Question

我使用boto：

跟随python代码

import boto3

# Get the service resource.
dynamodb = boto3.resource('dynamodb', region_name='us-west-2')

# Instantiate a table resource object without actually
# creating a DynamoDB table. Note that the attributes of this table
# are lazy-loaded: a request is not made nor are the attribute
# values populated until the attributes
# on the table resource are accessed or its load() method is called.
table = dynamodb.Table('djin-dev-genesis')

def addtodatabase(appname, chef_max, arp_score):

    response = table.get_item(Key={'appname': str(appname)})
    if 'Item' not in response.keys():
        print "partititon key (appname) not found, creating a new item in dynamo db with the key"
        table.put_item(
           Item={
                'appname': appname,
                'chef_max': True,
                'arp_score': '110'
            }
        )
    else:
        print "partition key = "+str(appname)+" found, here is the item dict : "+str(response['Item'])

我希望在else场景中查看（如果键存在），是否已存在任何属性值且匹配。在那种情况下，我想失败的理由，否则更新属性。

boto中的代码是什么？

Answer 1

在像attribute_not_exists(appname)这样的PutItem调用中使用条件表达式，只允许创建项目（如果该项目尚不存在）。捕获ConditionalCheckFailedException，否则使用GetItem获取项目。

检查dynamo db表是否存在属性，如果属性存在则因为原因而失败 - boto

1 个答案: