使用 boto3 获取特定用户 ID

Question

I am running a script which essentially will look for the user's "invitation_id" in my dynamo db table. I am essentially writing a try and catch block where I want it to spit out an error if the invitation_id does not exist. It seems to not spit out ValueError when it should be. Am not sure whether what am doing is correct or not. My script is as follows:

@staticmethod
 def search_delegate():

    CLIENT.get_item(
                    TableName="invtable",
                    Key={
                        'invitation_id': {
                            'S': '123'
                        }
                    }
                )


if __name__ == '__main__':

try:
    AWSDynamoUtils.search_delegate()
    print("Found user")
except:
    raise ValueError

Answer 1

From boto3 documentation:

The GetItem operation returns a set of attributes for the item with the given primary key. If there is no matching item, GetItem does not return any data and there will be no Item element in the response.

Since get_item does not return anything or does not raise any exceptions if invitation id is not in the table, your try statement executes successfully. Try implementing a check to see if if there are any records returned otherwise raise exception.

entry = AWSDynamoUtils.search_delegate()
if entry:
    print('Found User')
else:
    raise ValueError

Answer 2

As per boto3 documentation for dynamodb GetItem operation:

The GetItem operation returns a set of attributes for the item with the given primary key. If there is no matching item, GetItem does not return any data and there will be no Item element in the response.

Thus there won't be any exception raised in case there is no matching invitation_id. However, the "Item" element will not be present in the response. You can check on the response and raise the "Value Error" in case Item element is not present.

@staticmethod
 def search_delegate():

    return CLIENT.get_item(
                    TableName="invtable",
                    Key={
                        'invitation_id': {
                            'S': '123'
                        }
                    }
                )


if __name__ == '__main__':

response = AWSDynamoUtils.search_delegate()
if "Item" in response:
    print('Found User')
else:
    raise ValueError