transitions-Python轻量级、面向对象的有限状态机实现

# <a name="transitions-module"></a> transitions [](https://github.com/pytransitions/transitions) [](https://github.com/pytransitions/transitions/actions?query=workflow%3Apytest) [](https://coveralls.io/github/pytransitions/transitions?branch=master) [](https://pypi.org/project/transitions) [](https://copr.fedorainfracloud.org/coprs/aleneum/python-transitions/) [](https://github.com/pytransitions/transitions/compare/0.9.2...master) [](LICENSE) [](https://mybinder.org/v2/gh/pytransitions/transitions/master?filepath=examples%2FPlayground.ipynb) <!-- [](https://github.com/pytransitions/transitions) --> <!--[](Link)--> A lightweight, object-oriented state machine implementation in Python with many extensions. Compatible with Python 2.7+ and 3.0+. ## Installation pip install transitions ... or clone the repo from GitHub and then: python setup.py install ## Table of Contents - [Quickstart](#quickstart) - [Non-Quickstart](#the-non-quickstart) - [Some key concepts](#some-key-concepts) - [Basic initialization](#basic-initialization) - [States](#states) - [Callbacks](#state-callbacks) - [Checking state](#checking-state) - [Enumerations](#enum-state) - [Transitions](#transitions) - [Triggering a transition](#triggers) - [Automatic transitions](#automatic-transitions-for-all-states) - [Transitioning from multiple states](#transitioning-from-multiple-states) - [Reflexive transitions from multiple states](#reflexive-from-multiple-states) - [Internal transitions](#internal-transitions) - [Ordered transitions](#ordered-transitions) - [Queued transitions](#queued-transitions) - [Conditional transitions](#conditional-transitions) - [Check transitions](#check-transitions) - [Callbacks](#transition-callbacks) - [Callable resolution](#resolution) - [Callback execution order](#execution-order) - [Passing data](#passing-data) - [Alternative initialization patterns](#alternative-initialization-patterns) - [Logging](#logging) - [(Re-)Storing machine instances](#restoring) - [Typing support](#typing-support) - [Extensions](#extensions) - [Hierarchical State Machine](#hsm) - [Diagrams](#diagrams) - [Threading](#threading) - [Async](#async) - [State features](#state-features) - [Django](#django-support) - [Bug reports etc.](#bug-reports) ## Quickstart They say [a good example is worth](https://www.google.com/webhp?ie=UTF-8#q=%22a+good+example+is+worth%22&start=20) 100 pages of API documentation, a million directives, or a thousand words. Well, "they" probably lie... but here's an example anyway: ```python from transitions import Machine import random class NarcolepticSuperhero(object): # Define some states. Most of the time, narcoleptic superheroes are just like # everyone else. Except for... states = ['asleep', 'hanging out', 'hungry', 'sweaty', 'saving the world'] def __init__(self, name): # No anonymous superheroes on my watch! Every narcoleptic superhero gets # a name. Any name at all. SleepyMan. SlumberGirl. You get the idea. self.name = name # What have we accomplished today? self.kittens_rescued = 0 # Initialize the state machine self.machine = Machine(model=self, states=NarcolepticSuperhero.states, initial='asleep') # Add some transitions. We could also define these using a static list of # dictionaries, as we did with states above, and then pass the list to # the Machine initializer as the transitions= argument. # At some point, every superhero must rise and shine. self.machine.add_transition(trigger='wake_up', source='asleep', dest='hanging out') # Superheroes need to keep in shape. self.machine.add_transition('work_out', 'hanging out', 'hungry') # Those calories won't replenish themselves! self.machine.add_transition('eat', 'hungry', 'hanging out') # Superheroes are always on call. ALWAYS. But they're not always # dressed in work-appropriate clothing. self.machine.add_transition('distress_call', '*', 'saving the world', before='change_into_super_secret_costume') # When they get off work, they're all sweaty and disgusting. But before # they do anything else, they have to meticulously log their latest # escapades. Because the legal department says so. self.machine.add_transition('complete_mission', 'saving the world', 'sweaty', after='update_journal') # Sweat is a disorder that can be remedied with water. # Unless you've had a particularly long day, in which case... bed time! self.machine.add_transition('clean_up', 'sweaty', 'asleep', conditions=['is_exhausted']) self.machine.add_transition('clean_up', 'sweaty', 'hanging out') # Our NarcolepticSuperhero can fall asleep at pretty much any time. self.machine.add_transition('nap', '*', 'asleep') def update_journal(self): """ Dear Diary, today I saved Mr. Whiskers. Again. """ self.kittens_rescued += 1 @property def is_exhausted(self): """ Basically a coin toss. """ return random.random() < 0.5 def change_into_super_secret_costume(self): print("Beauty, eh?") ``` There, now you've baked a state machine into `NarcolepticSuperhero`. Let's take him/her/it out for a spin... ```python >>> batman = NarcolepticSuperhero("Batman") >>> batman.state 'asleep' >>> batman.wake_up() >>> batman.state 'hanging out' >>> batman.nap() >>> batman.state 'asleep' >>> batman.clean_up() MachineError: "Can't trigger event clean_up from state asleep!" >>> batman.wake_up() >>> batman.work_out() >>> batman.state 'hungry' # Batman still hasn't done anything useful... >>> batman.kittens_rescued 0 # We now take you live to the scene of a horrific kitten entreement... >>> batman.distress_call() 'Beauty, eh?' >>> batman.state 'saving the world' # Back to the crib. >>> batman.complete_mission() >>> batman.state 'sweaty' >>> batman.clean_up() >>> batman.state 'asleep' # Too tired to shower! # Another productive day, Alfred. >>> batman.kittens_rescued 1 ``` While we cannot read the mind of the actual batman, we surely can visualize the current state of our `NarcolepticSuperhero`.  Have a look at the [Diagrams](#diagrams) extensions if you want to know how. ## The non-quickstart A state machine is a _model_ of behavior composed of a finite number of _states_ and _transitions_ between those states. Within each state and transition some _action_ can be performed. A state machine needs to start at some _initial state_. When using `transitions`, a state machine may consist of multiple objects where some (_machines_) contain definitions for the manipulation of other (_models_). Below, we will look at some core concepts and how to work with them