import asyncio

def main1():
    print(1)

def main2():
    print(2)

def main3():
    print(3)

def main4():
    print(4)

async def do_main1(semaphore):
    async with semaphore:
        print('Start work #1')
        main1()
        # optionally do a lot of work that will consume memory
        await asyncio.sleep(1)
        print('End work #1')

async def do_main2(semaphore):
    async with semaphore:
        print('Start work #2')
        main2()
        # optionally do a lot of work that will consume memory
        await asyncio.sleep(1)
        print('End work #2')

async def do_main3(semaphore):
    async with semaphore:
        print('Start work #3')
        main3()
        # optionally do a lot of work that will consume memory
        await asyncio.sleep(1)
        print('End work #3')

async def do_main4(semaphore):
    async with semaphore:
        print('Start work #4')
        main4()
        # optionally do a lot of work that will consume memory
        await asyncio.sleep(1)
        print('End work #4')

async def main():
    tasks = []

    semaphore = asyncio.BoundedSemaphore(2)

    tasks.append(asyncio.ensure_future(do_main1(semaphore)))
    tasks.append(asyncio.ensure_future(do_main2(semaphore)))
    tasks.append(asyncio.ensure_future(do_main3(semaphore)))
    tasks.append(asyncio.ensure_future(do_main4(semaphore)))
    await asyncio.gather(*tasks)

if __name__ == "__main__":

    loop = asyncio.get_event_loop()
    #loop.set_debug(True)
    result = loop.run_until_complete(main())

    loop.close()

    if result:
            print(f"Задание {result}")
            sleep(2)