PEP 646 Variadic generics, https://peps.python.org/pep-0646/, was made for this specific use case but mypy is still working on implementing it. And even with it, it's expected several more peps are needed to make operations on variadic types powerful enough to handle common array operations. numpy/tensorflow/etc do broadcasting a lot and that probably would need a type level operator Broadcast just to encode that. I also expect the type definitions for numpy will go fairly complex similar to template heavy C++ code after they add shape types.