Python 有没有办法避免json中的重复值？

它运行得很好，但每次我重新运行它时，它都会添加已经在json文件中的用户id，从而导致重复的值。有办法解决吗

with open('./data/faction1.json','r', encoding='utf-8') as f:
  try:
    faction = json.load(f)
  except ValueError:
    faction = {}
    faction['users'] = []


class clan(commands.Cog):
    def __init__(self, bot):
        self.bot = bot

    @commands.command()
    async def join(self, ctx):

        new_user = ctx.author.id
        if new_user not in faction['users']:
            faction['users'][new_user] = ctx.author.name
            await ctx.send("you have been added to the faction")
            with open('./data/faction1.json', 'w') as f:
                json.dump(faction, f)
            
        else:
            await ctx.send("already in faction")

---

json将键保存为字符串，但

ctx.author.id

是一个整数。使用

new\u user=str（ctx.author.id）

可能会有所帮助。真是太棒了，它成功了@乌普斯