Usage¶

Define in a class the state_machine
Initialize state, either with a value, using __init__ or as a django field
Add hooks:

Method	Description
on_before_change_state	Before transitioning to the state
on_change_state	After transitioning to the state, if no failure, runs for every state
pre_<state_name>	Runs before a particular state, where `state_name` is the specified name in the `state_machine`
post_<state_name>	Runs after a particular state, where `state_name` is the specified name in the `state_machine`

This hooks will receive any extra argument given to change_state

E.g:

Running m.change_state('pending', name='john') will trigger pre_pending(name='john')

In your code¶

To use Python Finite State Machine in a project:

import fsm

Then add the Mixin to any class where the state machine is required.

class Foo(fsm.FiniteStateMachineMixin):

    state_machine = {
        'my_first_state': '__all__',
        'my_state': ('my_second_state',),
        'my_second_state': ('my_state', 'my_second_state', 'last_state'),
        'last_state': None
    }

    state = 'my_first_state'

Instanciate the class and use it. Remember that in order to work as intended, change_state must be used to transition from one state to the other.

>>> foo = Foo()

>>> foo.current_state()
'my_first_state'

>>> foo.change_state('my_state')
'my_state'

>>> foo.current_state()
'my_state'

>>> foo.can_change('last_state')
False

>>> foo.get_valid_transitions()
('my_second_state',)

You can also use BaseFiniteStateMachineMixin for more flexibility. Implementing current_state and set_state is required. Doing this allows using more complex behavior, but it is not recommended.