Using Timer Coroutine

A timer instance is created with atimer.Timer class. To delay execution, await the timer object. The result of the await expression is a number of timer expirations.

The example below creates timer object with 250 ms interval, arms the timer, and uses the timer six times in the loop (the purpose of the if statement is explained below).

import asyncio
import time

import atimer

async def start(timer: atimer.Timer) -> None:
    timer.start()

    for i in range(6):
        if i == 3:  # simulation of overrun
            time.sleep(1.1)

        num_exp = await timer

        now = time.time()
        print('{}: {:.3f}  {}'.format(i, now, num_exp))

timer = atimer.Timer(0.25)
try:
    asyncio.run(start(timer))
finally:
    timer.close()

The output of the example shows loop iteration counter, current system clock value, and number of expirations:

0: 1548799590.000  1
1: 1548799590.250  1
2: 1548799590.500  1
3: 1548799591.602  4
4: 1548799591.750  1
5: 1548799592.000  1

The following properties of the timer can be noticed

• the difference between each execution is 250ms; this is despite the the time needed for execution of all the statements within the loop

• almost all timer expirations are synchronized with system clock at the edge of the 250 ms interval

• one expiration (loop iteration 3) is affected by overrun due to the time.sleep statement; however, the timer corrects itself, and continues delayed execution at expected pace