JSON error expected string or buffer: TypeError lambda function failing

Question

Trying to complete a lab for setting up a mobile game. But the lambda function is throwing the following error:

expected string or buffer: TypeError
Traceback (most recent call last):
File "/var/task/lambda_function.py", line 34, in lambda_handler json_data = json.loads(msg)

From what I understand it is expecting a string but the variable msg is a dictionary that also contains list. Can someone explain how I can get this working? Should it be a json.dump instead? New to python and coding so please forgive if I'm not framing the question in the correct way. Code is below. Thanks in advance

def lambda_handler(event, context):
global client
print(event)
# check the receiver's queue url
if client == None:
    client = boto3.resource('sqs')
records = event['Records'][0]
sns_data = records['Sns']
msg = sns_data['Message']
print(msg)
json_data = json.loads(msg)
type_of_msg = json_data['type']
sender = json_data['sender']
receiver = json_data['receiver']
amount = json_data['amount']
# queue_name = get_queue_name_by_account_id(receiver)
queue_name = USER_POOL_ID + "_" + receiver
# enqueue the message
queue = client.get_queue_by_name(QueueName=queue_name)
msg = {
    "type": type_of_msg,
    "amount": amount
}
res = queue.send_message(MessageBody=json.dumps(msg))
print(res)
return json_data['receiver']

Please edit the sample code above to have the proper indentation. — GaryMBloom
– GaryMBloom, Commented Dec 9, 2017 at 18:17

Geander · Accepted Answer · 2017-12-12 18:17:51Z

json.loads needs a string or buffer, not a json.

msg is already a json, do not need to do json.loads.

below is a working example.

import boto3
import json

def lambda_handler(event, context):
    client = None
    USER_POOL_ID = 'xxxxx'
    print(event)
    # check the receiver's queue url
    if client == None:
        client = boto3.resource('sqs')
    records = event['Records'][0]
    sns_data = records['Sns']
    msg = sns_data['Message']
    print(msg)
    json_data = msg
    type_of_msg = json_data['type']
    sender = json_data['sender']
    receiver = json_data['receiver']
    amount = json_data['amount']
    # queue_name = get_queue_name_by_account_id(receiver)
    queue_name = USER_POOL_ID + "_" + receiver
    #enqueue the message
    queue = client.get_queue_by_name(QueueName=queue_name)
    msg = {
        "type": type_of_msg,
        "amount": amount
    }
    res = queue.send_message(MessageBody=json.dumps(msg))
    print(res)
    return json_data['receiver']

With sample test event for lambda:

{
  "Records": [
      {"Sns": {"Message": {"type": "a","sender": "b","receiver": "c","amount": "d"}}}
  ]
}

Hope this helps!

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