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[^] | jump | up | . | . |
| up | fall | 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[^] | jump | up | . | . |
| @up | fall | 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 | gets petted | wags tail | . | . |
| lies down[$] | . | . | . | . |
| sits[^] | squirrel! | barks | . | . |
| wags tail | gets petted | 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[^] | 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 |
+------------+-------------+---------+----------------+---------------+
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[^] | 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 |
+-----------+-------------+---------+----------------+---------------+
Note
As can be seen the two tables from this example and the prior one are exactly the same.
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