automaton/doc/source/user/examples.rst

Examples

Creating a simple machine

from automaton import machines m = machines.FiniteMachine() m.add_state('up') m.add_state('down') m.add_transition('down', 'up', 'jump') m.add_transition('up', 'down', 'fall') m.default_start_state = 'down' print(m.pformat())

Expected output:

Start	Event	End	On Enter	On Exit
down[^] up	jump fall	up down	.	.

Transitioning a simple machine

m.initialize() m.process_event('jump') print(m.pformat()) print(m.current_state) print(m.terminated) m.process_event('fall') print(m.pformat()) print(m.current_state) print(m.terminated)

Expected output:

Start	Event	End	On Enter	On Exit
down[^] @up	jump fall	up down	.	.

up False +----------+-------+------+----------+---------+ | Start | Event | End | On Enter | On Exit | +----------+-------+------+----------+---------+ | @down[^] | jump | up | . | . | | up | fall | down | . | . | +----------+-------+------+----------+---------+ down False

Running a complex dog-barking machine

from automaton import machines from automaton import runners

# These reaction functions will get triggered when the registered state # and event occur, it is expected to provide a new event that reacts to the # new stable state (so that the state-machine can transition to a new # stable state, and repeat, until the machine ends up in a terminal # state, whereby it will stop...)

def react_to_squirrel(old_state, new_state, event_that_triggered):

return "gets petted"

def react_to_wagging(old_state, new_state, event_that_triggered):

return "gets petted"

m = machines.FiniteMachine()

m.add_state("sits") m.add_state("lies down", terminal=True) m.add_state("barks") m.add_state("wags tail")

m.default_start_state = 'sits'

m.add_transition("sits", "barks", "squirrel!") m.add_transition("barks", "wags tail", "gets petted") m.add_transition("wags tail", "lies down", "gets petted")

m.add_reaction("barks", "squirrel!", react_to_squirrel) m.add_reaction('wags tail', "gets petted", react_to_wagging)

print(m.pformat()) r = runners.FiniteRunner(m) for (old_state, new_state) in r.run_iter("squirrel!"): print("Leaving '%s'" % old_state) print("Entered '%s'" % new_state)

Expected output:

Start	Event	End	On Enter	On Exit
barks lies down[$] sits[^] wags tail	gets petted . squirrel! gets petted	wags tail . barks lies down	. .	. .

Leaving 'sits' Entered 'barks' Leaving 'barks' Entered 'wags tail' Leaving 'wags tail' Entered 'lies down'

Creating a complex CD-player machine

from automaton import machines

def print_on_enter(new_state, triggered_event):

print("Entered '%s' due to '%s'" % (new_state, triggered_event))

def print_on_exit(old_state, triggered_event):

print("Exiting '%s' due to '%s'" % (old_state, triggered_event))

m = machines.FiniteMachine()

m.add_state('stopped', on_enter=print_on_enter, on_exit=print_on_exit) m.add_state('opened', on_enter=print_on_enter, on_exit=print_on_exit) m.add_state('closed', on_enter=print_on_enter, on_exit=print_on_exit) m.add_state('playing', on_enter=print_on_enter, on_exit=print_on_exit) m.add_state('paused', on_enter=print_on_enter, on_exit=print_on_exit)

m.add_transition('stopped', 'playing', 'play') m.add_transition('stopped', 'opened', 'open_close') m.add_transition('stopped', 'stopped', 'stop')

m.add_transition('opened', 'closed', 'open_close')

m.add_transition('closed', 'opened', 'open_close') m.add_transition('closed', 'stopped', 'cd_detected')

m.add_transition('playing', 'stopped', 'stop') m.add_transition('playing', 'paused', 'pause') m.add_transition('playing', 'opened', 'open_close')

m.add_transition('paused', 'playing', 'play') m.add_transition('paused', 'stopped', 'stop') m.add_transition('paused', 'opened', 'open_close')

m.default_start_state = 'closed'

m.initialize() print(m.pformat())

for event in ['cd_detected', 'play', 'pause', 'play', 'stop',

'open_close', 'open_close']: m.process_event(event) print(m.pformat()) print("=============") print("Current state => %s" % m.current_state) print("=============")

Expected output:

Start	Event	End	On Enter	On Exit
@closed[^] @closed[^] opened paused paused paused playing playing playing stopped stopped stopped	cd_detected open_close open_close open_close play stop open_close pause stop open_close play stop	stopped opened closed opened playing stopped opened paused stopped opened playing stopped	print_on_enter print_on_enter print_on_enter print_on_enter print_on_enter print_on_enter print_on_enter print_on_enter print_on_enter print_on_enter print_on_enter print_on_enter	print_on_exit print_on_exit print_on_exit print_on_exit print_on_exit print_on_exit print_on_exit print_on_exit print_on_exit print_on_exit print_on_exit print_on_exit

