text: def weekday_name(day_of_week):
      """Return name of weekday.
  
          >>> weekday_name(1)
          'Sunday'
  
          >>> weekday_name(7)
          'Saturday'
  
      For days not between 1 and 7, return None
  
          >>> weekday_name(9)
          >>> weekday_name(0)
      """
  
      day = {
          1:"Sunday",
          2:"Monday",
          3:"Tuesday",
          4:"Wednesday",
          5:"Thursday",
          6:"Friday",
          7:"Saturday",
      }
      return day.get(day_of_week,None)
  
  print(weekday_name(7))
  print(weekday_name(1))
  print(weekday_name(9))
  print(weekday_name(0))