Lambda 错误“TypeError：'str' 对象不支持项目分配 Traceback”答案

【问题标题】：Lambda error "TypeError: 'str' object does not support item assignment Traceback"Lambda 错误“TypeError：'str' 对象不支持项目分配 Traceback”
【发布时间】：2021-02-16 00:20:35
【问题描述】：

我正在尝试

import json
import uuid
import boto3

def lambda_handler(event, context):
    
    dynamo_client = boto3.resource('dynamodb')
    loadeo_carrier_company = dynamo_client.Table('loadeo_carrier_company')
    
    
    item = {}
    item = event['body']
    print(item)
    item['company_id'] = str(uuid.uuid4())
    
    print (type(item))
    try:
        loadeo_carrier_company.put_item(
          
            Item=item
        )
        return {
            "statusCode": 200,
            "headers" : {
                "Access-Control-Allow-Origin" : "*"
            },
            "message": json.dumps("Record has been inserted"),
            "body": item
        }
    except Exception as e:
            return {
                "statusCode": 500,
                "headers" : {
                    "Access-Control-Allow-Origin" : "*"
                },
                "message": "Error: Unable to save record!"
            }

这段代码。

当我通过 Lambda 测试事件对其进行测试时，它工作正常。但是当我创建一个 API 并使用 postman 尝试它时显示内部服务器错误但是当我查看云监视日志时显示以下错误。

    [ERROR] TypeError: 'str' object does not support item assignment
Traceback (most recent call last):
  File "/var/task/lambda_function.py", line 19, in lambda_handler
    item['company_id'] = str(uuid.uuid4())

注意： Lambda 测试事件运行良好。

"body": {
  "company_name" : "waveaxis pvt ltd",
  "mc_number" : "00000",
  "email_adderess": "waveaxis@waveaxis.co.in",
  "phone_number" : "+91 1234567890",
  "company_address" : "Kormangala, Bengaluru"

尝试答案后：

当我从 lambda 测试事件中测试它时：

   {
  "errorMessage": "the JSON object must be str, bytes or bytearray, not dict",
  "errorType": "TypeError",
  "stackTrace": [
    "  File \"/var/task/lambda_function.py\", line 17, in lambda_handler\n    item = json.loads(event['body'])\n",
    "  File \"/var/lang/lib/python3.8/json/__init__.py\", line 341, in loads\n    raise TypeError(f'the JSON object must be str, bytes or bytearray, '\n"
  ]
}

