reading files triggered by s3 event

Question

Here is what i want to do :

1. User uploads a csv file onto AWS S3 bucket.
2. Upon file uploaded, S3 bucket invokes the lambda function that i have created.

Answer 1

I suggest to add to your IAM policy also the access to Cloudwatch. Actually your lambda function is not returning anything, but you can see your log output in Cloudwatch. I really recommend to use logger.info(message) instead of print when you are setting up logger.

I hope that this helps to debug your function.

Except the part of sending, this is how I will rewrite it (just tested in the AWS console):

import logging
import boto3

logger = logging.getLogger()
logger.setLevel(logging.INFO)

s3 = boto3.client('s3')

def lambda_handler(event, context):
    email_content = ''

    # retrieve bucket name and file_key from the S3 event
    bucket_name = event['Records'][0]['s3']['bucket']['name']
    file_key = event['Records'][0]['s3']['object']['key']
    logger.info('Reading {} from {}'.format(file_key, bucket_name))
    # get the object
    obj = s3.get_object(Bucket=bucket_name, Key=file_key)
    # get lines inside the csv
    lines = obj['Body'].read().split(b'\n')
    for r in lines:
       logger.info(r.decode())
       email_content = email_content + '\n' + r.decode()
    logger.info(email_content)