Parse lambda event json to object using python

Question

in the event of lambda i am getting new and old images for any update in dynamo db .now in my new image have one property names as sourceDetails which can vary eg.(please note the string mentioned below is json

{'M': {'bucketName': {'S': 'postote-offers-bucket'}}}

or it be like for eg.

 {'M': {'streamName': {'S': 'someStream'},{'limit': {'N': 10}}}

How can i parse this result in best possible way

What do you mean by parse? What do you want to achieve? What have you tried so far? — Milan Cermak
– Milan Cermak, Commented Feb 12, 2019 at 12:57
i have a new and old image coming from dynamo db change in the associated lambda event .like newImage=json.loads(json.dumps(event['Records'][0]['dynamodb']['NewImage'])) .this gives me new image of event modify .now if i have to get bucket_name=newImage['InputSourceDetails']['M']['bucketName']['S'] i have to do something like this .Is there a better way to achieve the same . — divyanayan awasthi
– divyanayan awasthi, Commented Feb 13, 2019 at 6:22

Milan Cermak · Accepted Answer · 2019-02-13 15:14:36Z

3

You can use the jmespath library. It's already present in the python environment of Lambda, because it's a dependency of boto3.

path = 'Records[0].dynamodb.NewImage.InputSourceDetails.M.bucketName.S'
bucket_name = jmespath.search(path, event)

If there is no value under the path, the jmespath.search function will return None.

Btw you don't have to do the json.loads + json.dumps (as mentioned in the comment below the question), event is already a python dictionary.

answered Feb 13, 2019 at 15:14

Milan Cermak

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