It is faulty to think of the math notation and code being equivalent. The math states something much more general, and often much deeper, than some mundane for-loop. I’d have titled this “Python Recipes to Calculate Values of Simple Vector Math Expressions”.

Often times the symbols may not even be concrete numbers. Often the “real” number may not even be representable on a computer. Often a symbol does represent a concrete number but indirectly defined by some set of rules (e.g., x is the smallest eigenvalue of M; or y is the greatest value less than the supremum of f) that may require a whole library of code to calculate.

The mathematical notation is “meant” to be flexible and manipulated, not to be interpreted (necessarily) as a rigid computational process. It should also be noted that while some notation comes from convention, a lot of it is improvised and contextual!