[jononor]

Your example is a standard Finite State Machine. Multiple possible transitions is the norm for an FSM, and each possible transition is guarded by some predicate which decides if it should be followed.

# transition notation: FromState -predicate-> ToState

    Running -stop_button-> Stopped
    Stopped -start_button-> Running
    Running -start_button-> Running # stay running
    Stopped -stop_button-> Stopped # stay stopped

The stop/start_button button here can either be events that come in from the outside (from dedicated click handlers in a GUI), or be functions or properties that are polled when evaluating next().

Since booting a VM can take quite some time, one might want to introduce a Starting state between Stopped and Running.

The example in the original article is just a special case, where there is only one possible transition from each state, and where the predicate always returns true. Although arguably for a real traffic light, there should be a predicate on the transition that checks that enough time has passed! At least I would model that as part of the FSM, instead of on the outside.

EDIT: fix formatting