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
State: 状态
Event: 事件. 事件触发状态变换
Action: 动作. event发生前或后执行的动作
transition: 变换. 状态变换
github
https://github.com/pytransitions/transitions
安装
1 | pip install transitions |
简单示例
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 | # 连接协议状态机from transitions.extensions import HierarchicalMachine as Machinefrom transitions.extensions.nesting import NestedStateclass 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 1 self.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 2 self.machine.add_transition('disconnect', "STATE_CONNECTED", "STATE_NOT_CONNECTED") # transition 3 self.machine.add_transition('select', "STATE_CONNECTED_NOT_SELECTED", "STATE_CONNECTED_SELECTED") # transition 4 self.machine.add_transition('deselect', "STATE_CONNECTED_SELECTED", "STATE_CONNECTED_NOT_SELECTED") # transition 5 self.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
1 2 3 4 5 6 7 | # 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
1 2 3 4 5 6 7 | # 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
1 2 3 4 5 6 7 8 9 10 | # 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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