How to Build a Discord Bot With Slash Commands Using discord.py 2.0

You want to create a Discord bot that uses slash commands instead of traditional prefix-based commands. Slash commands appear in the user interface and provide autocomplete, required options, and permission controls. This article walks through building a basic bot with Python 3.8 or later using the discord.py 2.0 library. You will learn how to set up your bot token, write a command group, and deploy the bot to a server.

What Is discord.py 2.0 and How Slash Commands Work

discord.py 2.0 is a major update to the popular Python library for interacting with the Discord API. The library now supports Application Commands, which include slash commands, user context menu commands, and message context menu commands. Slash commands are commands that users type with a forward slash and are defined in code rather than parsed from a message prefix like ! or ..

When a user types a slash command, Discord sends an interaction event to your bot. Your bot receives the interaction, processes it, and responds within three seconds. For longer processing, you can defer the response and then send a follow-up. The discord.app_commands module handles parsing of options, autocomplete, and permission checks automatically.

Prerequisites for This Tutorial

Before you start, you need the following:

• Python 3.8 or later installed on your computer
• A Discord account and a server where you have the Manage Server permission
• A Discord application created at the Discord Developer Portal
• The bot token from the Developer Portal
• The bot invited to your server with the applications.commands scope

Steps to Create and Run a Slash Command Bot

Follow these steps to build a bot that responds to /hello with a greeting.

1. Install discord.py 2.0
   Open a terminal and run pip install -U discord.py. Verify the version with pip show discord.py. The version should be 2.0.0 or later.
2. Create a Python file for the bot
   Create a file named bot.py and open it in a code editor. Write the import statements at the top: import discord and from discord.ext import commands.
3. Define the bot instance with intents
   Write the following code to create a bot instance. Intents are required for the bot to receive events. For slash commands, you need at least the default intents.
   intents = discord.Intents.default()
bot = commands.Bot(command_prefix='/', intents=intents)
4. Add an event for when the bot is ready
   Write an on_ready event that prints a message when the bot connects. This confirms the bot is online.
   @bot.event
async def on_ready():
print(f'Logged in as {bot.user}')
5. Create a slash command using the tree
   Use the @bot.tree.command decorator to define a slash command named hello. The function name becomes the command name unless you specify a name parameter.
   @bot.tree.command(name="hello", description="Says hello")
async def hello(interaction: discord.Interaction):
await interaction.response.send_message(f"Hello, {interaction.user.mention}!")
6. Sync the command tree
   After defining commands, call bot.tree.sync() inside the on_ready event or in a separate setup function. This uploads the command definitions to Discord servers. The bot must be in a server for the commands to appear.
   @bot.event
async def on_ready():
await bot.tree.sync()
print(f'Logged in as {bot.user}')
7. Run the bot with your token
   At the bottom of the file, add bot.run('YOUR_BOT_TOKEN'). Replace YOUR_BOT_TOKEN with the actual token from the Developer Portal. Do not share this token.
8. Start the bot
   Run python bot.py in the terminal. You should see the logged-in message. Open Discord and type /hello in any channel where the bot has access. The bot should reply with a greeting.

Common Issues When Building Slash Command Bots

Commands Do Not Appear in Discord

The most common cause is that the command tree has not been synced. Make sure you call await bot.tree.sync() after all commands are defined. If you add or remove commands later, you must sync again. Also verify that the bot has the applications.commands scope when you invite it. Use the OAuth2 URL generator in the Developer Portal and select the bot and applications.commands scopes.

Bot Does Not Respond to Slash Commands

Check that your bot is online in the Discord server member list. If the bot is online but does not respond, the interaction may be timing out. Discord expects a response within three seconds. If your code takes longer, use await interaction.response.defer() first, then send a follow-up with await interaction.followup.send(). Also check that your bot has the necessary permissions in the channel.

Slash Command Options Not Working

When you add options to a slash command, use the @app_commands.describe() decorator or pass parameters directly. For example:
@bot.tree.command(name="greet", description="Greets a user")
@app_commands.describe(user="The user to greet")
async def greet(interaction: discord.Interaction, user: discord.Member):
await interaction.response.send_message(f"Hello, {user.mention}!")
Options must have type hints such as str, int, discord.Member, or discord.Role. If the type is wrong, the command will not register.

Commands Work Locally but Not After Hosting

If you move your bot to a cloud server, ensure the Python environment has discord.py 2.0 installed. Also check that the bot token is set as an environment variable rather than hardcoded. Use os.getenv('DISCORD_TOKEN') to read the token from the environment. This prevents accidental exposure.

Comparison: discord.py 2.0 Slash Commands vs Traditional Prefix Commands

Feature	Slash Commands (discord.py 2.0)	Traditional Prefix Commands
User interface	Shows in command list with autocomplete and descriptions	No UI, users must remember the prefix and command name
Permission control	Can require specific permissions per command, enforced by Discord	Must check permissions manually in code
Input validation	Options are typed and validated by Discord before sending to bot	Bot must parse and validate arguments from message text
Latency	Interaction must be acknowledged within 3 seconds, then follow-up allowed	Bot can take as long as needed to process and reply
Global availability	Commands sync globally but may take up to an hour to appear in all servers	Commands are available immediately after bot starts

You now have a working Discord bot that uses slash commands. The next step is to add more commands with options and autocomplete. You can also create groups of commands using @bot.tree.command(guild=discord.Object(id=GUILD_ID)) to test commands in a single server before making them global. Use the discord.app_commands documentation to explore advanced features like context menus and cooldowns.