The dunder method __new__ is used to customise object creation and is a core stepping stone in understanding metaprogramming in Python.
__new__
Today I learned how to use the dunder method __init_subclass__ to be notified when a class is subclassed.
__init_subclass__
Russian mathematician Grigori Perelman declined a $1,000,000 prize after solving one of the seven Millenium Prize Problems.