fwiw, it is not the case that pinball can schedule jobs only at specific times of the day. In fact the scheduler is merely a special type of worker that happens to start new workflows. It is totally doable to kick off a new workflow at any point in time, bypassing the scheduler.

Also, Pinball is also all Python but it currently has a dependency on mysql so it is definitely not as a lightweight as a standalone tool as luigi but it also offers much more in terms of the available features.