当我从邮递员那里打电话时。在没有错误的try块之前执行停止

编辑 2：打印事件的 json

{
   "resource":"/",
   "path":"/",
   "httpMethod":"PUT",
   "headers":{
      "Accept":"*/*",
      "Accept-Encoding":"gzip, deflate, br",
      "Authorization":"Bearer eyJraWQiOiJCUUl6ZkxcL1VOdm9QTDVxNExlWGFRNXNxOG1mVmhmXC9rK3ZJUDdYc0p0VjQ9IiwiYWxnIjoiUlMyNTYifQ.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.XMy9GP03o5EYrcLtQFzrMV6KID4IlDI_n0WrHa8osY_7CeeDjaCjH6Dtr766TAommLUzcLoKt-NrBUdq0Zfx-BL919j25rwiZXJbHiZP_4y9n891ddOXfPabO7n8O84-63W6l13QEBozuc21vXi7vuE_dSJ7KAgute46KP3LyoS73WPDhYim_7HZJO8pVedk64hhGNZsYWv6VU5QeQyqPl926spA25ZBo_z5dcoBnMZ_i2n5nz6qxRcINOKfMXL1f4_nDRbtKb5Pd33hKnsKYLkxEI0mrT1JKPJhkJRg9vGqaKcd13oqrigJRFSXYuVQuKNDluc38KbQJcwUoXDjjA",
      "Content-Type":"application/json",
      "Host":"661ny3iw92.execute-api.us-east-2.amazonaws.com",
      "Postman-Token":"654cfdd0-8080-48a5-8758-3aa7e5bcefcc",
      "User-Agent":"PostmanRuntime/7.26.5",
      "X-Amzn-Trace-Id":"Root=1-5fa13860-63da2718701bf3fc458c78e1",
      "X-Forwarded-For":"157.49.141.105",
      "X-Forwarded-Port":"443",
      "X-Forwarded-Proto":"https"
   },
   "multiValueHeaders":{
      "Accept":[
         "*/*"
      ],
      "Accept-Encoding":[
         "gzip, deflate, br"
      ],
      "Authorization":[
         "Bearer eyJraWQiOiJCUUl6ZkxcL1VOdm9QTDVxNExlWGFRNXNxOG1mVmhmXC9rK3ZJUDdYc0p0VjQ9IiwiYWxnIjoiUlMyNTYifQ.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.XMy9GP03o5EYrcLtQFzrMV6KID4IlDI_n0WrHa8osY_7CeeDjaCjH6Dtr766TAommLUzcLoKt-NrBUdq0Zfx-BL919j25rwiZXJbHiZP_4y9n891ddOXfPabO7n8O84-63W6l13QEBozuc21vXi7vuE_dSJ7KAgute46KP3LyoS73WPDhYim_7HZJO8pVedk64hhGNZsYWv6VU5QeQyqPl926spA25ZBo_z5dcoBnMZ_i2n5nz6qxRcINOKfMXL1f4_nDRbtKb5Pd33hKnsKYLkxEI0mrT1JKPJhkJRg9vGqaKcd13oqrigJRFSXYuVQuKNDluc38KbQJcwUoXDjjA"
      ],
      "Content-Type":[
         "application/json"
      ],
      "Host":[
         "661ny3iw92.execute-api.us-east-2.amazonaws.com"
      ],
      "Postman-Token":[
         "654cfdd0-8080-48a5-8758-3aa7e5bcefcc"
      ],
      "User-Agent":[
         "PostmanRuntime/7.26.5"
      ],
      "X-Amzn-Trace-Id":[
         "Root=1-5fa13860-63da2718701bf3fc458c78e1"
      ],
      "X-Forwarded-For":[
         "157.49.141.105"
      ],
      "X-Forwarded-Port":[
         "443"
      ],
      "X-Forwarded-Proto":[
         "https"
      ]
   },
   "queryStringParameters":"None",
   "multiValueQueryStringParameters":"None",
   "pathParameters":"None",
   "stageVariables":"None",
   "requestContext":{
      "resourceId":"529nsbfu6a",
      "resourcePath":"/",
      "httpMethod":"PUT",
      "extendedRequestId":"VbW_FFkYCYcF3PQ=",
      "requestTime":"03/Nov/2020:11:00:48 +0000",
      "path":"/dev",
      "accountId":"272075499248",
      "protocol":"HTTP/1.1",
      "stage":"dev",
      "domainPrefix":"661ny3iw92",
      "requestTimeEpoch":1604401248435,
      "requestId":"970dd9d2-9b35-45c5-b194-806060e27d10",
      "identity":{
         "cognitoIdentityPoolId":"None",
         "accountId":"None",
         "cognitoIdentityId":"None",
         "caller":"None",
         "sourceIp":"157.49.141.105",
         "principalOrgId":"None",
         "accessKey":"None",
         "cognitoAuthenticationType":"None",
         "cognitoAuthenticationProvider":"None",
         "userArn":"None",
         "userAgent":"PostmanRuntime/7.26.5",
         "user":"None"
      },
      "domainName":"661ny3iw92.execute-api.us-east-2.amazonaws.com",
      "apiId":"661ny3iw92"
   },
   "body":"{\r\n    \"company_name\": \"waveaxis pvt ltd\",\r\n    \"mc_number\": \"00000\",\r\n    \"email_adderess\": \"waveaxis@waveaxis.co.in\",\r\n    \"phone_number\": \"+91 1234567890\",\r\n    \"company_address\": \"Kormangala, Bengaluru\"\r\n}\r\n",
   "isBase64Encoded":False
}

【问题讨论】：

标签： python-3.x amazon-web-services aws-lambda postman aws-api-gateway

【解决方案1】：

据我所知，您的 event['body'] 可能只是一个 json 字符串，而不是真正的 json。

因此，而不是

item = event['body']

你可以使用

item = json.loads(event['body'])

应该将 json 字符串解析为 json 对象。

更新

根据event 的发布形式，您应该使用ast，而不是json

import ast

item = ast.literal_eval(event['body'])

【讨论】：

@sumanthshetty 您是否在测试活动中运行过它？应该通过api网关有效。
我把它跑完了。 API 网关仍然显示内部服务器错误
@sumanthshetty 你能print(event) 并在 cloudwatch 日志中检查它的结构吗？
已将其添加到问题中
@sumanthshetty 不起作用，因为 API 网关事件和您的测试事件不同。您已将测试事件设置为与 API 网关中的事件相同的格式。顺便说一句，如果答案有帮助，我们将不胜感激。