MIGRATING.md

Migrating to modern Pex

Lambdex used to be needed to produce zip files useable in lambda functions, but with modern Pex, it no longer is. Starting with Pex version 2.1.98 you only need to include import __pex__ at the top of your lambda handler entrypoint module and build the PEX with --inherit-path {fallback,prefer}.

For example, with the following my_lambda_module.py:

import __pex__

import hashlib

import requests


def handler(event, context):
    url = event["url"]
    return {
        url: hashlib.sha256(requests.get(url).content).hexdigest(),
        "requests.__file__": requests.__file__,
    }

You can create a zip that will work¹ in the Python 3.12 AWS lambda runtime with:

pex \
    --python python3.12 \
    requests \
    --module my_lambda_module \
    --output-file pex_lambda_function.zip \
    --inherit-path=fallback

With the zip uploaded and the lambda runtime configured to use the my_lambda_module.handler handler, you can post an event with {"url": "https://example.org"} to the handler endpoint and see a response similar to:

{
  "https://example.org": "ea8fac7c65fb589b0d53560f5251f74f9e9b243478dcb6b3ea79b5e36449c8d9",
  "requests.__file__": "/var/task/.deps/requests-2.32.3-py3-none-any.whl/requests/__init__.py"
}

Footnotes

1. In general, you need to either build the PEX in an environment compatible with the Lambda deployment environment or else use the the Pex --complete-platform option to properly cross-resolve for the deployement environment. This is no different a requirement than existed when using Lambdex to transform a PEX into a lambda-compatible zip previously. ↩