Scheduled tasks
A common kind of background task is an action that should run by itself in the background at any given time. Typically, those are managed through a cron daemon or similar system tools by configuring the daemon to run a given Python script at the provided time.
When you have a primary application that needs to perform tasks cyclically (such as expiring caches, resetting password links, flushing a queue of emails to send, or similar tasks), it's not really viable to do so through a cron job as you would need to dump the data somewhere accessible to the other process: on disk, on a database, or any similarly shared storage.
Luckily, the Python standard library has an easy way to schedule tasks that are to be executed at any given time and joined with threads. It can be a very simple and effective solution for scheduled background tasks.
How to do it...
The sched module provides a fully functioning scheduled tasks executor that we can mix with threads to create a background scheduler...
