byte types

[Gribouillis]

this is the limitation that prevents making a function (named whatever you want to name it) do as i described

I didn't say that. I say that the clen() function can behave the way you want for ALL types, but that this behavior can be based on a __clen__ attribute only for user defined types because one can not add members to builtin types.

It is a limitation that we cannot add members to builtin types BUT it doesn't prevent us from implementing a dynamic clen() function by the means of functools.singledipatch.