Try out a Lambda function locally before you upload it to the cloud.

A Python-based implementation of trylam.

Pylam runs as a small Python module. It can be installed as a development dependency, so that it adds nothing to the production runtime.

A typical setup involves doing the following:

1. Add a development dependency to the Lambda Python project:

   pip install -f requirements-dev.txt
   

2. Once installed, start up Pylam as follows:

   python -m pylam lambda_function.lambda_handler
   

   Where lambda_function.lambda_handler is the Lambda file name and function name respectively.

   NOTE: Two additional optional parameters can be specified:

   • Argument 2: The path to the Lambda entrypoint. This can be useful if the function is not in the root directory of the project. Do not include leading or trailing slashes (/)
   • Arrgument 3: The file extension. By default .py is used. To set to blank, pass the string "NONE".

   A full invocation may look like the following:

   python -m pylam lambda_function.lambda_handler src/lambdas .py
   

3. To invoke Pylam, make an HTTP call on port 9000 (the default port). For example:

   curl --request POST --url http://localhost:9000/ --data '{ "key1": "value1", "key2": [ "item21","item22"]}'
   

   NOTE: The --data will be used as the event parameter to the Lambda function.

   After running, you should see the results of the invocation on the console. Example:

   {"statusCode":200,"body":"\"Hello from Lambda!\""}
   

4. To Use Visual Studio Code to debug the function: Add a launch configuration:

   {
       "version": "0.2.0",
       "configurations": [
           {
               "name": "Hot dog debug",
               "type": "debugpy",
               "request": "launch",
               "module": "pylam",
               "args": ["lambda_function.lambda_handler", "."],
             "console": "integratedTerminal"
           }  
       ]
   }
   

   NOTE:: The above configuration assumes the Lambda entry point is named lambda_handler() and the name of the Lambda file is lambda_function.py.

   Set a breakpoint in the Lambda handler, and invoke the function via a curl call:

   curl --request POST --url http://localhost:9000/2015-03-31/functions/function/invocations --data '{ "key1": "value1", "key2": [ "item21","item22"]}'
   

From the root directory:

1. Bump the version number in pyproject.toml and src/pylam/__init__.py Set it to something like 0.9.0
2. Run python -m build
3. Run pip install --force-reinstall dist/pylam-0.9.0-py3-none-any.whl

This is a Python-based implementation of trylam, so for any questions, please open an issue in that repository.