from tornado.gen import coroutine
from tornado.web import Application, RequestHandler
from tornado_sqlalchemy import as_future, SessionMixin, SQLAlchemy

class NativeCoroutinesRequestHandler(SessionMixin, RequestHandler):
    async def get(self):
        with self.make_session() as session:
            count = await as_future(session.query(User).count)

        self.write('{} users so far!'.format(count))

class GenCoroutinesRequestHandler(SessionMixin, RequestHandler):
    @coroutine
    def get(self):
        with self.make_session() as session:
            count = yield as_future(session.query(User).count)

        self.write('{} users so far!'.format(count))

class SynchronousRequestHandler(SessionMixin, RequestHandler):
    def get(self):
        with self.make_session() as session:
            count = session.query(User).count()

        self.write('{} users so far!'.format(count))

handlers = (
   (r'/native-coroutines', NativeCoroutinesRequestHandler),
   (r'/gen-coroutines', GenCoroutinesRequestHandler),
   (r'/sync', SynchronousRequestHandler),
)

app = Application(
   handlers,
   db=SQLAlchemy('postgres://user:[email protected]/database')
)