Exiting 'closed' due to 'cd_detected' Entered 'stopped' due to 'cd_detected' +-----------+-------------+---------+----------------+---------------+ | Start | Event | End | On Enter | On Exit | +-----------+-------------+---------+----------------+---------------+ | closed[^] | cd_detected | stopped | print_on_enter | print_on_exit | | closed[^] | open_close | opened | print_on_enter | print_on_exit | | opened | open_close | closed | print_on_enter | print_on_exit | | paused | open_close | opened | print_on_enter | print_on_exit | | paused | play | playing | print_on_enter | print_on_exit | | paused | stop | stopped | print_on_enter | print_on_exit | | playing | open_close | opened | print_on_enter | print_on_exit | | playing | pause | paused | print_on_enter | print_on_exit | | playing | stop | stopped | print_on_enter | print_on_exit | | @stopped | open_close | opened | print_on_enter | print_on_exit | | @stopped | play | playing | print_on_enter | print_on_exit | | @stopped | stop | stopped | print_on_enter | print_on_exit | +-----------+-------------+---------+----------------+---------------+ ============= Current state => stopped ============= Exiting 'stopped' due to 'play' Entered 'playing' due to 'play' +-----------+-------------+---------+----------------+---------------+ | Start | Event | End | On Enter | On Exit | +-----------+-------------+---------+----------------+---------------+ | closed[^] | cd_detected | stopped | print_on_enter | print_on_exit | | closed[^] | open_close | opened | print_on_enter | print_on_exit | | opened | open_close | closed | print_on_enter | print_on_exit | | paused | open_close | opened | print_on_enter | print_on_exit | | paused | play | playing | print_on_enter | print_on_exit | | paused | stop | stopped | print_on_enter | print_on_exit | | @playing | open_close | opened | print_on_enter | print_on_exit | | @playing | pause | paused | print_on_enter | print_on_exit | | @playing | stop | stopped | print_on_enter | print_on_exit | | stopped | open_close | opened | print_on_enter | print_on_exit | | stopped | play | playing | print_on_enter | print_on_exit | | stopped | stop | stopped | print_on_enter | print_on_exit | +-----------+-------------+---------+----------------+---------------+ ============= Current state => playing ============= Exiting 'playing' due to 'pause' Entered 'paused' due to 'pause' +-----------+-------------+---------+----------------+---------------+ | Start | Event | End | On Enter | On Exit | +-----------+-------------+---------+----------------+---------------+ | closed[^] | cd_detected | stopped | print_on_enter | print_on_exit | | closed[^] | open_close | opened | print_on_enter | print_on_exit | | opened | open_close | closed | print_on_enter | print_on_exit | | @paused | open_close | opened | print_on_enter | print_on_exit | | @paused | play | playing | print_on_enter | print_on_exit | | @paused | stop | stopped | print_on_enter | print_on_exit | | playing | open_close | opened | print_on_enter | print_on_exit | | playing | pause | paused | print_on_enter | print_on_exit | | playing | stop | stopped | print_on_enter | print_on_exit | | stopped | open_close | opened | print_on_enter | print_on_exit | | stopped | play | playing | print_on_enter | print_on_exit | | stopped | stop | stopped | print_on_enter | print_on_exit | +-----------+-------------+---------+----------------+---------------+ ============= Current state => paused ============= Exiting 'paused' due to 'play' Entered 'playing' due to 'play' +-----------+-------------+---------+----------------+---------------+ | Start | Event | End | On Enter | On Exit | +-----------+-------------+---------+----------------+---------------+ | closed[^] | cd_detected | stopped | print_on_enter | print_on_exit | | closed[^] | open_close | opened | print_on_enter | print_on_exit | | opened | open_close | closed | print_on_enter | print_on_exit | | paused | open_close | opened | print_on_enter | print_on_exit | | paused | play | playing | print_on_enter | print_on_exit | | paused | stop | stopped | print_on_enter | print_on_exit | | @playing | open_close | opened | print_on_enter | print_on_exit | | @playing | pause | paused | print_on_enter | print_on_exit | | @playing | stop | stopped | print_on_enter | print_on_exit | | stopped | open_close | opened | print_on_enter | print_on_exit | | stopped | play | playing | print_on_enter | print_on_exit | | stopped | stop | stopped | print_on_enter | print_on_exit | +-----------+-------------+---------+----------------+---------------+ ============= Current state => playing ============= Exiting 'playing' due to 'stop' Entered 'stopped' due to 'stop' +-----------+-------------+---------+----------------+---------------+ | Start | Event | End | On Enter | On Exit | +-----------+-------------+---------+----------------+---------------+ | closed[^] | cd_detected | stopped | print_on_enter | print_on_exit | | closed[^] | open_close | opened | print_on_enter | print_on_exit | | opened | open_close | closed | print_on_enter | print_on_exit | | paused | open_close | opened | print_on_enter | print_on_exit | | paused | play | playing | print_on_enter | print_on_exit | | paused | stop | stopped | print_on_enter | print_on_exit | | playing | open_close | opened | print_on_enter | print_on_exit | | playing | pause | paused | print_on_enter | print_on_exit | | playing | stop | stopped | print_on_enter | print_on_exit | | @stopped | open_close | opened | print_on_enter | print_on_exit | | @stopped | play | playing | print_on_enter | print_on_exit | | @stopped | stop | stopped | print_on_enter | print_on_exit | +-----------+-------------+---------+----------------+---------------+ ============= Current state => stopped ============= Exiting 'stopped' due to 'open_close' Entered 'opened' due to 'open_close' +-----------+-------------+---------+----------------+---------------+ | Start | Event | End | On Enter | On Exit | +-----------+-------------+---------+----------------+---------------+ | closed[^] | cd_detected | stopped | print_on_enter | print_on_exit | | closed[^] | open_close | opened | print_on_enter | print_on_exit | | @opened | open_close | closed | print_on_enter | print_on_exit | | paused | open_close | opened | print_on_enter | print_on_exit | | paused | play | playing | print_on_enter | print_on_exit | | paused | stop | stopped | print_on_enter | print_on_exit | | playing | open_close | opened | print_on_enter | print_on_exit | | playing | pause | paused | print_on_enter | print_on_exit | | playing | stop | stopped | print_on_enter | print_on_exit | | stopped | open_close | opened | print_on_enter | print_on_exit | | stopped | play | playing | print_on_enter | print_on_exit | | stopped | stop | stopped | print_on_enter | print_on_exit | +-----------+-------------+---------+----------------+---------------+ ============= Current state => opened ============= Exiting 'opened' due to 'open_close' Entered 'closed' due to 'open_close' +------------+-------------+---------+----------------+---------------+ | Start | Event | End | On Enter | On Exit | +------------+-------------+---------+----------------+---------------+ | @closed[^] | cd_detected | stopped | print_on_enter | print_on_exit | | @closed[^] | open_close | opened | print_on_enter | print_on_exit | | opened | open_close | closed | print_on_enter | print_on_exit | | paused | open_close | opened | print_on_enter | print_on_exit | | paused | play | playing | print_on_enter | print_on_exit | | paused | stop | stopped | print_on_enter | print_on_exit | | playing | open_close | opened | print_on_enter | print_on_exit | | playing | pause | paused | print_on_enter | print_on_exit | | playing | stop | stopped | print_on_enter | print_on_exit | | stopped | open_close | opened | print_on_enter | print_on_exit | | stopped | play | playing | print_on_enter | print_on_exit | | stopped | stop | stopped | print_on_enter | print_on_exit | +------------+-------------+---------+----------------+---------------+ ============= Current state => closed =============

