Lazy loading in Python Lambda when reading from S3

lazy-loading-lambda.py

""" The name of the S3 bucket and object is contained inside the event that triggered the Lambda """
def lambda_handler(event, context):
    
    # Define client
    s3 = boto3.client('s3')
    
    # Get the bucket name
    source_bucket_name = event['Records'][0]['s3']['bucket']['name']

    # Get the object name
    key_name = event['Records'][0]['s3']['object']['key']
    
    # Get object from s3 [dict type]
    response = s3.get_object(Bucket=source_bucket_name, Key=key_name)
    
    # Open the stream in binary mode [objects in s3 are binary]
    # TextIOWrapper decodes in chunks.
    stream_content = io.TextIOWrapper(gzip.GzipFile(None, 'rb', fileobj=response['Body']))

    # Count HTTP 460s per targetgroup in AWS ELB [dict]
    http_460s_per_targetgroup = {}
    
    for each_line in stream_content:
        if (" 460 " in each_line) and ("targetgroup" in each_line):
            # Do some regex magic to find "targetgroup"
            targetgroup_name = return_target_group_from_string(each_line)
            increment_targetgroup_460_counter(http_460s_per_targetgroup, targetgroup_name)
        else:
            logging.info("False HTTP 460 log does not contain a target group")