Getting NULL output when running python job - python-2.7

Question

I am running a python job in AWS Lambda to stop ec2 instances based on tags.
The script is running properly, but even if the script completes successfully, I am getting output "null" in the result returned by function execution.
Attached herewith is the python script. I am new to Python scripting. I am from ops side.
import boto3
import logging
#setup simple logging for INFO
logger = logging.getLogger()
logger.setLevel(logging.INFO)
#define the connection
ec2 = boto3.resource('ec2')
def lambda_handler(event, context):
# Use the filter() method of the instances collection to retrieve
# all running EC2 instances.
filters = [{
'Name': 'tag:AutoOff',
'Values': ['True']
},
{
'Name': 'instance-state-name',
'Values': ['running']
}
]
#filter the instances
instances = ec2.instances.filter(Filters=filters)
#locate all running instances
RunningInstances = [instance.id for instance in instances]
#print the instances for logging purposes
print RunningInstances
#make sure there are actually instances to shut down.
if len(RunningInstances) > 0:
#perform the shutdown
shuttingDown = ec2.instances.filter(InstanceIds=RunningInstances).stop()
print shuttingDown
else:
print "NOTHING"

Answer 1

In order to get response from the lambda you need to return something (usually a dictionary) from lambda_handler method. By default all Python methods return None type, that is why you do not receive any valuable response.
def lambda_handler(event, context):
... your code here ...
return {"turned_off": RunningInstances}
PS. it is preferred to use logging.debug|info|... method instead of print(). You can find more info in the documentation: https://docs.python.org/2.7/library/logging.html
Anyway all the output is saved to CloudWatch Logs. The Log Stream is created automatically when you create a Lambda function. You can find all your prints there for debugging.