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 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

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 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.state

machine.is_()

定義狀態

# 狀態可以是三種類型: 對象、字符串、字典

from transitions import State

states = [

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

以上就是python 實用工具狀態機transitions的詳細內容，更多關于python transitions的資料請關注云海天教程其它相關文章！

原文鏈接：http://yongqing.is-programmer.com/posts/215592.html

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