Telethon使用asyncio，但是schedule在设计时并没有考虑到asyncio，你应该考虑使用基于asyncio的schedule替代品，或者仅仅使用Python在asyncio模块中的内置函数来“调度”事情：

import asyncio
from telethon import TelegramClient

def send_image():
    ...
    client = TelegramClient(phone, apiId, apiHash)

    await client.start()
    await client.send_file(toChat, "./image.jpg", caption="Write text here")
    await client.disconnect()

async def main():
    while True:  # forever
        await send_image()  # send image, then
        await asyncio.sleep(10)  # sleep 10 seconds

    # this is essentially "every 10 seconds call send_image"

if __name__ == "__main__":
    asyncio.run(main())

您还应该考虑在main中创建和start()客户机，以避免每次都重新创建它。

这意味着您给予时间完成操作，请尝试以下更改：

from telethon import TelegramClient
import schedule

async def sendImage(): # <- make it async
    apiId = 1111111
    apiHash = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
    phone = "+111111111111"
    client = TelegramClient(phone, apiId, apiHash)

    toChat = 1641242898

    client.start()

    print("Sending...")
    await client.send_file(toChat, "./image.jpg", caption="Write text here") # <- here too add await

    client.disconnect()
    return

def main():
    schedule.every(10).seconds.do(client.loop.run_until_complete(sendImage))

    while True:
        schedule.run_pending()

if __name__ == "__main__":
    main()

另外我不认为你应该保持连接和断开，在我看来，客户端。开始（）应该在这个函数和客户端。断开了

正如输出所说，你需要等待协程的响应，代码可能会触发异常，而这些异常应该被处理。

try:
    client = TelegramClient(...)
    client.start()
except Exception as e:
    print(f"Exception while starting the client - {e}")
else:
    try:
        ret_value = await client.send_file(...)
    except Exception as e:
        print(f"Exception while sending the message - {e}")
    else:
        print(f"Message sent. Return Value {ret_value}")