python 实用工具状态机transitions

说明

1. 状态机是一个非常实用的理论。在涉及到复杂的场景，建立状态机模型，能带来极大的方便。比如，网络连接、模型状态、业务逻辑。 2. 状态机并不复杂, 重要的是它的思想，能够极大减轻复杂度。使用时关键在于定义好事件和动作。

基本概念

github

https://github.com/pytransitions/transitions

安装

pip install transitions

简单示例

# 连接协议状态机from transitions.extensions import HierarchicalMachine as Machinefrom transitions.extensions.nesting import NestedState class ConnectionStateMachine: '''Connection state machine.''' def __init__(self, callbacks=None):''':param callbacks: callbacks for the state machine'''self.callbacks = {} # 定义状态self.states = ['STATE_NOT_CONNECTED', { ’name’: 'STATE_CONNECTED', # 状态名 ’on_enter’: self._on_enter_CONNECTED, # 进入状态触发 ’on_exit’: self._on_exit_CONNECTED, # 退出状态触发 ’children’: [ # 状态嵌套'STATE_NOT_SELECTED',{ ’name’: 'STATE_SELECTED', ’on_enter’: self._on_enter_CONNECTED_SELECTED} ] }] # transition 1self.machine = Machine(model=self, states=self.states, initial='STATE_NOT_CONNECTED', auto_transitions=False) if callbacks: self.callbacks = callbacks # 定义状态变换self.machine.add_transition(’connect’, 'STATE_NOT_CONNECTED', 'STATE_CONNECTED_NOT_SELECTED') # transition 2self.machine.add_transition(’disconnect’, 'STATE_CONNECTED', 'STATE_NOT_CONNECTED') # transition 3self.machine.add_transition(’select’, 'STATE_CONNECTED_NOT_SELECTED', 'STATE_CONNECTED_SELECTED') # transition 4self.machine.add_transition(’deselect’, 'STATE_CONNECTED_SELECTED', 'STATE_CONNECTED_NOT_SELECTED') # transition 5self.machine.add_transition(’timeoutT7’, 'STATE_CONNECTED_NOT_SELECTED', 'STATE_NOT_CONNECTED') # transition 6 # 事件触发的动作 def _on_enter_CONNECTED(self):if 'on_enter_CONNECTED' in self.callbacks: self.callbacks['on_enter_CONNECTED']() def _on_exit_CONNECTED(self):if 'on_exit_CONNECTED' in self.callbacks: self.callbacks['on_exit_CONNECTED']() def _on_enter_CONNECTED_SELECTED(self):if 'on_enter_CONNECTED_SELECTED' in self.callbacks: self.callbacks['on_enter_CONNECTED_SELECTED']()

定义状态机

# 一般都是两种：不嵌套、嵌套from transitions import Machine #不嵌套from transitions.extensions import HierarchicalMachine as Machine # 嵌套 # 检查状态machine.statemachine.is_<state_name>()

定义状态

# 状态可以是三种类型: 对象、字符串、字典from transitions import Statestates = [ State(name='solid'), # 对象 'liquid', # 字符串 {'name': 'gas'} # 字典]

定义变换

# 定义函数machine.add_transition(trigger, source, dest, )trigger(str) 方法名,触发状态转换source(str or list) 源状态dest(str) 目标状态 # 加上变换machine.add_transition(trigger='wake_up', source='asleep', dest='hanging out')machine.add_transition(’work_out’, ’hanging out’, ’hungry’)machine.add_transition(’nap’, ’*’, ’asleep’) # 从任意状态变为asleep

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