Force transition to initial state

[Jakuko99]

• Python State Machine version: 2.3.6
• Python version: 3.10.4
• Operating System: Windows 10

Description

Is there a possiblity to force statemachine to transition from any state to initial state? I know that it could be possible to define these transitions in statemachine, but in my case that would require around 19 transitions and this would make it even more complex than it already is.

My initial state is called "STA" and from there it goes to "idle" and other states. For example I wanted to try to transition from idle back to STA, using self.send("STA"), but this raised an error Can't STA when in Idle. I there a way to force this transition or do I need to define each transition from every state to initial one by hand?

(I can't publish the entire statemachine or the underlying code as this project is made for a company and its purpose is to simulate one of their products)

What I Did

self.send("STA") # send statemachine to initial state

"""Exception has occurred: TransitionNotAllowed
Can't STA when in Idle."""

[fgmacedo]

Hi @Jakuko99, hope you’re doing well!

Could you clarify a bit more about what you mean by “complexity” here? Are you referring to the added complexity of defining extra events and transitions in your state machine?

This might be a matter of adjusting the level of abstraction when defining States, Events, and Transitions. In other words, what is leading you to want to force a transition that doesn’t map explicitly as part of the state machine’s flow? It sounds like you’re looking for a way to bypass the state machine logic and directly jump between states.

To answer your question directly, if you’re okay with skipping any state-specific activation or callbacks, you could set the current_state manually. This essentially bypasses the state machine’s transition logic. However, please be aware that bypassing the state machine's defined transitions can lead to unforeseen runtime behaviors, which the state machine is designed to prevent.

Let me know if this solution works for your case, or if we need to explore another option.

Best regards!

[Jakuko99]

By complexity in this case I mean that between the states are defined multiple cycles how the statemachine can transition between them. So I don't want to add another cycle that will only be doing returning to root state and nothing else.

The transition to root state is needed because if one of the clients that use this statemachine disconnects I need to return to this state and wait there until all clients are connected again. I am okay with skipping the state specific activations, but in the end if I can change current state to the one I currently need and call specific transition-action manually afterwards.

I think the solution you proposed could be sufficient for this use-case, I will try it and will let you know if it did the job.

Thank you a lot!

[fgmacedo]

Added #497 as an alternative syntax for easier definition of from "any" state transition... in your example, you could now write back_to_sta = STA.from_.any().

Closing the issue for now, please feel free to comment here, reopen or open a new issue.

Best regards!