Some Event Listeners
Event listeners can be used in many different ways like keeping track of the servers that the bot gets added to.
To keep track of what server your bot has joined, the on_guild_join() method can be called via the @client.event decorator.
mkdir guilds.json-
import jsonPython module
import json
...
@client.event
async def on_guild_join(guild):
with open('guilds.json', 'r') as f:
guilds = json.load(f)
# Set default prefix variable and name of server
guilds[str(guild.id)] = {
"guild Name": guild.name,
"Prefix": "$"
}
# Push dictionary to JSON file
with open('guilds.json', 'w') as f:
json.dump(guilds, f, indent=4)
...
Likewise for when the bot is removed from the server to clean up the JSON file with on_guild_remove().
...
@client.event
async def on_guild_remove(guild):
with open('guilds.json', 'r') as f:
guilds = json.load(f)
# Remove guild dictionary from JSON file
guilds.pop(str(guild.id))
# Apply changes to file
with open('guilds.json', 'w') as f:
json.dump(guilds, f, indent=4)
...
If you would like to create some interaction with the bot and have a "conversation" the on_message() method has some things it can do.
This can be customized to fit your needs, but here's a basic example.
...
@client.event
async def on_message(message):
# Stop the bot from replying to itself or any other bot
if message.author.bot: return
# Send a reply to a human
if message.content == "ping":
await message.channel.send("pong")
...
Cogs
Adding commands and event listeners to the main file will create unnecessary clutter. Using extensions will create a space to fill in more methods to be used in more concise ways. To do this, the Cog class will be required.
Cog Decorator
To create a cog file, each will need to an instance of a new class.
Cog template
from nextcord.ext import commands
class <ClassName>(commands.Cog):
# Initialize with `self` and `bot: commands.Bot`
def __init__(self, bot: commands.Bot):
self.bot = bot
# All commands/listeners always take a parameter of "self"
@commands.Cog.listener()
async def <commandName>(self):
# Do some stuff
def setup(bot: commands.Bot):
bot.add_cog(<ClassName>(bot))
Error Handler
Having a custom error handler will come in handy to provide client feedback about their issued command.
...
async def on_command_error(self, ctx: commands.Content, error: commands.CommandError):
if isinstance(error, commands.CommandNotFound):
message = f'{error}'
elif isinstance(error, commands.UserInputError):
message = 'Your input was incorrect'
else:
message = 'Something went wrong while running a command'
await ctx.send(message, delete_after=5)
await ctx.message.delete(delay=5)
...
The isinstance() method takes in two parameters and returns a boolean:
- an
object class or tuple- returns
bool
Loading Cogs
After creating some cogs, go back into the main bot.py file and a for loop will be needed to load the cogs upon bot startup.
Along with this if not already done, you'll need to import the os module at the top of the file.
import os
...
# Load extensions on bot start
for filename in os.listdir('./cogs'):
if filename.endswith('.py'):
client.load_extension(f'cogs.{filename[:-3]}')
...
If now errors found within the extensions the bot will start up and the cogs will now be ready for use.
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