基于类的Discord Bot .hello命令报错：缺少ctx参数求助

编写了基于类的Discord Bot实现简单hello功能，代码启动正常，使用.help命令能看到hello选项，但调用.hello命令时无响应且触发TypeError，提示缺少必需的ctx参数。

代码 #

import discord 
from discord.ext import commands

class Bot(commands.Bot):
    async def on_ready(self):
        print(f"bot {self.user.display_name} started succesfully!!")

    @commands.command()
    async def hello(self, ctx):
        await ctx.send(f'hello {ctx.author.display_name}')

    def __init__(self, **kwargs):
        super().__init__(**kwargs)
        self.add_command(self.hello)

intents= discord.Intents.default()
intents.message_content= True
bot= Bot(command_prefix= '.', intents= intents)

tokn= 'MTE5MzU5NDM5ODI0NDYxODI3MA.GpvNRT.T1kNBXpP3egZ_g3a-8hOhYrmzzPIMtYGSOdPro'

bot.run(tokn) 

报错信息 #

Traceback (most recent call last):
  File "C:\Users\risha\AppData\Local\Programs\Python\Python310\lib\site-packages\discord\ext\commands\core.py", line 235, in wrapped      
    ret = await coro(*args, **kwargs)
TypeError: Bot.hello() missing 1 required positional argument: 'ctx'

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "C:\Users\risha\AppData\Local\Programs\Python\Python310\lib\site-packages\discord\ext\commands\bot.py", line 1350, in invoke       
    await ctx.command.invoke(ctx)
  File "C:\Users\risha\AppData\Local\Programs\Python\Python310\lib\site-packages\discord\ext\commands\core.py", line 1029, in invoke      
    await injected(*ctx.args, **ctx.kwargs)  # type: ignore
  File "C:\Users\risha\AppData\Local\Programs\Python\Python310\lib\site-packages\discord\ext\commands\core.py", line 244, in wrapped      
    raise CommandInvokeError(exc) from exc
discord.ext.commands.errors.CommandInvokeError: Command raised an exception: TypeError: Bot.hello() missing 1 required positional argument: 'ctx'

问题原因 #

问题出在手动调用self.add_command(self.hello)。当用@commands.command()装饰类成员方法时，装饰器会把方法包装成Command对象，但直接传递self.hello时，没有正确绑定Bot实例，导致调用时无法自动传入self（Bot实例），进而把原本应该是self的位置当成了ctx参数，最终出现缺少ctx的错误。

解决方案 #

方案1：移除手动添加命令的代码（推荐） #

@commands.command()装饰器会自动将方法注册为Bot的命令，无需手动调用add_command。修改后的代码：

import discord 
from discord.ext import commands

class Bot(commands.Bot):
    async def on_ready(self):
        print(f"bot {self.user.display_name} started succesfully!!")

    @commands.command()
    async def hello(self, ctx):
        await ctx.send(f'hello {ctx.author.display_name}')

    def __init__(self, **kwargs):
        super().__init__(**kwargs)
        # 移除手动添加命令的代码

intents= discord.Intents.default()
intents.message_content= True
bot= Bot(command_prefix= '.', intents= intents)

tokn= '你的Bot令牌'
bot.run(tokn) 

方案2：手动添加时使用copy()获取绑定后的命令 #

如果需要保留手动添加命令的逻辑，使用self.hello.copy()创建绑定了当前Bot实例的Command副本：

def __init__(self, **kwargs):
    super().__init__(**kwargs)
    self.add_command(self.hello.copy())

内容的提问来源于stack exchange，提问作者risav68111