我如何检查指定用户是否是有效用户（也在服务器中）（discord.py）

Question

So when this command is executed it fetches a discord user and i want to make it so that if the specified user isnt real or isnt in the discord server it will delete the message and send a dm to the message author saying that the user isnt real

  @commands.command()
  async def rickroll(self, ctx, user : discord.User = None):

    if user == None:
      none_embed = discord.Embed(title = "Missing argument - You didnt specify the user", color = 0xff0000)
      await ctx.author.send(embed = none_embed)
      await ctx.message.delete()
      return

    rickroll = ("just for the sake of the question i didnt write the lyrics otherwise it will be too long")

    rickroll_embed = discord.Embed(title = f"You have been rickrolled by {ctx.author}", description = rickroll, color = 0x00ceea)
    await ctx.message.delete()
    await user.send(embed = rickroll_embed)

    author_embed = discord.Embed(title = f"Sent the rickroll to {user}!", color = 0x00ceea)
    await ctx.author.send(embed = author_embed)

Answer 1

The error message that comes up if the user is not in the server is a UserNotFound error. You have to build your own error handler for that, discord.py helps you with that.

Have a look at the following code:

@rickroll.error
async def rickroll_error(self, ctx, error):
    if isinstance(error, commands.UserNotFound):
        await ctx.author.send("User not found.") # Or whatever you want to send

This code has to be under your actual rickroll command in order to work.

See the docs for more.