Python try except 块在我不希望出现问题时运行异常代码，并且在我希望它运行异常代码时只给出错误

Question

I'm working on a discord bot in python that will wish people a happy birthday. I plan on having users give their birthdays to the bot via a command so that it can store it in a txt file. This is the code so far:

@bot.command(pass_context=True)
async def birthday(ctx,arg1,arg2,arg3,arg4):
    try:
        if (ctx.user == bot.user):
            return
        print(arg1 + ', ' + str(arg2) + ', ' + str(arg3) + ', ' + str(arg4))
    except:
        channel = bot.get_channel(channel_id)
        await channel.send('Oops! I didn\'t get that. Please try again using this format:\n!birthday Garfield 19 6 1978')

Basically, it should print the info it got if it is formatted correctly, and warn the user that there's a problem if it is not. This is the error message I get:

Ignoring exception in command birthday:
Traceback (most recent call last):
  File "/home/valerie/.local/lib/python3.6/site-packages/discord/ext/commands/bot.py", line 892, in invoke
    await ctx.command.invoke(ctx)
  File "/home/valerie/.local/lib/python3.6/site-packages/discord/ext/commands/core.py", line 790, in invoke
    await self.prepare(ctx)
  File "/home/valerie/.local/lib/python3.6/site-packages/discord/ext/commands/core.py", line 751, in prepare
    await self._parse_arguments(ctx)
  File "/home/valerie/.local/lib/python3.6/site-packages/discord/ext/commands/core.py", line 670, in _parse_arguments
    transformed = await self.transform(ctx, param)
  File "/home/valerie/.local/lib/python3.6/site-packages/discord/ext/commands/core.py", line 516, in transform
    raise MissingRequiredArgument(param)
discord.ext.commands.errors.MissingRequiredArgument: arg4 is a required argument that is missing.

Why is it throwing an exception when everything should work fine and not even running the except code when there actually is a problem? Is there a way to fix this?

Answer 1

Somewhere in your code, you are calling birthday function which is expecting 5 arguments. You are not providing the required number of arguments. That's why the code is failing.

If you read through the last line of the exception, you will see the error clearly called out.

discord.ext.commands.errors.MissingRequiredArgument: arg4 is a required argument that is missing.

You need to provide arg4 which you are not providing.

Answer 2

This is a general comment, but a little too big to fit in the comments... (so please ignore as you see fit)

You can group you args, and use ", ".join() to make your code a bit cleaner:

@bot.command(pass_context=True)
async def birthday(ctx, *args):
    try:
        if (ctx.user == bot.user):
            return
        print(", ".join(args))
    except:
        ...