python-lambda-local

Run lambda function on local machine

Prepare development environment

Please use a newly created virtualenv of Python 2.7 or Python 3.6 .

Installation

Within virtualenv, run the following command.

$ pip install python-lambda-local

This will install the package with name python-lambda-local in the virtualenv. Now you can use the command python-lambda-local to run your AWS Lambda function written in Python on your own machine.

Usage

Run python-lambda-local -h to see the help.

usage: python-lambda-local [-h] [-l LIBRARY_PATH] [-f HANDLER_FUNCTION]
[-t TIMEOUT] [-a ARN_STRING] [-v VERSION_NAME]
[--version]
FILE EVENT
Run AWS Lambda function written in Python on local machine.
positional arguments:
FILE lambda function file name
EVENT event data file name
optional arguments:
-h, --help show this help message and exit
-l LIBRARY_PATH, --library LIBRARY_PATH
path of 3rd party libraries
-f HANDLER_FUNCTION, --function HANDLER_FUNCTION
lambda function handler name, default: "handler"
-t TIMEOUT, --timeout TIMEOUT
seconds until lambda function timeout, default: 3
-a ARN_STRING, --arn-string ARN_STRING
ARN string for lambda function
-v VERSION_NAME, --version-name VERSION_NAME
lambda function version name
--version print the version of python-lambda-local and exit

Prepare development directory

Project directory structure

Suppose your project directory is like this:

├── event.json
├── lib
│ ├── rx
│ │ ├── abstractobserver.py
│ │ ├── ... (package content of rx)
...
│ │ └── testscheduler.py
│ └── Rx-1.2.3.dist-info
│ ├── DESCRIPTION.rst
│ ├── METADATA
│ ├── metadata.json
│ ├── pbr.json
│ ├── RECORD
│ ├── top_level.txt
│ ├── WHEEL
│ └── zip-safe
└── test.py

The handler's code is in test.py and the function name of the handler is handler. The source depends on 3rd party library rx and it is installed in the directory lib. The test event in json format is in event.json file.

Content of test.py:

from __future__ importprint_functionfromrximportObservabledefhandler(event, context):
xs=Observable.from_(range(event['answer']))
ys=xs.to_blocking()
zs= (x*xforxinysifx%7==0)
forxinzs:
print(x)

Content of event.json:

{
"answer": 42
}

Run the lambda function

Within the project root directory, you can run the lambda function with the following command

python-lambda-local -l lib/ -f handler -t 5 test.py event.json

The output will be like:

[root - INFO - 2017-04-19 12:39:05,512] Event: {u'answer': 42}
[root - INFO - 2017-04-19 12:39:05,512] START RequestId: b918f9ae-0ca1-44af-9937-dd5f9eeedcc1
0
49
196
441
784
1225
[root - INFO - 2017-04-19 12:39:05,515] END RequestId: b918f9ae-0ca1-44af-9937-dd5f9eeedcc1
[root - INFO - 2017-04-19 12:39:05,515] RESULT:
None
[root - INFO - 2017-04-19 12:39:05,515] REPORT RequestId: b918f9ae-0ca1-44af-9937-dd5f9eeedcc1	Duration: 2.27 ms