code: def three_digit(number):
      
      number = str(number)
      if len(number) == 1:
          return u'00%s' % number
      elif len(number) == 2:
          return u'0%s' % number
      else:
          return number
docs: Add 0s to inputs that their length is less than 3.
  
      :param number:
          The number to convert
      :type number:
          int
  
      :returns:
          String
  
      :example:
          >>> three_digit(1)
          '001'