各位高人，最近學習python的asyncio時碰到點問題。以下的code是按照這邊的官方教學改的
https://docs.python.org/3/library/asyncio-task.html#coroutines

原本

import asyncio
import time

async def say_after(delay, what):
    await asyncio.sleep(delay)
    print(what)

async def main():
    task1 = asyncio.create_task(
        say_after(1, 'hello'))

    task2 = asyncio.create_task(
        say_after(2, 'world'))

    # Wait until both tasks are completed (should take around 2 seconds.)
    await task1
    await task2

asyncio.run(main())

這個執行後會print

hello
world

這個沒有問題，但本人做了以下小修改

import asyncio
import time

async def say_after(delay, what):
    await asyncio.sleep(delay)
    print(what)

async def main():
    task1 = asyncio.create_task(
        say_after(1, 'hello'))

    task2 = asyncio.create_task(
        say_after(2, 'world'))

    # Wait until both tasks are completed (should take around 2 seconds.)
    await task1
    print("HERE!")
    await task2

asyncio.run(main())

這個不知為何會print

hello
world
HERE!

而不是我所想的

hello
HERE!
world

還有，我嘗試註解掉await task2

import asyncio
import time

async def say_after(delay, what):
    await asyncio.sleep(delay)
    print(what)

async def main():
    task1 = asyncio.create_task(
        say_after(1, 'hello'))

    task2 = asyncio.create_task(
        say_after(2, 'world'))

    # Wait until both tasks are completed (should take around 2 seconds.)
    await task1
    # await task2

asyncio.run(main())

卻依然得到

hello
world

為什麼world還是會顯示？

謝謝各位看完