def blocking_task(n):
    for i in xrange(n):
        print i
        sleep(1)
    return i

import threading
import datetime
import time

def blocking_task(n):
    for i in xrange(n):
        print i
        time.sleep(1)
    return i

print "This is the begin of a blocking call. Started at %s"
      % datetime.datetime.now()
blocking_task(5)
print "This is the end of a blocking call. Ended at %s"
    % datetime.datetime.now()

th = threading.Thread(target=blocking_task, args=[5])
print "This is the beginning of a non-blocking call. Started at %s"
      % datetime.datetime.now()
th.start()
print "This is the end of a non-blocking call. Ended at %s"
      % datetime.datetime.now()

This is the begin of a blocking call. Started at 2014-04-07 15:14:41.763855
0
1
2
3
4
This is the end of a blocking call. Ended at 2014-04-07 15:14:46.768890
This is the beginning of a non-blocking call. Started at 2014-04-07 15:14:46.769160
0
 This is the end of a non-blocking call. Ended at 2014-04-07 15:14:46.769523
1
2
3
4

#!/usr/bin/python

import tornado.web
from tornado.ioloop import IOLoop
from tornado import gen
import time

@gen.coroutine
def async_sleep(seconds):
    yield gen.Task(IOLoop.instance().add_timeout, time.time() + seconds)

class TestHandler(tornado.web.RequestHandler):
    @gen.coroutine
    def get(self):
        for i in xrange(100):
            print i
            yield async_sleep(1)
        self.write(str(i))
        self.finish()


application = tornado.web.Application([
    (r"/test", TestHandler),
    ])

application.listen(9999)
IOLoop.instance().start()

add_timeout(deadline, callback) # deadline is the number of seconds to wait, callback is the method to call after deadline.

add_timeout(time.time() + seconds, ???)

yield gen.Task(loop.add_timeout, time.time() + seconds)

loop.add_timeout(time.time() + seconds, callback=gen.Callback(some_unique_key))