How does one automatically format a returned dynamodb item so that it can be put back into dynamodb-CodePudding

dynamodb yields an item in a string format:

cdb = boto3.client('dynamodb', region_name='us-west-2')
db = boto3.resource('dynamodb', region_name='us-west-2')
table = db.Table('my-table')
response = table.scan()
my_data = response['Items']
foo = my_data[0]
print(foo)

#  {'theID': 'fffff8f-dfsadfasfds-fsdsaf', 'theNumber': Decimal('1')}

Now, when I treat this like a black-box unit, do nothing, and return it to the db via put-item, I'll get many errors indicating none of the values in the dictionary are the expected type:

cdb.put_item(TableName='my-table', Item=foo, ReturnValues="ALL_OLD")

# many errors

I'd like to rely on boto3 to do everything and avoid manipulating the values if possible. Is there a utility available that will convert a response item into the format it needs to be to be placed back in the db?

CodePudding user response：

You should use your table resource to write items because you also use it to read.

Something like this should do the trick:

table.put_item(Item=foo, ReturnValues="ALL_OLD")

You're reading the data using the higher-level resource API, which maps many native Python Types to DynamoDB types, and trying to write using the lower-level client API, which doesn't do that.

The simple solution is also to use the resource-API to write, and it will perform the mappings.

(I'm inferring this based on your method signature for put_item, the question is not overly clear...)

CodePudding user response：

Apparently there is also a serializer that can be used:

from boto3.dynamodb.types import TypeSerializer