Access json request from python in python AWS lambda function

Question

I have an API in the AWS API gateway, connected to an AWS Lambda function in python, using lambda proxy integration. On my local computer, I am testing this API in python. I want to send a dictionary to the api and have the api return me a function of the elements in the dictionary.

The python code I use to test is:

import requests
import json

url = "https://p68yzl6gu6.execute-api.us-west-1.amazonaws.com/test/helloworld"

headers = {'data': [0,1]}

response = requests.post(url, json=headers)

print(response.text)

Since I cannot send a list through the header argument of requests.post I thought I'd use json. When I try this, I get a {"message": "Internal server error"}. This is my AWS lambda function (python):

import json

def lambda_handler(event, context):
    return {
        'statusCode': 200,
        'body': event['data']
    }

Looking at the logs, 'data' is not a key of event. How do I access the list in the AWS Lambda function? How do I find out what the event dictionary looks like when I test this? Looking forward I want to send a large dict containing dicts and lists. Is this the right way to do it?

Try showing event keys by calling event.keys() inside the lambda_handler method and see what pops up. — florex
– florex, Commented Aug 8, 2020 at 0:19
Where exactly would I do that? Where it says event['data']? If I do that and call my python function I still get an internal server error which doesn't really help.. — William Steenbergen
– William Steenbergen, Commented Aug 8, 2020 at 0:24
Thanks, if I do that, how/where would I see the output of that line? — William Steenbergen
– William Steenbergen, Commented Aug 8, 2020 at 0:30
I'm finding there are quite a few essential assumptions that are largely undocumented about using AWS Lambda. Does AWS convert your response to JSON or not, possibly controlled by a flag in the AWS configuration, how are stderr stdout handled, what is the default logging set up, etc. I like that "where would I see the output" question - exactly! — NeilG
– NeilG, Commented Feb 14, 2023 at 6:09

jellycsc · Accepted Answer · 2020-08-08 00:31:37Z

13

Try

import json

def lambda_handler(event, context):
    body = json.loads(event['body'])
    return {
        'statusCode': 200,
        'body': json.dumps(body['data'])
    }

edited Aug 8, 2020 at 0:31

answered Aug 8, 2020 at 0:18

jellycsc

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4 Comments

jellycsc Over a year ago

Try again, I added a json.dumps @WilliamSteenbergen

jellycsc Over a year ago

@WilliamSteenbergen try again

William Steenbergen Over a year ago

yes that works, thanks so much! the json.loads does it.

jellycsc Over a year ago

@WilliamSteenbergen no prob

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