Python AWS Lambda's event body returning string instead of my json object

Question

Invocation code

import requests
import json
# Create a new resource
data_object = {'key1':'testing'}
response = requests.post('https://fakeurl.execute-api.us-east-1.amazonaws.com/default/My_Test_Event_Lambda', data=data_object)

print(response._content.decode())

Lambda Code

import json

def lambda_handler(event, context):

    return {
                'statusCode': 200,
                'body': json.dumps(event['body'])
            }

The response I get from invocation is "key1=testing" I don't care so much about the response but i want the lambda function to be able to handle my data passed as json not a string. Example: I want to be able to say event['body']['key1'] and have it return "testing"

Currently API gateways being used as lambda proxy.

jarmod · Accepted Answer · 2021-12-14 16:36:58Z

11

The event['body'] you received is a string. You need to parse that from JSON into a dict with:

d = json.loads(event['body'])

Then you can return that dict as the body in your response, if you want, via:

return {
    'statusCode': 200,
    'body': json.dumps(d)
}

As it stands, you're just managing strings.

answered Dec 14, 2021 at 16:36

jarmod

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7 Comments

Sitruc Over a year ago

Hmmm I'm getting a key error when i use your code.

{   "errorMessage": "'body'",   "errorType": "KeyError",   "stackTrace": [     "  File \"/var/task/lambda_function.py\", line 4, in lambda_handler\n    d = json.loads(event['body'])\n"   ] }

jarmod Over a year ago

Are you using Lambda Proxy integration in API Gateway?"

Sitruc Over a year ago

Yea i'm using the proxy integration Type: LAMBDA_PROXY is displayed in Integration Request

jarmod Over a year ago

Did you debug log event to see what's in it? I assumed this was already working to retrieve the body, because your original code uses it.

jarmod Over a year ago

Because the body is not actually JSON, perhaps? It's just key=value when it should be {"key":"value"} (assuming you actually meant to pass JSON over the interface).

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