How do I mention a user using user's id in discord.py?

So I finally figured out how to do this after few days of trial and error hoping others would benefit from this and have less pain than I actually had.. The solution was ultimately easy..

  if message.content.startswith('!best'):
        myid = '<@201909896357216256>'
        await client.send_message(message.channel, ' : %s is the best ' % myid)

If you're working on commands, you're best to use discord.py's built in command functions, your hug command will become:

import discord
from discord.ext import commands

@commands.command(pass_context=True)
async def hug(self, ctx):
    await self.bot.say("hugs {}".format(ctx.message.author.mention()))

This is assuming you've done something like this at the start of your code:

def __init__(self):
    self.bot = discord.Client(#blah)

From a User object, use the attribute User.mention to get a string that represents a mention for the user. To get a user object from their ID, you need Client.get_user_info(id). To get the a user from a username ('ZERO') and discriminator ('#6885') use the utility function discord.utils.get(iterable, **attrs). In context:

if message.content.startswith('!best'):
    user = discord.utils.get(message.server.members, name = 'ZERO', discriminator = 6885)
    # user = client.get_user_info(id) is used to get User from ID, but OP doesn't need that
    await client.send_message(message.channel, user.mention + ' mentioned')