import tornado.ioloop
import tornado.web

from tornado.options import define, options

define("your_var", default="defined var")
# http://www.tornadoweb.org/en/stable/options.html?highlight=options#tornado.options.options
options.parse_command_line()
# or
#tornado.options.parse_config_file("/etc/server.conf")

class MainHandler(tornado.web.RequestHandler):
  def get(self):
    self.write("Hello, world " + options.your_var)

def make_app():
  return tornado.web.Application([
    (r"/", MainHandler),
  ])

if __name__ == "__main__":
  app = make_app()
  app.listen(8888)
  tornado.ioloop.IOLoop.current().start()