如何终止 Python 中的线程？

Question

我知道这个话题已经讨论过几次，但是我已经尝试过，或者至少尝试了几乎所有的解决方案，但是作为一个相当新的 python basher，我无法让以前的任何解决方案起作用。

该脚本的基本前提是它订阅了一个 MQTT 代理并等待命令，单个动作命令 100% 工作，但是其中一个命令需要一个循环无限期地运行，直到收到另一个命令，因此最合适的解决方案是在一个单独的线程中运行“循环”，而主订阅者循环继续“监听”下一个命令。

一切都在工作 95%，“静态”命令通过并且任务运行良好，然后当“mtg”命令通过它时，线程和循环运行 100%，但是这是它失败的地方，当收到下一个命令我可以确认“if”语句在将消息打印到控制台时处理命令，但是 thread.stop() 没有运行，或者它可能运行但它不会终止线程 ---我正在拔头发试图弄清楚。

一些代码：

from sys import exit
import blinkt
import threading
import time

MQTT_SERVER = '192.168.x.x'
MQTT_PORT = 1883
MQTT_TOPIC = 'mytopic'

REDS = [0, 0, 0, 0, 0, 16, 64, 255, 64, 16, 0, 0, 0, 0, 0, 0]

start_time = time.time()

class task(threading.Thread):

     def __init__(self):
         threading.Thread.__init__(self)
         self.kill = threading.Event()
         self.event = threading.Event()
         self._stop = threading.Event()

     def run(self):
#        while not self.kill.is_set(): 
         while True:
             if self.stopped():
                return
             self.start_run()

     def stop(self):
#        self.event.set()
         self._stop.set()

     def stopped(self):
         return self._stop.isSet()

     def start_run(self):
#         while True: <-- no longer needed as the run method loops the process. 
             delta = (time.time() - start_time) * 16
             offset = int(abs((delta % len(REDS)) - blinkt.NUM_PIXELS))

             for i in range(blinkt.NUM_PIXELS):
                 blinkt.set_pixel(i, REDS[offset + i], 0, 0)

             blinkt.show()
             time.sleep(0.1)

def on_connect(client, userdata, flags, rc):
    print('Connected with result code ' + str(rc))
    client.subscribe(MQTT_TOPIC)

def on_message(client, userdata, msg):

    data = msg.payload
    if type(data) is bytes:
        data = data.decode('utf-8')
    data = data.split(',')
    command = data.pop(0)

    if command == 'clr' and len(data) == 0:
        blinkt.clear()
        blinkt.show()
        t1.stop()      #<--- I've tried a few ways to get the task to stop when the "clr" command is recieved
        task.stop()
        return

    if command == 'rgb' and len(data) == 4: #<-- This code block works fine, msg arrives and LEDs are set correctly
        try:
            pixel = data.pop(0)

            if pixel == '*':
                pixel = None
            else:
                pixel = int(pixel)
                if pixel > 7:
                    print('Pixel out of range: ' + str(pixel))
                    return

            r, g, b = [int(x) & 0xff for x in data]

            print(command, pixel, r, g, b)

        except ValueError:
            print('Malformed command: ' + str(msg.payload))
            return
        if pixel is None:
            for x in range(blinkt.NUM_PIXELS):
                blinkt.set_pixel(x, r, g, b)
        else:
            blinkt.set_pixel(pixel, r, g, b)
        blinkt.show()
        return


    if command == 'mtg' and len(data) == 0:
        print(command)
        t1 = task()
        t1.start()   #<-- Here is where the Thread is called to start and seems to run ok
        return

blinkt.set_clear_on_exit()

client = mqtt.Client()
client.on_connect = on_connect
client.on_message = on_message
client.connect(MQTT_SERVER, MQTT_PORT, 60)
client.loop_forever()

Answer 1

您的t1变量是本地变量，因此当您退出on_message function 时它会丢失。 此外，您将 class task和实例t1 （ task.stop()不起作用）混为一谈。

为了快速修复，将t1 = None声明为全局，然后将global t1添加到您的on_message function...

