Create a global event

[yoavweber]

Hello,

Can I create a global event that would not be bound to one state?
For example:

class TrafficLightMachine(StateMachine):
    "A traffic light machine"
    green = State("Green", initial=True)
    yellow = State("Yellow")
    red = State("Red")

    honk = ?


    def on_honk(self):
            print("honk)

How should I define honk so it can be triggered in any state?

Thanks!

[fgmacedo]

Hi @yoavweber ,

One example of solution is to create internal transitions on each state:

class TrafficLightMachine(StateMachine):
    "A traffic light machine"
    green = State("Green", initial=True)
    yellow = State("Yellow")
    red = State("Red")

    honk = green.to.itself(internal=True) | yellow.to.itself(internal=True) | red.to.itself(internal=True)

    def on_honk(self):
            print("honk")

1. The state will NOT be changed.
2. The on_enter* or on_exit* hooks will NOT be called.
3. The on_hook will be called.

If this not helps, can you elaborate more your expected behaviour?

1. How could honk be triggered?
2. What you expect to happen when honk is triggered?
3. Is there any change in state?
4. Is there any blocking to only occour on a specific state?
5. Do the other on_enter_<state> or on_exit_<state> hooks be called?

Please refer to these docs, they can help clarify the current behaviour:

1. https://python-statemachine.readthedocs.io/en/develop/transitions.html
2. https://python-statemachine.readthedocs.io/en/develop/actions.html
3. https://python-statemachine.readthedocs.io/en/develop/guards.html

Best regards!

[yoavweber]

Hey @fgmacedo
Thanks for the replay! I believe this is what I was looking for, but I am getting the following error:
TypeError: Transition.__init__() got an unexpected keyword argument 'internal'

to trigger the event, I am doing the following:

test = TrafficLightMachine()
test.honk()

I am using:
python: 3.10
python-statemachine: 1.0.3

Is there other information I could provide?

[yoavweber]

I took a look at the source code, the installed package is not reflected the current state of the repository.

class Transition(object):
    """A transition holds reference to the source and target state.

    Args:
        source (State): The origin state of the transition.
        target (State): The target state of the transition.
        event (Optional[Union[str, List[str]]]): List of designators of events that trigger this
            transition. Can be either a list of strings, or a space-separated string list of event
            descriptors.
        validators (Optional[Union[str, Callable, List[Callable]]]): The validation callbacks to
            be invoked before the transition is executed.
        cond (Optional[Union[str, Callable, List[Callable]]]): The condition callbacks to be
            invoked before the transition is executed that should evaluate to `True`.
        unless (Optional[Union[str, Callable, List[Callable]]]): The condition callbacks to be
            invoked if the `cond` is False before the transition is executed.
        on (Optional[Union[str, Callable, List[Callable]]]): The callbacks to be invoked
            when the transition is executed.
        before (Optional[Union[str, Callable, List[Callable]]]): The callbacks to be invoked
            before the transition is executed.
        after (Optional[Union[str, Callable, List[Callable]]]): The callbacks to be invoked
            after the transition is executed.
    """

    def __init__(
        self,
        source,
        target,
        event=None,
        validators=None,
        cond=None,
        unless=None,
        on=None,
        before=None,
        after=None,
    ):
...

While in the repository Transition class is supporting the internal attribute:

class Transition:
    """A transition holds reference to the source and target state.

    ...
    """

    def __init__(
        self,
        source,
        target,
        event=None,
        internal=False, # <------------------------------
        validators=None,
        cond=None,
        unless=None,
        on=None,
        before=None,
        after=None,
    ):

...

[fgmacedo]

Yes, you're right. I've pointed you to a new feature that is planned to be landing in 2.0: https://python-statemachine.readthedocs.io/en/develop/releases/2.0.0.html#what-s-new-in-2-0

On the development branch there's a huge refactoring, as I removed backwards compatibility with older python versions.

My plan is to release 2.0 after #329.

I've fixed the default documentation link to open latest instead of develop.

Best regards!

[yoavweber]

Ok, I see. Thank you for clarifying and for maintaining this project!

[fgmacedo]

@yoavweber the new version was released.