it is not a focus of development and most applications should be written to use Tornado’s own interfaces (such as tornado.web) directly instead of using WSGI. In general, Tornado code is not thread-safe which do every- thing they are going to do before returning). There are many styles of asynchronous interfaces: • Callback argument • Return a placeholder (Future, Promise, Deferred) • Deliver to a queue get(self): http = tornado.httpclient.AsyncHTTPClient() response = await http.fetch("http://friendfeed-api.com/v2/feed/bret") json = tornado.escape.json_decode(response.body) (continues on next page) 26 Chapter

it is not a focus of development and most applications should be written to use Tornado’s own interfaces (such as tornado.web) directly instead of using WSGI. In general, Tornado code is not thread-safe which do everything they are going to do before returning). There are many styles of asynchronous interfaces: Callback argument Return a placeholder (Future, Promise, Deferred) Deliver to a queue Callback - api.com/v2/feed/bret") json = tornado.escape.json_decode(response.body) self.write("Fetched " + str(len(json["entries"])) + " entries " "from the FriendFeed API") For

which do everything they are going to do before returning). There are many styles of asynchronous interfaces: Callback argument Return a placeholder (Future, Promise, Deferred) Deliver to a queue Callback simply raise an exception (as opposed to the ad-hoc error handling common in callback-oriented interfaces), and Futures lend themselves well to use with coroutines. Coroutines will be discussed in depth else the user’s browser will simply hang. Here is an example that makes a call to the FriendFeed API using Tornado’s built-in AsyncHTTPClient: class MainHandler(tornado.web.RequestHandler): @tornado

it is not a focus of development and most applications should be written to use Tornado’s own interfaces (such as tornado.web) directly instead of using WSGI. In general, Tornado code is not thread-safe which do every- thing they are going to do before returning). There are many styles of asynchronous interfaces: • Callback argument • Return a placeholder (Future, Promise, Deferred) • Deliver to a queue fetch("http://friendfeed-api.com/v2/feed/bret") json = tornado.escape.json_decode(response.body) self.write("Fetched " + str(len(json["entries"])) + " entries " "from the FriendFeed API") For a more advanced

it is not a focus of development and most applications should be written to use Tornado’s own interfaces (such as tornado.web) directly instead of using WSGI. In general, Tornado code is not thread-safe which do every- thing they are going to do before returning). There are many styles of asynchronous interfaces: • Callback argument • Return a placeholder (Future, Promise, Deferred) • Deliver to a queue fetch("http://friendfeed-api.com/v2/feed/bret") json = tornado.escape.json_decode(response.body) self.write("Fetched " + str(len(json["entries"])) + " entries " "from the FriendFeed API") 26 Chapter 6. Documentation

it is not a focus of development and most applications should be written to use Tornado’s own interfaces (such as tornado.web) directly instead of using WSGI. In general, Tornado code is not thread-safe which do every- thing they are going to do before returning). There are many styles of asynchronous interfaces: • Callback argument • Return a placeholder (Future, Promise, Deferred) • Deliver to a queue fetch("http://friendfeed-api.com/v2/feed/bret") json = tornado.escape.json_decode(response.body) self.write("Fetched " + str(len(json["entries"])) + " entries " "from the FriendFeed API") 26 Chapter 6. Documentation

it is not a focus of development and most applications should be written to use Tornado’s own interfaces (such as tornado.web) directly instead of using WSGI. In general, Tornado code is not thread-safe which do every- thing they are going to do before returning). There are many styles of asynchronous interfaces: • Callback argument • Return a placeholder (Future, Promise, Deferred) • Deliver to a queue fetch("http://friendfeed-api.com/v2/feed/bret") json = tornado.escape.json_decode(response.body) self.write("Fetched " + str(len(json["entries"])) + " entries " "from the FriendFeed API") 26 Chapter 6. Documentation

it is not a focus of development and most applications should be written to use Tornado’s own interfaces (such as tornado.web) directly instead of using WSGI. In general, Tornado code is not thread-safe which do every- thing they are going to do before returning). There are many styles of asynchronous interfaces: • Callback argument • Return a placeholder (Future, Promise, Deferred) • Deliver to a queue fetch("http://friendfeed-api.com/v2/feed/bret") json = tornado.escape.json_decode(response.body) self.write("Fetched " + str(len(json["entries"])) + " entries " "from the FriendFeed API") 26 Chapter 6. DocumentationTornado

it is not a focus of development and most applications should be written to use Tornado’s own interfaces (such as tornado.web) directly instead of using WSGI. In general, Tornado code is not thread-safe which do every- thing they are going to do before returning). There are many styles of asynchronous interfaces: • Callback argument • Return a placeholder (Future, Promise, Deferred) • Deliver to a queue fetch("http://friendfeed-api.com/v2/feed/bret") json = tornado.escape.json_decode(response.body) self.write("Fetched " + str(len(json["entries"])) + " entries " "from the FriendFeed API") 26 Chapter 6. Documentation

it is not a focus of development and most applications should be written to use Tornado’s own interfaces (such as tornado.web) directly instead of using WSGI. In general, Tornado code is not thread-safe which do everything they are going to do before returning). There are many styles of asynchronous interfaces: Callback argument Return a placeholder (Future, Promise, Deferred) Deliver to a queue Callback - api.com/v2/feed/bret") json = tornado.escape.json_decode(response.body) self.write("Fetched " + str(len(json["entries"])) + " entries " "from the FriendFeed API") For