Super State Machine

https://pypip.in/d/super_state_machine/badge.png

Super State Machine gives you utilities to build finite state machines.

Free software: BSD license
Documentation: https://super_state_machine.readthedocs.org
Source: https://github.com/beregond/super_state_machine

Features

Fully tested with Python 2.7, 3.3, 3.4 and PyPy.

Create finite state machines:

>>> from enum import Enum

>>> from super_state_machine import machines


>>> class Task(machines.StateMachine):
...
...    state = 'draft'
...
...    class States(Enum):
...
...         DRAFT = 'draft'
...         SCHEDULED = 'scheduled'
...         PROCESSING = 'processing'
...         SENT = 'sent'
...         FAILED = 'failed'

>>> task = Task()
>>> task.is_draft
False
>>> task.set_draft()
>>> task.state
'draft'
>>> task.state = 'scheduled'
>>> task.is_scheduled
True
>>> task.state = 'process'
>>> task.state
'processing'
>>> task.state = 'wrong'
*** ValueError: Unrecognized value ('wrong').

Define allowed transitions graph, define additional named transitions and checkers:

>>> class Task(machines.StateMachine):
...
...     class States(Enum):
...
...         DRAFT = 'draft'
...         SCHEDULED = 'scheduled'
...         PROCESSING = 'processing'
...         SENT = 'sent'
...         FAILED = 'failed'
...
...     class Meta:
...
...         allow_empty = False
...         initial_state = 'draft'
...         transitions = {
...             'draft': ['scheduled', 'failed'],
...             'scheduled': ['failed'],
...             'processing': ['sent', 'failed']
...         }
...         named_transitions = [
...             ('process', 'processing', ['scheduled']),
...             ('fail', 'failed')
...         ]
...         named_checkers = [
...             ('can_be_processed', 'processing'),
...         ]

>>> task = Task()
>>> task.state
'draft'
>>> task.process()
*** TransitionError: Cannot transit from 'draft' to 'processing'.
>>> task.set_scheduled()
>>> task.can_be_processed
True
>>> task.process()
>>> task.state
'processing'
>>> task.fail()
>>> task.state
'failed'

Note, that third argument restricts from which states transition will be added to allowed (in case of process, new allowed transition will be added, from 'scheduled' to 'processing'). No argument means all available states, None or empty list won't add anything beyond defined ones.

Use state machines as properties:

>>> from enum import Enum

>>> from super_state_machine import machines, extras


>>> class Lock(machine.StateMachine):

...     class States(Enum):
...
...         OPEN = 'open'
...         LOCKED = 'locked'
...
...     class Meta:
...
...         allow_empty = False
...         initial_state = 'locked'
...         named_transitions = [
...             ('open', 'open'),
...             ('lock', 'locked'),
...         ]


>>> class Safe(object):
...
...     lock1 = extras.PropertyMachine(Lock)
...     lock2 = extras.PropertyMachine(Lock)
...     lock3 = extras.PropertyMachine(Lock)
...
...     locks = ['lock1', 'lock2', 'lock3']
...
...     def is_locked(self):
...          locks = [getattr(self, lock).is_locked for lock in self.locks]
...          return any(locks)
...
...     def is_open(self):
...         locks = [getattr(self, lock).is_open for lock in self.locks]
...         return all(locks)

>>> safe = Safe()
>>> safe.lock1
'locked'
>>> safe.is_open
False
>>> safe.lock1.open()
>>> safe.lock1.is_open
True
>>> safe.lock1
'open'
>>> safe.is_open
False
>>> safe.lock2.open()
>>> safe.lock3 = 'open'
>>> safe.is_open
True

beregond/super_state_machine

Super State Machine

Features