Python script to do something at the same time every day

You can do that like this:

from datetime import datetime
from threading import Timer

x=datetime.today()
y=x.replace(day=x.day+1, hour=1, minute=0, second=0, microsecond=0)
delta_t=y-x

secs=delta_t.seconds+1

def hello_world():
    print "hello world"
    #...

t = Timer(secs, hello_world)
t.start()

This will execute a function (eg. hello_world) in the next day at 1a.m.

EDIT:

As suggested by @PaulMag, more generally, in order to detect if the day of the month must be reset due to the reaching of the end of the month, the definition of y in this context shall be the following:

y = x.replace(day=x.day, hour=1, minute=0, second=0, microsecond=0) + timedelta(days=1)

With this fix, it is also needed to add timedelta to the imports. The other code lines maintain the same. The full solution, using also the total_seconds() function, is therefore:

from datetime import datetime, timedelta
from threading import Timer

x=datetime.today()
y = x.replace(day=x.day, hour=1, minute=0, second=0, microsecond=0) + timedelta(days=1)
delta_t=y-x

secs=delta_t.total_seconds()

def hello_world():
    print "hello world"
    #...

t = Timer(secs, hello_world)
t.start()

I spent quite a bit of time also looking to launch a simple Python program at 01:00. For some reason, I couldn't get cron to launch it and APScheduler seemed rather complex for something that should be simple. Schedule (https://pypi.python.org/pypi/schedule) seemed about right.

You will have to install their Python library:

pip install schedule

This is modified from their sample program:

import schedule
import time

def job(t):
    print "I'm working...", t
    return

schedule.every().day.at("01:00").do(job,'It is 01:00')

while True:
    schedule.run_pending()
    time.sleep(60) # wait one minute

You will need to put your own function in place of job and run it with nohup, e.g.:

nohup python2.7 MyScheduledProgram.py &

Don't forget to start it again if you reboot.