Python-lambda is a toolset for developing and deploying serverless Python code in AWS Lambda.

AWS Lambda is a service that allows you to write Python, Java, or Node.js code that gets executed in response to events like http requests or files uploaded to S3.

Working with Lambda is relatively easy, but the process of bundling and deploying your code is not as simple as it could be.

The Python-Lambda library takes away the guess work of developing your Python-Lambda services by providing you a toolset to streamline the annoying parts.

• Python 3.6
• Pip (~8.1.1)
• Virtualenv (~15.0.0)
• Virtualenvwrapper (~4.7.1)

Begin by creating a new virtualenv and project folder.

  $ virtualenv -p python3 pylambda
  $ source pylambda/bin/activate

Next, download Python-Lambda using pip via Github.

  (pylambda) $ pip install git+https://github.com/jgillard/python-lambda

From your pylambda directory, run the following to bootstrap your project.

  (pylambda) $ lambda init

This will create the following files: event.json, __init__.py, service.py, and config.yaml.

Next let's open service.py, in here you'll find the following function:

  def handler(event, context):
    # Your code goes here!
    e = event.get('e')
    pi = event.get('pi')
    return e + pi

This is the handler function; this is the function AWS Lambda will invoke in response to an event. You will notice that in the sample code e and pi are values in a dict. AWS Lambda uses the event parameter to pass in event data to the handler.

So if, for example, your function is responding to an http request, event will be the POST JSON data and if your function returns something, the contents will be in your http response payload.

Next let's open the event.json file:

  {
    "pi": 3.14,
    "e": 2.718
  }

Here you'll find the values of e and pi that are being referenced in the sample code.

If you now try and run:

  (pylambda) $ lambda invoke -v

You will get:

  # 5.858

  # execution time: 0.00000310s
  # function execution timeout: 15s

As you probably put together, the lambda invoke command grabs the values stored in the event.json file and passes them to your function.

The event.json file should help you develop your Lambda service locally. You can specify an alternate event.json file by passing the --event-file=<filename>.json argument to lambda invoke.

  (pylambda) $ python -m pytest tests/

TODO: lambda test to wrap pytest

Copy the template Terraform from the Usage section here:

https://github.com/depop/depop-infrastructure/tree/master/modules/tf_community_modules/tf_aws_lambda#usage

There is also a scheduled Lambda function available:

https://github.com/depop/depop-infrastructure/tree/master/modules/tf_community_modules/tf_aws_lambda_scheduled#usage