Running Python functions at Certain Times of the Day

Question

I've spent some significant time searching for something like this, but I think I'm not using the right search terms. Anyway, I have tasks that I want to do at certain times of the day, and these tasks are executable via a python-api.

Is there a module/method I can use to make sure these tasks run at the correct times, and ensures no tasks are skipped? If I wrote something myself it would look really ugly like:

import sys
import time

taskA = False
taskB = False
taskC = False

while True:
    now = time.strftime("%H:%M:%S")

    if taskA == False and now >= "10:00:00":
        <do TaskA>
        taskA = True
    if taskB == False and now >= "12:00:00":
        <do TaskB>
        taskB = True
    if taskC == False and now >= "16:20:07":
        <do TaskC>
        taskC = True
        sys.exit(0)

    time.sleep(1)

This is something that is currently on cron but I want to replace it with a python script.

Answer 1

IIUC: Here is one simple solution, You can use threading.Timer function from the threading package which starts a thread that executes a function after a specified interval has passed. You can use this:

from threading import Timer
from datetime import datetime, date
from time import sleep

def task_a():
    sleep(5) #--> perform some work
    print("Task A, completed at:", datetime.today().time())

def task_b():
    sleep(10) #--> perform some work
    print("Task B, completed at", datetime.today().time())

def task_c():
   sleep(20) #--> perform some work
   print("Task C, completed at", datetime.today().time())

now = datetime.today().time()

taska_start = datetime.strptime("10:00:00", "%H:%M:%S").time()
taskb_start = datetime.strptime("12:00:00", "%H:%M:%S").time()
taskc_start = datetime.strptime("16:20:07", "%H:%M:%S").time()

tasks = [(taska_start, task_a), (taskb_start, task_b), (taskc_start, task_c)]

for task_start, task in tasks:
    if datetime.combine(date.min, task_start) > datetime.combine(date.min, now):
        diff = datetime.combine(date.min, task_start) > datetime.combine(date.min, now)
        t = Timer(diff.seconds, task)
        t.start()

For Example,

If current time 12:00:00 and suppose task_a is scheduled to run at 13:00:00, task_b is scheduled to run at 13:30:00 and task_c is scheduled to run at 14:00:00.. Then after executing the script task_a will run after 60 seconds, task_b will run after 90, and task_c will run after 120 seconds from the current time.

Sample Result:

Task A, completed at: 13:00:05
Task B, completed at: 13:30:10
Task C, completed at: 14:00:20

Answer 2

You can use a CRON Job. Python Crontab allows you to do such a thing. You can check how to use it here: https://stackabuse.com/scheduling-jobs-with-python-crontab/