Lamda Function Execution Error

Question

I created a python program that counts number of RDs instances anad prints it.
Program runs fine in standlaone mode in Windows. I want to add this to AWS as Lambda Function.

```
#!/usr/bin/env python3

from boto3 import client

client = client('rds')

rds_instances = client.describe_db_instances(Filters=[{'Name':'engine', 'Values':['oracle-ee']}])

#print out just the number like your shell script
print(len(rds_instances['DBInstances']))

#Just a little additional code to show you how to access the results from the describe_db_instances call:
if len(rds_instances['DBInstances']) != 0:
    for db_instance in rds_instances['DBInstances']:
        db_engine = db_instance.get('Engine')
        print(db_engine)
```

I created a new IAM role "Lambda-Role" and gave it "administratorAcceess" policy because the policy "AWSLambda_FullAccess" generated a permission error for script to run a Boto or CLI command. I know this is not secure and I have to change it later.

However, I an getting this error even though the program does print the output.
Do you know what is causing this and how to fix it?

Details
Execution function: failed

{
  "errorMessage": "Handler 'lambda_handler' missing on module 'lambda_function'",
  "errorType": "Runtime.HandlerNotFound",
  "requestId": "bfe08f55-5bb3-4d59-8c4d-fb448a4ec15c",
  "stackTrace": []
}

Log Output

{
1
oracle-ee
START RequestId: bfe08f55-5bb3-4d59-8c4d-fb448a4ec15c Version: $LATEST
[ERROR] Runtime.HandlerNotFound: Handler 'lambda_handler' missing on module 'lambda_function'
Traceback (most recent call last):END RequestId: bfe08f55-5bb3-4d59-8c4d-fb448a4ec15c
REPORT RequestId: bfe08f55-5bb3-4d59-8c4d-fb448a4ec15c Duration: 20.24 ms Billed Duration: 21 ms Memory Size: 128 MB Max Memory Used: 78 MB Init Duration: 761.92 ms

Accepted Answer

Hello.

Try your Python code as below.  
The Lambda function executes the handler method when the function is called, so you need to define the function as follows.  
https://docs.aws.amazon.com/lambda/latest/dg/python-handler.html  
```
#!/usr/bin/env python3

from boto3 import client

client = client('rds')

def lambda_handler(event, context):

rds_instances = client.describe_db_instances(Filters=[{'Name':'engine', 'Values':['oracle-ee']}])

#print out just the number like your shell script
    print(len(rds_instances['DBInstances']))

#Just a little additional code to show you how to access the results from the describe_db_instances call:
    if len(rds_instances['DBInstances']) != 0:
        for db_instance in rds_instances['DBInstances']:
            db_engine = db_instance.get('Engine')
            print(db_engine)
```

Lamda Function Execution Error

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