Python：使用键盘按键启动和停止线程

Question

I'm working on Python 3.8 and I'm trying to be able to toggle a thread on and off using a keyboard shortcut.

This is my Thread class:

import keyboard
from threading import Thread
import time

class PrintHi(Thread):
    def __init__(self):
        Thread.__init__(self)
        self.active = False

    def run(self):
        while True:
            if self.active:
                print("Hi,", time.time())
                time.sleep(1)

It seems to work as intended I can start the thread and later change 'thread.active' to True or False depending on if I want to enable it or disable.

The problem is when I try to use it with the "keyboard" module it doesnt work as expected:

class KeyboardHook(object):
    def __init__(self):
        self.thread = PrintHi()
        self.thread.start()
        self.set_keyboard_hotkeys()

    def toggle_print(self):
        print("Toggle Print")
        self.thread.active = not self.thread.active

    def set_keyboard_hotkeys(self):
        print("Setting hotkeys hooks")
        keyboard.add_hotkey('ctrl+c', self.toggle_print)
        keyboard.wait()


if __name__ == '__main__':
    hook = KeyboardHook()

These are the steps:

• I first create the thread, store it in 'self.thread' and start it.
• Then I set the keyboard hotkeys hooks
• When I press 'ctrl+c' the 'toggle_print()' function should execute
• This should set the active property of the thread to True thus enabling the printing.

The thread by itself works fine, and the keyboard hook by itself also works fine but when I combine both they don't work.

Does anyone have an idea of what I'm doing wrong? Is there a approach of toggling threads on and off by using keyboard shortcuts? In my application, I will have multiple threads that I will have to toggle on and off independently.

Thanks!

Answer 1

I'd suggest to refactor your code a bit, namely to use Event in the printer thread instead of a bool variable to signal a print action, and to add logic which will allow you to stop the printer thread on program exit:

import time
from threading import Thread, Event

import keyboard


class PrintThread(Thread):
    
    def __init__(self): 
        super().__init__() 
        self.stop = False 
        self.print = Event()

    def run(self): 
        while not self.stop: 
            if self.print.wait(1): 
                print('Hi,', time.time())
    
    def join(self, timeout=None): 
        self.stop = True 
        super().join(timeout)

Also, I'd suggest to move the blocking code out from the KeyboadHook initializer to a separate start method:

class KeyboardHook: 

    def __init__(self):
        self.printer = PrintThread()
        self.set_keyboard_hotkeys()

    def toggle_print(self): 
        print('Toggle the printer thread...')

        if self.printer.print.is_set():
            self.printer.print.clear()
        else:
            self.printer.print.set()

    def set_keyboard_hotkeys(self):
        print('Setting keyboard hotkeys...')
        keyboard.add_hotkey('ctrl+p', self.toggle_print)

    def start(self): 
        self.printer.start()

        try:
            keyboard.wait()
        except KeyboardInterrupt:
            pass
        finally:
            self.printer.join()

Run it like this:

hook = KeyboardHook()
hook.start()

This code works for me like a charm.

Answer 2

Some changes in KeyboardHook get it running:

1. You do not need to keyboard.wait()
2. Start the thread after setting up hotkeys
3. Better change hot-key from ctrl-c to something else

class KeyboardHook(object):
    def __init__(self):
        self.thread = PrintHi()
        self.set_keyboard_hotkeys()
        self.thread.start()

    def toggle_print(self):
        print("Toggle Print")
        self.thread.active = not self.thread.active

    def set_keyboard_hotkeys(self):
        print("Setting hotkeys hooks")
        keyboard.add_hotkey('ctrl+p', self.toggle_print)
        #keyboard.wait()