asyncio，任务在哪里执行？

Question

I'm new to asyncio. Reading asyncio documentation , I don't understand where Tasks are run.

import asyncio

async def query_api(url):
    #http://a.b.c takes 3 seconds
    #http://x.y.z takes 5 seconds

async def main():
    task1 = asyncio.create_task(query_api('http://a.b.c'))
    task2 = asyncio.create_task(query_api('http://x.y.z'))
    
    await task1
    await task2
    print ('Tasks Done')

asyncio.run(main())

This doc says asyncio has an event loop running in a main thread.

• Do task1 and task2 run in the main thread? If so, they must not run in parallel because CPU can only do one thing at a time?
• Tasks Done appears after 8 seconds or sooner?

Answer 1

AsyncIO is a framework to run concurrent tasks. Please note that Concurrency does not mean parallelism here.

• Do task1 and task2 run in the main thread? If so, they must not run in parallel because CPU can only do one thing at a time?

Yes. They run in the same thread (by default) and it means that the they use the same CPU. But the trick is that we do not need to hold on to the CPU while we are doing network I/O.

Task2 can start using the CPU when Task1 is waiting on network to respond.

• Tasks Done appears after 8 seconds or sooner?

The tasks should finish before 8 seconds

There are ways to use multi-threading or multi-processing using asyncIO if you require your tasks to be run outside your main thread.