actionpack 1.1.1a2

a lib for describing Actions and how they should be performed

actionpack

a lib for describing Actions and how they should be performed

Overview

Side effects are annoying. Verification of intended outcome is often difficult and can depend on the system's state at runtime. Questions like "Is the file going to be present when data is written?" or "Will that service be available?" come to mind. Keeping track of external system state is just impractical, but declaring intent and encapsulating its disposition is doable.

Usage

Intent can be declared using Action objects:

>>> action = ReadBytes('path/to/some/file')

An Action collection can be used to describe a procedure:

>>> actions = [action,
...            ReadBytes('path/to/some/other/file'),
...            ReadInput('>>> how goes? <<<\n  > '),
...            MakeRequest('GET', 'http://google.com'),
...            RetryPolicy(MakeRequest('GET', 'http://bad-connectivity.com'),
...                        max_retries=2,
...                        delay_between_attempts=2)
...            WriteBytes('path/to/yet/another/file', b'sup')]
...
>>> procedure = Procedure(*actions)

And a Procedure can be executed synchronously or otherwise:

>>> results = procedure.execute()  # synchronously by default
>>> _results = procedure.execute(synchronously=False)  # async; not thread safe
>>> result = next(results)
>>> print(result.value)

A KeyedProcedure is just a Procedure comprised of named Actions. The Action names are used as keys for convenient result lookup.

>>> prompt = '>>> sure, I'll save it for ya.. <<<\n  > '
>>> saveme = ReadInput(prompt).set(name='saveme')
>>> writeme = WriteBytes('path/to/yet/another/file', b'sup').set(name='writeme')
>>> actions = [saveme, writeme]
>>> keyed_procedure = KeyedProcedure(*actions)
>>> results = keyed_procedure.execute()
>>> keyed_results = dict(results)
>>> first, second = keyed_results.get('saveme'), keyed_results.get('writeme')

One can also create an Action from some arbitrary function

>>> Call(closure=Closure(some_function, arg, kwarg=kwarg))

Development

Build scripting is managed via Makefile. Execute make commands to see the available commands. To get started, simply run make. Doing so will create a virtualenv loaded with the relevant dependencies. All tests can be run with make tests and a single test can be run with something like the following:

make test TESTCASE=<tests-subdir>.<test-module>.<class-name>.<method-name>

Making new actionpack.actions is straightforward. After defining a class that inherits Action, ensure it has an .instruction method. If any attribute validation is desired, a .validate method can be added.

There is no need to add Action dependencies to setup.py. Dependencies required for developing an Action go in :::drum roll::: requirements.txt. When declaring your Action class, a requires parameter can be passed a tuple.

class MakeRequest(Action, requires=('requests',)):
    ...

This will check if the dependencies are installed and, if so, will register each of them as class attributes.

mr = MakeRequest('GET', 'http://localhost')
mr.requests  #=> <module 'requests' from '~/actionpack/actionpack-venv/lib/python3/site-packages/requests/__init__.py'>