老师，我在调用命令行参数时，出现了“An exception has occurred, use %tb to see the full traceback. SystemExit: 2” 这样的显示，请问是什么原因？

import os import argparse def add(arg1, arg2): return arg1+arg2 def substract(arg1, arg2): return arg1-arg2 def args_opt(): parser = argparse.ArgumentParser( description="Return sum and difference of two numbers if both are integers") parser.add_argument("arg1") parser.add_argument("arg2") return parser.parse_args() if __name__ == "__main__": args = args_opt() try: val1, val2 = int(args.arg1), int(args.arg2) print(add(val1, val2), substract(val1, val2)) except ValueError: print(f"At least one of {args.arg1,args.arg2} is not integer")

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