python 實用工具狀態(tài)機transitions

更新時間：2020年11月21日 17:21:17 作者：妙音

這篇文章主要介紹了python 實用工具狀態(tài)機transitions的使用，幫助大家更好的理解和學(xué)習(xí)python，感興趣的朋友可以了解下

說明

1. 狀態(tài)機是一個非常實用的理論。在涉及到復(fù)雜的場景，建立狀態(tài)機模型，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。使用時關(guān)鍵在于定義好事件和動作。

基本概念

State: 狀態(tài)
Event: 事件. 事件觸發(fā)狀態(tài)變換
Action: 動作. event發(fā)生前或后執(zhí)行的動作
transition: 變換. 狀態(tài)變換

github

https://github.com/pytransitions/transitions

安裝

pip install transitions

簡單示例

# 連接協(xié)議狀態(tài)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(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

# 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_<state_name>()

定義狀態(tài)

# 狀態(tài)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(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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