code: def preloop(self):
          ''' Keep persistent command history. '''
          if not self.already_prelooped:
              self.already_prelooped = True
              open('.psiturk_history', 'a').close()  # create file if it doesn't exist
              readline.read_history_file('.psiturk_history')
              for i in range(readline.get_current_history_length()):
                  if readline.get_history_item(i) is not None:
                      self.history.append(readline.get_history_item(i)f preloop(self):
          ''' Keep persistent command history. '''
          if not self.already_prelooped:
              self.already_prelooped = True
              open('.psiturk_history', 'a').close()  # create file if it doesn't exist
              readline.read_history_file('.psiturk_history')
              for i in range(readline.get_current_history_length()):
                  if readline.get_history_item(i) is not None:
                      self.history.append(readline.get_history_item(i))
docs: Keep persistent command history.