Nature of Async

The nature of Async

The nature of Async is an Event Loop.

The result is a coroutine object after invoke a async function. The function can only be executed after becoming a task.

Basic 1

import asyncio
import time

async def say_after(delay, what):
  await asyncio.sleep(delay)
  return f"{what} - {delay}"

async def main():
  print(f"started at {time.strftime('%X')}")

  await say_after(1, "hello")
  await say_after(2, "world")

  print(f"finished at {time.strftime('%X')}")

asyncio.run(main())

Basic 2

import asyncio
import time

async def say_after(delay, what):
  await asyncio.sleep(delay)
  return f"{what} - {delay}"

async def main():
  print(f"started at {time.strftime('%X')}")

  task1 = asyncio.create_task(say_after(1, "hello"))
  task2 = asyncio.create_task(say_after(2, "world"))

  await task1
  await task2

  print(f"finished at {time.strftime('%X')}")

asyncio.run(main())

Basic 3

import asyncio
import time

async def say_after(delay, what):
  await asyncio.sleep(delay)
  return f"{what} - {delay}"

async def main():
  print(f"started at {time.strftime('%X')}")

  ret = await asyncio.gather(
    say_after(1, "hello"),
    say_after(2, "world")
  )

  print(f"finished at {time.strftime('%X')}")

Another way to run

loop = asyncio.get_event_loop()
res = loop.run_until_complete(xxx())
loop.close()