discord.py's basic_bot.py converted to use "cogs".

basic_bot.py

from discord.ext import commands

description = '''An example bot to showcase the discord.ext.commands extension
module.

There are a number of utility commands being showcased here.'''

# this specifies what extensions to load when the bot starts up
startup_extensions = ["members", "rng"]

bot = commands.Bot(command_prefix='?', description=description)

@bot.event
async def on_ready():
    print('Logged in as')
    print(bot.user.name)
    print(bot.user.id)
    print('------')

@bot.command()
async def load(extension_name : str):
    """Loads an extension."""
    try:
        bot.load_extension(extension_name)
    except (AttributeError, ImportError) as e:
        await bot.say("```py\n{}: {}\n```".format(type(e).__name__, str(e)))
        return
    await bot.say("{} loaded.".format(extension_name))

@bot.command()
async def unload(extension_name : str):
    """Unloads an extension."""
    bot.unload_extension(extension_name)
    await bot.say("{} unloaded.".format(extension_name))

@bot.command()
async def add(left : int, right : int):
    """Adds two numbers together."""
    await bot.say(left + right)

@bot.command()
async def repeat(times : int, content='repeating...'):
    """Repeats a message multiple times."""
    for i in range(times):
        await bot.say(content)

if __name__ == "__main__":
    for extension in startup_extensions:
        try:
            bot.load_extension(extension)
        except Exception as e:
            exc = '{}: {}'.format(type(e).__name__, e)
            print('Failed to load extension {}\n{}'.format(extension, exc))

    bot.run('token')

members.py

import discord
from discord.ext import commands

class Members():
    def __init__(self, bot):
        self.bot = bot

    @commands.command()
    async def joined(self, member : discord.Member):
        """Says when a member joined."""
        await self.bot.say('{0.name} joined in {0.joined_at}'.format(member))

    @commands.group(pass_context=True)
    async def cool(self, ctx):
        """Says if a user is cool.

        In reality this just checks if a subcommand is being invoked.
        """
        if ctx.invoked_subcommand is None:
            await self.bot.say('No, {0.subcommand_passed} is not cool'.format(ctx))

    @cool.command(name='bot')
    async def _bot(self):
        """Is the bot cool?"""
        await self.bot.say('Yes, the bot is cool.')


def setup(bot):
    bot.add_cog(Members(bot))

rng.py

import random
from discord.ext import commands

class RNG():
    def __init__(self, bot):
        self.bot = bot

    @commands.command()
    async def roll(self, dice : str):
        """Rolls a dice in NdN format."""
        try:
            rolls, limit = map(int, dice.split('d'))
        except Exception:
            await self.bot.say('Format has to be in NdN!')
            return

        result = ', '.join(str(random.randint(1, limit)) for r in range(rolls))
        await self.bot.say(result)

    @commands.command(description='For when you wanna settle the score some other way')
    async def choose(self, *choices : str):
        """Chooses between multiple choices."""
        await self.bot.say(random.choice(choices))


def setup(bot):
    bot.add_cog(RNG(bot))

A rewrite cogs example can be found here: https://gist.github.com/EvieePy/d78c061a4798ae81be9825468fe146be

Credits to Leo for some of the content and other members for helping.

@leovoel An example of this with automatic dir loading: https://gist.github.com/Modelmat/b2f92ad6db3d89302649ceb6dcb19744

how do you use the NDN format for the roll command

Thank you! This is super informative and helpful.

@PythonJames:

N stands for the amount of dice to be thrown
d is a separator
N is the amount of sides on said dice.

For example: 5d6 would throw 5 6-sided dice.

@PythonJames:

N stands for the amount of dice to be thrown
d is a separator
N is the amount of sides on said dice.

For example: 5d6 would throw 5 6-sided dice.

Thanks that was really helpful

Awesome!