Python 中的异步和线程

Question

I want to use async in python like c# or javascript.For example I want my program not to block next codes or maybe buttons in app while sending a request.I wrote some code about that.However I dont know whether this usage is true or false.I can't understand asyncio

import asyncio
import threading
import time

async def waitForMe(name):
    for i in range(5):
        await asyncio.sleep(1)
        print(name)

async def main():
    task1 = asyncio.create_task(waitForMe("task1"))
    task2 = asyncio.create_task(waitForMe("task2"))
    task3 = asyncio.create_task(waitForMe("task3"))
    await task1
    await task2
    await task3

def mfunction():   
    asyncio.run(main())
t1=threading.Thread(target=mfunction)
t1.start()
for i in range(3):
    time.sleep(1)
    print("main")

Answer 1

I'd really recommend this excellent asyncio walkthrough, which should answer most of your questions.

A quote from the mentioned article in the light of your code:

[...] async IO is a single-threaded, single-process design: it uses cooperative multitasking, a term that [...] gives a feeling of concurrency despite using a single thread in a single process.

If you don't want your program to block while processing (IO) requests (as stated in your question), concurrency is sufficient (and you don't need (multi)threading)!

Concurrency [...] suggests that multiple tasks have the ability to run in an overlapping manner.

I'll repeat the exact example from the mentioned article, which has a similar structure as your example:

#!/usr/bin/env python3
# countasync.py

import asyncio

async def count():
    print("One")
    await asyncio.sleep(1)
    print("Two")

async def main():
    await asyncio.gather(count(), count(), count())

if __name__ == "__main__":
    import time
    s = time.perf_counter()
    asyncio.run(main())
    elapsed = time.perf_counter() - s
    print(f"{__file__} executed in {elapsed:0.2f} seconds.")

This runs as follows:

$ python3 countasync.py
One
One
One
Two
Two
Two
countasync.py executed in 1.01 seconds.

Note that this examples uses asyncio.gather to kick-off the three count() processes in a non-blocking manner. Putting three await count() statements after one another won't work.

As far as I can see, this is exactly what you are looking for. As demonstrated, you don't need threading to achieve this.