Discord bot

import discord
import youtube_dl
from discord.ext import commands

TOKEN = 'your_token_here'

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

@client.event
async def on_ready():
    print('Logged in as {0.user}'.format(client))

@client.command()
async def join(ctx):
    if ctx.author.voice is None:
        await ctx.send("You are not connected to a voice channel")
        return
    voice_channel = ctx.author.voice.channel
    if ctx.voice_client is None:
        await voice_channel.connect()
    else:
        await ctx.voice_client.move_to(voice_channel)

@client.command()
async def leave(ctx):
    await ctx.voice_client.disconnect()

@client.command()
async def play(ctx, url):
    if ctx.voice_client is None:
        await ctx.send("I'm not connected to a voice channel")
        return
    player = await YTDLSource.from_url(url, loop=client.loop)
    ctx.voice_client.play(player, after=lambda e: print('Player error: %s' % e) if e else None)
    await ctx.send(f'Now playing: {player.title}')

class YTDLSource(discord.PCMVolumeTransformer):
    def __init__(self, source, *, data, volume=0.5):
        super().__init__(source, volume)
        self.data = data
        self.title = data.get('title')
        self.url = data.get('url')

    @classmethod
    async def from_url(cls, url, *, loop=None):
        loop = loop or asyncio.get_event_loop()
        data = await loop.run_in_executor(None, lambda: youtube_dl.YoutubeDL({'format': 'bestaudio', 'quiet': True}).extract_info(url, download=False))
        if 'entries' in data:
            data = data['entries'][0]
        filename = data['url'] if 'url' in data else data['id']
        return cls(discord.FFmpegPCMAudio(filename), data=data)

client.run(TOKEN)