goes through a text channel's chat log and writes it to a file

savePastDiscordChat.py

import discord
import asyncio

client = discord.Client()

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

@client.event
async def on_message(message):
    if message.content.startswith('record chat'):
        with open('output.txt', 'a') as the_file:
            async for log in client.logs_from(message.channel, limit=1000000000000000):
                  stringTime = log.timestamp.strftime("%Y-%m-%d %H:%M")
                  try:
                      author = log.author
                  except:
                      author = 'invalid'
                  message = str(log.content.encode("utf-8"))[2:-1]

                  template = '[{stringTime}] <{author}> {message}\n'
                  try:
                      the_file.write(template.format(stringTime=stringTime, author=author, message=message))
                  except:
                      author = log.author.discriminator
                      the_file.write(template.format(stringTime=stringTime, author=author, message=message))
                  print(template.format(stringTime=stringTime, author=author, message=message)[:-1])

    elif message.content.startswith('!sleep'):
        await asyncio.sleep(5)
        await client.send_message(message.channel, 'Done sleeping')

client.run('<your token here>', bot=False)

Discord would prefer you use a bot account to your user one. As I recall, it's in their Terms of Service.