AWS Classroom Series – 02/Jul/2020

Creating an AWS Lambda with Environment and events using python

• Create a blank function using python in aws lambda
• Lets build a simple calculator

{
    "op": add/sub,
    "val1": 5,
    "val2": 2

}

• Now lets take the basic python code

import json

def lambda_handler(event, context):
    # TODO implement
    
    return {
        'statusCode': 200,
        'body': json.dumps('Hello from Lambda!')
    }

• Now lets modify the code to suit our problem statement

import json

def lambda_handler(event, context):
    op = event['op']
    val1 = event['val1']
    val2 = event['val2']
    result = 0
    if op == 'add':
        result = val1 + val2
    elif op == 'sub':
        result = val1 - val2
    elif op == 'mul':
        result = val1 * val2
    elif op == 'div':
        result = val1 // val2
    else:
        result = "Invalid"
        
        
    
    return {
        'statusCode': 200,
        'body': json.dumps(result)
    }

• Now lets add the following logic to make use of environmental variables. I will be adding a ENVIRONMENTAL variable "DEBUG_LEVEL" which if it has value as verbose, we should print more logs
• Now lets make changes in the code

import json
import os

def lambda_handler(event, context):
    debug_level = os.getenv('DEBUG_LEVEL')

    op = event['op']
    val1 = event['val1']
    val2 = event['val2']
    if debug_level == 'VERBOSE' :
        print("{} is operator and values are {} {}".format(op,val1,val2))
    result = 0
    if op == 'add':
        result = val1 + val2
    elif op == 'sub':
        result = val1 - val2
    elif op == 'mul':
        result = val1 * val2
    elif op == 'div':
        result = val1 // val2
    else:
        result = "Invalid"
    return {
        'statusCode': 200,
        'body': json.dumps(result)
    }

• If you execute the function with environment varaible ‘DEBUG_LEVEL’ with value ‘VERBOSE’ you should see extra logs

• Lambda can be exposed using API Gateways or Load balancers.