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Creating and invoking Python actions

The process of creating Python actions is similar to that of other actions. The following sections guide you through creating and invoking a single Python action, and demonstrate how to bundle multiple Python files and third party dependencies.

An example action Python action is simply a top-level function. For example, create a file called hello.py with the following source code:

def main(args):
    name = args.get("name", "stranger")
    greeting = "Hello " + name + "!"
    print(greeting)
    return {"greeting": greeting}

An action supports not only a JSON object but also a JSON array as a return value.

It would be a simple example that uses an array as a return value:

def main(args):
    return ["a", "b"]

You can also create a sequence action with actions accepting an array param and returning an array result.

You can easily figure out the parameters with the following example:

def main(args):
    return args

Python actions always consume a dictionary and produce a dictionary. The entry method for the action is main by default but may be specified explicitly when creating the action with the wsk CLI using --main, as with any other action type.

You can create an OpenWhisk action called helloPython from this function as follows:

wsk action create helloPython hello.py

The CLI automatically infers the type of the action from the source file extension. For .py source files, the action runs using a Python 3.6 runtime.

Action invocation is the same for Python actions as it is for any other actions:

wsk action invoke --result helloPython --param name World

  {
      "greeting": "Hello World!"
  }

Find out more about parameters in the Working with parameters section.

Packaging Python actions in zip files

You can package a Python action and dependent modules in a zip file. The filename of the source file containing the entry point (e.g., main) must be __main__.py. For example, to create an action with a helper module called helper.py, first create an archive containing your source files:

zip -r helloPython.zip __main__.py helper.py

and then create the action:

wsk action create helloPython --kind python:3 helloPython.zip

Packaging Python actions with a virtual environment in zip files

Another way of packaging Python dependencies is using a virtual environment (virtualenv). This allows you to link additional packages that may be installed via pip for example. To ensure compatibility with the OpenWhisk container, package installations inside a virtualenv must be done in the target environment. So the docker image openwhisk/python3action should be used to create a virtualenv directory for your action.

As with basic zip file support, the name of the source file containing the main entry point must be __main__.py. In addition, the virtualenv directory must be named virtualenv. Below is an example scenario for installing dependencies, packaging them in a virtualenv, and creating a compatible OpenWhisk action.

  1. Given a requirements.txt file that contains the pip modules and versions to install, run the following to install the dependencies and create a virtualenv using a compatible Docker image:
docker run --rm -v "$PWD:/tmp" openwhisk/python3action bash \
  -c "cd tmp && virtualenv virtualenv && source virtualenv/bin/activate && pip install -r requirements.txt"
  1. Archive the virtualenv directory and any additional Python files:
zip -r helloPython.zip virtualenv __main__.py
  1. Create the action:
wsk action create helloPython --kind python:3 helloPython.zip

Python 3 actions

Python 3 actions are executed using Python 3.6.1. This is the default runtime for Python actions, unless you specify the --kind flag when creating or updating an action. The following packages are available for use by Python actions, in addition to the Python 3.6 standard libraries.

  • aiohttp v1.3.3
  • appdirs v1.4.3
  • asn1crypto v0.21.1
  • async-timeout v1.2.0
  • attrs v16.3.0
  • beautifulsoup4 v4.5.1
  • cffi v1.9.1
  • chardet v2.3.0
  • click v6.7
  • cryptography v1.8.1
  • cssselect v1.0.1
  • Flask v0.12
  • gevent v1.2.1
  • greenlet v0.4.12
  • httplib2 v0.9.2
  • idna v2.5
  • itsdangerous v0.24
  • Jinja2 v2.9.5
  • kafka-python v1.3.1
  • lxml v3.6.4
  • MarkupSafe v1.0
  • multidict v2.1.4
  • packaging v16.8
  • parsel v1.1.0
  • pyasn1 v0.2.3
  • pyasn1-modules v0.0.8
  • pycparser v2.17
  • PyDispatcher v2.0.5
  • pyOpenSSL v16.2.0
  • pyparsing v2.2.0
  • python-dateutil v2.5.3
  • queuelib v1.4.2
  • requests v2.11.1
  • Scrapy v1.1.2
  • service-identity v16.0.0
  • simplejson v3.8.2
  • six v1.10.0
  • Twisted v16.4.0
  • w3lib v1.17.0
  • Werkzeug v0.12
  • yarl v0.9.8
  • zope.interface v4.3.3