无法使用python从AWS Dynamodbget_item？

Question

我是dynamodb的新手，尝试从dynamodb获取数据。

这是我的表，以“主题”为主要散列键

我的python代码

import boto3 
from boto3 import dynamodb 

from boto3.session import Session

from boto3.dynamodb.conditions import Key, Attr


dynamodb_session = Session(aws_access_key_id='XXXXXXXXXXXXXXX',
          aws_secret_access_key='XXXXXXXXXXXXXXXXXXXXXXXXXXXX',
          region_name='us-east-1')

dynamodb = dynamodb_session.resource('dynamodb')

table=dynamodb.Table('Garbage_collector_table')

my_topic = "$aws/things/garbage_collector_thing/shadow/update/accepted"

response = table.get_item(TableName='Garbage_collector_table', Key={'topic':my_topic})

for res in response: 
    print "result ",res

我得到以下错误

Traceback (most recent call last):
 File "get-data-dynamodb-boto3.py", line 19, in <module>
    response = table.get_item(TableName='Garbage_collector_table', Key={'topic': my_topic})   File
 "/usr/local/lib/python2.7/dist-packages/boto3/resources/factory.py",
 line 518, in do_action
     response = action(self, *args, **kwargs)   File "/usr/local/lib/python2.7/dist-packages/boto3/resources/action.py",
 line 83, in __call__
     response = getattr(parent.meta.client, operation_name)(**params)   File "/usr/local/lib/python2.7/dist-packages/botocore/client.py", line
 258, in _api_call
     return self._make_api_call(operation_name, kwargs)   File /usr/local/lib/python2.7/dist-packages/botocore/client.py", line 548,
 in _make_api_call
     raise ClientError(parsed_response, operation_name)

botocore.exceptions.ClientError:调用GetItem操作时发生错误（ValidationException）：提供的键元素与架构不匹配

我的代码中有什么遗漏吗？

Answer 1

假设表中只有分区键（又名散列键）。

import boto3
dynamodb = boto3.resource('dynamodb',region_name='ap-southeast-2')
table = dynamodb.Table('my-table')
key = {}
key['key'] = 'my-key'
print(key)
response = table.get_item(Key=key)
print(response['Item'])

Answer 2

您还可以查询数据库：

from boto3.dynamodb.conditions import Key

table = dynamodb.Table(table_name)
response = table.query(
    KeyConditionExpression=Key('topic').eq(my_topic)
)
items = response['Items']
if items:
    return items[0]
else:
    return []

来源：https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/GettingStarted.Python.04.html

Answer 3

您正在混合具有不同方法的资源对象和客户端对象。更多信息请点击这里。

资源的正确语法为：

response = table.get_item(Key={'topic': my_topic})

但我个人建议使用boto客户端：

client = boto3.client('dynamodb')

response = client.get_item(TableName='Garbage_collector_table', Key={'topic':{'S':str(my_topic)}})

http://boto3.readthedocs.io/en/latest/reference/services/dynamodb.html