如何在异步任务完成时退出

Question

在这个简短和简化的代码中，我想等待所有任务完成（queue.join）然后离开。此代码打开网络连接并下载一些数据。不幸的是我必须推 'ctrl-c' 因为 'client.run_until_disconnected()'.

完整代码有效，但我不知道如何在不中断键盘的情况下退出。我必须用 crontab 安排它，所以我不能使用 'client.run_until_disconnected()'

编辑：更新代码

#!/usr/bin/env python3.7

import asyncio
import telethon
from telethon import TelegramClient
from telethon import functions, types
from datetime import datetime

api_id = 00000 # your api_id
api_hash = "your api hash"

async def worker(queue):
    while True:
        queue_book = await queue.get()
        book_name = queue_book.file.name
        print(book_name)
        loop = asyncio.get_event_loop()
        await client.download_media(queue_book,book_name)
        queue.task_done()

async def main():
    #Free ebook medical articles
    channel = await client(functions.messages.CheckChatInviteRequest('your channel hash'))
    #values message's id depend on the chosen channel
    ids = [63529,63528,63527,63526,63525,63524,63523,63522]
    queue = asyncio.Queue(1)
    workers = [asyncio.create_task(worker(queue)) for _ in range(5)]
    for booksId in ids:
        async for get_book in client.iter_messages(channel.chat, ids=booksId):
            await queue.put(get_book) 
    await queue.join()
    for the_worker in workers:
        the_worker.cancel()

async def wait_until(dt):
      now = datetime.now()
      await asyncio.sleep((dt - now).total_seconds())

async def run_at(dt, coro):
      await wait_until(dt)
      return await coro

client = TelegramClient("Test", api_id, api_hash)
loop = asyncio.get_event_loop()
client.start()

try:
    loop = loop.create_task(run_at(datetime(2021, 2, 19, 11,00),main()))    

    client.run_until_disconnected()
except KeyboardInterrupt as keyint:
    print("KeyboardInterrupt..")
    pass

Answer 1

run_until_disconnected() 只是一个辅助函数，如果您想控制事件循环何时结束，则没有义务运行它。最小的变化是将 client.run_until_disconnected() 替换为 loop.run_forever()，并在 main() 结束时调用 loop.stop()。

更惯用的方法是保持 main() 不变，而不是从 create_task 开始，await 从顶部开始-级别协程（通常按照惯例称为 main，但您已经为其他函数选择了该名称）。然后就可以直接调用asyncio.run(actual_main())，当main结束时程序会自动退出。例如（未经测试）：

# main and other functions as in the question

async def actual_main():
    global client
    client = TelegramClient("Test", api_id, api_hash)
    await client.start()
    await run_at(datetime(2021, 2, 19, 11, 00), main())

asyncio.run(actual_main())

如何在异步任务完成时退出

How to exit when task is finished in asyncio

python

task

wait

python-asyncio

telethon