But that's not really true either - there's __len__ which len() calls: https://docs.python.org/3/reference/datamodel.html#object.__len__ https://docs.python.org

But that's not really true either - there's __len__ which len() calls: https://docs.python.org/3/reference/datamodel.html#object.__len__ https://docs.python.org/3/reference/datamodel.html#object.__... You can add iterators with __iter__, reversed() calls __reversed__, etc.