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Python "state machine" module

README.rst

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 2.6 to 3.3

Links

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
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