I feel it's not proper to allow the width restrict on types %S, %R, %A. These types correspond to PyObject_Str(), PyObject_Repr, PyObject_ASCII() respectively, the results of them are usually a complete string representation of a object. If you put a width restriction on the string, it's likely that the result string is intercepted and is of no complete meaning. If you really want to put a width restriction on the result, you can use %s instead, with one or two more lines to get the corresponding char* from the object.