python - 如何检查python中是否存在JSON键/对象

Question

我是 python 的新手。除了我的以下代码之外，是否还有检查 python 中是否存在特定 JSON 对象的方法？承认我的以下代码不是好的做法，因此需要知道哪种方法更易于检查和维护？

这是 JSON 响应:

[
  {
    "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"
      }
    }
  }
]

这是我要检查的 python 代码:

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')

请让我知道上面的代码是否是好的做法。

Answer 1

您可以检查的另一个选项，也是我在使用 JSON 数据时实际上更喜欢的选项，是从 JSON 数据创建一个对象并使用 hasattr 方法。这将防止您开始过度使用 try-except block ，还可以使您的代码更易于理解。使用您的数据的示例如下:

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')

输出:

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