如何在python中完成任务后停止线程？

Question

在下面的代码中，当我第一次单击按钮后，微调器 (MDSpinner) 将开始旋转，logging.info() 将被定向到 MDLabel。但是在我第二次点击按钮后，会有两份logging.info() 指向MDLabel。任务my_thread 完成后如何停止线程？提前致谢。

import kivy
from kivy.lang import Builder
import logging
import threading
from kivy.uix.floatlayout import FloatLayout
from kivymd.app import MDApp
from kivy.clock import Clock

import time

root_kv = '''
BoxLayout:
    id: main
    orientation: "vertical"
    spacing: "20dp"
    padding: "50dp", "10dp", "50dp", "10dp"

    MDRaisedButton:
        id: button4read_mtx
        size_hint: None, None
        size: 4 * dp(48), dp(48)
        text: "Start"
        opposite_colors: True
        pos_hint: {"center_x": 0.5, "center_y": 0.5}
        on_release: app.analyze_data()
    MDSpinner:
        id: spinder4button
        size_hint: None, None
        size: dp(46), dp(46)
        pos_hint: {'center_x': .5, 'center_y': .5}
        active: False
    MDLabel:
        id: test_label_log
        text: "Log"
        halign: "left"
'''

exit_flag = 0
def my_thread(log, app):
    app.root.ids.spinder4button.active = True
    for i in range(5):
        time.sleep(1)
        log.info("Step %s", i)
    app.root.ids.spinder4button.active = False

class MDLabelHandler(logging.Handler):

    def __init__(self, label, level=logging.NOTSET):
        logging.Handler.__init__(self, level=level)
        self.label = label

    def emit(self, record):
        "using the Clock module for thread safety with kivy's main loop"
        def f(dt=None):
            self.label.text += "\n" + self.format(record)  #"use += to append..."
        Clock.schedule_once(f)


class MyApp(MDApp):
    def __init__(self, **kwargs):
        super().__init__(**kwargs)

    def build(self):
        root = Builder.load_string(root_kv)
        return root
    def analyze_data(self):
        log = logging.getLogger("my.logger")
        log.level = logging.DEBUG
        log.addHandler(MDLabelHandler(self.root.ids.test_label_log, logging.DEBUG))
        #thread_info = _thread.start_new(my_thread, (log, self, ))
        #print(thread_info)
        x = threading.Thread(target=my_thread, args=(log, self, ))
        x.start()

if __name__ == '__main__':
    MyApp().run()

Answer 1

当任务完成时，线程应该终止。那不是问题。问题是每次运行analyze_data() 时都会添加一个新的日志记录处理程序。解决方法是只添加一个处理程序：

class MyApp(MDApp):
    def __init__(self, **kwargs):
        super().__init__(**kwargs)
        self.log = None

    def build(self):
        root = Builder.load_string(root_kv)
        return root

    def analyze_data(self):
        if self.log is None:
            self.log = logging.getLogger("my.logger")
            self.log.level = logging.DEBUG
            self.log.addHandler(MDLabelHandler(self.root.ids.test_label_log, logging.DEBUG))
        #thread_info = _thread.start_new(my_thread, (log, self, ))
        #print(thread_info)
        x = threading.Thread(target=my_thread, args=(self.log, self, ))
        x.start()