如何在 Python 中使用 asyncio 和线程

Question

I am trying to use asyncio together with threading for a Discord Bot. I've found this script which I changed to my needs:

import time
import threading as th
import asyncio
import discord

class discordvars(object):
    client=discord.Client()
    TOKEN=('---')
    running_discordthread=False

    discordloop = asyncio.get_event_loop()
    discordloop.create_task(client.start(TOKEN))
    discordthread=th.Thread(target=discordloop.run_forever)

def start():
    if discordvars.running_discordthread==False:
        discordvars.discordthread.start()
        print("Discord-Client started...")
        discordvars.running_discordthread=True
    else:
        print("Discord-CLient allready running...")
    time.sleep(2)
    
def stop():
    if discordvars.running_discordthread==True:
        discordvars.discordloop.call_soon_threadsafe(discordvars.discordloop.stop())
        print("Requestet Discord-Client stop!")
        discordvars.discordthread.join()
        print(discordvars.discordthread.isAlive())
        time.sleep(1)
        print("Discord-Client stopped...")
        discordvars.running_discordthread=False
    else:
        print("Discord-Client not running...")
    time.sleep(2)


@discordvars.client.event
async def on_message(message):
    if message.content.startswith('!test'):
        embed = discord.Embed(title="test", color=0x0071ce, description="test")
        await message.channel.send(embed=embed)

Starting the Script with the start() function works great. Also stopping with the stop() function works somehow. If I call the stop() function it prints: "False" so I am thinking that the thread was stopped. But if I then call the start() function I will get an error:

RuntimeError: threads can only be started once

This script is part of a big project so I am calling the functions from another script. But I think that shouldn't be the problem.

What is the problem? Thanks in advance.

Answer 1

You cannot re-start the existing thread, but you can start a new thread that runs the event loop. You can achieve that by moving the assignment to discordthread to the start function.

And your call to call_soon_threadsafe is wrong. You need to pass discordloop.stop to it, without parentheses. That refers to the actual function without calling it right away, and allows the loop thread to call it, which was intended:

discordloop.call_soon_threadsafe(discordloop.stop)

Finally, your init function is missing a global declaration for the variables you assign that are intended as globals.