Welcome to StateMachine’s documentation!¶

Getting Started¶

The State Machine is used to implement a workflow. Through a transition you change from one state to another. The current state determines the behavior.

Context¶

The Context serves as an interface between the state machine and the client . It delegates a request from the client to the current state. Depending on the current state, the request results in a different behavior.

The following example shows how to create a context and load a state by its name:

from state_machine.context import Context

context = Context()
context.load_state("RegisteredState")
context.change_state()

State¶

Each state is modeled as a JSON document with two set of strategies (create_study and change_state) that dictates a set of behaviors.

The existing states need to be passed to the context. Here is an example:

{
    "name" : "RegisteredState",
    "strategies_create_study" : [
        {
            "name" : "expression",
            "value" : "len(kwargs.get('datasets', [])) > 0",
            "state_if_true" : "DatasetState"
        }
    ],
    "strategies_change_state" : [
        {
            "name" : "expression",
            "value" : "len(kwargs.get('datasets', [])) > 0",
            "state_if_true" : "DatasetState"
        }
    ]
}

study_state_machine¶

study_state_machine package¶

Subpackages¶

Submodules¶

study_state_machine.context module¶

Implementation of a finite state machine for studies

class study_state_machine.context.Context(available_states, initial_state=None)¶

Bases: object

Only if an initial state is passed to the constructor, the context of the current state is set. Otherwise, call transition_to() or load_state() with a name of a State, respectively

add_sample(*args, **kwargs)¶

property available_states¶

change_state(*args, **kwargs)¶

create_study(*args, **kwargs)¶

property current_state¶

get_state_dict(state_name)¶

load_state(state_name)¶

Load state with given name

Parameters: state_name – Name of the state
Raises: StateNotFoundException – If the state is not found

parse_strategies(strategies, *args, **kwargs)¶: Parse strategies list and return a state to be transitioned to

transition_to(state_name)¶

Set state as the new current state and set its context

Parameters: state_name – new current state

study_state_machine.errors module¶

Collection of state machine related exceptions.

All exceptions inherit from StateMachineException

exception study_state_machine.errors.BehaviorNotAllowedException¶

Bases: study_state_machine.errors.StateMachineException

Exception if a state does not support a behavior

exception study_state_machine.errors.StateMachineException¶

Bases: Exception

Generic state machine error

exception study_state_machine.errors.StateNotFoundException¶

Bases: study_state_machine.errors.StateMachineException

Exception if state is not found by its name

study_state_machine.interfaces module¶

class study_state_machine.interfaces.IState(context=None)¶

Bases: abc.ABC

Base class for all states.

The state has a reference to the context in order to change into the next state.

property context¶

class study_state_machine.interfaces.IStudyState(context=None)¶

Bases: study_state_machine.interfaces.IState

Base class for all study states

add_sample(*args, **kwargs)¶

change_state(*args, **kwargs)¶

create_study(*args, **kwargs)¶