Executing periodic actions in Python [duplicate]

Answer 1

Here's a simple single threaded sleep based version that drifts, but tries to auto-correct when it detects drift.

NOTE: This will only work if the following 3 reasonable assumptions are met:

1. The time period is much larger than the execution time of the function being executed
2. The function being executed takes approximately the same amount of time on each call
3. The amount of drift between calls is less than a second

-

from datetime import timedelta
from datetime import datetime

def exec_every_n_seconds(n,f):
    first_called=datetime.now()
    f()
    num_calls=1
    drift=timedelta()
    time_period=timedelta(seconds=n)
    while 1:
        time.sleep(n-drift.microseconds/1000000.0)
        current_time = datetime.now()
        f()
        num_calls += 1
        difference = current_time - first_called
        drift = difference - time_period* num_calls
        print "drift=",drift