Creating a complex CD-player machine (using a state-space)

This example is equivalent to the prior one but creates a machine in a more declarative manner. Instead of calling add_state and add_transition a explicit and declarative format can be used. For example to create the same machine:

from automaton import machines

def print_on_enter(new_state, triggered_event):

print("Entered '%s' due to '%s'" % (new_state, triggered_event))

def print_on_exit(old_state, triggered_event):

print("Exiting '%s' due to '%s'" % (old_state, triggered_event))

# This will contain all the states and transitions that our machine will # allow, the format is relatively simple and designed to be easy to use. state_space = [ { 'name': 'stopped', 'next_states': { # On event 'play' transition to the 'playing' state. 'play': 'playing', 'open_close': 'opened', 'stop': 'stopped', }, 'on_enter': print_on_enter, 'on_exit': print_on_exit, }, { 'name': 'opened', 'next_states': { 'open_close': 'closed', }, 'on_enter': print_on_enter, 'on_exit': print_on_exit, }, { 'name': 'closed', 'next_states': { 'open_close': 'opened', 'cd_detected': 'stopped', }, 'on_enter': print_on_enter, 'on_exit': print_on_exit, }, { 'name': 'playing', 'next_states': { 'stop': 'stopped', 'pause': 'paused', 'open_close': 'opened', }, 'on_enter': print_on_enter, 'on_exit': print_on_exit, }, { 'name': 'paused', 'next_states': { 'play': 'playing', 'stop': 'stopped', 'open_close': 'opened', }, 'on_enter': print_on_enter, 'on_exit': print_on_exit, }, ]

m = machines.FiniteMachine.build(state_space) m.default_start_state = 'closed' print(m.pformat())

Expected output:

Start	Event	End	On Enter	On Exit
closed[^] closed[^] opened paused paused paused playing playing playing stopped stopped stopped	cd_detected open_close open_close open_close play stop open_close pause stop open_close play stop	stopped opened closed opened playing stopped opened paused stopped opened playing stopped	print_on_enter print_on_enter print_on_enter print_on_enter print_on_enter print_on_enter print_on_enter print_on_enter print_on_enter print_on_enter print_on_enter print_on_enter	print_on_exit print_on_exit print_on_exit print_on_exit print_on_exit print_on_exit print_on_exit print_on_exit print_on_exit print_on_exit print_on_exit print_on_exit

Note

As can be seen the two tables from this example and the prior one are exactly the same.