Question

您好希望连续添加到一个子项目，该子项目最初被声明为空，之后将被更新。

这是代码-

dynamodb = boto3.resource('dynamodb',endpoint_url='http://localhost:8000')
# Creating the Table
table = dynamodb.create_table(
            TableName='TableN',
            KeySchema=[
                           {
                           'AttributeName': 'name',
                           'KeyType': 'HASH'
                           }
                       ],
            AttributeDefinitions=[

                            {
                                'AttributeName': 'name',
                                'AttributeType': 'S'
                            }
                        ],
            ProvisionedThroughput={
                        'ReadCapacityUnits': 1000,
                        'WriteCapacityUnits': 1000
                        }
        )
# Updating with the Initial Values
table = dynamodb.Table('TableN')
IntValues = {
              "datapoints": [], 
               "attributes": {"host": "server1", "customer": "Ast1"}, 
                "name": "B001_P001"
             }

table.put_item(Item=IntValues)

现在，我想用一组值更新“数据点”-

datapoint1 = {"x1":1,"x2":"OK","x3":"23.123"}
datapoint2 = {"x1":3,"x2":"ON","x3":"56.123"}
datapoint3 = {"x1":5,"x2":"OFF","x3":"78.123"}

因此最终值应类似于-

{
    "name" : "B001_P001",
    "datapoints" : [
        {
          "x1" : 1,
          "x2" : "OK",
          "x3":"23.123"
        },
        {
          "x1" : 1,
          "x2" : "OK",
          "x3":"23.123"
        },
        {
          "x1" : 1,
          "x2" : "OK",
          "x3":"23.123"
        }]
        "attributes": {"host": "server1", "customer": "Ast1"}
}

如何在不删除或重新创建整个项目的情况下更新现有子项目？

Answer 1

我已使用update_item更新每个数据点-

在使用put_item创建了有问题的初始更新后，我使用了update_item来更新属性。

我已经使用for循环来传递各个数据点-

ulist = datapoint1     
table.update_item(
                  Key={'name':'TableN'},
                  UpdateExpression= 'SET #datapoints = list_append(#datapoints,:val1)',
                  ExpressionAttributeNames={'#datapoints': 'datapoints'},
                  ExpressionAttributeValues={':val1':ulist}
                 )

使用Python更新DynamoDB中项目中的子项目

1 个答案: