How do I format the Key in my boto3 lambda function to update dynamodb?

Question

I need help with figuring out how to format my Key in lambda to update an item in DynamoDB. Below is the code I have but I can't figure out how to format the Key.

My table looks as follows:

'''

import json import boto3

dynamodb = boto3.resource('dynamodb')

client = boto3.client('dynamodb')

def lambda_handler(event, context):

response = client.update_item(
    TableName='hitcounter',
    Key={????????},
    UpdateExpression='ADD visits :incr',
    ExpressionAttributeValues={':incr': 1}

)


print(response)

'''

ERROR MESSAGE:

''' { "errorMessage": "'path'", "errorType": "KeyError", "stackTrace": [ " File \"/var/task/lambda_function.py\", line 11, in lambda_handler\n Key={'path': event['path']},\n" ] }

'''

Marcin · Accepted Answer · 2020-06-11 02:59:45Z

1

The AWS docs provides an example for Updating an item:

table.update_item(
    Key={
        'username': 'janedoe',
        'last_name': 'Doe'
    },
    UpdateExpression='SET age = :val1',
    ExpressionAttributeValues={
        ':val1': 26
    }
)

I'm not sure from your question, if the AWS examples are unclear or what is the issue specifically?

answered Jun 11, 2020 at 2:59

Marcin

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8 Comments

nktanu Over a year ago

I keep getting this error. I'm assuming that it has to do with my Key. I've tried following documentation but still get it. ''' { "errorMessage": "'path'", "errorType": "KeyError", "stackTrace": [ " File \"/var/task/lambda_function.py\", line 11, in lambda_handler\n Key={'path': event['path']},\n" ] } '''

Marcin Over a year ago

@nktanu This is your lambda code issue, not specific to DdB. Can you update the message with the error message, the structure of event object and how do you access it?

nktanu Over a year ago

Sorry I'm pretty new to this and learning as much as I can right now. I added the error to to my post. I'm not sure what you mean by the structure of the event and how it's accessed? @Marcin

Mahdi Ridho Over a year ago

can you add log output for the "event" variable? Check on your cloudwatch what the log result and paste here? I guess the problem came there. It's something like event['path'] is missing value.

nktanu Over a year ago

Got it figured out! It had to do with the defining variables at the top of my code

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