> 3) Pick your value encoding carefully. You almost always want fast immediate integers. On 64-bit platforms it is quite common these days to repurpose some of the NaN range in IEEE doubles for type tags to enable storing doubles in immediate values.

That technique applies more to JavaScript, which uses doubles as the standard number type, than in Python, which has both integers and floats. Still a good idea to make sure that both native integers and native floats end up as unboxed native types in registers, though.