Test_coroutine.py

"""
Testing with coroutines and yielding futures
This programs final ouptput is 3
get_x, and get_y simulate an async task that returns later.
"""

import tornado.ioloop
from tornado.concurrent import Future
from tornado import gen

def get_x():
    print 'Get x'
    f = Future()
    ioloop = tornado.ioloop.IOLoop.instance()
    ioloop.add_callback(_get_x, f)
    return f

def _get_x(future):
    print '_get_x'
    future.set_result(2)

def get_y():
    print 'Get y'
    f = Future()
    ioloop = tornado.ioloop.IOLoop.instance()
    ioloop.add_callback(_get_y, f)
    return f

def _get_y(future):
    print '_get_y'
    future.set_result(1)

@gen.coroutine
def gen_futures():
    print 'gen_futures'
    x = yield get_x()
    print 'x: ', x
    y = yield get_y()
    print 'y: ', y
    print x + y


def main():
    ioloop = tornado.ioloop.IOLoop.instance()
    ioloop.run_sync(gen_futures)
    ioloop.start()

if __name__ == '__main__':
    main()