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Super State Machine

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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:

  .. code-block:: python

  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:

  .. code-block:: python

  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:

.. code-block:: python

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