我如何从机器人离线时添加前缀。 discord.py

Question

每次机器人下线，并且有人添加机器人时，机器人不会自动添加机器人离线时的前缀。我不知道如何构建自动添加的东西，知道吗？

我收到这个错误：

Ignoring exception in on_message
Traceback (most recent call last):
  File "C:\Users\Administrator\AppData\Local\Programs\Python\Python38-32\lib\site-packages\discord\client.py", line 312, in _run_event
    await coro(*args, **kwargs)
  File "C:\Users\Administrator\AppData\Local\Programs\Python\Python38-32\lib\site-packages\discord\ext\commands\bot.py", line 930, in on_message
    await self.process_commands(message)
  File "C:\Users\Administrator\AppData\Local\Programs\Python\Python38-32\lib\site-packages\discord\ext\commands\bot.py", line 926, in process_commands
    ctx = await self.get_context(message)
  File "C:\Users\Administrator\AppData\Local\Programs\Python\Python38-32\lib\site-packages\discord\ext\commands\bot.py", line 842, in get_context
    prefix = await self.get_prefix(message)
  File "C:\Users\Administrator\AppData\Local\Programs\Python\Python38-32\lib\site-packages\discord\ext\commands\bot.py", line 787, in get_prefix
    ret = await discord.utils.maybe_coroutine(prefix, self, message)
  File "C:\Users\Administrator\AppData\Local\Programs\Python\Python38-32\lib\site-packages\discord\utils.py", line 317, in maybe_coroutine
    value = f(*args, **kwargs)
  File "C:\Users\Administrator\Desktop\doob\bot.py", line 16, in get_prefix
    return prefixes[str(message.guild.id)]
KeyError: '{insert server id here}

(prefix.py):

class prefix(commands.Cog):
    def __init__(self, client):
        self.client = client

    # Opens json file then dumps '-'
    @commands.Cog.listener()
    async def on_guild_join(self, guild):
        with open('prefixes.json', 'r') as f:
            prefixes = json.load(f)

        prefixes[str(guild.id)] = "-"

        with open('prefixes.json', 'w') as f:
            json.dump(prefixes, f, indent=4)

    # Removes guild from json file when Doob leaves.
    @commands.Cog.listener()
    async def on_guild_remove(self, guild):
        with open('prefixes.json', 'r') as f:
            prefixes = json.load(f)

        prefixes.pop(str(guild.id))

        with open('prefixes.json', 'w') as f:
            json.dump(prefixes, f, indent=4)

    # Changes the prefix (that the user provides.) for the specific server.
    @commands.command(aliases=['prefix'])
    @commands.has_permissions(administrator=True)
    async def changeprefix(self, ctx, prefix):
        with open('prefixes.json', 'r') as f:
            prefixes = json.load(f)

        prefixes[str(ctx.guild.id)] = prefix

        with open('prefixes.json', 'w') as f:
            json.dump(prefixes, f, indent=4)

        embed = discord.Embed(title="An administrator has changed the prefix.", description=f"An administrator has changed the prefix to {prefix}.", colour=discord.Color.blue())

        embed.add_field(name="The prefix has been changed to:", value=prefix)
        embed.set_thumbnail(url=doob_logo)
        await ctx.send(embed=embed)

(bot.py):

# Creates and loads the json file.
def get_prefix(client, message):
    with open('prefixes.json', 'r') as f:
        prefixes = json.load(f)

    return prefixes[str(message.guild.id)]

client = commands.Bot(command_prefix = get_prefix)

有人要我的代码，所以这是我的代码，我仍然需要帮助，所以任何帮助！先谢谢你了！！！

Answer 1

我个人会采取不同的做法，而不是为每个新公会设置一个前缀，只为设置了前缀的公会设置自定义前缀以避免这种情况。像这样的事情会做你现在所做的事情，除了它应该处理所有行会，因为它是 fallback/default 前缀

def get_prefix(client, message):
    with open('prefixes.json', 'r') as f:
        prefixes = json.load(f)
    try:
         return prefixes[str(message.guild.id)]
    except KeyError:
         return '-

我如何从机器人离线时添加前缀。 discord.py

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