Testing AWS Serverless Services https://towardsdatascience.com/testing-serverless-services-59c688812a0d

extract.py

def handler(event, context):
    """
    extract the contents from the emails and
    put the resulting object back to s3.
    """
    # get the source key and bucket from
    # the event that triggered this lambda_function function.
    source_key = event['Records'][0]['s3']['object']['key']
    source_bucket = event['Records'][0]['s3']['bucket']['name']

    # get the email name from the key
    email_name = source_key.split('/')[-1]

    # get email from s3,
    s3_client = boto3.client('s3')
    s3_object = s3_client.get_object(Bucket=source_bucket,
                                     Key=source_key)["Body"].read()
    # extract the contents
    email_object = extract_contents(s3_object, email_name)

    # get the destination key and bucket
    # from the environment variables
    destination_bucket = os.getenv('DEST_BUCKET')
    destination_key = os.getenv('DEST_KEY')
    full_s3_key = destination_key + email_name + '.json'

    # dump the result back to s3
    s3_client.put_object(Body=email_object,
                         Bucket=destination_bucket,
                         Key=full_s3_key)
    return full_s3_key