zorky / xworkflows

Python "state machine" module

XWorkflows

XWorkflows is a library to add workflows, or state machines, to Python objects.

It has been fully tested with all versions of Python from 2.7 to 3.6

Links

• Package on PyPI: http://pypi.python.org/pypi/xworkflows
• Repository and issues on GitHub: http://github.com/rbarrois/xworkflows
• Doc on http://readthedocs.org/docs/xworkflows/

Example

It allows to easilly define a workflow, attach it to a class, and use its transitions:

import xworkflows

class MyWorkflow(xworkflows.Workflow):
    # A list of state names
    states = (
        ('foo', "Foo"),
        ('bar', "Bar"),
        ('baz', "Baz"),
    )
    # A list of transition definitions; items are (name, source states, target).
    transitions = (
        ('foobar', 'foo', 'bar'),
        ('gobaz', ('foo', 'bar'), 'baz'),
        ('bazbar', 'baz', 'bar'),
    )
    initial_state = 'foo'


class MyObject(xworkflows.WorkflowEnabled):
    state = MyWorkflow()

    @xworkflows.transition()
    def foobar(self):
        return 42

    # It is possible to use another method for a given transition.
    @xworkflows.transition('gobaz')
    def blah(self):
        return 13

>>> o = MyObject()
>>> o.state
<StateWrapper: <State: 'foo'>>
>>> o.state.is_foo
True
>>> o.state.name
'foo'
>>> o.state.title
'Foo'
>>> o.foobar()
42
>>> o.state
<StateWrapper: <State: 'bar'>>
>>> o.state.name
'bar'
>>> o.state.title
'Bar'
>>> o.blah()
13
>>> o.state
<StateWrapper: <State: 'baz'>>
>>> o.state.name
'baz'
>>> o.state.title
'Baz'

Hooks

Custom functions can be hooked to transactions, in order to run before/after a transition, when entering a state, when leaving a state, ...:

class MyObject(xworkflows.WorkflowEnabled):

    state = MyWorkflow()

    @xworkflows.before_transition('foobar')
    def my_hook(self, *args, **kwargs):
        # *args and **kwargs are those passed to MyObject.foobar(...)
        pass

    @xworkflows.on_enter_state('bar')
    def my_other_hook(self, result, *args, **kwargs):
        # Will be called just after any transition entering 'bar'
        # result is the value returned by that transition
        # *args, **kwargs are the arguments/keyword arguments passed to the
        # transition.
        pass