python 實用工具狀態機transitions

說明

1. 狀態機是一個非常實用的理論。在涉及到復雜的場景，建立狀態機模型，能帶來極大的方便。比如，網絡連接、模型狀態、業務邏輯。 2. 狀態機并不復雜, 重要的是它的思想，能夠極大減輕復雜度。使用時關鍵在于定義好事件和動作。

基本概念

State: 狀態 Event: 事件. 事件觸發狀態變換 Action: 動作. event發生前或后執行的動作 transition: 變換. 狀態變換

github

https://github.com/pytransitions/transitions

安裝

pip install transitions

簡單示例

# 連接協議狀態機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 = {} # 定義狀態self.states = ['STATE_NOT_CONNECTED', { ’name’: 'STATE_CONNECTED', # 狀態名 ’on_enter’: self._on_enter_CONNECTED, # 進入狀態觸發 ’on_exit’: self._on_exit_CONNECTED, # 退出狀態觸發 ’children’: [ # 狀態嵌套'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 # 定義狀態變換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 # 事件觸發的動作 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']()

定義狀態機

# 一般都是兩種：不嵌套、嵌套from transitions import Machine #不嵌套from transitions.extensions import HierarchicalMachine as Machine # 嵌套 # 檢查狀態machine.statemachine.is_<state_name>()

定義狀態

# 狀態可以是三種類型: 對象、字符串、字典from transitions import Statestates = [ State(name='solid'), # 對象 'liquid', # 字符串 {'name': 'gas'} # 字典]

定義變換

# 定義函數machine.add_transition(trigger, source, dest, )trigger(str) 方法名,觸發狀態轉換source(str or list) 源狀態dest(str) 目標狀態 # 加上變換machine.add_transition(trigger='wake_up', source='asleep', dest='hanging out')machine.add_transition(’work_out’, ’hanging out’, ’hungry’)machine.add_transition(’nap’, ’*’, ’asleep’) # 從任意狀態變為asleep

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