CODEWITHSUNDEEP
pythonasynchronouspython-asynciopython-3.8
kuso.sama
kuso.sama

Reputation: 336

python Make an async timer without waiting to finish

I want to make a timer which is started in a normal function, but in the timer function, it should be able to call an async function

I want to do something like this:

startTimer()
while True:
   print("e")

def startTimer(waitForSeconds: int):
   # Wait for `waitForSeconds`
   await myAsyncFunc()

async def myAsyncFunc():
  print("in my async func")

Where the while True loop should do its stuff and after waitForSeconds the timer the async function should execute an other async function, but waiting shouldn't block any other actions and doesn't need to be awaited

If something isn't understandable, I'm sorry, I'll try to explain it then

Thanks

Upvotes: 1

Views: 2775

Answers (2)

user4815162342
user4815162342

Reputation: 155406

If you want to run your synchronous and asynchronous code in parallel, you will need to run one of them in a separate thread. For example:

def sync_code():
    while True:
        print("e")

async def start_timer(secs):
    await asyncio.sleep(secs)
    await async_func()

async def main():
    asyncio.create_task(start_timer(1))
    loop = asyncio.get_event_loop()
    # use run_in_executor to run sync code in a separate thread
    # while this thread runs the event loop
    await loop.run_in_executor(None, sync_code)

asyncio.run(main())

If the above is not acceptable for you (e.g. because it turns the whole program into an asyncio program), you can also run the event loop in a background thread, and submit tasks to it using asyncio.run_coroutine_threadsafe. That approach would allow startTimer to have the signature (and interface) like you wanted it:

def startTimer(waitForSeconds):
    loop = asyncio.new_event_loop()
    threading.Thread(daemon=True, target=loop.run_forever).start()
    async def sleep_and_run():
        await asyncio.sleep(waitForSeconds)
        await myAsyncFunc()
    asyncio.run_coroutine_threadsafe(sleep_and_run(), loop)

async def myAsyncFunc():
    print("in my async func")

startTimer(1)
while True:
    print("e")

Upvotes: 2

404pio
404pio

Reputation: 1030

I'm pretty sure that you are familiar with concurent processing, but you didn't show exactly what you want. So if I understand you correctly you want to have 2 processes. First is doing only while True, and the second process is the timer(waits e.g. 5s) and it will call async task. I assume that you are using asyncio according to tags:

import asyncio

async def myAsyncFunc():
    print("in my async func")

async def call_after(delay):
    await asyncio.sleep(delay)
    await myAsyncFunc()

async def while_true():
    while True:
        await asyncio.sleep(1) # sleep here to avoid to large output
        print("e")

async def main():
    task1 = asyncio.create_task(
        while_true())

    task2 = asyncio.create_task(
        call_after(5))

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

asyncio.run(main())

Upvotes: 0

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