code: def update_label(self):
          
          current_file = str(self.selectedFiles()[0])
          if not '.' in current_file.split(os.path.sep)[-1]:
              # add hdf5 extention if none given
              current_file += '.hdf5'
          if os.path.isfile(current_file):
              self.setLabelText(QtGui.QFileDialog.Accept, 'Reload')
          elif os.path.isdir(current_file):
              self.setLabelText(QtGui.QFileDialog.Accept, 'Open')
          else:
              self.setLabelText(QtGui.QFileDialog.Accept, 'Create')
docs: Updates the text on the accept button, to reflect if the 
          name of the data file will result in opening an existing file,
          or creating a new one