[eesmith]

You did write "two numbers" ;)

Guess I could also have used 5j + 3 as a counter-example.

If this is an issue then at this stage, many Python people switch to use one of the alternatives mentioned here, like Cython, which is a Python-like language which includes a static type system (including support for C++ templates) and can easily generate C extensions that can call and be called from Python.