Details on the AWS Lambda Python LambdaContext context object when instantiated from a CloudFormation stack

example_aws_lambda_cloudformation_context.md

LambdaContext

Here is the raw output from examining the Python LambdaContext context object in a AWS Lambda function when called from a CloudFormation stack. More information on the context object can be found here : http://docs.aws.amazon.com/lambda/latest/dg/python-context-object.html

LambdaContext object : print(context)

<__main__.LambdaContext object at 0x7fd706780710>

LambdaContext vars : vars(context)

{
    'aws_request_id': 'a3de505e-f16b-42f4-b3e6-bcd2e4a73903',
    'log_stream_name': '2015/10/26/[$LATEST]c71058d852474b9895a0f221f73402ad',
    'invoked_function_arn': 'arn:aws:lambda:us-west-2:123456789012:function:ExampleCloudFormationStackName-ExampleLambdaFunctionResourceName-AULC3LB8Q02F',
    'client_context': None,
    'log_group_name': '/aws/lambda/ExampleCloudFormationStackName-ExampleLambdaFunctionResourceName-AULC3LB8Q02F',
    'function_name': 'ExampleCloudFormationStackName-ExampleLambdaFunctionResourceName-AULC3LB8Q02F',
    'function_version': '$LATEST',
    'identity': <__main__.CognitoIdentity object at 0x7fd7042a2b90>,
    'memory_limit_in_mb': '128'
} 

LambdaContext dir : dir(context)

[
    '__class__',
    '__delattr__',
    '__dict__',
    '__doc__',
    '__format__',
    '__getattribute__',
    '__hash__',
    '__init__',
    '__module__',
    '__new__',
    '__reduce__',
    '__reduce_ex__',
    '__repr__',
    '__setattr__',
    '__sizeof__',
    '__str__',
    '__subclasshook__',
    '__weakref__',
    'aws_request_id',
    'client_context',
    'function_name',
    'function_version',
    'get_remaining_time_in_millis',
    'identity',
    'invoked_function_arn',
    'log',
    'log_group_name',
    'log_stream_name',
    'memory_limit_in_mb'
]

context.succeed()

The Python runtime does not have the equivalent of a context.succeed(), context.done() or context.fail().

In order to achieve the same thing, merely return from the handler function to succeed or raise an exception to fail

def lambda_handler(event, context):
    if event['variable_name'] == 1:
        return { 
            'message' : 'We are done'
        }
    else:
        raise Exception('Sending failure')

What does it look like from AWS's side

@NovemberOscar points out this code which shows what AWS sees on their side for the Python context

https://github.com/aws/aws-lambda-python-runtime-interface-client/blob/main/awslambdaric/lambda_context.py

Hi Gene –

Thanks for the gist. I've seen examples of people calling context.succeed() in the Node.js runtime. Is this possible with Python? I can't find anything in the docs.

Thanks for the gist :)
I have the exact same problem. Can't find anything in the docs about the said succeed or done methods that seem to be used with Node.js runtime.

Hi Michael and Gene,
I'm running into the same problem. Did either of you find a workaround to exit the program early without throwing an error?

@msambol @Depado @cameck have you tried just returning from the handler function?

http://docs.aws.amazon.com/lambda/latest/dg/python-context-object.html

Alexa's skill id is delivered the context object during certain audio playback requests. does that have an alias?

Just found this, but for anyone else looking, AWS Lambda's Python runtime does not have a succeed() capability. I'm not sure why of the disparity between the two runtimes, but a successful return (whether controlled exceptions via a catch block or normal execution) is what tells Lambda to succeed the invocation.

And more details here :) (it's official!)

https://github.com/aws/aws-lambda-python-runtime-interface-client/blob/main/awslambdaric/lambda_context.py

Where do I put the response body? How can I mapping template response headers out of it? All I can do is set errorMessage with an exception, right? 304 Not Modified, where does ETag go?