Check if asyncio.get_event_loop() has finished?-CodePudding

I have a custom background decorator. When I run a function in the background, how can I then check if all functions, that I started in the background, are done until I return?

#background decorator
def background(fn):
    def wrapped(*args, **kwargs):
        return asyncio.get_event_loop().run_in_executor(None, fn, *args, **kwargs)
    return wrapped

#myfunction that I run in the background
@background
def myfunction():
    #run some tasks

#main here I call "myfunction"
def main():
    for i in list:
        myfunction()
#check if all myfunction's are done then return (MY PROBLEM)

CodePudding user response：

You can make a list of myfunction() tasks, then run them with asyncio.wait()

import asyncio
from timeit import default_timer as timer

def background(fn):
    def wrapped(*args, **kwargs):
        return asyncio.get_event_loop().run_in_executor(None, fn, *args,**kwargs)
    return wrapped

@background
def myfunction(tasknum):
    print("tasknum",tasknum," -- started at", timer())
    #add lots of numbers to simulate some task...
    x = 0
    for n in range(20000000):
        x  = n
    print("tasknum",tasknum," -- finished at", timer())

def main():
    print("main -- started at", timer())
    background_loop = asyncio.get_event_loop()
    tasks = []

    for i in range(4):
        tasks.append(myfunction(i))

    try:
        background_loop.run_until_complete(asyncio.wait(tasks))
    finally:
        background_loop.close()

    print("main -- finished at", timer())

main()
print('returned from main')

output:

main -- started at 38203.24129425
tasknum 0  -- started at 38203.241935683
tasknum 1  -- started at 38203.24716722
tasknum 2  -- started at 38203.257414232
tasknum 3  -- started at 38203.257518981
tasknum 1  -- finished at 38206.503383425
tasknum 2  -- finished at 38206.930789807
tasknum 0  -- finished at 38207.636296604
tasknum 3  -- finished at 38207.833483453
main -- finished at 38207.833736195
returned from main

Note that get_event_loop() is depreciated in python 3.10, so the best solution is probably to start the background loop before the decorator definition, and then just use the loop name directly:

background_loop = asyncio.new_event_loop()

def background(fn):  
    def wrapped(*args, **kwargs):
        return background_loop.run_in_executor(None, fn, *args, **kwargs)
    return wrapped

CodePudding user response：

Outside your main function you should define your loop, and use this to wait all the functions that will run in your main until they're completed:

loop = asyncio.new_event_loop()
asyncio.set_event_loop(loop)
loop.run_until_complete(main())  # <- This is what you are looking for
loop.close()

Then, in your wrapped function use this loop like this:

await loop.run_in_executor(...)

And remember use async and await expressions where appropriate.