code: def randval(self):
          
          fmtt = self.fmt[-1]
          if fmtt in "BHIQ":
              return {"B":RandByte,"H":RandShort,"I":RandInt, "Q":RandLong}[fmtt]()
          elif fmtt == "s":
              if self.fmt[0] in "0123456789":
                  l = int(self.fmt[:-1])
              else:
                  l = int(self.fmt[1:-1])
              return RandBin(l)
          else:
              warning("no random class for [%s] (fmt=%s)." % (self.name, self.fmt))
docs: Return a volatile object whose value is both random and suitable for this field