How to make simple alarms on Python

Question

I'm trying to make a simple alarm using Python but whatever I try it doesn't seem to work. I've just recently made a timer but an alarm would be a little more useful. I'm also pretty new to Python so I'm not really aware of all the rules and syntax.

import datetime
import os
stop = False
while stop == False:
    rn = str(datetime.datetime.now().time())
    print(rn)
    if rn == "18:00:00.000000":
        stop = True
        os.system("start BTS_House_Of_Cards.mp3")

When I run the file, it prints the time but goes completely past the time I want the alarm to go off at.

Answer 1

The technical problem here is that if you call datetime.now() over and over again, you can't always call it fast enough to get all of the possible values. So == should instead be >=. However, this still isn't very good.

A much better way to do this is to use time.sleep() instead of looping.

import datetime
import os
import time

now = datetime.datetime.now()

# Choose 6PM today as the time the alarm fires.
# This won't work well if it's after 6PM, though.
alarm_time = datetime.datetime.combine(now.date(), datetime.time(18, 0, 0))

# Think of time.sleep() as having the operating system set an alarm for you,
# and waking you up when the alarm fires.
time.sleep((alarm_time - now).total_seconds())

os.system("start BTS_House_Of_Cards.mp3")