old_contents: import sys
  
  
  def lowest_unique(int_list):
      numbers = {}
      for index in range(len(int_list)):
          group = numbers.setdefault(int(int_list[index]), [])
          group.append(index)
      for number in numbers:
          retval = numbers[number]
          if len(retval) == 1:
              return retval[0] + 1
      return 0
  
  
  if __name__ == '__main__':
      inputfile = sys.argv[1]
      with open(inputfile, 'r') as f:
          for line in f:
              line_list = line.rstrip().split()
              if line_list:
                  print str(lowest_unique(line_list))
  
new_contents: import sys
  
  
  def lowest_unique(int_list):
      numbers = {}
      for index, number in enumerate(int_list):
          group = numbers.setdefault(int(number), [])
          group.append(index)
      for number in sorted(numbers.keys()):
          retval = numbers[number]
          if len(retval) == 1:
              return retval[0] + 1
      return 0
  
  
  if __name__ == '__main__':
      inputfile = sys.argv[1]
      with open(inputfile, 'r') as f:
          for line in f:
              line_list = line.rstrip().split()
              if line_list:
                  print str(lowest_unique(line_list))
  
subject: Improve solution by using enumerate