Given a file ./tokens.txt containing many Discord bot tokens, this script will attempt login with each, and write valid tokens (plus their names and how many servers they're in) to ./valid.csv.

getnames.py

import discord
import asyncio

class Bot(discord.Client):
    def __init__(self, token):
        super().__init__()
        self.token = token
        print('%s->' % token, end='')

    async def on_ready(self):
        """Run when the bot is ready."""
        print('%s#%s' % (self.user.name, len(self.servers)))
        with open('valid.csv', 'a+') as f:
            f.write('%s,%s,%s\n' % (self.token, self.user.name, len(self.servers)))
        await self.logout()


if __name__ == '__main__':
    with open('tokens.txt') as f:
        tokens = [token for token in f.read().split('\n') if token]
    with open('valid.csv') as f:
        f.write('token,name,servers')

    loop = asyncio.get_event_loop()
    bots = []
    for token in tokens:
        bots.append(Bot(token))
        try:
            loop.run_until_complete(bots[-1].start(token))
        except discord.errors.LoginFailure:
            print('BAD TOKEN')