但是，我会考虑重构一些东西，以便有一个始终运行的线程来命令 Blinkt。 并且 MQTT 消息处理程序只需相应地设置其 state - 显然是这样的，干编码。 所以可能会有一些愚蠢。

from sys import exit
import blinkt
import threading
import time

MQTT_SERVER = "192.168.x.x"
MQTT_PORT = 1883
MQTT_TOPIC = "mytopic"

REDS = [0, 0, 0, 0, 0, 16, 64, 255, 64, 16, 0, 0, 0, 0, 0, 0]

start_time = time.time()


class BlinktManager(threading.Thread):
    def __init__(self):
        threading.Thread.__init__(self)
        self.stop_event = threading.Event()
        self.mode = None

    def run(self):
        while not self.stop_event.isSet():
            self.tick()
            self.stop_event.wait(0.1)  # instead of sleep

    def tick(self):
        if self.mode == "reds":
            self._tick_reds()

    def _tick_reds(self):
        delta = (time.time() - start_time) * 16
        offset = int(
            abs((delta % len(REDS)) - blinkt.NUM_PIXELS)
        )

        for i in range(blinkt.NUM_PIXELS):
            blinkt.set_pixel(i, REDS[offset + i], 0, 0)

        blinkt.show()

    def clear(self):
        self.mode = None
        blinkt.clear()
        blinkt.show()

    def set_all_pixels(self, r, g, b):
        self.mode = None
        for x in range(blinkt.NUM_PIXELS):
            blinkt.set_pixel(x, r, g, b)
        blinkt.show()

    def set_pixel(self, x, r, g, b):
        self.mode = None
        blinkt.set_pixel(x, r, g, b)
        blinkt.show()

    def begin_reds(self):
        self.mode = "reds"


def on_connect(client, userdata, flags, rc):
    print("Connected with result code " + str(rc))
    client.subscribe(MQTT_TOPIC)


def on_message(client, userdata, msg):
    data = msg.payload
    if type(data) is bytes:
        data = data.decode("utf-8")
    data = data.split(",")
    command = data.pop(0)

    if command == "clr" and len(data) == 0:
        blinkt_manager.clear()

    if command == "rgb" and len(data) == 4:
        x = data[0]
        r, g, b = [int(x) & 0xFF for x in data[1:]]
        if x == "*":
            blinkt_manager.set_all_pixels(r, g, b)
        else:
            # TODO: error handling
            blinkt_manager.set_pixel(int(x), r, g, b)

    if command == "mtg" and len(data) == 0:
        blinkt_manager.begin_reds()


blinkt.set_clear_on_exit()

blinkt_manager = BlinktManager()
blinkt_manager.start()

client = mqtt.Client()
client.on_connect = on_connect
client.on_message = on_message
client.connect(MQTT_SERVER, MQTT_PORT, 60)
client.loop_forever()

Answer 2

Python 程序在 python 线程中引发异常

import threading 
import ctypes 
import time 

class thread_with_exception(threading.Thread):

    def __init__(self, name): 
    threading.Thread.__init__(self) 
    self.name = name 

def run(self): 

    # target function of the thread class 
    try: 
        while True: 
            print('running ' + self.name) 
    finally: 
        print('ended') 

def get_id(self): 

    # returns id of the respective thread 
    if hasattr(self, '_thread_id'): 
        return self._thread_id 
    for id, thread in threading._active.items(): 
        if thread is self: 
            return id

def raise_exception(self): 
    thread_id = self.get_id() 
    res = ctypes.pythonapi.PyThreadState_SetAsyncExc(thread_id, 
          ctypes.py_object(SystemExit)) 
    if res > 1: 
        ctypes.pythonapi.PyThreadState_SetAsyncExc(thread_id, 0) 
        print('Exception raise failure') 

t1 = thread_with_exception('Thread 1') 
t1.start() 
time.sleep(2) 
t1.raise_exception() 
t1.join()