super_state_machine 1.0

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

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):
  ...
  ...    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 = 'p'
  >>> 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.

• You can also define short version of all transition values like:

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

  Result code will behave the same as example above. Note also that you can always pass also enum values instead of strings.

History

1.0 (2014-09-04)

• Added all basic features.

0.1.0 (2014-08-08)

• First release on PyPI.

• Added utilities to create simple state machine.