python 状态机教程_python 实用工具状态机transitions
說明
1. 狀態(tài)機(jī)是一個(gè)非常實(shí)用的理論。在涉及到復(fù)雜的場(chǎng)景，建立狀態(tài)機(jī)模型，能帶來極大的方便。比如，網(wǎng)絡(luò)連接、模型狀態(tài)、業(yè)務(wù)邏輯。
2. 狀態(tài)機(jī)并不復(fù)雜, 重要的是它的思想，能夠極大減輕復(fù)雜度。使用時(shí)關(guān)鍵在于定義好事件和動(dòng)作。
基本概念
State: 狀態(tài)
Event: 事件. 事件觸發(fā)狀態(tài)變換
Action: 動(dòng)作. event發(fā)生前或后執(zhí)行的動(dòng)作
transition: 變換. 狀態(tài)變換
github
https://github.com/pytransitions/transitions
安裝
pip install transitions
簡(jiǎn)單示例
# 連接協(xié)議狀態(tài)機(jī)
from transitions.extensions import HierarchicalMachine as Machine
from 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(tài)
self.states = ["STATE_NOT_CONNECTED",
{
"name": "STATE_CONNECTED",?? # 狀態(tài)名
"on_enter": self._on_enter_CONNECTED,? # 進(jìn)入狀態(tài)觸發(fā)
"on_exit": self._on_exit_CONNECTED,??? # 退出狀態(tài)觸發(fā)
"children": [???? # 狀態(tài)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
# 定義狀態(tài)變換
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
# 事件觸發(fā)的動(dòng)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(tài)機(jī)
# 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(tài)
machine.state
machine.is_()
定義狀態(tài)
# 狀態(tài)可以是三種類型: 對(duì)象、字符串、字典
from transitions import State
states = [
State(name="solid"),??? # 對(duì)象
"liquid",?????????????? # 字符串
{"name": "gas"}???????? # 字典
]
定義變換
# 定義函數(shù)
machine.add_transition(trigger, source, dest, )
trigger(str)???????? 方法名,觸發(fā)狀態(tài)轉(zhuǎn)換
source(str or list)? 源狀態(tài)
dest(str)??????????? 目標(biāo)狀態(tài)
# 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(tài)變?yōu)閍sleep
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原文鏈接：http://yongqing.is-programmer.com/posts/215592.html
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