-48a1-9941-84219a82513e",
"ReceiptHandle": "AQEBjualXe2ywqTgIVmCNI5sKj7r48werf84HHA2BWZimwiEXLFxA/MiPBclK048NZBtOnM3dSDfoiwwqoNTPxTRz+IChd8McziweCxHX6texjAOi/MyAQjCWP+2hJPoxzQgXx9kjnKbepKlcgxhpOiQZe6WiSIq0dXwHHXSA7SP0g9NIR/dU38b+wmo0m2q7MNVfSct967EKF49wow9RHyFMO8iD8fH93PYT9om5NdUha3dvkWnisKcfuO5pZY3LLXPAnuZT/VfqxJjmPqb98iepBfqFb6SpM/02IVSql81XKJEbMBc4zPHp/Uace6e4UDGsn/hPCVsqQsTzrbKCR+ovpkhXipWwTYSlgsLe/o43k0UxhCN8eKhg835KuUkskA3T8C5Q6v6xgznlR7JJuhZpg==",
"MD5OfBody": "bbdc5fdb8be7251f5c910905db994bab",
"Body": "Information about current NY Times fiction bestseller for week of 12/11/2016.",
"Attributes": {"SentTimestamp": "1553851566164"},
"MD5OfMessageAttributes": "d25a6aea97eb8f585bfa92d314504a92",
"MessageAttributes": {"Author": {"StringValue": "John Grisham","DataType": "String"},"Title": {"StringValue": "The Whistler","DataType": "String"},"WeeksOn": {"StringValue": "6","DataType": "Number"}}
  } '''

import json

class Response:

    def __init__(self, data):
        self.__dict__ = json.loads(data)

response = Response(data)

if hasattr(response , 'MessageId'):
    receipt_handle = response.ReceiptHandle
    print("Received and deleted message: %s" % response.MessageId)

else:
    print('Message not received yet')

Output:

Received and deleted message: 250e37a8-d779-48a1-9941-84219a82513e