import sys from argparse import ArgumentParser argparser = ArgumentParser() argparser.add_argument('file', help='Input filename') args = argparser.parse_args(sys.argv[1:]) flines = open(args.file) line_list = [] for line in flines: line_list.append(line[4:8]) line_list.append(line[0:4]) flines.close() out_file = open('halfword_inst_' + args.file, "w") for line in line_list: out_file.write(line + '\n') out_file.close()