@wolma, That would work in this simple example. But in a more complicated case this became inconvenient.

Actually I'm working with reading and writing in python an extremely C-oriented file-type (MDV). For that I represent C-structs as python dics (e.q {"array":[v1,v2,v3,v4]}), and because of this lack of arrays I'm forced to keep track if a key represents a single value or an array. It works, but I think everyone would benefit if struct could handle that simple task.