如何避免将“全局”与 asyncio（电视节目）一起使用？

Question

As far as I know using "global" is a bad practice in python, but I have no idea how to avoid it here. Thank you in advance.

import asyncio
from telethon import TelegramClient, sync, events

api_id = ***
api_hash = '***'

client = TelegramClient('session_name', api_id, api_hash).start()

channel_id = ***

@client.on(events.NewMessage(chats=channel_id))
async def handler(event):
    text = event.raw_text.lower()

    global task

    if text == 'start':
        task = client.loop.create_task(main())
        await client.send_message(channel_id, 'task was started')

    if text == 'stop':
        task.cancel()
        await client.send_message(channel_id, 'task was canceled')

async def main():
    while True:
        await client.send_message(channel_id, 'do something')
        await asyncio.sleep(3)

client.run_until_disconnected()

Answer 1

Looking at the documentation, I couldn't find the recommended way to use the client with classes, but you should always be able to connect it yourself. For example:

class MyClient:
    def __init__(self, client):
        self.task = None
        self.client = client

    async def on_message(self, channel_id, event):
        text = event.raw_text.lower()

        if text == 'start':
            self.task = self.client.loop.create_task(self.main(channel_id))
            await self.client.send_message(channel_id, 'task was started')

        if text == 'stop':
            self.task.cancel()
            await self.client.send_message(channel_id, 'task was canceled')

    async def main(self, channel_id):
        while True:
            await self.client.send_message(channel_id, 'do something')
            await asyncio.sleep(3)

def run_client():
    # instantiate telegram client, my client, and connect the two
    api_id = ***
    api_hash = '***'

    channel_id = ***

    client = TelegramClient('session_name', api_id, api_hash).start()
    my_client = MyClient(client)

    @client.on(events.NewMessage(chats=channel_id))
    async def handle(event):
        await my_client.on_message(channel_id, event)

    client.run_until_disconnected()

run_client()

Answer 2

the TelegramClient's function:add_event_handler is what you're looking for

Answer 3

In general in Python, if you need a variable to be "static" (continue its lifetime beyond a single function call) like "task" in this example, you should consider going for an object-oriented approach, like @user4815162342 suggested. If you don't want classes and objects, you can also emulate a similar functionality using pre-set keyword arguments, although it's somewhat of an ugly hack. In your example, you would only have to change a single function like so:

@client.on(events.NewMessage(chats=channel_id))
async def handler(event, static_variables={}):
    text = event.raw_text.lower()

    if text == 'start':
        static_variables['task'] = client.loop.create_task(main())
        await client.send_message(channel_id, 'task was started')

    if text == 'stop':
        static_variables['task'].cancel()
        await client.send_message(channel_id, 'task was canceled')

The reason this works is that Python will only instantiate default arguments for keyword arguments on the first function call, and then re-use the instance (in this example, an initially empty dictionary) on all subsequent function calls.