i'm trying to check existence of an hash_key in dynamodb with boto (i can not update my filed if exist) i've try with query
for i in self.table.query(hask_key=[value]):
print i['url']
But i miss an argument (???). I've try with scan but i need to check my hash_key, not attributes.
I've try with get_item but i cannot manage the response if hash_key does not exist.
Any advice?
I've play with redis and it have exist method.
Rather than doing a query operation, you should just attempt to retrieve the item using get_item. If it exists, the item will be returned. If not, the call will raise a DynamoDBKeyNotFoundError which you can catch. So, something like:
def exists(hash_key):
try:
item = self.table.get_item(hash_key=<hash key>...)
except boto.dynamodb.exceptions.DynamoDBKeyNotFoundError:
item = None
return item
would return None if the hash didn't exist and would return the item if it did exist.
Just ended up on this page after a google search. Here's a 2020 update:
The API behaviour has changed and is returning either 'the item' or 'nothing', but won't raise an exception: https://boto3.amazonaws.com/v1/documentation/api/latest/reference/services/dynamodb.html#DynamoDB.Client.get_item
Here is an example of how to use get_item to query for a single item: https://boto3.amazonaws.com/v1/documentation/api/latest/guide/dynamodb.html#getting-an-item
And this SOF answer addresses the specific problem of checking for the existence of an item in a DDB table: https://stackoverflow.com/a/48589589/512155
