How to convert from DynamoDB wire protocol to native Python object manually with boto3?

Question

I have a Lambda that is being triggered by a DynamoDB stream. The Lambda does some processing and then creates a notification on a topic in SNS. Ideally I would like to includ

Answer 1

Using TypeDeserializer didn't work for me for some reason. This utility did, however:

https://github.com/Alonreznik/dynamodb-json

Those not wanting to deal with emulating pip install inside a Lambda function, you can just copy and paste this source file (containing the loads() function) into your own code:

https://github.com/Alonreznik/dynamodb-json/blob/master/dynamodb_json/json_util.py

Answer 2

I have a similar situation and I used the following an approach like this:

from boto3.dynamodb.types import TypeDeserializer

deser = TypeDeserializer()

...
<in handler>
    for record in event['Records']:
        old = record['dynamodb'].get('OldImage')
        new = record['dynamodb'].get('NewImage')
        if old:
            d = {}
            for key in old:
                d[key] = deser.deserialize(old[key])

This approach works for me. The resulting dictionary d contains the converted object rather than the wire-format version passed to the handler.