code: def maxRange(self):
          
          try:
              x, freqs = self.datafile.get_calibration(str(self.ui.calChoiceCmbbx.currentText()), self.calf)
              self.ui.frangeLowSpnbx.setValue(freqs[0])
              self.ui.frangeHighSpnbx.setValue(freqs[-1])
              print 'set freq range', freqs[0], freqs[-1], freqs[0], freqs[-1]
          except IOError:
              QtGui.QMessageBox.warning(self, "File Read Error", "Unable to read calibration file")
          except KeyError:
              QtGui.QMessageBox.warning(self, "File Data Error", "Unable to find data in file")
docs: Sets the maximum range for the currently selection calibration,
          determined from its range of values store on file