There's no language in which you would be able to write a function for arbitrary data structures using sum(), and get a reasonable outcome.
The problem with Python is that it doesn't have typing that can express "I can sum".
The problem with Python is that it doesn't have typing that can express "I can sum".
# Python 3.8
from typing import Protocol, TypeVar
T = TypeVar('T')
class Summable(Protocol[T]):
def __add__(self, other: T) -> T: ...
from typing_extensions import ProtocolC++ added such feature, this above looks like a Python version, Rust has it, Scala had them as one of the first "OOP" languages.
It's nice to see that Haskell pioneered a very useful and now spreading language feature!
Computing the number of bytes used by a data type seems perfectly reasonable use of sum in that context. This is also achievable in many languages. All 'sum' needs is a map from a value to a number, which can have many sensible meanings even for arbitrary data types.
sum(map(mappingFunction, iterable))