openstack/automaton
Code Issues Proposed changes

Add a state-space machine building example

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We currently don't have an example that uses a state
space to build a machine, so in order to make people aware
of this ability add an example that uses it to build a simple
state machine.

Change-Id: Ieec71ceee14f2bb451a52457d1a05aa54898597c
This commit is contained in:
Joshua Harlow 2016-01-22 10:52:39 -08:00
parent 9f74d1f886
commit 3f93f01330
1 changed files with 105 additions and 0 deletions
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105
doc/source/examples.rst
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@ -131,6 +131,7 @@ Running a complex dog-barking machine
Leaving 'wags tail' Leaving 'wags tail'
Entered 'lies down' Entered 'lies down'
------------------------------------ ------------------------------------
Creating a complex CD-player machine Creating a complex CD-player machine
------------------------------------ ------------------------------------
@ -355,3 +356,107 @@ Creating a complex CD-player machine
============= =============
Current state => closed 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:
.. testcode::
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:**
.. testoutput::
+-----------+-------------+---------+----------------+---------------+
| 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.