python-automaton 1.2.1

A minimal Python finite-state machine.

Automaton requires Python version 3.4 or greater.

Automaton is an easy to use, easy to maintain finite-state machine package for Python 3.4 or greater. The goal here is to have something minimal to enforce correctness and to avoid clutter from useless features.

In order to define an automaton, just subclass a provided base:

>>> from automaton import *
>>>
>>> class TrafficLight(Automaton):
>>>
>>>     go = Event("red", "green")
>>>     slowdown = Event("green", "yellow")
>>>     stop = Event("yellow", "red")

You’re done: you now have a new automaton definition that can be instantiated and used as a state machine:

>>> crossroads = TrafficLight(initial_state="red")
>>> crossroads.state
"red"

The automaton can be operated via events: signalling the occurrence of an event to the state machine triggers the evolution of the automaton from an initial state to a final state. You can trigger an event calling the class attributes themeselves:

>>> crossroads.go()
>>> crossroads.state
"green"
>>> crossroads.slowdown()
>>> crossroads.state
"yellow"

An alternative way, more convenient if triggering events progammatically, is to call the event() method:

>>> crossroads.event("stop")
>>> crossroads.state
"red"

Automaton enforces correctness in two ways:

1. checking that the requested event is valid, that is a transition from the current state to the destination state exists in the state machine definition;

2. checking whether the state graph representing the automaton is connected or not (that is it must have only one connected component).