settings.py is for Django settings; it's fine to put your own settings in there, but using it for arbitrary non-configuration data structures isn't good practice.
Just put it in the module it logically belongs to, and it'll be run just once per instance. If you want to guarantee that the module is loaded on startup and not on first use later on, import that module from your top-level __init__.py
to force it to be loaded immediately.
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