Django-fsm first came out in 2010 and had a big update in 2.0 release at 2014, making it incompatible with earlier versions. Now, ten years later at 2024, it's been updated to version 3.0 and renamed viewflow.fsm.

This new version has a different API that doesn't work with the old one but is better suited for today's needs.

Migration guide:

https://github.com/viewflow/viewflow/wiki/django%E2%80%90fsm-to-viewflow.fsm-Migration-Guide

Finite state machine workflows is the declarative way to describe consecutive operation through set of states and transitions between them.

viewflow.fsm can help you manage rules and restrictions around moving from one state to another. The package could be used to get low level db-independent fsm implementation, or to wrap existing database model, and implement simple persistent workflow process with quickly bootstrapped UI.

All things are buit around viewflow.fsm.State. It is the special class slot, that can take a value only from a specific python enum or django enumeration type and that value can't be changed with simple assignement.

from enum import Enum
from viewflow.fsm import State

class Stage(Enum):
   NEW = 1
   DONE = 2
   HIDDEN = 3


class MyFlow(object):
   state = State(Stage, default=Stage.NEW)

   @state.transition(source=Stage.NEW, target=Stage.DONE)
   def complete():
       pass

   @state.transition(source=State.ANY, target=Stage.HIDDEN)
   def hide():
       pass

flow = MyFlow()
flow.state == Stage.NEW  # True
flow.state = Stage.DONE  # Raises AttributeError

flow.complete()
flow.state == Stage.DONE  # True

flow.complete()  # Now raises TransitionNotAllowed

Full documentation available at https://docs.viewflow.io/fsm/index.html