simple cogs example in discord.py

cogs.py

# main.py
from discord.ext import commands
import os

client = commands.Bot(command_prefix = "!")

for f in os.listdir("./cogs"):
	if f.endswith(".py"):
		client.load_extension("cogs." + f[:-3])

client.run("token")

# cogs / test.py
from discord.ext import commands

class Test(commands.Cog):
	def __init__(self, client):
		self.client = client # sets the client variable so we can use it in cogs
	
	@commands.Cog.listener()
	async def on_ready(self):
		# an example event with cogs
	
	@commands.command()
	async def command(self, ctx):
		# an example command with cogs

def setup(client):
	client.add_cog(Test(client))

@Tango0o0o Here is a far better version of the code:

# main.py
from discord.ext import commands
import discord

EXTENSIONS = ("extensions.example",)
INTENTS = discord.Intents.default()
INTENTS.message_content = True

bot = commands.Bot(
    intents=INTENTS,
    command_prefix="!"
)

@bot.event
async def setup_hook() -> None:
    for extension in EXTENSIONS:
        await bot.load_extension(extension)

bot.run("token")

# extensions/example.py
from discord.ext import commands

class ExampleCog(commands.Cog):
    def __init__(self, bot: commands.Bot) -> None:
        self.bot = bot
	
    @commands.Cog.listener()
    async def on_ready(self) -> None:
        pass
	
    @commands.command()
    async def command(self, ctx: commands.Context) -> None:
        pass

async def setup(bot: commands.Bot) -> None:
    await bot.add_cog(ExampleCog(bot))

I deliberately avoided automatically loading extensions, because it could lead to errors and listing the extensions manually was far simpler. Also, note that extensions and cogs are different and should be treated as such, as you can load an extension without any cogs in it at all.

@bot.event
async def setup_hook() -> None:
for extension in extensions:
await bot.load_extension(extension)

That's what I was missing in all the official and fancy guidelines.
Thank you, sir, you are a true savior!