How to pass parameters to an AWS Lambda Function using Python

Question

I have written an AWS Lambda function in Python that filters through instances and turns them on or off depending on how they are tagged. This will show you a working function, and the set-up needed to get it working. If you have questions on anything post it in the comments.

Here is my Lambda Function as of now:

import boto3
def lambda_handler(event, context):
    startStop = event['startStop']
    vertical = event['vertical']
    isRunning = ''

    if(startStop == 'start'):
        isRunning = 'stopped'
    elif (startStop == 'stop'):
        isRunning = 'running'

    ec2 = boto3.resource('ec2')
    filters = [
        {
            'Name': 'instance-state-name', 
            'Values': [isRunning] 
        },
        {
            'Name': 'tag:Vertical',
            'Values': [vertical]
        }
    ]

    instances = ec2.instances.filter(Filters=filters)

    runningInstances = [instance.id for instance in instances]

    if len(runningInstances) > 0:
        if(startStop == 'start'):
            shuttingDown = ec2.instances.filter(InstanceIds=runningInstances).start()
        elif (startStop == 'stop'):
            shuttingDown = ec2.instances.filter(InstanceIds=runningInstances).stop()

For reference, here is my mapping template:

{
    "startStop":"$input.params('startStop')",
    "vertical":"$input.params('vertical')"
}

And this is how I am passing in the parameters within the URL:

https://awslambdaapiurl.../prod/-params?startStop=start&vertical=TEST

Answer 1

You can use the queryStringParameters on event object.

request_data = event['queryStringParameters']
startStop = request_data['startStop']
vertical = request_data['vertical']