How to programme a task with a timer in my Python code?-CodePudding

I want to execute a task after certain time, so I have tried a countdown timer with a condition of being finished (when countdown variable = 0, the task is performed). The thing is that I don't want to stop the execution of the main program while performing the countdown. I have tried this:

import time

def countdown(num_of_secs):
    while(num_of_secs):
        time.sleep(1)
        num_of_secs -= 1
        return num_of_secs

So, I run my code setting a number of seconds to the countdown, and when this countdown reaches the 0 value, a task must be execute. Using this code (it uses a while), when I call my function "countdown" it stops the execution of the main program, so it is the same as a big time.sleep. I want to carry out this count in the background, without stopping other actions until the countdown finishes and the task starts. Thank you

CodePudding user response：

Usually python only has a single program flow, so every instruction needs to complete before the next one can get executed.

For your case you need asynchronicity, with e.g. asyncio.sleep(5) as a separate task in the same event loop.

import asyncio

async def sleeper():
    print('Holding...')
    await asyncio.sleep(5)
    print('Doing Work!')

async def work():
    print('Doing work')
    print('while')
    print('the other guy is sleeping')

async def main():
    await asyncio.gather(sleeper(), work())

asyncio.run(main())

CodePudding user response：

Another alternative is by using threading. I've got a simple example here with 2 Threads where the working thread is waiting for the countdown thread to finish and starting. The Main is still working fine.

import threading
import time


def do_something():
    countdown_thread.join()
    print("Starting Task")
    time.sleep(3)
    print("Finished Task")

def countdown(num_of_secs):
    while(num_of_secs):
        time.sleep(1)
        num_of_secs -= 1
        print(num_of_secs)


if __name__ == '__main__':
    countdown_thread = threading.Thread(target=countdown, args=(3,))
    work_thread = threading.Thread(target=do_something)

    countdown_thread.start()
    work_thread.start()

    while True:
        print("Main doing something")
        time.sleep(1)

Example picture for multithreading: Sequential vs Threading