Question

从一种方法我得到的输出低于

        {'Records': [{'messageId': '2953dfd5-d848-42b2-a60b-43df00ec8e5f', 
       'receiptHandle': 'AQEBPMr5RbW3T2DG4pAYi+', 'body': 
      'I am still trying', 'attributes': {'ApproximateReceiveCount': '1', 
        'SentTimestamp': '1552073955807', 'SenderId': '944198216610', 
        'ApproximateFirstReceiveTimestamp': '1552073955816'}, 
        'messageAttributes': {}, 'md5OfBody': 
         '2111a742ddbdac2d862fa6a204f7dc85', 'eventSource': 'aws:sqs', 
          'eventSourceARN': 'arn:aws:sqs:us-east- 
         1:944198216610:LambadaQueue', 'awsRegion': 'us-east-1'}]}

现在我想从中获取主体的值，所以我在下面使用了

body = event ['Records'] [0] [0] ['body']

但这无法正常工作。您能帮我弄清楚我在做什么错吗？

Answer 1

我在做什么错了？

Records键是一个列表，您可以使用该项目的索引号从列表中选择项目。

json_string = {
              "Records": [
    {
      "messageId": "2953dfd5-d848-42b2-a60b-43df00ec8e5f",
      "receiptHandle": "AQEBPMr5RbW3T2DG4pAYi+",
      "body": "I am still trying",
      "attributes": {
        "ApproximateReceiveCount": "1",
        "SentTimestamp": "1552073955807",
        "SenderId": "944198216610",
        "ApproximateFirstReceiveTimestamp": "1552073955816"
      },
      "messageAttributes": { },
      "md5OfBody": "2111a742ddbdac2d862fa6a204f7dc85",
      "eventSource": "aws:sqs",
      "eventSourceARN": "arn:aws:sqs:us-east-1:944198216610: LambadaQueue",
      "awsRegion": "us-east-1"
    }
  ]
}

因此，当您执行json_string['Records'][0]时，这会选择列表中的第一项，它也是字典：

{
  "messageId": "2953dfd5-d848-42b2-a60b-43df00ec8e5f",
  "receiptHandle": "AQEBPMr5RbW3T2DG4pAYi+",
  "body": "I am still trying",
 ....}

现在，如果您执行json_string['Records'][0][0]，则您正在尝试访问字典键，例如列表中的项（使用索引号0），这在语法上是不正确的。如果您想访问'messageId'的值，则可以按名称访问密钥，例如json_string['Records'][0]['messageId']，或者在您的问题中按如下方式访问“ body”键的值：

`json_string['Records'][0]['body']`

 #Output:
 I am still trying

Answer 2

您是否要获得“我还在尝试”？

json_data = {
  'Records': [{
    'messageId': '2953dfd5-d848-42b2-a60b-43df00ec8e5f',
    'receiptHandle': 'AQEBPMr5RbW3T2DG4pAYi+',
    'body': 'I am still trying',
    'attributes': {
        'ApproximateReceiveCount': '1',
        'SentTimestamp': '1552073955807',
        'SenderId': '944198216610',
        'ApproximateFirstReceiveTimestamp': '1552073955816'
    },
    'messageAttributes': {},
    'md5OfBody': '2111a742ddbdac2d862fa6a204f7dc85',
    'eventSource': 'aws:sqs',
    'eventSourceARN': 'arn:aws:sqs:us-east-1: 944198216610: LambadaQueue',
    'awsRegion': 'us - east - 1'
  }]
}

print (json_data['Records'][0]['body'])
# output
# I am still trying

Answer 3

如果您尝试获取“ body”元素的值，则看起来应该跳过查找中的第二个[0]。格式正确，看起来像这样：

{
  "Records": [
    {
      "messageId": "2953dfd5-d848-42b2-a60b-43df00ec8e5f",
      "receiptHandle": "AQEBPMr5RbW3T2DG4pAYi+",
      "body": "I am still trying",
      "attributes": {
        "ApproximateReceiveCount": "1",
        "SentTimestamp": "1552073955807",
        "SenderId": "944198216610",
        "ApproximateFirstReceiveTimestamp": "1552073955816"
      },
      "messageAttributes": { },
      "md5OfBody": "2111a742ddbdac2d862fa6a204f7dc85",
      "eventSource": "aws:sqs",
      "eventSourceARN": "arn:aws:sqs:us-east-1:944198216610: LambadaQueue",
      "awsRegion": "us-east-1"
    }
  ]
}

因此，要获取“记录”中第一条记录的“正文”字段的值，您应该这样做： body=event['Records'][0]['body']

从Json提取

3 个答案: