捕获扩展异常

Question

所以我想捕获加载扩展时会引发的每个异常，我在文档中找到了这些

扩展错误：

• 扩展已加载
• ExtensionNotLoaded
• NoEntryPointError
• 扩展失败
• ExtensionNotFound

这是我一直在尝试使用的代码，但我太笨了

@bot.command()
async def reload(ctx, extension):

    try:
        bot.reload_extension(f'Cogs.{extension}')
        await ctx.send(f'reloaded {extension}')

        # raise commands.ExtensionNotFound(extension) # makes **ExtensionNotFound* prints

    except commands.ExtensionNotLoaded: # this works
        bot.load_extension(f'Cogs.{extension}')
        await ctx.send(f'{extension} was not loaded in the first place but i loaded it up for you')

    except commands.ExtensionNotFound: # doesn't catch actual exception unless it's raised
        await ctx.send('commands.ExtensionNotFound')

    except commands.ExtensionError: # didn't test coz i got hung up on the last exception
        await ctx.send('commands.ExtensionError')

    except commands.ExtensionFailed: # didn't test
        await ctx.send('commands.ExtensionFailed')

    except commands.ExtensionAlreadyLoaded: # didn't test
        await ctx.send('commands.ExtensionAlreadyLoaded')

所以我想要的是一个捕获扩展异常的工作示例（与我的弱代码不同，它确实有效）

编辑1： 如果我使用不存在的 cog !reload not_a_real_cog 调用 reload 函数，我会收到以下异常：

Ignoring exception in command reload:
Traceback (most recent call last):
  File "d:\Discord bots\Discord bot - Cogs V1\main.py", line 136, in reload
    bot.reload_extension(f'Cogs.{extension}')
  File "C:\Users\Bruh\AppData\Local\Programs\Python\Python39\lib\site-packages\discord\ext\commands\bot.py", line 759, in reload_extension  
    raise errors.ExtensionNotLoaded(name)
discord.ext.commands.errors.ExtensionNotLoaded: Extension 'Cogs.not_a_real_cog' has not been loaded.

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "C:\Users\Bruh\AppData\Local\Programs\Python\Python39\lib\site-packages\discord\ext\commands\core.py", line 85, in wrapped
    ret = await coro(*args, **kwargs)
  File "d:\Discord bots\Discord bot - Cogs V1\main.py", line 142, in reload
    bot.load_extension(f'Cogs.{extension}')
  File "C:\Users\Bruh\AppData\Local\Programs\Python\Python39\lib\site-packages\discord\ext\commands\bot.py", line 676, in load_extension    
    raise errors.ExtensionNotFound(name)
discord.ext.commands.errors.ExtensionNotFound: Extension 'Cogs.not_a_real_cog' could not be loaded.

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

Traceback (most recent call last):
  File "C:\Users\Bruh\AppData\Local\Programs\Python\Python39\lib\site-packages\discord\ext\commands\bot.py", line 939, in invoke
    await ctx.command.invoke(ctx)
  File "C:\Users\Bruh\AppData\Local\Programs\Python\Python39\lib\site-packages\discord\ext\commands\core.py", line 863, in invoke
    await injected(*ctx.args, **ctx.kwargs)
  File "C:\Users\Bruh\AppData\Local\Programs\Python\Python39\lib\site-packages\discord\ext\commands\core.py", line 94, in wrapped
    raise CommandInvokeError(exc) from exc
discord.ext.commands.errors.CommandInvokeError: Command raised an exception: ExtensionNotFound: Extension 'Cogs.not_a_real_cog' could not be loaded.

通过@CrazyChucky 在 cmets 中提供的方法再次测试ExtensionNotFound .. 我想我误解了实际捕捉它的异常是什么，尽管我试图捕捉它：

• ExtensionNotLoaded
• ExtensionNotFound
• CommandInvokeError

但我什么也没抓到

Answer 1

根据您的 cmets，我发现您不清楚 try/except clauses 的工作原理；您只能在try 部分捕获异常，而try 只会捕获它遇到的第一个异常，立即中止并转到相应的except（或else）子句。

在这种情况下，您需要将一个 try/except 嵌套在另一个中，请记住，无论您是 loading 还是 reloading，您都可能生成多个相同的错误，并且您不希望您的代码重复。

@bot.command()
async def reload(ctx, extension):
    try:

        # This inner try/except only cares about whether the extension
        # can be REloaded, or whether it needs to be loaded from
        # scratch.
        try:
            await ctx.send(f'Attempting to reload {extension} extension...')
            bot.reload_extension(f'cogs.{extension}')
        except commands.ExtensionNotLoaded:
            await ctx.send(f'{extension} is not currently loaded. Attempting '
                            'to load...')
            bot.load_extension(f'cogs.{extension}')

        await ctx.send(f'{extension} has been freshly loaded.')

    # These except clauses will be reached if their exception occurs,
    # regardless of whether or not the inner except clause was entered.

    except commands.ExtensionNotFound:
        await ctx.send(f"Error: {extension} couldn't be found to load."))

    except commands.ExtensionFailed:
        await ctx.send(f'Error: {extension} failed to load properly.')

    except commands.ExtensionError:
        await ctx.send(f'Error: unknown error with {extension}')

注意：Python 中的模块名通常都是小写，所以我将Cogs 重命名为cogs。

您可能会被 bot 的 extensions attribute 的存在所诱惑，按照以下方式进行操作：

if extension in bot.extensions:
    bot.reload_extension(f'cogs.{extension}')
else:
    bot.load_extension(f'cogs.{extension}')

但这在像这样的异步环境中是危险的，因为它是一种竞争条件：在您执行in 检查和实际尝试加载/重新加载扩展程序之间，可能有其他用户或进程可能已经加载/卸载了扩展。