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Django friendly finite state machine support

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django-fsm adds simple declarative state management for django models.

If you need parallel task execution, view and background task code reuse over different flows - check my new project django-viewflow:

Instead of adding a state field to a django model and managing its values by hand, you use FSMField and mark model methods with the transition decorator. These methods could contain side-effects of the state change.

Nice introduction is available here:

You may also take a look at django-fsm-admin project containing a mixin and template tags to integrate django-fsm state transitions into the django admin.

Transition logging support could be achieved with help of django-fsm-log package

FSM really helps to structure the code, especially when a new developer comes to the project. FSM is most effective when you use it for some sequential steps.


Or, for the latest git version

The library has full Python 3 support


Add FSMState field to your model

Use the transition decorator to annotate model methods

The field parameter accepts both a string attribute name or an actual field instance.

If calling publish() succeeds without raising an exception, the state field will be changed, but not written to the database.

If some conditions are required to be met before changing the state, use the conditions argument to transition. conditions must be a list of functions taking one argument, the model instance. The function must return either True or False or a value that evaluates to True or False. If all functions return True, all conditions are considered to be met and the transition is allowed to happen. If one of the functions returns False, the transition will not happen. These functions should not have any side effects.

You can use ordinary functions

Or model methods

Use the conditions like this:

You can instantiate a field with protected=True option to prevent direct state field modification.

Note that calling refresh_from_db on a model instance with a protected FSMField will cause an exception.

source state

source parameter accepts a list of states, or an individual state or django_fsm.State implementation.

You can use * for source to allow switching to target from any state.

You can use + for source to allow switching to target from any state excluding target state.

target state

target state parameter could point to a specific state or django_fsm.State implementation

custom properties

Custom properties can be added by providing a dictionary to the custom keyword on the transition decorator.

on_error state

If the transition method raises an exception, you can provide a specific target state


Instead of passing a two-item iterable choices you can instead use the three-element state_choices, the last element being a string reference to a model proxy class.

The base class instance would be dynamically changed to the corresponding Proxy class instance, depending on the state. Even for queryset results, you will get Proxy class instances, even if the QuerySet is executed on the base class.

Check the test case for example usage. Or read about implementation internals


It is common to have permissions attached to each model transition. django-fsm handles this with permission keyword on the transition decorator. permission accepts a permission string, or callable that expects instance and user arguments and returns True if the user can perform the transition.

You can check permission with has_transition_permission method

Model methods

get_all_FIELD_transitions Enumerates all declared transitions

get_available_FIELD_transitions Returns all transitions data available in current state

get_available_user_FIELD_transitions Enumerates all transitions data available in current state for provided user

Foreign Key constraints support

If you store the states in the db table you could use FSMKeyField to ensure Foreign Key database integrity.

In your model :

In your fixtures/initial_data.json :

Note : source and target parameters in @transition decorator use pk values of DBState model as names, even if field "real" name is used, without _id postfix, as field parameter.

Integer Field support

You can also use FSMIntegerField. This is handy when you want to use enum style constants.


django_fsm.signals.pre_transition and django_fsm.signals.post_transition are called before and after allowed transition. No signals on invalid transition are called.

Arguments sent with these signals:

sender The model class.

instance The actual instance being processed

name Transition name

source Source model state

target Target model state

Optimistic locking

django-fsm provides optimistic locking mixin, to avoid concurrent model state changes. If model state was changed in database django_fsm.ConcurrentTransition exception would be raised on

For guaranteed protection against race conditions caused by concurrently executed transitions, make sure:

  • Your transitions do not have any side effects except for changes in the database,
  • You always run the save() method on the object within django.db.transaction.atomic() block.

Following these recommendations, you can rely on ConcurrentTransitionMixin to cause a rollback of all the changes that have been executed in an inconsistent (out of sync) state, thus practically negating their effect.

Drawing transitions

Renders a graphical overview of your models states transitions

You need pip install "graphviz>=0.4" library and add django_fsm to your INSTALLED_APPS:


django-fsm 2.8.2 2024-04-09

  • Fix graph_transitions commnad for Django>=4.0
  • Preserve chosen "using" DB in ConcurentTransitionMixin
  • Fix error message in GET_STATE
  • Implement Transition __hash__ and __eq__ for 'in' operator