python - 使用事件系统时如何正确杀死/退出/停止线程？

Question

我正在通过python创建一个gui工具。这里有一个问题，当我通过点击一个按钮触发一个子线程运行一些逻辑代码时。处理时间可能很长，并且在这个过程中可能会发生一些错误。如果发生错误我会发送一个错误事件来通知EventManager 并调用一些函数来杀死/退出子线程，因为继续运行左侧逻辑代码是没有意义的。但我不知道如何使用错误事件正确杀死/退出/停止子线程。有人可以帮我吗？

from queue import Queue, Empty
from threading import *
from tkinter import *
import time
from tkinter import ttk

EVENT_TYPE_1 = "Count"
EVENT_TYPE_2 = "Error"
MAX_NUMBER = 10
CUR_NUMBER = 0


class event_manager:
    def __init__(self):
        self._eventQueue = Queue()
        self._thread = Thread(target=self.Run, daemon=True)
        self._handlers = {}
        self._active = False

    def Start(self):
        self._active = True
        self._thread.start()

    def Run(self):
        while self._active is True:
            try:
                event = self._eventQueue.get(block=True, timeout=1)
                self.Process(event)
            except Empty:
                pass

    def Process(self, event):
        if event.type in self._handlers:
            for handler in self._handlers[event.type]:
                handler()
        else:
            pass

    def Stop(self):
        self._active = False
        self._thread.join()

    def addEventListenter(self, type_, handler):
        try:
            handlerList = self._handlers[type_]

        except KeyError:
            handlerList = []
            self._handlers[type_] = handlerList

        if handler not in handlerList:
            handlerList.append(handler)

    def removeEventListenter(self, type_, handler):
        try:
            handlerList = self._handlers[type_]
            if handler in handlerList:
                handlerList.remove(handler)
            if not handlerList:
                del self._handlers[type_]
        except KeyError:
            pass

    def sendEvent(self, event):
        self._eventQueue.put(event)


class Event:
    def __init__(self, event_event_name, cur_done_task, type_=None):
        self.type = type_
        self._event_name = event_event_name
        self._curDoneTask = cur_done_task


class EventSource:
    def __init__(self, event_name, event_mgr, max_number, type):
        self._event_name = event_name
        self._event_manager = event_mgr
        self._type = type
        self._max_number = max_number

    def count(self):
        global CUR_NUMBER
        for i in range(self._max_number):
            CUR_NUMBER = i + 1

            if CUR_NUMBER == 4:  # assume this is a error check function,if error occurs,it will send a error event,and hopefully this event can terminate the sub-thread which is exactly running current code 
                print("************ detect error occurred , this thread should be terminated immediately !")
                errorEvent = Event("error", CUR_NUMBER, type_=EVENT_TYPE_2)
                self._event_manager.sendEvent(errorEvent)

            print(
                "************ main thread start：now start process {} - count : {}".format(self._event_name, CUR_NUMBER))
            event = Event("test", CUR_NUMBER, type_=self._type)
            self._event_manager.sendEvent(event)
            time.sleep(1)


class GUIListener(Tk):
    def __init__(self):
        super(GUIListener, self).__init__()

        self.title("Progress GUI")
        self.geometry("1200x805+600+100")
        self.config(bg="#535353")
        self.resizable(True, True)
        self.taskThread = None

        self.progressBar = ttk.Progressbar(master=self, orient=HORIZONTAL, maximum=MAX_NUMBER, length=300)
        self.progressBar.pack()
        self.button = ttk.Button(self, text="Run", command=lambda: self.button_function(MAX_NUMBER))
        self.button.pack()

    def update_progress_value(self):
        print("************Sub thread start: detect progress bar value is now...{}".format(self.progressBar['value']))
        self.progressBar['value'] = CUR_NUMBER
        self.progressBar.update_idletasks()
        print("************Sub thread start: update progress bar value to...{}".format(CUR_NUMBER))

    def button_function(self, max_number):
        # though I can make some error check function before task thread starts,but I really want to discuss the way that using event-system here 
        es = EventSource("eventSource", eventMgr, max_number, EVENT_TYPE_1)
        self.taskThread = Thread(target=es.count, daemon=True).start()  # here to start the sub-thread which need to be terminated by error event

    def terminate_error_thread(self):  # this method will be called when GUIListener recieved error event and terminate the sub-thread immediately
        pass
        # TODO: but how to implement this method？


if __name__ == '__main__':
    gui = GUIListener()

    eventMgr = event_manager()
    eventMgr.addEventListenter(EVENT_TYPE_1, gui.update_progress_value)
    eventMgr.addEventListenter(EVENT_TYPE_2, gui.terminate_error_thread)

    eventMgr.Start()

    gui.mainloop()

希望控制台会给我以下日志：

************ main thread start：now start process eventSource - count : 1
************Sub thread start: detect progress bar value is now...0.0
************Sub thread start: update progress bar value to...1
************ main thread start：now start process eventSource - count : 2
************Sub thread start: detect progress bar value is now...1
************Sub thread start: update progress bar value to...2
************ main thread start：now start process eventSource - count : 3
************Sub thread start: detect progress bar value is now...2
************Sub thread start: update progress bar value to...3
************ detect error occurred , this thread should be terminated immediately !

标签： pythonmultithreadingpython-multithreading

Answer 1

In the count function, you could simply break out of the loop when you want to exit. If the function finishes running, the thread will exit automatically.

For example,

class EventSource:
    def __init__(self, event_name, event_mgr, max_number, type):
        self._event_name = event_name
        self._event_manager = event_mgr
        self._type = type
        self._max_number = max_number

    def count(self):
        global CUR_NUMBER
        for i in range(self._max_number):
            CUR_NUMBER = i + 1

            if CUR_NUMBER == 4:  # assume this is a error check function,if error occurs,it will send a error event,and hopefully this event can terminate the sub-thread which is exactly running current code 
                print("************ detect error occurred , this thread should be terminated immediately !")
                errorEvent = Event("error", CUR_NUMBER, type_=EVENT_TYPE_2)
                # self._event_manager.sendEvent(errorEvent)
                break

            print("************ main thread start：now start process {} - count : {}".format(self._event_name, CUR_NUMBER))
            event = Event("test", CUR_NUMBER, type_=self._type)
            self._event_manager.sendEvent(event)
            time.sleep(1)