apscheduler in Flask executes twice [duplicate]

Answer 1

You can start the scheduler in Flask's before_first_request() decorator, which "registers a function to be run before the first request to this instance of the application".

import time
import atexit

from apscheduler.schedulers.background import BackgroundScheduler


def print_date_time():
    print(time.strftime("%A, %d. %B %Y %I:%M:%S %p"))


@app.before_first_request
def init_scheduler():
    scheduler = BackgroundScheduler()
    scheduler.add_job(func=print_date_time, trigger="interval", seconds=3)
    scheduler.start()
    # Shut down the scheduler when exiting the app
    atexit.register(lambda: scheduler.shutdown())

Note that before_first_request() will always be called again with the first request after server reload.