Limiting Cycle To At Most One Transition - prior_state or last_transition variable?

[slowrunner]

The Brooks 84 "Subsumption Architecture For Mobile Robots" describes a hierarchy of robot behaviors as layers of state machines.

I would like to limit a machine "cycle" to 0-1 transition.

In the current python-statemachine implementation with

• tests of external robot values/events in the on_enter_stateA()
• actions in on_transitionA2B,
• and cycle = stateA.to.itself() | stateB.to.itself() ...

a loop on statemachine.cycle() will "free run" until no transitions are possible.

If the statemachine maintained a "prior_state" variable or "last_transition" variable, then I could add a check in each on_enter_stateXYZ() to ensure entry is a "reentry" or the null/cycle transition. This would allow limiting the cycle to 0-1 transitions.

Lacking this, I could

• set a variable "nullTransition" True in on_cycle()
• add a check in every on_enter_stateX() to only transition out of the state if nullTransition is true.
• reset the nullTransition var in the on_enter_stateX() before performing the transition

This is a bit cluttered, but allows the existing python-statemachine package to work for my purposes.

[fgmacedo]

Hi, starting from 1.0.0 you can add the parameter source in a callback, it points to the origin state in a transition.

This helps?

Closing as this is stale for a while. Feel free to reach out if you have any other questions.

Best!