APScheduler (short for Advanced Python Scheduler) is an external Python library that supports the scheduling of Python code to be executed later, either once or periodically. This library gives us high-level options to dynamically add/remove jobs to/from the job list so they can be scheduled and executed, as well as to decide how to distribute those jobs to different threads and processes.

Some might think of Celery (http://www.celeryproject.org/) as the go-to scheduling tool for Python. However, while Celery is a distributed task queue with basic scheduling capabilities, APScheduler is quite the opposite: a scheduler with basic task queuing options and advanced scheduling functionalities. Additionally, users of both tools have reported that APScheduler is easier to set up and implement.